Rear Mounting Tweeters

[ralph-bway]

If I rear mounted the PE 49 cent Onkyo 3/4 inch tweeters in a line array the closest I can space them is 2.25 inches (because of the diameter of the rear magnet).

If I rear mounted them to a baffle 1.5 inches thick and angled the opening each driver would be mounted in the throat of a mini horn.

The crude pic of what I'm thinking of follows. Would this have a an adverse effect on the sound of the tweeters or the array?

[ralph-bway]

think I got the pic here

[ralph-bway]

don't know how but the image is in everything else under

"attaching image - help"

[ralph-bway]

Anyone chip in with some info or point me in the right direction??

[Illusus]

With just an angle cut like that you end up with a plain conical horn, notthe best contour for a HF horn. A tractrix would be ideal but it would be a real tedious task by hand, I guess if you're really 'tenacious' in nature you could shape your own router bit contour...but those are most likely not the wanted routes. A round over bit would probably do the job better than an angled cut. You'd, at least, get away from that sharp edge at the mouth of the horn. That edge may induce unwanted diffraction effects. Blow through a drinking straw at a sharp adge, then a rounded adge, you'll hear the effect.

You can actually see how your horn may perform by using Hornresponse; you have the throat area, mouth area, horn length...pretty much all you need for a good guess.

Give the conical horn a try, at least shape the mouth edge with some sandpaper. It won't be too hard to try one driver in a piece of scrap. While you're at it, try a few different angles and roundovers, see what sounds best to you.

[ralph-bway]

I couldn't draw it but that is what I thought of. Angle out the tweeter hole and then use a 3/4 inch roundover bit to eliminate the sharp edge on the face of the baffle.

How steep an angle should the hole flare out? I'll crossover to the tweeters at about 4.5K -5K.

The throat is 1 inch and the hole at the front of the baffle is a maximum of 2.25 inches.

I suppose I wasn't sure if how thick of a front baffle I needed (.75 - 1.5 inches) to get from a throat of 1 inch to an exit of the horn of 2.25 inches at the optimum angle.

Thanks for the help.

[planet10]

I haven't done the assymetrical thing with 2 tweeters (but have with some tractrix PA mids), but often use the technique to act as a waveguide on super-tweeters to get a better match with the FRs.

The picture is a closeup of an MTM designed for ceiling mount (3" thick overall)...

dave