Topic: Fitting a k87 capsule without the leads already attached (Read 6817 times)

africantigercow · « **on:** January 17, 2011, 03:08:06 pm »

Hello everybody.

Sorry if this question is something that has been covered but I could not find an answer with several searches...

i recently acquired a second hand k87 capsule to replace the bad one in an old u87i that I own.

One thing that I missed when buying it was that there are no leads already attached to the centres of the capsule. It also appears to be lacking the plastic piece that sits on top of the capsule. (see attached picture)

luckily the mic still has all of it's leads still attached and also has the plastic top.

I was wondering if there is any special procedure to follow when replacing a capsule in this state?

Do I Unscrew the old cables from the centre of the old capsule, remove the old capsule from the mic, replace it with the new capsule (soldering any leads that were previously attached to the old capsule, to the new capsule) and then loosen the screws from the centres of the new capsule before placing the screw through the circular piece at the end of the lead and then back into the mic?

How much should one tighten the screw at the centre of the diaphragm? Does the tightness of the screw affect the sound?

What does the plastic above the capsule do?
(visible in this picture http://recordinghacks.com/images/mic_extras/neumann/neumann_ k870_capsule.jpg )
should I remove it from my old capsule and place it on the new one?

Is there any info I should pass on to my stable handed tech before beginning this procedure?

Also, What would you consider the condition of this capsule?
Does it look all original? Is it likely to perform to spec? (the capsule pictured in the attachment, not the link above)

Thank you very much for your time and help in advance... It is much appreciated, Sorry to put so many questions into one post. I am just very nervous about ruining a relatively expensive capsule..

Please let me know if there is any other information that you need.

thanks again,

Mike

Klaus Heyne · « **Reply #1 on:** January 17, 2011, 04:50:26 pm »

africantigercow wrote on Mon, 17 January 2011 12:08

Do I Unscrew the old cables from the centre of the old capsule, remove the old capsule from the mic, replace it with the new capsule (soldering any leads that were previously attached to the old capsule, to the new capsule) and then loosen the screws from the centres of the new capsule before placing the screw through the circular piece at the end of the lead and then back into the mic?

Proceed as you described. Remove the screws that hold the wire eyelets from the diaphragms before you dismantle the capsule from its mount, and re-attach the screws into the eyelets into the center of the diaphragms as the last procedure of the new installation.

Quote:

How much should one tighten the screw at the centre of the diaphragm? Does the tightness of the screw affect the sound?

Barely hand-tight. Make sure that you do not tighten it so much that the diaphragm starts to crease. When that happens, back up completely and start fresh.

Quote:

What does the plastic above the capsule do?

It protects the diaphragm ring from distorting/changing shape in case of whiplash of the capsule against the inside of the basket. First contact and primary impact in such case will be of the nylon collar against the basket, not the capsule's fragile diaphragm ring which needs to provide even diaphragm tension.

Quote:

Also, what would you consider the condition of this capsule?
Does it look all original? Is it likely to perform to spec?

The capsule looks original to me. No obvious damage visible. Its sonic qualities cannot be determined from a picture.

ssltech · « **Reply #2 on:** January 17, 2011, 05:36:39 pm »

Klaus,

Is there a 'spacer' behind the diaphragm which might make it important to NOT TILT the capsule during this process, for as long as the center-termination screw is removed?

Keith

africantigercow · « **Reply #3 on:** January 17, 2011, 06:05:09 pm »

Thank you very much for the info Klaus. That makes this procedure less stressful.

The back side of the capsule has a minor dent (see attached pic)

Does that look like something that might affect the sound at all?

Also, does this capsule look to be in need of a cleaning?

If these are questions that I should be paying someone to answer please let me know.

Thank you very very much for your help again. I can't believe what a valuable resource this is...

mike

Klaus Heyne · « **Reply #4 on:** January 17, 2011, 07:13:07 pm »

Yes, there is a center spacer between diaphragm and backplate, but it is almost impossible to dislodge it. (K870 as used in current generation U87 no longer have the spacer.)

Simple tilting of the capsule to the vertical will not dislodge the spacer; besides, the remote possibility of the spacer moving off its center is self-correcting: the capsule's center screw is impossible to mount with the capsule plane in the vertical position anyway.

In the rare case where the spacer may be dislodged from the center, coaxing it back to its original position by tapping the capsule is quite easy.

P.S.: the dent in the diaphragm is not nice. While it does not look like a hole (bad for the damping of diaphragm movement), its depth may interfere with the free movement of the diaphragm against the back plate, which is only 40

ssltech · « **Reply #5 on:** January 17, 2011, 08:48:57 pm »

Thanks for the clarification, Klaus.

Keith

africantigercow · « **Reply #6 on:** January 18, 2011, 02:49:33 am »

Quote:

P.S.: the dent in the diaphragm is not nice. While it does not look like a hole (bad for the damping of diaphragm movement), its depth may interfere with the free movement of the diaphragm against the back plate, which is only 40

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ssltech

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Re: Fitting a k87 capsule without the leads already attached

« Reply #7 on: January 18, 2011, 08:31:54 am »

There's nothing that can be tested without hooking it up electrically to SOMETHING... -So I'd proffer that it might be a good idea to hook it up and have a listen.

Even if it's touching the backplate at rest, it still won't stop it from producing sound, it would just alter the free movement of the diaphragm to a greater or lesser extent... think of a tapping drum skin with a finger gently touching it in one spot as an analogy.

-It might be quite acceptable, and if you turn it so that it's the REAR diaphragm surface, it wouldn't have any significant effect in cardioid; just omni and fig-8.

I've certainly had a diaphragm which had a similar dent, which the owner was entirely happy with... and it was on the FRONT diaphragm. -Your mileage may indeed vary.

As for cleaning; I've seen worse capsules be perfectly fine, and it'd be impossible to judge merely by the picture.

You be the judge; -try it, and see.

Keith

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Re: Fitting a k87 capsule without the leads already attached

« Reply #8 on: January 18, 2011, 11:03:32 am »

If you're very lucky, that dent could be right over one of the holes in the backplate and be no trouble at all.

Or it might not.

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africantigercow

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Re: Fitting a k87 capsule without the leads already attached

« Reply #9 on: January 19, 2011, 02:15:30 am »

Thanks very much for your help everyone.

I guess the best thing to do is to slap it on my mic and see how it sounds...

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