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Old 17th May 2010, 07:10 AM   #1
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Default DIY Headshell with energy sink

I was thinking about building a head shell which would act as an energy sink. The jist of the idea is to have an open rectangular metal frame with a horizontal cross member about 3/16-1/4 inch wide (front) and the other 1/8 inch wide at the back, the side pieces would be about 1/8 of an inch wide. So the centre section is hollow (for the moment). The two cartridge fixing holes would be in the front section. The mounting points would have a washer hard fixed to this frame one at each hole and a third in the centre on the rear cross section so the cartridge makes contact at three points when screwed down. Now comes the interesting part. The open central section would be fitted with five flat prongs about 1/16 of an inch wide and spaced apart, three attached to the front cross piece and two attached to the rear cross piece. These three prongs hard mount to the front cross piece and extend back toward the rear cross piece but stop short and do not touch the rear cross piece. The other two similar prongs attach to the back cross piece and extend toward the front cross piece but again do not make contact at the front. So we have five rectangular prongs three from the front and two from the back all parallel to each other. Then the space between the prongs is filled with a damping compound.
The idea is that energy from the cartridge makes the prongs vibrate and the damping compound eats the vibration up. There may even be a little out of phase cancellation between the front mounted prongs and the rear mounted prongs but I can't be sure about that.
Any comments or suggestions would be most welcome. I hope that I have described this well enough for readers to understand so please ask questions if you are not clear on the design. I look forward to any and all comments. Regards Moray James.
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Old 17th May 2010, 11:49 AM   #2
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Bit of a dilemma.

The only energy coming from the cart is what sneaks through the suspension into the body and then on into the headshell.

The only point of the headshell is to hold the cart in a geometrically stable position with reference to the tonearm pivot and stop any energy from the tonearm getting to the cart.

So there's a compromise between stability and absorption, made more difficult because any energy will find the path of least resistance.

I'd be interested to see what you can do with it. Some careful accelerometer measurement is in order.

I'd go for maximizing the surface contact area between the damping compound and the stiff support structure for the cart, that should maximize the chance of it working.

Here's a sketch. Good luck with it.

http://media.bestkiteboarding.com/mm/damper.jpg
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Old 17th May 2010, 03:52 PM   #3
bgruhn is offline bgruhn  United States
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Quote:
Originally Posted by moray james View Post
I was thinking about building a head shell which would act as an energy sink. The jist of the idea is to have an open rectangular metal frame with a horizontal cross member about 3/16-1/4 inch wide (front) and the other 1/8 inch wide at the back, the side pieces would be about 1/8 of an inch wide. So the centre section is hollow (for the moment). The two cartridge fixing holes would be in the front section. The mounting points would have a washer hard fixed to this frame one at each hole and a third in the centre on the rear cross section so the cartridge makes contact at three points when screwed down. Now comes the interesting part. The open central section would be fitted with five flat prongs about 1/16 of an inch wide and spaced apart, three attached to the front cross piece and two attached to the rear cross piece. These three prongs hard mount to the front cross piece and extend back toward the rear cross piece but stop short and do not touch the rear cross piece. The other two similar prongs attach to the back cross piece and extend toward the front cross piece but again do not make contact at the front. So we have five rectangular prongs three from the front and two from the back all parallel to each other. Then the space between the prongs is filled with a damping compound.
The idea is that energy from the cartridge makes the prongs vibrate and the damping compound eats the vibration up. There may even be a little out of phase cancellation between the front mounted prongs and the rear mounted prongs but I can't be sure about that.
Any comments or suggestions would be most welcome. I hope that I have described this well enough for readers to understand so please ask questions if you are not clear on the design. I look forward to any and all comments. Regards Moray James.
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Moray, What an innovative design approach. I love it. Naturally there will be some fabrication problems to work out but not insurmountable. Going to give it some thought and perhaps a test piece a bit later. Busy right now. I've long felt that the right approach is to keep the energy off the arm wand by absorbing it as close to the source as possible. I do not recall any threads dealing with having an absorbing element (felt pad, silicone damping bar, whatever) between the cartridge body and the headshell. That would achieve some of what your proposed mount is intended to do. in a far less elegant way, but could indicate whether there is any chance of significant improvement in arm performance.

