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post #61 of 80 Old 09-17-2008, 06:59 AM
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Why have a blackbelt when only a red sash will do?

Part of the problem is that many (noobs and advanced noobs) aren't certain about what question should even be asked. I do (like most of you) prefer that a bit of research (frustrating or otherwise) be conducted before jumping in. However, there is no such thing as a stupid question...now, stupid answers on the other hand...

If you're serious about getting a handle on all of this, Floyd Toole's new book "Sound Reproduction" is available on Amazon. A great read and good reference. Terry and I are currently memorizing the book. Ethan can't read, so we'll brief him. (Sorry, Ethan. Not true but you take pokes so well.) Kraz will sort us all out during the oral exam.

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post #62 of 80 Old 09-17-2008, 09:55 AM
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Quote:
Originally Posted by Dennis Erskine View Post

Why have a blackbelt when only a red sash will do?

Part of the problem is that many (noobs and advanced noobs) aren't certain about what question should even be asked. I do (like most of you) prefer that a bit of research (frustrating or otherwise) be conducted before jumping in. However, there is no such thing as a stupid question...now, stupid answers on the other hand...

If you're serious about getting a handle on all of this, Floyd Toole's new book "Sound Reproduction" is available on Amazon. A great read and good reference. Terry and I are currently memorizing the book. Ethan can't read, so we'll brief him. (Sorry, Ethan. Not true but you take pokes so well.) Kraz will sort us all out during the oral exam.

Hahahaha...
I'll have to check it out.
Thanks Dennis!
Ethan, just remember that despite their good humored ribbing, we all love ya on AVS.

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post #63 of 80 Old 09-17-2008, 09:57 AM
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Yeah you guys read it and I'll just ask the dumb questions about it on here - will save me some bucks and some time.

Hope it is not just his CEDIA slides redone like that "booklet" from a former HT designer now innkeeper...as there went my pizza fund for the month. Should have waited for the Stereophile columns version on that one.

Funny - Amazon's list of customers who bought this book also bought the usual list of other audio/acoustic books - then "Nine Lives" by Steve Winwood??? Ethan are you the Stevie fan?
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post #64 of 80 Old 09-17-2008, 11:29 AM
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Originally Posted by krasmuzik View Post

Ethan are you the Stevie fan?

Sure.

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post #65 of 80 Old 09-18-2008, 05:15 AM
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Quote:
Originally Posted by krasmuzik View Post

Yeah you guys read it and I'll just ask the dumb questions about it on here - will save me some bucks and some time.

Hope it is not just his CEDIA slides redone like that "booklet" from a former HT designer now innkeeper...as there went my pizza fund for the month. Should have waited for the Stereophile columns version on that one.

Funny - Amazon's list of customers who bought this book also bought the usual list of other audio/acoustic books - then "Nine Lives" by Steve Winwood??? Ethan are you the Stevie fan?

Please, by all means, in six months, go ahead and ask away. If I can, I'll be more than happy to help instead of bi%$ching about it.
I'll rememeber that I too was in the same place as the person/member asking the questions.

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post #66 of 80 Old 09-18-2008, 06:15 AM
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Hope it is not just his CEDIA slides redone

Note even close. A very definitive work.

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post #67 of 80 Old 09-18-2008, 08:10 AM
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Dr. Toole introduced me to the mouthful "Interaural Crosscorrelation Coefficient". By far one of the most helpful CEDIA classes I have been to and he is a Kingpin in the world of small room acoustics.

I used to have an open mind but my brains kept falling out.
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post #68 of 80 Old 01-05-2009, 10:23 PM
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Quote:
Originally Posted by Dennis Erskine View Post

That is showing the off axis response has the same general shape as the on axis ... a good thing. In this case, you'd want bad panels rather than absorption at those Mirror Points. Quest (www.questai.com) has some new abfusor panels we tested at CEDIA. They did an outstanding job for bunches less money than the RPG product. We also tested a 4" multidensity/laminate panel that did a very credible absorption job down to 125Hz.

I understand that the BAD panels are good for shorter distances. If the closest seats are 7' from the first reflection point, would another option be the RPG Abfussor panels?

I have not seen any change in the Quest website--so maybe they are not proceeding to offer their abfusor panels? Anyone seen them?

I did find something called the HiPer panel from Acoustics First. http://www.acousticsfirst.com/HiPerPanel.htm Anyone know if these are a useful alternative to RPG's BAD?
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post #69 of 80 Old 01-06-2009, 11:58 PM
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The RPG Abffusor is essentially a directionally independant absorber only - not diffusive.

I believe the Quest product and the Bad Panel are both billed as LF absorptive and HF diffusive.

