how do you re tension LD caps?

[theom]

Often I hear folks talk about getting their U87's or other LD mic's "re-tensioned".
I have a bunch of cheap mics and some older beater 87's and would like to experiment.

Do you need a jig? What is the procedure?

Yes I know I am asking for trouble, I am prepared to **** up some perfectly good (or not so good ) mics.

I assume there is glue holding the mylar to the hoop, What solvent do you use? What type of glue?
It the tension controled by the screws around the element, like a drum head? or are they just there to hold the tension determined when the mylar is glued?

It the tension measured is some way, some mico tension feeler gizmo?

I know it is a fine art, But can't I at least finger paint?

[Nutmeg II.]

Get new mics and send your old mics to me!

[Etnier]

I use my Milwaukee heat gun. Gotta be quick, though!!!!!

[theom]

Can someone point me to the klaus hyne (sp?) ariticle I have heard about concerning re tensioning LD capsules?

[Tim Farrant]

woooooooo - sounds scary to me - and what's wrong with an ole flabby diaphram anyway ?

Sorry not much help, but sounds like a job for those in the know !!

Tim.

[rylos]

but sounds like a job for those in the know !!

Even they had to start somewhere.

[Bob Olhsson]

You would need to acquire the skills and gear needed to build and test condenser microphones. I'd start by visiting some mike factories to see how they do it.

[Bernd G]

I recently had a long discussion with Klaus Heyne about this subject (find his article on www.germanmasterworks.com). You will find that, in good German tradition, he would be horrified by anyone else than a "certified" expert to lay hand on anything as delicate as re-tensing (is this a word?) a microphone diaphragm. Now, being slightly less German as he is, I think it is a great opportunity to experiment with some old and otherwise worthless microphones. As a teenager I was in a bind and strung a piece of aluminum foil between the magnets in my broken Beyer M 500. Beyer was completely mortified by my initiative - but fact is that the mic did work and the gig was saved. I would think of this work being similar to tuning a drum (tympani comes to mind). You could end up making a very bad sounding mic, or in worst case scenario, distroy the diaphragm and possibly more. Or you could be lucky and create a very interesting sounding, unique instrument. Working with microphones can be similar to tuning pianos, there are artists, craftmen (women) and hacks. I suggest you ask more questions (ie. Stephen Sank) and then try your luck on some stuff that has little value (not your vintage U 87). Good luck

Cheers

[faeflora]

It's a very fine craft and you'll screw up your mics. Don't mess around especially on 87s.

[faeflora]

Originally posted by Etnier
I use my Milwaukee heat gun. Gotta be quick, though!!!!!

This is actually a great reccomendation. Yesterday I dried my hair and then made my '47 diaphragm nice and taut! I once melted the diaphragm on an '87 but it was ok because I replaced it with condom latex dipped in solder!

[gyraf]

But on the other hand, if you have a capsule that is broken anyway, you could as well try fixing it. If not for anything else, then to demystify the inner workings of microphone capsules. There is SO much mumbo-jumbo and black magic surrounding that area. But in fact, there is a lot you can do yourself, if you can afford the chance of ruining the capsule. Which makes experimenting logical for otherwise broken capsules.

Trying to discourage that seems wrong to me...


Jakob E.

[McQ]

Originally posted by gyraf
But on the other hand, if you have a capsule that is broken anyway, you could as well try fixing it. If not for anything else, then to demystify the inner workings of microphone capsules. There is SO much mumbo-jumbo and black magic surrounding that area. But in fact, there is a lot you can do yourself, if you can afford the chance of ruining the capsule. Which makes experimenting logical for otherwise broken capsules.

Trying to discourage that seems wrong to me...


Jakob E.

Then, in the interest in "myth-busting", send THEOM your mics to mess with...

Modifying healthy gear by the inexperienced and unknowledgable should be subject to the conventional wisdom of the stock market: never invest what you can't afford to lose.

[theom]

Yup, The mics I wanted to mess with are not really worth much. There isn't much I can find online about mic capsules and there manufacture. Some great articles by SP about his ultra low mass diaphragms. But nothing about how exactly they are tensioned. I have read that the B&K s are welded on due to their super high tension. I just wanted to know the process involved in tensioning and re tensioning a regular mylar capsule.

I might try the heat gun.

Also I removed the windscreen on a mxl v67G and a nady/mxl 2001. A huge difference in sound! I thought I'd get more RF but it didnt seem to get any more.

