How to tell if Acoustic Treatment is Needed?

I have a 12x22x8.5 ft room with the audio on the long wall - for various reasons - facing the listening chair 8.5' away from front of speakers. The soundstage is excellent with the center clean and tight. The ceiling slopes from 7.5' to 9' upwards from speaker wall to wall behind chair. I have no complaints; I think the sound is very good, although with 60 year-old ears and not a lot of experience with high-end audio systems I don't know whether MY budget system can be better.

I do know that there are furnishings in the room that people say do create problems, such as a large glass-fronted picture behind the chair, a coffee table in front of the chair. The speakers are older Mission 762s with front ports and thin cabinets (similar to Harbeth/Spendor BBC style) which sound quite nice. They sit with their back edge about 20" from wall.

My question is: How can one tell - or, what do you listen for - in order to determine if acoustic treatments would improve the sound? For example, I've tried moving the coffee table away from the chair but couldn't determine a change in sound.
Stand in the middle of the room and clap your hands a few times and listen for an echo.....if you have one, then some type of treatment is needed.

This of course is just one way....
I have a room very similar in size/volume to yours. Mine is 12X24 with a ceiling sloping from 7 to 11 feet and a more vaulted ceiling at one end away from the system where the room is wider. Speakers are 8 feet from listening position on the long wall. I think it depends largely on the contents of the room and the room materials and construction, so my room may not resemble yours beyond the surface measurements. I definitely require some treatments as my room is very 'live' with lots of hard surfaces. Just putting a few houseplants in the room helped. When I changed from a fabric to a leather couch that made a huge difference in how the room sounded (fabric was better being much more absorptive). Riley's suggestion definitely would have indicated need for treatment in my room which is much improved with the addition of a few panels, plants and curtains. Still, it does need work. I guess my suggestion to you is this:


I have no complaints; I think the sound is very good although with 60 year-old ears and not a lot of experience with high-end audio systems I don't know whether MY budget system can be better.

It's kind of like going to a group of wine snobs and saying, "I really like this wine - can you tell me why I should not?" There will always be something "better", make no mistake about it. If I did feel the way you do about my room I would probably just enjoy what I had rather than put the effort in. When I've made changes it is because there is something about what I'm hearing that really bugs me and I know I can improve it because I've heard it done. Music is a wonderful thing, and what a privilege it is to have it brought into your home that way.

That said, very easy and basic steps to take that could help a setup like yours (based entirely on my experience): treat the first reflection point (if there is one - this assumes the speakers are at one end of the room). This treatment could be as simple as a large houseplant (diffusion), but is more commonly done by an absorptive panel. Next, by your description your listening position is up against a (back) wall. That wall ideally should have some diffusion panels against it behind your head. You could also try bass traps in the corners of the room behind the speakers (again, this assumes the system is at one end of the room). If the system is centered in a 22 foot room on the long wall you may not have the issues of a first reflection (except on the ceiling) or corners directly behind the speakers (though you may still benefit from bass traps in the room). You are basically listening nearfield and are probably avoiding some of the problems you may have in a larger room.

Good luck, and congratulations on putting together a system you really enjoy.
What Jax said! If the system/room interface provides you with what sounds like real/satisfying music to YOUR ears; COUNT YOUR BLESSINGS!!
Thank you all, very much. I expect that since the speakers are on the long wall I have less of a problem with side reflections but sitting on a couch touching the back wall - even worse with a large picture above the couch - probably introduces some head-on reflections. If it is a problem, what would I be hearing?

I enjoy jazz (e.g., Chet Baker, Dave Brubeck, Patricia Barber), most classical and pop/rock (e.g., Dire Straits, Pink Floyd, Roy Orbison).
Best way is to try some tweaks and see if they improve the sound. First, bring the speakers out from the wall using the 38% rule (see realtraps site for details). Also using the realtraps web site calculate the reflection points and see if they are interfering with room nodes. Yes, any glass is a no-no, as all glass 'rings'. Leave it were it is and put a blanket, or two, over it to see if things improve. Others have also suggested some considerations. Also, check out the Toole book, 'Sound Reproduction', it has tons of information that will help you 'listen'. Use the music that is most familiar, Chet is great listening. Finally, hit the 'pillows', placing them at reflection points to see if improvements result.
If you are indeed sitting with your head against a wall (or within a foot) then you need to change listening position first and foremost. I would recommend a listening position at least 4 feet from a wall. This difference will be huge - the sound should open up and sound less claustrophobic with much more even bass response.
A listening position within a foot of the back wall was one recommended by John Dunlavy if the wall behind the listener is heavily damped. This is from my Dunlavy SC-III manual:

"All of these potential problems [of short wall placement] can be avoided by simply rotating the room layout 90 degrees such the loudspeakers are located along the longest wall of the room with the listener seated adjacent to the opposite wall directly across from the center-point between the speakers. The listening position should be close enough to the back-wall (less than about one foot) to eliminate low-end standing waves between the wall and the listener.

