AudioCircle
Audio/Video Gear and Systems => Open Baffle Speakers => Topic started by: jonirvine on 16 Feb 2012, 06:24 am
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Hello all! I'm new to this forum but it looks like there's some good OB conversation! This will be my second OB project ever so bear with me if I'm way off. I'm looking for advice on this setup:
(http://jonirvine.com.s3.amazonaws.com/plan2.jpg)
Any thoughts? Ideas?
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Interesting setup :thumb: One thing to consider may be the Alpha 15 impedance, I believe they are 8 ohms, so with two of them you will be driving a 4 ohm load from the woofers amps (in mono mode) which they may not be very happy about (per specs). Or, connected in series you will have a 16 ohm load so reduced power.
The other point to note that the lowpass filter is 18 dB/octave. I'm not sure if that will integrate well or not.
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You know John I had similar concerns but when I emailed the Parts express guy he replied with:
Your best bet, if using two amps, would be to run one channel of each amp to each woofer. If you wanted to use one amp, you could run the two woofers in each speaker in parallel. This would present a 4 ohm impedance to each channel.
Regards,
Technical Advisor
Parts Express
So I didn't know I was misunderstanding something or if the amps would be able to handle sending (2) 4ohm loads to (2) 8ohm speakers (again, I'm a newb at this)
How would that 18 db/octave effect the sound? Do you have a better suggestion on how to amp this setup? Maybe some different amps or an easy crossover?
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I use a Denon AVR-1905 in stereo mode to drive four Alphas with a low pass 80 hz XO from PE on each. The Denon has terminals for 2 pair of mains. I paid $35 for this older non HDMI AV receiver which seems more powerful than the two Dayton APA 150's I use in another system. It's also nice to have a remote to control the volume.
Since the Denon has a DAC I am able to send a digital signal to it from my CDP while sending the analog to my integrated SET thereby avoiding the need for a preamp.
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If you go with the Daytons here's a manual that gives other connection options. The Dayton's were formerly sold by Emotiva.
http://emotiva.com/manuals/49_emotiva_bpa_manual_final_v1.0.pdf
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You'll definitely need a low pass filter for the alpha 15's - they have some nasty peaks. Assuming you can get the mids down to 200hz, a cheap way to do this would be with some small plate amps with a filter built in. GR has some designed for OB. Also, the stock zaph crossovers were not designed for such a wide baffle.
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The Alphas are near ideal for a passive system due to their very high Q.
However, for an active system, as proposed above, they are IMO, an inferior solution.
I would suggest instead 2 x http://www.parts-express.com/pe/showdetl.cfm?Partnumber=269-087 (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=269-087) per side and 2 x http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-805 (http://www.parts-express.com/pe/showdetl.cfm?Partnumber=300-805). Mount the amp in the main baffle or in the floor base to support it (if you are cloning the 909). You will get far cleaner, deeper, more powerful bass, with greater flexibility/control. And it costs less too.
More problematic is the dipole/baffle effect on the midbass. You will want some form of highpass on the midbass, as well as a bit of eq to tame the baffle peak. You should have that ability (eq) with your computer source. So the question would be the highpass on the midbass.
Btw, there also now zero excuse for not measuring. Any modern computer with a mic input can measure. The calibration mic that comes with HT receivers will work just fine and most everyone has those. So zero hardware to buy. And plenty free software.
Heck, there are even iPhone/android etc apps that allow RTA measurements, not perfect, but way better than flying blind over mountains. :wink:
cheers,
AJ
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The Alphas are ideal in my bi-amped Tang Bands/ H-frames. I drive the TB's with a 2a3 and the Alphas with two Dayton APA150's. MJK likes them :-)
(http://www.audiocircle.com/image.php?id=57739)
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Hi Look at your set up sub woofer will maximum down to only 150Hz(freq on the sub plateamp show) but for 5 inch on mid woofer I think is very difficult to reach 150 Hz(in open baffle without EQ) . normally 200 hz is lowest for that 5 inch .
thanks
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You know John I had similar concerns but when I emailed the Parts express guy he replied with:
So I didn't know I was misunderstanding something or if the amps would be able to handle sending (2) 4ohm loads to (2) 8ohm speakers (again, I'm a newb at this)
Hi, you would have less output power that way. The specs don't give power into 8 ohms, but probably 40-45W per driver. And you need more cables.
How would that 18 db/octave effect the sound? Do you have a better suggestion on how to amp this setup? Maybe some different amps or an easy crossover?
It would be a question of integration - slope (and accompanying phase) will affect how the woofer output interacts with the mid. I like using a DSP crossover and separate amps because of the flexibility. However the suggestions by AJinFLA look good.
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Thanks everyone for the advice! Very helpful and kind to offer your wisdom.
Well, since I've already ordered the Alpha's and the 1" MDF sheets have just come into the plywood store (special order amazingly enough), I've had to make some major decisions here. I've modified the plan to get rid of the Zaph's and instead go with my original plan (http://jonirvine.com.s3.amazonaws.com/plan_wires.jpg) and go with some TB W8-1808's (similar to your setup Poultrygeist but without the h-frame). I know, I know, this won't make for a very good 909 "clone" but in the end, I was worried that the untested Zaph's would lack in mid and also mix weird with the Alpha's since they had a much lower SPL.
I've also decided to passively cross over the alpha's with the seemingly simple design mentioned in MJK's legendary article http://www.quarter-wave.com/OBs/OB_Design.pdf (http://www.quarter-wave.com/OBs/OB_Design.pdf).
This will open up a variety of options for ampage which I will still meditate over while I build the baffles. I think I could still end up going with the Dayton's but I'd just nix using that active low-pass. I think the advice about the subs needing to reach 200hz is a good reason not to use any active pass on the amps.
I'm still considering the Peachtree Decco, Decco2, or Nova to power the full ranges and be my DAC. I like this all-in-one solution because it keeps things simple and clean. I may experiment with a high pass c/o on the full range like in MJK's article as well.
Here are some other amps I'm looking at for the subs:
Mitsubishi DA-A15DC - http://portland.craigslist.org/mlt/ele/2855425888.html
(2) Marantz MA-500 - http://portland.craigslist.org/mlt/ele/2851822075.html
Hafler DH-220 - http://portland.craigslist.org/mlt/ele/2859970931.html
*The problem with all of these is that they're all power amps with no volume control (like the Daytons). Poultrygeist, that's not a bad idea running the Alpha's with an integrated amp. I may consider that. Actually I have a Harman Kardon avr25II laying around that may do the trick but for some reason I feel weird about using these modern home theater amps for this sort of application.
Any other ideas on a good amp solution for the Alpha's?
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Any other ideas on a good amp solution for the Alpha's?
Pro amps usually have input attenuation (and plenty of power).
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The 2 flagship Jamos are on my list (but can probably never afford them!). That's way cool your doing a DIY version. My humble suggestion: add a rear firing tweeter. Best of luck however you decide :).
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My humble suggestion: add a rear firing tweeter.
I've seen this done before but I'm not sure I understand the concept, sonically speaking. Can you explain briefly and/or point me in the direction of an online resource?