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post #70 of 80 Old 01-07-2009, 12:47 AM
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Quote:
Originally Posted by jamin View Post

The RPG Abffusor is essentially a directionally independant absorber only - not diffusive.

I believe the Quest product and the Bad Panel are both billed as LF absorptive and HF diffusive.

RPG claims both diffusionand absorption:

>>The Abffusor, with it’s modulating surface topology, offers the perfect combination of absorption and diffusion to tame reflections from the front wall, side walls between the speakers, and listening position and also directly behind a sofa placed against the rear wall of the room. The Abffusor is a hybrid surface, absorbing some of the incident sound, while diffusing any energy that is reflected.<<

Of the BAD panel, RPG states: >>The panel provides mid and high frequency diffusion and low frequency absorption.<<

These descriptions seem rather similar to my uninformed eye.

RPG does not advise about listening distances for these devices, but they do say: >>the listener can sit much closer to [BAD panels] without experiencing near field phasing effects.<<

I've read that Prof Erskine recommends BAD panels for first reflection points (with deserving speakers), but I'm wondering if Abfussors are also an option in small rooms or not.
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post #71 of 80 Old 01-07-2009, 01:51 AM
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Yipes-good to know about the Abffusor. I never actually looked that sucker up. I took a trip to RPG for a couple days in Oct '07 I think it was and just parroted what Zjeff told me. I have tended away from QRD type diffusion on small rooms as I don't like the sound, which I am sure is the distance thing. I do wish RPG would publish the diffusion graphs. Whose to say how they fare? I realist that is the question. Maybe with an absorption coefficient above 1 out to at least 4K maybe not a problem.

On the bad panels, I certainly should not have left out the MF part of the frequency range. I have unfortunately adopted a bit of short hand that I believe talking with you will tend to break that habit!

I have been in rooms that utilized QRDs, bare wall, 3 PCF fiberglass, 6pcf fiberglass, BAD panels, Quest PerfSorbers, and Skylines at reflection points. I have able to experience many of those in the same room during the same session and some of them seconds apart. And on more than one ocassion. My preference tends toward the Quest panels and the Bad panels. I will have to arrange to get some abffusors for the next chance.

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post #72 of 80 Old 01-07-2009, 02:05 AM
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On reflection, I believe the differences between the hybrid panels may primarily manifest as the frequency range where the transition occurs from absorption to diffusion.

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post #73 of 80 Old 01-07-2009, 05:05 AM
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Roger...I have a sample here of the Perf-Sorber. I'll PM you with test data.

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post #74 of 80 Old 01-07-2009, 05:52 AM
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On reflection

Is that direct reflection? Diffused reflection? Perhaps partially absorbed diffusion? Or is it just a function of interaural crosscorrelation?

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post #75 of 80 Old 01-07-2009, 09:44 AM
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Quote:
Originally Posted by Dennis Erskine View Post

Is that direct reflection? Diffused reflection? Perhaps partially absorbed diffusion? Or is it just a function of interaural crosscorrelation?

Chuckle - glad you caught that Dennis. I'm going with Spectacular Confusion for the moment. Try this on a iphone with no tactile feeback and a built in word destroyer and as I can see from above my tone has apparently changed to full on brain damage. Not a big stretch from partial, but still! I think the Bell labs boys decided long ago that a little feedback can moderate the distortion so I grabbed a real keyboard to try this again.

I thought about editing my post all the way down to full on removal but it was late so I let it stand, er stay.

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post #76 of 80 Old 01-21-2011, 09:25 AM
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Originally Posted by pmeyer View Post

Ok, big disclaimers:

I'm NOT an expert. Just a dabbler. I have not even treated a single room (although I'm in the middle of doing mine).

My recommendation: go to the "Acoustical Treatement Master Thread"
http://www.avsforum.com/avs-vb/showthread.php?t=255432

It's a huge thread, but if you take your time and read it, you'll get the general idea of what people are doing. If you really care about sound quality, you'll then likely hire Bryan Pape, Terry Montlick, Dennis Erskine, or another professional to do some online consulting. It doesn't cost as much as you might expect.

If you don't want to do that, then you can muddle through and do some basics. Here is a summary I just put together for a friend:

The basics:

1) get absorption on the first reflection points on the floors and walls. This is the spot on the left/right wall where the sound from various front speakers bounces off the wall and hits the listener. The floor is usually handled by carpet, and the ceiling can be done as well, but most people don't for hassle/aesthetic reasons.

With three front speakers and multiple people in the room, it ends up being a range of dots on the side walls. Put carpet on the floor, and put 1" thick fiberglass or cotton panels on the walls to cover those spots. Lots of advice in the thread above on how to frame/cover the panels so they look ok.

The gain from this is better 'localization'. The soundstage of the front speakers sounds accurate (right sounds from the right, middle from the middle, etc.) and not mushed together.

