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#1
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Microphone Head Grille Effects
In this post I'll quote a number of experts who've posted to
rec.audio.pro over the years on the subject of mic head grille effects. Though they may differ on other issues, you'll see agreement that head grilles play an important role in the sound of a mic. I'll go on to describe some head grille mods I recently made to a couple of mics. Recently, while making improvements to an Oktava ML-52 I finally gave up trying to stop the head grille assembly from ringing – I took the entire assembly off and rolled a new wire mesh grille for it in the shape of an ML-16. (as seen on this page: http://www.is.svitonline.com/ustrizza/mics/mics.htm ) After rolling the new screen I made some reference recordings with it installed on the mic. I was concerned about protecting the ribbons from wind blasts so I removed the grille and added a layer of fine silk to the inside of the wire mesh. When I retested the mic with the silk/wire screen installed, I found that both the LF and HF were rolled-off and the mic had lost some transient detail. Ok, time for a Google groups search of rec.audio.pro for a lesson in mic head grille issues. The quotes below can be found in their context by doing a Google groups search for the author's name and the first few words of the quote. Ty Ford had an interesting observation about the Neumann M149: "...The M149 head grille is less restrictive than those of the U47, U87, U89, TLM170. It's so transparent that you can see the capsule rather easily through the grille, resulting in a noticeable lift in the 7KHz-10KHz range, and a bit beyond". Ty goes on to quote Karl Winkler of Neumann USA who said: "The old-style head grille has three layers (of wire) that affected the sound more than we wanted. They provide a certain amount of acoustic compression". Regarding the difference between one and two-layer grilles, Greg Gualtieri wrote: "The Horch (U47 replica) has a single-mesh grille with fairly wide spacing. I took some fine mesh screen and wrapped it around the head of the mic to mimic the dual mesh of the U47/48. The mids softened dramatically". So – an audible difference between one, two and three layers of wire mesh? In an earlier post David Josephson went even further when he wrote: "B&K lab mics, for instance, sound a lot better when you take off the protection grille and let the diaphragm be out in the air, rather than behind a low-Q Helmholtz resonator that's formed by the grille cavity." The omnipresent, but seldom heard from Dave Royer pointed out: "..problems due to reflections inside the head grille ... can make life miserable. A two inch diameter mic body with a capsule in the middle means there's one inch to the screen. Sound will also pass by the capsule inside the head grille, bounce off the inside of the head grille and back onto the rear membrane. That sound will either be subtracted or added to the front sound, depending on whether the rear membrane is in or out of phase with the front membrane." Another mic designer, Klaus Heyne wrote: "...tubes have less to do with it than you think...most of the sound is from the capsule, followed by the grille shape, then the output transformer. The tube is dead last". And David Bock of Soundelux wrote "...the U47's peak is at 10k. This peak is cause solely by the headgrille, which also causes the 6k to 9k 2dB dip, and rolloff above 12k. The capsule is remarkably flat from 10k to 15k without the headgrille." By now I had the impression those bits of wire in front and back of the capsule are important. I pulled the silk out of the open weave wire mesh on the ML-52, restored the top end clarity, and now use a popper stopper out in front. I didn't stop there, I survey my "bottom feeder" mic collection and noticed my MK319, Studio Projects C1 and MXL Royer tube mod mic all use two-layer wire mesh screens. I have a preference for clear, open high frequency response – just the sound of the capsule as much as possible with no mechanical HF lift devices. So, one by one, I pulled out the fine weave grille screen on all three mics to leave just the more open, heavier grille screen. Results? - Incremental improvement in transient detail and accuracy in the MK319 and MXL. In fact, it's really surprising how "alive" this particular MK-319 is now. (This 319 has been "Dorsey modded" - FET, Rs, Cs, plus it has my head grille mod, head cavity foam absorbers installed and perforated mechanical HF lift disc removed). I have not tested the C1 against my reference recording yet to see if the lower internal reflections afforded by removing the fine wire mesh changes the rather pronounced top boost this mic is known for. So, once again, a bunch of cheap mics and Google groups makes for an interesting day of learning and DIY pleasure. Best, MJ |
#2
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Microphone Head Grille Effects
Good synopsis of what the experts have said, Mike. And goodonya for
