Mating Acoustats with Ribbons

[coloradosound]

My Acoustat 2+2's are about 1/2 too tall for my ceiling,
so I am planning on rebuilding the frames and using
1/8" Aluminum (insulated with a Teflon/fiberglass tape
next to the panels ends) I also have some of the Carver
48 inch ribbons and was thinking that these could be
used to improve treble/dispersion. Since I will be building
a wider frame to accomodate the ribbons, I was wondering
If I should place the ribbons on the outside edge of the
panels (mirror image pair), or place them between the panels?
Also should I keep the angle between the panels (I think
it was 11 degrees), or change the angle, or mount the panels
straight flush with each other?
I plan on using a gentle slope to x-over in the
600-800Hz range.
Any ideas, suggestions, tips, etc.?

 

[david yost]

Ribbons with Planars

I have speculated about this sort of thing myself. I have a bunch of Acoustat panels and 6 of the old Gold Ribbon Concepts drivers...even bought a Behringer crossover/eq to play with. I was going to go with a 2+2 set-up with the ribbons in the center. My concern with mounting the ribbon inboard is that it could be modulated by the bass panels more than if it were mounted to the outside. On the other hand, the original Quad 57 does this without audible problems. I would be tempted to run it this way for symmetry of horizontal dispersion if nothing else.

You might want to get in touch with Thomas W. from the Infinitely Baffled subwoofer site, as I think he played around with Acoustat arrays with ribbon/leaf tweeters some years back.

 

[ThomasW]

I run a similar setup for my mains.

On each channel I have a pair of 1+1s. Between them is a B&G RD75 and a line array of Technics leaf tweeters. This is a variant of the classic Quad arrangement.

The Acoustats are used as mid woofers, they run from 80Hz-600Hz. The RD75 runs from 600Hz-5K, the leafs from 5K up.

Crossover functions are handled by Marchand units.

Where in Colo are you? I'm in south central Denver if you want to stop by for a listen

 

[coloradosound]

Sounds interesting, Thomas. I'm down here in the Springs.
I also have some (2) of the B&G RD75s!, but one of them is non-
functional, but I do have 4 of the 48in. Carvers that all work!
I think the BGs roll of around 18K (which is probably why
you are using the leafs?). I want to try to keep it simple as
possible and I was also looking at the Marchand X-Os.
I like their line level passive units (small inductor and cap!).
Maybe we can get together when we can find the time.

 

[ThomasW]

Send me an email if there's a day when you're going to be up in Denver. My schedule is very flexible so I can accommodate virtually any time or day that's convenient for you...

 

[coloradosound]

Finally found another set of RD75's of which one of those is also bad.
Providing I repair the bad units, I think I can do something like the Polk
Stereo Dimension Arrays (SDA's).
Any thoughts on correct spacing between RD75's (will probably build
a narrow HF ribbon to fit between the RD75's to cover the top.
Also any thoughts on the response shaping for the crossfeed drivers?

http://www.parts-express.com/catalog/pdf/2010/198pec10.pdf

http://www.parts-express.com/pdf/264-710.pdf

The 9 in. panels are the electrostats.
Can't seem to find much info on how the Polk SDA's worked though.

 

[coloradosound]

Ok, seems my attachment didn't make it first time.

 

[a.wayne]

Why don't you build your own ribbon tweeter , the BG 's are so hard sounding and you could do it for about 30 % of the cost of one .

 

[coloradosound]

Why don't you build your own ribbon tweeter , the BG 's are so hard sounding and you could do it for about 30 % of the cost of one .

I saw pics posted of ThomasW's setup. I did certainly have something in mind as
a higher freq. ribbon or leafs to cover from 5k up and most leafs are too wide
with the complete assembly.
Thought crossed my mind to roll my own, what was the spacing from the driver
centers to get the SDA effect?
I don't remember but I thought it was somewhere between 6-7 in. and that
would help me figure how wide to make my tweeters.

 

[david yost]

If I had 4 BG75's, I would be tempted to try a F and R Ambiopole set-up using 2 X electro-music.com's AmbiophonicDSP crosstalk cancellation program. This would be much more flexible than SDA and probably sound a lot better too!

 

[ThomasW]

Finally found another set of RD75's of which one of those is also bad.
Providing I repair the bad units, I think I can do something like the Polk
Stereo Dimension Arrays (SDA's).
Any thoughts on correct spacing between RD75's (will probably build
a narrow HF ribbon to fit between the RD75's to cover the top.
Also any thoughts on the response shaping for the crossfeed drivers?

Can't seem to find much info on how the Polk SDA's worked though.

B&G will rebuild the RD75's for a fee. I had one rebuilt a while back cost was $220. Not what I'd consider a DIY project..

The Polk SDA is nothing more than the old Dyna-quad (ambient recovery) design with hot leads from the corresponding sides run to the hot in and a common wire run between the two (-) terminals. Personally I can't imagine this being of any benefit with dipoles.

 

[coloradosound]

If I had 4 BG75's, I would be tempted to try a F and R Ambiopole set-up using 2 X electro-music.com's AmbiophonicDSP crosstalk cancellation program. This would be much more flexible than SDA and probably sound a lot better too!

It sounds like I would have to insert a computer into the system and go through a
sound card?

 

[coloradosound]

The Polk SDA is nothing more than the old Dyna-quad (ambient recovery) design with hot leads from the corresponding sides run to the hot in and a common wire run between the two (-) terminals.

I think the SDA was different than the Hafler-Dyna quad setup in that the ambient
recovery was just out of phase signal extracted by running rears from the two (+)
terminals and anything different between the two(+) was out of phase ambient info.
The SDA, If I recall, had attenuated, equalized, inverted signal crossfed to other channel.
So, it sounds like there are two distinct stereo signals crossfed and inverted. The
spacing between the normal signal of inner driver and the outer driver of a channel
set up the delay timing to produce the SDA effect?

Personally I can't imagine this being of any benefit with dipoles.

I was thinking of some more fairly heavy damping in the BG ribbon part of the system
and leaving just the little felt pads on the electrostat panels, so the electrostat
would be more dipolar, and then become more monopolar in the highs