The V67G with no screen and a royer metal pop filter with a regular stocking pop filter on top sounded really super open and up front on female vocals.

One cough and it might kill the tension I suppose but hey It's an experiment.

[gyraf]

Hi THEOM,

I don't think there's a way to re-tention diagphrames, other than possibly the heating you mentioned. Don't know if that will work though.

The diagphrame is glued to a ring that is screwed tightly to the backplate, often with a thin spacer to keep the distance to the backplate.

There's no way to retention the membrane material, other than removing the old one, stretching a new one, and glueing it onto the ring again.

SP - allthough he writes a lot of articles about the subject, - does in fact NOT let you know anything about what happens in the actual process. Makes me think if it's that hard to do after all?

In the AKG CK12-types of capsules, the degree of membrane stretching - it's resonant frequency - is important, as this is part of the acoustic equation. The Neumann type capsules are much less dependent on exact membrane resonant frequency, as acoustics are primarily regulated by backplate design in these types. Try doing a couple of patent searches - be patient, these patents are well hidden!

Membrane material - gold evaporated mylar - is hard to get hold on in small quantities. You could try scientific material suppliers, or possibly Josephson - he is a really nice guy. He is often found in the Yahoo group "MIC-DIY'ers"

Jakob E.

[faeflora]

AKKK I was joking about the heat gun! I hope the other guy was too!

[Bernd G]

Originally posted by gyraf
Hi THEOM,

I don't think there's a way to re-tention diagphrames, other than possibly the heating you mentioned. Don't know if that will work though.

The diagphrame is glued to a ring that is screwed tightly to the backplate, often with a thin spacer to keep the distance to the backplate.

There's no way to retention the membrane material, other than removing the old one, stretching a new one, and glueing it onto the ring again.

SP - allthough he writes a lot of articles about the subject, - does in fact NOT let you know anything about what happens in the actual process. Makes me think if it's that hard to do after all?

In the AKG CK12-types of capsules, the degree of membrane stretching - it's resonant frequency - is important, as this is part of the acoustic equation. The Neumann type capsules are much less dependent on exact membrane resonant frequency, as acoustics are primarily regulated by backplate design in these types. Try doing a couple of patent searches - be patient, these patents are well hidden!

Membrane material - gold evaporated mylar - is hard to get hold on in small quantities. You could try scientific material suppliers, or possibly Josephson - he is a really nice guy. He is often found in the Yahoo group "MIC-DIY'ers"

Jakob E.

Nice post Jakob,
Yes, it does make you wonder if it is not mostly "job security" for the few "initiated".
we recently did a few tests with replacing capsules. We had a few old C 12a lying around and mounted one of the capsules on a Studio Projects C3 (a condenser is a condenser, my tech said). It worked just fine. It was very interesting to evaluate the sonic qualities of an original C12 a, a C3 with the CK 12 capsule and an original C3 with an Averill Lavigne type of voice. I only wished the C12a nuvistor tube weren't as noisy - it is a nice mic otherwise. Perhaps it is just this particular tube - a replacement might change things. Also, it seems that in the SP C3 it is indeed the capsule that provides most of its (perhaps overly so) bright sibilant sound. To make a long story short - this test fostered my interest in experimenting with diaphragm tension - I do think it is very similar to tuning a tympani - screws on the ring that change the tension. Now, if I could just "tap" the diaphragm like you would on a tympani... .

Cheers

[gyraf]

Actually, from what I've learned, the membrane stretching is done prior to glueing it onto the ring that is screwed onto the backplate. The "tapping" is done by a speaker beneath the membrane in the tensioning jig, looking for mechanical resonance at specific frequencies.

Adjusting the screws around the edge of the capsule may not give you any benefit other than maybe changing the spacing behind the membrane a bit by compressing the spacer ring a bit.

This can maybe be used for small adjustments in sensitivity (important for well-behaved directivity patterns..) but not for stretching the membrane. It's not made like a drumhead, I think - at least not the capsules I have taken apart.

A friend of mine, Tim Campbell, has gathere'd quite a collection of non-BS information about microphone capsules - that he may be willing to share if you're genuinely interested. His adress is tim(at)timcampbell(dot)dk

On the matter of using a heat gun, I've actually seen him removing a small dent in a CK12 capsule (mylar membrane) with a heatgun. That was no joke - but don't expect miracles here!!