experimenting and sharing! Based on the subject line, I thought you were going to talk about one of my pet peeves: the whistling sound that breath from a "wh" sound makes when it crosses the coarse screen on a handheld mic. I've actually put nylon mesh on the *outside* of my KMS-105 and AKG 535 to deal with this. I didn't even think to record before/after to listen for changes in response, and I doubt it makes a difference for live mics like this. But for studio, I think it's interesting to hear how much of an effect the grille can have. I'm wondering if there is an "ideal grille" that is a fine, open mesh that is spherical around the diaphragm and some minimum distance from it? George Reiswig Song of the River Music "Michael Joly" wrote in message om... In this post I'll quote a number of experts who've posted to rec.audio.pro over the years on the subject of mic head grille effects. Though they may differ on other issues, you'll see agreement that head grilles play an important role in the sound of a mic. I'll go on to describe some head grille mods I recently made to a couple of mics. Recently, while making improvements to an Oktava ML-52 I finally gave up trying to stop the head grille assembly from ringing - I took the entire assembly off and rolled a new wire mesh grille for it in the shape of an ML-16. (as seen on this page: http://www.is.svitonline.com/ustrizza/mics/mics.htm ) After rolling the new screen I made some reference recordings with it installed on the mic. I was concerned about protecting the ribbons from wind blasts so I removed the grille and added a layer of fine silk to the inside of the wire mesh. When I retested the mic with the silk/wire screen installed, I found that both the LF and HF were rolled-off and the mic had lost some transient detail. Ok, time for a Google groups search of rec.audio.pro for a lesson in mic head grille issues. The quotes below can be found in their context by doing a Google groups search for the author's name and the first few words of the quote. Ty Ford had an interesting observation about the Neumann M149: "...The M149 head grille is less restrictive than those of the U47, U87, U89, TLM170. It's so transparent that you can see the capsule rather easily through the grille, resulting in a noticeable lift in the 7KHz-10KHz range, and a bit beyond". Ty goes on to quote Karl Winkler of Neumann USA who said: "The old-style head grille has three layers (of wire) that affected the sound more than we wanted. They provide a certain amount of acoustic compression". Regarding the difference between one and two-layer grilles, Greg Gualtieri wrote: "The Horch (U47 replica) has a single-mesh grille with fairly wide spacing. I took some fine mesh screen and wrapped it around the head of the mic to mimic the dual mesh of the U47/48. The mids softened dramatically". So - an audible difference between one, two and three layers of wire mesh? In an earlier post David Josephson went even further when he wrote: "B&K lab mics, for instance, sound a lot better when you take off the protection grille and let the diaphragm be out in the air, rather than behind a low-Q Helmholtz resonator that's formed by the grille cavity." The omnipresent, but seldom heard from Dave Royer pointed out: "..problems due to reflections inside the head grille ... can make life miserable. A two inch diameter mic body with a capsule in the middle means there's one inch to the screen. Sound will also pass by the capsule inside the head grille, bounce off the inside of the head grille and back onto the rear membrane. That sound will either be subtracted or added to the front sound, depending on whether the rear membrane is in or out of phase with the front membrane." Another mic designer, Klaus Heyne wrote: "...tubes have less to do with it than you think...most of the sound is from the capsule, followed by the grille shape, then the output transformer. The tube is dead last". And David Bock of Soundelux wrote "...the U47's peak is at 10k. This peak is cause solely by the headgrille, which also causes the 6k to 9k 2dB dip, and rolloff above 12k. The capsule is remarkably flat from 10k to 15k without the headgrille." By now I had the impression those bits of wire in front and back of the capsule are important. I pulled the silk out of the open weave wire mesh on the ML-52, restored the top end clarity, and now use a popper stopper out in front. I didn't stop there, I survey my "bottom feeder" mic collection and noticed my MK319, Studio Projects C1 and MXL Royer tube mod mic all use two-layer wire mesh screens. I have a preference for clear, open high frequency response - just the sound of the capsule as much as possible with no mechanical HF lift devices. So, one by one, I pulled out the fine weave grille screen on all three mics to leave just the more open, heavier grille screen. Results? - Incremental improvement in transient detail and accuracy in the MK319 and MXL. In fact, it's really surprising how "alive" this particular MK-319 is now. (This 319 has been "Dorsey modded" - FET, Rs, Cs, plus it has my head grille mod, head cavity foam absorbers installed and perforated mechanical HF lift disc removed). I have not tested the C1 against my reference recording yet to see if the lower internal reflections afforded by removing the fine wire mesh changes the rather pronounced top boost this mic is known for. So, once again, a bunch of cheap mics and Google groups makes for an interesting day of learning and DIY pleasure. Best, MJ |
#3
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Microphone Head Grille Effects
Michael,
