DIY Omni Directional Speakers

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Did a search here and couldn't come up with any serious designs.

There are a few commercial systems out there that look to be well thought out (and expensive) but they all tend to be inefficient.

I'm thinking of using very high quality high efficiency drivers and building a three way. The bass should be easy, it will be down firing into a 360 degree reflector. The midrange will be crossed in at 300 and will fire up into a 360 degree reflector and extend to 3K and the treble will be a special 360 degree horn.

The goal is to drive the room with equal power response with little compromise in dynamics.

I have one working and it is pretty amazing. It's around 100db sensitive and measures (and sounds) darn near the same every where in the room with pink noise :D I've tried this before but not with the reflectors, I used multi drivers like bose - this seems to be far superior.

Wonder how a pair will sound?
 
I know you're looking for something serious, but I played around with this idea a coupla years ago. Made some MDF cones adjustable over a sonotube baffle. It never went anywhere and I had a name for them - The Screaming Banshees. :D

I didn't much like the 360 degree reflector and ended up with a very nice sounding takeoff on the Pluto. Not high enough efficiency though.

An externally hosted image should be here but it was not working when we last tested it.
 
Mostly I just didn't like the presentation - the image and soundstage floated around to the point of annoyance. I just wanted to yell out, "Stay in one spot!"

The screaming banshee came from not being able to tame some peakiness around 5khz - I mean it was the mount Everest of peakiness and I never could figure out where it was coming from. I based the size of the large cone on the fact that 1khz was pretty much maximum for omni radiation from an upfiring driver of any decent size and so everything above that would be reflected as the cone got smaller matching the increasing frequency wavelengths. It may not have been a viable idea, but it seemed to make sense.

I like your idea of using a 360 degree horn. I often wondered how to get the efficiency up and I never thought of that.

BTW, I only tried using the Fostex FX200 and the Fostex FT17H you see in the picture and a one day experiment with the PR170. Different drivers might have been a better choice. I'm honestly not sure how to improve it.
 
check this active thread

Magnetar,

You might want to check this active thread in the full range forum. There has been some interesting discussion of convex vs concave reflectors, waveguides, etc. The original thread started with an open-ended design "inspired" by one of the top end Dueval models. You might find something to spark your imagination!

Good luck,
Squib hexagon pioneer B20
 
FWIW, I've done three different omni or hybrid omni-directional/direct firing projects and I'm working on the 4th. The threads linked below describe their design and the process, including measurements, etc.

The first two below are hybirds, which in my expereince, are better than the full omni prjects because they have exceelent power response, but good imaging due to the front iring tweeters.
HOSS
Here are some measured vertical off axis frequency plots:
http://htguide.com/forum/attachment.php4?attachmentid=10374
http://htguide.com/forum/attachment.php4?attachmentid=10375
And a horizontal off axis out to 60 degrees:
http://htguide.com/forum/attachment.php4?attachmentid=10376
DSCF0131-small.jpg


This next project was the precursor to the one above, but usesa downfiring 12" subwoofer. Incidentally, I found no benefit to using a diffuser on the downfiring woofer.
Mentor
Mentor1Omni2s.jpg


I also did a fully omni project, but it never got paste a single prototype. It was never as good sounding as the other three mentione here, so was not completed. It was a 3way, and used a combination of concave cone diffusers and waveguides to create 360 degree horns:
Waveguide Omni
DSCF0950-a1.jpg


If you check out any of these threads, I suggest you start at the end and go back, becuase there was typically a trasnformation in the design concept fromhe beginning to the end. With a couple of these projects I did a lot of testing of diffusers and their profiles, sizes and heights and without a doubt in my mind, if you are going to use a diffuser, I suggest a concave cone diffuser like Duevel uses as the ideal shape for midranges and tweeters. Flat sided cones, dome shapes, etc. have much more significant problems, IMO.

I'm working on a third project that is a 3-way, has an up firing woofer, up and down firing mids and a front firing tweeter with crossover points at around 450hz and 3500hz. Here is a photo of the prototype.
An externally hosted image should be here but it was not working when we last tested it.
 
I heard a couple of dlneubec's designs last year and they sounded very, very good! :nod:






How ya doing Dan? I finally joined here and am starting work on a couple of amps. Very slow to get started though.

Someday you're gonna have to tutor me in the ways of diy speakers...

Cheers,
Gary
 
WARNING: HIGH VOLTAGE IS LETHAL. That's right it can kill you. Do not attempt the following idea if you are not comfortable with this, or if you are too confident.

If you're comfortable working with HI VOLTAGE, you could try using a plasma tweeter for the HF. Google plasma tweeter. They generate ozone, among other things, so this has to be considered, relative to human health.

Reminder: THERE IS HIGH VOLTAGE USED IN PLASMA TWEETER. DO NOT TREAT THESE LIGHTLY.


Did I mention that there are HI Voltages used in plasma tweeters and this can kill you if not handled carefully?

Just a possibility for omni-directional drivers

Peace,

Dave
 
dlneubec said:
FWIW, I've done three different omni or hybrid omni-directional/direct firing projects and I'm working on the 4th. The threads linked below describe their design and the process, including measurements, etc.

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Very interesting, beautiful speakers and great work!

