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Does anyone know if the older TAD 4001 compression driver diaphragms are made of aluminum or have they always been beryllium from the get go? And if there was an aluminum version, do they sound any different? Thanks.
Follow Ups:
From my understanding, all 4001's have Be diaphragms, but they made they stronger/thicker/heavier in the mid-90's to prevent damage when played "Really" loudly. I guess some diaphragms suffered failure from extreme power input and they decided to make the change. Because of the additional weight, the frequency response is much more limited on top with the newer design, so the early ones are more highly regarded.Anyone can confirm or dispell this?
Hey Grant,Do not have any info on 4001 [but if I get enough 'blown' Be 4001's I'll measure and compare thickness of Be] — but as John mentions, this is true for the 2001. FYI, here is all I know (so far) about the 2001 Be dome, from my TAD 2001 whitepaper:
THE “Pre-1990” DOME:
As the story goes, in the late 1980s, TAD was getting returns and complaints of shattered Beryllium domes, and to mitigate this problem, increased the thickness of the Beryllium dome. This supposedly happened around1990, but when I asked TAD USA, they replied, “ There is no record of any production change to the beryllium diaphragms for TD-2001 at any time.” While they may indeed have “...no record...” of a production change, I have now measured a quantitative sample of both the “Pre-1990” and “Post-1990” Beryllium domes, and have found there is substance to the story.Measuring* cross sectional half dome pieces of the new style current production ‘Post 1990’Beryllium domes, in over 24 places, I found the thickness of the Beryllium dome to be a consistent and repeated 0.03 mm. Measuring cross sectional half dome pieces of ‘Pre 1990’, Beryllium, in over 40 places, I found the thickness of the Beryllium dome to average 0.02 mm. Additionally, in the cross sectional half of the ‘Pre 1990’ Beryllium dome, the outer edge, where the dome meets the surround, measured a consistent 0.03 mm [@ 9 measure points] then thinning to 0.02 mm [@ 24 measure points] then to 0.01 mm [@ 6 measure points] at the center of the dome.
This tells me the old style ‘Pre 1990’Beryllium dome is thinner, especially towards the center of the dome, than the ‘Post 1990’ dome. This would lend credence to the often repeated statement that the ‘Pre-1990’ domes (because of being lighter, thinner) have a perceived advantage in reproducing the ‘Delicate air’ of the high frequencies.
The way I categorize the domes into ‘old’ & ‘new’ is by direct observation of the glue joints between the clear high-polymer surround and the beryllium dome/VC former. In older ‘Pre-1990’ dome assemblies, the glue is opaque, and ranges in color as it ages over the years, from off-white to light brown. In the newer ‘Post 1990’ dome assemblies, the glue is gray in color and is translucent in appearance. The hardness of the ‘old style’ opaque glues, after scraping with dental tools, and removing Beryllium pieces from the ‘old’ glues, are a bit harder/stiffer than the newer ‘Post 1990’ glues. Both pre and post glues are quite excellent in bonding the dome pieces. In inspection of over 90 domes, I have found only one in which the glue bond had partially separated.
I suspect that it is also a combination of the ‘older’ glues used in combination with the thinner Beryllium that may be the reason behind the perception pre/post high frequency difference. Similar to how the 'voice' of a violin impreves over time...
*MEASURED with Mitutoyo Model 500-196
HTH, Paul (still too busy in Mitckey D Rat-Town) B
NOTE: Looking for blown 4001 domes!
"Those who hear not the music think the dancers mad."
- Angela Monet
Hi -I'm interested in what you find out about the 4001 diaphragms since I have a pair, but I bought them 'NOS' so to speak so I only have their serial #'s. Is there a way to correlate them with date of manufacture?
Hi Tom,Yes, there is [theoretically] a way to correlate the date of manufacture. I ask my rep. He asks via email JA rep. JA rep asks JA engineering data. Answer flows backward. This may take many months. Or never. Send me your SN#s, and I'll find out... eventually. < GRIN >
Best, Paul Butterfield
TAD audio products
"Those who hear not the music think the dancers mad."
- Angela Monet
Grant,I know this is true for the TAD 2001 diaphragms, but I don't know if it is true for the 4001.
Rgs, JLH
A friend of mine obtained some very interesting pieces, various prototypes and early examples, from Bart Locanthi's estate. Included were some very early 2001 and 4001 units, mounted to Dr. Bob Smith style Distributed Source horns. As I recall, these drivers were made before Pioneer had begun using the Technical Audio Devices, and the rear label said "Esquire" or some similar name. They all contained beryllium diaphragms to the best of my knowledge.Pioneer had hired Mr. Locanthi, who had designed many drivers while at JBL, to produce a line of superior quality drivers. He was given the freedom to design without the usual cost restraints, and the TAD line of drivers was the result.
Hi Trekman,AFAIK, No. Just got in a pair of 20+ year old Be domes from fellow audio/music enthusiast that have just suffered the ignominy of Be surround failure. The VC domes were used for those 20+ years in his home ultrafi system, not in pro sound reinforcement. Will be attempting experimental surround replacement repair on them. At first glance, they seem identical to a dome I recently received of recent manufacture.
Radian makes the only 'drop in' [theoretically] replacement, with a mylar surround used for the aluminum dome. A number of my clients have reported positive results with the Radian replacement. Good value for sound, but needs HF tweet, where TAD does not. TAD good for dynamics, Radian good for vocals.
RUMOR: [Disclaimer; May or may not be true. Probably false. Hearsay only.] Radian may be working on 'better' 4001 replacement.
Personal Note: for those of you that have noticed a slowdown in correspondence from me, I now have a 'Day Job' — and am working evenings on TAD stuff...
Best, Paul B
"Those who hear not the music think the dancers mad."
- Angela Monet
From what I understand, they have always been Be; never anything else. And they are not interchangeable with any other brand due to slight size differences compared to JBL. However, Radian makes an aluminum 4001 substitute. I've never heard either of them though.Neil
Thanks Neil. I was concerned because the used prices seems to go down much greater with age. I understand alnico magnets demagnitize over time, but I am hoping this won't be noticable, or these drivers would truly be worth much less. I didn't want to save money at the expense of not having a supposedly superior diaphragm, which for a TAD, would be the Be, I would suppose.
Talk to Paul Butterfield, he's "dman" on Tad's.paulbutterfield@earthlink.net
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