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Acoustic treatment for my living room

49K views 593 replies 32 participants last post by  Ethan Winer 
#1 ·
This link shows the layout of my living room.



It is an L shape. The living room is opened on the right side to the dining area, with more openings to kitchen and stairs. Ceiling height is about 9 feet. The "hot movie zone
" is within the 16' x 13' area only.


The TV is on the 16' wall.


The round circles denote my Klipsch Synergy speakers in 5.1 + Front Wide DSX setup.


Any good recommendations/tips on acoustic treatment for my living room?
 
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#2 ·

Quote:
Originally Posted by Skylinestar /forum/post/21793380


This link shows the layout of my living room.



It is an L shape. The living room is opened on the right side to the dining area, with more openings to kitchen and stairs. Ceiling height is about 9 feet. The "hot movie zone
" is within the 16' x 13' area only.


The TV is on the 16' wall.


The round circles denote my Klipsch Synergy speakers in 5.1 + Front Wide DSX setup.


Any good recommendations/tips on acoustic treatment for my living room?

I would put panels on the wall behind speakers and on the right wall. Also heavy curtain on large window to the left. I also recommend to move surround back speakers to the back wall.
 
#6 ·

Quote:
Originally Posted by Skylinestar /forum/post/0



nothing wrong. just wanna further improve the acoustic properties of the listening area.

Measure the acoustics of your system first, then figure out what's not optimal, then treat. Do not apply treatment indiscriminately, like people do with a couple of bass traps here a few absorber panels there!
 
#7 ·

Quote:
Originally Posted by Skylinestar /forum/post/21793380


This link shows the layout of my living room.



It is an L shape. The living room is opened on the right side to the dining area, with more openings to kitchen and stairs. Ceiling height is about 9 feet. The "hot movie zone
" is within the 16' x 13' area only.


The TV is on the 16' wall.


The round circles denote my Klipsch Synergy speakers in 5.1 + Front Wide DSX setup.


Any good recommendations/tips on acoustic treatment for my living room?

The two big problems I see are asymmetrical absorption at side and rear, and reflection off the back wall. One source of asymmetry is the window on the left wall, and the other is the dining room at the right rear. The window is potentially the more serious problem.


You don't seem to be saying much about floor covering and window treatments.
 
#9 ·

Quote:
Originally Posted by arnyk /forum/post/21801725


The two big problems I see are asymmetrical absorption at side and rear, and reflection off the back wall. One source of asymmetry is the window on the left wall, and the other is the dining room at the right rear. The window is potentially the more serious problem.


You don't seem to be saying much about floor covering and window treatments.

The floor is concrete flooring white hard shiny tiles. I know it's bad. Without a doubt, a carpet will fix it.


All windows have a layer of thick curtain over them currently.
 
#10 ·

Quote:
Originally Posted by Skylinestar /forum/post/21815643


The floor is concrete flooring white hard shiny tiles. I know it's bad. Without a doubt, a carpet will fix it.


All windows have a layer of thick curtain over them currently.

It turns out that carpeting will soften up the acoustics of that floor, but not in the best way. Carpet provides minimal bass absorption. Wall or ceiling treatments with similar area but greater depth and bass absorption would be better. Of course there are tons of great sounding rooms with carpeting, but if you have the choice of something better, it would be a good way to go.



If the curtains aren't really thick and have deep folds, its acoustical significance is low.
 
#11 ·

Quote:
Originally Posted by arnyk /forum/post/21816433


It turns out that carpeting will soften up the acoustics of that floor, but not in the best way. Carpet provides minimal bass absorption. Wall or ceiling treatments with similar area but greater depth and bass absorption would be better. Of course there are tons of great sounding rooms with carpeting, but if you have the choice of something better, it would be a good way to go.



If the curtains aren't really thick and have deep folds, its acoustical significance is low.

Thanks for the info.


What is better than carpet?

For the wall, treatment will be absorbers on front & side walls, am I correct?

For the ceiling, treatment will be diffusors on the ceiling, am I correct?
 
#12 ·

Quote:
Originally Posted by Skylinestar /forum/post/21816632


Thanks for the info.


What is better than carpet?

