Center-Center Distances and Horns

[BassAwdyO]

Ok experts I need your help on this one. Say we have two horn tweeters. We're using them for sound reinforcement, and we want to put them together as close as possible to increase directivity and efficiency.

Will the center-center distance of the actual driver matter as much in this instance? It will be impossible to get under maybe 3 inches of seperation, but even so what kind of lobing issues and such will occur?

What result might this have on sound quality?

[mwmkravchenko]

Your diagram offers a good idea. In a well designed horn the wave front will exit as a soap bubble pushed through the same shape. It exits with a slightly curved wave front. There are all kinds of horns designed to minimise the distosions to the wave passing through them but thats a different story.

When you have two horns that close together there wil be mutual coupling where the wavelength of reproduced sound is approximately equal to the diameter of the horn mouth. After that there will be lobing. The higher up in frequency you go of course the shorter the wavelength and the greater lobing.

Short answer for sound reinforcement I don't think to many people will find it objectionable.

Mark

[GM]

Greets!

It will depend on how far away the crowd is since over distance the parallax error decreases. Up close there will be comb filtering both on and off axis, so the response won't be as smooth, and up high there may be some audible loss of clarity, but that's pretty common in any prosound app with multiple speakers covering the same BW.

GM

[thalis]

You can explore these comb filtering issues and have an idea of what happens with angle and with distance with this very easy to learn and function excel-based program:
http://www.pvconsultants.com/audio/radiation/vpr.htm

Regards,
Thalis

[BassAwdyO]

Up close there will be comb filtering both on and off axis

Wouldnt that depend if the tweeters were arranged vertically or horizontally? I dont see any reason why there would be comb filtering on axis if the drivers are arranged horizontally.

[GM]

Greets!

?? OK, I'll bite, using your drawing, why do you think it will be less/none than when vertically oriented?

Anyway, due to our hearing being more acute in the horizontal than vertical plane, it will actually become obvious at a lower frequency and why they should be arrayed in an arc to mimic the early multi-cells, preferably with their throats overlapped if their dimensions allow it.

[BassAwdyO]

Well if we arange the tweeters side by side horizontally then the on axis plane will be represented by the line labeled on axis, and the line which goes straight down through the picture and intersects the line labeled on axis.

This may cause a greater amount of comb filtering off axis I suppose, but on axis I dont see why their should be any. The distance from any point on that plane to the center of either driver will be the exact same.

[GM]

Greets!

Draw a line down the center of each horn. These are the on axis lines once the horns begin beaming. It's the parallax errors from the left horn to both ears and right horn to both ears that matters, so there's problems on the acoustic axis, increasing with increasing listener offset. Now do this when they are vertically aligned and it's not nearly as bad.

GM

[mwmkravchenko]

GM has nailed it

MArk