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Old 28th February 2012, 09:22 PM   #1
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Default DIY Walsh driver revisited

Is anyone out there still playing with home build Walsh drivers?
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Old 3rd March 2012, 04:24 AM   #2
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Not much interest, eh? On another forum, someone mentioned the Walsh tweeter that Infinity used for a time.
I worked with Bill Seneca on the original prototypes for this thing- We probably built 50-60 pairs of these guys on my kitchen table.
If there is interest, I'll share how we did it.
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Old 3rd March 2012, 04:37 AM   #3
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Yes, I would be interested. I have a pair of Infinity WTLC's with one of the Walsh tweeters out. Quite frankly, they both could use a complete overall.
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Old 3rd March 2012, 04:58 AM   #4
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I am interested also. Nothing like learning from someon.e who it's experienced.
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Old 3rd March 2012, 09:25 PM   #5
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Can you attach a couple of close-up photos of your tweeter?
I can tell you what we did with the prototypes, but I don't know what Arnie Newdell did in production.
The base for the tweeter was a Seas 1 1/2 inch dome. They were used in the Dynaco two way bookshelf, and back then, they cost about $9. I doubt of you can get them any more, but I did see a couple of likely candidates at Part Express.
We had to carefully cut the dome off of the voice coil, which was tricky because the magnet attracted the Exacto knife blade. We ruined quite a few.
The cone was made of a layer of 1 mil acetate that was cut using a pattern. There was no particular science involved- we just arbitrarily selected a size, about 6" tall, and the angle. The acetate was then smeared with clear silicone except where the end met for cementing. We used 5 minute epoxy.
Now over the coated acetate was placed a layer of heavy duty aluminum foil that conformed to the shape of the thing, and the laminate was rolled into a cone shape and epoxied. I think we used invisible Scotch tape to hold the seam while the epoxy set.
A wooden dowel was epoxied to the center of the pole piece in the tweeter that was long enough to just reach the end of the cone when it was assembled.
This was used to hold a thickness of urethane foam cut ever so slightly larger the the open end of the cone. This served to terminate the acoustic wave traveling up the cone, and helped give the cone a little support.
A hole was cut in the center of the foam to accomodate the dowel.
The cone's small end was trimmed to fit the voice coil former, and was then epoxied.
Surprisingly, we didn't use a jig to hold the cone- we just set it in there and eyeballed the angle, then waited for the epoxy to set.
The, a small amount of Dacron was placed inside the cone around the dowel, and the foam plug was ever so gently eased into place.
That is basically it. We didn't have the luxury of instrumentation- the whole thing developed by trial and error and extended listening. We were told by a true "golden eared" musician that it had a slight peak at about 2KHz. I think Seneca smeared some white heatsink grease around the surround and that helped fix it.
White heatsink grease got smeared on a lot of things back then to see what would happen.
The Promethean Audio cartridge resulted from injecting the stuff inside the cantilever of a $35 Grado cartridge. It dampened micro resonances that were occurring in there.
I'll look around for a few possible candidates for making these things and get back here in a day or so.
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Old 3rd March 2012, 09:30 PM   #6
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The clear silicone we used was clear silicone grease- Not the RTV adhesive!!!!

Last edited by glorocks; 3rd March 2012 at 09:31 PM. Reason: misspelling
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Old 4th March 2012, 01:05 AM   #7
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I did a bit of poking around at Parts Express, and found a dome tweeter that might be a good starting point. Part # DC28F-8. It has three things going for it- it's relatively cheap at $22.00, it can be dismantled, so you can cut the dome out without having the Exacto blade pulled out of your hand, and you can get replacement diaphrams. You'll ruin a few before you get it right.
Now, the holy grail- when we were playing with these titanium foil was "unobtainium".
We wanted very much to try it but couldn't get it.
Now, we have Titanium Goat where you can get it in small quantities without draining your wallet.
I mention this because I am thinking about building a Walsh driver that can extend down to 200 Hz or lower, and hoping that some of you will be encouraged to try this and share your expriences here. German Physiks Walsh (they disavow the term Walsh, but that's exactly what they are building) speakers using titanium have received rave reviews, but at $45K a pair and up, I couldn't afford to audition them much less own them.
So, gang, get out your Exacto knifes and Epoxy and have some fun.
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Old 6th March 2012, 03:10 PM   #8
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Hi Jay,
I will post some pictures of the Walsh tweeters on my WTLC's.
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Old 6th March 2012, 04:39 PM   #9
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Here is few shots. I will take more if needed.
Attached Images
File Type: jpg IMG_0174.jpg (658.9 KB, 2946 views)
File Type: jpg IMG_0176.jpg (681.0 KB, 2755 views)
File Type: jpg IMG_0178.jpg (976.1 KB, 2617 views)
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Old 6th March 2012, 05:18 PM   #10
von Ah is offline von Ah  United States
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What a great thread! I certainly hope to see more developments!
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