inverse horn for omni directional?

[killerfishes]

how would one design/ make one. I figure an up fireing woofer with a horn shaped cone above it to disperce the sound. I would need to play with XO points but it would be set at under 2khz.

Any ideas?

[bear]

I think you have to ask yourself first, "what am I trying to do"?

There is one company that uses a compression driver into a horn that is aimed down, there being a complementary curve below, with the exit being 360 degrees rotated about the vertical axis.

You might want to look around for that?

Not quite "omni directional" but definitely doughnut shaped certainly.

At bass freqs most woofers are omnidirectional or at least hemispheric.

As the frequency goes up for any vibrating surface the wavelength gets shorter. As the wavelength gets shorter the surface radiating the sound begins to emit the sound in more and more of a direction perpendicular to the vibrating mode. The critical point is when the wavelength gets around 1/4 wavelength distance compared to a dimension of the vibrating object.

So one answer is to use smaller size surfaces to make sound below 2kHz. Of course the problem with that is merely max output level.

That can be solved by a multi driver line source - which then resolves to a longish ribbon driver of narrow dimension.

You can also look at the Walsh driver solution as well.

Unfortunately there is nothing that is inverse of a horn unless you consider some spherical or egg shaped object with a driver mounted on the surface - but it will have no "wavguide" properties per se.

You could scale up the above described "doughnut" horn...

_-_-bear

[leadbelly]

http://www.diyaudio.com/forums/showt...519#post439519

[killerfishes]

Originally posted by planet10


Here is a pic of my latest surround experiment ... these will hang from the ceiling just behind and a bit to the sides of the listening area. They have a 6" FR w whizzer (costing only labour and some ductseal, these are very much Frugal-phile (tm) material.

dave

bingo this is what I'm looking for. is it just any exponential "sp?" curve for the deflector or is it made like a horn ? I'm making plasma tweeters and want 360º bass/midbass up to 1.2Khz where the tweet will take over. The plan is to use a 7 or 8in Dayton RS series woofer. iv seen the ones for sale but they don't list specs on the horns, only this pic.

[bear]

Ummm... is the plasma tweeter direct radiating out of a horn?

The curve of the HF element shown in that cutaway is likely to conform to one of the usual curves (exponential is one).

The Mid driver is likely only getting reflected from the surface that it faces, as there is not going to be much if any compression taking place, and the mouth size is too small to have any effect at LF... I think those speakers may have another woofer for LF, not sure...

it's not clear from that cutaway but the commercial speaker uses an upward firing mid that sits where the wireframe part of the image posted is...

_-_-bear

[sdclc126]

Originally posted by killerfishes
how would one design/ make one. I figure an up fireing woofer with a horn shaped cone above it to disperce the sound. I would need to play with XO points but it would be set at under 2khz.

Any ideas?

Are these for your mains/fronts? Have you looked at the Linkwitz Pluto? http://www.linkwitzlab.com/Pluto/intro.htm. No "dispersion horn" above the woof - it just fires up, and the XO point is set so that the woof operates in a wide dispersion frq range.

I'm guessing there is some loss of sound pressure/efficiency without a "lens" to concentrate the sound into a vertical field, but these speakers are intended for relatively smaller listening environments, and I think allowing the woof to fire upward "unhindered" may make for a more realistic illusion of the live performance.

I've had many thoughts about these kinds of designs and whenever I finally build my "ultimate" speakers I think they will be something like bi-polar/omni-directional in concept. A few designs use conventional forward-firing drivers plus a ceiling-firing driver mounted in the top of the cabinet - possibly getting good relative efficiency in the primary soundstage with the added onmi dimension up top.

There is also the bi-polar design - for fronts/mains they are mounted in the front and rear baffles of a conventional cabinet, 180 out of phase; I wonder what this would be like with a top-mounted driver in addition - overkill maybe? I've also seen some designs with the woof mounted at about 45 degrees toward the ceiling - I was thinking of trying this with a bi-polar design, tweeter mounted on top between the woofs, facing forward.

Lots of possibilities here...

[killerfishes]

Originally posted by sdclc126



I'm guessing there is some loss of sound pressure/efficiency without a "lens" to concentrate the sound into a vertical field,

my problem is I want them to look and sound good. I'm going to stack the tweet over the woofer, I know playing into a flat bottom will sound like ****.

the Idea

edit. I think this may be a good time to test out my vacume bagging skills, I will get some HD foam and hot wire it into shape then overlay it with carbon/fiber, kevlar, or CK.

[sdclc126]

Your rendering/idea looks somewhat like these:

http://www.cd-konzert.de/loudspeaker.htm

This is actually not a new design - there have been several speakers like this on the market over the years. I think it's quite a challenge for the DIYer, with the curved horn surfaces, etc., but I'd sure love to hear the result.

Good luck with your project - I'm sure we'd all like to see what you've come up with when you're finished. Hope the Duevels give you some ideas.

BTW - have you decided on drivers yet, or will that be decided when the concept is more advanced?

[Puggie]

Originally posted by sdclc126
Your rendering/idea looks somewhat like these:

http://www.cd-konzert.de/loudspeaker.htm

This is actually not a new design - there have been several speakers like this on the market over the years. I think it's quite a challenge for the DIYer, with the curved horn surfaces, etc., but I'd sure love to hear the result.

I knew I'd seen it somewhere else, I've been looking for that site all morning. I think there is a company 'Celtic Audio' or similar in the UK that do something very similar but using a conventional tweet, not a compression driver.

[kneadle]

Pardon the interruption:

Where may I find details about the applications for omnidirectional speakers? I'm trying to get my mind around the concept; rather, the concept is trying to get around my mind...

My mind works like this: one places two speakers on either side of the "stage" for stereo reproduction. What is omnidirectional doing which is different or better?

Thanks,
Dave