OB mains in front of IB

[jimcant]

I hope that the answer to this question is not blindingly obvious, but I have not seen it discussed before and have been unable to resolve it by myself

My dual manifold IB's are located in the front wall of my room, about 6' behind my main speakers.
The open baffle main speakers have a 15" coaxial driver which is run full range, and a 15" bass augmentation driver covering about 80Hz downwards.
The IB is crossed at about 80 Hz as well.

Therefore it is possible that at some frequencies there is output from all three sources.

With all drivers in phase, it would seem to me that the rear wave from the OB's would be out of phase with the IB and could induce some cancellation

Is my thought process correct?

Thanks,
Jim.

[ThomasW]

Mar 26, 2010 0:27:02 GMT -7 jimcant said:

The open baffle main speakers have a 15" coaxial driver which is run full range, and a 15" bass augmentation driver covering about 80Hz downwards.
The IB is crossed at about 80 Hz as well.

Therefore it is possible that at some frequencies there is output from all three sources.

With all drivers in phase, it would seem to me that the rear wave from the OB's would be out of phase with the IB and could induce some cancellation

Is my thought process correct?

Dipole/OB or monopole, there are all kinds of cancellation issues when multiple drivers at differing distances to the listener are playing the same frequencies.

And that's but one reason why crossovers were invented, and IMO are a mandatory part of any good sound system .......

Look around for articles talking about "comb filtering" as it relates to audio for more info on this

[jimcant]

Thanks Thomas,

I am doing as you suggest and from the looks of it, could be at it for some time
I have only managed Moulton Labs articles so far

I was aware of the phenomena of comb filtering but was under the mistaken impression that it did not have much influence at low frequency, where most of my overlap is.

I guess one can have too much of a good thing ;D

Cheers,
Jim.