I only have a few data points for your collection, plus some advice: Incremental improvements in sound quality are great, but let's take care to test everything that might be relevant after making a change. Here's my story: Earlier this year I bought two used AKG C 414 B-ULS microphones, had them checked out by AKG in Nashville, then sent them to be modified by a well respected (including by me) person who specializes in upgrading studio equipment. The modifications included removing one layer of metal screening from around the capsules, and the microphones' output transformers were also removed. With that person's knowledge--he is notably the opposite of an egomaniac-- I then sent one of the modified microphones to some friends in Germany to test. My friends know their way around condenser microphones and have a test setup that I trust. Also, a stock (unmodified) C 414-B ULS was on hand there for comparison--these people do, after all, pay attention to what's on the market as part of their work. After making the standard frequency and polar response measurements, the nice people in Germany decided to check out the modified microphone's immunity to RFI. Unfortunately the modified microphone was found to be highly susceptible to interference. Large amounts of noise resulted from using a mobile phone anywhere in the same room. No such problem was found with the stock microphone. So while the removal of the output transformer could also be implicated in this problem, let's please consider that grounded metal mesh screens may have multiple functions, and let's test accordingly, OK? Also, I've seen one instance in which a more "open" design for a screened capsule head caused a greater increase in that capsule's _low frequency_ response than in its high frequency response. It would be very nice to understand the physical reason for that, but at present I sure don't. Thus I suspect that as non-experts, our common-sense expectations about the effects of screens on the sound of a capsule may be misplaced, too simple, or perhaps both--and I suggest proceeding cautiously before we turn any unproven assumptions into dogma. --Since some people here can probably guess who did the above-mentioned mods and who did the aforementioned testing, let me add that in other respects the modified C 414 B-ULS was found to be improved: 2 dB lower noise, output impedance reduced by half, and improved (i.e. increased) high frequency response--though the degree of that was considered rather slight as it was told to me. None of the above should be construed as an endorsement by anyone of anything (nor the contrary, if you please); it's just data points. Let's add 'em to the pile and keep on having open minds, at least until someone who knows more about this than we do comes along to explain it to us. --best regards |
#4
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Microphone Head Grille Effects
David,
Thanks for the story, data points for the collection and your words of caution - especially your comments about RF immunity. I too would like to see as many knowledgable points of view as possible show up here. As a short research project I restricted myself just to the rec.audio.pro archives - the sort of activity a curious student might engage in and only quoted from that source. However, I am aware of Stephen Paul's seminal series of articles on condenser mic design in Mix Magazine many years ago. As a side note, I feel a discussion of this topic might have long-lasting educational value and might be more readily found here on the public USENET via Google groups search than on the private bulletin boards subject to editorial oversight. Thanks for reading and commenting! |
#5
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Microphone Head Grille Effects
On Thu, 18 Dec 2003 07:55:18 -0500, Michael Joly wrote:
As a short research project I restricted myself just to the rec.audio.pro archives - the sort of activity a curious student might engage in and only quoted from that source. However, I am aware of Stephen Paul's seminal series of articles on condenser mic design in Mix Magazine many years ago. Michael, Do you know off hand which issues of Mix Magazine carried the Stephen Paul articles? Very interesting observations. Thanks for sharing guys!!! Nick =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= http://www.songbirdofswing.com Nick Busigin Visit Our Indie Jazz CD Construction Project! =-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-=-= |
#6
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Microphone Head Grille Effects
The modifications to the output should be the prime suspect for your RF