A thick sound-absorbing drape (preferably with a high percentage of sheep's wool) between the listener and the back-wall will further mitigate problems from developing at the low-end of the sound spectrum. (A low cost alternative is to use a 3 to 4 inch thickness of sound-absorbing polyester foam, perhaps 4x6 feet [the accompanying diagram of is labeled ACOUSTICAL FOAM, 4' WIDE, 7' HIGH], affixed to the wall behind an attractive drape, preferably one containing at least some natural wool (which will help to absorb mid and high frequencies). This arrangement provides the most accurate spectral-balance, the smoothest and deepest bass, and most natural imaging and soundstage."
In case you can't help yourself and want to tweak:

Master Set Procedure for speaker set-up.

I haven't tried it yet, but am going to before I start buying/making room treatments.

Supposedly, it works better for a long wall set up like yours. And if done properly, a room shouldn't need treatment. It's free.

cheap place to buy absorption panels and DIY supplies, Corning 703/705, proper cloth:

Diffusion Panels (kinda look like egg carton cardboard material you can paint):

I have an extra box of this stuff, so let me know if you're interested.

Hope this helps.
Great suggestions and resources here for treatment. Ken, I'd have to agree that glass behind your head is a big no-no for optimum sound, but again, if it ain't broke...

That said, yes, get rid of the glass and replace it with some sort of diffusion. I put up some heavy curtains and have a project to build a DIY diffusion panel. The OC 703 panels that are mentioned are absorptive panels and NOT diffusion. In addition to the great resource for the inexpensive covered 703 panels, they are also available from companies that deal in insulation (these are Corning insulation panels made from dense foam). A five pack of 2X4 panels should be a bit over $100, or rather they are in my area. These are normally not the foam carried by Home Depot and other large chains. It is also not good to have glass or hard surfaces in between your speakers on the back wall, and here again a combination of diffusion and bass traps may be the way to go. Absorption can also be used, as on the side walls and ceiling. There are numerous threads and resources for room treatment. I would imagine, given that you are happy with the sound now, and by the fact that you are listening nearfield, that you may find that limiting treatment to only one or two points may make a big difference. It is a great suggestion to experiment before jumping in head first by removing the offending glass and replacing it temporarily with a thick foam cushion or heavy blanket if you can find some way to suspend either behind you. Play some music you are very familiar with before and after and see if the difference that makes is worth the effort and expense.

Again, I would not dwell further on it if you cannot hear a difference, and would go with that great old children's song lyric that I remember from Romper Room ...If you're happy and you know it clap your hands! Hey, was that an echo I heard just then?
No Joke. If you don't have them, you need them. There is no room that couldn't benefit from them.
Shadorne is 100% correct. You should move your listening chair away from the back wall. Try getting about 6 feet away from the speakers. So your ears might be 3 feet from the back wall and the front of the speakers 3 feet from that wall. Give that a try and let us know. It is cheaper than room acoustic treatments I believe.
Definitely try alternative placement ideas before you spend $$$ on the problem. If nothing else, it will help optomize what you already have.

Then get some coush cushions or quilts and oth4er dampening things (borrow some from other audiophiles if you can) and try them around the room. In the corners as bass traps and at the 1st reflection points. If you are like me, they will be revelatory, and then there's no going back.

IMO treating a room is almost always necessary and rarely does harm unless it is overdone (or done improperly).

Shadorne is 100% correct. You should move your listening chair away from the back wall. Try getting about 6 feet away from the speakers. So your ears might be 3 feet from the back wall and the front of the speakers 3 feet from that wall. Give that a try and let us know. It is cheaper than room acoustic treatments I believe.

If you move six feet from your speakers you will also, very likely have to bring the speakers together as well in order to keep the soundstage focused. This, in turn, may also reduce your soundstage and imaging abilities to a smaller space. This is based upon my own experience with various speakers in my own space. I can tell you that in my room of similar proportions, that arrangement also looks pretty ridiculous and closes the room off to a significant degree. You mentioned you have a coffee table which makes this proposition even more challenging. It rates extremely low in the WAF. Hell, I don't even like it, in every way imaginable (visually and acoustically). Diffusion on the back wall is a far more pleasing solution for me. BTW, speaking of the coffee table - you did mention that you'd tried moving it away from the chair. You might try two other things: eliminate the table all together and see what that sounds like. The second is to leave the table in the same place you use it and find the actual reflection points on the table. To do this place a mirror flat on the table surface. Sit in your listening position and move the mirror around the table until you can see the reflection of each speaker in the mirror (two separate spots on the table). As a test, in those spots place a pillow or a small plant or something that my otherwise absorb or diffuse the sound. See if that makes a difference for you.

