Effect of having multiple drivers in a cab

[kringle77]

Here's a question that I can't find a direct answer too. If you have a multi driver bass cab, like a 4x10, what is the effect on frequency response. I know that in a 4x10 there are phase cancellations which probably overall, reduce mids. So, would that mean you would have a response with more emphasis on 500hz and lower and less above that? If Im close, what range is additive and which is subtractive in a 4x10 cab?

[PlungerModerno]

Originally Posted by kringle77

Here's a question that I can't find a direct answer too. If you have a multi driver bass cab, like a 4x10, what is the effect on frequency response. I know that in a 4x10 there are phase cancellations which probably overall, reduce mids. So, would that mean you would have a response with more emphasis on 500hz and lower and less above that? If Im close, what range is additive and which is subtractive in a 4x10 cab?

Here's some reading materials (put better than I can):

http://barefacedbass.com/uploads/BGM62%20Jan2011.pdf

http://barefacedbass.com/technical-i...dispersion.htm

http://barefacedbass.com/technical-information.htm

http://barefacedbass.com/bgm-columns.htm

In short: Multiple sound sources mean more complex acoustics. 2X2 arrays of drivers make certain frequencies have very inconsistent polar response. . . and tweeters + a crossover aren't as good a as vertical arrays of drivers(of comparable drivers).

[Downunderwonder]

It is frequency and location dependent. Google comb filtering and beam frequency. Or go to a funky cover band gig with vocal PA and listen from right in front of the 4x10 and then go to the side.

[DukeLeJeune]

Originally Posted by kringle77

Here's a question that I can't find a direct answer too. If you have a multi driver bass cab, like a 4x10, what is the effect on frequency response. I know that in a 4x10 there are phase cancellations which probably overall, reduce mids. So, would that mean you would have a response with more emphasis on 500hz and lower and less above that? If Im close, what range is additive and which is subtractive in a 4x10 cab?

At frequencies where the drivers are within about 1/4 wavelength of one another (edge to edge), their outputs add. From 1/4 to 1/2 wavelength they add, but we start to get a little bit of cancellation at the pattern edges, so we have less than perfect addition. North of 1/2 wavelength, we get progressively more and more cancellation.

The net result is, the more drivers we cluster, the more downward-sloping the power response (summed omnidirectional response), so the "darker" the perceived tonal balance.

But I'm not sure where the tipping point is between "more total energy due to summing" and "less total energy due to cancellation" as we add more drivers. My guess would be, where the edge-to-edge distance is approximately one wavelength, in both dimensions (or the average edge-to-edge distance if the array isn't square). That comes out to about 700 Hz for a 4x10 cab, assuming 19" edge-to-edge. But this is just a guess.

[Arjank]

Originally Posted by DukeLeJeune

At frequencies where the drivers are within about 1/4 wavelength of one another (edge to edge), their outputs add. From 1/4 to 1/2 wavelength they add, but we start to get a little bit of cancellation at the pattern edges, so we have less than perfect addition. North of 1/2 wavelength, we get progressively more and more cancellation.

The net result is, the more drivers we cluster, the more downward-sloping the power response (summed omnidirectional response), so the "darker" the perceived tonal balance.

But I'm not sure where the tipping point is between "more total energy due to summing" and "less total energy due to cancellation" as we add more drivers. My guess would be, where the edge-to-edge distance is approximately one wavelength, in both dimensions (or the average edge-to-edge distance if the array isn't square). That comes out to about 700 Hz for a 4x10 cab, assuming 19" edge-to-edge. But this is just a guess.

+1

I would like to add the following, there is also the increase in baffle size. This has a large effect on the frequency range where the bafflestep occurs. With a 4x10 the baffle width will be 24". The bafflestep will occur between approx. 250 and 500hz. So, this will also make the overall sound "darker".

[kringle77]

Thanks guys, that was pretty much what I wanted to know. I appreciate the effort and responses.