2) cut down on the echo in the room. This is generally referred to as getting the rt60 under control. (RT60 is ~ the time it takes for the sum of all reflections to decline 60dB once the sound source ceases). This is done by covering a certain amount of the walls (often ~50%) with material that will absorb mid-high frequencies. 1" acoustic material is typical. The first reflection point (FRP) absorption above counts towards this coverage. Often, there isn't any special FRP absorption: people just put absorption on the side walls up to and a bit above ear height along the whole side wall. This takes care of 1 and helps with 2.

3) put absorption on the front wall. Pretty much make the front wall dead (2" fiberglass panels). Same with the back wall. The front wall keeps all the surrounds from bouncing back at you. The back wall absorption (typically close to the back of the seats) counts as a 'first reflection point'. I'm doing 2" fiberglass panels across both front and back. (Some folks prefer to keep the back wall reflecting. "Live-end/Dead-end" was apparently a common desire in music rooms. In my HT, with seats 3' from the back wall, I want the back wall dead)

4) Bass traps. Typical room is going to have resonant frequencies (wall to wall, ceiling to floor, diagonal corners, getting more and more complex). At these frequencies you will get standing waves in the room. Those waves will tend to lead to spots in the room where certain frequencies of bass are much stronger than they should be (peaks) and spots where a certain frequency is completely non-existent (nulls). This is bad. At any given spot in the room, instead of a flattish bass frequency response, you'll get these (potentially big) peaks and nulls. This is typically in the 20Hz to 200Hz range.

The problem with these standing waves is that you can't equalize them out if you have more than one listening spot, and maybe not even then. In your seat, you may have a null at a given frequency, but two seats over the same frequency may be a peak. If you raise it up to fix your null, it makes it even worse for the other spot.

Typical thing to do here is to build bass traps in the corners (corners because all standing waves have at least some connection to corners, so you can be most effective there. It's also often the easiest place to get a deep bass trap. A very easy and well reputed DIY trap is the studiotips superchunk (http://forum.studiotips.com/viewtopic.php?t=535). Triangles of fiberglass panels stacked in the corners. There are also panel bass traps you can buy. In general, more bass traps is better.

-----------------------------

So: it's much more complicated than that, but it seems safe to say that if you have:
- carpet of some kind between speakers and front seats.
- front wall dead.
- 1" absorption up to ear level on the side walls.
- Bass traps in the corners

That you will have a better sounding room than if you do nothing at all. Will it sound better (or can you get away with less/different) if you hire a pro? Probably.

Good luck, and remember, this is simply my (imperfect) learnings from reading the master thread. It's worth what you paid for it...

Bump. This thread should be a sticky thread.

I found this thread thanks to BigMouthinDC, who linked to it in another thread.

Sure, I'll wade through the rest of the Acoustical Treatments Master Thread, I've read Everest and Pohlman, and I'm in the middle of Floyd Toole's book, but this overview is just awesome. More people should see it. Thank you.

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post #77 of 80 Old 01-24-2011, 10:00 AM
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I agree, at least it should be added to the The Show Me Thread - All of the "Show Me Your....." threads linked here.
so others can easily find it.

I've also read Everest and Pohlman, not tackled Floyd Toole's book.

As top level/quick 101 this is good start.
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post #78 of 80 Old 01-15-2014, 05:40 PM
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Quote:
Originally Posted by Roger Dressler View Post

I did find something called the HiPer panel from Acoustics First. http://www.acousticsfirst.com/HiPerPanel.htm Anyone know if these are a useful alternative to RPG's BAD?

Has anyone seen or used these things?

http://www.acousticsfirst.com/hiper-panel-flat-panel-diffuser.htm

HiPerPanel_composition2.png

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post #79 of 80 Old 01-16-2014, 05:52 AM
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Perforated panels have been around for a long time and can work well if used in the right places. I would though recommend using something like this with a 4" or thicker backer to absorb below 250hz, which most rooms need the most help below that frequency range (can you say BASS TRAPS? smile.gif) Needless to say this is our design of something close, but there are others on the market and people can also diy something.
http://gikacoustics.com/scatter-plate-product-video/
http://gikacoustics.com/product/gik-acoustics-scatter-plate/

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post #80 of 80 Old 01-16-2014, 05:58 AM
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Ellil.. I have never actually touched one of the panels from Acoustics First but have spoken to them in depth about their panels.. think "perfsorber" (and price)

Although their were some slight differences in the binary pattern the assembly stack up (as described in thier patent) was Very, Very, Very, Very..rolleyes.gif similar to the "Original" Perfsorber that I had purchased.. I say original because I believe what Quest sells now is different from the perfsorber they were selling 4-5 years ago.

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