hooked on ob sound... what to build first?

rabbit · « **Reply #20 on:** 10 Mar 2015, 12:19 pm »

Quote from: mcgsxr on 10 Mar 2015, 11:55 am

I maintain that you don't need to go multi-way or spend a ton of money to play around with this and potentially even be happy.

You can, and if you want to you should.

Linkwitz has done a ton of research, and shared that too, no doubt.

Others here have spent tons of time finding out how this works, and why, and thankfully also share their experiences.

Sure there is science to it, but I don't personally think that you have to dive in headfirst to a driver bakeoff with measurements, and multiway amplification to "hear it".

If the complex solution is satisfying for you, awesome. if now, don't be put off. If this is a hobby for you, it is fine to start simple and play around.

I ended up with a full ranger on a wide winged baffle, augmented with biamped OB bass. It was excellent. It was 100% shared ideas in the "Gravity well of a darkstar" thread that formed my opinions about what is possible and pleasing on a budget.

I respect that there are tons of ways to find satisfaction in audio, and OB is DIY paradise.

sure, it you want something simple to try out i say happy listening

fwiw, i recently built a pair of lxmini, they are not dipole in any way because of the high 700hz xo, but they do sound sort of OB, because of their baffleless approch.
the fullrange driver does show itself from time to time, but i can highly recommend them.. great midrange imaging. farr superior to the hawthorne silver iris for example. (even thou they are more OB from midrange down)
otherwise the gainphile s20-z should work pretty good, easy to build and with an passive/active combo. top drivers and passive xo should be availible from madisound.

im guessing the OP is more interested in a high effciency solution with 15" woofers etc. i dont really have a specific recommendation in that department..so i leave it to you guys

Guy 13 · « **Reply #21 on:** 10 Mar 2015, 12:21 pm »

Hi all, translated directly from French:
Each one preach for his parish.
meaning that each one think is approach is the best and even the only good one.
Each approach has it's strong and weak points.
H, U and V frames, active - passive crossover, extended range, 2 ways and three ways.
What's the best? To me it's the simplest approach.
(Audio should be simple, as per my Avatar)

Guy 13

brad944911 · « **Reply #22 on:** 10 Mar 2015, 03:36 pm »

Wendell,
Here's what I've found since I was bitten...your happiness will be in relation to how much free time you have, your access to test equipment, your source equipment, your tools and ultimately how your expectations for YOUR sound are met. I can see OB not being for everyone, especially those who expect PERFECTION right off the bat. I found out that using open baffles is challenging and an absolute blast all at the same time. I was able to design a system that has met my ear for far less than my old Maggies.
I built the original Hestia in Nov of this year and have already modified every aspect of it. Not that it didn't sound good, but every ear and room is different...and I like to tinker...ALOT. What I did come to terms with is that for me, DSP is a savior! All my amps have DSP on board. This worked for me because I already used them, but for some with great amps already, the MiniDSP would be invaluable. You can modify your sound without having a graveyard of components after every change.
If you're curious, I ended up with (per side) a JBL GT series 12 in a U frame enclosure, 2 MCM 10's with dust caps removed and a Vifa tweet coax mounted in each. I saw earlier a guy knocking coax and DSP, but for me it's working. Best of luck on your journey.

Brad

wendelltate · « **Reply #23 on:** 10 Mar 2015, 03:47 pm »

Thanks Brad (and everyone),

I read through the Hestia OB thread and that was my original target. I was thinking about starting with that using the four MCM drivers and the Vifa just to get going. I then saw the Manzanita CV and like the idea of the 15" with a 4" full range. This seems like it could have a really great sound too. They both seem like good designs and are roughly the same size.

I guess that I will have to break down and get a minidsp as well. I have tried to avoid going this direction but it might be inevitable. Everyone who does an active design really raves about it.

BrassEar · « **Reply #24 on:** 10 Mar 2015, 07:43 pm »

Quote from: rabbit on 10 Mar 2015, 07:55 am

this is just false. no fullrange driver has any dipole dispersion pattern anywhere near treble frequencies, its forword directional, with very poor offaxis control, and a dipole absolutelty needs that.
doesnt come close to CD/waveguide, thats physics, OB or not.

My 40 years as an audiophile and my ears tell me otherwise. I have heard Mr. Linkwitz's offerings - all of them. I have stayed at his various vacation homes and listened to them at length. They are very good speakers but when I come home and listen to my DIY OBs, there is nothing missing - "very poor off axis control" or not.

BrassEar · « **Reply #25 on:** 10 Mar 2015, 07:47 pm »

Quote from: wendelltate on 10 Mar 2015, 03:47 pm

I guess that I will have to break down and get a minidsp as well. I have tried to avoid going this direction but it might be inevitable. Everyone who does an active design really raves about it.

