Add Second Sub to fill in for NULL?

[avnetguy]

One outstanding problem I've had with my living room HT is a nasty null at about 60hz. Now the sub I have is in the best place it can be right now, all other frequencies are fine or tamed down nicely with a DSP1124. Obvously trying to dump extra power into the null from the current sub is not a good idea but was thinking if adding a second sub at a different location filtered to output 60Hz only would work to fix this.

Anyone ever done or tried this?

Steve

 

[GranteedEV]

Do you mind doing me a favor? Without moving the measurement microphone laterally, raise it up to ~3 feet below the ceiling and do a sweep.

This will tell you if this 60hz issue is a vertical or horizontal problem. If vertical, you may benefit from raising your current sub above the vertical center line, somehow.

The above won't help you at any other seat like a second sub will, though. If adding a second sub, I would first disengage any EQ cuts and reapply cuts after the subs are integrated.

 

[WaynePflughaupt]

What you might try is taking measurements at locations where you might put a second sub, and see how response looks at 60 Hz at those locations. If you find one that eliminates the 60 Hz null, then you have a good chance that adding a second sub will fix the problem. Granted, things may change when the second sub is actually added, as there may be some “reaction” between the two, but I think some additional measurements would give you a good indication if it would work.

Regards,
Wayne A. Pflughaupt

 

[avnetguy]

GranteedEV, I'll give that microphone height adjustment a test when I setup again and how much the results vary when I add in 1.5 ft. Honestly, I never really thought of a vertical adjustment to the primary sub but it makes sense to try. My main concern is if I adjust the sub height I'll probably, not for sure of course, be just moving the freq of the null.

Wayne, I've only got two positions in which to place a second sub with a little bit of wiggle room in each area, one is a corner placement, the other has only one wall. I'll setup the 1124 to only allow a narrow freq range near 60Hz to the second sub to minimize interaction, then see what the sweep results look like and of course, how it sounds.

I always prefer to keep it simple but sometimes things need to get a little more complicated I guess.

Steve