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Vintage Phenolic Ring Tweeters: magnets differences and sound quality

P

peters8

Active Member
Hi guys!
I've three couples of vintage phenolic ring tweeters: two couples haven't any brand stamped on the magnet, only one pair has the name of its manufacturer: BIC 020.
I know that BIC was a good brand, but strangely the magnets of these BIC are smalller than the magnets of the other phenolic ting tweeters that I own (I hope to post their pictures tomorrow).
So, my question is the following: could the size of a phenolic ring tweeter be a quality guarantee?...I mean: is the tweeter with the biggest magnet the one with the best sound?
Thank you very much!
Best regards
 
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USA based driver manufacturer CTS was indeed the company that pioneered the aftermarket phenolic ring tweeter design but once it hit the market it was immediately copied by many other US based driver manufacturers and the Japanese manufacturers as well. To my knowledge no European driver manufacturers ever copied the phenolic ring design.

All other factors being equal, which is definitely NOT the case with phenolic ring tweeters from different manufacturers, a larger ceramic magnet should yield better sound quality. The problem is the voice coil structures are not all identical so different tweeters from different manufacturers can indeed have very different response curves even with similar sized magnets. Also different diameter voice coils were utilized with the larger coils (and corresponding dust caps) being designed to handle more power.

If you find fully functional CTS branded phenolic ring tweeters on FleaBay, you really can't go wrong. The blue paper cone phenolic ring tweeters used by Marantz in their US made Imperial series speakers were also of good quality. In the BIC Formula series speakers from the 1970's which also contained a horn loaded "Biconex Horn" tweeter, the phenolic ring tweeters were used as a "super tweeter" and crossed-over at a relatively high frequency to cover frequencies above the output range of the Biconex Horn and therefore provided a limited contribution to total sound output.
 
There were two principal versions of the CTS phenolic tweeter, identified as such on the back plate.

The better one was the 2T8, signifying a 2" VC and 8 oz. magnet. There was a less expensive version called the 3T2, 3" VC and 2 oz. magnet. Why the cheaper one had a bigger VC I coudn't tell you.

There are, of course, endless copies of these...
 
1tumbleweed said:
There were two principal versions of the CTS phenolic tweeter, identified as such on the back plate.

The better one was the 2T8, signifying a 2" VC and 8 oz. magnet. There was a less expensive version called the 3T2, 3" VC and 2 oz. magnet. Why the cheaper one had a bigger VC I coudn't tell you.
There are, of course, endless copies of these...
Click to expand...

Hi 1tumbleweed!!! thank you for your very interesting reply!
I can assure you that there's also a 5 oz magnet version...as soon as possible, I'd like to post the pictures of the three versions of my phenolic ring tweeters...
It could be funny to try, all together, to identify the models of these tweeters I own.
Thank you once again for your support!
Regards
 
Marantz used them in the Imperial line. Depending on the year the speaker models were made they can have black, brown or blue cones. I like the sound of the CTS made phenolic tweeters. Parts Express sells 4 and 8 ohm versions that they claim are modern direct replacements for them. I haven't tried them myself.
 
peters8 said:
I can assure you that there's also a 5 oz magnet version...
Click to expand...

I have no doubt. CTS, being a for-hire manufacturer, would custom build any variety you wanted. I mentioned the 2T8 and 3T2 specifically because they were in the "dealer" line which was designed to be sold by retailers. I'm sure many other variations exist.

as soon as possible, I'd like to post the pictures of the three versions of my phenolic ring tweeters...
Click to expand...

Please, do!
 
Hi! I apologize for the delay.
Anyway here're the picture of the three phenolic ring tweeters models
 

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peters8 said:
Hi! I apologize for the delay.
Anyway here're the picture of the three phenolic ring tweeters models
Click to expand...

In the first picture you can see the biggest and the heaviest model, the second is the medium size model...and the third is the smallest and the lightest model...the BIC.
In the second picture you can see a comparison between the medium size model and the biggest one
In the third picture, you can see a comparison between the smallest model (BIC) and the medium size one: please notice how short is the BIC tweeter (and its magnet is smaller than the others!)
In the pictures below, I tried to measure the diameter of the three magnets (obviously the measurement is in centimeters).
The best sound belongs to the biggest phenolic ring tweeter.
The BIC model, even if it's the smallest one sounds fine and detailed...the third tweeter, the one with the medium size magnet, sounds decently but I hear a bit of distortion
Obviously I've use a Mundorf 3.9 uF capacitor to test all these old tweeters.
That said...Watching the pictures, is there an 8 oz magnet version among these three tweeters, in your opinion?
Thank you once again for the patience and for your kindness, my friends!
best regards!
 
Hi guys!...so, do you notice a version with the 8 oz magnet in these pictures above?Please guys, let me know!
Thank you.
regards
 
Lavane said:
Marantz used them in the Imperial line. Depending on the year the speaker models were made they can have black, brown or blue cones. I like the sound of the CTS made phenolic tweeters. Parts Express sells 4 and 8 ohm versions that they claim are modern direct replacements for them. I haven't tried them myself.
Click to expand...
I have used the Parts Express tweeters in some bookshelf speakers that I built and like them.
 
I have bought multiple pairs of the Parts Express version over the years, as replacements for blown vintage Kenwood phenolics. I compared one of the Parts Express units to a working vintage Kenwood phenolic, and preferred the Parts Express'. Who knows if the older one was abused at some point, but I don't think you can go wrong with the PE replacement.
 
peters8 said:
Hi guys!...so, do you notice a version with the 8 oz magnet in these pictures above?Please guys, let me know!
Thank you.
regards
Click to expand...
On the frontal1 pic, which has all three tweeters, I would have to guess the the one on the far left ( the largest ) would be the 8 oz. magnet.
 
peters8 said:
Hi guys!...so, do you notice a version with the 8 oz magnet in these pictures above?Please guys, let me know!
Thank you.
regards
Click to expand...
LASALLY has this for sale in barter town. Original 2T8 with 8 oz magnet.
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Last edited:
Hi guys!
I've a question for you!: in your opinion does the BIC phenolic ring tweeter (the smallest one you can see in the picture above) can reach 18.000 hz?
Thank you!
 
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