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Altec 604-8G Diaphragms

D

Doug Weiss

Member
Hello all,
I've had a pair of 604-8G for quite a while, and they have mismatched diaphragms. One is original, and the other is a Symbiotik. Regardless, they still sound wonderful, but in the spirit of progress I would like to buy a new pair and am looking at GPA 34647 or Radian 1228-8. I've heard favorable comments about each but haven't heard a direct comparison. If you've had experience with both of these, please share your thoughts, impressions, and if you have them, measurements. Thanks in advance!
 
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Depending on the exact production date of your 604's, 34647's may have been the original diaphragms.

8G's were introduced with the 23744 "light" diaphragm that was ultimately discontinued, and replaced by 34647 while 8G's were still in production.

For any 604 i'd stick with as close to original as possible. The only advantage the Radians will offer is a somewhat lower price, and they will sound somewhat rolled off in the high end compared to 34647.
 
bowtie427ss - thanks for the comment. Sounds like the Radian HF performance may be more like the Symbiotik. For an extra $60 ish, I guess I will go with the real thing. What's that 427 in?
 
Symbiotik starts rolling off steeply around 11.5 KHZ, where the newer diaphragm has a gradual roll off thats down 4 to 6db at 20,000 HZ. Now if you had the sectorial horn UREi used the speaker would be almost flat to 20,000.
 
Doug Weiss said:
bowtie427ss - thanks for the comment. Sounds like the Radian HF performance may be more like the Symbiotik. For an extra $60 ish, I guess I will go with the real thing. What's that 427 in?
Click to expand...

The Radian diaphragms are based on the Renkus/Emilar- type diaphragm design- which were, like the Symbiotik diaphragms, all designed by Dr. Jonas Renkus. Though there are some differences, they will all basically have the same "family" of sound, as a result.

Regards,
Gordon.
 
twiiii said:
Symbiotik starts rolling off steeply around 11.5 KHZ, where the newer diaphragm has a gradual roll off thats down 4 to 6db at 20,000 HZ. Now if you had the sectorial horn UREi used the speaker would be almost flat to 20,000.
Click to expand...

Thanks for your comment. Even though I can't hear above 11.5 kHz, there's not enough difference in cost to justify the Radian. This isn't a pro sound application.
 
GordonW said:
The Radian diaphragms are based on the Renkus/Emilar- type diaphragm design- which were, like the Symbiotik diaphragms, all designed by Dr. Jonas Renkus. Though there are some differences, they will all basically have the same "family" of sound, as a result.

Regards,
Gordon.
Click to expand...

Thanks Gordon!
 
The Radian will be significantly more transparent due to the lack of suspension resonance that a metal diaphragm suspension has. Another benefit is the lack of ear fatigue due to the lower distortion.
 
edgewound said:
The Radian will be significantly more transparent due to the lack of suspension resonance that a metal diaphragm suspension has. Another benefit is the lack of ear fatigue due to the lower distortion.
Click to expand...

edgewound, that puts a different light on this altogether. If I understand what you're saying, the metal suspension resonates at a specific frequency that interacts with the other frequencies being reproduced. Might come across as harshness, or perhaps the perception of HF extension and brightness? As far as transparency, does that translate to accuracy, soundstage, etc? Any idea how the Radian compares with the original Symbiotik for response and relative efficiency in a 604-8G application? Thanks!
 
Doug Weiss said:
edgewound, that puts a different light on this altogether. If I understand what you're saying, the metal suspension resonates at a specific frequency that interacts with the other frequencies being reproduced. Might come across as harshness, or perhaps the perception of HF extension and brightness? As far as transparency, does that translate to accuracy, soundstage, etc? Any idea how the Radian compares with the original Symbiotik for response and relative efficiency in a 604-8G application? Thanks!
Click to expand...

Hi Doug,

Your understanding is correct. The Mylar suspension of the Radian diaphragm is free of the metal surround resonances. As an added bonus, Mylar doesn't work harden like aluminum and crack after extended time in use. Much the same as Symbiotik, which is Kapton polyimide, the same material as the voice coil former.

