DIY Omni Directional Speakers

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#21
Have you seen this?

Here is a high efficiency omnipolar design from a decade ago.
Platinum Audio, before they went out of business, had a flagship speaker called the AirPulse 3.1. It used 2 12" woofers with one side of each radiating in the large cylindrical horns and the other side radiating into the 360 degree horns. In the middle was some type of compression driver also radiating into a 360 degree horns. It looks like it may have been a 3 way but I can't find many technical details.

Here is a link with a short description
http://www.enjoythemusic.com/wces97/wces97equipment.htm

This page has some line drawings of internal construction of the reflector assemblies and the woofer back horn. Most definitely not a weekend project.
http://www.enjoythemusic.com/magazine/factory/tlg/
 
#22
Hi,

ive been interested in omni sound and have tried building one.
it didn't work out the FR was too offensive I tried to build the shape of the diffuser like the bella luna. I vaguely suspect that using a similar design to say the bella luna Jupiter requires a low crossover frequency between the mid and tweeter. maybe say 1khz??
However its hard to find a tweeter that can crossover that low, has anyone had any success? I think the bella luna uses a horn tweeter? I'm still interested in building a omni, tho probly only as a rear speaker as I still have an unused nice looking wooden diffuser to use for something.

thanks,
 
#23
mattIlikesound said:
Hi,

ive been interested in omni sound and have tried building one.
it didn't work out the FR was too offensive I tried to build the shape of the diffuser like the bella luna. I vaguely suspect that using a similar design to say the bella luna Jupiter requires a low crossover frequency between the mid and tweeter. maybe say 1khz??
However its hard to find a tweeter that can crossover that low, has anyone had any success? I think the bella luna uses a horn tweeter? I'm still interested in building a omni, tho probly only as a rear speaker as I still have an unused nice looking wooden diffuser to use for something.

thanks,
Click to expand...

It uses a high compression horn, that matches with the low end driver. Both are dispersed by the custom turned wooden lense. There are several horns which have good characteristics. I would suggest you go to Parts Express and look at what they have there to offer. They range from a 1" opening to higher sizes. If you follow the specs back to the manufacterer, you can see what the response curve looks like. Just be careful which one you mate up with, because finding one that low is not all that hard. It is in finding one that gives you a smooth response that is important.

As an aside, have you looked at the Motorola high end piezo horns? Don't bother with the dirt cheap ones, but go for the Motorola/CTX brand. They are extremely efficient and have great response, with the right crossover.
 
#25
mattIlikesound said:
thanks,
I don't know much about horn tweeters at all, I found this bigger tweeter (1 1/2 inch) that might be allright to xover low say 1khz http://www.tymphany.com/datasheet/printview.php?id=66 The jupiter I think used a bigger tweeter. my diffuser is like the jupiter. I tried using the diffuser with a higher Xover say 2khz but found the FR was bad...
Click to expand...

That is not what I am talking about. I am talking about a high compression horn. Like this one. They are extremely efficient, and is somewhat akin to what Duevel uses with their enclosures. Go to this page here, and travel down about half way, and to the left, you will see "Horns and Horn Drivers". There are 1", 1.4" and 2" drivers. Check them out, there are quite a few.
 
#27
The Pioneer HPM-200 tweeter might make an excellent tweeter for this project. Anyone with any experience with it used outside of the HPM speaker?

I've been trying to think of a good use for this driver and you may have helped my find the way. 🙂
 
#28
93db Efficient 8 ohm Omni??

Magnetar would this work as a 92.5-93db 8ohm efficient omni 2 way http://www.wolcottaudio.com/WA_omni.htm
The tweeter would be a Morel MDT33 or what ever they call it now days
The mid woofers would be http://www.partsexpress.com/pe/showdetl.cfm?&Partnumber=264-852
You could put a spiral port in the bottom of the cabinet
http://www3.ocn.ne.jp/~hanbei/eng-intro.html
All though I don’t quite agree with what Wolcott did for the tweeter dispersion.
I think if you had a bowling ball turn on a lathe you could make a nice lens on the upper half for the tweeter and keep lower half as is for the woofers.
 
#29
Hi Ben,

My 'minds-eye' does not like the tweeter arrangement either, and not just via imagination but from actually trying similar myself.

I found that a sphere or anything with a reflecting surface so 'flat' and close to a tweeter would set up a central HF reflection peak which became noticeable on cymbals, sibilance etc.

Just checked the spelling of sibilance - did not expect this -
http://www.urbandictionary.com/define.php?term=sibilance


Cheers ......... Graham.
 
#30
My experience supports Graham's conclusions. The sphere shaped diffuser will not work well for the tweeter. I've done a lot of experimenting with different surface shapes, diameters, spacing, etc. as diffusers for omni tweeters and the only thing that works, IMHO, is a concave cone shape, similar to the Duevel Bella Luna or Venus, that is when using a dome tweeter.

The bowl shape over a woofer will probably not help its performance and may even be detrimental. Again, the concave cone shows much better results, in my experience and testing, even in the midrange area.
 
#32
Hi,

I apologise, my last posts were abit confusing, I mixed up some of the names of the Duevel speakers.

Its good to see keen people regarding omnispeakers,
I have a diffuser that is very similar to the Duevel Venus, I'm interested in using it in a second attempt at making a omni speaker. my first attempt suffered bad colouration so I abandoned it.

I'd be interested to know what the Xover frequency is on the Venus, I suspect that maybe a low X'over is required between the mid and tweet in order to avoid colouration between the midwoofer and diffuser, say maybe around 1kHz?? And hence with the lower Xover a bigger tweeter is required to handle the extension?? I could be wrong though..I found a scanspeak 1 1/2 inch dome tweeter that might work, other people on the forum have also suggested horn tweeters..
 
#33
threads been quite for a while, was it something I said? lol

So I'm looking at a tweeter that can be crossed over low, say 1khz, and also has good sound quality and flat FR. To save doing a tonne of research is there any specific good tweeters that come to mind? i'd be using it with probly a 6" midwoofer.
 
#36
thanks guys,

that Fostex driver is very interesting (another seperate interesting topic - is it good to use without a Xover & with multiple drivers??)

Anyway regarding omni's does the driver have to be a certain size in relation to the diffuser? that Fostex is a 3" I noticed the Duevel uses only a 34mm HF driver in the Venus.
 
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