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Altec Malibu Speakers - how to optimize?

hammr7

hammr7

AK Subscriber
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I recently stumbled into a beautiful pair of Altec Malibu Speakers. Having never really played with Altecs in a home environment, I figure I'll put these through the paces and see how they are as-is, as well as what reasonable enhancements can do for them.

I hope to have pictures of them next week when I take them out of storage and get them set up to play.

It seems that the 843B Malibus are relatively rare, with each containing an 806a / 811b horn and a pair of 414z woofers crossed with an N-800-F network.

From what I have read, I need to check the woofer accordian surrounds for any Altec goop buildup, and make sure the crossover pots are clean and functioning. Otherwise, any additional improvements apparently relate to component upgrades (Altec or other aftermarket) to enhance the high frequency response and perhaps to change the crossover frequency to the horn.

The question for me is what would be the best enhancements while keeping everything in the existing Malibu boxes?

It seems like the Altec horn may be something of a limitiation for high frequency output. I've read about roll off above 14 kHz, although this doesn't seem to be a universal claim. Assuming it is true, if I want to extend high frequency response, do I look at going 3-way? I have a bunch of extra high frequency drivers (like Jensen RP-302s) and a Marchand 3-way active crossover I could play with unless Altec has a better horn to better handle everything from ~ 1 1Hz up and a passive crossover network to accomodate the alternate horn and the 414z woofers.

I've seen references to modifying the crossover point of one of the 414z woofers to configure it for "two and a half" lower base reinforcement rather than the same extended range as the other. For years I used (and still have) KEF 304s that did that quite nicely.

From what I have heard I won't get wild lowest bass output, but that may not be a problem for me.

So what have I got right in my plans and what else might I want to try?
 
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Only when I get them to the point where they can be the sound system for the party!
 
hammr7 said:
It seems like the Altec horn may be something of a limitiation for high frequency output. I've read about roll off above 14 kHz
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It's not the horn, it's the 806A driver. 14k is generous.

Have you considered active bi-amping?

Without swapping HF drivers, or a radical and costly re-design of a network, i think DSP based active bi-amping would show you the most potential for the least modification and expense as it seems you already have the amplifier requirements well handled.
 
This is off topic but I think that after hearing them in stock form you might be quite content to then leave them alone or simply go for optimally stock; they're very seductive. I owned a pair in Heath AS-21 form and at times I preferred them to my Model 19s.

I admit to swapping out the compression drivers for GPA 902s, the improvement was subtle and I loved them in stock form as well.

Anyway, whatever you do I advise you to be wary of screwing up the speaker's basic voice, give them a chance.
 
bowtie427ss said:
It's not the horn, it's the 806A driver. 14k is generous.

Have you considered active bi-amping?

Without swapping HF drivers, or a radical and costly re-design of a network, i think DSP based active bi-amping would show you the most potential for the least modification and expense as it seems you already have the amplifier requirements well handled.
Click to expand...

Thanks for the responses. Whatever I do I want to do slowly, so I will spend some time with the Malibus as they are. I may eventually seek to bi-amp, but at least initially I'll stick to single amps.

Bowtie, I meant the driver. I have heard about the 902 driver mdification, but wondered whether simply adding a super-tweeter might be less intrusive.

One reference I saw described how the stock Malibu horn driver "muddied" certain clicky percusion sounds. Allen Organ solved that problem 50 years ago, with great results, by adding Jensen RP-302 tweeters to their stock offerings. Since I already have the Jensen drivers, and an active network that can cross virtually anywhere I want ($18 per pair of frequency chips if I don't already have the desired frequency), my cost is almost nothing.

If the tweeter mod proves sufficient I can simply augment the existing passive crossover. If I go with the 902 driver it seems I may want to scrap the current crossover completely. I realize making the Malibus 3-way speakers may be an issue, but I am currently expecting a crossover somewhere at or above 10 kHz (similar to what I did with ribbon supertweeters on my CLS-II speakers), so hopefully I can minimize any adverse effects.

If the 800 Hz crossover point needs to change, then I am eventually looking at a new passive crossover anyway.
 
For relaxed speakers that are easy on the ears, fun to listen to, and capable of long listening sessions without fatigue, the addition of the 302s will make them a little more extended, etched, and Jodi leaning.
 
A simple addition that has worked well for Mark Hardy and for me with our 604E's is the addition of a simple supertweeter on top of the main cabinet.

Mark uses a Fostex T90A with a simple 2uF cap crossover and an 8 ohm L-pad to control the volume. It sounds great and fills out the high end of the 604E.

I did the poor man's version using Pyramid TW44 horn tweeters that Parts Express sells for $10 each. Since they are 4 ohms rather than the 8 ohms of the Fostex, 4uF caps give the same 20KHz -3db point in the single order crossover.

Just for fun, I brought the Pyramid setup with me on a recent visit to Mark's audio heaven. We compared them to the Fostex T90A's and heard virtually no difference. So save yourself a few hundred bucks and try out the Pyramids first.

Confession - I saw a good eBay deal on a pair of new T90A's so I grabbed them. Yeah, they're definitely prettier than the Pyramids...
 
Drugolf said:
hammr, what did you end up doing here?
Click to expand...

At the moment the Malibus are my main speakers, but I am running them as almost stock 2-ways (different crossovers than the N-800s). I am doing a lot of work on my music room, and have been distracted by real life, so I haven't delved into my proposed 3-ways. To be honest, until I finish work on the room I can't take full advantage of the speaker improvements. And the default Malibus are already pretty nice.
 
hammr7, i've been using my malibus stock through a variety of ss and tubed receivers/amps for the past six years in my office, and they're absolutely wonderful just as they sit. they're behind me about eight, nine feet, in a 20x10 office full of stuff, and even when i turn them down low i can hear so, so much detail. i'll miss these when i retire (they're not allowed in the house with their size)...

listening to lockjaw davis play subtones on "the man with the horn" backed by paul gonsalves, roland hanna, everett barksdale, ben tucker, and grady tate...so, so good.
 
You might try find a Model 19 crossover schematic and use the supplementary section of the HF section to flatten the response of the driver. Or you might want to try to find some N-1201 crossovers which will raise the crossover freq ridding the honking sound of the horn. Being two section crossover HF section it allows more flexibility in getting the correct balance. You might also want to replace the HF driver diaphragms that you can purchase from Great Plains audio. We used to pull 811 and 511 horns and paint the outside of the horns with auto undercoating to dampen the horn tendency to ring. With a little care. you really don't need a super tweeter. Finding a pair of Altec 950 UHF ring radiators is a real challenge. later model JBLs would work but earlier models have very erratic performance. Tannoy super tweeters will break the bank. Bob Crites of Klipschorn fame has tweeters you could add with the appropriate crossovers.
 
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