Acoustic Treatments and Room Correction

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ajzepp

Acoustic Treatments and Room Correction
« on: 5 Jun 2019, 02:50 am »
I recently turned a room into a theater room, and part of that process was installing about 18 GIK traps, mostly absorbers with few diffusors on the rear wall. My thought process was that improving the room acoustics - especially in a smaller room (13x17) will give the ARC room correction software the best opportunity to do its job.

But then I started thinking about whether this was actually the case (I'm assuming it is, since so far the results are very good, especially in the low end), and whether certain types of treatments are best when there is room correction software involved.

Is a combination of absorption and diffusion going to be the best approach to this? I can't really do much about what I've already added, but I've been planning on adding more diffusion to the rear wall, so wanted to check before I did.

Thanks

ajzepp

Re: Acoustic Treatments and Room Correction
« Reply #1 on: 6 Jun 2019, 12:53 am »
Here is Anthem's response, in case anyone is interested:
 
The less ideal a room is the greater the impact ARC will have. Essentially the closer you get to a perfect room the less ARC will need to correct so having ARC enabled or disabled may not be as noticeable. That being said there may be issues in some rooms that ARC simply can't correct unless they are acoustically treated or speaker positions are changed. /i]

goskers

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Re: Acoustic Treatments and Room Correction
« Reply #2 on: 6 Jun 2019, 05:14 pm »
As a very smart gentleman once told me (Geddes) for an acoustical problem it’s best to find an acoustical solution.  IE, an electrical solution to an acoustics problem will not be as effective a solution.

poseidonsvoice

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Re: Acoustic Treatments and Room Correction
« Reply #3 on: 6 Jun 2019, 05:35 pm »
As a very smart gentleman once told me (Geddes) for an acoustical problem it’s best to find an acoustical solution.  IE, an electrical solution to an acoustics problem will not be as effective a solution.

Yup! What he said!  :rules: :thumb:

Best,
Anand.

Tyson

Re: Acoustic Treatments and Room Correction
« Reply #4 on: 6 Jun 2019, 05:48 pm »
I agree too.  I've used some very sophisticated EQ in the past to try to deal with room issues and I can say with certainty that dealing with acoustic issues in the acoustic realm is by far the best option.

That doesn't mean just throwing up absorbing every where.  That can deaden a room too much, IME.  I recommend absorption at the first reflection points (walls and floor).  Absorption over flat hard surfaces like glass windows (heavy curtains or cloth roman shades work great), and diffusion on the front wall (behind the speakers) and any walls not part of the first reflection point.  That'll get you a really good starting point for great sound in a room.  Not too dead, not too live, and the most important problems fixed. 

Now bass, that's a whole other topic, lol.  It needs to be addressed, too.  EQ "works", but not nearly as well as using OB bass (powered, preferably) or if you can't do OB, then a Swarm approach using 3 to 5 subwoofers distributed semi-randomly around the room is best. 

youngho

Re: Acoustic Treatments and Room Correction
« Reply #5 on: 7 Jun 2019, 12:09 am »
...whether certain types of treatments are best when there is room correction software involved.

Is a combination of absorption and diffusion going to be the best approach to this? I can't really do much about what I've already added, but I've been planning on adding more diffusion to the rear wall, so wanted to check before I did.

This is probably a difficult question to answer, since there are a variety of room correction products available. Probably it would be helpful for you to start by looking at http://www.aes.org/tmpFiles/elib/20190606/17839.pdf, as well as Floyd Toole's book and the accompanying website: https://www.routledgetextbooks.com/textbooks/9781138921368/home-theatre.php

To make it slightly more difficult, there is more than one understanding of what diffusion means in an acoustical sense, as well as varying performance with respect to the frequency spectrum depending on product depth.

The short answer is that absorption and diffusion are probably relatively equivalent (assuming 4-6+" depth for absorption and 6-8"+ depth for diffusion) at primary reflecting points (due to attenuation of reflections when they reach the measuring device), that room correction products are unlikely to take small room reverberation time equivalents into account (where diffusion potentially comes into play), that specific positioning (hence direction of reflections) of specific products (phase coherent versus true diffusion in terms of amplitude and phase) likely matters greatly.

One more resource: https://danylastchild07.files.wordpress.com/2016/05/acoustics-of-small-rooms.pdf

Sorry for any condescension, I won't respond further unless you specifically ask from me,

Young-Ho

ajzepp

Re: Acoustic Treatments and Room Correction
« Reply #6 on: 7 Jun 2019, 12:26 am »
Thanks everyone, this is great info...much appreciated!

