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Adding a second subwoofer, on average how flatter will the freq. response be?

post #1 of 12
4/25/12 at 7:55pm
Thread Starter 
Decided to do some testing of in room response using some test tones today and the results were pretty poor.

I'm using an LFM-1 Plus and can't seem to get a good response no matter where I've placed it in the room, doing the "sub crawl" didn't translate into great results either. I've tried 6 possible spots and still the same bass response all around just about.

Basically in the 65-70 range it's about 5 db down with a peak near the 60-65 hz range, under that until about 39hz I drop a good 20db and below that I'm not hearing a thing. The woofer is moving down to the 20hz test tones (Subwoofer set on maximum output) but I don't hear a single thing even with the receiver playing at -5 db (What I usually listen to movies/music at). Keep in mind this was done in the main listening position using an iPhone SPL meter

Will adding a second LFM-1 Plus solve these issues? The room is 19L x 14W x 8H, one odd doorway that opens into a hallway, room is around 3500 cu. ft I'd say.

Knowing that the subwoofer can do 25hz +/- 3db and not being able to even hear anything under 40hz is driving me insane to say the least.

I could MAYBE get away with one large bass trap, would that have any decent effect?

Thanks in advance for any advice
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post #2 of 12
4/25/12 at 8:42pm
Quote:
Originally Posted by BB1111 View Post

Decided to do some testing of in room response using some test tones today and the results were pretty poor.

I'm using an LFM-1 Plus and can't seem to get a good response no matter where I've placed it in the room, doing the "sub crawl" didn't translate into great results either. I've tried 6 possible spots and still the same bass response all around just about.

Basically in the 65-70 range it's about 5 db down with a peak near the 60-65 hz range, under that until about 39hz I drop a good 20db and below that I'm not hearing a thing. The woofer is moving down to the 20hz test tones (Subwoofer set on maximum output) but I don't hear a single thing even with the receiver playing at -5 db (What I usually listen to movies/music at). Keep in mind this was done in the main listening position using an iPhone SPL meter

Will adding a second LFM-1 Plus solve these issues? The room is 19L x 14W x 8H, one odd doorway that opens into a hallway, room is around 3500 cu. ft I'd say.

Knowing that the subwoofer can do 25hz +/- 3db and not being able to even hear anything under 40hz is driving me insane to say the least.

I could MAYBE get away with one large bass trap, would that have any decent effect?

Thanks in advance for any advice

First any phone with a db meter will not even be close to accurate especially the bottom end.
Second if you are setting in the middle of the room then you are in a null.
Have you tried moving the sub in all directions in the place you think is best
sometimes a foot over or forwards/backwards makes a difference.
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post #3 of 12
4/25/12 at 9:11pm
Thread Starter 
Quote:
Originally Posted by oztech View Post

First any phone with a db meter will not even be close to accurate especially the bottom end.
Second if you are setting in the middle of the room then you are in a null.
Have you tried moving the sub in all directions in the place you think is best
sometimes a foot over or forwards/backwards makes a difference.

On the back wall I had the best bass but still lacking in the low end, moving it more into the corner resulted in a bit more "boom". Flipping the phase to 180 seemed to smooth things out a bit but that is just from listening by ear so not 100% sure, it seemed better for only certain scenes/effects.

I know the phone meter isn't worth much but it's all I have to go by at the moment.
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post #4 of 12
4/25/12 at 9:20pm
Quote:
Originally Posted by BB1111 View Post

I know the phone meter isn't worth much but it's all I have to go by at the moment.

Well, you still may not have anything depending on which iPhone you have. Have you seen frequency response tests for the iPhone microphones?
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post #5 of 12
4/25/12 at 9:43pm
Thread Starter 
Quote:
Originally Posted by cel4145 View Post

Well, you still may not have anything depending on which iPhone you have. Have you seen frequency response tests for the iPhone microphones?

It's a 4S which isn't much better then the 3GS, I'll report back with better results once I get REW up and running

But besides that, how much of an improvement can be had from adding a second identical sub? Or would I benefit more from getting an AVR that does sub EQ? Currently I'm using MultEQ XT but in the manual EQ it only hits 63hz
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post #6 of 12
4/26/12 at 6:06am
Quote:
Originally Posted by BB1111 View Post

It's a 4S which isn't much better then the 3GS, I'll report back with better results once I get REW up and running

But besides that, how much of an improvement can be had from adding a second identical sub? Or would I benefit more from getting an AVR that does sub EQ? Currently I'm using MultEQ XT but in the manual EQ it only hits 63hz

See what your REW results are then go from there.
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post #7 of 12
4/26/12 at 12:41pm
Just a note - The outlaw audio LFM-1 Plus is on sale for $499 shipped (until April 30th). Not a bad time to potentially "have" to add a second.
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post #8 of 12
4/26/12 at 1:08pm
It's hard to tell what's going on without a visual representation of your frequency response curve. Generally speaking, having two subwoofers gives you flexibility and a higher likelihood of achieving a flat frequency response curve.

However, you will need an EQ either way. I have the MultiEQ XT and it does an adequate job for me, but YMMV.
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post #9 of 12
4/28/12 at 3:44pm
Here's a pic that worked for me



Here's the end result...I did end up getting the response right at the XO (80hz)

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post #10 of 12
4/29/12 at 6:50am
Thread Starter 
Thanks for the advice, still working on getting REW setup so I can really see what is going on.


Right now I have one subwoofer in the rear corner of the room, about 8 feet back from the listening position, if I were to add another LFM-1+ would next to the sofa be a good spot? Would be the most out of the way spot for it at the moment.


Also yesterday while watching How To Train Your Dragon, when the giant dragon comes out of the cave the one LFM-1+ chuffed pretty loudly, was similar to a popping sound. Would a second sub solve this issue? Should I run two in Max Extension or Max Output mode if I were to add another? Currently I have it set on MO.
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post #11 of 12
4/29/12 at 7:53am
You can't eq out of a bad room null.

Two subs help flatten fr response because in practice usually the various room nulls of the two subs don't perfectly align and the subs compliment each others weaknesses based on placement.

Two subs non colocated give you an increase of about 3db. As to port chuffing on HTTYD, if you turn it down 3db on your current setup from your preferred volume do you still have chuffing? If so then a second identical sub probably won't meet your needs - if so then yes the second sub will!
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post #12 of 12
4/29/12 at 9:33am
Just to add to what Archaea said.

Two same subs will allow them to work easier at a lower gain and you gain headroom. This may or may not reduce the chuffing you're getting dependant on what lvls you listen at.

REW will certainly give you a better idea of what's happening.
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