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It's a pity that people still walk right into the Alpha15 trap. This unit is markedly inferior soundwise, for instance also to Beta15 and others which many people now have witnessed about, some exapmles: http://hi-fiworld.co.uk/index.php/loudspeakers/68-technology/138-open-baffle-loudspeaker-design-part-16.html .
I wonder what kind of music really is listened to if clarity and articulation is not the valued asset. The Alpha15 does colour the whole music appearance.
/Erling
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For the price of the NOVA or less you can buy a SET and an outboard DAC for your Macbook. I'm pretty sure you can even buy a USB SET. I promise you the full range Tang Bands will sound so much better with a SET and I would not use an evil passive XO on them as there's no need if you bi-amp and use the Daytons. Bi-amping with active XO will get the most out of this design. This is the approach MJK uses in his "Alpha Experimental OB Design" article which we're likely to see more of it in his "Designing An Active Two Way OB System Coming Soon" article.
The Alphas sound the same to me whether I'm driving them with the Daytons or the Denon AVR. I like the Alphas for their fast transients and over all bass weight which adds a much needed foundation to all the full range speakers I used them with. I run the Alpha H-frames topless when I want more bass for the Frugal Horn Mk3's.
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Erling,
with due respect for your controlled and measured personal findings and preferences: the second link in your previous post is a typical example for misleaded "knowledge", false "deduction" and poking around in the dark.
The thread opener has no clue about dipoles, can't do measurements, but knows that the driver is the culprit. When switching to another driver, things improve.
I don't see how anybody can learn anything trustworthy from such an "experiment". :(
Rudolf
It would be VERY helpful, if you could show with some distortion diagrams or CSD, where and why the Alpha 15 is inferior to the IB 15.
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If you daisy chain the Daytons together ( as shown in the Emo link ) each Dayton can drive two Alphas so there's no need to connect the Alphas in series and you'll have a 8 ohm load instead of 4 ohms.
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Rudolf,
You are right I removed the last link.
Regarding measurements I think there are better resources available, here is a measurement of the IB15's distortion at 100 dB from the known 'drivervault':
http://493531664873718246-a-1802744773732722657-s-sites.googlegroups.com/site/drivervault/driver-measurements/15/ae-speakers-ib15/non-linear-distortion/HD_sweep.PNG?attachauth=ANoY7cqUnxOLBHiHIcYsnGEDUEcHcIXHJt5ir7TEYNS4FrPxz_ASDiy5LCUMOt2rkDQSkN3j36yTD4IDq_vp58n7fJqyisEWDmzaQn4XFA9Wwit6HIHZ0lB9_yciwdarMMuOEjbzOhk6VMoDmDuM1rP4LRnVoW-I5_G-lHwIZB-_sMQIjvGtSIiqflAA4VELVqSV4TpWQYYHYkzPBE4tk6OCX9VsOpcSNuds_PhEqzm6skjLiEsqaj2oZTVwI8yOtdXQgJ1PIEwO96C1kwU_cENBhpAFcXqY_hCc2oUHNZjfG1fcOU70BoM%3D&attredirects=0 and I don't know of any similar for the Alpha15.
It is enough that I felt tricked myself when I realized the big difference in sound when the better unit was put to use.
/Erling
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If you daisy chain the Daytons together ( as shown in the Emo link ) each Dayton can drive two Alphas so there's no need to connect the Alphas in series and you'll have a 8 ohm load instead of 4 ohms.
The way Jon has it in his diagram is fine (the end result will be the same), he can use a female to male Y at the sub amp end and run one Alpha on each channel.
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I've seen this done before but I'm not sure I understand the concept, sonically speaking. Can you explain briefly and/or point me in the direction of an online resource?
A great online resource is the Linkwitz Labs website, just google those 2 words and off you go. He has tons of info. available, not just for his speakers but lots of links, references, articles, etc including measurements that back up his claims that omnipolar and dipolar using an open baffle framework are the best signal launch methods.
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*UPDATE*
Here's the pieces for the 1" MDF I will be CNCing this week:
(http://jonirvine.com.s3.amazonaws.com/OB_Pieces2-1.png)
(http://jonirvine.com.s3.amazonaws.com/OB_Pieces2-2.png)
(http://jonirvine.com.s3.amazonaws.com/OB_Pieces2-3.png)
(http://jonirvine.com.s3.amazonaws.com/OB_Pieces2-4.png)
Next Step: Lots of sanding and painting to get the piano black finish I'm looking for!
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And here's the 3D render:
(http://jonirvine.com.s3.amazonaws.com/cnc_r909.jpg)
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Perhaps this will rival user "Prelude"'s recent Linkwitz Orion DIY build! Just kidding guys, just saying this is looking pretty interesting.....best of luck on this project
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Great design to emulate Jon. Best of luck. :thumb:
The 909 has always looked to be quite the sexy beast for an open baffle speaker, as far as I'm concerned.
I'd love to hear a pair someday.
Thanks for the CNC images. Please post photographs of the build progress, if at all possible.
Bob
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Hello!
I have to agree with Scorpion here.
My humble advice is to stay away from High QTS drivers.
Although, I have to admit, I never used Eminence Alpha drivers, but I tried a cheap high qts driver in my open baffle with really bad results.
I would suggest to use a driver with QTS between 0,4 - 0,7, with a healthy Xmax instead. Use EQ to compensate for the roll off.
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To clarify my statement.
I think folks in general focus to much on the frequency response, and forget that the quality of sound production is a lot more than frequency response. Even though cheap high qts woofers will sound perfectly ok in open baffle, (compared how they do in a regular box), there's still more parameters to consider to get great bass than just low frequency response.
In open baffle, my experience, I prefer high quality bass, to let say, 40 hz with roll off compared to 25 with muddy, rumbling soft bass.
But that's me and my personal opinion. Other folks may like the "round" full bass sound, but I'm more for the "kick in the chest" type of guy. So it depends a lot what you kind of sound you are looking for.
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Fresh off the press:
(http://www.audiocircle.com/image.php?id=58448)
(http://www.audiocircle.com/image.php?id=58449)
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All pieces cut and ready to sand:
(http://www.tumblr.com/photo/1280/jonirvine/18224595243/1/tumblr_lzxg5lLTH71qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/18224595243/2/tumblr_lzxg5lLTH71qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/18224595243/3/tumblr_lzxg5lLTH71qz9wze)
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Very handsome and you should be very proud of your efforts.
I don't have the patience or smarts to get a good finish coat on MDF so I've started convering it with textured wall paper which makes it easily paintable.
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Thanks Paul! I'm planning on doing wood filler, oil based primer, then Sherwin's line of SureChem raven black. With lots of sanding in between coats, I hope I can get that piano black finish. On the back of the baffle and the base I'm going to cover with Quiet Kote sound dampening spray. I'm not sure of that will make much difference, but it can't hurt you know?
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Thanks Paul! I'm planning on doing wood filler, oil based primer, then Sherwin's line of SureChem raven black. With lots of sanding in between coats, I hope I can get that piano black finish. On the back of the baffle and the base I'm going to cover with Quiet Kote sound dampening spray. I'm not sure of that will make much difference, but it can't hurt you know?
