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High Efficiency Speaker Asylum Need speakers that can rock with just one watt? You found da place. |
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In Reply to: Re: Tad 4001 diaphragm question posted by GrantG on March 4, 2004 at 11:26:25:
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
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Follow Ups
- Tad Be diaphragm quasi-answer - Paul Butterfield 07:42:46 03/05/04 (2)
- Re: Tad Be diaphragm quasi-answer - Tom Dawson 09:54:13 03/08/04 (1)
- Re: Tad Be diaphragm quasi-answer - Paul Butterfield 05:54:01 03/09/04 (0)
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