B200 Open Baffle Dimensions

jkelly · « **on:** 9 Jan 2006, 08:58 pm »

Starting the B200 journey.
I have 2 B200 speakers and found 2 finished 43 x 23 panels at work for the baffle.
However, I am not sure where to put the speaker on the baffle.

Also what is the right size hole in inches for the B200?

Any suggestions on baffle size and speaker placement would be helpful!

Thanks,

Jeff

JLM · « **Reply #1 on:** 10 Jan 2006, 12:04 am »

Jeff,

Mount it slightly off-centered so as to vary the distance from center of driver to the edges as much as possible. Some mount it lower to gain more bass from the effective baffle extension provided by the floor (remember you can tilt the baffle back).

25.4 mm = 1 inch

J North · « **Reply #2 on:** 10 Jan 2006, 02:30 am »

Use the "golden mean" if you can.

Mount the drivers .618 * 23 high and .618 * 43 from the inside edge (mirrored pairs).

jkelly · « **Reply #3 on:** 10 Jan 2006, 02:34 am »

Very helpful.

I was thinking of using a vertical stance but I think your are suggesting a horizontal profile. 43 across and 23 high - would that be a better configuration?

Jeff

J North · « **Reply #4 on:** 10 Jan 2006, 02:56 am »

sorry for the confusion

Vertical is the way to go.

I was suggesting to use the .618 factor to calculate *where* on the baffle you would mount the drivers.

I would also suggest you trim the height down a but as you don't need the full 43 inches. 1.618 * 23 = 37" of height would be ideal. The width would stay at 23"

So, you would mount the driver centre 23" above the ground and 14" from the inside edge on each speaker.

Hope that helps.

jkelly · « **Reply #5 on:** 10 Jan 2006, 03:05 am »

Cool. Sounds like a plan. I will let you know how it sounds.

Thanks,

Jeff

JeffB · « **Reply #6 on:** 10 Jan 2006, 03:13 am »

I found this graph showing baffle size vs frequency, but I don't understand it.
http://melhuish.org/audio/baffle.html

A baffle is 2 dimensional, but the graph only shows one dimension.
Is this graph only for square baffles?
If a baffle was 40" tall but 9" wide would the frequency be 80Hz or does it need to also be wider?

Or is the smaller dimension the deciding factor, such that
40" tall by 9" wide would yield a frequency of about 320Hz.

JLM · « **Reply #7 on:** 10 Jan 2006, 11:17 am »

OBs are about dipole dispersion, not bass response. As the referenced graph shows you'll never get full, deep bass from OB without EQ of some sort and/or a sub.

Except for infinite baffle speakers, all speakers suffer from baffle step losses (what the graph is showing). By varying the edge distances you'll have 4 smaller steps versus 1 bigger step.

As wavelength increases as frequency its size matches the baffle size and the back wave meets the front wave (perfectly out of phase) so the two cancel each other. Sound wave size = 13,200/frequency (in inches), so baffle step losses start at 6,600/frequency (in inches). For residentially sized OBs this begins at the midrange frequencies. The result is the classic dipole diffusion pattern, with little output in the plan of the speaker so that there is little room gain.

BTW infinite baffles are used primarily for bass and can only develop the front of the soundstage.

mcgsxr · « **Reply #8 on:** 10 Jan 2006, 02:35 pm »

Sorry to not have responded for a while to this... two young daugthers has kept me away from the PC for extended periods of time!

I started with flat open baffles of about 48x36. I mounted the driver around 28 off the floor, and 16 in from the inside edge. I found that arrangement, especially tilted back so that the drivers "met" above my head about 2 feet, and in front of me by about 2 feet, to be great.

HUGE Panels though...

So, next I cut each panel into 3 pieces, and used piano hinge to "fold" in the sides to varying extents. I also decreased the overall H by 4-6 inches. This is much more manageable, but I can no longer tilt the baffles, and I find that it sounds better when tilted a little.

For what you are describing, they are relatively narrow, and I wonder what bass you will get - not sure of room size, bass preference etc, so it will depend.

They are good drivers, and with experimentation, I bet you will find something that works for you!

JLM · « **Reply #9 on:** 11 Jan 2006, 10:14 am »

Mark,

Did you ever try adding EQ to extend the bass? IMO a sub alone won't work as the OB roll-off is just too high, even from baffles the size of yours.

take care

jimbop · « **Reply #10 on:** 12 Jan 2006, 03:14 am »

Mark, if you cut an angle in the bottom of each wing, you could tilt the baffle. If you install a set of threaded spikes at the back of each wing, you could adjust the angle.

JD

jkelly · « **Reply #11 on:** 12 Jan 2006, 03:15 am »

Instead of starting a new thread - what is everyone who has the B200 using for speaker cables and connections to the driver?

Jeff

ooheadsoo · « **Reply #12 on:** 12 Jan 2006, 07:18 am »

I'm temporarily using alligator clips

Couldn't find any crimp quick disconnects...