No harm in using the Quiet Cote. It can only help. Baffles look excellent. Don't you just love CAD machines? When I made my prototype baffles out of a 3 layer sandwich of Plywood/MDF/plywood, they were still a little resonant feeling. Almost a little spongy if that make sense. Yes, it is layered, but the dimensions are large considering no sides or bracing as in a typical box build. Once I jumped into the bamboo, the added stiffness of that material really made a significant different in the rigidity of the baffle.
Keep the picts coming....
Greg
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Are you still set on the Alpha 15s? Did you check the link AJ sent you? Seems like a good choice without breaking the bank for some AEs. Never used the ones he linked, but Alphas are not the greatest and you are obviously investing a lot of effort and time, so.....
Greg
Sorry, just realized those woofers are 12" and you have you holes for 15" at this point.
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Once I jumped into the bamboo, the added stiffness of that material really made a significant different in the rigidity of the baffle
I looked into the pricing of bamboo actually.... very expensive! I would love to do a project with that one day. Maybe even make a nice component shelf even.
Are you still set on the Alpha 15s?
Well yeah... I went back and forth between some cheaper and more expensive drivers (including AJ's link). And yeah they're already ordered and waiting for me at my local speaker shop (Jamac in Portland, which I highly recommend btw). The Alpha's are well tested for OB context and 15's make it congruent for a r909 clone. Perhaps down the road a lil swap out if I'm not happy with the results but for now they seem like a trusted sub... and for someone like me who's a newb to this diy audio world... I'll take as much proven experience as possible. I've got a lot to learn!!
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I hope you will be satisfied with your 'Jamos'. Regarding Alpha15s and Beta15s there are evidence that the Betas sound more articulate and clearer than the high Qts Alphas as I posted above.
Alpha15 has Fs = 41 Hz and Qts = 1.26 and Beta15 has Fs = 35 and Qts = 0.58. Mostly (in OB) you have to cross from bass to midrange about 200-300 Hz were in fact you will cover a lot of instrumental and voice fundamental tones in the bassrange. I have used Alpha15, AE IB15 and A&D R1524. I cross at 277 Hz sharp between bass and midrange and to me the difference between AE IB15 and Alpha15 is like Night and Day, like you pull a veil from the speakers. I have no experience with the Beta15 but others say they are that better than the Alpha15.
But Alpha15 bass superiority is a bit of a myth. Simulation of the units on a 40 x 20 " baffle, two of them placed about the same as on your Jamo baffles looks like this:
Alphas first, crossed at 200 Hz 2nd order L-R:
(http://img440.imageshack.us/img440/7343/2alpha15200hzlrlp2nd.jpg)
Betas, crossed at 160 Hz, to give the same SPL level as the Alphas, 2nd order L-R:
(http://img15.imageshack.us/img15/3901/2beta15160hzlrlp2nd.jpg)
So what is the main difference. The Betas may be about 3 dB down compared to the Alpha at 40-50 Hz in all other frequencis they will be more or less equal.
This is the trade-off then, some dBs in the very low bass instead of overall clarity and articulation.
/Erling
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Thanks for these comparisons! I'll def consider the beta's more in the future. Luckily it seems like both are good candidates.
I wonder what the Tang Bands would look like on one of these simulations? I don't have a PC (Mac only home) so I can't download Edge or that other one that begins with a B. Can anyone recommend a similar program for the Mac? Or do me a solid and plug in the TB's values and post them? I'm running them wide open at first so I'm trying to determine my c/o point for the Alpha's. MJK does 200hz but his is a networked c/o with Fostex. Poultrygeist does 80hz and his setup is nearly the same as mine as he runs his TB's wide open too. Therefore I imagine there's a good reason to go lower than 200 hz... I just don't know how low. 80? 100?
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Why haven't you considered making your main baffle sand filled?
That mid layer in your sandwich could easily be replaced by a sand filled cavity.
That tall and narrow baffle is gonna vibrate quite bad.
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Why haven't you considered making your main baffle sand filled?
That mid layer in your sandwich could easily be replaced by a sand filled cavity.
That tall and narrow baffle is gonna vibrate quite bad.
I have no idea what sand filling is. Just using the best methods I know.
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I have no idea what sand filling is. Just using the best methods I know.
Hey Jon,
I've made a few sand filled baffles. It does help to cut down on resonance, vibrations, etc...
Check > Here < (http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=4203&sid=74e9315be6897334a47187defd904f8a) and > Here < (http://www.hawthorneaudio.com/forums/viewtopic.php?f=2&t=3018&sid=74e9315be6897334a47187defd904f8a)
Something to think about for your next build. Hope that helps. :wink:
Bob
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Wow Bob, those are nice builds! I've never heard about this method until now. Zmyrna, you're right, this would have been a fairly easy modification considering my design.
I know that the Jamo's are made of 7 layers of MDF so that's why I decided to go that route. I guess we'll see how these sound without sand and def consider them next time. (Wait, "next time"? This is the build that was supposed to bring me eternal audio contentment) ;)
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(Wait, "next time"? This is the build that was supposed to bring me eternal audio contentment) ;)
You're new to this hobby, aren't you? :rotflmao:
Thank you for the complement Jon. I'm watching your build with interest as I've always thought those 909's were pretty sexy. On top of that, you're doing a fantastic job.
Just a heads up though, it's easier to have a damp rag handy during clamp time to wipe up the glue as it squeezes out than it is trying to sand it off once it dries. Less change of damaging the MDF trying to sand off the glue and wood glue is harder than MDF.
Bob
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You're new to this hobby, aren't you?
Oh yes, very new in a lot of ways. I have a lot of experience with car, stage and video editing related audio but this is the first time getting in "deep" with it all, esp from a diy perspective.
Just a heads up though, it's easier to have a damp rag handy during clamp time
Actually, I used zero clamps. My friend who has the CNC also has what's called a vac bag. He threw it in there. It gives about 120lbs of pressure evenly throughout the whole thing... it's like those storage bags that you vacuum seal but 10x more powerful.
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Just for the record, I was teasing about the 'new' comment, based on your idea that any part of this hobby is "eternal"....there's always something shinier to draw our attention. :lol:
I'm familiar with the vacuum press. It's a fantastic system, but does make it hard to wipe the glue off before it dries.
Bob
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oh no worries Bob... I totally know what you mean.... I was joking too when I said "eternal" knowing that this hobby will probably never provide ultimate contentment. hahahaha.
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But Alpha15 bass superiority is a bit of a myth. Simulation of the units on a 40 x 20 " baffle, two of them placed about the same as on your Jamo baffles looks like this:
Alphas first, crossed at 200 Hz 2nd order L-R:
(http://img440.imageshack.us/img440/7343/2alpha15200hzlrlp2nd.jpg)
Betas, crossed at 160 Hz, to give the same SPL level as the Alphas, 2nd order L-R:
(http://img15.imageshack.us/img15/3901/2beta15160hzlrlp2nd.jpg)
So what is the main difference. The Betas may be about 3 dB down compared to the Alpha at 40-50 Hz in all other frequencis they will be more or less equal.