problems.... A single layer of screen should be sufficient as long as it still has a low resistance connection to the rest of the case. The RF wavelength of the holes should be small enough to get the job done. Regards Eric "David Satz" wrote in message m... Michael, I only have a few data points for your collection, plus some advice: Incremental improvements in sound quality are great, but let's take care to test everything that might be relevant after making a change. Here's my story: Earlier this year I bought two used AKG C 414 B-ULS microphones, had them checked out by AKG in Nashville, then sent them to be modified by a well respected (including by me) person who specializes in upgrading studio equipment. The modifications included removing one layer of metal screening from around the capsules, and the microphones' output transformers were also removed. With that person's knowledge--he is notably the opposite of an egomaniac-- I then sent one of the modified microphones to some friends in Germany to test. My friends know their way around condenser microphones and have a test setup that I trust. Also, a stock (unmodified) C 414-B ULS was on hand there for comparison--these people do, after all, pay attention to what's on the market as part of their work. After making the standard frequency and polar response measurements, the nice people in Germany decided to check out the modified microphone's immunity to RFI. Unfortunately the modified microphone was found to be highly susceptible to interference. Large amounts of noise resulted from using a mobile phone anywhere in the same room. No such problem was found with the stock microphone. So while the removal of the output transformer could also be implicated in this problem, let's please consider that grounded metal mesh screens may have multiple functions, and let's test accordingly, OK? Also, I've seen one instance in which a more "open" design for a screened capsule head caused a greater increase in that capsule's _low frequency_ response than in its high frequency response. It would be very nice to understand the physical reason for that, but at present I sure don't. Thus I suspect that as non-experts, our common-sense expectations about the effects of screens on the sound of a capsule may be misplaced, too simple, or perhaps both--and I suggest proceeding cautiously before we turn any unproven assumptions into dogma. --Since some people here can probably guess who did the above-mentioned mods and who did the aforementioned testing, let me add that in other respects the modified C 414 B-ULS was found to be improved: 2 dB lower noise, output impedance reduced by half, and improved (i.e. increased) high frequency response--though the degree of that was considered rather slight as it was told to me. None of the above should be construed as an endorsement by anyone of anything (nor the contrary, if you please); it's just data points. Let's add 'em to the pile and keep on having open minds, at least until someone who knows more about this than we do comes along to explain it to us. --best regards |
#8
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Microphone Head Grille Effects
In Article , "Eric K. Weber"
wrote: The modifications to the output should be the prime suspect for your RF problems.... A single layer of screen should be sufficient as long as it still has a low resistance connection to the rest of the case. The RF wavelength of the holes should be small enough to get the job done. Regards Eric Persactly! I think I found this out while reviewing the SolidTube. Even though the top and bottom halves of the mic body were fitted together, I found with a VOM that there was no ground continuity between the bottom and top. I used a clip lead to make the connection and the RFI went away. AKG later included a small piece of metal where the body parts joined to ensure that the headgrille was grounded. I received no money, but a nice pat on the back for that sleuthery. Regards, Ty Ford **Until the worm goes away, I have put "not" in front of my email address. Please remove it if you want to email me directly. For Ty Ford V/O demos, audio services and equipment reviews, click on http://www.jagunet.com/~tford |
#9
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Microphone Head Grille Effects
http://www.is.svitonline.com/ustrizza/mics/mics.htm )
Interesting stuff! I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. One little neat thing I happened upon: If you are looking for a less fine mesh for a small diaphragm capsule, the little discs for aeration filters on kitchen and bathroom taps are an intriguing possibility. Too small for a c-60, by a hair, but they might work on something else. Yes, they are way more coarse (though less than a window screen) but that might actually sound better. I suppose that the percentage of open area in addition to "fibre count" are the too main parameters. Then the material, conductive/non- conductive, stiff/flexible and a whole bunch of other little details come into play. Rob R. |
#10
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Microphone Head Grille Effects
Have a look at http://www.mcmaster.com/ they stock very fine screen...
Rgds: Eric "Rob Reedijk" wrote in message ... http://www.is.svitonline.com/ustrizza/mics/mics.htm ) Interesting stuff! I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. One little neat thing I happened upon: If you are looking for a less fine mesh for a small diaphragm capsule, the little discs for aeration filters on kitchen and bathroom taps are an intriguing possibility. Too small for a c-60, by a hair, but they might work on something else. Yes, they are way more coarse (though less than a window screen) but that might actually sound better. I suppose that the percentage of open area in addition to "fibre count" are the too main parameters. Then the material, conductive/non- conductive, stiff/flexible and a whole bunch of other little details come into play. Rob R. |
#11
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Microphone Head Grille Effects
Use the following to find info on available types of wire cloth...
