Gravity Well Of A DarkStar

opnly bafld · « **Reply #640 on:** 22 May 2006, 01:48 am »

Russell,
Is the first word now or no, in your previous post?

The only way I can think of right now to get the drivers at equal distance, is a baffle that tilts back on the lower half and foward on the upper half. (>)
Not sure how having the top fullrange driver higher but pointing down to listening height will affect soundstage.
Lin

opnly bafld · « **Reply #641 on:** 22 May 2006, 02:41 am »

The first pair of speakers I used to try this OB thing were Pioneer 6 1/2" whizzer cone drivers that were given to me.
The Pioneers sounded horrible, but they gave me an idea what OB would sound like.
So I have a suggestion for any that are sitting on the baffle(fence) and not sure about spending $250 for the Visatons to try this OB thing.
Try a 6x9 car coax speaker, for less than $75 including some MDF you can hear what this is all about.
You can use it alone or with a sub and get a taste of what the B200 does.

....Or you can get the B200s and if you don't like

, you can sell them and get most of your money back, or if you could use some great sounding standmounts, send the drivers to Omega for use in some A8s.

Lin

nodiak · « **Reply #642 on:** 22 May 2006, 03:28 am »

Excuse the interuption, but the Fostex don't have the excursion for OB (xmax= .4mm !), unless you roll them off from 300+ hz on down. And imo you would need at least 2nd order to be able to play them at all medium loud. The 83e's are low spl for Fostex anyway. Trust me on this as I tore the vc's on a pair of 108's that way, was just testing them at medium spl's. Never again with similar Fostex without at least a cap.
I used 167e's and 107's with caps on them on OB, forgot the cap value, so they were crossed out ~ 300hz down. Worked ok with 12"bass below.
The qts won't matter if crossing out in this range anyway. And they do make good mids on OB with a decent bass driver.
Use any xmax ~ 4mm and up driver to get the OB magic, midbass on up, but be careful with the volume. Some car speakers are highish qts...get it all with a coax...
The B200's are studs even with lower xmax, pretty special in that category.
nodiak over and out.

Russell Dawkins · « **Reply #643 on:** 22 May 2006, 07:35 am »

Lin, I think the word was no, but it might as well have been yes - I was in a hurry to get to supper.
I am guessing the center to center distance of the Wharfedale 12s in the case described was about 2 1/2 feet.

I don't think things are as carved in stone or critical as you may think at this stage.

1] It isn't necessary or even preferable for the drivers to be firing directly at you, so it may not be necessary to angle the top one down. A flat baffle might work as well.

2] equal distance from drivers to ears does not have to be exact, just approximate, and be aware that in a vertical array of 2 or more speakers covering the same frequencies, there will always be phase cancellations that are more obvious with closely spaced speakers. This was known as the venetian blind effect for the way it sounded when you moved your head vertically in front of a vertical array of speakers.

As to your case, it sounds like you already have close to an ideal set up. It has the virtue of simplicity. Leave the baffle board flat and tilt it back as you suggest. Only trouble is, the image is a bit low and that would bug me, but that's me.

If I were you and had the time and inclination to play around and get picky, I'd experimentally extend the baffle vertically so the upper driver was as far above your ear height as the lower one is below.

This would mean mounting the upper driver so its center is about 63" from the floor, assuming a 36" seated ear height and the lower driver center at 9" off the floor.
If you could swing it, tilt the upper down and the lower up so that the axes of the drivers cross just slightly ahead of you, giving you the same kind of benefit I've described elsewhere with regards left right imaging, only in the vertical domain. This would also allow for the 5º effect, that is, a lot of drivers actually sound better 5º off axis than on axis! (IMO)

opnly bafld · « **Reply #644 on:** 22 May 2006, 11:45 am »

Nodiak,
Thanks, I appreciate your experience and knowledge of such things.
I changed my post to 6x9 car coax.
Lin

nodiak · « **Reply #645 on:** 22 May 2006, 02:43 pm »

Hey Lin, my knowledge came from an experiment born of ignorance! Man, that type of le$$on $tick$!
Appreciating the various stages being built for the B200 space travelling ship!
Don

Dmason · « **Reply #646 on:** 22 May 2006, 04:14 pm »

