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Thread: Altec 811b + what driver?

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    Member Al Klappenberge's Avatar
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    Altec 811b + what driver?

    Hi guys,

    I'm new here. This is my very first post..

    Question: I have Altec 811B horns with JBL 2426H drivers on them. The response drops off in a smooth droop. What driver do you suggest I put on these horns to use in a 3 way system crossed at 700 Hz and 7500 Hz?

    Al K.

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    2404 or 2405's.

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    Member Al Klappenberge's Avatar
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    Alex,

    The 2404 and 5 are tweeters. I am using Beyma CP-25 and am pretty happy with them. What I want to do is REPLACE the 2426H drivers with something that works better on the Altec 811b horn.

    AL K

    Last edited by Al Klappenberge; 01-31-2004 at 04:48 PM.

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    Member Al Klappenberge's Avatar
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    Ok then, I'll be specific --> 802, 806, 902?

    Does anybody make new new ones now or do I buy a pig in a poke off eBay?

    Al K.

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    OK, then IMHO You are all set, an Altec driver will not make it sound "better", but Your horns and the 2426īs are designed to be x-overed at 800 Hz.

    Alex.

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    Member Al Klappenberge's Avatar
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    Alex,

    I am stretching the crossover down a bit to 700 Hz becasue that's the upper limit of the Belle Klipsch woofer. The crossover has extremely sharp slopes, so there is no danger of damage from lows. I am just hoping a driver desinged for the 811 / 511 horns would not show the frequency response droop the JBL driver shows with the 811 horn. I have tried an Altec 902-8 driver and it is beautifull but I only need flat response to 7500 Hz where I am crossing to a tweeter. What I am looking for is a NEW alternitive to buying a used driver in unknown cndition. That is why I bought the JBLs.

    I have response plots I can post if it will illustrate my point.

    I may have to get a used driver and fix it up, I just don't want to!

    To see what I have done, click on the "My stereo stuff" link below.

    Al K.

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    Senior Member maxwedge's Avatar
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    You could try a 2461 with the phenolic diaphragms, if you can find them they go down to 500 hz. I have a pair and they sound great as long as you have a tweeter, cause they crap out about 12k. I've seen them from time to time on ebay but you have keep looking. Also if you can find only the diaphragms they may fit your 2426's but an expert here will have to confirm this.

    Looks like Jammin Jersey has some.

    EDIT: Looks like he has 2470's also but I'm not sure what the difference is to the 2461 except that it has a bigger magnet. Same price.
    Last edited by maxwedge; 02-01-2004 at 07:52 AM.

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    Member Al Klappenberge's Avatar
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    Maxwedge,

    I have tried to attach my plot of the 2426H + 811b horn.

    Do you think the phenolic diaphragm would solve this problem up to 7500 Hz. I an thinking it's some sort of throat mismatch between JBL and Altec. What I don't know about horns would write the book though!

    Al K.
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    Senior Member maxwedge's Avatar
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    I'm not the one to really the one to answer your tech questions, as there's far more experienced people here, but I do know that the responce you get is the result of your 'combo' of the horn and driver combined. Looking at your graph it looks like you have more of a HF problem (I didn't quite get that point before)....I was thinking of your 700hz crossover point for the 2461. I don't really know if it would help in the HF range you need.

    Scott

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    Member Al Klappenberge's Avatar
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    Scott,

    Ok... Here's a plot done at the same time with an Altec 902 driver on the very same horn. It is much better. Since I would have to get used ones and I only need it to go flat to 7500, I was hoping that there would be an alternitive driver. I think also that the JBL drivers just don't match the Altec horn. Since Altec isn't making them any more I guess I'm stuck with what I got or a used Altec.

    Al K.
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    Senior Member maxwedge's Avatar
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    Yes, thats a much nicer plot. I'd say you must be correct about the JBL/Altec combo. Another alternative would be to use a JBL horn but that may involve some modifications to your cabinet. I take it the 902's don't belong to you?

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    Member Al Klappenberge's Avatar
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    Scott,

    No.. The 902 driver was on loan from a fellow I desinged a set of crossover netwroks for. He was going to use the 902 with a 511 horn, my network and a Klipsch LaScala woofer. I just had the driver to measure the complex impedance of it across it's frequency range. (I'll post that plot if anybody's interested)

    Actually, I have an R-C equalizer in the squawker circuit now that flattens out the response. I just don't like equalizers. I think I am just going to try a better equalizer next. It will certainly cost me less money than replacing 3 drivers!

    Al K.

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    Member thevott's Avatar
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    902 drivers in excellent and /or new condition are frequently available on Ebay and replacement diaphrams should be available for many years to come. These staple drivers are only out of production because of corporate Bologna Sausage, not because of obsolescence or the normal 'end of production'. The demise of Altec is a truly sad and disappointing reality

  14. #14
    Member Al Klappenberge's Avatar
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    thevott,

    Have you ever replaced a diaphragm in an Altec driver? How much trouble is it?

    I treid to do it in a set of older JBLs (2420s I think) and didn't have much luck. I know about the "rubber hammer" centering method. I did two of them. One came out ok but the other wouldn't center. The new diaphragms I was given were an unknown quantity though. They may have been used ones! They were from Jammin' Jersey as were the drivers themselves. I finally made J-J take the drivers and the diaphragms back, which he did with no argument.

    Al K.

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    Member thevott's Avatar
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    Al,

    I have removed and inspected almost all of my Altec diaphragms (both large and small) with no problems. It is so easy that I've even performed the operation just to show my friends how they're assembled. I guess I'm a speaker nerd though, what can I say. Anyway, the only JBL's I have disassembled are my 075 bullets when I replaced the diaphragms---which was also a piece of cake---but that's another animal entirely. I expect most JBL drivers are just as easy to service as their Altecs cousins if the proper manufacturing tolerances are met and if there is no oxidation/corrosion on the screws and centering pins.


    MP

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