Matching dispersion characteristic at the crossover point (400hz).

Back story: I have a big space to fill with sound, 11,000 ft^3 or so. I also have a collection of large horns and compression drivers that I would like to use, if possible, for the surround speakers.

They will be active 3 ways. The mid-range horns are the big Altec Mantarays. I have two with a 60x40 dispersion and two with a 90x40 dispersion.

I can provide the time alignment easily enough since these are active. The c2c spacing is going to be less than 1/2 a wavelength but greater than 1/4 wavelength @ 400hz - acceptable?? How do I determine what drivers/alignments will have matching dispersion characteristics? Or to be more specific, I want to mate these horns to a simple sealed cab with a pair of 15" pro drivers. Is comb filtering even audible at 400hz?

Thanks guys, that info is of great help!

Since these are going to be surrounds, they will be along the back and side walls, not in the corners. Nothing can be that easy

I've have a little more time to think about this and... If I were to build a 2x15" array the drivers would be at least 16" apart. But when crossing at crossed 400hz (1/4 wavelength would be 8.1") so there would be comb filtering between the two 15" drivers AND between the 15's and the mid horn.

Is this a big concern or something you can file under compromise? The Onken w (two driver array) is often matched to altec mid horns, but it's obviously going to suffer comb filtering as I just described.

What's the advantage of stacking them vertical, vs horizontally? The Altec mid horns are wide enough to accommodate a side by side configuration.

It's bad enough that there are so many rules (as dictated by physics) to speaker building, but the real killer is that there is no consensus on what you can get away with, because you pretty much have to break a few rules. Even Danley's synergy horn doesn't have a smooth mouth termination and as such should cause reflections back into the mouth, right?

Buy, build, measure/audition rinse and repeat can get pretty expensive.

I think I'm going re-visit the idea of a FLH. I like what I already have (80hz FLH) but want a f3 at 60hz this time around.

Building and bracing six, 60hz front loaded horns is going to take awhile... (makes me think of the quote in your signature)

Thanks Bill. I will read it, and more importantly attempt understand it all. Thanks for the link.

Ah, got it. So in something like the JBL Everest (side by side configuration) they are crossing to the mid horn low enough that they avoid lobbing between the drivers?

So if vertical orientation avoids horizontal lobbing, then with something like my current setup (single driver front loaded horn crossed to the altec 1003 horn at 300hz) I shouldn't get any lobbing/comb filtering on the horizontal axis, correct? With the right floor and ceiling diffusion/absorption the lobes will have a pretty minimal impact... hmmm interesting.

So the Onken W is only horizontal because it would be too tall to stack the drivers vertically?

Yep, good point, but I wonder why Tom didn't bother with it. Maybe it's not that audible at certain frequency's? Your avatar looks like a DIY synergy horn. Got any details on it, I would love to learn more!


Exactly, I understand the limitations. But is it a worth while trade off for having 300-5Khz (or 500-7Khz) on a single horn/compression driver.

There is approx 56cm c2c between my bass horn and Altec1003's horns. That would require a crossover at 147hz to satisfy the 1/4 wavelength rule.

I can cross the 1003 as low as 300hz. So that would allow a max c2c of 27.5cm or 10.8". The bass horn would have to be very squashed to achieve that kind of spacing.

This is looking more and more like mission impossible. Looks like I either have to live with it or move away from large format horns. At least with my single driver bass horn & 1003 mid horn (see avatar), the lobes will be directed at the floor ceiling, correct?

Ah, I didn't know that the 15's had different crossovers points.