Altec 807 measurements

[robertbartsch]

OEM Machine tolerances for these drivers are very tight. I would expect that frams that do not fit on the factory pins are not up to aftermarket specs and these are likely to be sloppy specs when compared to OEMs.

Since Altec has been defunct for 15 years or so, I can't explain why anyone would be selling "Altec" diaphragms. Are these really GPA frams?

I thought Radian diaphragms are mylar not aluminum and they are supposed to take lots of power but I have not used them. If these are blown, one might wonder if the drivers have been hammered and need a re-mag.

Is the physical condition of your drivers OK?

I got a 2425 driver once that had a cracked motor so people do throw these things around, I guess.

[grumpy]

mMmmmMmm... carbon-looking residue...

(sounds like you've overcome your alignment/sizing issues,
but always good to clean the gap if there's any question of
contamination)

[Progneta]

Aren't the diaphrams in all Altec compression drivers aligned with two pins mounted by the factory in the driver body and the frams have matching wholes which means there is no "mis-alignment" potential issue for these units?

I just checked an Altec 902 and 802 that I have lying around and both have alignment pins for the diaphragms.

If I were you, I would remove the covers and check to see if the diaphragms are non-factory replacements. I'm not knocking Orange County but they routinely recommend non-factory frams which are typically dogs and which do not meet factory specs! OC does great work but you need to tell them excatly what you want.

The Chinese make great won tons but lousy frams.

I once bought a fram on ebay that was after market 802 diaphragm. It looked very similar to the original altec fram. So I went ahead an bought it and gave it a test. I found that it was different sound, but close. For 45.00, not bad but if you want the real deal. Get a GPA.

Check out attached pic. It is a quick little pic demo I put together. Basically these are my results from tinkering with am frams. The not so good sound pretty damn bad, and the pretty good are the closest I have heard to authentic original frams!

[Tom Brennan]

Radian diaphrams are aluminum with a mylar surround. I've used them in Altec and JBL bodies and they sounded good to me. But now that they're almost as expensive as GPAs one might as well use GPAs in Altecs.

[spkrman57]

That way my Altec/Great Plains compression drivers always work like they should!

Bill H. is great to talk to also!

Regards, Ron

[Earl K]

I was about to go crazy...It was a relief to discover that there are widespread problems with diaphragm alignment--

http://audioheritage.org/vbulletin/s...802#post249075

That is my original post that you are referencing and which discusses aftermarket replacement frams for Altec drivers.

I would not characterize the conclusions in the post as widespread alignment issues with Altec diaphragms. Rather, I would say that the aftermarket frams and old OEM tested in this post SUKed.

Radian diaphrams are aluminum with a mylar surround. I've used them in Altec and JBL bodies and they sounded good to me. But now that they're almost as expensive as GPAs one might as well use GPAs in Altecs.

- I won't argue the point with Tom about Radian diaphragms / but this is as good as I could get the FR to "look" with the same Radian diaphragm fitted into 2 different Altec drivers . I'm sure it sounds better than the picture.




- I was eventually able to fitup my old Altec 35480 diaphragms into 2 different 802D bodies // with the original phenolic-plastic loading caps reinstalled ( but no backcaps ).
- This is the performance those old Altec diaphragms were able to offer ( after a pad, a single pole HP and a RC contour circuit were all implemented ;



- That trace above shows remarkably linear midrange from a diaphragm that I had thought was "pooched" ( within a different thread ) .

- Below is the "worst" of the two 35480 diaphragms that I own / showing the effects ( before & after ) of a High-"Q" notch filter being applied (at around 7K) .



- So at this time, I can't agree with Robert that my old Altec OEM diaphragms "SUK" / but I will state that " the Radians have yet to prove their worth to me".

<> cheers

ps 1 ; I guess I should update that other thread sometime .
ps 2 ; The statement made within that other thread still holds true / installing diaphragms is not just "plug & play"
- ( even with test gear, getting a good fit-up can be very time consuming & it doesn't always occur ) .