Wire is 14ga. or 12ga. magnet wire I got from a fellow AC member.

mcgsxr · « **Reply #13 on:** 12 Jan 2006, 01:50 pm »

I am using Bolder M80 speaker cables, and I use CAT5e from the binding posts to the driver itself.

And I should have been more specific about the ability to lean the baffles since installing the piano hinge, and wings - yes, if you can cut wood accurately, and have the time, you can angle the wings to allow for said preferred (in my case) lean. In my case, I have not had the chance to measure, mark, and cut the wings, to allow for that lean.

That idea about spikes sounds interesting...

And to JLM, I don't have a digital EQ, and am playing around with an analog EQ (old Teac 12 band per side jobbie) but feel that although I can alter the frequencies heard, the veil over the whole spectrum negates the betterment of the bass. Lesson? Get a Behringer, like everyone has been saying...

Or, just admit it, and use that darn JVC EX A1, since it makes the best music with the present baffles, that I have heard yet!

fabaudio · « **Reply #14 on:** 12 Jan 2006, 03:19 pm »

mcgsxr

Assuming you had a JVC ES1 at one time what advantage(s) does the JVC-EX A1 have over the ES1?
Thanks
Frank

audiojerry · « **Reply #15 on:** 12 Jan 2006, 03:57 pm »

anyone got photos to post?

mcgsxr · « **Reply #16 on:** 12 Jan 2006, 04:52 pm »

These were the first baffles I built - I have since vertically cut them into 3 pieces, and installed piano hinge so that they don't take up quite so much space... This is also my old listening room - my present space is around 4x the size, but an unfinished basement, so not the most visually appealing!

As for the EX A1 vs the ES-1, yes I can offer a little insight.

The ES-1 that I had came used, from a fellow AC member - I also lent it to JLM, as the unit was coming from the US anyway, and he lived sort of half way between the origin, and me up here in Canada, and I know that he was interested to get an ear around that highly touted technology. I found that it was nice, but not great for me. I preferred the Bolder modded Teac by far, as it seemed to have more punch, and better clarity. I used the JVC with my old Totem Rokks, the DIY Cable/CSS WR125S running full range, and the KIT41 from the same folks. I moved the ES-1 along before I built the OB b200's, so I cannot comment on it with them.

In direct comparison to the EX A1, I would say the obvious first - one is a 5 channel receiver, the other a 2 channel, all in one type device, that includes DVD playing, tuner, etc. The build quality of the EX A1 is in a different state - the little unit is rock solid, nice aluminum case, copper screws (think Sony ES build quality), binding posts, and if you Google this little guy, you will see that it was built from scratch to be the "statement" piece for JVC at the time, using their "Hybrid Digital Feedback" technology.

OK, tactile and marketing rant off - how does the little bugger sound?

Well, the built in source holds it back, so if you can use an external one (I used my Nakamichi cd player feeding a Bolder Mensa) into the AUX input, you will hear it as it should be heard. Rich, full, clear, and really pleasing.

On the b200's, it is the best I have heard yet, for realistically reproducing all but the lowest 1.5-2 octaves - most other amps get off at least an octave higher.

I have continued to try amps since, but this one is sitting on a shelf, waiting for me to stop kidding myself, and just admit that I will use this boring old, non-audiophile, mass market company amp, and love the sound!

I have tried the Panny XR55, it did not do it for me, I own a gainclone (it is the equal of the JVC in many ways, but does not produce the bass as well), and the Bolder Teac was sold off, etc.

STOOOOPID value at the $240 I paid off eBay, for a new unit, from the Sharper Image.

Not a great deal at the $1000 list price up here in Canada.

Recommended at the under $300 price point, in my experience, and since it was designed to play with single drivers... perfect for the b200 thang - has a sub out, but you cannot control the cutoff frequency, and JVC techs could not even tell me where it knifes the bass from the mains when you activate it...

That help?

audiojerry · « **Reply #17 on:** 12 Jan 2006, 06:24 pm »

Thanks for the photo - wow, that's gonna have a very dismal WAF, I'm afraid.

I like your idea of hinging it - open it up when in use, folding it down when not. Did you ever experiment with the baffle being partially folded on the hinges?

It reminds me of a baffle used for testing drivers. Who ever would of thought of it as a solution.

I wonder if anyone has tried an open baffle where the baffle is a horn.

mcgsxr · « **Reply #18 on:** 12 Jan 2006, 10:25 pm »

Yes, WAF RIGHT OUT THE WINDOW...

I only use the baffles partially folded back, now that I have it configured that way - I cut the baffles so that 14 inches are the "face", and the two wings are of differing sizes.

I will snap some pics, but I am embarrassed about the unfinished basement listening room...

mcgsxr · « **Reply #19 on:** 12 Jan 2006, 11:48 pm »

Here are some pics of the folded baffles, as I use them, and a couple of pics of my lowly basement audio cave corner!