www.mcmaster.com click woven wire cloth click woven wire cloth again.... click printers and stencil grade.... mesh as fine as 400x400 to the inch is available... Rgds: Eric "Rob Reedijk" wrote in message ... http://www.is.svitonline.com/ustrizza/mics/mics.htm ) Interesting stuff! I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. One little neat thing I happened upon: If you are looking for a less fine mesh for a small diaphragm capsule, the little discs for aeration filters on kitchen and bathroom taps are an intriguing possibility. Too small for a c-60, by a hair, but they might work on something else. Yes, they are way more coarse (though less than a window screen) but that might actually sound better. I suppose that the percentage of open area in addition to "fibre count" are the too main parameters. Then the material, conductive/non- conductive, stiff/flexible and a whole bunch of other little details come into play. Rob R. |
#12
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Microphone Head Grille Effects
I am really glad that Eric has posted this. Not only is it useful for mesh,
but it also has things like springs. I have a capsule that needs a spring, and while the Home Depot one I put in is workable, McMaster seems to have an excellent selection. Rob R. Eric K. Weber wrote: Use the following to find info on available types of wire cloth... www.mcmaster.com click woven wire cloth click woven wire cloth again.... click printers and stencil grade.... mesh as fine as 400x400 to the inch is available... Rgds: Eric "Rob Reedijk" wrote in message ... http://www.is.svitonline.com/ustrizza/mics/mics.htm ) Interesting stuff! I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. One little neat thing I happened upon: If you are looking for a less fine mesh for a small diaphragm capsule, the little discs for aeration filters on kitchen and bathroom taps are an intriguing possibility. Too small for a c-60, by a hair, but they might work on something else. Yes, they are way more coarse (though less than a window screen) but that might actually sound better. I suppose that the percentage of open area in addition to "fibre count" are the too main parameters. Then the material, conductive/non- conductive, stiff/flexible and a whole bunch of other little details come into play. Rob R. |
#13
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Microphone Head Grille Effects
Glad to see you found it of use.... you might also look at their
competition... http://www.mscdirect.com/ Rgds: Eric |
#14
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Microphone Head Grille Effects
Rob Reedijk wrote in message
Trying to find a supplier of fine mesh is a bit of trial. Small Parts has a good supply of stainless steel wire screen: http://www.smallparts.com/products/d.../CX,%20CXX.cfm You can select weave style, wire size, width of opening and % open area. 3"x6", 6"x12" and 12"x24" are their standard sizes. |
#15
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Microphone Head Grille Effects
In Article , Rob Reedijk
wrote: http://www.is.svitonline.com/ustrizza/mics/mics.htm ) Interesting stuff! I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. One little neat thing I happened upon: If you are looking for a less fine mesh for a small diaphragm capsule, the little discs for aeration filters on kitchen and bathroom taps are an intriguing possibility. Too small for a c-60, by a hair, but they might work on something else. Yes, they are way more coarse (though less than a window screen) but that might actually sound better. I suppose that the percentage of open area in addition to "fibre count" are the too main parameters. Then the material, conductive/non- conductive, stiff/flexible and a whole bunch of other little details come into play. Rob R. The new Neumann broadcast mic has a rectangular screen mounted inside the headgrille, a bit infront of the diaphragm. The Neumann popper stopper uses tricot. Do you need the wire mesh, or would tricot material work? Regards, Ty Ford **Until the worm goes away, I have put "not" in front of my email address. Please remove it if you want to email me directly. For Ty Ford V/O demos, audio services and equipment reviews, click on http://www.jagunet.com/~tford |
#16
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Microphone Head Grille Effects
Ty Ford wrote:
I am going through some questions about mesh densities. I have some c-60s, and one of them needs the mesh replaced. AKG no longer stocks it and are not very helpful in providing specs (what is the per square inch count? material? etc) Trying to find a supplier of fine mesh is a bit of trial. However, I am eventually going to be getting hold of some samples from pulp & paper people. My dad worked in the industry for 30 or 40 years, and they know a lot about fine mesh. They deal in some pretty fine densities. The new Neumann broadcast mic has a rectangular screen mounted inside the headgrille, a bit infront of the diaphragm. The Neumann popper stopper uses tricot. Do you need the wire mesh, or would tricot material work? I really don't know. The mesh that is in there is wire. But it is supported by a metal surface with larger holes in it, so stiffness is not an actual requirement. Rob R. |
#17
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Microphone Head Grille Effects
Rob Reedijk wrote:
I really don't know. The mesh that is in there is wire. But it is supported by a metal surface with larger holes in it, so stiffness is not an actual requirement. So, first see if a magnet will pick it up. If it will, it's steel. Otherwise, scrape the end of one of the wires and look with a magnifier to see if it is brass-colored. If so, it's probably brass. A linen tester or some other magnifier with a measuring scale will help you count the number of wires per inch. If McMaster-Carr and Small Parts don't have it, Applied Industrial Technologies or MSC might. --scott -- "C'est un Nagra. C'est suisse, et tres, tres precis." |
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