Geddes on Waveguides

[freddi]

thanks PB- got lost in those fascinating threads
--are there good (meaning affordable) online sources of foam and if so what specification/url?--are there some happy buidlers of hybrids with "basshorn" rather than reflex?

[Patrick Bateman]

Originally posted by freddi
thanks PB- got lost in those fascinating threads
--are there good (meaning affordable) online sources of foam and if so what specification/url?--are there some happy buidlers of hybrids with "basshorn" rather than reflex?

McMaster Carr -
http://www.mcmaster.com/nav/enter.as...52&pagenum=605

[freddi]

cool! - what size plug and sheets/cube would be useful for original Unity?

[Patrick Bateman]

For my waveguides I make the foam plug the exact same way I make the waveguide itself. The way that I do *that* is documented on both audiogroupforum and htguide. I basically lay it up layer by layer.

This is not optimum for the plug. Based on conversations I've had with Dr Geddes, there's issues due to the transition from layer to layer. But I'm not going to do what he does (cuts it out of a solid "bun" of foam.

Way too much work there! Expensive too.

[gedlee]

Lets keep in mind that below about 1 kHz (500 Hz certainly) the audibility of timing delayed aberration events falls off very fast. I would not think that foam would have any effect on LF devices. I try and control the diffraction only above about 1 kHz. I don't worry about it too much below 500 Hz.

The use of layers depends on how you hold the layers together. A lot of glue would be a real problem, no glue could also be a problem - getting this right could be tricky, which is why I use a solid block. It takes some doing to cut it, but I now get very clean pieces.

[Pano]

Originally posted by gedlee
It takes some doing to cut it, but I now get very clean pieces.

Electric carving knife? That's the classic for carving foam. Or hot wire.

[Sjef]

What kind of foam are you using ?

The foamplug seems interesting to me since I use some BMS4540ND driver in some 16cm diameter custom made waveguides (used from 4kHz upwards with 60db/oct crossover) They sound pretty good but still excibit some "sqeekiness" wich I have handled too some extend with my DEQX correction unit but I think an acoustical correction would work better in this case. Besides this little "sqeekiness" they sound more "real life" and dynamic then my ESS air motion transformers. The AMT's have got more inner detail though and sound more sophisticated. Though choise wich one is realy better, realy depends on the combination with the mid driver and amplifier choice, specially the BMS can sound awfull on some amps and brilliant on others. they both got there strenghts but at the moment I prefer the impact and lifelike dynamics of the BMS waveguides, getting rid of that last piece of harshness and a bit more air and detail would make it the perfect tweeter (and I have tried dozens of the most expensive high end stuff out there)

[Patrick Bateman]

Originally posted by Sjef
What kind of foam are you using ?

The foamplug seems interesting to me since I use some BMS4540ND driver in some 16cm diameter custom made waveguides (used from 4kHz upwards with 60db/oct crossover) They sound pretty good but still excibit some "sqeekiness" wich I have handled too some extend with my DEQX correction unit but I think an acoustical correction would work better in this case. Besides this little "sqeekiness" they sound more "real life" and dynamic then my ESS air motion transformers. The AMT's have got more inner detail though and sound more sophisticated. Though choise wich one is realy better, realy depends on the combination with the mid driver and amplifier choice, specially the BMS can sound awfull on some amps and brilliant on others. they both got there strenghts but at the moment I prefer the impact and lifelike dynamics of the BMS waveguides, getting rid of that last piece of harshness and a bit more air and detail would make it the perfect tweeter (and I have tried dozens of the most expensive high end stuff out there)

Source for the foam is listed in my post above.

BMS 4540nd is the same compression driver that I'm using in my foam loaded waveguides. You could probably steal my crossover and use it as a starting point. Heaven knows that I didn't come up with it on my own - it's a heavily tweaked version of the crossover from the Lambda Acoustics Unity. That xover was done by Tom Danley I believe.

http://www.audiogroupforum.com/csfor...ad.php?t=62789

[lovechild]

Hi,

I'm wondering if there is any waveguide/horn available (for diy), that would come close to the Gedlee OS waveguide.

I found the 18Sound XT1086 'Constant Coverage HF Horn' mentioned here and there, and the measurements look great, but how does it perform in reality...

Also the Monacor Wg-300 it supposed to work quite well with several dome tweeters, but it is rather small so it only works above 2kHz.

best,
LC

[gedlee]

I have for sale 90 degree OS waveguides for 1" drivers. They are $250 each. I can make any size, but the tooling gets expensive and I have to charge for that for a small order.