DIY treble horn?

[TroelsM]

Hi!

I´m working on at LOUD-speaker (well not THAT loud, but enough to make some noise at private parties).

Its gonna be a 10" Bass/mid and a "titanium-dome" with a crossover somewhere around 3-4Khz.

I have two decent Titanium domes and I was wondering if I could make a horn of some kind to boost the level? Some of my favorite "small" loud-speakers are the good old EV in the grey "flat" box with a 12" and a treble horn (sorry cant remember the name. Something with 200, -SL200?. I will try to find a picture).

A cross-sction off the horn looks like the attachment. Could I make something like that and place in front of a normal dome-unit? ( I know, that I could... - would it work..?).

I was thinking on making a horn of Styrofoam for a starter. Any ideas?

EDIT: The Electro Voice speaker: http://www.stevesdjservice.com/images/Mar30_03.JPG

TroelsM

[Ed LaFontaine]

Hello Troels, want to bump & boogie?
You may want to consider for your "horn" profile the following:
y= SQRT(a*2 +Tan*2(theta)(x*2))
where
y = radius of contour
a = throat radius (2.54 cm dome = 1.27 cm)
theta = 1/2 coverage angle (for desired dispersion of 60 degrees, this is 30 degrees)
x = distance from throat
(x*2) means (x squared)

The transition of the horn to the baffle should be with a radius no less than wavelength/4, where wavelength is the upper limit for the horn.

Your depicted "horn" may be adequate for your intentions. I expect it would produce diffractions with freq. resp. effects

I would make the prototype from mdf. I would make the proven version from a select hardwood. If you use syrofoam I would coat the surface to smooth surface irregularities.

I need a routine scripted so I can create the profile described by the equation. My excel skills are lacking. With the profile I can turn it on my wood lathe. Would you like to collaborate?

What tweeters are you considering? Seas units are used by Amphion and others. I would consider the TBFC/G.

[TroelsM]

Hi and thanks for the fast reply.

The eq. seems to be very simple. I hav'nt got any mat-tools on my PC right now, but i could be calculated on a "pocket" calculator (texax 82, and the like).

As i understand it the eq gives curved sides but many horns have flat sides in 2 or 3 different angles, - like my drawing. Why?

I´m going to use some tweeters i have from an old projekt. Its probably 3/4 inch domes. They are not ment to be used as horn-drivers but what the heck...

TroelsM

EDIT: Looking at the eq. i get confused... Is it sqrt(a*2 + tan((2*theta)(x*2)) ?

[Ed LaFontaine]

Yes, it is much easier when done by hand. Let me try again:

y= SQRT(a*2 +Tan*2(theta)(x*2))

should be

y = SQRT(a*2 + (Tan(theta)*2)(x*2))

So easy to mess this up. Use the (Tangent of theta) squared.

Flat sides do not promote a smooth progression of the wavefront away from the diaphragm. Corners (abrupt changes in the profile) generate sound wave difraction which results in distortion of the sound at the listening position.

[TroelsM]

aha...

I can see that the sides should be as smooth as possible, but then I dont get why so many pro horns are made with flat/angled sides? When making the horn in plastic og metal it should be the same amount of work?

I will play around with the "new" eq.

TroelsM

[BAM]

Why not just buy a decent little compression driver and a DesignDirectSound fiberglass horn that fits your size requirements? If you can afford it, try a compression driver from Radian. Those can be had on PartsExpress.com but you'll have to look elsewhere for the DDS horns.

[TroelsM]

I Know that horn speakers are sold at many shops, but it seems to be do-able to make it my self and it would be a lot cheaper and a lot more fun...

TroelsM

[Variac]

I really don't know, but some pro horns are called "diffraction horns"
I think they use the sharp edges purposely diffract the sound to increase the angle of coverage. I get the impression that this is bad for sound quality though. There is a paper on the Peavey site that shows a straight sided horn that they claim is quite good. I'll see if I can find it..

EDIT: Here it is!

http://www.hilberink.nl/codehans/hornqwp1.pdf

[AndrewT]

Hi,
the horn in post 1 looks very wide for a treble unit. Depth of 70mm to 90mm is about right for 3kHz but diameter should also be about 80mm to 100mm. That big horn looks more like a badly designed mid horn!.
Try using a tractrix horn. It gives a short horn that meets the front panel at a tangent and looks really nice if turned in wood. There is no corner at the front edge and I've heard that it sounds good with treble units.

[TroelsM]

The horn in my first post is a pretty accurate model off the horn used in the EV speaker: http://www.stevesdjservice.com/images/Mar30_03.JPG.
I cant hear the lack of treble. They are some very nice speakers!

I dont know what the crossover-freq is, but maybe the horn is there to amplify the lack off mid from the tweeter-unit?

Does anyone have any info on the EV speakers? Datasheet? Units?

TroelsM