Jakob E.

[Bernd G]

Thank you Jacob,

I will contact your friend Tim for some detailed information on microphone capsule tensioning. I gather from what you are saying that there is no way to change the frequency response of the diaphragm without removing it from the backplate and that the screws on the ring are only holding the diaphragm in place but have no "stretching" function? I am curious.
Cheers

[gyraf]

Some non-bs (diy) articles about microphone capsules:

http://www.conditionedresponse.com/D...nes/index.html

Jakob E.

[Stephen Paul]

a) Do not use a heat gun.

b) It has nothing to do with job security in the sense that if they'd figured out how I do sub 3 micron reliably and successfully to 34mm capsules, they'd have done it. Hell, they've already ripped off my three to the tune of what must be by now approaching a hundred thousand or more capsules...

c) The method we use is proprietary for several reasons. I designed, machined and constructed our tensioning jig, and have simply drawn the line at the idea of publishing every single one of the hundreds of secrets to doing it properly.

d) If you think I'm full of shit, then be my guest. But I don't think my time of no competition would have been as long as twelve years, if it was so easy and we just made it sound hard. (You guys kill me sometimes...)

e) If you try and do it knowing nothing whatever about the physics of capsule design, coating technology, physics, acoustics, machining, and a good basic grounding in how it all works, you'll learn quickly what separates the good mikes that are repeatably good, is that very design knowledge, and without it, it's not black magic.

It's magic, but not black. But it's really not just magic, it is alchemy, or the successful merging of magic and science into the third level of reality, and it's results, which is what is so difficult to find in today's products, and why we're still here after twenty years and own claim to almost every important first in microphone technological advancement, since 1984. (Just for the record, where I and my few compatriots don't seem to agree is that transformerless mikes are not an improvement...)

But if you think you have the right to just ask for and be given what took me hundreds of thousands of bucks to learn and make possible, after already having the experience at the hands of manufacturers and independents I had, then that's a problem in your own understanding of what it really takes, and why eventually, even I, who published more of the true secrets than anyone in mike history, wish sometimes I had drawn the line just a little tighter than I did.

Your post sounds kind of like you feel that those of us who truly pioneered the big advancements owe you something.

I've taught for years on the net, and it has been one of the least rewarding experiences of my career. (With some truly notable exceptions,) and I only stopped in to edit something and then I saw this...) I blame only myself, but if you want to know, man, then pick a scuderia you think you can handle, and sweep floors, whatever you can do to learn about it.

Just remember, there's maybe five guys in the world that can 'fresh sheet of paper' design a capsule, let alone a twin that kicks ass and isn't just a rehash.

So be careful who you choose for a mentor.

[theom]

Dear Mr. SP


I really hope that reply wasn't aimed at me.
I have tons of respect for you. My question was lunk headed and (I thought) I was up front about it. I was fishing for some good links on capsule design and manufacture. And maybe a few tips on experimenting with my old and or cheap mics.

After a bit more research I found that indeed there are jigs needed and that the screws on most capsules are for holding tension, not for adjustment there of.
While I have no practical experience with modification or manufacture of capsules, I do think I have a pretty good handle on the physics and mathematics of capsule theory.

I am sorry if I offend you in anyway. And also if I was the catalyst for any other posts here that did the same.

With sincere respect,

Theo Mack (theom)

[Stephen Paul]

Actually, before I really am outta here for a while (and with absolutely no hard feelings, believe it or not), I state categorically the following:

1) As the old license plate frame I had on my Plymouth Sport Fury 383 said, "Don't Follow Me, I'm Lost."

2) I believe I did something that borders on pure sorcery as a manuever of the reliquishing of my self-importance by coming right out and saying that I'm perfectly aware that I can be a total asshole sometimes.

That doesn't mean I want to be, and don't care and that I'm not trying to do something about that, because at 52, I think I could stand to finally let go of it all and just say, "Hey, screw it man, they got your techno, but you gave it to 'em, what're you complaining about?"

And the truth?

