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Old 18th March 2017, 10:16 PM   #1
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Default Dual, front and rear firing Acoustats need explanation

So curiosity got the better of me. I put a pair of Model 3 directly behind the Monitor 3, firing in the opposite direction, separately powered. To my delight, they sound phenomenal this way. I've been listening to them like this for a couple weeks now. So I'm assuming the diplole effect is cancelled because of the close proximity and rear firing renders the combo 360 deg dispersion? It seems like the diaphragms are acting against/boosting each other and thereby causing higher sensitivity/efficiency? What I hear are greater dynamics and much deeper sound stage.
I'm hoping someone will be willing to explain this ignorant endeavor technically
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Last edited by Discopete; 19th March 2017 at 11:40 AM.
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Old 19th March 2017, 01:52 AM   #2
gnnett is offline gnnett  Australia
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Hi Did
Fascinating arrangement and not quite sure that your description of cancelling and boosting is correct, unless you are running each pair out of phase with each other.
So, if you are running them in phase, they are adding to each other (as the arrangement you show is with them back to back) in the area between each set of panels. Outside the panels, to the sides, the dipole cancelation is broadened, but behind you have a bipolar dispersion. Additionally this will change with frequency on the basis of the width of the panels. So would be keen to hear what knowledgeable people think of this. The later point regarding frequency balance effects as a function of width, has always puzzled me regarding why the standard stacked multi-panel systems had the same bass balance as the wider, similar number of panelled systems. Great set up anyway and would be keen to also hear what size room and proximity to back wall you are running the set up in.
Kind Regards
Grant
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Old 19th March 2017, 05:15 AM   #3
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Originally Posted by gnnett View Post
Hi Did
Fascinating arrangement and not quite sure that your description of cancelling and boosting is correct, unless you are running each pair out of phase with each other.
So, if you are running them in phase, they are adding to each other (as the arrangement you show is with them back to back) in the area between each set of panels. Outside the panels, to the sides, the dipole cancelation is broadened, but behind you have a bipolar dispersion. Additionally this will change with frequency on the basis of the width of the panels. So would be keen to hear what knowledgeable people think of this. The later point regarding frequency balance effects as a function of width, has always puzzled me regarding why the standard stacked multi-panel systems had the same bass balance as the wider, similar number of panelled systems. Great set up anyway and would be keen to also hear what size room and proximity to back wall you are running the set up in.
Kind Regards
Grant
I tried them out of phase and that just sucks the life right out of the sound but the opposite happens when they are in phase. By saying they cancell the dipole effect, I meant that over all, there is a resultant 180 deg. X2 or 360 deg bi-polar effect. By boost, I mean that it seems the membranes are bucking against each other resulting in a stronger/more forceful action as if like in a dynamic speaker motor, a higher flux density results in a stronger field against the vc. I'm thinking there is an optimal distance between them. I want to remove the panels from the Model 3 and put them on a more diminutive frame with the interfaces on the floor. That way I can get them much closer to each other and move them a little at a time to discover the best distance. The front facing Monitor 3 are 45" from the back wall and the Model 3 are 29", measured from the actual panels. They are 8' apart. The room is open from the left speaker to the dining area, about 5' to the wall from the right speaker. Front and back walls are 17' apart.
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Old 19th March 2017, 09:22 AM   #4
gnnett is offline gnnett  Australia
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Yes, that makes sense and the experimentation may provide a better understanding of the mechanisms at play. I hope someone can add some technical input to explain what you are hearing and worth taking some time to evaluate if there are any negatives in terms of time domain issues, upper harmonics and response fluctuations associated with the spacing.
Best Wishes
Grant
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Old 21st March 2017, 11:44 AM   #5
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I tried a similar experiment with Magnepans, with the rear panel at 90 degrees to the listening axis, emulating the SME arrangement.

Bass an midrange energy raised, along with some room nodes. Imaging wasn't better. I used two identical stereo amps to drive it all.

"FrankenPan"

http://www.quadesl.org/index.php/har.../stacked-quads


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Last edited by anji12305; 21st March 2017 at 11:51 AM.
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Old 21st March 2017, 10:01 PM   #6
WrineX is offline WrineX  Netherlands
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hmm should be less then ideal if you ask me in phase would work beter but at mid high ferq they should be WAAAAAY closer. try filtering the back one then run them out of phase, then you will get a boost.
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Old 22nd March 2017, 03:47 AM   #7
tyu is offline tyu  United States
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Looks Good...all that matters is you like the sound...I done a lot of things with-too Acoustat...panels,interfaces
some will say .........sounds-looks like voodoo magic...maybe
keep up the good work thanks for sharing info
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Old 22nd March 2017, 07:19 AM   #8
gnnett is offline gnnett  Australia
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Originally Posted by WrineX View Post
hmm should be less then ideal if you ask me in phase would work beter but at mid high ferq they should be WAAAAAY closer. try filtering the back one then run them out of phase, then you will get a boost.
Hi Winrex
I think with them mounted back to back and the "interfaces" wired in phase, the panels are out of phase.
Cheers
Grant
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Old 22nd March 2017, 06:07 PM   #9
WrineX is offline WrineX  Netherlands
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Quote:
Originally Posted by gnnett View Post
Hi Winrex
I think with them mounted back to back and the "interfaces" wired in phase, the panels are out of phase.
Cheers
Grant
yeah something you dont want actually. so out phase would result in phase panels
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Old 22nd March 2017, 08:26 PM   #10
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yeah something you dont want actually. so out phase would result in phase panels
Well as I said when I reversed polarity in the Model 3 interfaces there was serious cancellation. This way it's just like more of everything. The sound is 'stronger' for lack of a better term. Attack is harder, decay is more complete, the recording 'room' is louder. Like a more sensitive mic was used.
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