Just noticed this little detour on the matter of experimentation; I have a pair of old Isophon car speakers pulled out of an old (1971) Volvo 245. I had read somewhere that these were jewels, and they are. To my amazement they had AlNiCo magnets... They sound fantastic by any standard believe-it-or-not, and on an open baffle. My suspicion is that high quality car speakers are an untapped treasure of OB drivers. The now-legendary Ciare CH250 sounds great on OB, and is now enjoying a career as a car speaker, in my son's truck! Also, the Delco car speakers, which I plucked out of a Honda Accord, sound pretty good too. I think it best to stay away from the shiny coaxial and stick with the paper cone stuff. There are some finds out there, so take a picnic to the scrapyard, my opinion, and look for Volvos, Merc's, and BMW's.

nodiak · « **Reply #647 on:** 22 May 2006, 05:36 pm »

damn, my volvo's an '85! off to seek out old models...

sts9fan · « **Reply #648 on:** 22 May 2006, 05:39 pm »

well my 91 240 wagon did not come with nice speakers but she is still chuggin at 267k...

mcgsxr · « **Reply #649 on:** 22 May 2006, 06:08 pm »

Well, this being a long weekend up here in Canada, I took the opportunity to play around with the system, and do a little exploring. I am interested by what those using 2 pair of b200 are saying, but as I don't own 2 sets, but I do own this sub...

Having followed with interest, the idea of H baffle bass, and recently becoming aware of what happens when you use only 1 voice coil in a DVC sub... I decided that I could not resist the $25 to build one up.

Leveraging a 2001 model Rockford Fosgate HX2 12 inch, and using only 1 voice coil (thus doubling the QTS to 1...) and pushing 300w through it, I figured I would get some idea of what open baffle bass is like. I use the sub out of my little JVC, and feed that to my old Teac EQ, then on to the sub amp.

This way, I can boost 30, 60 and 125Hz accordingly, and trim also, should that need arise. Shade tree? Oh yeah, but free, so let's get on with it!

The last pic shows it in place, with the borrowed Omega 3 speakers, and how I have it located.

Good sound, not the best bass I have ever heard, but worth playing around with. I look forward to the return of my b200 panels, and seeing how well this can integrate.

It plays low bass well, when boosted around 9db at 30Hz, but seems to lack upper bass, so I am waiting to hear the Visatons again, to play around more with Xover settings, and boost and cut with the analog EQ.

Fun to be sure, and my daughter helped with the chalk lines...

Dmason · « **Reply #650 on:** 22 May 2006, 06:24 pm »

Mark

Very nice, thanks for the shots, .. a literal "H" ...you need to put a hat and shoes on that load for it to work properly. Are you going to wire for both voice coils? One can also flare the sides in a trapezoid configuration, a la Eastern Audio Works, to form a quasi-horn load front, and still retain the dipolar rear. THis way you gain acoustic coupling, AND dipole, all in a real easy build.

What is that pink stuff behind the plastic?

I will be interested in what the H sounds like fully clothed, and with the Visatons. This could be a superb short cut from Linkwitz' dipole enclosures like DarkStar, which are a tough build, and mounting the drivers is really not a fun thing, that build is to be avoided, if possible. Thanks for the pix, and look forward to more tests. Hope you like the Omegae as much as I do.

mcgsxr · « **Reply #651 on:** 22 May 2006, 06:57 pm »

Yes Dan, it does need more "finishing" but it is designed to slide right under an IKEA LACK side table... painted black, it will just blend with the coffee table - sure, odd to have out in the room... but that is me!

I like these older Omega's, but they pale in comparison to the b200, in my room, to my ears etc.

I don't plan on using both voice coils, as that causes me two problems.

1 - since both VC are 4 ohm, I end up with either a 2 or 8 ohm load - the 8 ohm load lowers my plate amp output to 200w, and a 2 ohm reduces it to a pile of garbage, after it blows up...

2 - both VC in use would also restore the 0.48 QTS, vs the effective 0.96 I have now, as I understand it, with only 1 VC in use.

I could be wrong...

