# Acoustics advice for room design



## Serenity Now (Mar 28, 2014)

Hi all,

I am currently designing a basement 2ch listening space that will double as my 7.2ch home Theater. I say listening space first, as I know music can be less forgiving than movies when it comes to sound. Anyway, I am looking to double check my work before I commit to this layout. :scratch:

Here are the approx finished room with measurements. It is 15x23x8. The room will be wood framed and 5/8 drywalled, with thick carpet and underlay. Ceiling will be insulated with roxul.


[img]http://i1298.photobucket.com/albums/ag47/Hellcommute/Top_View_zps3213759e.png[/img]

































The first reflection points will be 4" safe and sound panels. The panels beside the seating will be poly diffusers (several per panel at staggered sizes). The rear panel will be another absorber opposite the room exit, an open archway. Behind the AT screen is a large poly diffuser flanked by 2 small absorbers. There are room height bass traps in each of the front corners planned as well. There is a large media shelf planned for Behind the seating location.


[img]http://i1298.photobucket.com/albums/ag47/Hellcommute/Top_View_Rendered_zps7800e2c1.png[/img]




































Any input on how I should change things up? I am trying to get my layout pinned down so I can plan the lighting locations. There will be wall sconces located mid panel at each location. Thanks in advance!!


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## ajinfla (May 10, 2009)

Serenity Now said:


> I say listening space first, as I know music can be less forgiving than movies when it comes to sound.


Hi Serenity, somewhat true, but it also depends on _your_ preferences. What type of music do you prefer..and what do you want it to sound like? If that preference is towards electronic, studio stereo constructs, where your acoustic memory might be based on listening to other speakers, or a "live" concert sound would emanate from a stack of speakers and amplification, then you're probably on the right path.
If however, your acoustic memory contains many performances of unamplified instruments, from concert halls, small jazz clubs, etc. then you might want to completely reconsider.
Read this and ask questions regarding your beliefs and what you think you know about acoustics and your plan.



Serenity Now said:


> The first reflection points will be 4" safe and sound panels. The panels beside the seating will be poly diffusers (several per panel at staggered sizes). The rear panel will be another absorber opposite the room exit, an open archway. Behind the AT screen is a large poly diffuser flanked by 2 small absorbers. There are room height bass traps in each of the front corners planned as well. There is a large media shelf planned for Behind the seating location.
> 
> Any input on how I should change things up?


That would depend on what speakers you have and as previously mentioned, what type of sound you want. It will definitely look fashionable. Do you have perceptual/listening impressions and measurements of the room prior to all that planned stuff? 
If not, what is the basis of the plan?

cheers


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## Serenity Now (Mar 28, 2014)

Hi AJ, thanks for the reply and the helpful article. I have also read a couple of Everest's "Master" books and think I have a rough understanding of the hows and whys.  Lot to digest....

I hope I answer some of your queries:

I guess what I mean by music being the biggest factor for me is that I tend to notice issues more readily becaue of my familiarity with the music. Ie. standing waves etc. easily picked out in a familiar song. This is tougher for me to pinpoint with movie soundtracks I find.

I have experience with treating my past room and have listened with and without absorbers. I had front corner traps, and first and second reflections controlled by 4" traps. The sound was pleasing and I liked how the clarity improved. Bass was also improved in the aspect of tightness and perceived impact during movies. I definitely preferred the room more with absorbtion at the side locations than without.

One drawback I noticed was that some of the "live" energy of the music was taken away and the room felt small. In my new room I would like to preserve the clarity I had in the old room, but make the room feel larger and less narrowed.

I wish to explore the use of diffusion in this space. I want the best of both worlds when it comes to a controlled, image specific, direct sound-- while keeping the room from feeling small and dead. A PM I received from a member here suggested QRDs at the first reflection points with absorbers beside the listening area to draw down the RT60 time. Then diffusion at the rear of the room. This makes sense to me from my reading but I have yet to play with diffusion.

I intend to make the panels all the same dimensions so that each location can be changed to something else at a later time if required. They will be 6' x 6' with columns in between when finished.

Any input on the poly at the front of the room? My intended use here is to make the front soundstage feel wider to add an acoustic artifice to the image while watching movies.

Thanks again!


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## ajinfla (May 10, 2009)

Serenity Now said:


> Hi AJ, thanks for the reply and the helpful article. I have also read a couple of Everest's "Master" books and think I have a rough understanding of the hows and whys.  Lot to digest....