Wall or ceiling treatments with a similar surface area but greater depth.


For example, there are ways to make a drop ceiling into a superior replacement for carpeting.


For the wall, treatment will be absorbers on front & side walls, am I correct?

Back before front. Back before sides.

Quote:
For the ceiling, treatment will be diffusors on the ceiling, am I correct?

Absorbers are good. Diffusers break up regular reflections while absorbers make them go away.


On balance, some diffusion is good. Per square foot, diffusiion is almost always far more costly.


Sound treatments are first and foremost about getting a lot of surface area treated.
 
#15 ·

Quote:
Originally Posted by jproy13 /forum/post/21817047


Even if the first point of reflection is probably on the sides? Or was it just for this specific case?

the rear wall is not any more of a priority than other boundaries - any sparse high-gain indirect early signal is going to be destructive. this is determined by speaker radiation pattern, angle of incidence, total flight path, acoustical impedance of boundary, etc.

http://www.avsforum.com/avs-vb/showt...8#post21813228


treatment any/all first reflection points is a blind approach and can quickly lead to a highly damped/dead room. is this a design goal?


you can utilize the Envelope Time Curve (ETC) response to identify boundaries incident of early arriving, high-gain indirect specular reflections ... eg, the ACTUAL high-gain reflection points, vs any and all POSSIBLE reflection points.


the ETC will display how specular energy impedes the listening position - from the direct signal, to early arriving sparse reflections, to the eventual decay of the specular energy until the last of the energy is completely damped. gain with respect to time. it is the time-domain that takes priority with respect to the specular region, NOT the frequency-domain. the frequency response details you absolutely nothing other than the fact that you are seated in an interference pattern due to superposition of direct and indirect signal(s).


carpet will attenuate some HF content, but will not be effective to the lower-mid specular region. if you are using porous absorption to attenuate a high-gain specular reflection, then the absorber needs to be effective down to the Schroeder cut-off frequency/transition region (typically 250-300hz in smaller rooms; based on room dimensions). thin absorption will merely attenuate the HF band and allow the lower-mid band to persist - which will filter/EQ/color the reflection which will then superpose with the direct signal at the listening position. the lower frequencies are going to be more off-axis with typical speaker designs, and they also contain longer wavelengths with inherently more energy content. so the absorber's design must be with respect to effectively attenuating the lower-mid specular band.



Toole: the AES paper: Loudspeakers and rooms for sound reproduction" section 7.1.2 Attenuating, Reflecting, and Scattering Indirect Sounds

JAES vol.54No6 June 2006


Quote:
Originally Posted by Toole /forum/post/0


Although reflections appear not to be great problems, it

is reasonable to think that there must be a level above

which the good attributes are diminished and negative attributes

grow. Obviously an empty room is not a comfortable

listening environment, even for conversation. The

furnishings and paraphernalia of life tend to bring normal

living spaces into familiar acoustical territory. Custom listening

spaces need to be treated. In all rooms absorption,

scattering or diffusion, and reflection occur, and devices to

encourage each are commonly used by acousticians.


It appears that much of what we perceive in terms of

sound quality can be predicted by the anechoic characterization

of loudspeakers. Because most of these data pertain

to sounds that reach listeners by indirect paths, it is proper

to suggest that nothing in those indirect sound paths

should alter the spectral balance.
For example, a 1-inch

(25.4-mm) layer of fiberglass board at the point of a strong

first reflection is effective at removing sound energy

above about 1 kHz. From the perspective of the loudspeaker,

the off-axis response of the tweeter has just been

greatly attenuated—it will sound duller and less good.
Obviously if the purpose of the absorbing material is to

attenuate the reflection, the material should be equally effective at all frequencies.



Given the duplex nature of

sound fields in small rooms, it seems reasonable to expect

similar performance at all frequencies above the transition

region.

In their examination of the audibility of reflections, Olive

and Toole looked at detection thresholds as high frequencies

were progressively eliminated from the reflected

sounds, as they might be by frequency-selective absorbers.

They found that only small to moderate threshold elevations

occurred for low-pass filter cutoff frequencies down

to about 500 Hz, where the investigation ended. Removing

the high frequencies alone is not sufficient to prevent audible

effects [32].