Dmason · « **Reply #652 on:** 22 May 2006, 07:02 pm »

Hmm, maybe use one to avoid the proverbial dust bin of history, and LP< ~60Hz or so. Looks like a nice woofer, and saves audio $ for two more B200's

opnly bafld · « **Reply #653 on:** 22 May 2006, 08:23 pm »

Hi Mark,
You really need to try 2 B200s.
JiffyBoob put it best, 1+1=4

Lin

mcgsxr · « **Reply #654 on:** 22 May 2006, 09:40 pm »

I know, I know, the best sound comes from 2 pair of b200... but bear with me, I am just fooling around with what I already own, and exploring in my own direction.

When I have the $$, I will have a pair of b200 running, trust me, I believe all that each of you are claiming, I have seen the light!

Now, I am simply sharing the photos of the ugliness, as it emerges, for a simple coffee table sized dipole, H baffle sub.

In time, I will build one of these, using the lid of the table as the missing top panel, and with a bottom panel, this is simply the skunkworks 2 hour Sunday afternoon, $25 version!

This pic should highlight the intended direction - remove the 4 post legs, rebuild the H to fit exactly the dimensions of the table top, and have a nicer version. When finished, the H will be the exact size of the OD measurements of the table top, and will replace the legs that you currently see.

At present, it is 15 inches wide, with 22 inch sides - can one of you math guys help me out with what that should translate into, for effective baffle size, and thus expected cutoff etc?

The woofer is a very robust one, 29Hz FS, 14mm XMAX in each direction etc, I can put the power to it, it sounds decent - no raving, just decent. More of them would be required to really move air, ala KCHANG...

Dmason · « **Reply #655 on:** 22 May 2006, 10:34 pm »

Mark

About 37 inches fore and aft. Nice effective baffle width, with LOTS of boundary lift. I like the table motif, sort of architectural speaker design. Sounds like that thing dont gots much on the Dayton IB-15.

opnly bafld · « **Reply #656 on:** 22 May 2006, 11:13 pm »

Nice Mark, very nice.
Please report performance when done.

Ordered 12mh inductors today for the lower B200.
They should give a 6db/oct. rolloff starting at @75hz.
Should receive them tomorrow.
Lin

opnly bafld · « **Reply #657 on:** 22 May 2006, 11:19 pm »

Dan,
The pink stuff behind the plastic at Mark's home is something used in colder climates.
It is called insulation, in some places you can't have too much.

Lin

lonewolfny42 · « **Reply #658 on:** 23 May 2006, 10:43 am »

Mark....Thanks for the photo's !!!

mcgsxr · « **Reply #659 on:** 23 May 2006, 01:02 pm »

Thanks for the math help johnincr, I appreciate knowing a little more about the expected FR of the build - I know that this is completely backward design to most of you, but sometimes it pays to think differently about design. When I build it out to the exact size of the table top, it will be 22 inch sides, and 20 inch panel where the woofer lives - I assume that this will only have a marginal effect on the sound.

I will use the sub out in the middle of the room, I know that I need to have it parked out where the speakers are, I just figure that it might look a little better as a table, than as raw mdf... then again, ALL my stuff is raw mdf, so perhaps I should just embrace it!

Dmason - the pink stuff behind the plastic, all around the top half of my unfinished basement, is indeed pink insulation - I guess OwensCorning must have won the bid for all the houses around me have that. They insulate the portion of the concrete wall, that leads to just below ground level outside, as deep as frost is expected to penetrate I assume. In time, I will remove all that, and build 2x6 exterior walls, Roxul SafenSound in the ceiling etc, but for now, that is how it is...

The old Fosgate woofer is a decent one, I abused it fully in my BMW for a couple of years, with 500w, so I know that it responds well to lots of power, in a sealed enclosure. Compared to the reputedly excellent IB15, it has a smaller diameter, higher FS, higher effective QTS, and handles more power, but really, it is free to me, that is why I am using it... I know that the IB is a far better woofer, and a pair of them would be excellent, but for a couple of bucks of mdf, it is interesting to get a sense for what that can accomplish.

Glad to share the pics, it really is the only way to fully communicate what is going on, in my estimation. I would love to see some pics of the pair or more of b200 that some around here are using.

I will report more, as it comes, when I have the time to assemble a better version of this woofer.

What is interesting about it, is that I can hear it distort at higher volumes, or at least that is what it seems like - not unlike when I push my ported sub, I can hear it change the nature of the bass.

I assume this is why people use MANY woofers for open baffle bass, to allow for more air movement, with lower distortion, better power handling etc.