A few newb questions before I start installing...

[captainobvious]

I read through the FAQ and found some very good info.

I have a couple of questions that I didnt find clear answers on and would like to ask before I start installing anything.

1. Why are most of the IB subs pictured, installed facing each other inside the manifold? Arent there cancellation issues by doing this?

2. Is there any benefit to running two seperate stereo subs/manifolds at the locations of the mains as opposed to a single manifold containing all drivers in a center location between the mains? Is it worth the trouble of constructing and tuning for 2 seperate subs, and is stereo any benefit over mono at these frequencies? (Probably about 60hz and down)


My listening area is a combination living room/dining room with appx dimensions of 18' x 40' x 9' ceilings.

[ThomasW]

Jan 5, 2011 9:26:40 GMT -7 captainobvious said:

1. Why are most of the IB subs pictured, installed facing each other inside the manifold?

To cancel the mechanical vibrations off the driver frames

Arent there cancellation issues by doing this?

The output from the cones isn't canceled as long as they're wired in phase

2. Is there any benefit to running two seperate stereo subs/manifolds at the locations of the mains as opposed to a single manifold containing all drivers in a center location between the mains? Is it worth the trouble of constructing and tuning for 2 seperate subs, and is stereo any benefit over mono at these frequencies? (Probably about 60hz and down)

This tends to be a question with almost religious fervor.

Some swear it's extremely important to have stereo subs.

IMO mono subs are just fine. I hear no decrease in channel separation or smearing of the stereo image using mono subs

[mojave]

The stereo vs mono subwoofer question involves several things to think about. First of all, in order to do it you have to either run the mains full range or have some way of providing them with a high pass filter. I think they always need a high pass filter to reduce distortion at high SPL. You also have to set the low pass for the subs. You can use a Behringer DCX2496 and easily do this. However, then you are limiting yourself to using its DACS and you are going through an extra ADC to DAC conversion step. It is also hard to integrate the LFE signal back into a stereo subwoofer setup, but it can be done.

I have a DCX2496 and experimented with stereo bass. I was able to quickly switch back and forth between a dual stereo or dual mono setup at various crossover frequencies. I couldn't really hear much of a difference with a lower crossover (60 Hz and down). I don't think it is worth the hassle. Also, my system sounds better without the DCX2496 in the signal chain.

For me, however, there is a big difference between dual subwoofer and single subwoofer locations regardless of whether they are stereo or mono. I get a much smoother frequency response with a subwoofer in the front left and right of my room than I can at any single location. I also get more room gain with the subs in the corners. In an IB system you should still get the benefits of room gain and a smoother frequency response with using two manifolds as opposed to just one manifold in the center.

[captainobvious]

Very helpful responses. Thank you very much.

My mains (which I'm currently building) will be a 3-way setup actively crossed over using a DCX-2496. MTM top cabinet and dual woofers in the lower cabinets. I may have to play around with locations before cutting for the manifold to determine which setup will sound the best (one location mono, dual location mono/stereo).

Thanks