phase plug modifications

[louped garouv]

I've noticed some threads mentioning modification of older 244* compression drivers to include the newer style coherent phase plug designs...

Does anyone here have experience with these modified devices?
Would you care to share your thoughts, if you have any?

and if one was to be interested in such a modification, how would they go about arranging for this? DIY primarily?





The phasing plug shall be assembled of machined concentric exponential horns to eliminate phase cancellations, and it shall be further coupled to a tapered flared throat, the mouth of which shall be 2 inches in diameter.






The Coherent Wave phasing plug structure has four equal length passages to provide in-phase summation of diaphragm output at the 38 mm exit. This optimized configuration produces coherent acoustical power up to much higher frequencies than more conventional designs.

[more10]

Why do you want to do this? Alnico magnet with a modern (2446) phase plug?

I read somewhere on this forum that the reason for changing the phase plug design was to extend high frequency using beryllium diaphragms. Unfortunately all drivers up to 2446 have the long 183 Hz driver mouth.

If you want to use a truextent beryllium diaphragm I suggest you instead go for a 2447 or 2451 1.5" exit driver instead. On these drivers JBL removed (or shortened) the mouth, allowing for horns with better high frequency qualities.

Its a cool project though. I believe it can be done. You need one driver of each kind. Demagnitize both. Remove the phase plugs and take the rings apart. Scan the phase plugs using a CNC 3D probe (http://www.youtube.com/watch?v=o5Gl6YCrA8U). Design a new phase plug that fits in you old driver in a CAD program. Convert the CAD 3D drawing to CNC code. Make the new phase plug in brass with a CNC router. Assemble your driver. Magnetize. It wouldn't take more than a few hundred hours :-)

[louped garouv]

Honestly, the mentions of the modifications just stirred my curiosity...