Altec 291-16A Replacement Diaphragm. What are my options?

todd.brust

New Member
So I have had a pair of Altec 291-16A compression drivers that had a pretty thick coat of paint on them, so I decided to clean them up a bit. I had them apart and managed to damage a tinsel lead and the diaphragm is shot. I would like to find a replacement, and was wondering about my options.

A quick Google search brought up Great Plains Audio. Looks like they have the replacement I would need, but has no pricing information. Simply Speakers has replacement diaphragm for $50 and original Altecs for $130. The original Altec replacements do not look like what I broke today if that is any help. I also saw replacements on eBay for ~$20 with free shipping from China.


So what is the best route to go with repairing this compression driver? Anyone dealt with any of the mentioned options? Any other options? I was thinking about buying the $20 China replacement and at the very least do a comparison. Anyone dealt with Great plains?


As far as what I plan on using them for, No idea at the moment. I have a set of 805B multicellular horns that these attach to. Kind of wanted to play around with these but have no particular application yet.


Here's a couple of Pictures.

Before I messed up the Tinsel Lead
IMG_3743.JPG

The driver that I had already cleaned up. This was mostly done with a couple plastic razor blades and a little rubbing alcohol. Those plastic razor blades work great too! The original paint was almost perfect underneath that old paint. According to some documentation I found, these monsters were installed in 1970. They were used regularly with all of the original Altec electronics until 2015. Pretty impressive, especially for the original preamp and amplifier,

FullSizeRender (1).jpg


These are the pair of 805Bs.
IMG_3747.JPG

Thank for any help in advance!
 
The original Altec replacements do not look like what I broke
Original Altec replacements have been out of production for decades. It is known by Altec's trade name as a "symbiotik" diaphragm.

I also saw replacements on eBay for ~$20 with free shipping from China.
Absolute garbage and a prompt waste of 20 bucks, probably the same diaphragm simply speakers sells for 50.

So what is the best route to go with repairing this compression driver?
Two options, standard aluminum 288 type diaphragm, or the "Pascalite" 299 style diaphragm. You would need to replace them both to get matching response and performance.

The final option would be to purchase another 291 that still has a good phragm in it. By the time you add the shipping, this option will cost about the same as a new PAIR of GPA diaphragms.

You may find someone willing to attempt repair of the broken lead in conductor. There's no guarantee how long such a repair will last, or how long before any of the other break as they are old, used, and fatigued. The broken lead in is the common failure mode for these, and why those lead in conductors were eventually re-engineered.
 
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Unfortunately, I tossed the bad diaphragm. I attempted to fix the broken lead and was almost successful. Almost in the fact that I was able to solder and reestablish the connection but not durable enough to even gently handle the driver without the joint failing. There was a coating on it I could not get through well enough to solder and make a reliable joint.

Fortunately, I have a third 291-16a, So that would solve my issue of having a matched driver. I would just just don't want to have a worthless motor. I will probably end up buying the $20 eBay diaphragm for fun. Maybe do an A/B comparison and do some measurements for fun.

I did some research after my original posting and had a few questions. One thing I read was that the 291 and the 288 are very similar, if not the same, except the diaphragms. Is this correct? The other thing that was said that was a difference between the two was that the 288 had better HF response, but lacked power handling when compared the the 291. Is this correct? If so, would it be worth getting a set of new diaphragms to replace the set of original 291-16as, considering I don't really need the high power handling as this is not a PA system anymore. I imagine the extended HF would be desired, but would it be worth it to spend the money to do that? How much would the frequency response be improved assuming the questions I asked are true?

Thanks again!
 
One thing I read was that the 291 and the 288 are very similar, if not the same, except the diaphragms. Is this correct?
Yes.

The other thing that was said that was a difference between the two was that the 288 had better HF response, but lacked power handling when compared the the 291. Is this correct?
Yes

If so, would it be worth getting a set of new diaphragms to replace the set of original 291-16as, considering I don't really need the high power handling as this is not a PA system anymore. I imagine the extended HF would be desired, but would it be worth it to spend the money to do that?
Only you can determine the "worth" of any venture. Typically, large format components are not for the frugal minded or budget constrained enthusiast. Properly employed, Altec large format compression drivers are among the finest in the world. Changing the diaphragm out to the 288 style is going to net a HF roll-off in the 13.5khz - 14khz range where the stock 291 is rolling off pretty good by 10 - 10.5khz. The difference is easily audible, yet many enthusiasts will still opt to use a tweeter to fill out the top end with 288's.

Your other option is to keep watching ebay for somebody selling a used 291 symbiotik diaphragm in working condition, they do pop up regularly.
 
A quick Google search brought up Great Plains Audio. Looks like they have the replacement I would need, but has no pricing information.
There is pricing information. 16 ohm diaphragm

Your other option is to keep watching ebay for somebody selling a used 291 symbiotik diaphragm in working condition, they do pop up regularly.
A pair of Symbiotics sold on ebay recently. Ouch, I thought these weren't desirable. lol. Times have changed.

edit: This thread is from 2017. SORRY! doh.
 
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I was watching that auction too. Really surprising the symbiotiks went for that much. The same seller has a pair of Pascalites that sold for less

Makes me regret selling a mint pair of 291 diaphragms for 100 bucks a few years back.

Hey I like talking about Altec regardless of how old the thread is ;)
 
The best you will find are at Great Plains Audio in Oklahoma City. Designed and made by former Altec employees. THe diaphragms are much more capable than the 291 diaphrgms. Though they won't quite handle the same amount of power they are flat beyond 18,000 HZ with lower distortion and can Handle 30 watts RMS where the older 288 diaphragms could barely handle 10 watts RMS. Depending on which horns you have if you will raise the crossover to 800HZ they will handle almost 50 watts rms if you don't clip the amp . THe 291 diphrams really started to roll off just above 12 Khz and why you need 902 16 HF as tweeters to reach 20 KHz with EQ added above 16 KHZ or so. Only the 950 UHF Altec ring radiator could reach 22,000 HZ flat at 104 db 4 ft 1 watt.

If you need to reach down to 500 HZ, you will just need to back off the level 2 or 3 db below what a 291 would do. I used the 291 diaphrgms for out door use and the more modern diaphragms for in door use. USing MAC power amps with power guard or Urei limiter compressors set up properly kept experts from expensive Altec diaphragm replacements and my time didn't come cheap either. 90% of the systems I installed using Altec drivers and Mac amps with Power guard never had a diaphragm or woofer failure. Even after 30+ years. THe most problem prone were the 619 and 617 ceiling speakers. Small and large HF drivers and woofers the issues were very very rare. THe issues I had were with professional and theatre Klipsch speakers. THey never did perform as well as printed on the spec sheets. EV and JBL could be that way also in the 70's 80's and 90's....TAke out an EV woofer and install an Altec and it would be more efficient and reach at least a 1/2 octave lower in the same EV cabinet. 18 or 15/16 inch woofer. Even the 12 and 10 inch woofer performed very well,, But that 8" JBL woofer couldn't be matched and the 10 inch was so close to the Altec I would say in some cases the JBL 10" was better. Most JBL woofers could handle more power but were very limited in the lowest frequencies.
 
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Yer making me feel bad @elitopus, nah, not really. Those diaphgams work well in my 291 drivers that came without any.
Lol. No I don’t feel bad about selling them to you. I’m glad you’re getting some use out of them :thumbsup:

I ended up getting a pair of GPA phragms for my 291C that those came out of.
 
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