Altec 807 measurements

[sba2]

For my basement lounge, I put together a 15" two-way system using some vintage drivers (jbl d130f & altec 807 / 511b), along with Zilch's modified model 19 network (which I think has been optimized for BMS drivers).

After enjoying the system for a few weeks, I bought a mic to take some measurements...but was then surprised to see how very choppy things look with the 807s (which have new aluminum diaphragms from Orange County Speaker).

So, these being my first measurements (as well as my first project with compression drivers), I'm just wondering...Is this choppiness something one should expect from vintage Altec 1" drivers? Some of these dips and peaks are most likely audible, no? Can anything be done to make these drivers smoother....perhaps a crossover modification to help with the 3500 to 5500 dip in the Right speaker? Any thoughts!

Thanks

[robertbartsch]

I've used the Altec 802s and 806s a lot but not the 807s.

Anyway, replacement diaphragms are a big concern. Cheap replacement units can be had for $40 but they are not built to factory specs and they sound bad. I bought a used 902 with a cheap fram from Fleabay and it SUKs too.

I would ONLY use Great Plains Audio frams for Altecs as they have the original factory tooling that was acquired after the Altec company tanked.
Cost is around $90 each.

Cheap frams from communist China will always cause issues IMO.

[Zilch]

The crossover is a blend of Altec designs, actually.

807 behaves as I would expect; they won't "push" beyond 14 kHz. I presume those are 8-Ohm diaphragms.

Swap crossovers between left and right. If the hole in the response in the right between 3 and 7 kHz remains, the diaphragm in that one is misaligned....

[robertbartsch]

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.

[sba2]

Thanks for your replies...I think you guys might be on to something here.

Prior to reading your posts, I did some parts swapping and found that the right side dip persisted after swapping the left and right frams. I also mounted the left driver onto the right speaker, in order to see if there were any issues with the signal, the horn, or with my wiring of the crossover...and there were none. So something's up with the right driver, or its alignment.

I didn't even think about the alignment, but now that you mention it, the non-factory frams from Orange County didn't fit when they arrived. The frams straddled the alignment pins okay, but the mounting holes on the ring were off so much that I had to widen them with a drill. I guess that's what one gets for $85 pr. Maybe they should send fortune cookies along with those frams...and print the invoice on a little green guest check.

I'll loosen the fram mounting screws and try adjusting while watching on RTA.

Thanks again

[robertbartsch]

....I would try to negotiate with OC since these were real Chinese dogs. You might try to send the entire drivers back to them and ask them to use only frams from Great Plains Audio.

Since the Chinese frams have been drilled by you this may be an issue for them.

I ordered a pair of JBL 075 frams from them and one was damaged in shipping. Eventually, they replaced the bad fram for no charge.

The fool proof method of getting the real deal would be to send the 807 units to GPA and ask them to install a fresh pair of frams. They even re-magnitize the magnets in your drivers for no extra charge!

Properly re-built these babies will sing sweet!

[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.