Plane Wave Tube Construction

[4313B]

JBL uses a smallish curved PWT that fits in the corner of a small room where their Klippel machine is also located. The shelves next to the PWT are stacked with every compression driver JBL ever made. I was not allowed to take a photo. At the time, the driver bolted to the PWT was a 275Nd.

The mouth of the vertical portion of the PWT where the compression driver is bolted on is at about waist height and the PWT curves where is meets the floor and extends out for a few feet where it ends. They might have others but the question didn't come up.

[grumpy]

I swear I've seen a picture of that thing somewhere...
or at least a trial version.

1audiohack... in the AES materials (1991 design and practice):
Common materials are 3 lb/ft3 (48 kg/m3) fiberglass, and 70 to 90 pore-per-inch Scott
reticulated foam (available from Scott Paper Foam Division, Essington, PA).

[4313B]

I swear I've seen a picture of that thing somewhere...

It's certainly possible. Don might have shot one during one of his visits. Heck, I might have taken one too and just don't remember.

[Rudy Kleimann]

It's certainly possible. Don might have shot one during one of his visits. Heck, I might have taken one too and just don't remember.

I seem to recall a JBL catalog or brochures from the '70's showing a picture of their driver test benches, including the compression driver bench with the PWT. It may (also) be an Altec catalog or brochure.

I want to say I saw it somewhere on the LHS site. It could be on an Altec site. If I had time right now, I'd do some sleuthing for it. Maybe tonight...

Grumpy, thanks for sharing here.

I've met 1audiohack and seen some of his goodies. He can do some really fine work, given the right tools and setup. What I'd give for one week with his TEF analyzer...

[grumpy]

Any bonehead can point to what more experienced people have published. I just hope
I point to more good than bad.

[1audiohack]

in the AES materials (1991 design and practice):
Common materials are 3 lb/ft3 (48 kg/m3) fiberglass, and 70 to 90 pore-per-inch Scott
reticulated foam (available from Scott Paper Foam Division, Essington, PA).

Many thanks.

[1audiohack]

It's alive1 It's alive!! It's alive!!!

I am still tuning the dampening after finally finding a way to pull it through with out tearing it.

I did some driver sweeps and after swapping eight drivers and two mic's, powering down the computer and amp, restarting anew and re-sweeping the first driver I tested a day later the single largest variation on a small peak was 0.4 dB, another small peak was 0.2 dB, the rest was a single line imposed on the original line from 200 to 22000 Hz,,, finally, I have a way to pick the gnat crap out of the pepper, and it's fast!

[JeffW]

Do you have adapters for that pile o' drivers, or just gonna machine something up?

[grumpy]

Nice job. It's that driver/pipe/mic interface, that you've nicely machined, that slowed me to a stop.

[Rudy Kleimann]

What's the input torque rating on that flange and tube?

Looks great! Hardly a "hack" job...

Is it a "Plain wave"?

Seriously though, is the tube I.D. 1.5" or 2"?

It's alive1 It's alive!! It's alive!!!

I am still tuning the dampening after finally finding a way to pull it through with out tearing it.

I did some driver sweeps and after swapping eight drivers and two mic's, powering down the computer and amp, restarting anew and re-sweeping the first driver I tested a day later the single largest variation on a small peak was 0.4 dB, another small peak was 0.2 dB, the rest was a single line imposed on the original line from 200 to 22000 Hz,,, finally, I have a way to pick the gnat crap out of the pepper, and it's fast!

[1audiohack]

The I.D. is 1.550". I just made a tapered aluminum sleeve and pressed it in the big end of 2327 for the 1" drivers so the original flare rate is kept until it reaches 1.500". I have a Delerin sleeve for the 2" drivers that slips in the throats up to the screens.

I plan to use a 2451 for critical diaphragm comparisons.

[ivica]

It's alive1 It's alive!! It's alive!!!

I am still tuning the dampening after finally finding a way to pull it through with out tearing it.

I did some driver sweeps and after swapping eight drivers and two mic's, powering down the computer and amp, restarting anew and re-sweeping the first driver I tested a day later the single largest variation on a small peak was 0.4 dB, another small peak was 0.2 dB, the rest was a single line imposed on the original line from 200 to 22000 Hz,,, finally, I have a way to pick the gnat crap out of the pepper, and it's fast!

This is really marvelous work.
Bravo Barry.

[pos]

You did it Barry!

Can't wait to see your measurements!!
Do you have a calibrated measurement mic?

[bstleve]

Great job !

Pos, stop dreaming, that will not fit in your flat

Bertrand

[pos]

Hey Betrand!
Do not forget the balcony
Well, I have no intention of building it: I prefer to rely on Barry's measurements