This is the trade-off then, some dBs in the very low bass instead of overall clarity and articulation.
Erling,
I know you don't like the Alpha 15A woofers, that is OK. But looking at the two plots you have produced, what in particular causes the Alpha in your opinon to be at a disadvantage in clarity and articulation compared to the Beta? High frequency roll off is almost the same. At these low frequencies I do not see cone break up being an issue. All I see is a bit more low end extension, I cannot believe that is the issue. The AE Dipole 15 and IB 15 both go even lower into the bass frequencies and that has not produced a similar observation. Your words and your plots seem to tell opposite stories.
Martin
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Hi Martin,
You are right the difference is not in the simulations, that was my point really. :)
I think we should agree that we disagree in this matter.
In reality I think loudspeakers, as other things also, perhaps not perform as ideal as theoretical assumptions proclaim.
/Erling
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Erling,
OK, the simulations tell one story.
Where do you think the problems you hear in the Alpha 15A come from and what is the key difference in the more expensive AE 15" OB woofers? There are now quite a few other OB and cost friendly woofers (high Qts and low fs) from Goldwood, GRS, and Eminence. Is one brand better than the others and if so what is the reason? I have both low cost and high cost OB woofers and have swapped them in and out of my system and with the exception of bass extension do not hear that large a difference at sane listening levels.
Martin
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MJK, (btw thank you for sharing your research with the world, it's been very helpful for me) if I'm planning on bi-amping the subs and the FR's separately, where do you think I should start with my lowpass c/o, assuming I'm running the TB's wide open? I have one friend who does 80hz and another who does 125hz. Is it really just taste/preference at that point? Or is there a way to quantify via a simulation or some other means beyond my abilities?
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Jon,
You do not want to run the full range driver without a crossover, you need to design a crossover for the woofers and the full range driver to ensure a smooth and controlled transition. Without the crossover you will have uncontrolled reinforcement and cancellation of the SPL responses from the different drivers.
I am not sure how you are designing your OB speaker system, I do have MathCad worksheets available that will handle your exact configuration with either passive or active crossovers. I am sure there are also other programs for doing the simulations required to engineer an OB system.
If you are using a trial and error approach that can also produce a decent design if you are patient, purchase a variety of parts to try in the crossover, and have an intuitive feel for how the crossover works.
Martin
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I do have MathCad worksheets available
Thanks Martin. Where can I find such worksheets? Are they for purchase?
Honestly, I'm pulling most of my design from other projects I've seen on the forums and a friend of mine who has a similar setup with Fostex/Alpha's. I'm more of a left-brained guy so I have a difficult time understanding the electrical engineering stuff. But I do know how to plugin values into a worksheet! The main thing I'm looking to find now is how the TangBands would look simulated on an open baffle. I don't have a PC so I can't use Edge or that other "B!" one. So if you have a worksheet that is mac-compatible, that'd be much appreciated!
thanks!
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Using a Mac pretty much leaves you out in the cold when it comes to speaker design hardware and software.
I probably do not have all the baffle dimensions exactly correct, but here are two recommendations for crossovers that you can use as starting points. These both assume the Alpha 15A drivers are wired in parallel.
1. Active Crossover
Low Pass 2nd order LR at 200 Hz
High Pass 2nd order LR at 300 Hz
No bass boost needed, woofer and full range driver wired in phase
2. Passive Crossover
Low Pass 2nd order
1.0 ohm resistor in series with a 4.7 mH inductor (ERSE Super Q) in series with the driver, a 135 uF Capacitor in parallel with the driver.
High Pass 2nd order
39 uF in series with the driver, a 7.2 mH inductor (ERSE Super Q) in parallel with the driver
Note the drivers are wired out of phase. The SPL of the woofer can be raised or lowered by changing the value of the 1.0 ohm series resistor. Do not use a tube amp, stick with a higher powered SS amp. Minimum electrical impedance is just under 5 ohms.
In both cases the system produces about 93.5 dB/W/m output.
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Wow, thanks Martin for all of your help
My only question is:
Note the drivers are wired out of phase.
I always thought it was "bad" to have speakers out of phase. What is the rationale behind this?
Also, I'm assuming you mean to wire them this way:
Figure A
(http://www.colomar.com/Shavano/2po-spkr.gif)
not this:
Figure B
(http://www.colomar.com/Shavano/2p-spkr.gif)
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The woofers are wired together in phase, but the Tangband is connected out of phase with the woofers in the passive crossover (not in the active crossover where everything is connected in phase).
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Martin,
I will try to give you an as correct answer as possible by revisiting the Alpha15s and compare with th IB15s. However I will be away for almost two weeks now, so it will take some time. But I will come back to your question.
/Erling
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Erling,
That would be great. I am curious to know your opinion concerning the differences you are hearing between the Alpha 15A and the IB15 woofers. Is there a design defect or limitation inherent in the Alpha 15A, maybe at higher power levels versus lower levels where I tend to listen, compared to the AE driver. The AE drivers are definitely better made units. No comparison in build quality of the two, it is not even close. Or is what you are hearing more related to the extended low frequency range of the IB15, more deeper bass providing a more satisfying result, which is what I hear. I am not too concerned about frequencies above 200 Hz, knowing the AE driver will excel compared to the Alpha 15A, since this frequency range is not being required in my style of OB speaker systems with low crossovers.
While the frequency range from 20 or 40 Hz up to 200 Hz seems like a limited narrow spectrum, compared to everything else up from 200 Hz to 20 kHz, it does contain a lot of the signal/information that makes music sound so good. To prove this to yourself all you need to do is listen only to the woofer in this type of OB system to realize that what you are hearing is most of the music but dulled slightly by the lack of the top end from the fullrange driver.
When you have time I am still interested in your observations,
Martin
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I believe that in such a comparison we need distortion and waterfall (CSD) measurements - done at different volume levels. Nobody will doubt that the AE driver can play a lot louder with less distortion. But maybe we can see, up to what levels the Alpha will play "safe" too. Pano's poll on http://www.diyaudio.com/forums/multi-way/204857-test-how-much-voltage-power-do-your-speakers-need.html (http://www.diyaudio.com/forums/multi-way/204857-test-how-much-voltage-power-do-your-speakers-need.html) does suggest that listening levels might be quite different from one individuum to the other.
Lately I covered the stamped steel basket of a midrange driver with anti drumming compound. The before/after difference was only vaguely visible in the response and THD diagrams, but had a huge impact (much reduced ringing time at 1 kHz) in the CSD.
Possibly such effects make the real difference between both divers.
Rudolf
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Rudolf, have you compared the sound quality difference on the midrange driver.
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MJK,
I drive my Tang Band W8-1808 with a 2a3 amp sans crossovers atop your H-frame Alpha design. The Alphas are driven by two Dayton APA-150 which have built in crossovers set at 80hz. This system totally humbled the expensive Zu's I could no longer justify and finally sold. How could a passive crossover benefit this system?
