Sub placement changes

[grn1969c10]

I added some fiberglass bass traps to my front corners and decided to play with sub locations again. Right now I'm using two mismatched subs - One on each side of the TV cabinet. I disabled the EQ and ran a sweep. Then I moved a sub 1/2 way to the corner took a sweep. Moved it into the corner, another sweep and then repeated the process with the sub on the other side.



The first sweep is dark blue and has the lowest output between 60 and 100hz. This is the placement I have been using because (In normal use) I'm applying EQ cuts to several frequencies from 40hz on up and this location lets me use the least EQ.

Is this line of reasoning logical? Any ideas on why sub placement and 6" thick corner traps have so little effect on the 20 through 50hz range?

[tonyvdb]

It is my understanding the bass traps need to be much thicker than 6" to affect between 20-50Hz and are not as affective in that range anyhow.

[thewire]

Two rows deep of R19 stacked flat on one another would help that low. If not, maybe you could return it unused. That would be a pretty thick trap. It would however hurt your extention. It might be best to use some equalization to deal with that peak as far as the frequency response goes, then worry about modal ringing with the trapping.

[grn1969c10]

I posted a trap / no-trap comparison in the Home Audio Acoustics forum. The reading I have done led me to believe that most traps more than 6" were built with lower density fiberglass such as OC 703 or Roxul 40. Since I had the Roxul 60, I limited it to six inches thinking a full superchunk would not add much benefit. Maybe I goofed.

I'm trying to work with sub placement, room treatment and EQ to make the best of what I have, as the budget is about exhausted. (Not to mention all this work on the audio and I'm still using an old school 25" television that I've repaired with super glue and donor plastic from CD cases.)

Given some unkown theoretical baseline of performance - Does the "in-room" result imply the low bass is being absorbed somehow or the mid bass is being boosted? If it's the latter, I suppose a ton of mid bass EQ would be acceptable. The room, unfortunately, has thin wood paneling over studs with no sheetrock backing and lots of windows.

I'm not aware of the subs bottoming out or anything but I feel like I am driving them pretty hard. The input to the BFD is dangerously close to clipping and the subs gain knob is about 70%. I'm tempted to try to lower the input level to the BFD but then I'll have to up the sub gain even more to compensate. I like to listen to movies in the low to mid 80db range with brief, loud scenes bumping 100db.

I feel like I have done all I can do with sub placement and the traps. At this point, I suppose I just need to fine tune the levels and determine how much EQ I can tolerate. School starts up next week so I won't have nearly as much time to fool around with the system.

[thewire]

That is what happens when we lower the level. We need to listen to the bass higher. That is why when a movie has lots of midbass that I hear, I lower the volume so it sounds right. Midbass can be difficult to deal with but is very rewarding when improved. It looks your already around 95% of the way there as far as the lower bass goes. A commercial theater rolls off at around 35Hz.

[Wayne A. Pflughaupt]

I added some fiberglass bass traps to my front corners and decided to play with sub locations again. Right now I'm using two mismatched subs - One on each side of the TV cabinet. I disabled the EQ and ran a sweep. Then I moved a sub 1/2 way to the corner took a sweep. Moved it into the corner, another sweep and then repeated the process with the sub on the other side.?

I can’t tell from what you wrote if you were using a single sub or both for your sweeps.

Given some unkown theoretical baseline of performance - Does the "in-room" result imply the low bass is being absorbed somehow or the mid bass is being boosted? If it's the latter, I suppose a ton of mid bass EQ would be acceptable.

The main thing bass traps give you is faster decay times for the bass, which makes the bass sound tighter. Their affect on taming peaks and valleys in response is usually minimal, unless you have so many traps in the room that you have to leave your guests outside.

I'm not aware of the subs bottoming out or anything but I feel like I am driving them pretty hard. The input to the BFD is dangerously close to clipping and the subs gain knob is about 70%. I'm tempted to try to lower the input level to the BFD but then I'll have to up the sub gain even more to compensate. I

Sounds like you may need a sub upgrade. Or maybe just determine which sub is best and ditch the other. Often mismatched subs only degrade overall performance. I’d take measurements at various locations to determine which one is best (i.e., the least distance between the peaks and valleys, best SPL level and extension), then compare the two subs with separate readings at that location.

Regards,
Wayne

[grn1969c10]

I can’t tell from what you wrote if you were using a single sub or both for your sweeps.

I was using both subs for that particular set of test. I ran the first sweep with this.


Then moved sub 1 half way to the left corner, ran sweep, then into the corner and ran sweep.
Then moved sub 2 half way to the right corner, ran sweep, then into the corner and ran sweep.

Moving the subs into the corners did not affect the 20 to 50hz region at all. The gain in the 60hz and up range seemed similar for both subs, but in this case is undesirable.

Their affect on taming peaks and valleys in response is usually minimal

I had hoped that by correcting room mode issues their effect on peaks would have been, shall we say, "less minimal".

Sounds like you may need a sub upgrade.

Definitely. I need a pair of ULS-15's. As it is, the CSX-15 is more capable than the PSW-1200. There's a very good chance that the two subs won't work well together. I should be able to prove it one way or the other with totally awesome tools such as Room EQ Wizard. I'm investigating phase effects right now and they are pretty far out. There are a lot of different contributing factors to an audio systems performance. "Divide and conquer", they say. Thankfully, I find acoustics a very interesting study. Who knows, maybe understanding this stuff will help land me a paying job one of these days!

[Wayne A. Pflughaupt]

grn1969c10 wrote:

I had hoped that by correcting room mode issues their effect on peaks would have been, shall we say, "less minimal".

To find out of they’re doing anything for you, use a waterfall graph, one with traps and without.

Regards,
Wayne

[grn1969c10]

I had posted one in the Home Audio Acoustics forum, but I think that I shall redo the test when I finally pull the traps down to finish covering them.