walsh tweeter design/rebuild
- Thread starter loquatious
- Start date
loquatious
village elder
its just standard white polyfill. same stuff as the cabinets are stuffed with.
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Rex81
Well-Known Member
I just acquired a set of fully functional WTLCs that fortunately only needed a refoam on the woofers, some Restore-a-Finish and Feed-n-Wax on the cabinets, and new foam for the Walsh tweets.
After closely analyzing Loquatious' post a few pages back about replacement foam, but being too cheap to order a full sheet of the stuff plus shipping, I came across what I believe to be a suitable replacement at the local Home Depot.
http://www.homedepot.com/p/Shop-vac-Small-Foam-Sleeve-Filter-SHO9052600/205904905
It is simply the foam sleeve filter for a shop vac. It is the correct thickness, open cell, and fairly similar to the original. I just cut it in half (since it is a sleeve), then placed a can of lacquer that happened to be of Loquatious' exact dimensions (3 7/16" OD) on top of it and traced my utility blade around it. By placing it carefully, I was able to cut two circles on one half of it. Then I punched a 3/8" hole in the center and placed it carefully inside the cone. No glue was necessary.
So one $5 filter will provide enough material for 4 Walsh tweeters. In fact, I still have the 2nd half and would be happy to mail it to a fellow AK'er, free of charge. PM me if you want it.
After closely analyzing Loquatious' post a few pages back about replacement foam, but being too cheap to order a full sheet of the stuff plus shipping, I came across what I believe to be a suitable replacement at the local Home Depot.
http://www.homedepot.com/p/Shop-vac-Small-Foam-Sleeve-Filter-SHO9052600/205904905
It is simply the foam sleeve filter for a shop vac. It is the correct thickness, open cell, and fairly similar to the original. I just cut it in half (since it is a sleeve), then placed a can of lacquer that happened to be of Loquatious' exact dimensions (3 7/16" OD) on top of it and traced my utility blade around it. By placing it carefully, I was able to cut two circles on one half of it. Then I punched a 3/8" hole in the center and placed it carefully inside the cone. No glue was necessary.
So one $5 filter will provide enough material for 4 Walsh tweeters. In fact, I still have the 2nd half and would be happy to mail it to a fellow AK'er, free of charge. PM me if you want it.
I read through this whole thread looking for some comment on the late 50s Hegemann water lily tweeter which is very much the same design as the much later Walsh tweeter. Stu Hegemann of HK designed a tweeter with the same tall unterminated cone glued into a standard tweeter voice coil, but he used a piece of graph paper, and didn't bother cutting it into a cone -- it unabashedly looked like a cone made of graph paper. I believe he felt that the shape diminished the major resonance(s) in the cone, and he didn't feel it needed damping inside. The tweeter got good reviews, and Eico made a column speaker that used it in a similar implementation to the Monitor IIs -- open sides and solid top. This was all at the tail end of the mono era. Edwart Tatnall Canby of Audio liked it very much and gave it a most positive review, but he later noted that it produced too much top end in stereo -- the omni effect was nice in mono, but apparently too much with two speakers. I've been looking for a pair ever since I first heard of them, with no luck.
I bought a pair of Monitor IIs (maybe IIas, I can remember) at a tag sale fifteen or twenty years ago. The owners had replaced the Watkinson dual voice coil woofers at some point, and had stuck Radio Shack Linneaum tweeters in the front of the tweeter compartment. I can't remember if the the Walsh tweeters there worked or not, but what I do remember is that there were three pairs of the tweeters in boxes in the garage -- a couple open and the rest still sealed. So I bought the lot. The speakers were okay, but with the wrong woofers, didn't billow my sails (and the cheapness of the wiring and crossover components rubbed me the wrong way) so I sold them to a friend who parted them out, I think.
He also bought the Walsh tweeters and contacted John Strobhein (sp?) of Ohm to ask him about them and John bought the unopened pair because he said he was trying to figure out how to make more.
That was long time ago, and I have not idea what came of that idea.