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Poultrygeist,
In the past month or so another DIYer has been e-mailing me recommending I try the no crossover approach to my H-frame and OB speaker systems. His arguement was interesting enough to convince me to give it a try. My dBX active crossover allows me to run without the crossover so I have basically two amps powering the two drivers in parallel. I have run the simulations and spent some time listening and comparing this configuration to my baseline set-up.
The simulations made it look like a total mess with either a broad peak (no crossover) or a deep null (one sided crossover) in the regions where the drivers overlapped. The sound was not as bad as the simulaton showed, but it was not as good as with the baseline crossover. The crossover on both drivers helps smooth the transition and to my ears produces a more balanced sound without the emphasis (peak) or de emphasis (null) on a narrow band for frequencies around 200 Hz. With the correct crossover on both drivers the sound from the speakers was just cleaner.
Martin
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So here's where things are at with my project. I'm still sanding away and routing the baffles but all the components are in (FR's Alphas, caps, inductors, etc). I've also come across some good deals on craigslist so now I have a Msuci angel Tube amp and even traded my old Wharfedale's for a 300watt poweramp. I've spent more money that expected on building materials so I've had to adjust my initial plan a bit. Thank you for everyone that has helped my fine tune this project (esp Poultrygeist who has entertained my many emails.)
So here's my dilema. This system is going in my humble home theater in my basement. Instead of having 2 systems in there, I was hoping to combine the 2 into one somehow while being able to switch between 2 channel and some sort of Dolby SS. The only way I can figure out how to do this is to have a preamp/integrated amp that can switch between the sources and also process the dolby when needed. I have a Harman Kardon AVR25II but I'd rather replace that with something more audiophile worthy that won't disrupt the nice audio signal i have coming from my dac. Any ideas on this? See below:
(http://jonirvine.com.s3.amazonaws.com/plan3.jpg)
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Pre-pro?
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Meaning a professional preamp? I've looked at some Emotiva's and Rotels but those are out of my price range at this point. Any recommendations on affordable models?
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*PROJECT UPDATE*
> All components are in
> One day of sanding the baffles down
> Next: puddy edges and resand. also, router & and chamfer the rear holes.
Pics:
(http://www.tumblr.com/photo/1280/jonirvine/18701736448/1/tumblr_m0cacs3oc91qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/18701736448/3/tumblr_m0cacs3oc91qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/18701736448/4/tumblr_m0cacs3oc91qz9wze)
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Very Cool :D Thanks for the pictures.
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I've seen older Marantz AV preamp processors for under $100 on ebay.
Keep those pictures coming.
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So I sold some old guitar equipment and scrounged up just under $400 to buy this missing component. Based on searching around on the net and CL I found 2 possible solutions:
1.) ROTEL RSX-1058 ($400 used) - this is a used unit but originally a much more expensive unit. It's more powerful but lacks the latest Dolby codecs for when I'm in HT mode. It also uses 1.1 HDMI standards which may cause issues down the road. However it'a high quality amp for a good price. I'd also consider using it to power my Alpha's and removing my power amp from the equation.
2.) Marantz NR-1402 ($390 new) - This is a less powerful amp but it has the lastest codecs. It's received good reviews across the board. Again, since I'll really only be powering the center/surrounds speakers with it when I'm in 5.1 mode, it doesn't have to have much power. I also like that it comes with a calibration mic and built in software. My biggest issue is choosing this one over the Rotel which has an even better reputation and may be able to power my alphas thereby cleaning up the system clutter a bit.
It's a dilema but I'm leaning towards the Marantz because Dolby TrueHD and HDMI 1.3 seem like significant upgrades that will be highly noticeable in a HT context. I would love to remove my power amp from the equation though so the Rotel also is appealing. oh the decisions!
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HT is for movies and their sound effects.
Two channel is for music.
It would be a waste to drive the TB's with an AV receiver.
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OOh no :nono:, I'm still going to power the TB's with my Music Angel Tube amp. I just need something to act as a preamp so I can switch between 2.0 for Music and 5.1 for theater. So basically I'd run my sources into the integrated amp and use the pre-amp out (using a y-adapter) to the Music Angel and Alesis power amp. Then, when I want to listen to music, I just turn off the Dolby and go into 2 channel bypass. Basically, I'm trying to prevent having 2 systems in one room. I'd say I use the room 50/50 for music/movies. I think the open baffles may be odd for HT but I'm going to see how they work. I have some EV OB's in my office and they actually sound pretty good for HT, the sounds are very atmospheric. Usually in HT the center channel is doing most of the work anyhow, so I don't think the TB's will get much exercise while in 5.1 mode. See below:
(http://jonirvine.com.s3.amazonaws.com/plan3.jpg)
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HT is for movies and their sound effects.
Two channel is for music.
It would be a waste to drive the TB's with an AV receiver.
Oh Jesus..... :duh:
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Music in the round is fine if you play in the orchestra :lol:
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Right. I think you should just stay where you're at. You seem happy there so there's no reason to change, and certainly not on my account. You will not receive a multi-channel music sales pitch from me.
Jon - What you're proposing will work just fine. I do it in my system for home theater AND two channel, using a tube amp from the pre-outs to power both "modes". The "surround off" button can be pressed on any AVR to feed the main channel only.
I have no knowledge of the specific AVR units you mentioned though.
Bob
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If I may suggest something it would really be to investigate how the 8 channel MiniDSP could be used in your setup. I think the DAC section of that unit is most acceptable and then Crossover and EQ facilities will be far superior to anything you thought of so far. Regarding the center channel I dont really know their frequency range but possibly you could run them from the TB fullrange amp or an amp of their own, a cheap T-amp would probably do. I would venture to suggest Vifa TC9FD-18-08 units for this channel, very good value.
/Erling
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On the subject of the MiniDSP, I know a fella that has a 2x8 unit he's willing to get rid of (and no, it's not me).
Bob
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Interesting Scorpion... so does a mini DSP negate the need for a passive crossover?
Unfortunately, it doesn't really help me with my need for a preamp as far as I can tell. :(
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http://www.minidsp.com/
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Is this enough chamfer/roundover for the 8" FR? I wanted to go about twice this radius or more but I don't have a router with a large enough shaft to fit a larger bit (ugh). I also did the 15" woofer holes just "because". Will this help the sound at all?
(http://www.tumblr.com/photo/1280/jonirvine/19333771277/1/tumblr_m0wvmhC4l71qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19333771277/2/tumblr_m0wvmhC4l71qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19333771277/3/tumblr_m0wvmhC4l71qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19333771277/4/tumblr_m0wvmhC4l71qz9wze)
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Wow!
You got some wood working skills there Jon :thumb:
The roundover looks good enough. The woofers doesn't really need roundover but it won't hurt either and it looks better.
/Jacozz
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Thanks Jacozz!
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You may want to consider flow coating the baffles and then sanding smooth, priming and finish coat. The flow coat will give a very hard and durable finish like on a glass fibre boat.
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.....otherwise the MDF seams will show later down the road.
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miniDSP will also negate the need for the DAC.
