HI y'all. I've done the searches (I think) and still need help.

I have a rectangular 3000 sq ft room with the TV and 7.1 audio setup at one of the ends. I've never gotten the bass response I've wanted from movie soundtracks, and I've tried a lot of good subs. I've owned two SVSs (including a recent PB12/2+), and now have two Velodyne HGS 18s, and two HGS-15s.

I used the Room EQ program with the Digital Rat Shack SPL meter to graph the frequency response, and every conceivable combination of positions I can muster with one or two subs hooked up- I can't keep all 4. (Two HGS-18s on either side of the from mains (inside and out), one and two subs on either side of and behind the listening position, and every permutation in between). I've moved the listening position one foot to the left, or to the right, in the center, forward, back, etc. The resonse was similar with the SVS as it is with the Velos, so I know it is the room.

The bottom line is I have these big dips in SPL from 15-20 db+, from bout 30-50 Hz. The frequency spread and the amount of the drop in level vary somewhat from in the different positions but none, to my recollection, is much less than 15 dB. I do have all the graphs saved as jpegs if it would be helpful. What can I do?

HI y'all. I've done the searches (I think) and still need help.

I have a rectangular 3000 sq ft room with the TV and 7.1 audio setup at one of the ends. I've never gotten the bass response I've wanted from movie soundtracks, and I've tried a lot of good subs. I've owned two SVSs (including a recent PB12/2+), and now have two Velodyne HGS 18s, and two HGS-15s.

I used the Room EQ program with the Digital Rat Shack SPL meter to graph the frequency response, and every conceivable combination of positions I can muster with one or two subs hooked up- I can't keep all 4. (Two HGS-18s on either side of the from mains (inside and out), one and two subs on either side of and behind the listening position, and every permutation in between). I've moved the listening position one foot to the left, or to the right, in the center, forward, back, etc. The resonse was similar with the SVS as it is with the Velos, so I know it is the room.

The bottom line is I have these big dips in SPL from 15-20 db+, from bout 30-50 Hz. The frequency spread and the amount of the drop in level vary somewhat from in the different positions but none, to my recollection, is much less than 15 dB. I do have all the graphs saved as jpegs if it would be helpful. What can I do?

A couple feet here or there is probably not going to really cure the huge dips you are experiencing. You most likely need to split the subs up to opposite sides or ends of the room or co-locate them in an opposite end/corner of the room.
If placement does not solve your issue, you may need to enlist the help of some electronic correction. I would try an SMS-1 or similiar device to help in that regard.

A couple feet here or there is probably not going to really cure the huge dips you are experiencing. You most likely need to split the subs up to opposite sides or ends of the room.
If placement does not solve your issue, you may need to enlist the help of some electronic correction. I would try an SMS-1 or similiar device to help in that regard.


I solved my null problem by stacking my subs. I had them split up (front right, rear right) and testing showed me the one in the front had the null, not the one in the back, but when both were playing, the null existed. I stacked them in back, and the null is gone.

With respect to using EQ to fix nulls, my understanding from reading posts by people more knowledgeable than me is that EQ is for reducing peaks, but doesn't work really for raising nulls. Do some reading (search) on nulls here and you'll see the discussions.

I solved my null problem by stacking my subs. I had them split up (front right, rear right) and testing showed me the one in the front had the null, not the one in the back, but when both were playing, the null existed. I stacked them in back, and the null is gone.

With respect to using EQ to fix nulls, my understanding from reading posts by people more knowledgeable than me is that EQ is for reducing peaks, but doesn't work really for raising nulls. Do some reading (search) on nulls here and you'll see the discussions.


Correct, you will probably need a combination of both. An EQ will help you tame the peaks which can ultimately help lessen the nulls. But both solutions are needed to help the worst scenarios.

Thanks, guys. I reaaly can't stack the subs as one of the reasons I got two subs is that I could localize one sub to "that corner", even with the X-over set to 60 Hz, and I really hate that.

I just ordered two corner bass traps and will let you know how that works.

Thanks, guys. I reaaly can't stack the subs as one of the reasons I got two subs is that I could localize one sub to "that corner", even with the X-over set to 60 Hz, and I really hate that.

I just ordered two corner bass traps and will let you know how that works.

That's a bummer, it really sounds like you have a difficult situation. I hope you can get something worked out. Do you have access to a DD-18 you could try? Using a single sub and some graphical analysis may go a long way towards solving those pesky problems allowing you to make many adjustements very easily.

check out this post

http://www.avsforum.com/avs-vb/showthread.php?t=745281&highlight=swgiust