Finally there are the indications that the precedence effect

is maximally effective when the spectra of the direct

and reflected sounds are similar [4], [18], [20]. If the spectrum

of a reflection is different from that of the direct

sound, the probability that it will be heard as a separate

spatial event is increased—not a good thing.
Quote:
Originally Posted by Toole /forum/post/0


Thus from the perspectives of maintaining the excellence

in sound quality of good loudspeakers, rendering an

unwanted reflection inaudible, and preserving the effectiveness

of the precedence effect, there are reasons not to

alter the spectrum of reflected sounds. One is free to redirect

them with reflectors or diffusers, or to absorb them

with lossy acoustical devices, but in each case, the process

should not alter the spectrum of the sound above some

frequency toward the lower side of the transition region in

a small room.
It seems reasonable to propose, therefore,

that all acoustical devices used in listening rooms—

reflectors, diffusers, and absorbers—should be uniformly

effective above about 200 Hz. For resistive absorbers this

means thicknesses of 3 inches (76 mm) or more.

...and the 4" absorber with a 4" air-gap is based on updated gas-flow-resistivity figures calculated using the Delaney, Bazely, and Miki models (and subsequent modifications, as they satisfy all of the various mods to it) - based on the ACTUAL values for the recommended fiberglass and rockwool porous materials.
 
#16 ·
Well, first, thank you for your post.


Second, I understood about 60% of the article (laugh if you want but I'd rather admit this than say I understood fully and stick my foot in my mouth along the line
) This is a totally new area to me.


Third, this blows because the material I bought is 2" thick. I bought some of that compressed polyester fiber sheets. And even though they turn out to be useless, I may have to hang them anyway as it took me lot of convincing to get there.


Fourth, it blows more because as supportive as my wife is about my hobby, which she enjoys immensely as well, she will not be supportive of me hanging anything thicker than 2" on our wall, let alone ceiling.


Fifth, is it worth for me to hang them at all? and if so, according to your link from dragonfyr, the ceiling should be first?


lastly, these questions are not meant to steal the OP's thread, the OP could probably use this info as well I hope.


cheers
 
#17 ·

Quote:
Originally Posted by Nyal Mellor /forum/post/21801110


Measure the acoustics of your system first, then figure out what's not optimal, then treat. Do not apply treatment indiscriminately, like people do with a couple of bass traps here a few absorber panels there!

Any tips for that? Currently I have a RS SPL meter. I do have a notebook with Line-In connection with REW software loaded. How do I test the acoustic and what should I look for?
 
#18 ·

Quote:
Originally Posted by ap1 /forum/post/21793846


I would put panels on the wall behind speakers and on the right wall. Also heavy curtain on large window to the left. I also recommend to move surround back speakers to the back wall.
Quote:
Originally Posted by arnyk /forum/post/21816707


Back before front. Back before sides.

Treatment for front or side, which is of higher priority?
 
#19 ·

Quote:
Originally Posted by Skylinestar /forum/post/21846875


Any tips for that? Currently I have a RS SPL meter. I do have a notebook with Line-In connection with REW software loaded. How do I test the acoustic and what should I look for?

the SPL meter is used for relative gain settings - but for full band measurements/sweeps you will want to utilize a mic that is sufficiently flat across the freq range.


something like this:
http://www.parts-express.com/pe/show...number=390-801


and you can get the cal file here;
http://www.daytonaudio.com/index.php...icrophone.html


this will work for a USB sound-card + pre-amp:
http://www.bhphotovideo.com/c/produc..._Dual_Pre.html


the relevant acoustical measurements are:
  • waterfall plot for the modal region (0-300hz, depending on room dimensions). this will show frequency response of the modal region as well as the LF decay times (how long it takes for the energy to be completely damped).
  • the Envelope Time Curve is for the specular region. this will detail to you how specular energy impedes the listening position (in the time-domain). Gain with respect to Time. from the direct sound (straight vector from speaker to mic, so it should arrive first), to the early arriving high-gain reflections, to the later-arriving reflections, and finally the specular room decay until all of the energy has been damped. specular energy can be modeled like light (angle of incidence == angle of reflection) - like billiard balls bouncing around a pool table. using the ETC you can identify boundaries incident of high-gain early arriving indirect reflections that arrive at the listening position to superpose with the direct signal causing the frequency-response anomaly referred to as comb-filtering.


