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The power of diffusion Dynamics Plugins
Old 5th March 2010
  #1
Gear Nut
 

The power of diffusion

I know most of the members are here because of their involvement in designing/building recording studios. On the other hand, I am a home theater guy, but I ended up in this forum because it seemed to have the most lively discussions about diffusors.

This forum turned me on to QRDude, and within the last couple of months, I've built two 1D QRD diffusers (N=31 and N=13) and I have two 1D binary amplitude phase gratings (that double as bass traps) in upper half of the rear corners. The end result is that most of my back wall is diffusive.

In my opinion, no other addition to my theater has improved the sound quality so obviously and so immediately. It really is hard to describe the effect of a strong, diffuse sound field to someone who hasn't experienced it themselves.. It's like having a field of pressure composed of every frequency exerting force against the back of my head.. the music seems to surround me.

To flatten the bass response in the room, I had so much fiberglass that the front soundstage was actually too dry sounding (perhaps a little too articulate, if that's possible), to the point that I found myself obsessing about strange sounds the tweeters and subs would make on certain musical passages.

Now that I have created a diffuse sound field in the rear of the room, there is no more "obsessing" over the nuances of each speaker. Diffusion makes the sound bigger and creates a pleasant envelope around the lister that somehow manages to make the music take front stage over the speakers themselves.

Anyway, just wanted to share my thoughts on the power of diffusion. Great stuff. And great forum, guys.
Old 5th March 2010
  #2
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avare's Avatar
 

Thanks for sharing your experience with room treatment. Congratulations too for achieving such pleasing results.

Pleased,
Andre
Old 5th March 2010
  #3
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Weasel9992's Avatar
 

Quote:
Originally Posted by gremmy View Post
I know most of the members are here because of their involvement in designing/building recording studios. On the other hand, I am a home theater guy, but I ended up in this forum because it seemed to have the most lively discussions about diffusors.

This forum turned me on to QRDude, and within the last couple of months, I've built two 1D QRD diffusers (N=31 and N=13) and I have two 1D binary amplitude phase gratings (that double as bass traps) in upper half of the rear corners. The end result is that most of my back wall is diffusive.

In my opinion, no other addition to my theater has improved the sound quality so obviously and so immediately. It really is hard to describe the effect of a strong, diffuse sound field to someone who hasn't experienced it themselves.. It's like having a field of pressure composed of every frequency exerting force against the back of my head.. the music seems to surround me.

To flatten the bass response in the room, I had so much fiberglass that the front soundstage was actually too dry sounding (perhaps a little too articulate, if that's possible), to the point that I found myself obsessing about strange sounds the tweeters and subs would make on certain musical passages.

Now that I have created a diffuse sound field in the rear of the room, there is no more "obsessing" over the nuances of each speaker. Diffusion makes the sound bigger and creates a pleasant envelope around the lister that somehow manages to make the music take front stage over the speakers themselves.

Anyway, just wanted to share my thoughts on the power of diffusion. Great stuff. And great forum, guys.
Thanks for posting. Always great to hear first-hand experiences with things that aren't loaded with technical jargon. I know I personally can miss the forest for the trees sometimes.

Frank
Old 5th March 2010
  #4
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Bubbagump's Avatar
 

For curiosity sake (can't help but have some numbers) what are the room dimensions and what is listening position in relation to the walls/speakers/diffusers?
Old 5th March 2010
  #5
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johndykstra's Avatar
 

Great post, and thank you for your shared experience!
Old 5th March 2010
  #6
Gear Nut
 

Quote:
Originally Posted by Bubbagump View Post
For curiosity sake (can't help but have some numbers) what are the room dimensions and what is listening position in relation to the walls/speakers/diffusers?

The room is 19ft. x 11.25ft. x 7.5ft

Seating position is roughly 7.5 ft off the back wall. Diffusors are on the back wall. Distance between seated position and diffusor fronts is about 7 feet (give or take an inch or two).
Old 6th March 2010
  #7
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Bubbagump's Avatar
 

Sweet! thumbsup
Old 9th March 2010
  #8
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Weasel9992's Avatar
 

Quote:
Originally Posted by gremmy View Post
The room is 19ft. x 11.25ft. x 7.5ft

Seating position is roughly 7.5 ft off the back wall. Diffusors are on the back wall. Distance between seated position and diffusor fronts is about 7 feet (give or take an inch or two).
There you go. Smart placement. I'd probably mix them up with bass traps on the back wall.