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So i'm not familiar with flow coating... i did some googling but only found some videos of guys spraying huge amounts of paint with a hose, usually on industrial equipment. Is this flow coating? If so, I don't have equipment for this. Is there an "home-brewed" way to do it? What is the actual substance that coats it?
My plan was to do a 50/50 water-glue mixture on the seams and then sand again. Think this will work just as well?
Any advice is appreciated!
Thanks!
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Jon, you need to use a 2 pack polyester type of undercoat. Probably available from guys that supply auto refiinishers. Or you could go to your local auto' painter and maybe purchase a small amount from them. 2 pack will probably give you the best finish without any seams showing later on.
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*UPDATE*
Ok here's some pics for ya from today's work. Basically I got everything ready to audition before I go through the painful process of painting. One thing that I had to do was alter the design so the baffle is on the base instead of the pedestal on the base. Basically, the "lip" on the pedestal was too narrow and going any deeper would mean recutting the arm and the base completely. It was hard for me to compromise on this but I figure it's a purely aesthetic decision that saved a lot of heartache. How do they sound? Well... fantastic!!! They're much brighter and more crisp than my EV LT-12 OB's which have a bit of a "horn" sound and lacking in mids. These TB's (although not "burned in" yet) are absolutely wonderful and smooth. The sound stage is really present.
Next steps:
1.) Take a break and enjoy them for a couple weeks.
2.) Seal the edges. I'm still leaning towards glue/water mix but I'm open to other methods that are relatively easy and practical.
3.) Sand around the inset of the subs (they're "just right" for now but with a few layers of paint and primer, I may be rubbing the edges of the Alpha's which may cause what I believe is called resonance.
4.) Prime, prime, prime.
5.) Sand
6.) Paint with paint gun. Wet sand in between coats.
7.) Polish
8.) Spray base and rear of baffle with Quiet Kote.
9.) Paint the arm silver.
10.) Put it all back together
Did I mention I'm also building open baffle Center and surrounds for when I'm in Home Theater mode? I'm doing the CEnter with a Dayton PS220 and the rears with Dayton PS180's. They will match the mains with piano back and curved edges. Ever see totally open baffle 5.1 setup? Well, you're about to!
Ok some pics:
(http://www.tumblr.com/photo/1280/jonirvine/19867018004/1/tumblr_m1f2opqFU21qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867018004/2/tumblr_m1f2opqFU21qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867018004/3/tumblr_m1f2opqFU21qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867018004/4/tumblr_m1f2opqFU21qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867068822/1/tumblr_m1f2qbklCK1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867068822/2/tumblr_m1f2qbklCK1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867068822/3/tumblr_m1f2qbklCK1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867068822/4/tumblr_m1f2qbklCK1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867132155/2/tumblr_m1f2saXkwu1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867132155/3/tumblr_m1f2saXkwu1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/19867132155/4/tumblr_m1f2saXkwu1qz9wze)
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Wow dude. That's awesome. :thumb:
Although putting partially finished speakers "in play" with the intention of finishing them "later" can be a dangerous thing. :wink:
Bob
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Thanks bob! Yeah, I hear that... I'll welcome a virtual kick in the pants if you don't see an update within the month :icon_lol:
That being said, I really can't stand the look of MDF and am longing for that piano black finish I have in my head, so hopefully that will keep me motivated.
Till then!
(http://s3.amazonaws.com/data.tumblr.com/tumblr_m1h76c2icx1qz9wzeo1_1280.jpg?AWSAccessKeyId=AKIAJ6IHWSU3BX3X7X3Q&Expires=1332824456&Signature=YVbOn%2BCc%2FPAVsxLdU66IxyhNV4Q%3D)
J
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Jon,
I think the miniDSP (or some other line-level crossover) would be a preferable solution for your project. You already have multiple amps so it doesn't make any sense to implement a speaker-level crossover. Plus, you will most likely need some equalization for both the full-range and woofer drivers. The miniDSP can make easy work of that.
Cheers,
Dave.
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You're right Dave, and many have recommended this for me too. I will def consider going the miniDSP route in the future. For now, my wife approved budget is completely tapped out as I built this system from the ground up. Going miniDSP also means I need to buy/acquire Parallels & a windows license since I'm completely Mac here at home. But I agree, it would def help me get a better sound for my setup. For now the $30 on my passive c/o will have to do and I'm pleased with the sound. I went with MJK's advice on the c/o points and while I would like to play around in the future, it's a well rounded sound for me now.
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my friend use miniDSP with MC note book with out problems
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Yes, no need for Windows for miniDSP.
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oh really? Cool! I'll have to check that out then, I was under the wrong impression.
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Beautiful work!!
I recently installed a pair of TB 1808's in an ob baffle with a 15" Auggie. The TB is amazing so far, but do yourself a huge favor (if you haven't already). Run a driver break-in cd, like from Isotek or Purity Audio.
Out of the box the TB was congested & peaky. After only 6 hrs of play at a medium volume, the Isotek cd corrected most of the nasties.
My set-up is similar to yours in that we have a large screen between the speakers. The TB's complement the arrangement with wide & detailed imaging.
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Running a burn-in right now actually! Some pink noise and spirit classical station at once. I've never tried one of those CD's before... Worth the purchase? Got any pics of your system goober?
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Here's some progress on the center channel and surrounds. They sound pretty darn good! I added a monopole subwoofer to the center to fill in the lows but the vocals are really crisp with this Dayton 220 and spread nicely across the screen to give a realistic effect... def an improvement from any boxed center channel I've used. While these pieces were primarily made to work with my home theater, it's also fun hear music in Dolby or DTS music mode, but I prefer it in pure stereo still. So now that everything is sounding good, next step is to dismantle the drivers and start priming/painting. I'm using Sherwin Williams' "Sher-Kem in Raven Black." It's a high quality lacquer paint that is durable and supposedly very high gloss. I've read that it's the same paint used for tractors and heavy duty equipment. I'll test it on some spare MDF and decide afterwards if I need to wet-sand and/or polish. The manager at sherwin williams seems to think I will be happy with a nice even coat without it but I'm not sure it will meet my standards for a "piano- black" finish. More pics to come!
(http://www.tumblr.com/photo/1280/jonirvine/20617466045/1/tumblr_m22zq2Jh6S1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/20617466045/2/tumblr_m22zq2Jh6S1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/20617466045/3/tumblr_m22zq2Jh6S1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/20617466045/4/tumblr_m22zq2Jh6S1qz9wze)
(http://www.tumblr.com/photo/1280/jonirvine/20617466045/7/tumblr_m22zq2Jh6S1qz9wze)
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I like your style Jon. looking great. :thumb:
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Very nice work John.
Dave
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2.) Seal the edges. I'm still leaning towards glue/water mix but I'm open to other methods that are relatively easy and practical.
Have you had any more thoughts on your #2?
I've had several MDF builds where the seams showed through after the paint dried. And that was after using various methods of sealing the edges, including fiberglass resin on one build and a thick coat of wood glue on another.
Within a couple days, both had "cracks" in the paint where the layers of MDF were.
Bob
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I've used automotive glazing putty with success....on subs no less.