in this very simplified lab experiment, you can see the correlation between the time-domain (left) and frequency-domain (right).

to start, the reflections from all of the room's boundaries combine with the direct signal at the listening position destructively and constructively - to what is known as a comb-filter interference pattern.




on the left (ETC), you can see the direct signal arriving first, and then high-gain reflections from the room's boundaries. they arrive later in time (X-axis), as they take longer flight paths (and the speed of sound is a constant in your room). the Y-axis is the gain of the signal.


the diagram illustrates how high-gain indirect reflections are attenuated (in this case, Absorbed), which REDUCES the interference at the listening position in the frequency response (graph on the right).


again, this is a very simplified diagram to show the correlation - it is not guidance as to how to treat your room. that is your own decision based on the response you wish to achieve



the ETC details to you how the energy impedes the listening position. the longer the flight path (reflection path), the later it will arrive in time. to simplify even further, think of a loud impulse like a gun-shot or a balloon popping. the direct signal arrives first (shortest path), then the reflections, and eventually the burst of energy is completely decayed/damped within the room.
 
#21 ·

Quote:
Originally Posted by arnyk /forum/post/21847165


Sides first.


There's a school of thought that says that acoustic treatment on the front, behind the speakers, may even be detrimental.

...
http://www.avsforum.com/avs-vb/showt...8#post21813228
http://www.avsforum.com/avs-vb/showp...7&postcount=11


there is no "priority"...and there is no discussion of what to treat unless measurements are taken to determine how specular energy impedes the listening position - and the boundaries identified that are incident of such high-gain indirect energy.


otherwise, you're just placing 'treatment' blindly (what problem is the 'treatment' treating?)
 
#22 ·

Quote:
Originally Posted by Skylinestar /forum/post/0



Any tips for that? Currently I have a RS SPL meter. I do have a notebook with Line-In connection with REW software loaded. How do I test the acoustic and what should I look for?

See this article to get you started http://www.realtraps.com/art_measuring.htm
 
#23 ·
Just finished reading "LoudspeakersandRoomsPt1.pdf" and "UnderstandingRoomAcousticsAndSpeakerPlacement.pdf" (written by Floyd E. Toole, Vice President Acoustical Engineering, Harman International).


In slide 43 and 44 (Page9/15) of the "LoudspeakersandRoomsPt1.pdf" and the other pdf, the figure shows a square room, with speakers placed diagonally. In my opinion, diagonal placement is only possible on square room.


Isn't square room the worst room of all? Does diagonal placement fixes this issue? It does mention that the bothersome side-wall reflections go away.


I'm asking this because currently, I do have another small room with dimensions of about 11ft W x 11ft D x 9ft H. This is almost a cube, which based on my previous readings and knowledge, the worst room of all. However, this is a closed/sealed room, which should be good for my subwoofer to pressurize the air in it. The FV15HP will definitely work better in 14Hz mode in that small room. Besides that, being a closed room, it is quieter than my opened living room. This should allow me to hear all the quieter scenes in movie better. The movie volume will not bother my other family members too, which is good.


Will it be worth to shift all my gears into that room? Is that Harman white paper slide trustworthy?
 
#25 ·
If I could hijack for just a moment to ask a question - the point of (minor) concern in my room is at left side wall reflection point. I have a few Asian carpets of varying size that I was planning to put on this wall, will this suffice in place of more professional panels?
 
#26 ·

Quote:
Originally Posted by Nethawk /forum/post/21854028


If I could hijack for just a moment to ask a question - the point of (minor) concern in my room is at left side wall reflection point. I have a few Asian carpets of varying size that I was planning to put on this wall, will this suffice in place of more professional panels?

Not a good idea. A thin "panel" like that will be like an EQ which will filter out the high frequencies of your speakers. This is on top of viability of any form of absorption on that wall. If you have a few hours, read through this thread (close your eyes on the personal jabs
), to see merits of some of the advice given: http://www.avsforum.com/avs-vb/showthread.php?t=1401704
 
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