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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.
kencalgary
rodman99999
6,206 posts
 
What Jax said! If the system/room interface provides you with what sounds like real/satisfying music to YOUR ears; COUNT YOUR BLESSINGS!!
kencalgary OP
45 posts
 
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).
buconero117
2,311 posts
 
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.
shadorne's avatar
shadorne
7,477 posts
 
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.
daverz
487 posts
 
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."
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