I would go active. It is just not that expensive anymore. Amps are cheap. You can also get an analog active xover for around $100. There is something great about being able to change xover points and high/low pass gains on the fly. It's so easy to dial it in to perfection. Try doing that with passives.

I just wish someone had given me this advice on audio 40 years ago. It would have saved me many thousands of $$ and endless research and searching.

brad944911 · « **Reply #26 on:** 10 Mar 2015, 07:55 pm »

Yea I saw the Manzanitas when I was looking to get started, but it was a little rich for my blood...especially since I'd never auditioned OB speakers. I also contacted Hawthorne audio thinking those would be great to buy. A little cheaper and GREAT customer support and service, but still steep. So the Hestias it was.
I first saw the MiniDSP when looking into open baffle designs(Linkwitz and a few others) and, being old school, I dismissed it. Then I started tinkering with the design of the original Hestia and the sound was not what I wanted, so I went back to researching DSP. I saw mention one day that the Crown CDI amps had it built in; I just happened to have an old Crown CDI 1000 amp that I inherited during my band days...Bingo! I hooked it up and quickly adjusted the sound to my liking. I quickly bought another one. The interface is very useful and intuitive with more than enough controls to correct almost anything. Make sure that you buy the right "plug in" for the MiniDSP if you go that route. I can't remember which one it was.
BTW, I am by no means an expert but have some experience. I just thought I'd give you a little unbiased info. Anyway, best of luck!
Brad

Tyson · « **Reply #27 on:** 10 Mar 2015, 08:03 pm »

If you go the miniDSP route (which I also recommend, strongly) get the 4x10HD and not the smaller 2x4. The 4x10 HD does up to a 4 way speaker (but can also do 2 and 3 ways too), more importantly is has 24/96 decoding, so can act as your hirez DAC. And it has an analog input and 3 digital inputs, so you can use it as a source selector too. AND it has a master volume control, so you can use it as a full function preamp as well. Here's the link:

http://www.minidsp.com/products/minidsp-in-a-box/minidsp-4x10-hd

opa1 · « **Reply #28 on:** 22 Mar 2015, 01:35 pm »

Quote from: MJK on 10 Mar 2015, 01:46 am

My latest OB pairs an Eminence Alpha 15A and a Fostex FF85WK full range driver. The baffle is 18" wide by 24" tall and is tilted back 15 degrees. Second order crossover, active or passive (I like the passive version much better), works well. Good bass from the 15A, the Fostex full range driver is very smooth all the way to 20 kHz, and best of all low cost. Great performance at an entry level price.

Is this newer version using the same crossover as the original with the FE 103E/Alpha15a?

bladesmith · « **Reply #29 on:** 22 Mar 2015, 04:02 pm »

Quote from: MJK on 10 Mar 2015, 01:46 am

My latest OB pairs an Eminence Alpha 15A and a Fostex FF85WK full range driver. The baffle is 18" wide by 24" tall and is tilted back 15 degrees. Second order crossover, active or passive (I like the passive version much better), works well. Good bass from the 15A, the Fostex full range driver is very smooth all the way to 20 kHz, and best of all low cost. Great performance at an entry level price.

MJK,

Have you tried a taller/bigger baffle, say 36" tall x 24" wide baffle with your 15A"s ? Those 15A's have a very good following. I am running the Eminence 15FLA"s in a 24" wide baffle, no wings at all and getting wonderful amounts of bass. Not sure why that is. Seems impossible, but it works. Love my experiment so far.

V.....

MJK · « **Reply #30 on:** 22 Mar 2015, 05:09 pm »

The details of the design can be found here :

http://www.quarter-wave.com/Project12/Project12.html

The page is under construction so I will be adding more details and a full write up in the future. The baffle size, drivers used, and crossover design all go together. If you change one you need to rejuggle the other two. This is a new combination of drivers for me and a redesigned passive crossover. I have built a few other OB speakers all of them significantly bigger, they get smaller with each design iteration, and this "compact" OB has really good bass and feedback on the performance has been very positive.

bladesmith · « **Reply #31 on:** 22 Mar 2015, 05:33 pm »

Quote from: MJK on 22 Mar 2015, 05:09 pm

The details of the design can be found here :

http://www.quarter-wave.com/Project12/Project12.html

The page is under construction so I will be adding more details and a full write up in the future. The baffle size, drivers used, and crossover design all go together. If you change one you need to rejuggle the other two. This is a new combination of drivers for me and a redesigned passive crossover. I have built a few other OB speakers all of them significantly bigger, they get smaller with each design iteration, and this "compact" OB has really good bass and feedback on the performance has been very positive.

