Effects of two different subs in close proximity.

[SUBduction]

I was wondering of someone could link me or shed light on the effects of two different subwoofers used in close proximity to each other. I'm particularly interested in tapped horn subs. It seems to me like we're dealing with cancellation issues.

Last summer I tested two different tapped horns, one stack on the other and noticed a dip in expected output. At first I realized this was a polarity issue but changing polarity on one of the subs helped but not as much as expected.

For simplicity's sake, lets say "Sub A" is about 8 feet from throat to mouth and "Sub B" about 4 feet.

Thanks for any information you can provide.

 

[NEO Dan]

If you wanted to go full on geek you might export a wav file if the impulse response from hornresp for each design and combine them and import the result into REW for examination. If you have a mic and preamp you would just measure the pair with REW.

 

[Zero D]

You also need to delay the cab with the shortest path length to match the others longer length & delay. A digital delay would do it, as built into many crossovers etc.

To discover Exactly what the delays of both cabs are, you would need a good mic & software such as REW etc. Set the mic the same distance from each cabs output, say 1 metre @ LOW volume, & read of the distance in the software on your comp.

Then you would need to do the same with your top cabs to ensure their delay matches the bass cabs.

 

[chris661]

THs aren't good for mixing and matching.

From what I can tell (and this has gone round a few times), most of the LF output is from the front of the cone, and is fed down the length of the horn, past the magnet, and out.
Higher up, most of the output is from the magnet side of the cone. In-between, its anyone's guess.
You'll have phase wraps all over the place, either way.

In a more general sense, I'd recommend using cabinets all of the same tuning (as a minimum), as this will ensure reasonable phase tracking between cabinets, and also you avoid situations where one cab can go loud, and the other can go low, but if you try to run the two, you can only go as loud as the quieter one (plus 6dB), and only as low as the higher one. Its a waste of both of them.

Chris