Watkins woofer white paper

I have a copy of an article New Loudspeaker with Extended Bass written by William H. Watkins published in Audio magazine in December, 1974.

This is a technical five-page paper discussing enclosure and crossover design for the Watkins woofer, and includes pertinent graphs and formulas.

I don't know if this article is the "white paper" referred to in this thread, but I have made a PDF scan of the article.

I could post the PDF file here, but I don't know if doing so would violate any copyright laws. Does anyone know?

I can email a copy of the article on request.

Ken


I know I want to read it, post it here, or at least email me a copy. jazzmans AT G mail dot com
 
Does anyone have the T/S parameters for a 12 inch Watkins woofer? What is the ideal box size? My (5 cu. ft.) QLS1 box "sounds" too big, kind of "boomy".
 
I asked Mr. Watkins these exact questions. Here are his responses from a back-and-forth email.

My question: Do you have Thiele/Small parameters for your new 12” Watkins woofers? Do you have a suggested sealed box size for them? I measured the internal volume of my Infinity 2.5’s to be about 2.36 cubic feet, but is that an optimum size for these woofers? How about a suggested box stuffing material?

His response: The dual drive configuration circumvents the Thiele/Small parameters. You can have whatever Q you want free from efficiency restraints. The volume of the 2.5 is matched to the LC circuit of the dual drive network. Anything else would have been completely improper. The stuffing in the speaker is also matched to the other dual drive parameters.
 
FWIW.
I had been using the RS series grey poly coned Watkins in my QLS-1s for quite some time.
My Q2s have the original gray paper Watkins.
I thought the Q2 bass response was more interesting, musical and detailed compared to the QLS.
I replaced the RS polys with the "originals".
Significant improvement.
 
Yes and well it should. If you look at the magnet size it gives you the answer, If you use the woofer from the RS 2.5/RS 4.5 it is wrong for the older series like the QLS1, QLS2 and so on. Look at the box size. Bill Watkins said that the new poly series could be used in the old series. This is wrong. The older series had larger boxes meaning you could get away with smaller magnets. Using the the poly cones with larger magnets causes the roll off to begin much to soon in a large box. I could explain this but I will only if I need to. If you don't believe me take a QLS1 and put a poly in one and the old paper cone in the other. The low bass difference will be very apparent. However the mid bass smack will be better with the poly. Always a trade off. In my opinion the paper cones sounded better. Even a rubber vs a foam surround can change the sound. If you have the old cones keep them and change the surrounds if they wear out.
 
Yes and well it should. If you look at the magnet size it gives you the answer, If you use the woofer from the RS 2.5/RS 4.5 it is wrong for the older series like the QLS1, QLS2 and so on. Look at the box size. Bill Watkins said that the new poly series could be used in the old series. This is wrong. The older series had larger boxes meaning you could get away with smaller magnets. Using the the poly cones with larger magnets causes the roll off to begin much to soon in a large box. I could explain this but I will only if I need to. If you don't believe me take a QLS1 and put a poly in one and the old paper cone in the other. The low bass difference will be very apparent. However the mid bass smack will be better with the poly. Always a trade off. In my opinion the paper cones sounded better. Even a rubber vs a foam surround can change the sound. If you have the old cones keep them and change the surrounds if they wear out.
The RS Watkins driver in the QLS-1s produced a woolly boxy type of bass, very unattractive.
I too have talked to B Watkins and he did say all Watkins types would work, but perhaps he meant if they had individually appropriate crossover parameters per design.
There is an interview with Watkins where he says "the 4.5 woofers were dogs".
I thought this statement may have colored my listening and prejudiced me against the RS poly.
Replacing them with originals nixed that.
 
Here is a link to an interesting white paper on the Infinity IRS Omega. It includes a very interesting discussion on the Watkins DVC woofer that was developed for this speaker, and apparently it was designed to perform better than the previous versions of Watkins 12" woofer (dare I say a further evolved version). Here are a few excepts to get you more interested:

- Omega's Watkins dual voice coil woofer is a totally new design from its specially formulated cone to its frame...
- ...design changes were required in every important performance parameter in order to achieve a major advance in sonic quality over former Watkins designs.
- The woofer's dual winding voice coil is a refinement from former Watkins designs...
- The cone material of Omega's two cone drivers is a kevlar and paper composite...
- ...the frame is an aluminum die-casting rather than stamped steel...

Highly recommend reading for all DVC enthusiasts, very informative. I looked up the part number in an IRS Omega spec sheet, and it appears to be: 334306-001

LINK: http://www.cieri.net/Documenti/Infi...Infinity - IRS Omega - White Paper (1998).pdf
 
Considering that the patent has long expired, I'm surprised that no other manufacturers have latched on to this design
 
Bill Watkins Jr. provided me with some additional info..."The IRS Omega Watkins Woofer was designed specifically for the Omega application....it's unique parameters would not be a better match than a original Peerless kapok/felt-coned Watkins woofer [used in the QLS speakers]...the QLS performs excellent with it. The later Infinity Watkins woofers were built by Tonegen...[which] will work well in the QLS, but I prefer the original Peerless woofer to maintain it's original performance spec and sound."

Thus, it appears that newer 12" Watkins DVC woofers may be a perfect/exact drop-in replacement in terms of specifications and sound in QLS models. I am convinced, and decided to refoam edge my old Watkins DVC Peerless woofers as I continue to refurbish my old QLS-4 speakers.
 
Are replacement coils for the 12" woofers available through Watkins or any aftermarket source? I am looking at future proofing a pair of speakers and I always like to have spares.
 
Leads to another question of how to identify the different magnet/VC versions. You'ld have to be careful buying one replacement.

I once collected some photos that I could find of various 12" Watkins DVC woofers that might be found in an Infinity speaker, and Bill Watkins Jr was kinds enough to provide his input (see link below).

Infinity%20Woofers%20Comparison.jpg

https://www.dropbox.com/s/prfxkqr32snqbjw/Infinity Woofers Comparison.jpg?dl=0
 
Here is a link to an interesting white paper on the Infinity IRS Omega. It includes a very interesting discussion on the Watkins DVC woofer that was developed for this speaker, and apparently it was designed to perform better than the previous versions of Watkins 12" woofer (dare I say a further evolved version). Here are a few excepts to get you more interested:

- Omega's Watkins dual voice coil woofer is a totally new design from its specially formulated cone to its frame...
- ...design changes were required in every important performance parameter in order to achieve a major advance in sonic quality over former Watkins designs.
- The woofer's dual winding voice coil is a refinement from former Watkins designs...
- The cone material of Omega's two cone drivers is a kevlar and paper composite...
- ...the frame is an aluminum die-casting rather than stamped steel...

Highly recommend reading for all DVC enthusiasts, very informative. I looked up the part number in an IRS Omega spec sheet, and it appears to be: 334306-001

LINK: http://www.cieri.net/Documenti/Infinity/Documenti tecnici/Infinity - IRS Omega - White Paper (1998).pdf
Thanks for that!

I'd be willing to bet that this is the 'final' design of the watkins dual vc driver, remember, Watkins themselves recommended the new driver over the older versions. There was a lot of hyperbole in the white paper, but also a good amount of info.
A lot of info on the emit/emim changes as well!
added to my personal collection!
 
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