I bought a pair of Monitor IIs (maybe IIas, I can remember) at a tag sale fifteen or twenty years ago. The owners had replaced the Watkinson dual voice coil woofers at some point, and had stuck Radio Shack Linneaum tweeters in the front of the tweeter compartment. I can't remember if the the Walsh tweeters there worked or not, but what I do remember is that there were three pairs of the tweeters in boxes in the garage -- a couple open and the rest still sealed. So I bought the lot. The speakers were okay, but with the wrong woofers, didn't billow my sails (and the cheapness of the wiring and crossover components rubbed me the wrong way) so I sold them to a friend who parted them out, I think.
He also bought the Walsh tweeters and contacted John Strobhein (sp?) of Ohm to ask him about them and John bought the unopened pair because he said he was trying to figure out how to make more.
That was long time ago, and I have not idea what came of that idea.
Ok, to revive and old thread. I just bought a pair of Infinity Monitor II's. Both Walsh tweets are dead. One must have been replaced as I have both versions shown in this thread. Million dollar question, and it my sound dumb. From what I can can gather from my readings the highs produced are not like a forward firing tweeter. Is it produced by the cone vibrating that is attached to the voice coil. Is that correct?
Walsh's explanation (or maybe it was just adspeak) of how it worked was that the voice coil send ripples down (or, in the tweeter's case, up) the cone. The angle of the cone is intended to line up waves created in the air by the ripples as they pass through the cone - the soundwaves produced in the air by ripples at the beginning move as far outward towards the listener as the ripples moving along the angle of the cone, so you get a straight wavefront. Elegant in theory. We tend to think of the angle of the cone as a way of making the driver pistonic, and if some flexure is designed in, allowing higher frequencies to be emitted from a smaller source so dispersion is better. But Walsh wanted the opposite of pistonic motion.
I am not competent to judge whether the explanation is correct.
I am not competent to judge whether the explanation is correct.
Exactly zero difference, I would guess. That's assuming that by center pole you are referring to the post that sticks up from the pole piece. It's surrounded by (and supports and locates) sound dampening material, the purpose of which is to absorb the backwave produced inside the cone, but I imagine it also absorbs any sonic signature of the post.
It might be possible that the post also radiates heat away from the voice coil and magnet, in which case there might some difference in efficiency in that regard, but if getting rid of heat is the idea, surrounding the post with fiberglass or whatever the stuffing is, isn't exactly the way to accomplish it most successfully. So I doubt it.
It might be possible that the post also radiates heat away from the voice coil and magnet, in which case there might some difference in efficiency in that regard, but if getting rid of heat is the idea, surrounding the post with fiberglass or whatever the stuffing is, isn't exactly the way to accomplish it most successfully. So I doubt it.
Sheepybloke
New Member
So I found a pair of WTLC's in my father-in-law's basement, and they need a little love. The need new foam on the woofers, which (theoretically) isn't too hard and a new finish. But I'm not sure about the walsh tweeters. They need new foam, which I can do (Thanks Loquacious!), but my question is about the cone itself. The cones aren't ripped, but they have indents in a couple places. There are no rip, thankfully! Will the tweeter still work fine if I just push them out, or will the work themselves out if I run a test frequency through?
Jimbo40
Super Member
On my pair of walsh tweets 902-0060 one is dead, the other 7.8 ohms, but old and messy as everyone else's.The coil in the bad one was stuck in the magnet, the top plate was off center and one side of the coil was pinched tight next to its housing large gap on one side very small, and large on the other. no coil movement could have ever happened since it was oem glue of the top plate to the magnet. The coil was destroyed getting it out.
Is there still a repair? The cone are dented but still in tacked. Any advice?
Is there still a repair? The cone are dented but still in tacked. Any advice?
You could contact the guy on the bay who says he repairs them. I tried when I first got mine, but all he gave me were short answers, not much detail. You might have better luck.
That tweeter appears to be a modified dome tweeter, modified by gluing the Walsh ice cream cone to the voice coil. Don't know if the dome is still there down at the bottom, though the post would have to go through it, so unlikely. I can't remember the maker of the tweeter used, but it had a distinctive enough face plate that I recognized it at the time.
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Without pics I'm not sure how damaged the tweeter actually is, but perhaps you or Milleround can install a new voice coil. http://www.millersound.net/
the bottom picture is the version I remember. The upper one looks rather like a Philips on an adaptor plate - perhaps a repair/kludge, or maybe Infinity and or Ohm changed the design. Which suggests that a DIY attempt might succeed, since it looks like it already has been done before.
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