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View Full Version : Need JBL and Altec advice



gottaJam
03-21-2006, 07:35 AM
Hello everyone. It has been a long time since i have had a chance to get online, so you probably will not remember me. I started a new business last year and it's VERY DEMANDING. anyway, i have a pair of JBL SR4725 series speakers. Subs are fine, but diaphragms in both horns are bad. I am also missing one driver (2426h). Should i go to the trouble to fix these or spend the money on other ones? Also, i have a pair of custom built cabinets (probably over 100lbs each). They are setting in our living room and my wife doesn't like them. They have earned the name great whites (they are large and white) from all of my friends. They house a 411-8A sub and 511B horn with 902-8b drivers in each. One diaphram is cracked all over, but the other is working fine. There is no crossover in these cabinets and i am not sure why. What should i do with all this? I really want to get the SR4725 speakers going and maybe sell the others. If anyone has advice or parts to sell please let me know. I am lost as a goose:dont-know. My email is [email protected]. Thanks!:D

Mike Caldwell
03-21-2006, 07:56 AM
Hello
If thinking of the right cabinet those have a 2226 15" and a 2426 driver on a 2370 horn. If all you need is a diaphragm for the one driver and a complete driver in the other they are worth fixing up. Look for a used driver on Ebay actually look for one without a diaphragm as it will sell for less and then get two new JBL diaphragms part# D8R2425 or D8R2426 and both drivers will be good as new. It wont matter if you get a driver without a diaphragm that says 16 ohm on back cover, the diaphragm is the only difference you could also get a 2425 driver. they are the same as a 2426 only the 2426 has a removable mounting flange to use it as a thread on driver.
The biggest weakness with the earlier SR series cabinets was the crossovers they would developed cracked solder connections and become intermittent.

You mentioned that your Altec cabinet had no crossover in them, how are the drivers wired? If they are just paralleled with the woofer I'm surprised they both are not blown.

Mike Caldwell

gottaJam
03-21-2006, 08:10 AM
Hello and thanks for the reply. For some reason it said my message couldn't post so i reposted this in the general forum. Sorry if that confuses anyone.

I actually found a place that sells generic diaphragms on ebay for $50.00. should i avoid them? If i decide to replace the crossovers, which one should i use?
The drivers and woofers are both wired in parallel, but i am not sure this is how they were wired when in use. I believe someone took the crossover out before i got them. would it be worthwhile to fix these?

thanks:)

Mike Caldwell
03-21-2006, 08:25 AM
Hello
The generic diaphragms will work......but can vary greatly in sound quality from diaphragm to diaphragm within the same brand and most will agree that the generic replacements just sound as good as the real thing. The exception maybe Radian replacement diaphragms but they cost just about as much as a JBL.

Your Altec cabinets need crossovers, there's no way you can run horn drivers directly paralleled with the woofers. If you don't want to build you own you can buy basic generic crossovers from MCM and Parts Express. Those will work and sound good but not as good as a crossover and impedance network designed for those drivers. If you go with a basic crossover look for something at 800hz to 1000hz if you plan on driving the cabinets with some power, for lower power use you could go down to the 500hz to 800hz range. You will also need to the impedances of the woofer and horn driver to get the correct crossover. Diaphragms for the Altec drivers will be harder to get, Great Plains Audio may beable to help.

Mike Caldwell

gottaJam
03-21-2006, 08:47 AM
How much would it cost to build a crossover vs buying one? Which setup do you think will perform the best when both are finished, the JBL or Altecs?

Thanks

Ragen Nash

Zilch
03-21-2006, 01:13 PM
http://www.jblproservice.com/pdf/SR-Series/SR4725.pdf

http://www.jblproservice.com/pdf/SR-Series/SR4725A.pdf

Keep for what use?

moldyoldy
03-21-2006, 07:01 PM
Your Altec components are essentially what they used in the 9846 monitors, which used a 500Hz XO, the N501-8A, which are common on eBay for resonable $. The 411 is an awesome woofer, but doesn't do well much beyond 500Hz. Those N501 XOs also have HF attenuation to match to the 411, which you'll want to add to a storebought XO, if you go that way.

If you replace the diaphragms, I'd go with the Pascalight ones from GPA, especially for a 500Hz XO point....those $49 specials don't like it that low....for long.

The 9846 was an excellent 2-way monitor, and well-worth reviving.

hapy._.face
03-21-2006, 07:08 PM
MOLDY!
Good to see you! Always a pleasure to read your posts. Thanks!

gottaJam
03-21-2006, 07:54 PM
Moldyoldy, sounds like you prefer the altecs over the JBL. I will be using these for small DJ gigs and the altec cabinets are just too big and heavy. Maybe i should just sell them. Maybe not. Dang audio addiction..... it was once car audio and now it's becoming home audio. better buy my wife a bass boat so she has some toys.

gottaJam
03-21-2006, 07:59 PM
I occaisionally dj for small parties and wedding stuff. The altec setup is just too heavy to tote around. Thanks for the manuals. I am going to get the JBLs back in the work force.:)

Steve
03-21-2006, 09:07 PM
The attenuator that moldyoldy spoke of is Altec #30904.
It is necessary because the woofers are a lot less effecient.
I might have one or 2 in the attic.... or if I can read the printing....
the schematic.
I love the Santiago's I have at my mother's house.
I also have a pair of Barcellona's at a friends....The problem with those is they have the black tar surrounds instead of the foam. The bass is limited on them. Gotta pull them and send them to Bill.
Here is a link showing the Santiago and Barcelonna's
http://www.lansingheritage.org/images/altec/catalogs/1975-home/page03.jpg

Steve

gottaJam
03-25-2006, 09:18 AM
i noticed the valencia was ported. is there much difference between it and the santiago as far as bass?

moldyoldy
03-26-2006, 12:09 AM
Apples and oranges. The 411 is unlike any other Altec 15" in that it has much greater xmax via the half-roll surround, and a 4" overhung voice coil. In a 6-8 cu/ft sealed box, 20Hz is readily acheivable, at the cost of a few dB sensitivity (~97/1W/1M). IMO the best Altec bass to be had. Old ones with original cloth surrounds that have collapsed and no longer retain their shape should have new foam surrounds or be reconed if the spiders are shot (GPA).

The Valencia's efficient vented 416 is no slouch in the bottom end though, it just has a more typical falling response from 40-20Hz.
If your source material largely stays above 40Hz, you won't notice much difference, other than the Valencias are louder. For HT, organ music, etc., the Santiago's 411s go that last octave.

For DJ apps, the JBLs would be the best choice, they'll handle the kind of power usually needed, and can likely use smaller boxes. The 411s are only rated 75-100W IIRC.