Part way through acoustic panel setup - some Q's

[AbMagFab]

Okay, I'm part way through my acoustic panel setup. I've got both side walls done, and part of the back wall. I need to add one more 4" panel to the back wall, corner bass traps, and kill the screen wall.

I have a couple of pieces I like to use to test the acoustics of the room, mostly just how it sounds to me.

I am pleased with the improvement so far. It's not as incredibly dramatic as I was expecting, but it's noticable (this might be partly because I upgraded my speakers and within a month have put these panels up, so I probably didn't get totally used to the speakers yet).

Anyway, I don't know the proper terminology, but the sounds seems wider (wider than my room actually), and much less muddy, and I almost never find myself thinking it's shrill on the high end.

So my questions:

1) During some piano scenes (example is the moonlight sonata in Immortal Beloved), there's one note he hits a few times that swells a little too much in my head. I checked with a SPL, and it's not noticably louder. So is this an acoustic issue, or is it just my head? I've moved around and I get the same sense, that it almost drowns out everything else for a 1/2 second.

2) My sub is actually doing quite well even without corner traps. I have the Audyssey in my 905, as well as an SMS-1, and I get very even response all around my seating area. I think I'm able to have my fronts and sub balance each other in such a way that it's kind of working now.

Given that the sub seems good, which is more important - killing the screen wall, corner traps, or doing 3 panels on the ceiling? I'd really like to kill this piano swell if it's an acoustic issue, but I have no idea what would be the best place to do it.

3) Why is killing the screen wall a good idea? Aside from bass, I figured nothing is really hitting that wall? Should I be using 2" or 4" panels? And should I put something behind the screen, or just around it?

Thanks in advance for any advice! I'll post pictures later.
-Mark

 

[bpape]

Adding broadband bass control will actually give you MORE bass and lower midrange thereby better balancing the room from a decay time standpoint. That single note may just happen to be falling where you have a peak in the speaker response coupled with an unwanted reflection causing a peak.

The front wall deals with 2 different issues.

- SBIR, the sawtooth response caused by the spherical wavefront from the bass and lower mids coming off the front wall and blending in with the main direct signal - some in phase (peak), some out of phase (dip).

- Killing all reflections from the surround channels from bouncing off the front wall and mixing with the front soundstage and confusing/masking it.

As for dynamics, that's more a matter of

- Capability of the amp/speaker combination to provide quick, controlled volume changes.

- Having a very quiet, well isolated room to start with that has a very low ambient noise floor. People often ignore room isolation as they only consider the 'sound getting out' part and completely forget about the 'sound getting IN' part which raises the ambient noise floor and masks low level details and hinders overall dynamic range potential.

If a system can put out 100db peaks and the ambient noise floor in the room is say 50db, the MOST you'll ever get out of it is 50db dynamic range. Now, if you can lower the ambient noise floor in the room to say 35db, then the same system (100db peaks) is now capable of 65db of dynamic range.

Bryan

 

[AbMagFab]

Thanks for the response. I actually took today off, so I decided to make the screen wall panels. They're all done now, just waiting for them to dry.

I did 4" panels to the right/left of the screen, and 2" panels below the screen.

My room was designed to be silent, it's got an ambient noise well below 20db (which is the noise my projector makes). Without the projector, I can't get the SPL to pick up anything except my breathing (for normal equipment - PS3, XB360 obviously add a lot of anbient noise, but my Anthem P5, Tivo S3 and Onkyo 905 don't create any ambient noise from their closet to the room).

Okay, I'll work on the corner traps for the back of the room next. They're next anyway.

What about ceiling panels? Are they important?

Also, any thoughts on that one piano note that I talked about above?

Thanks!
-Mark

 

[jostenmeat]

Hey again Mark,

take what I say with a lot of salt, because Im just as new to this stuff as you are.

Is your piano issue occurring with the Audyssey in effect? And is it just with that one disc, or is that swell being replicated at that same frequency with other recordings as well?

It could be "overhang" in your room. It wouldn't necessarily come up louder on an SPL meter, since its not louder, but the decay takes much longer. Audyssey is supposed to help with that as it is designed to do.

I know that the particular placement of speakers can be VERY complex. When you pull or push the speakers from the front wall, what happens to that swell? Still there? I assume its still there no matter the listening position?

Regarding even more treatmests: As I've told you before, HT rooms are typically deader than 2-ch rooms. I sort of have my OWN half-baked-theory on this. When you listen to music, it might be nice to have the room effect where you might think the musicians are in your room? (though others say a dead room should allow you to hear the ambience of where the recording was actually created, not your own room's). Tastes vary greatly.

But, for HT effects I don't think you want it to sound like a screeching jet fighter is in your room? Again, just my own half-baked theory I just created. I hope someone else sheds light!

I think the easy way is to keep trusting your ears, keep it looking nice as an install. You can take it slowly and add a trap/panel at a time, and go from there. If you want outside opinions, you can just invite us over.

 

[jaxvon]

The problem with the specific note you referenced earlier could be a function of problems with the microphones in the recording, the post processing, your speakers, or perhaps all three. It sounds to me like you have a fairly well-treated room, so I don't think acoustical problems are the source. If the recording engineer used non-linear microphones for the recording or decided to apply some EQ during mixdown, that could definitely account for the note that sticks out. It could also be the case that your speakers have a cabinet resonance at that frequency. In the case of the former, your only option is to find another recording of the Beethoven sonata. In the case of the latter, you can either look at modifying your speakers to reduce the said resonance or purchase different speakers that do not suffer from such a problem (though it is quite difficult to find commercially available speakers that do not suffer from colorations due to cabinet resonances).

 

[AbMagFab]

Well, I hope it isn't my speakers, as I just spent a fair amount on them (Paradigm Signature 7-channel setup, S6's + C5 + ADP3's + S2's).

I hope it's the recording. This is on a BluRay disc, LPCM soundtrack, and I'm playing it through a HTPC, so there are a few additional variables (like the potential PC downsampling). My PS3 is in for repair, so I can't test it on another player atm.

I'll try a CD recording of it, which is a good idea. I'll post back my results (I'll also try again after I install the screen wall acoustic panels).