Phenolic fram of the 290

[Panomaniac]

Will the phenolic diaphragm of the 290 fit in the 291 driver? Or is it a different beast?
I'd like to hear one, just for fun.

[Old Guy]

Nope it won't fit

It's been about 20 years since I have done one, I think it's a matter of the 290 needing a larger mounting ring. Physically just won't fit.

I would check with GPA as I am having trouble picturing the difference in frams, But remember for certain they don't fit.

[Audio_by_Goodwill]

I asked a similar question at one time...... seems like I was told the 290 has a bigger gap. Somethings bigger any way. Going the opposite way will physically fit, I believe, but won't work well sonically/magnetically.

[Audio_by_Goodwill]

I found the reference where I inquired....... I think I've read it elsewhere, too.

http://www.hostboard.com/forums/alte...ml#post1769328

[Steve Schell]

As I recall, the diaphragm mounting screws are on a larger diameter than with the 288 and 291. The 290 phenolic diaphragm has a larger outer compliance, requiring a larger diameter mounting ring. I'm certain this is the case with the large format JBLs, but believe it is also true of the Altecs.

[Panomaniac]

Thanks for posting that, I couldn't find it.

Makes sense, given the specs of the 290 drivers. 4 ohm coil and rated at 100 watts above 300Hz. I'd still love to listen to one on my 300Hz horn. It ought to get insanely loud - at least!

[GM]

It's similar to the difference between a Symbiotik and alum. diaphragm in that since they are pistonic over a wider BW the horn's actual gain BW is more accurate/'full', but the trade-off is a faster/nastier sounding HF roll-off, so need to be XO'd to a tweeter horn for best performance in a wide BW/high SQ app. On a 300 Hz horn they really are a 'living voice' reproducer through the ~300-3 kHz BW they were originally optimized for.

GM