Note that I do not use and have never used "bass traps" composed of large piles of fiberglass or other material. This would be impractical in small rooms like mine since it takes up so much space, even if I weren't concerned about carcinogenic fibers in the air, which I am.
And, frankly, electronic EQ works just dandy in the lower frequencies for removing bass resonances you might hear at the listening position. You don't need stacks of absorbing material.
If you are concerned about hearing uneven bass elsewhere in the room, you might be a candidate for using dipole bass speakers. Even in the bass pig concrete bunker basement room I had in my prior home, when I used electronic EQ to remove the bass peaks audible at the listening position, with dipole bass speakers the bass was quite even sounding even in room corners and along the walls behind the speakers and behind the listener, the usual trouble spots.
While I don't quite agree with some that you can almost never have enough high frequency absorption in your listening room, most people will be surprised how much absorption it takes to reduce slap echo audible from the listening position to near inaudibility.
I've mentioned this
clap track test before, but this CD is worth buying just for that one track. Listen to how it sounds over headphones--most any headphones will do. You will only hear a sharp transient that sounds like a handclap, but with absolutely no decay following the initial transient. Listen to it on repeat until you understand what I'm saying and recognize what it sounds like not to have any trailing echo.
Now try to place absorption in your room so that, when played at a healthy level, that track when played through your speakers and listened to from the listening position sounds as close as possible to the way it sounds through headphones in terms of only being an initial sharp transient with no trailing echo. As I said, you may be amazed at how much absorption is required to pass this test. And it doesn't take Golden Ears to hear the difference between the headphone sound and the speaker sound. It will be pretty obvious until you get enough absorption in the room.
Once you have enough absorption in your room to pass that clap track test, you can go further, and add yet more absorption. If you do, however, the room may begin to make conversation in the room sound what I feel is unnaturally and annoyingly dull and damped.
Some serious music listeners aparently don't mind this and, technically, it is correct that in a listening room you really shouldn't be hearing any reverb from your listening room at all. All the ambiance you hear from your listening position should be from the recordings and absorption added to your room will increase the audibility of that rather than decrease it. But many recordings don't have sufficient recorded original venue sound, so they may sound a bit or more dry. Since there are no recording standards, you have to decide what sounds best to you.
I tend to not add additional absorption after the reproduction passes the clap track test--when the speaker sound is very close to the headphone sound of the clap track. At that point, conversation in the room still does not sound like it has a blanket over it.
I should add that you should expect the
subjective SPL at the listening position for any given setting of your volume control to decrease at least a bit if you add enough absorption to pass the clap track test. Especially in small rooms such as I use, much of the sound you hear is from sound reflecting off room surfaces and once you significantly reduce the mid- and high-frequency reflections, the SPL you hear at the listening position decreases, at least subjectively. This is especially true of wide dispersion speakers like the AR-303a. Without adding acoustic absorption to the room surfaces, much of the sound you hear from the listening position will first reflect off room surfaces. If you reduce that refection significantly, it makes sense that the sound you hear from the listening position will decrease somewhat in subjective SPL.
This change is only subjective, however. I did experiments
where I measured pink noise from the Stereophile Test CD2 using the Audio Tools analog SPL meter on my iPhone. I set the volume control at the same minus 30 dB level on the Lyngdorf TDAI-3400 in both rooms and got about the same measured level in each room with the iPhone held at ear level a few inches in front of my face, about 65 dB. I also tried the same thing with some random program on MPR playing renaissance music and got basically the same results.
When I turn up the volume another 10 dB to minus 20 dB, it still measures about the same SPL in both rooms but at that higher SPL the unpadded room definitely sounds louder. Perhaps my ears are just defending themselves more in the unpadded room and that is what I'm reacting to.
Alternatively, it has been suggested to me that I should I think of this subjective effect in terms of Matt Mayfield’s famous video about the Loudness War.
.
Increased reflections are analogous to the compression and turning the volume back up that Mayfield describes.
Decreased reflections are analogous to restored dynamic range. With absorptive room treatment I want to turn the volume up. The music is both louder and softer and simultaneously sounds so much better.
Playing louder in an acoustically treated room feels the same in terms of loudness/comfort level as playing the music at lower SPL in an untreated room.
Whether YOU need to increase the volume in an acoustically damped room and thus need significantly more amplifier power to do that will somewhat depend on your reaction to the ways the sound is "better" with the absorption if you don't change the volume. You may not feel then need or even desire to turn up the volume. But I WILL say that once you are not hearing a lot of obnoxious early-arriving slap echo, turning up the volume control can be even more rewarding than before because you aren't simultaneously turning up the "room roar" from reflections.