Dr. Richard Kontrimas, the Radian founder was involved with the engineers at Emilar, Renkus-Heinz, and Altec-Lansing. He has a Ph.D in metallurgy and developed a proprietary alloy and heat treatment for the Radian diaphragms. I used to spend hours talking with him over three decades at his facility before he sold the company and retired just a few years ago. I believe the Radian website has a discussion on this material.

https://radianaudio.com/pages/about-radian

There's a reason many mix down houses in Los Angeles use Radian diaphragms in their large format studio monitors. They just sound better. It's like cleaning a hazy window, or removing a veil form the front of the speakers. Cleaner, clearer, less fatiguing playback. The systems I've restored for customers with either Altec or JBL drivers the last few years have raved about the difference in clarity and detail. Another thing to strongly consider is having the AlNiCo magnets recharged to bring them up to brand new spec. The difference is not trivial. Bass response becomes faster and tighter, high frequency response becomes more sensitive and extended.

Hope this helps.
 
edgewound said:
Hi Doug,

Your understanding is correct. The Mylar suspension of the Radian diaphragm is free of the metal surround resonances. As an added bonus, Mylar doesn't work harden like aluminum and crack after extended time in use. Much the same as Symbiotik, which is Kapton polyimide, the same material as the voice coil former.

Dr. Richard Kontrimas, the Radian founder was involved with the engineers at Emilar, Renkus-Heinz, and Altec-Lansing. He has a Ph.D in metallurgy and developed a proprietary alloy and heat treatment for the Radian diaphragms. I used to spend hours talking with him over three decades at his facility before he sold the company and retired just a few years ago. I believe the Radian website has a discussion on this material.

https://radianaudio.com/pages/about-radian

There's a reason many mix down houses in Los Angeles use Radian diaphragms in their large format studio monitors. They just sound better. It's like cleaning a hazy window, or removing a veil form the front of the speakers. Cleaner, clearer, less fatiguing playback. The systems I've restored for customers with either Altec or JBL drivers the last few years have raved about the difference in clarity and detail. Another thing to strongly consider is having the AlNiCo magnets recharged to bring them up to brand new spec. The difference is not trivial. Bass response becomes faster and tighter, high frequency response becomes more sensitive and extended.

Hope this helps.
Click to expand...

edgewound, many thanks for your input. I was very close to pulling the trigger on the OEM units, but everything you've said, especially regarding listening fatigue, is spot on with what I like and occasionally dislike about these speakers. It all depends on the music I'm listening to and the degree to which my tinnitus is acting up. With the right recordings, these 604s sound amazing.
 
Doug Weiss said:
.....Any idea how the Radian compares with the original Symbiotik for response and relative efficiency in a 604-8G application? Thanks!
Click to expand...

I have no direct experience with Radian diaphragms for Altec but hold the Emilar EC/EA175 and Renkus Heinz SSD drivers in high esteem. FWIW, I've done quite a bit of comparison between the Altec Aluminum vs. Symbiotik diaphragms and also compared the Emilar EC175 vs. Altec 802, amongst others. Ultimately, I chose the 802 motor + 20275 or 34852 diaphragms for my application.
 
edgewound - since you deal with studios, is there a sonically desirable advantage to a 604-8G with a 16 ohm diaphragm (vs 8 ohm), along the lines of the model Altec 604-168X? They sold it without crossover to be biamped. Ultimately, that's the direction I'm going, and short term, I can easily modify my existing crossover.
 
Altec's reasoning was that with an 8 ohm woofer and 16 ohm horn, you could use smaller (=cheaper) coil and cap values in the crossover.
 
toddalin said:
Altec's reasoning was that with an 8 ohm woofer and 16 ohm horn, you could use smaller (=cheaper) coil and cap values in the crossover.
Click to expand...
When I ran the numbers on changing my 2nd order xover from 8/8 to 8/16, the HF cap value was cut in half but the HF choke value doubled. Wonder if there was any other implied benefit? I don't use the stock xover so I can adjust if there's a sonic benefit.
 
One more question to the group that has provided many helpful answers - if I could get a Pascalite diaphragm, specifically a 26421, vs the otherwise recommended Altec 34647, would there be any advantage, other than the joy of reconfiguring my crossover?
 
You mean the same Pascalites everyone hated? and quickly changed?
Even Altec stopped making them.
 
Nyjblbob said:
You mean the same Pascalites everyone hated? and quickly changed?
Even Altec stopped making them.
Click to expand...

Bobhorn, that's what I needed to hear. Didn't find that kind of animus toward them in a handful of google searches, but they were added to the available options at the 11th hour. Just trying to get it right the first time based on input from the experts.
 
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