Why have you abandoned a waveguide for the midrange? I'm using a high sensitivity B&C mid that has a rising on axis response, when I fire up at the waveguide (my waveguide is attached to the midrange's phase plug, a modified Parts Express conical round horn) I am getting great response out to 5K and 3 volt sensitivity of 98 db plus or minus 1 db 450 to 4K

Also the diffuser for the bass in project 2, you say there was no benefit - where did you crossover ? I have a huge 37" reflector I'm firing down into that reflects the waves out and up 360 degrees, the bass is a JBL 2226 15" woofer in a 27" diameter sphere and the mid is in a 10" diameter sphere above it. Kinda like a snowman :cannotbe:
 
Hi Magnetar,

Hmmm - maybe I'll slap in a pro driver on my 'ol Walsh 5 remakes. I would like to find one that has a fairly "deep" cone and will go to say 4 KHz and then cross over to the Heil AMT 1's. I point these out because I know that you have some of the Heils around and have used them before. These speakers work very nice for HT and not bad for audio. Not in the same league as your OB monsters - but I have space and spouse requirements to consider. Could give me a reason to finish these up and then play around with some "K" tubes!
 

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c2cthomas said:
Hi Magnetar,

Hmmm - maybe I'll slap in a pro driver on my 'ol Walsh 5 remakes. I would like to find one that has a fairly "deep" cone and will go to say 4 KHz and then cross over to the Heil AMT 1's. I point these out because I know that you have some of the Heils around and have used them before. These speakers work very nice for HT and not bad for audio. Not in the same league as your OB monsters - but I have space and spouse requirements to consider. Could give me a reason to finish these up and then play around with some "K" tubes!


Hello, If you can find one with a rising response and a phase plug just do what I'm doing. with the waveguide - I still have 8 of the big heils - probably need to sell 6 of them- the line array I built with them sucked - The K tube may be better with these omni's then my 360 treble horn based on what I've read......

As long as I keep this stuff in my bunker my wife doesn't care what I build ;)
 
I'm over at the PE site looking at some Eminence 12 inch drivers right now! They all seem to have a rise to them in the 2 KHz to 5 KHz area so that might work out well for me. I would still be using them backasswards and firing down into the Sonotube - which is sealed and stuffed about half full. I run the Pioneers full range and crossover to the AMT's with just a cap - so there isn't a lot of stuff in the XO to be getting in the way of things. The Alphas and Deltas look like they might be worth a shot! :D
 
Magnetar said:



Very interesting, beautiful speakers and great work!

Why have you abandoned a waveguide for the midrange? I'm using a high sensitivity B&C mid that has a rising on axis response, when I fire up at the waveguide (my waveguide is attached to the midrange's phase plug, a modified Parts Express conical round horn) I am getting great response out to 5K and 3 volt sensitivity of 98 db plus or minus 1 db 450 to 4K

Also the diffuser for the bass in project 2, you say there was no benefit - where did you crossover ? I have a huge 37" reflector I'm firing down into that reflects the waves out and up 360 degrees, the bass is a JBL 2226 15" woofer in a 27" diameter sphere and the mid is in a 10" diameter sphere above it. Kinda like a snowman :cannotbe:

Hi Magnetar,

There may be a confusion of terms here. When I say waveguide, i'm talking about the thing that the mid dome and dome tweeter are mounted in. What I call a diffuser is the thing they fire up into to reflect the sound.

A pro driver was the other alternative I intended to explore sometime. You lose a lot of on axis sensitivity when you fire a driver up or down, because the driver never transitions from playing in4pi space to 2pi. In my experience, you have a couple options to overcome that loss of sensitivity. One is to use two drivers firing at each other. Another is to use a waveguide/diffuser combination or in other words a 360º horn, like Duevel uses in their higher end stuff and I tried in my waveguide omni design. The third is to use a high efficiency Pro driver so that the 4pi and off axis losses are accomodated by the drivers inherent sensitivity. I think a cone firing up into what I call a concave cone diffuser is good solution with pro driver, if you can get the midrange close enough to the tweeter to not have CTC and its resulting issues. I played with a 13" dia. concave cone diffuser on my Mentor project (7" midwoofer) and found that it boosted the output slightly, extended the useable FR a bit and made for a little flatter roll off.

One of the other interesting things that most folks don't recognize is that when a driver is fired up or down and you are essentially listening 90d off axis, the driver has a natural roll off that typically drops any breakup modes a good 15-20db from what they are on axis, so they are much easier to supress. Though I haven't measured them to prove this, my hypothesis is that harmonic distortion also drops off axis, so you have a cleaner sounding driver in this type of application.

The problem I found with the mid dome, when using both a waveguide and concave cone diffuser was a horn-like sound in the midrange which did not sound natural to my ear, even though the FR with the crossover was essentially flat.

I tried diffusers (dome shaped, concave cone shaped, etc.) with various bass drivers and found they had little effect until you got up into the 1khz range, IIRC. One one project I tried them with a 12" sub driver and it had no effect, but the plate amp was set to crossover at 100hz. On the other project, I played with several diffuers and again , they had negligible affect, but they were crossing over around 600hz or so. You could see an effect up higher in FR. In my expereince with testing bass drivers, the spacing from the baffle to the first reflection surface was far more inidicative of the FR than any diffuser arrangement I tried.

In my experenice, diffusers can be beneficial (the concave cone type only in my testing), but like everything else in speaker design, present their own conplications, like causing the drivers to be separated by a greater distance than CTC rules would suggest are desirable, which presents its own set of concerns, as I mentioned above. Everything is a trade-off.

No way I could get away with a 27" wide speaker, with a 37" diffuser in my house. :smash: :dead:

If you've not seen this, you might find it very interesting.
http://jgbouska.tripod.com/audio/plan9.pdf

I'd love to see a picture of your creation!
 
Magnetar said:
AJ,

Those are close to what I have here in concept!

I'm liking the sound in mono but am afraid it will die when I go to two channels.

What was it that you disliked with the Screaming Banshees? How would you improve it ?

I'm not sure if anyone has linked to my project, over at the single driver section, but I am currently working on an omnidirectional speaker right now.

You can access it at at Hexagon Speaker thread. I am spending a lot of time and pictures on the construction proceedure as well.

Enjoy!


:)
 
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