I have a less than ideal room (an area rug and a couch but almost no other fabric) to which I have added some temporary sound absorption (mostly more area rugs strewn all over the place). All of it is below four feet high though – I have nothing but drywall and artwork above 4 feet. I am much happier now with imaging and tonal balance at low-moderate volume (say 80db or less, although I’m really not sure). Vocals and trumpet in particular seem very realistic, focused, and stable. But it seems to me that as I crank up the volume (still under 100db, but louder) the image and balance break down a little. For example, the vocalist may start to sound more like he or she is singing in an empty gymnasium instead of a concert hall.

Is it normal to lose some imaging and tonal balance due to room acoustics as the volume gets cranked up from say 75 to 85 to 95db? If not, is there a particular room acoustics problem that leads to that issue? Or am I just full of crap? Thanks.

Is it normal to lose some imaging and tonal balance due to room acoustics as the volume gets cranked up from say 75 to 85 to 95db?

Once a room is treated properly it should sound fabulous at all volume levels. If things start to sound irritating at high levels, you need more - and better - treatment. I say "better" because a bunch of rugs is not good acoustic treatment for many reasons.

Or am I just full of crap?

LOL, not at all. Just not an expert yet. :D

See this:

http://www.ethanwiner.com/acoustics.html

If you read this entire article a few times, you will be an expert.

--Ethan

I was lucky enough to run into Ethan's article when I started looking into room treatments. Thanks Ethan. There are others out there, but that is a great place to start.

Kool! Thanks. I saved it to read tonight.

JCarls,

You are just hearing more and better at higher volume. The room is doing exactly the same at low and high volume, as Ethan said. Rooms, amplifiers, and speakers are all linear systems (unless they are busted :) -- rattling cabinet, clipping power amp, etc.). This means that 2x the input gives exactly 2x the output. There is no other change in the sound reaching your ears.

The only exception is at really high volume level -- 130 dB plus. At this level, the air itself becomes non-linear in transmitting sound waves. But your ears will hurt to warn you not to listen at such levels, presuming your system might actually get that loud.

Regards,
Terry

JCarls,

You are just hearing more and better at higher volume. The room is doing exactly the same at low and high volume, as Ethan said. Rooms, amplifiers, and speakers are all linear systems (unless they are busted :) -- rattling cabinet, clipping power amp, etc.). This means that 2x the input gives exactly 2x the output. There is no other change in the sound reaching your ears.

Regards,
Terry



To bad our hearing is not a linear system!

I think that it is true that amplifier voltage gain is linear, but doesn't output power increase with the square of the voltage? Isn't that non-linear?

Likewise are loudspeakers linear? Doesn't it take 10 times the power to double the output?

To bad our hearing is not a linear system!

Well, some of these posts are along the line of what I was wondring - that maybe as certain room reflections went from say 20 db to 30 db, that for one reason or another our brain might perceive a 2x increase instead of a 1.5 increase. But the thread has convnced me that, in any case, I have problems with my room.

BTW, has anyone had great success with temporary put-up-take-down diffusers/absorbers? I'm wondering if maybe I could use the hooks on the wall that hang my pictures/paintings to double as hangers for diffusers/absorbers only when I'm doing serious listening. Or maybe I could construct panels that just lean up against the wall and can be moved to the basement when they're not is use? I apologize if that's in your article Ethan - I have not finished it yet. So far I have only seen the reference to stacking insulation rolls in the corners, which is possible but a lot of work I think.

I think that it is true that amplifier voltage gain is linear, but doesn't output power increase with the square of the voltage? Isn't that non-linear?

Yes. But but both our ears and ordinary microphones don't sense power. They sense pressure, which is linear with voltage.

Likewise are loudspeakers linear? Doesn't it take 10 times the power to double the output?
Ditto for loudspeakers. The pressures they produce are non-linear only when they are broken. :(

- Terry

In a room with lots of reflective surfaces, the sound bounces around the room several times before dying down to below-audible levels. What hits your ear is a combination of the direct sound from the speaker, plus the first reflection, second reflection, all the way up to more than the 20th reflection depending on how reflective the room is. The more you crank up the volume is the longer the reflected sound will take to die down and the more you will hear of the indirect reflections.

Ethan's article is good. Sources I like for affordable acoustic treatment:

GIK Acoustics.
ATS Acoustics (great for a DIY!)

Ethans company RealTraps is in a slightly higher division, starting to compete with companies like Auralex (which has some good recording studio foam that you don't want on your walls, and some nice-looking panels that are really expensive).

