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808-8A : midrange driver ...

24.140.98.34

Posted on April 4, 2015 at 07:01:09



Got re-magnetized 808-8A back from GPA.

Bill told me these drivers don't have much output past 10KHz and start dropping off around 8KHz.

He suggested using the 800Hz crossover point with 811B horns.

I set up my XM9 for 800Hz and added a Foster horn tweeter crossing over first order at 13KHz.

This was OK except for a huge 9.5dB peak at 2KHz that was about 1 1/2 octaves wide.

I used a series cap and coil across the +/- of the 808-8A and it took out the 2KHz peak almost entirely.

-3dB point measured in room 13250Hz at my listening position.

The 808-8A/811B/Foster combo sounds very nice once dialed in.

Also added a powered sub from 80Hz to -3dB point of 38Hz.

I got Tuba 18 plans, not started on those yet.

Might do a mock up with cardboard since they seem a bit more complex than a simple ported box.

Edit: added some small wooden baffles to mount Foster horns to 811B.

Still debating need for active EQ and upgrade to 55-1220.

 

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RE: 808-8A : midrange driver ..., posted on April 10, 2015 at 19:09:28
Bikeryder
Audiophile

Posts: 75
Location: MontrealWest
Joined: March 27, 2006
Also have an 808 driver paired with a 511 horn, thinking about sending mine to GPA for an 802 conversion. Did you give any thought to this option?
Cheers

 

RE: 808-8A : midrange driver ..., posted on April 10, 2015 at 20:12:38
The only thing I discussed was upgrading the diaphragms, but Bill at GPA thought it might be better to sell the 808's and go with new GPA 802-8G alnico drivers.

I would probably have to sell the 808's for a $$$ loss, so I will keep them.

Adding in a horn tweeter or whatever for the high end is no problem.

Got some 414's and dual 31 band EQ on the way, that will finish off my Altec system for now.

 

RE: 808-8A : midrange driver ..., posted on April 14, 2015 at 12:23:33
Bikeryder
Audiophile

Posts: 75
Location: MontrealWest
Joined: March 27, 2006
Also have a pair of badly abused 802s from the '70s, need new diaphragms, also possible remag, and new connectors. Have to call Bill tomorrow to find out if it's worth the time and money, or just go with new GPA 802s.
Cheers

 

RE: 808-8A : midrange driver ..., posted on April 14, 2015 at 20:18:46
New GPA diaphragms are about $180 a pair and a new 802-8G is about $260 each.

Got an Alto AEQ231 31 band graphic EQ hooked up today.

Took me a few minutes with the PC RTA to get a flat response in room and it is super quiet using unbalanced RCA in/out jacks.

No more trying to EQ at speaker level.




 

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