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Old 18th May 2010, 01:37 AM   #4
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Hi,

Quote:
So there's a compromise between stability and absorption, made more difficult because any energy will find the path of least resistance.
Least resistance is what it is all about. Well put.
Question is, how is this best achieved?


Cheers,
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Old 18th May 2010, 03:18 AM   #5
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Quote:
bgruhn: "I do not recall any threads dealing with having an absorbing element (felt pad, silicone damping bar, whatever) between the cartridge body and the headshell."
I wonder if The Music Man isolator is similar in concept. I am skeptical of such product but some say it works for their systems.

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Old 18th May 2010, 03:25 PM   #6
bgruhn is offline bgruhn  United States
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Originally Posted by directdriver View Post
I wonder if The Music Man isolator is similar in concept. I am skeptical of such product but some say it works for their systems.

.
Checked out the musicman isolator link. That is what I've had in mind for a while but done nothing about it for lots of good reasons, mostly lack of a good isolation material. But I think I've seen felt or other semi absorbing pads applied between cartridges and arms before.

My Schroeder clone has had a couple resonances that I've not dealt with much at all and have been plaguing me for a long time. So last night I replaced the mounting crossbar on my Schroeder clone with a 1" square of cork about 3/16" thick. Held it to the arm with the single mounting screw driven into but not all the way through the cork piece. fastened the cartridge to the cork with double sided sticky tape and put the kluge on to play. With the record not turning but the stylus resting on the record virtually all trace of resonances were inaudible even at very high volume settings. Previously, no matter what I did for anti skate settings and alignment of the arm and cartridge there were some tracking error distortions audible in the playback. With very little care in setup of the corkmod several records played from beginning to end with nothing evident. Stayed very consistent for the whole disk. There was some change in the overall character of the sound. Best described as a midrange dulling. Lows and highs were excellent.

So what is this all saying? I think that some form of headshell isolator can make a huge difference in a tone arm. Moray's fingers and absorbers may be the way to go. If I'm looking at it correctly Moray, your rectangular frame is solid all the way around. The fingers are integral with the front and rear cross members of the frame and together with the damping goop suck up the vibrations. This solid frame may kill the midrange dulling I hear with the cork pad. The absorber is key to the idea really working. And finding the right absorber will be the trick. The Ortofon cartridge has a removable weight to provide two selections of cartridge mass. So an Ortofon (OM series) can be adjusted to compensate for the added mass of the Moray Isolator. I wonder if we can come up with the automotive material the MusicMan Isolator uses. Think you guys! Then too, I wonder if it would be better to provide a break in the side rails of the Moray isolator and let the absorber hold the two parts together.

BillG
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Old 18th May 2010, 07:31 PM   #7
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Just for the sake of sharing I have had excellent results with using PVC electrical tape as an interface in all sorts of situations. The thickness is what works for you. Top quality PVC tape is usually 5 mill (that's 5 thousandths of an inch) thick and the cheaper versions are normally about 3 mill thick. The 3 mill thick tape is the one to use. It is thin and soft enough to cold flow out and sticks down under pressure like a suction cup. Due to the thinness it does not add much compliance and adds just enough damping over a very wide band to make it a useful tool to have.

Bill: the prongs or tines should be rectangular in shape so that they will only be able to vibrate up and down not sideways. This is important as any side to side motion will impact the cartridge tracking where up and down is pretty much a non issue. For a damping compound I was thinking that a good starting place would be Duct Seal used in outdoor electrical and HVAC work. Both softer and thicker materials could be tried. You will not be using much so I don't expect added mass to be a problem. I would not break both side rails as you need the strength and a solid coupling to the tonearm. I do think that the head shell could be made in a "C" shaped three sided rectangle then more tines could be incorporated.
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Old 19th May 2010, 07:21 AM   #8
bgruhn is offline bgruhn  United States
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Quote:
Originally Posted by moray james View Post
Just for the sake of sharing I have had excellent results with using PVC electrical tape as an interface in all sorts of situations. The thickness is what works for you. Top quality PVC tape is usually 5 mill (that's 5 thousandths of an inch) thick and the cheaper versions are normally about 3 mill thick. The 3 mill thick tape is the one to use. It is thin and soft enough to cold flow out and sticks down under pressure like a suction cup. Due to the thinness it does not add much compliance and adds just enough damping over a very wide band to make it a useful tool to have.

