Altec Compression Driver ID

[xanadu1797]

I picked these up from Craigslist this weekend. The seller told me they are 4 ohm voice coils but I forgot my multimeter and can't confirm.
I suspect them to be Altec as they came with 805b horns.

Thoughts?

 

[BillWojo]

Altec large format alnico drivers. Nice haul.

BillWojo

 

[xanadu1797]

Well, I paid for them and it wasn't exactly a steal but I figured it would probably not lose me any money (famous last words).

 

[Monoblockguy]

Those look to be 1970s or maybe a little earlier type 808 compression drivers.

They feature a much larger magnet and voice coil assembly than the home audio version 804s.

Probably worth $200 local. As much as $400 on eBay.

(edit) also note yours are missing the badges.

 

[bowtie427ss]

288 G or H/291B. You won't know for sure without seeing the diaphragm load.

As Billwojo mentioned they are large format, not anything from the 800 series.

They would be circa 1975-1980.

 

[g..v]

If you need two hands to lift 'em, they're large format, usually in the 20+ pounds range. Small format weigh much less.

 

[xanadu1797]

Ok, well I discovered that the voice coils are blown on both units. They have 288 diaphragms in them which seem to have been replaced once already. Since I don't have the labels from the cover, is there any other way to tell which version of the 288 driver this is? The "H" looks awfully similar to the "G".

 

[Sam Cogley]

Drivers are the same. G and H should only designate the diaphragm.

 

[twiiii]

Do they have the orange tangerine phase plug? There were 5 different diaphragms for the drivers. A low powered light weight diaphragm in either 8 or 16 ohm. 15 watt rating. There was the 291 16 ohm version with red plastic surround. Then the 30 watt up graded diaphragm in 8 and 16 ohm. All three basic diaphragm power handling can be almost doubled by raising the crossover frequency to 750 HZ. I use to drive a single 291 with one channel of a Mac 2120 with power Guard and never had a failure. I'd drive the same driver in Pairs with 2150's and never had a failure. I could drive three with a 2250 with power guard without failures. The 30 watt aluminum diaphragm could be driven by 75 watt Mac or 80 watt QSC amp with out issues either. But don't try it with Crown, Crest, Yamaha or other commercial amps the diaphragms won't last one minute. And tube amps will kill just as fast as regular SS amps.

 

[elitopus]

288G/291B are metal phase plugs

288H/291C are tangerines

Besides the diaphragm load, the 288/291 of this series are the same

 

[BillWojo]

There is only one place to get replacement diaphragms, all of the cheap ones are junk. Great Plains Audio is owned by a fellow (Bill) that used to work for Altec and he purchased all the tooling when they went under. So you get authentic Altec parts, not some Chinese knockoffs.
As far as size, BIG! and they are about 30 pounds each.
Where do you live? I'm from Burlington, nice to see a fellow Altec fan close by.

BillWojo

 

[elitopus]

Pretty sweet they came with the 805 horns also.

OP: What are your plans for these?