Well, what I linked has to do with _psycho-acoustics/perception, ie. what we actually hear_ (with ears), especially in home A/V environments....vs "Acoustics", which often leads on great ideas of "how to build a recording studio or at least something that looks like one". 
Not the same. A very good book that explains why, is Floyd Tooles "Sound *Re*production". 
To quote his protege, Dr. Sean Olive (Director Acoustic Research Harman Intl):



> *Q:* Spend less on speakers, more on acoustic treatment?
> 
> *A:* _You got the title backwards. It should read: Spend MORE on speakers, and LESS on Acoustical Treatment"
> Turning bad loudspeaker sound into HEAT [through absorption] is passe, a waste of energy, and environmentally irresponsible in 2010. Instead buy a good speaker so you need less treatment. Carpet, furniture and bookshelves (make sure a copy of Floyd Toole's "Sound Reproduction in on it after you read it] will take care of the rest. - Sean_





Serenity Now said:


> I hope I answer some of your queries:


Unfortunately, you missed 2 critical ones. What speakers and what music/memory/preference.
Though you may have answered inadvertently below.



Serenity Now said:


> I have experience with treating my past room and have listened with and without absorbers. I had front corner traps, and first and second reflections controlled by 4" traps. The sound was pleasing and I liked how the clarity improved. Bass was also improved in the aspect of tightness and perceived impact during movies. I definitely preferred the room more with absorbtion at the side locations than without.
> One drawback I noticed was that some of the "live" energy of the music was taken away and the room felt small. In my new room I would like to preserve the clarity I had in the old room, but make the room feel larger and less narrowed.


With good speakers (smooth, controlled polar response), _both_ clarity and spaciousness are enhanced by lateral reflections (to human ears). The entire front of room would be free of "treatments"...not to mention huge reflective objects! (Like mixing consoles, he-man equipment stands/audiophile shrines, mega TVs, etc.). Then of course, there is preference...and sighted expectations.



Serenity Now said:


> I wish to explore the use of diffusion in this space. I want the best of both worlds when it comes to a controlled, image specific, direct sound-- while keeping the room from feeling small and dead. A PM I received from a member here suggested QRDs at the first reflection points with absorbers beside the listening area to draw down the RT60 time. Then diffusion at the rear of the room. This makes sense to me from my reading but I have yet to play with diffusion.
> 
> I intend to make the panels all the same dimensions so that each location can be changed to something else at a later time if required. They will be 6' x 6' with columns in between when finished.
> 
> ...


Inevitably you will do what suits you best. 
My advice, out in the open for all to see are critique/discuss, would be this insane idea: 
Furnish the room. Sofas, carpets, etc. Place your (good?) speakers (roughly) where they are diagrammed. Listen. With your ears. Before making a single measurement, or placing a single "treatment" (even diffusion). 
If it sounds like the semblance of a concert hall or jazz club in your memory banks(?), you're all set. If it's missing the artificial pinpoint studio stereo construct imaging you might instead desire, start treating. Keep in mind that multiple subs *and EQ* (<500hz) can smooth the bass, without killing the sound.
Good luck.

cheers


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## Serenity Now (Mar 28, 2014)

ajinfla said:


> Inevitably you will do what suits you best.
> My advice, out in the open for all to see are critique/discuss, would be this insane idea:
> Furnish the room. Sofas, carpets, etc. Place your (good?) speakers (roughly) where they are diagrammed. Listen. With your ears. Before making a single measurement, or placing a single "treatment" (even diffusion).
> If it sounds like the semblance of a concert hall or jazz club in your memory banks(?), you're all set. If it's missing the artificial pinpoint studio stereo construct imaging you might instead desire, start treating. Keep in mind that multiple subs *and EQ* (<500hz) can smooth the bass, without killing the sound.
> ...



Indeed this is the best advice. I have no idea how to predict room response before construction. But post construction I will have some definitive baseline to work from. 

I am definitely on board with the listen first, decide later method.

The speakers will be Mordaunt Short Mezzo 6 for mains. Mezzo 5 for center, Mezzo 2 surrounds, Mezzo 6 for rear surrounds. There will be 2 SVS SB12-NSD subs up front at 1/4 in from room sides.

My music preferences are accuracy before anything else. I am kind of a chameloeon when it comes to taste. Jazz to Classical to 80s Synth to Grunge. I want a room that plays the recording as is, without adding it's own ambiance or reverb. When I gave away my panels to prepare for the move, I ended up packing up the works a week later. I hated the room sound with the room treatments gone. The room's dynamics were lost, as one note or beat bled into the next.

This probably means I would tend to like an engineered sound VS a live space sound. I do like to hear the pinpoint location of sounds within the soundstage.

So long as the proposed locations for the panels aren't in dispute (regardless as to what lives behind the fabric in the end, if anything) I should be good to go so far as lighting layout goes.