Like bondo but no mixing and not quite as hard to sand.
On round edges a thick piece of rubber to guide the putty, and not much to sand.
Sealed the cut edges quite nicely and hasnt cracked in the last 4 yrs of use.
Used the same method on my V-1s for the round top of the OB....same result
Beautiful work BTW.....very impressive!
Might want to give it a try.... :thumb:
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I actually was still planning on the glue/water mix because bondo is too much work and I've worked with resin before and it's more mess than I'm willing to work with. That being said, I've never thought of using glazing puddy before as PDR suggested. Maybe it's a happy medium? I'm also planning a heavy heavy coat of primer and have purchased a very high quality paint. Hmmmm.... I'm still undecided but I'll be starting soon. Thanks for sharing your experiences... Any other options?
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I've never tried the Glazing puddy, so I have no opinion there.
But I would strongly caution against the glue idea. I've done that, with very poor results.
And I did several coats of primer and paint as well....to no avail.
Anything that consists of two parts and has to be mixed is going to be a pain, so I'd steer clear of that, just because you've got so many linear feet to cover. But some form of puddy like PDR is talking about would be great.
Bob
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I always used wood putty with great success, easy to sand too.
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A couple suggestions ... think about putting a "quirk" @ the seams of the MDF panels. (where they sandwich). This can be done now with a router and a shaft that will accept slot cutters. This joint will show no matter what later on ... work with it. A nice 1/8" x 1/8" groove is easy to produce .. and a guy could accent that with a contrasting color, silicone caulk, wood/laminate inlay .... you get the idea.
As you guys fabricate your parts don't get into a rush to assemble. Take the time to sand all of your work beforehand. Doing it later is a real PITA.
It would be an extremely good idea to at least primer your parts as well at this stage. Raw MDF is like a sponge. Get it sealed up right away. Doesn't matter too much with what ... just get something on it.
Looking good so far!
Phil
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think about putting a "quirk" @ the seams of the MDF panels. (where they sandwich). This can be done now with a router and a shaft that will accept slot cutters.
Exactly!
If you can't hide it, accentuate it! :thumb:
Sometimes it's easier, and adds a nice visual touch too.
Bob
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I was thinking about wood puddy and even bought a big can to do so a month ago... maybe I'll try that after a layer of the glue/water mix. Then go crazy on Primer. That should do it, and geeze if it doesn't this is the last time I'm working with MDF. Speaking of which, I'm already starting a new project using bamboo plywood... very excited to use this material and not deal with all the sanding and finishing of MDF (ugh).
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............. this is the last time I'm working with MDF..(ugh).........
That's a good choice. :wink:
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So today's weekend project was adding a rear firing super tweeter. The "baffle" for it is temporary but i found a good use of some spare IKEA metal braces laying around. Overall, I "think" I like the addition to the rest of the system but am still questioning whether I "like" the crisper highs I'm hearing. When I A/B them (on/off) I can def tell my TB's alone aren't producing the same amount of brightness however, I might say there's a more balanced and even warm tone without the tweeters. hmmmm.. SO the jury is still out.
Does anybody have any advice on where to face the tweeters? I currently have them parallel with the rear wall and have designed the framing so I can play with different directions. Any advice?
Here's some pics:
(http://28.media.tumblr.com/tumblr_m2uxurXD5b1qz9wzeo1_1280.jpg)
(http://25.media.tumblr.com/tumblr_m2uxurXD5b1qz9wzeo2_1280.jpg)
(http://27.media.tumblr.com/tumblr_m2uxurXD5b1qz9wzeo3_1280.jpg)
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Most creative Jon ....Go boy go !!!!!!!.
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If I had to guess, that tweeter is quite a bit more sensitive than the other drivers. You might try padding it down some to find a happy balance of more highs without sounding too bright...
You could pick up some L-pads from Rat Shack and then have a variable set-up. Much better than attaching various resistors a million times till you find the sweet spot.
Also, how are you crossing it over? Are you picking off a parallel feed from the TB and using a cap?
Greg
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Yeah you're right... it is more sensitive with an SPL: 104 dB 1W/1m. I have it running on it's own amp right now so it's not networked with the FR or anything. I've never used those L-Pads but will def look into it. I like the idea of being able to play with different options. Of course, I'm thinking of going with a MiniDSP real soon here so I might hold out and just adjust it from there. For now, I think simply toning down the volume/level on the amp has helped it not be so bright.
The capacitor included is 3.3uF, which will put the crossover frequency at approximately 6kHz.
I still don't know what direction sounds best as I don't have an "assistant" available to turn it as I listen... i have to keep getting up and down trying to remember what each version sounds like.
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Try some smaller caps without an L-PAD. I am running a Fostex 90A super tweeter with a 0.33 uf cap. Buy some cheap caps of say 1.0, .68, and .33 and see where it gets you. I run mine facing the front. I tried rear facing and didn't like it.
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Try some smaller caps without an L-PAD. I am running a Fostex 90A super tweeter with a 0.33 uf cap. Buy some cheap caps of say 1.0, .68, and .33 and see where it gets you. I run mine facing the front. I tried rear facing and didn't like it.
I don't get the point behind your recommendation. Caps of those values will put the knee of the crossover at approx. 20,000 , 30,000 and 60,000hz respectively. Sure, sound will still be getting through with only a 6dB/oct slope, BUT why do this rather than a proper crossover where you might want it and then some padding to lower the level. I'm not suggesting to leave the variable L-pad in place, just use it to tune to taste and then swap it out for the value resistors that work best for the situation.
Jon, you might to swap out that nasty little cap that came with the tweeter and replace it with a nice Dayton poly or something....nothing too boutique. It's at least a cheap tweek. Might make a difference, might not, but you're only out a couple of bucks to try it.
Greg
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Yeah you're right... it is more sensitive with an SPL: 104 dB 1W/1m. I have it running on it's own amp right now so it's not networked with the FR or anything. I've never used those L-Pads but will def look into it. I like the idea of being able to play with different options. Of course, I'm thinking of going with a MiniDSP real soon here so I might hold out and just adjust it from there. For now, I think simply toning down the volume/level on the amp has helped it not be so bright.
The capacitor included is 3.3uF, which will put the crossover frequency at approximately 6kHz.
I still don't know what direction sounds best as I don't have an "assistant" available to turn it as I listen... i have to keep getting up and down trying to remember what each version sounds like.
Yikes, 104?!?!? Holy highs Batman! You gotta tame that sucker. IF you use the L-pad, you could attach long wires to it and play with it from your seat in real time. You might even find a stereo one and set both speakers simultaneously.
I would keep them pointed about straight back. This should give the you the most even, consistent spread once you have the overall level lowered. Pointing off to the side too much might give you some reflected hot spots side to side along your listening axis. You might even play with a little diffusion on the wall behind them for a more natural reflective spread.
Greg
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Why? It works and it is what Fostex recommends, not that means anything and it is cheap and easy to do.
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Why? It works and it is what Fostex recommends, not that means anything and it is cheap and easy to do.
Actually, the data sheet shows 1.0-1.5Mfd cap AND an L-pad. Just sayin...