In a room with lots of reflective surfaces, the sound bounces around the room several times before dying down to below-audible levels. What hits your ear is a combination of the direct sound from the speaker, plus the first reflection, second reflection, all the way up to more than the 20th reflection depending on how reflective the room is. The more you crank up the volume is the longer the reflected sound will take to die down and the more you will hear of the indirect reflections.

Aaaaaahhhh!!!!!!! I feel like the guy who just got a scientific reason why his $1000 speaker cables sound different than somebody else's cables. Room response could vary with volume... Thanks hdmi4ever!!!!!!

Meanwhile I am exploring every avenue to fix my room.,,

It's not that the room response changes -- your room, as was said, is pretty much a linear system. If you double the input, you get double the response. What's happening is that your ear is nonlinear. Consider that if you keep cutting the volume of a signal in half, you don't always hear the signal half as loud: eventually you hear nothing at all, even if the signal is still there, albeit very low in volume. In the example of the reflections, the key is that after a certain point the reflections become inaudible, or low enough in volume that your ear filters them out. The room is behaving mostly the same, but your ear/brain ignores some of the reflections.

I think the bigger point is that your ear and brain do an enormous amount of filtering on the inputs they receive, and small changes in the relative timings, volume levels, and frequency content of signals (and their reflections, in a room) can alter how and where you perceive the sound as coming from. There's a lot of info out there on psychoacoustics; this Wikipedia article doesn't seem that great but it's a place to start:

http://en.wikipedia.org/wiki/Psychoacoustic_model

I think some of it might be due to background noise. All listening rooms have some noise - it might be the fridge in the next room, or the kids outside playing, or cars driving by, wind through trees, you get the idea. Everytime sound gets reflected its volume is decreased somewhat. When the reflected sounds gets below the noise level, you no longer hear it. When you increase the volume more reflections can be heard over the background noise. Just a thought . . .

And to the OP. Fix your room. Don't forget the first reflection points on the ceiling - treating that made a huge improvement in my room..

Based on the advice I got in this thread, I added three bass traps and a little bit of extra mid-high frequency absorption to my room, and I’m very happy with the SPL meter and listening results thank you. But I did want to mention the fact that the original problem I had (resonances/reverberations in vocals, getting worse as the volume goes up) turned out to be a different issue with a different solution entirely.

I might have been able to fix that problem eventually by room treatments if I was willing to cover 50% of my wall space or whatever, but the simple solution turned out to be moving the speakers to a location only 10” from the back wall. Based on all the reviews I've read over the years, where the first thing the reviewer talks about is placing the speakers 2' to 4' away from the back wall, this was not an obvious solution to me. But I got a 50% or so improvement in vocal clarity and a less forward-sounding image by pushing them closer to the back wall. It’s just something to consider if all the traditional solutions out there don’t seem to be solving your particular problems – the answer isn’t always “more room treatments”, sometimes it’s just moving your speakers around, even in ways that might conflict with the traditional wisdom on placement.

You are right! Moving speakers around can make a huge difference. I think we all assumed that you have already tried tweaking speaker position. Shame on us for not
mentioning this. You might find further improvements by playing with speaker position, and toe in, some more. Just remember, when you move the speakers you also move the first reflection points - usually you want to pick the best speaker position, then tweak the room. Sounds like you are well on your way to making things to your liking - well done.

I prefer speakers right on/in the wall, or, for near-fields, closer to your head than to the wall. If there is some space between speakers and wall, I prefer absorption right behind the speakers, to reduce the inevitable comb filtering and back scattering.
Does your image improve more if you put absorption on the wall right behind the speakers?

I prefer speakers right on/in the wall, or, for near-fields, closer to your head than to the wall. If there is some space between speakers and wall, I prefer absorption right behind the speakers, to reduce the inevitable comb filtering and back scattering.
Does your image improve more if you put absorption on the wall right behind the speakers?

I tried some custom sound absorbing blankets (sold by "audimute") hanging on a frame between the speakers, but not directly behind the speakers. It didn't help. It might be because the blankets are just like 703 fiberglass at 500Hz and above, but they don't do all that well at 250Hz and below. But I think I'll try your suggestion and try it right behind the speakers. I'm not really prepared to sacrifice my living room by mounting 705FRK permanently on the wall though. Next time I buy a house I'm going to look for a listening room that is infinitely flexible that way:).