I will hold off on building a monster poly for the front wall until I have spent some time in the space first. Would be cool though. :bigsmile:

Thanks a lot for your advice. I can't believe people like you give your time at no cost to punters like me! :T

Great resource to have.


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## phazewolf (Feb 5, 2012)

If I recall correctly people says in regards to RT60 that you want the room more lively for music and more dead for movies so sometimes it can be hard to balance the 2 uses of a given room.


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## ajinfla (May 10, 2009)

Serenity Now said:


> Indeed this is the best advice. I have no idea how to predict room response before construction. But post construction I will have some definitive baseline to work from.
> I am definitely on board with the listen first, decide later method.
> 
> The speakers will be Mordaunt Short Mezzo 6 for mains.
> ...


Well, our ears tend to adapt to sounds, so I'm not surprised by what you experienced above. The question is, did you try moving the speakers around (after removing the treatments)? I notice in your (new) diagram that the mains (L&R) are positioned quite close to the front (facing) wall. Obviously you want to save space by not moving the false "wall" out to far, but position will have a profound effect on the spatial reproduction, especially with speakers like yours. Unfortunately, those fall into Seans (and mine) "bad" speaker category. Now you can dismiss that as, hey, 2 speaker manufacturers want to sell me something. But that would also dismiss the mountain of perceptual research done by and also referenced by Toole et al. On the same token, "treatments" are generally not given away by charities. And there is *zero* perceptual blind studies done by home reproduction "treatment" proponents....for good reason . What is your estimated cost for the proposed "treatments"?
Here is your Mezzo 6 mains (top graph) averaged over a 15 degree frontal "cone" (_far_ too narrow, but still telling).










And same 15 degree cone with a "good" (controlled off axis) type speaker:










See the difference? It would be progressively more obvious further off axis...and more informative, since we hear, cumulatively, the sum of all the off axes, along with the "direct" sound.
They would sound markedly worse (to ears) with sidewall, etc "treatment". Yours, might sound (as you found) markedly "less worse" _with_ "treatment", due entirely to the poor off axis, _not_ because sidewall reflections are "bad".
I strongly doubt you will be able to get your cake and eat it too (as is), but preferences vary and maybe with just the right positioning....



Serenity Now said:


> This probably means I would tend to like an engineered sound VS a live space sound. I do like to hear the pinpoint location of sounds within the soundstage.


Most do. It is exceedingly rare for anyone to request other than electronic studio constructs at audio shows.
Go with what you prefer!



Serenity Now said:


> So long as the proposed locations for the panels aren't in dispute (regardless as to what lives behind the fabric in the end, if anything) I should be good to go so far as lighting layout goes.
> 
> I will hold off on building a monster poly for the front wall until I have spent some time in the space first. Would be cool though. :bigsmile:
> 
> ...


Regarding layout, the one thing I would suggest (again), is moving the mains forward, so that they are on the same "arc" from the centered LP, as the center channel speaker is (which should put them slightly further out than screen). Then angle the "false wall" faces (parallel to the face of speaker) in to meet the sides of the screen.
Ideal spatial reproduction would eliminate that wall and have the screen further back, but aesthetic considerations may trump that.

cheers


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## Serenity Now (Mar 28, 2014)

Hey AJ, once again, thanks.

The false wall has to stay. There will be people using the room when I'm not around including their little ones and I want to keep as much as I can out of the path of curious hands.  Looks cleaner this way too I think.

The budget for treatments will be based on how much I spend on the rest of the build. Most likely, I will have to go the DIY route for some. Luckily, absorbers are relatively easy to make. Diffusion will likely be purchased if I go that route.

I have adjusted the room to account for the center VS mains listening arch you mentioned (I should have thought of that!) and made alterations to the false wall setup. The whole facade moves up 12" and the screen stays put. This yeilds a L/R position advance of approx 8". If I needed to exagerate the arch more, I will move the center channel back slightly. Here is the new top view:

[img]http://i1298.photobucket.com/albums/ag47/Hellcommute/Basement_Mockup_False_Wall_AT_4_Feet_Top_zps92786d30.png[/img]




































I kind of likethe result in the rendered view. The advantage here is also that the screen to ceiling glare could be reduced slightly because of the arch bumped ahead.

[img]http://i1298.photobucket.com/albums/ag47/Hellcommute/Basement_Mockup_False_Wall_AT_4_Feet_zps273a1352.png[/img]


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## phazewolf (Feb 5, 2012)

So have you tried anything with the room yet or made any progress? Would love to hear how it came out and what you ended up doing with it.


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## Serenity Now (Mar 28, 2014)

The room has not yet taken form. The space in still being planned and building should start in a couple of months. I'll update for sure once I get rolling.


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