JLM

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Re: Acoustic Treatments and Room Correction
« Reply #7 on: 10 Jun 2019, 09:25 am »
First always define the particular problem you're hearing.  In this case measure the room.

For room issues (they all have issues):  top proirity is shape (Fibonacci ratio is perhaps the best), next size (bigger is almost always better), then speaker/listening position setup (don't put a big rack between speakers), then treatment (first reflection point absorption to make the room seem bigger, diffusion can only help above roughly 1100 Hz as limited by length of sound waves, is the ceiling an issue?), and finally as icing on the cake use EQ/DSP (as Geddes says fix acoustic problems with acoustical solutions).

Recommend reading Floyd Toole's "Sound Reproduction" 3rd edition to learn how speakers and rooms work (or don't work) together.  He pushes for the use of monitors and multiple subs.  Toole and Gedde agree on much.

Hipper

Re: Acoustic Treatments and Room Correction
« Reply #8 on: 14 Jun 2019, 12:48 pm »
Treating a home theatre room (with more than two speakers I presume) may be different from treating a stereo set up which is my only experience.

The basic plan is:

1. Position chair and speakers for best sound, especially bass (up to around 300Hz).

2. Use room treatment, particularly bass traps, to control the room effects on the sound.

3. Use DSP/EQ to finish off - to a flat frequency response or whatever curve you want.

To do this in the most informed way you should learn to measure the room, most accurately with a microphone and suitable software (many use the free Room EQ Wizard - REW).

As for what treatment, diffusors or absorbers - or a combination of both, I only use absorbers as I didn't like the effects of diffusors. But that's just me. The issue with diffusors is they need a certain distance between them and the listener to be effective otherwise you can actually hear them.

Reflections are dependent on your speakers sound distribution. If that is narrow you may not get reflections, especially off the ceiling. Ask you speaker designer.

GIK offer free advice, especially as you've already bought some of their products. They also have an audiocircle - https://www.audiocircle.com/index.php?board=183.0    ).

Their website, and that of RealTraps, is full of useful guidance including how to use REW.

ajzepp

Re: Acoustic Treatments and Room Correction
« Reply #9 on: 18 Jun 2019, 04:31 am »
Thanks for all the feedback gentlemen.

I was mainly trying to decide about adding additional treatments, as I'd already put a lot of time and effort into the room, but after further tweaking the ARC software (I didn't realize there were two modes on the new Anthem ARC Genesis program), I'm really happy with the results. I had no idea I'd be able to get this type of low end in a smaller room like this, but it appears the combination of physical panels plus the room correction is quite effective. Pretty dramatic how the room sounded pre-treatment vs now. Spent more than I wanted to, but hard to argue with the results.

Appreciate all the help.

dB Cooper

Re: Acoustic Treatments and Room Correction
« Reply #10 on: 18 Jun 2019, 11:48 am »
The problem with 'room correction' is that it doesn't correct the underlying problem- the actual interaction of the speaker with the room- so by making the sound better 'here', you may make it worse 'there'.

Over 40 years ago, Roy Allison figured out how to get wide band flat power response  throughout a room from one pair of speakers, but today his discoveries seem to have been largely forgotten. Only Larsen (that I am aware of) seems to be working with similar concepts.

Good to see some posts recently about acoustics and room effects though; they can have a profound effect but are often ignored.

JLM

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Re: Acoustic Treatments and Room Correction
« Reply #11 on: 18 Jun 2019, 12:27 pm »
I question the microphone ARC uses.  REW and Dirac recommend a calibrated USB mike, and some even go for a 'highly calibrated version.  My inexpensive Sony 6.1 AVR and DSPeaker Anti-Mode 2.0 Dual Core both used apparently cheap mikes that could be way off. 

Tyson

Re: Acoustic Treatments and Room Correction
« Reply #12 on: 18 Jun 2019, 04:14 pm »
Thanks for all the feedback gentlemen.

I was mainly trying to decide about adding additional treatments, as I'd already put a lot of time and effort into the room, but after further tweaking the ARC software (I didn't realize there were two modes on the new Anthem ARC Genesis program), I'm really happy with the results. I had no idea I'd be able to get this type of low end in a smaller room like this, but it appears the combination of physical panels plus the room correction is quite effective. Pretty dramatic how the room sounded pre-treatment vs now. Spent more than I wanted to, but hard to argue with the results.