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hmmm... great advice here! Thanks for the input! I def think this "nasty" crossover is the issue. Now I just need to decide if I should mess with the passive solutions mentioned or just wait till I get a miniDSP in a month or so. It's about time for me to disassemble and start painting so I might just wait for the miniDSP.
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Oh this is funny... Jamo mentioned me on Twitter:
(http://www.audiocircle.com/image.php?id=61611)
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That is funny :D
Jon, have you heard the original Jamos?
From my understanding, they did a clever thing with the XO:s for the woofers.Instead of using high QTS drivers, they choosed to lowpass the first woofer around 60-70 hz (or somewhere around there), but with the second driver lowpassed around 250 hz (or somewhere around there), so it's actually a 3 1/2 way speaker.
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I have but was not completely blown away by the sound as much as I was the design. I knew going into this I didn't have the skills to put together a crossover system anywhere close to theirs so I went with the tried and true design of MJK.
they choosed to lowpass the first woofer around 60-70 hz (or somewhere around there), but with the second driver lowpassed around 250 hz
That's interesting, I did not know that. I'm planning on getting a miniDSP soon and maybe I'll play around with something like that instead of running the Alpha's parallel.
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Does anybody have any advice on where to face the tweeters? I currently have them parallel with the rear wall and have designed the framing so I can play with different directions. Any advice?
convention seems to be that the rear tweeters should be square with the speaker to keep the dipole radiation pattern. However, there are a few examples of upward firing tweeters.
Seems like it might be a trial and error style integration based on your system and your listening room set up. I am actually going down this road soon with a rear firing tweeter to match my sealed front tweeter.
Maybe you should ask your new friends at Jamo and see what they say...
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Maybe you should ask your new friends at Jamo and see what they say...
:lol: That's funny.
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The rear tweeters on my baffle are firing inwardly with satisfying results.
(http://www.abload.de/thumb/107rckseitegrodesktopkli8u.jpg) (http://www.abload.de/image.php?img=107rckseitegrodesktopkli8u.jpg)
(http://www.abload.de/thumb/108rckseitenahansichtc2edc.jpg) (http://www.abload.de/image.php?img=108rckseitenahansichtc2edc.jpg)
If you install them flexible, you can test what you like best.
Regards
Till
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Jons bullet tweeter doesn't illuminate the hemisphere behind the baffle, but throws a "hot" spot on some part of the wall. I'm not sure if a directive speaker is the best approach in this case.
Rudolf
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My hat's off to anyone with the patience and skill to prime, sand and paint MDF.
On my next MDF OB's I'm going to try covering them with heavy pre-pasted wall paper and use molding on the edges.
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Hello John. I was wondering if you have finished the speakers and how do they sound?
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My hat's off to anyone with the patience and skill to prime, sand and paint MDF.
On my next MDF OB's I'm going to try covering them with heavy pre-pasted wall paper and use molding on the edges.
I agree with poultry, the last time I put together a MDF cabinet it took forever to sand prime and paint correctly. MDF just soaked up so much primer and when I finally went to paint it the first time some flaws were seen I didn't catch after sanding it multiple times. So back to more priming and sanding then painting. Well in the end I was fairly satisfied. Nope, throw veneer, sanded, stained, poly'd and more than happy.
ps: that mdf dust during sanding is a breathing killer, mask a must. Aw mdf, such an odd material. Pre drill holes or it will crack, heavy and dense but weak and easy to chip.
Also I would like to state these clones look awesome. I always loved those Jamo's thinking that I would create a clone later when I first saw the design as well. A job well done and patience has sure made this go along way. Well done.
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I too wish for an update from Jon on this interesting build. Since I discovered the ease of active crossovers my OB's has taken on a new life.
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Thanks for the bump guys, I forget all about the build.
I was soooo looking forward to seeing the end results.
I've seen some fells do a brush on "sealer" for the MDF so it'll take paint.
Bob
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I've seen some fells do a brush on "sealer" for the MDF so it'll take paint.
works great. saves time.
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Hey guys! So as many had predicted, it's much harder to go back an "finish" once I had it all assembled. This is due in part to my summer hobby of motorcycling kicking in and the fact that my air compressor busted right around the same time. So I'll be picking up where I left off soon as the Portland rainy season is approaching. I have all of the finishing materials (primer, paint, etc) sitting in my garage waiting for me.
I'd be interested to hear more about which MDF sealer people have had success with. But for now, I've decided to do the following:
- Seal the edges with a glue/water mix
- Seal the edges again with wood puddy and sand.
- Roll a few coats of primer and sand
- Buy a new air compressor on Craigslist and paint/wetsand x 4 or so coats
- Polish if necessary
As far as sound is concerned, I'm super satisfied with the results but i think once I get through the finishing process, I'm going to replace the passive C/O's with active C/O amps on the subs and run the TangBand's wide open with my current tube amp. If that doesn't quite do the job, I may add a miniDSP into the mix and tune each speaker on the front end.
All summer I've enjoyed them immensely and my friends who have experienced them have also been equally amazed at the clarity and realistic soundstage. If anyone lives in the area, I invite you to come take a listen and let me know what you think!
Jon
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I've never (successfully) seal MDF edges myself, but have been witness to the process with buddies.
It's a simple layer/coating of chemical brushed on, then sanded, then painted. After that, it's treated like any other material being painted and sanded. Just don't sand back down deep enough to hit fresh MDF.
Or....Wrap the baffle in speaker fabric, screw the drivers in over the top of the fabric, and call it a day. :lol:
Bob
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I'd be interested to hear more about which MDF sealer people have had success with. But for now, I've decided to do the following:
I skipped the water/glue and used a fine drywall filler rubbed into all the seams -- sanded with 220. Wood filler was a little too gritty and not fine enough for the small seams. The best advice I got was to avoid any soft sanding blocks. I used a 6"x12" piece of mdf and a full sheet of sand paper to really smooth everything out.
Then I primed and sealed everything with this rolled on:
http://www.homedepot.com/buy/paint/primers/zinsser-bulls-eye-1-2-3-1-gal-water-based-white-primer-sealer-182407.html#.UIcK3LSxFGE
Again, sand with a large flat sanding block.
Depending on your seams, you may need to repeat the procedure. And remember to let everything dry overnight before sanding anything !
The results I got were fantastic. You can see my current build here:
http://www.audiocircle.com/index.php?topic=109455.0
I'm in the same boat with the weather in Vancouver - next sunny day I'm taking off to do the final spray.
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Did you ever finish the project? painted, etc? Finish PICTURES? Just wondering what other inexpensive drivers would go with a project like this besides the alphas.
Thinking about doing a similar project and noticed a couple drivers that might fit the bill. MCMelectronics have a couple new models out. The one I was looking at was 55-2993 with a fs 44hz, qts .53 xmax 6.5mm spl 98 100oz magnet, 4.0" voice coil die cast frame.
Those baffles look really good. You CNC'd them? Did you have this at hand, or did you get it done somewhere else? Where can I get wood cut like that, and how much does it cost?
What inexpensive fullrange driver could be used for the top half besides the TB?