Keep in mind, that none of this stuff may occur to you to make a difference at all, or perhaps it makes a difference, but one you'd really have to make an effort to hear yourself. There's no doubt the physical changes in the room do make a difference, and that treating a room can have a positive effect. The question really is do you hear it, is it worth it to you, and do you care about the differences it does make. If the answer is no after giving it a try, then keep on enjoying what you have!
i agree that long wall speaker positioning is the way to go (as it greatly ameliorates side wall reflections), but it does create its own problems:
1) bass articulation
2) staging
3) top end extension

IME you cannot overload the room w/ bass traps---put them in the corners to start (lots of DIY solutions for very little money--search Jon Risch). but you've also got to reduce standing waves between the walls that are 12' apart (check for slap echo; if its present, add wall panels--OC 703 is a nice product, put that covered w/ some polyester battling over top on the wall behind your head and see if you notice anything. its a $50 experiment).
Thank you for all the wonderful suggestions and links. With the speakers on the long wall I can't move my seating position or I'll be sitting on top of them, but it is something I will keep in mind for the future should I change the speakers' position. At present I think I'll try some diffusion on the wall behind my head.
What I think you'll need is, absorption on the wall behind your head.
Ken in Calgary - it's Kevin in Toronto here.

Some more thoughts for you:
(1) Get your hearing tested. Men, moreso than women, and especially after 50, lose our hearing quicker. Best to know if or at what frequencies you may be challenged by. If it's mid/high frequencies then all the diffusion and mid/high absorption won't mean a damn thing if you can't hear it to begin with. Sorry for the frankness.
(2) assuming (1) above is fine, in your case the first surface to deal with is the wall behind your head. DO NOT put diffusion there as you need to sit 6-10feet away from diffusion for it to work properly. I have both 1-dimensional GIK D1 diffusers and 2-dimensional Sklyine diffusers and you can sit closer to the 2-D because about half the sound is diffracted horizontally back towards you, but I digress. Instead, put some broadband absorption 4" to 8" thick sold by GIK or RealTraps, which means moving the picture to another wall. If you can't/won't move the picture, then try moving the bottom of the picture out away from the wall by putting a block of wood between the wall and the picture so that sound hitting the picture will be reflected upwards towards your slanted ceiling which will then be reflected down and toward your front wall (behind the speakers) which is fine.
(3) put a blanket overtop of your coffee table or move it during listening sessions so as to prevent high frequency reflections that interfere with the speaker's direct sound.
(4) try diffusion on your front wall behind the speakers.

No side wall treatments needed if your stereo is centered along the long wall.
No ceiling treatment needed unless by using a mirror you can see the tweeters from your listening chair in which case put up some diffusion (1D or 2D) if sufficent distance exists.

Generally speaking, think of your room in frequency bands and treat each one individually.
(A) Bass below the Schoeder frequency which in most rooms is about 300Hz: The clustering of bass nodes are less dense than upper frequencies which causes bass peaks and dips in SPL to be much easier to hear, so evening them out is the goal. Try to minimize the dips as best you can using absorption as the peaks can always be cut in volume with a little parametric EQ. Use 8" or more of absorption (diffusion would require well depths of several feet, clearly not an option) so to the extent you want or need better bass try putting bass traps in a variety of places, play some test tones and using a SPL meter graph the results. This is an iterative and time consuming exercise, so beware.
(B)Mid - Upper frequencies: for music you want to maintain the aliveness of the room to help create the "spaciousness" that is critical. Most domestic rooms are overly damped to begin with (i.e. furniture, draps, carpeting, people, pets etc)so I'd recommend diffusion over mid/high frequency absorption. Other main factors to consider are "timbre" and "location of instruments in space." All three factors will benefit from diffusion BUT only if you're sitting far enough away from it. This is why small room acoustics is so much more challenging than larger rooms due to more constraints. The deeper the well depths of the diffuser the lower the frequency it will work down to. The well depth is half the frequency wavelength distance and may in fact continue to work down one additional octave but less effectively.

So in summary, check your hearing, move the painting and replace it with 4"-8" absorption, move the coffee table or throw a blanket over it and pour yourself a libation. Enjoy and do report back to us how you made out.