Appreciate all the help.

Very true!

rollo

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Re: Acoustic Treatments and Room Correction
« Reply #13 on: 18 Jun 2019, 04:36 pm »
The problem with 'room correction' is that it doesn't correct the underlying problem- the actual interaction of the speaker with the room- so by making the sound better 'here', you may make it worse 'there'.

Over 40 years ago, Roy Allison figured out how to get wide band flat power response  throughout a room from one pair of speakers, but today his discoveries seem to have been largely forgotten. Only Larsen (that I am aware of) seems to be working with similar concepts.

Good to see some posts recently about acoustics and room effects though; they can have a profound effect but are often ignored.

   Gradient as well. Great speaker BTW. 


charles

ajzepp

Re: Acoustic Treatments and Room Correction
« Reply #14 on: 18 Jun 2019, 09:36 pm »
I question the microphone ARC uses.  REW and Dirac recommend a calibrated USB mike, and some even go for a 'highly calibrated version.  My inexpensive Sony 6.1 AVR and DSPeaker Anti-Mode 2.0 Dual Core both used apparently cheap mikes that could be way off.

ARC uses a calibrated mic...comes with the receiver

ajzepp

Re: Acoustic Treatments and Room Correction
« Reply #15 on: 18 Jun 2019, 09:38 pm »
The problem with 'room correction' is that it doesn't correct the underlying problem- the actual interaction of the speaker with the room- so by making the sound better 'here', you may make it worse 'there'.

Over 40 years ago, Roy Allison figured out how to get wide band flat power response  throughout a room from one pair of speakers, but today his discoveries seem to have been largely forgotten. Only Larsen (that I am aware of) seems to be working with similar concepts.

Good to see some posts recently about acoustics and room effects though; they can have a profound effect but are often ignored.

All I can say is that ARC does an incredible job improving the overall intelligibility of dialogue, panning effects, and especially the low end. Trying to manually calibrate nine speakers and two subs sounds like a task I would never want to undertake, so in this case, the software does an amazing job.

JLM

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Re: Acoustic Treatments and Room Correction
« Reply #16 on: 19 Jun 2019, 11:30 am »
Sadly not all calibrated mikes are alike (calibration can vary significantly).

Mike in NC

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Re: Acoustic Treatments and Room Correction
« Reply #17 on: 19 Jun 2019, 10:34 pm »
Sadly not all calibrated mikes are alike (calibration can vary significantly).

Of course not. Arguably the worst was the mic that came with the TacT 2.2X. Fortunately, a compatible third-party mic, with superior calibration, was available.

I know of no reason to think the Anthem mics are less well calibrated than, e.g., a UMIK-1 or similar. After I measured my system with ARC (and the supplied mic), the averaged curve was quite similar to curves from a Dayton OmniMic2. I can't compare them in detail, because the ARC curves are averaged and smoothed, while the Omnimic curves are smoothed (probably differently) but not averaged spatially.

It is a bummer that most systems work with one and only one type of microphone, so cross-comparison is difficult. I currently own four different measurement mics, each compatible with its own system (Anthem, UMIK-1 for Dirac, Omnimic, and mic for JL Audio subs).

Is anyone aware of a re-calibration service that handles Anthem USB mics?

poseidonsvoice

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Re: Acoustic Treatments and Room Correction
« Reply #18 on: 3 Jul 2019, 12:48 pm »
Is anyone aware of a re-calibration service that handles Anthem USB mics?

Try/email Herb Singleton of Cross Spectrum Acoustics.

Best,
Anand.

Mike in NC

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Re: Acoustic Treatments and Room Correction
« Reply #19 on: 3 Jul 2019, 11:14 pm »
Try/email Herb Singleton of Cross Spectrum Acoustics.

Thanks, Anand! I dropped them a message today and hope they can do it, if only to satisfy my curiosity.

P.S.  When I switched to ARC from manual calibration of my 2.2 system, the results improved to a startling degree. That was a surprise, and it's sure more pleasant than adjusting 4 speakers individually with the measure--adjust--remeasure cycle. The only issue I've found with ARC so far is the lack of "knobs" to tweak its midrange results. It has plenty of adjustability on the low and high ends. (My premise is that no automatic system will be exactly right for every listener in every system, so that kind of flexibility would be ideal.) Still, I've been able to get outstanding results by experimenting with measurement layouts until one worked just-right for me.