Two Subwoofer question

[Andy Safholm]

I want to add a second subwoofer to my existing Home Theater system and wanted advice. My room dimensions are 20 x 20 with vaulted ceilings. I have one NHT SW12 behind my main speakers. I have read that I would have a significant amount of standing bass waves with the vaulted ceilings. Is it a waste of time/money to add a second SW12 behind my listening seat? Would it be to much? Any advice would be great!! Thanks a lot.

Regards,

Andy

[Sir Terrence the Terrible]

I want to add a second subwoofer to my existing Home Theater system and wanted advice. My room dimensions are 20 x 20 with vaulted ceilings. I have one NHT SW12 behind my main speakers. I have read that I would have a significant amount of standing bass waves with the vaulted ceilings. Is it a waste of time/money to add a second SW12 behind my listening seat? Would it be to much? Any advice would be great!! Thanks a lot.

Regards,

Andy

You would have to decide if it is too much for yourself. The amount of bass one enjoys is purely a taste thing. My taste tends to lean towards VERY clean, deep, and tight bass, and I tend to play my DVD's at about 5db's below reference. This requires two subs in my room so there is no bottoming, and ultra low distortion.

In your room, I would avoid putting the subs in corners. A 20x20 room is a acoustical mess in the bass region.

[Andy Safholm]

Thanks for the reply. Would the second sub level off the bass or make the acoustics worse? By adding the second sub I also can set them at 0db or lower. Thanks again!!

[Richard Greene]

You want both of your subwoofers placed near main speakers so they are sonically invisible.

One sub in front and one in back is much less likely to be sonically invisible (some people may enjoy the "special effect" of bass pressurization coming from behind their seat, but that's not likely to make music sound realistic).

The strongest standing waves form between two opposing room surfaces.

The room surfaces don't have to be parallel.

Placing two subwoofers on opposite sides of a room does prevent some standing waves between the two opposing surfaces they are near, specifically all odd-order axial (two-surface) standing waves.

That's why using left-right subwoofers can be useful, especially for videos when several people sit in a row, or on a couch, while listening.

A first-order axial standing wave between the side walls causes the bass to sound weak half-way between the side walls (location of the null) and stronger for listeners who are closer to a side wall (location of the maximum bass peak).

Everyone in a row of seats, or on the couch, would hear a different bass frequency
response.

Using left-right subwoofers prevents this standing wave, although there will still be standing waves from the front wall to the back wall, and from the floor to the ceiling, and from tricorner to tricorner, in a rectangular room.

The problem could be worse in a square room where the front wall to back wall standing wave is at the same frequency as the side wall to side wall standing wave because the distances between the opposing surfaces are the same.

You may assume by now that eliminating one standing wave by using two subwoofers is a good thing to do ... but for any specific listener, eliminating one bass peak or trough by using two subwoofers can make the remaining bass peaks and troughs easier to hear and even more annoying.

It's difficult to predict on paper whether adding a second subwoofer on the opposite side of the room will create a subjectively better bass frequency response for any specific listening seat (compared with placing both subwoofers next to each other, or stacked on top of each other, on the same side of the room).

Two subwoofers can play louder than one, or they can play at the same volume with lower harmonic distortion, so two subwoofers are better than one ... except for the extra money and extra space required for a second subwoofer.

If you use a crossover frequency that allows you to hear male voices through the subwoofer
with other speakers turned off (significant output over 80Hz., which I do not recommend for any subwoofers), you'd be better off using left-right subwoofers because output over 80Hz. tends to make a subwoofer sonically visible.

[Andy Safholm]

Thanks for the great reply. My acoustics for bass is not really good. I will put the second SW12 behind the other main and see what the results are. Great stuff, thanks again!! Have a great weekend!