JBL/ALTEC Diaphragms Question

[ngccglp]

Hi,

May I know whether the diaphragms for JBL 2420 and Altec 802 are interchangeable? They look quite the same to me.

Thanks.

[Earl K]

May I know whether the diaphragms for JBL 2420 and Altec 802 are interchangeable? They look quite the same to me.

- The gap width and depth of the magnetic assemblies may be the same / but I don't know that for sure. Certainly the two models show their common heritage .
- But, functionally, the diaphragms are not interchangeable ( acoustically & mechanically ) because Altec & JBL didn't want them to be for some obvious reasons .

- The problem is threefold .
(i) Diaphragm dome & coil weight is matched for each type of diaphragm to the magnetic strength of each specific drivers' assembly . This matchup effects all sort of performance parameters including among other things; HF extension , apparent smoothness of breakup modes or dampening as I call it. Even putting a 2410 diaprhagm into a 2420 magnet isn't recommended JBL practise for this reason ( though in my experience a 2410 diaphragm in a 2425/6 magnetic assembly is still smoother sounding than the stock titanium diaphragm ) . A 2420 has more magnetic assembly than the 802. The 802 is a closer kissing cousin to the le175/2410. Putting the heavier 2420 diaphragm ( meant for the stronger magnet ) into the weaker 802s' assembly should result in some real degradation in HF performance .

(ii) The locator pins for JBL and Altec are not set the same distance from the center of the phase plug. This makes drilling out the locator holes in the diaphragms' plastic mounting ring an unacceptable option ( IME ). The disparity in distance is enough that any "widening" of the hole must be accomplished as an oval shape , which is just too much drilling around a fragile ( expensive ) diaphragm for my taste .

(iii) The 3 holes for securing each diaphragm into the top-plate endup being mirror image to each other because of the locator pins .

:)

[Mr. Widget]

If you are hell bent on doing it, you can remove the locating pins from the driver. This is not an endorsement or recommendation, but that is how I would do it if I had some drivers to toss out and was bored one Saturday.


Widget

[John]

Did JBL not show the same part # on the dia. for both the LE175 + LE85 ???:blink:

I once spoke to Bill at great plains and he said you can interchange the two if you want, but you have to modify the mounting ring as has already been discussed.

[Earl K]

Did JBL not show the same part # on the dia. for both the LE175 + LE85 ???

- They are different part numbers .

- Here's a .gif collage from the 2003 parts price list, showing the different numbers.

regards EarlK