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

42520

42521

42522

[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.... :blink:

http://audioheritage.org/vbulletin/attachment.php?attachmentid=32741&stc=1&d=1212357423

[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!

[sba2]

I bought the diaphragms over the internet months and months ago. OC didn't perform any work on the drivers.

****

In trying to adjust the alignment on my non-factory diaphragm for the Altec 807, I had to widen the screw holes and the registration holes.

Using RTA I was able to get a half-way decent looking curve by using both hands and six fingers, but everything went to pot when I began tightening the screws...even slight turns would create moderate dips and/or peaks on the RTA.

I know I didn't start with the best frams but, after seeing how minor adjustments cause the response to dance around, I now have a little less confidence in this two-pin / 3-screw design. Perhaps it works fine for most applications, but my hunch is that it doesn't guarantee the optimal alignment needed for home hifi. Even with factory diaphragms, I would now find it hard to believe that one could just drop them in and have 100% optimal alignment. I have no idea whether GP measures for such a thing when they do a replacement.

[robertbartsch]

I would call Bill or Steve at GPA and tell them what you have done and ask them about your issues and questions.

I've been using them for a long time and these guys are GOOD. They have the only original Altec tooling.

If you are not sure about the origin of these drivers it is all the more reason to send the drivers to them since they re-mag the motors and install the frames free.

OC charges $25 each for a re-mag I beleive.

[sba2]

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

http://audioheritage.org/vbulletin/showthread.php?p=249075&highlight=802#post249075

[robertbartsch]

Hi SBA:

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.

Frams are manufactured using jigs which align the multiple parts (voice coil, former, alum fram, plastic body, alignment holes, etc) so multiple production runs will turn out similar units.

One thing we know about aftermarket frams is that they are manufactured using jigs that did not originate from the OEM factory. In addition, the materials and essembly methods for aftermarket frams will likely differ from OEM.

Anyway, there are a lot of variables in the test including the condition of the driver cores and their magnet motors. If your drivers were not purchased new, you have no way of knowing if they were ever abused so the only prudent thing is to start with a fresh re-magnitization of the motors and new OEM frams.

Since Altec is now defunt, your only viable choice is GPA IMO since they are former Altec employees and they have the original tooling that no one else does.

[sba2]

Robert, I exaggerated when I said "widespread problems", and you're right about there not being anything about brand new GPA diaphragms in that thread; but, it's fair to say that both Mr Widget and Earl K emphatically concluded that vintage drivers were not simply plug & play items...that they must indeed be measured...and that, even then, issues may persist.

I'm still in the process of trying to get my diaphragms adjusted. I can hand-hold them in order to get a decent FR curve, but I can't lock them down in place without the curve deteriorating. So I'm really reluctant to just throw a couple hundred at some new vintage diaphragms from GPA. I'll tinker some more and see what develops.

I've also been checking into driver replacements and came across a site with side-by-side comparisons of some current drivers--

http://sites.google.com/site/drivervault/driver-measurements/acoustic-elegance-td12m

The Beyma cp385nd has nice FR and low distortion ($260 delivered from US speaker). Another driver that seems decent is the B&C de250 ($125 delivered from PartsExpress, which also has a 45 day return policy). Their liberal return policy is appealing, should the driver not sound or measure decent. The BMS 4550 is also compared. The GPA 902 isn’t included (yet). I wonder about the cost of a new 902...I can't even find any curves for it on the GPA website!

[robertbartsch]

Do your aftermarket frams have a metal ring on the bottom? I just checked some OEMs that have this.

...Not sure why you have alignment issues when tightening but it seems like it could be a bad/warped fram body. Are both of your old OEM frams burned out?

There is no reason why your units cannot be brought up to factory spec unless they were damaged after they left the factory.

There is a reason why JBL & Altec compression drivers are ledgendary and the other brands are not.

[Zilch]

I wonder about the cost of a new 902...I can't even find any curves for it on the GPA website!:hmm:

[robertbartsch]

I bought a pair of frames from GPA last week and told them about their web cite issues including the spec sheets that cannot be viewed with the new version of Adobie..

They never publish prices there anyway.

o

[sba2]

Do your aftermarket frams have a metal ring on the bottom? I just checked some OEMs that have this....Are both of your old OEM frams burned out?

My aftermarket diaphragms from OC speaker have metal rings and resemble the images that I've seen of OEM aluminums, but without all the numerical and other markings. I don't think mine are the same as the lower priced ($45pr) Hong Kong ones, which appear to have different surrounds. My 807s, by the way, were DOA with damaged Symbiotic voice coil wires...so I was looking for something to just get the 807s up and running.

For the Altec 1” drivers, OC speaker carries Altec ($240pr delivered), Radian ($265pr), and aftermarket ($160pr) diaphragms. The prices have gone up! I recall looking on the GPA site and seeing that the older drivers would also need a conversion kit specifically for GPA's diaphragms ( I later realized that this is mostly about changing the wiring connectors, something I could have done easily without the kit).

Anyway, both my aftermarket diaphragms needed hole widening in order to insert the screws; and both then performed okay on one of the drivers, but not the other. I don’t know why. Both drivers showed no obvious signs of abuse. I did notice that the problematic driver had a lot more carbon looking residue in the gap; and, in the end, that driver required a diaphragm with even larger screw and registration holes, as well as a lot of fricking adjustment.

The 511b horn also required some tinkering...or more precisely, a Sawsall to remove those sectoral vanes that were ringing like everyday was a Sunday. That wasn’t quite enough to tame it however, and I deadened it further by applying self-adhesive SBS roofing base (left over from the roofers). Because of the whale-tail curvature of the horn and the stiffness of the SBS base, I scored the base extensively with a utility knife after it was on the horn, and then gave it a quick warm-up with a propane torch in order to make sure that it adheres well. My 511 is just a simple radial horn now, and sounds like a Bongo when tapped...no more delayed ringing.

Overall the system is starting to sound very enjoyable, in spite of its current lack of VHF...and it’s fun to be learning on “legendary” equipment!

[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]

:homer: 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 (http://audioheritage.org/vbulletin/showthread.php?p=249075&highlight=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.


http://www.audioheritage.org/photopost/data//500/Radian_in_802_or_902_Altec_1.PNG

- 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 ;

http://www.audioheritage.org/photopost/data//500/medium/802_35480_Diaphragm_2_Sammi_Horn_EQed_notched.PNG

- 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) .

http://www.audioheritage.org/photopost/data//500/802_35480Fram_1_Sammi_Horn_EQed_no-notch.PNG

- 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 ) .