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Old 27th February 2013, 12:40 AM   #791
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6" thick foam (grey packing) seemed fine to me.

2 x 3" thick pieces 3' x 3', like the convoluted stuff at parts express without the bumps............
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Old 27th February 2013, 06:46 PM   #792
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Hi Norman,

Yes, the lighter, less dense material used the thicker the barrier has to be. So 6" ~ 15cm is a good start for grey foam, I guess. Been reading that glass-wool of same thickness can absorb well down to 100-150Hz. Some denim-cotton batting stuff out there comes in even thicker and works lower than that too, they claim...

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Charlie
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Old 27th February 2013, 08:33 PM   #793
lolo is offline lolo  France
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Quote:
Originally Posted by charlieblue View Post
Forgot to mention, sound wave angle of incidence seems to play a role on the absorption capabilities of said materials, always depending on frequency. Hope that for our application of a barrier, the a coefficient will not change much.

Is it my impression, or does the rigid / reflective barrier start looking better now? I mean, you just pick a slab of plywood or mdf (which can be very heavy indeed, and thus block low frequencies well), cut off a piece for the legs so as to bring torso and head close to the barrier at the seating possition, and that's that! No need to hassle over selection of absorptive materials, calculating coefficients, or worrying over airborne particles from the acoustic insulation..
thanks Charlie, I also read Keele's paper again and it makes sense. I actually do have 4 leftover large pieces of flooring plywood ,heavy duty. I shall try again over the weekend. God my wife will kill me!
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Old 27th February 2013, 09:57 PM   #794
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to me a barrier would work best because you don't have the reflection of the left speaker hitting the right wall then coming at your head (wrong direction).

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a removable wall, similar to what you may fine in office spaces.

Norman
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Old 28th February 2013, 08:41 AM   #795
lolo is offline lolo  France
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what to think of this setup, said to work as the barrier but without it?

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Old 28th February 2013, 08:52 AM   #796
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I've no idea.
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Old 28th February 2013, 08:59 AM   #797
Elias is offline Elias  Finland
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Quote:
Originally Posted by lolo View Post
what to think of this setup, said to work as the barrier but without it?

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I think this is very interesting.

Ambiophonics

The angle of the side speakers is set to +-55 degrees, which gives the minimum of IACC. This maximises stereo separation.

In this case it also improves spaciousnes since the feed signal to the side speakers is MS stereo side signal S = L - R.

There is something similar to the 3 speaker linear stereo matrix where the side speakers also get part of signal S. For example with matrix x=0.5 left speaker signal is
Ls = L - 0.5*R = 0.5*L + 0.5*(L - R) = 0.5*L + 0.5*S

If the two innermost speakers are very close to each others or if you merge them as one, you'll arrive to the 3 speaker stereo matrix

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Last edited by Elias; 28th February 2013 at 09:03 AM.
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Old 28th February 2013, 09:01 AM   #798
lolo is offline lolo  France
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so it's a quadraphonic matrix? any amplifier restrictions? There are no secrets for you Elias! :-)
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Old 28th February 2013, 09:06 AM   #799
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This will not give the same results as a barrier or RACE but it will sure beat stereo. This is Elias' territory...
I have yet to get ot this train
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Old 28th February 2013, 12:41 PM   #800
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Quote:
Originally Posted by lolo View Post
God my wife will kill me!
I know, I know... to get rid of the nagging, I once got out and rented a place of my own, just to house the ambio. On the plus side, I got to push the speakers anyplace I wanted, even mid-room, 4m from the front wall! Ah, those were the days...

Quote:
Originally Posted by Elias View Post
I think this is very interesting.
.
.
.
Elias, just a thought:
Would moving the outer speakers (G-D & D-G) into an arc - always at 55*, but so as to maintain equal distances - be better for time alligning of this 4 speaker setup? Or isn't that necessary with this arrangement?
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