(Here it comes Lurkers and gennleman, he's gonna say it, but only once, this once:)

Because if you'd been jamming with Bela Fleck and David Lindley and The Hedgeman, (Michael Hedges), and had just done a prime-time ten minute piece playing and singing on Fox, and got the director to insist that Fox allow me to keep my copyrights and publishing, and lease the piece to them, (for those of you not pro songwriters fortunate enough to have gotten something big under your belt a couple of time,) in my case, BMI paid me by the second (with a bonus because it was prime-time, though Fox is syndicated so the rates are a hair /sec. less than the Networks prime-time royalties, Fox usually owns IT ALL.) Yup. Including 100% of your copyright man! That makes Motown look like pikers. Amateur pickpockets. Can I say that? And then to have it all suddenly yanked outta your hands, how would you feel?

Anyway I'm still livin' off the checks from that one, not even counting the AFTRA just for the appearance... and we were about to do two very hot NY shows in a few weeks, and everyone was primed and ready to go like a bullet.

But then I had to stop to do a couple of weeks of interviews, (up till then I'd been playin' eight hours a day, on my primary acoustics,) Two Martin sixes, a D45 1982, so it had the rosewood bridge plate and the unscalloped 1/4" bracing, and my main squeeze, a '68 D35 Brazilian, with custom inlay, maple bridgeplate, extremely thinnnnnn quarter sawn sides, a narrow neck, the 3/8ths triple aught bracing, though unscalloped, and on my twelve, (Big Guild DeLuxe), Fiddleback Maple natural finish, no bracing in the back.

All the acoustics had saddles I cut by hand out of bone, and then hand intonated over about six months of playing live. I changed my strings after every show, and used the last intonation to help me zero in the saddle radii with a small file... until the octaves were perfect and I could modulate keys by whipping my hand down and bopping my Kaiser up a fret!

You get the idea. My electric collection, pretty much same kinda thing. Duco blue '54 strat, '65 Sunburst Jaguar, Sunburst Precision, and Strat 12, with Duncan Hotstax and custom preamp built into the guard. There were many others, including my Padulla six-string fretless with Bartolini active pickups that I used to shove into a Pultec and into a 2A then right into my analog 24.

But I digress. The point is, this and airbrush painting was really what my life was all about.

One week before the TV shows that were booked, three of my knuckles went South.

Arthritis. Stuck. Bowels no move. You know?

Usually we would just directly inject 0.5ccs of Kennalog Cortisone right inta the knuckle. Ouch!!!! Baby did that HURT!

Most we usually did in a sitting was two, okay? 'Cos I may have a high pain tolerance, but Superman I am not. I ain't even from Havana!

But that afternoon was so important I looked at my doc and I said "Alan, go for it. Let's hit all three, because I cannot miss these bookings.

He shot all three.

I'll leave the gentle reader to imagine that that afternoon left no doubt in my mind that if anybody suffered for their art, they had nuthin' on me. Whew.

But.

Four days later.

I call my doc. "Alan."

"Yes?"

"Uh, nothing happened, I still can't play these particular tunes... and my hands really hurt. We have to do something..."

We did.

The bookings were cancelled.

I was told by my hand surgeon that I would not play guitar ever again, the in any way remotely resembling what my doctor had played him.

My doc likes my records.



Point is, my place which was a beehive of rehearsals every day, support personnel scheduling stuff, some of the greatest musicians in the world coming by and plaing real good for free 'cos they loved the music and believed in it, and in me.

And suddenly I lived in a tomb.

Mikes were never the central focus of my life except for the first years while I learned what was in the back, and how to actually be able to get up in the morning, look myself in the eye, and know that I could say, "Yeah. I got it." I understand as much as anyone who did, or could understand, about how these little bastards worked. And then could say that they weren't just messed around with, they were truly re-engineered.

And what I went through finding the info and deducing the rest.

BUT IT WASN'T MY LIFE.

I could AFFORD to give it away.

I would have anyhow.

I'm a trouble maker. Always have been, always will be.

Good officer, but the gentleman part? Well, that could take some time and just the right lady.

And I still write music and perform live, using my knuckles and thumbs on a Yamaha Tyros, slightly modded...

And I'm blessed that I have just a few people around me who took the trouble to get to know me, and for some reason have not gone screaming off into the hills.

So there's the problem.

Kurt Vonnegut said that artists, were the canaries of society.

Like when miners used to take canary birds with them down into the mine shafts, because of there was any poison gas present, it would knock out the canaries before the people, so the canary was sprt of a poison gas early warning system.

And that artists are the canaries of society.

That they are the first to keel over in the face of impending doom to the social order of things.

So my need right now, after exposing myself for as long as I did at that Other Place, and I cannot express to you what my own longings are at this point, but that one of them, was to able to relax.