Frank
Old 9th March 2010
  #9
Gear Nut
 

Quote:
Originally Posted by Weasel9992 View Post
There you go. Smart placement. I'd probably mix them up with bass traps on the back wall.

Frank
The back corners are bass traps from floor to ceiling. The upper half of these corners are 1D binary amplitude phase gratings, which will double as bass traps at frequencies below the resonant frequency of the quarter inch luan that I'm using for the reflective patches (and the absorptive patches are entirely absorptive). The bottom half of the rear corners is 100% absorptive.

Also on the back wall, I have very deep bass traps mounted to the wall behind the row of leather recliners. Energy from my speakers will reflect and/or diffuse off the leather chairs at high frequencies and will pass through the seats and into the rear absorption panels at lower frequencies.

The end result of all this creative engineering (if I can be so presumptious as to refer to it as engineering -- it isn't really heh) is a rear wall that is reflective and/or diffusive at frequencies above 500hz and mostly absorptive at frequencies below this.

I've got a few more first reflections to kill on the ceiling, and then I'm going to start playing around with the Haas effect.
Old 9th March 2010
  #10
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Quote:
Originally Posted by gremmy View Post
I've got a few more first reflections to kill on the ceiling, and then I'm going to start playing around with the Haas effect.
Have you done any testing in all of this ? The ETC graph is pretty useful for getting
to an acceptable Initial Time Delay (time before the big reflections start) and then
aligning your Haas 'kicker' (a strong reflection to tell everyone that the ITD is over).

Paul P
Old 9th March 2010
  #11
Gear Nut
 

Quote:
Originally Posted by PaulP View Post
Have you done any testing in all of this ? The ETC graph is pretty useful for getting
to an acceptable Initial Time Delay (time before the big reflections start) and then
aligning your Hass 'kicker' (a strong reflection to tell everyone that the ITD is over).

Paul P
I've done plenty of measurement within the room, but my last round of measurements went bye-bye because I forgot to save the file!

So at the moment, I don't have any valid measurement files showing the effect of my latest round of treatments, which was quite extensive. What I did notice before I lost my file was that a big dip that I'd been struggling to remove near the crossover frequency was completely eradicated, although I still have a stubborn hump centered around 30hz that I never expect to fully get rid of. Also, decay times at the lower frequencies have leveled off with those in the rest of the spectrum. I noticed less significant comb filtering as well. Unfortunately, I didn't pay enough attention to the time based measurements (discounting waterfall), and well, the file is gone now, so I'll need to take more measurements to check it out. Maybe this weekend if I get time.
Old 9th March 2010
  #12
jdg
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jdg's Avatar
we need pics! heh
Old 9th March 2010
  #13
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Weasel9992's Avatar
 

Quote:
Originally Posted by jdg View Post
we need pics! heh
Yeah...color me impressed. I'd like to see this.

Frank
Old 9th March 2010
  #14
Gear Nut
 

OK, OK, you guys have encouraged me to finally get a functioning digital camera. My last one is broken, so all I have for pics at the moment is my wife's IPhone. Hopefully I can get some pics up this weekend.
Old 11th June 2011
  #15
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still waiting for those pics...
Old 11th June 2011
  #16
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John White's Avatar
 

Quote:
Originally Posted by takman View Post
still waiting for those pics...
Me too.

Quote:
Originally Posted by gremmy View Post
...the front soundstage was actually too dry sounding (perhaps a little too articulate, if that's possible), to the point that I found myself obsessing about strange sounds the tweeters and subs would make on certain musical passages...
Duly noted the lack of measurement results, this is a very revealing argument for a very dry control room. Yes?
Old 12th June 2011
  #17
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would love to see photos of the N31
cheers,
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