MJK,

your write up on OB speakers (Comparison of the Bass Performance of Passive Open Baffle, U Frame, and H Frame Speakers) is very interesting.

thanks,
V....

opa1 · « **Reply #32 on:** 22 Mar 2015, 10:22 pm »

Quote from: MJK on 22 Mar 2015, 05:09 pm

The details of the design can be found here :

http://www.quarter-wave.com/Project12/Project12.html

The page is under construction so I will be adding more details and a full write up in the future. The baffle size, drivers used, and crossover design all go together. If you change one you need to rejuggle the other two. This is a new combination of drivers for me and a redesigned passive crossover. I have built a few other OB speakers all of them significantly bigger, they get smaller with each design iteration, and this "compact" OB has really good bass and feedback on the performance has been very positive.

Thanks! Nice work sheet. I have a baffle in this width. Did a OB project that didn't work well.

It has the Alpha 15 cut out. Are the values on page 5 for the crossover close enough for use now? Or should we wait for more feedback?

MJK · « **Reply #33 on:** 23 Mar 2015, 12:01 am »

Quote from: opa1 on 22 Mar 2015, 10:22 pm

Thanks! Nice work sheet. I have a baffle in this width. Did a OB project that didn't work well. It has the Alpha 15 cut out. Are the values on page 5 for the crossover close enough for use now? Or should we wait for more feedback?

The values on page 5 are what I used.

The crossover is designed to be wired out of phase which is the way I initially hooked it up. The sound was a little dull and I measured a dip in the 500 Hz region. Looks like either my Alpha 15A woofers or the Fostek FF85WK full rangers have the positive terminal marked incorrectly, when I swapped the input wires to the Fostex drivers the sound improved significantly and matched the simulation. The simulation did predict the dip when the drivers were wired in phase.

So if you build the design try the connections to the Fostex drivers both ways. One connection will sound much smoother and lifelike, that is the correct out of phase connection. I will look a little closer at my wiring when the speakers are returned.

Remember to use a SS amp, a tube amp will probably struggle with the low crossover frequency (very poor bass output).

opa1 · « **Reply #34 on:** 23 Mar 2015, 12:16 am »

Thanks again. Looks like the in room SPL is around 82 to 83 average?

MJK · « **Reply #35 on:** 23 Mar 2015, 01:20 am »

Quote from: opa1 on 23 Mar 2015, 12:16 am

Thanks again. Looks like the in room SPL is around 82 to 83 average?

The measured SPL is taken at 1 m on the axis of the FF85WK. It is not normalized for 1 watt or 2.828 volts, it is just the volume the preamp was set to at the time.

The calculated SPL at 1 m with 2.828 volts applied is 87-89 dB, 89 dB at low frequencies trailing off to 87 dB as frequency increases.

matevana · « **Reply #36 on:** 23 Mar 2015, 04:53 pm »

Martin,

Good to see you writing about OB on this site again! Just curious how you calculated the offset on the FF85WK drivers. From the first photo it appears slightly offset?

Thanks,

MJK · « **Reply #37 on:** 23 Mar 2015, 05:35 pm »

Quote from: matevana on 23 Mar 2015, 04:53 pm

Good to see you writing about OB on this site again! Just curious how you calculated the offset on the FF85WK drivers. From the first photo it appears slightly offset?

I don't post much on forums any more, if there is something interesting being discussed I will follow and occasionally add my 2 cents.

All of my designs are done using MathCad worksheet simulations, I iterate the design variables to get a SPL curve that looks promising. The variables include the driver T/S parameters, the OB dimensions and driver positions, and the passive or active crossovers. Measurements of the final build usually track the calculations closely, I usually don't need to do any significant tweaking. In this case, I iterated the position of the FF85WK to minimize the ripple above the dipole hump. I think I ended up with a 1"offset, the pdf file of the simulation will have the exact dimensions. This implies that the baffles are made in mirror image pairs.

matevana · « **Reply #38 on:** 23 Mar 2015, 06:45 pm »

And in the mirrored pair, did you prefer the FF85's toward the inside or outside?

MJK · « **Reply #39 on:** 23 Mar 2015, 09:37 pm »

I always offset the full range driver in my two way OB designs. I have tried both set-ups, full range driver shifted towards the inside and towards the outside, and not heard any great sonic differences. I set my systems up with the full range driver shifted towards the inside, the asthetic difference seems to be more significant than any acoustic difference. With the FF85WK only shifted 1" off center on the 18" wide OB the calculated polar SPL plots are almost symmetric at all frequencies, the predicted dipole ripple is tamed without a huge impact on the predicted polar SPL plot.