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View Full Version : LOADING CAPS: Oh No?



Skywave-Rider
12-03-2007, 04:43 PM
Been looking into whether or not I have loading caps on my 9844-8B HF drivers, and I think I do. It should have a 902 HF driver, but Altec docs indicate 2 versions, one that crosses over at 800Hz and the other at 1200Hz. The 902 with the loading cap goes for the speakers with the lower crossover point, like mine, to manage diaphragm excursion at lower frequencies I suppose.

Can anyone confirm what I have? I see the Tangerine phase plug. I guess someone removed the outer cover, because it is as pictured.

What do I do to go "plugless?" Can I order felts? I could not separate the cap from the diaphragm, does it need persuasion? I am scared.....

Pics below:

Russellc
12-03-2007, 05:02 PM
Yes, that plastic thing is a loading cap. It can be wedged apart from the diaphragm and and the diaphragm re installed without it. It will take shorter screws to do this, as without the loading cap as a spacer, the screws will be too long and will bottom out in the holes before they will tighten against the diaphragm. You will need shorter screws, and a felt to install in the back of the rear cover. If you dont have a rear cover, you will need to get one. All this stuff can be obtained from Great Plaines audio. I have seen loading caps in drivers crossover at 500,600 and 1200 Hz. The 902 8B usually had the loading cap and the good aluminum diaphragm, while the 902 8A usually did not have the loading cap, but also the "good" diapraghm. you may have a Symbiotic diaphragm, which does not quite have the high frequency extension of the aluminum version previously spoken of.

Also, yes, it needs a bit of
"persuasion" they are fairly snug. Call, dont Email, Great plaines and talk to Bill, tell him the numbers on your diaphragm and order the parts you need. It should improve your high frequency somewhat, as well as transparency. I have done this on all my altec drivers that had the caps, usually 808 8B, 908 8B, and 902 8B. Again, you will need rear covers after doing this, as well as the felts.

You are likely to find any of the drivers with any of those crossover points, that is determined by the crossover, not the driver. PA applications many times did use the loading caps, and sometimes (808 8B and 908 8B) symbiotic diaphragms to increase power handling. do not worry about this for home use, you will blow your ears out before the driver!

russellc

Skywave-Rider
12-04-2007, 10:13 AM
Thanks, Russellc! I appreciate the info. I will contact Great Plaines. Can you tell by looking whether or not the driver is a 902 of any incarnation? The numbers I can see look to be serial numbers.

After spending all night :( looking through many many posts and literature, and now an affirmation by EarlK, I'm pretty sure the diaphragms are aluminum:
http://www.audioheritage.org/vbulletin/showthread.php?t=18913
I read that there is a "light" version however, so I'll ask Bill about that. My speakers will be used for home Hi Fi and "easy" studio monitoring. Nothing too taxing, so the diaphragms won't be too stressed.

Best wishes.

Tom Brennan
12-04-2007, 12:43 PM
That's a 902 driver. Altec figured that since the drivers had loading caps and were inside boxes that the rear caps were superfluous, like the "Z" woofers that lacked the cosmetic magnet covers.

You can tell those aren't symbiotics by the surround, the symbiotics didn't use the folded metal surround but one of plastic.

Personally I never heard much, if any, difference with and without loading caps. Have fun experimenting but don't get in a dither.

Russellc
12-04-2007, 02:22 PM
Thanks, Russellc! I appreciate the info. I will contact Great Plaines. Can you tell by looking whether or not the driver is a 902 of any incarnation? The numbers I can see look to be serial numbers.

After spending all night :( looking through many many posts and literature, and now an affirmation by EarlK, I'm pretty sure the diaphragms are aluminum:
http://www.audioheritage.org/vbulletin/showthread.php?t=18913
I read that there is a "light" version however, so I'll ask Bill about that. My speakers will be used for home Hi Fi and "easy" studio monitoring. Nothing too taxing, so the diaphragms won't be too stressed.

Best wishes.
As Tom Brennan said, it looks like you have 902s with the good domes, so thats good. If you wish to remove the caps, contact great plaines. Just be very careful, magnets are very strong and diaphragms very delicate. My 902s had those light versions, they are fine, dont worry. I got all in a wad because I couldnt find the number listed anywhere, but Bill put it to rest when I inquired there. I could hear no difference between those and Bill's new replacements.
Have fun!

russellc

Skywave-Rider
12-04-2007, 05:00 PM
Ahahaha! Thanks Tom and Russellc.
Yeah, I don't want to get too obsessive. :)
Actually.......I called Great Plaines today and they're getting back to me with a price. It makes sense that they would not put covers over the caps inside a cab. I'm hoping the cost won't be out of orbit.

I think there's a great bunch of folks here.

Tom Brennan
12-04-2007, 07:36 PM
Yeah, Bill is great and his prices very reasonable. I paid about $200 each recently for a pair of 902-16 drivers and about $90 each for 902-8 diaphragms. It's as cheap to get diaphragms from Bill as it is to get Radians from Parts Express. Radians were a good deal when they were half the cost of Altec diaphragms but not now.

Skywave-Rider
12-04-2007, 11:26 PM
Tom, that must be the inside of one of your AS-21s. Gorgeous!

Tom Brennan
12-05-2007, 12:37 AM
Yup, ain't they pretty?

Russellc
12-05-2007, 05:07 AM
Yeah, Bill is great and his prices very reasonable. I paid about $200 each recently for a pair of 902-16 drivers and about $90 each for 902-8 diaphragms. It's as cheap to get diaphragms from Bill as it is to get Radians from Parts Express. Radians were a good deal when they were half the cost of Altec diaphragms but not now.
Very nice, I have never seen those before. How's the bass compared to the model 19 in your avatar?

russellc

Tom Brennan
12-05-2007, 08:09 AM
How's the bass compared to the model 19 in your avatar?

russellc


The bass is very strong and effortless but not quite as well defined as the Nineteens, boomier. Whether that's the room, placement or the nature of the speakers I don't know. In any event they're not so boomy as to be annoying, just a little.

What I really like about 414s is their fabulous upper bass and midrange reproduction, true Altecs.

Skywave-Rider
12-08-2007, 11:55 AM
I love those cabinets, Tom. Mine look so "commercial," but I kind of like that too. I placed the order with Bill of Great Plaines, and should be receiving the 902 covers, hardware, felts, etc., needed to chuck the loading caps. They even had some Altec stickers, so that's quite nice. I'll post some pics when it's all put together.