Beyond the Ariel

[Lynn Olson]

Interesting. Of all the coaxes, the Beyma's look most interesting. Their 12" bass drivers look pretty good too.

[ShinOBIWAN]

Another interesting Coax:

http://www.sabre-international.com/c2/uploads/03521.pdf

[audiotux]

another one : IMG Stageline SP-30PAX

see www.monacor.de PA-Coax
or in the new Klang+Ton

[Variac]

The original Bastanis Promithius used a Beyma tweeter with their Eminence woofer I believe.

[Variac]

Several pages back, we had an interesting proposal for a custom driver with a 4" VC assembly and a coaxially mounted ribbon where a pole-piece would normally sit. The ribbon could sit fairly deep in the woofer, almost touching the interior of the cone, or it could extend further out on a cylindrical pole-piece. The extended version would be compatible with your suggestion for local felt damping near the center of the cone, where it could do the most good.

I think that there probably isn't room for the ribbon too deep, as the ribbon tweeters are pretty deep themselves. I was however suggesting this as a DIY experiment. It would require one to remove the dust cap in the center of the driver. Anyone who has used one of the kits to replace a driver's rotted suspension can tell you that this is pretty simple. Then glue a piece of pipe, PVC aluminum, cardboard, or whatever comes in an exterior 4" diameter onto the solid steel polepiece which is just inside where the dustcap was. Add some damping inside and then glue the tweeter into the end of the tube. A clever way should be found to try different lengths of tube, but I suspect that getting the tweeter as close in as possible is probably best. The tube could be then wrapped in felt. A 3" tube and tweeter in a 4" voicecoil would probably give a lot more room for experimentation, but even if you remove the tweeter flange I can't remember if it will be small enough- will check This scheme seems a bit more doable now that we are aware of 12" drivers that can go up to 4k or more...

I checked: Darn! 92dB / 2.83V / 1M not efficient enough! Well.... the Phy drivers use piezo tweeters....

OK the Aurum Cantus 2si ribbon has a diameter of 4-5/16" (110mm) but the flange could be removed and easily machined to less than 4" without damage as you can see from the link below.It's 96 db

http://www.e-speakers.com/catalog/au...si_4284956.htm


Hmm I wonder if the pressure would damage it? I have a 2si 4.5" laterally away from a 15" woofer and no problems so far...

[planet10]

Originally posted by Variac
the ribbon tweeters are pretty deep themselves

Isn't that mostly transformer?

I have a set of AC here with custom 104.5 mm bezels... it could be smaller yet, 93 mm by my drawing.

dave

[johninCR]

To make things more simple, why can't a good efficiency dome go in a 90deg constant directivity waveguide to match the efficiency of the woofer. My limited research and experience with waveguides tells me that a dome with a CD waveguide in front would be easier to get right than a CD WG for any other driver. You want the wave front edges perpendicular to the waveguide sides. Typically a lot of trouble or size goes into getting the necessary spherical wavefront shape entering the waveguide. With a dome the wave starts out the proper shape, so no throat is needed.

The only compression driver I ever opened up had a dome membrane in it producing the sound, and what a cluster f#$& the sound had to go through to get to your ears. Radiating from a dome straight into say a 90deg WG seems a whole lot simpler to me, and if you can get the woofer up to 4-5khz, the WG doesn't need to be very big. Radiating 94db/w/m into half space has to get close to your efficiency goal radiating into a 90deg CD WG. With the CD WG you should even run into far less problems related to the woofer operation interfering with the tweeter operation, IM etc.

The whole thing seems so simple to me that there must be some basic flaw, unless the manufacturers are just out to sell you the high priced compression drivers. Why else would they insist on strapping a 106db/w/m compression driver to a 99db/w/m woofer. Let's make our own 99db/w/m tweeter.

Am I that far off the mark?

[planet10]

Here's a picture with dimensions

[fiacono]

My small contribution...

I would like to contribute but I have very little speaker knowledge but a reasonable ear for music (musician). Most of this stuff is over my head.
I've noticed the TT Alnico is edge wound, no information on the ceramic TT VC construction (round wound?).
All the coaxes mentioned here (unless I've missed some) are not edge wound. Some of the pro sound non coaxes are edge wound from the same vendors with coaxes.

Not sure if the VC construction has any relevance, but I must say the 12" TT alnico have amazing mids.

Regards
Frank.

[Variac]

Dave, 93mm doesn't surprise me. It could be done. You are Mr. Phaseplug so I'd think you'd be tempted. A nice turned wood nose tht tapers from 100mm to 93mm,that fits into a 4"tube which attaches to the polepiece. The tube could just have a piece of steel inserted on the inside end which I would presume would snap right onto the magnatized polepiece. Carefully!!! like the guys that use a socket wrench socket as a phaseplug.

At the moment I cross to the 2si at about 4500 hz and I like it!
At 96db it probably is about the right efficiency to work with 97 Db drivers. People say that padding down a ribbon hurts the sound. I don't have to pad mine down because it matches the mid efficiency so well. That is really elegant IMHO.

I think most of the rear of the ribbon is magnet. It's just that additional bump which I think is the transformer, but I'm just guessing.

I don't know if any hemp 12" drivers have 4" coils though.
Quite likely the Super Boy 15" with cast basket does, but ceramic magnet and how high does it go?

Might have to use the eighteen sound..or some other for an experiment. I don't have measuring equipment.

http://www.6moons.com/audioreviews/b...metheus_2.html


John,
Here are the new Bastanis tweeters. As you mentioned, they are the insides of a compression driver made to work with a custom horn(below link) I do believe that he leaves the backplate off to get dipole action! The 6 moons site shows this. They look like they could be used as dome tweeters, but without compression, their efficiency might be as low as other dome tweeters.I don't know Also compression driver magnets are pretty huge. They wouldn't fit in a phase plug... All commercial dome tweeters that I have found top out at 93 dB which really isn't enough for what Lynn wants. I think he'll accept 97 dB but I think he dreams of 99 dB

http://www.bastanis.com/catalog/index.php?language=en
http://www.bastanis.com/us/atlas.htm