To know that it's done. The work is done. I don't have to prove anything to anyone anymore.

And that's where I want to be, and the internet disturbs my sense of peace about it.

I don't really care who's to blame, I've already said that I know what I can be like, but there's one thing you mustn't forget.

If you were going to walk up to Wyatt Earp, any of his brothers, or Doc Holliday, and even play a game of cards with them, I would say, do it with not only respect, but with a healthy sense of why they might be names that were known to you in the first place.

And act accordingly.

I don't mean to blow anyone's head off, honestly.

I'm agin' it.

But why bring up a subject that is bound to cause nothing but trouble, bad feeling, and competitiveness, in an atmosphere of zero science, at ALL.

Why?

Why BOTHER?

And publicly for something you happen to be representing?

Hey, I tell you what, G-d save me from ever doing it to someone else. I had to learn to behave myself when I wrote a lot for Mix and was a ghost contributing editor to EM.

And I think that while I feel any reaction on my part is stupid and does nothing but even acknowledge and dignify some story, and I freely admit that, I also know my limitatons, I know that this is the kind of stuff that for whatever reason makes me feel like acting unreasonably, and so I choose to remove myself from the arena and let it be argued amongst those of you who wish to indulge in such speculations, and I don't need to spend my time stressing over nonsense that I shouldn't even have to read, because my secretary knows better than to even hand me such a piece of mail.

Okay?

Think of me whatever you wish. I worked like a dog to get where I am and to know what I know and to just keep on going. And if I choose where I sleep, then I choose it.

[bjornson]

ZOOOIIINNNKKKS I ain't hangin around tracy korby no more.... It could be contagious

[Bernd G]

Dear Mr. Paul,
I do not think anyone on this forum meant any disrespect regarding your achievements. We have come a long way in forums such as this in terms of sharing knowledge that once was regarded as secrets of the trade. I also think that in the end everyone will agree that there is no "right" way in sound recording - which is part of the charm, and the reason why the field can still generate excitement in most of us. There is science and there is art - and sound recording technology epitomizes the fascinating symbiotic relationship between them. Having said that, in my humble experience the people that feel truly at ease with their trade are usually the ones most generous in sharing their experiences and findings. I am glad to find that you are part of this group of people.
Greetings




P.S.: thank you Gyraf for the link !

[gyraf]

..see what I mean..?

Jakob E.

[Stephen Paul]

The 12a is noisy because it has a cathode follower amp circuit around the tube, which while low-distortion, is also low output.

Nothing you can do unless you want to cut traces and redesign the amp as a plate follower, and use a higher primary Z xfrmr.

Not much you can do otherwise.

In addition do NOT use a 13CW4.

The first two numbers in a NuVistor number are the heater voltage.

The 12a uses a 3586 or whatever the hell it is, (I forget the exact number).

And if there's anyone here who can say that I didn't 'share my information freely' for years on the 'net, you're nuts!

This isn't about security. It's about what I've chosen after years of givin' it up to the whole world, only to watch them take the work, not credit the source and make a pile of bucks from it.

That didn't stop me either. I have no idea what the Korby remark meant, but you sure don't want to get me started on that guy.

I'm just tired. I also hate to see bogus info like this last tube information get passed around with pure guesswork and not an idea of how any of it really works, and some utter nonsense presented as facts.

If just once in a while someone whould say, 'Well, none of this is absolutely known to me...'

such as the type of tube used in the mike asked about, etc.

That draws a remark purely for the sake of some knowledge, so I'm still doing it I guess out of habit.

But please don't imply that I haven't shared info or don't understand that spirit.

I've shared too much, and I'm burnt. Maybe that's the problem.

But you never meant that to appy to me, did you?

Just happened to find its way onto this particular thread. And there is no implication whatsoever that I'm a non info sharer.

You guys crack me up.

[Stephen Paul]

There are things connected to more than one post in my reply.

Neither of them are anger.

The problem is it's hard for me to not correct something like the tube type, PLUS leaving out the fact that with the 7586 you need a different xfrmr.

No, it's not going to kill anyone.

But there's something I learned a looooong time ago from my own teachers in audio, some of whom were I'm lucky to say, were the people that really built the very foundations of the industry. And there's one thing these people taught me.

If you're going to publish in any way, anywhere, make sure you know what you're talking about and be sure of your info.

In other words I was taught to make sure that even if I wrote for the