Constant Bandwidth Transducer

[richidoo]

Sorry for the late notice, but I just learned about this yesterday:

Don Keele will demonstrate his invention, the Constant Bandwidth Transducer audio line array speaker system TODAY at Part Express' Midwest Audiofest 2010 Speaker Design Competition in Franklin, Ohio.

http://midwestaudiofest.com/judges.html#Keele
http://www.midwestaudiofest.com/

After reading the original Navy technology briefs and Don's AES papers about the application to audio it seems like a very interesting path. It effectively eliminates off axis SPL attenuation in both vertical and horizontal planes, and eliminates SPL variation with distance in normal sized rooms. Unlike straight line arrays, there is no near field with these speakers, they actually sound a little softer as you get closer. The original invention was intended to emit sound in all directions with perfectly uniform intensity for improved sonar resolution. The original invention for sonar used a hemispherical piezo tranducer, with amplitude shading toward infinity at the base. This line array approximates that acting as a slice of a hemisphere, with drivers attenuated from 0 at the bottom to -12dB at the top to create the effect. All drivers play in phase.

All speakers are a compromise, I expect the flat in room frequency response of this speaker to be offset by phase distortion of more or less degree. Room reflections provide similar type of phase distortion, and more people seem to like it, so probably a benign effect here too.

More info on Don's website: http://www.xlrtechs.com/dbkeele.com/

Here's a picture of Don with his latest prototype, 2 way "towers" with Dayton aluminum 3.5" cones and probably laptop drivers for the tweeters as used in the research prototypes in his papers.


There is a "Church of God" here in Cary, NC that flies 3 huge CBTs above the congregation for PA, using ribbon tweeters and larger cones. I hope to check it out soon.
Rich

[rollo]

   Good find Rich. Looks and reads very well. Now how do they sound ? In theory they should kick some butt. Any Idea of price ?


charles

[richidoo]

He worked for Harmon, they have some patents on it. They are selling a JBL version that is a straight array with electronic phase and shading to simulate the curve. It's aimed at PA, not high end, but it's probably expensive.   As with any speaker, the driver quality and cabinet construction make the difference JBL pro makes good stuff. Afaik, the curved speakers are not available commercially yet. It's a little radical 

[Face]

   Good find Rich. Looks and reads very well. Now how do they sound ? In theory they should kick some butt. Any Idea of price ?


charles

http://techtalk.parts-express.com/showthread.php?t=218570

[richidoo]

Thanks a lot Face. There's some great info in that thread. Especially Rick's intention to pursue the design for Selah Audio. That is very exciting!  
Rick, have you a prototype working yet?
Rich

EDIT: Reading that thread a little more carefully tonight I think Rick was there, probably no chance to build his own in only 2 days.

[Selah Audio]

Thanks a lot Face. There's some great info in that thread. Especially Rick's intention to pursue the design for Selah Audio. That is very exciting!  
Rick, have you a prototype working yet?
Rich

EDIT: Reading that thread a little more carefully tonight I think Rick was there, probably no chance to build his own in only 2 days.

I had planned to go but couldn't get away. The demo pair was playing tonight in the shop. 
Plans to market these are evolving - not much I can say at this time. I didn't have any input on what was heard at the show (Behringer DSP) but will be doing some DEQX magic on them soon. 

[richidoo]

Awesome!     

Please keep us posted!

[rollo]

Thanks a lot Face. There's some great info in that thread. Especially Rick's intention to pursue the design for Selah Audio. That is very exciting!  
Rick, have you a prototype working yet?
Rich

EDIT: Reading that thread a little more carefully tonight I think Rick was there, probably no chance to build his own in only 2 days.

I had planned to go but couldn't get away. The demo pair was playing tonight in the shop. 
Plans to market these are evolving - not much I can say at this time. I didn't have any input on what was heard at the show (Behringer DSP) but will be doing some DEQX magic on them soon. 

Rick
Nice to see you posting here.  I'm considering a pair of subs for the Pipedreams. Any suggestions ?
Good luck with the project.

charles

[richidoo]

I was very fortunate to be able to hear these speakers in Rick's secret laboratory yesterday. They sound different, curious - in a good way. Every position in the room has the same general volume level, but they have excellent musical dynamics as with all arrays. They sound exactly the same standing up or sitting down, close up or far away. No lobing was audible from the 72 tweeters, 5/8" wide, <1" apart. High frequencies were clear and strong everywhere in the room. Walking past the speakers with eyes closed is a weird feeling, their horizontal dispersion is as good as the vertical. So imaging is very good, even with the non-audiophile electronics. I felt that the stock Behringer DCX and ATI amps limited their potential refinement and clarity, but I hope to hear them again after they've been Selah-ized. It is obvious that they have some fundamental advantages over regular speakers. We did not play them at high volume level, but supposedly they can really wail. We played some big band music at moderate levels. Intelligibility is excellent so there was no need to turn it up louder, but because they are so effortless with dynamics, it is tempting to really crank them, they are so relaxed and effortless. They just seemed to fill the room with music, but without the pressurized feel that horns and waveguides sometimes have. Very nice!  Thanks for the opportunity, Rick.

[richidoo]

Parts Express has created a DIY kit to build these speakers, $1980.

http://www.parts-express.com/cbt36/

http://www.parts-express.com/pe/showdetl.cfm?Partnumber=301-980

[Barry (NJ)]

Wow!!! That kit includes the enclosures, not bad for $1980.



They would look great flanking my LCD 

[BobM]

They look a little drunk!

[machinehead]

I think something more practical looking with internal dsp would be awesome.

[Face]

I think something more practical looking with internal dsp would be awesome.

It wouldn't have the same effect.