Bill: the prongs or tines should be rectangular in shape so that they will only be able to vibrate up and down not sideways. This is important as any side to side motion will impact the cartridge tracking where up and down is pretty much a non issue. For a damping compound I was thinking that a good starting place would be Duct Seal used in outdoor electrical and HVAC work. Both softer and thicker materials could be tried. You will not be using much so I don't expect added mass to be a problem. I would not break both side rails as you need the strength and a solid coupling to the tonearm. I do think that the head shell could be made in a "C" shaped three sided rectangle then more tines could be incorporated.
Hi Moray,
Did some crude sketches tonight to just about scale to get a better idea of what we are trying to do. Used your 1/16 - 1/8 - 1/4 dimensions for starters and an overall frame size of about 1" square. This fits 5 tines into it nicely. The one thing that I questioned was how thick to make the tines and the frame member(s). To keep a rectangular cross section of the tines, to restrict them to up and down motion, looks like they should be on the order of .015" to .020". The frame itself could be anything from 1/16" to 1/8" thick. Basically we are looking at a sheet metal structure. Am I interpreting this as you intended it to be?

(Leave the damping compound out, and mount it on an air bearing arm and the escaping air will play the thing like a harmonica.)

Whilst playing around with the concept, pencil in hand, the thought occurred to me that thin tines might not provide as much energy sink as we are needing. If the energy flows along the paths of least resistance, we may achieve greater transfer/damping if instead of tines we use a thicker one piece frame perforated by many holes of various sizes and filled with the damping material.
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Old 19th May 2010, 07:14 PM   #9
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Hey Bill: that sounds right. If a three sided frame structure were used there is no reason why longer tines could not be used to get additional resonant action going and so increase the amount of energy sinking. Further there is no reason why the arm could not be "T" shaped with the solid "T" section having the cartridge mounting holes. Then you could have tines protruding horizontally along each side of the main shaft for even more resonant action. The tines could be adjusted for length to cover a wide bandwidth. If the tines were long at the tip end of the assembly you could also get some added stability along the lines of the Frank Van Alstine's out rigger weights. Two birds with one stone.
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Old 20th May 2010, 03:31 PM   #10
bgruhn is offline bgruhn  United States
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Originally Posted by moray james View Post
Hey Bill: that sounds right. If a three sided frame structure were used there is no reason why longer tines could not be used to get additional resonant action going and so increase the amount of energy sinking. Further there is no reason why the arm could not be "T" shaped with the solid "T" section having the cartridge mounting holes. Then you could have tines protruding horizontally along each side of the main shaft for even more resonant action. The tines could be adjusted for length to cover a wide bandwidth. If the tines were long at the tip end of the assembly you could also get some added stability along the lines of the Frank Van Alstine's out rigger weights. Two birds with one stone.
Hi Moray, Seems to me we are getting far afield from the goals of your original post. Longer tines, more resonant action etc. when what we were trying to do was kill the coupled energy from the cartridge body from getting onto the arm wand. My first take on the tines was what a neat way to get more of this unwanted energy absorbed. Put more of it in contact with the damping medium. By the time we have the tines packed with absorber, there is no way they will resonate.

So I tried a simple test with a cork mounting piece and observed some good results, and some not so good. To further this approach, still not getting into the complexities of fabrication for the "tines approach", I made a damped version of the "T" bar cartridge mount piece used on my magnetically suspended tone arm. Made a new T bar from the same wood as the arm wand (mahogany). Same dimensions as the aluminum piece. Then I drilled a center hole for the screw which holds it to the arm wand. then added 4 more holes, 2 on either side of the center hole. These 4 were about as large in diameter as could be gotten into T bar. Filled these holes with modeling clay (plasticine) , attached the cartridge with double sided sticky tape, mounted it on the arm and listened. Here was a major improvement. Clear, clean, unmuddied midrange, super sound stage etc. At full volume setting, there was but the slightest trace of arm wand resonance. So again I am convinced that stopping the energy as close to the source is the way to go. Keep it out of the rest of the arm and TT assembly. The damping material will absorb the energy and dissipate it as heat (not much) rather than trying to lead it off unattenuated and un-reflected (impedance matching the transmission line) to be absorbed later on down the chain. Need to do a bit more work on a slightly bigger piece and a better way of attaching the cartridge than a bit of sticky tape a quarter of an inch wide. Got some ideas for a better shape and size. Just got to do it.
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