Stupidly, I destroyed two Schoeps MK4 capsules recently by storing them for only a weekend in a home made foam enclosure. I glued pieces of Pelican case foam together with Weldbond PVA glue. This reacted with the foam to bathe the mics in acetic acid vapour.

I noticed the vapour on the Monday after and thought it couldn't be good for the mics. Using them, I noticed a significant loss of output (6-10dB over a few weeks). Sent them back to Schoeps, unrepairable and destroyed.

Lesson learned. Store and transport mics in the most inert enclosures possible.

Oooof. I'm so sorry about that. Thanks for sharing, David.

yow....bummer.

That's really strange since PVA glue is water-based, one would think it's rather 'inert'.

Sad to hear of your experience David. Timely, as I was about to make some mic storage boxes akin to cigar boxes, gluing lining cloth to formers with PVA - assuming the latter was benign. Indeed, it might be in that use (i.e. not gluing polyurethane foam), but I'll be checking first.
Was the glue still curing in your case?
Cheers,
Roland

Good point; waiting until fully dry may make all the difference.

Did you assume acetic acid based on vinegar-y smell, or was that verified by Schoeps?

Is it true that Ribbon mics must be stored "upright". ?
To prevent the ribbon elements from sagging, if they are stored sideways ?

Yes that was my thinking too. As others have noted, probably not fully cured.

No it was abundantly clear it was acetic acid smell. Some silcones emit this too while they are curing.

I am wondering now about other foams in my mic cases (Peli) and any long term effects of the slowly degrading foam. I store the mics in ziplock bags while in these cases to minimise any corrosion.

Klaus Heyne recommends storing mics in plastic bags to protect from degrading foam but keeping the bags not sealed to avoid condensation issues.

For US customers: I store my pencil mics in these PVC shipping tubes, which are similar to the Schoeps tubes but far cheaper and come in a wide variety of sizes. I haven't ever tried the polypropylene versions; they are a more recent offering.
https://www.mcmaster.com/shipping-tu...hipping-tubes/

0.79" diameter works for mics up to 20mm; 0.87" if you have Neumann. My DPA 4000 mics perfectly fit in this one:
https://www.mcmaster.com/2108T22/

The tubes then go into cutouts in my Pelican case. I also use Kaizen foam cut with a scalpel instead of the normal pluck cube stuff, as it doesn't break down and turn to dust.

Correct.

Royer states no such caution in their manuals. Nor does Shure.

Might be true of some vintage mics and/or those with very long ribbons, and sketchy corrugations.

Yes, and I also think it’s good practice, and it makes sense.

If a ribbon were to stretch in response to gravity, wouldn’t that occur no matter which orientation it were stored in ?

Using a spring analogy, the difference would be that with horizontal storage the ‘stretch’ would be either distributed equally across the length, or perhaps more evident at the 2 attachment end zones ….while with vertical storage, the stretch would occur primarily at the uppermost attachment point alone, as the weight bearing end of the ribbon ?

I’d expect a longer and thicker ribbon to stretch more than a thinner, shorter one.

I believe there are some manufacturers who create longitudinal corrugations (ie parallel to the ribbon’s length) at the ends, with transverse corrugations along the majority of the ribbon, to offset this ‘end stretch’ tendency

In fact, I’d be more interested in the oxidation of the aluminium foil surface over time….and the galvanic effect of dissimilar metals in contact at the attachment points. Since it’s never mentioned, it can’t be a problem…right ?

This is Hugh Robjohns’ opinion on the matter:

So perhaps the obsessive-compulsive extension to that practice could be to simply invert the vertical storage boxes every few weeks….to give each attachment end a regular turn at being uppermost !

I'm certain you are pulling legs (they are susceptible to stretch you know) but no.

What Hugh is saying is that it is simply a good practice to store ribbons vertically. Not even common practice. Not even vintage practice. Just good engineering practice.

I agree, but don't tell anyone. I always stored my Royers and Samars on their sides.

Then again, I have no ribbons any more nor use for them.

D.

Just got my perfect-fit tubes for my DPA 4015s from McMaster-Carr today. Thanks for the great source! They beat the Shure pouches I was using in SO many ways.

Just ordered tubes for my KM100 series as well.

D.

It depends on the individual mic. I own a Samar AL95. The Samar website says this about it:

“At the heart of the microphone is a ‘piston’ corrugated ribbon. Compared to the regular ‘zig-zag’ corrugation, it offers lower noise, deeper, fuller, and more controlled bass response, higher output, lower resonance modes, and very high SPL handling. All those advantages are due to the ribbon motion, which is similar to that of speaker cones. A very important feature of the ribbon is its robust construction and therefore, much lower fragility than conventional ribbon microphones. Due to this, they do not require any special precautions for storage.”

I believe the Samar ‘piston’ ribbon mimics a similar approach used in the older B&O ribbon models from the 1960’s ….does anyone have the knowledge to describe the difference between these and the conventional ribbon designs ?

Edit: the UK ribbon mic maker Extinct Audio, as well as Beyer, have also used pistonic ribbons, it’s described in the sidebar (“Piston Engines”) paragraph here: https://www.extinctaudio.co.uk/wp-co...ExtinctBM9.pdf

Glad they are working well for you. I don't remember if someone recommended them to me or I found them myself. I remember looking for a cheaper alternative to the Schoeps-branded tubes, and I think the McMaster ones are just as good.

Sorry this happened!!! But, thanks for sharing this intel!

It’s a sobering reminder of one of the fragilities of (non-ribbon) mics. You’d be hard pressed to damage a condensor mic with the SPL from most instruments, but it’s agents such as condensing water vapour and solvents like David encountered which present the greatest malfunction risk.

In his case, an alternative approach might be the use of double sided adhesive tape, or even a sewing needle and cotton thread, to join or attach pieces of foam together inside an enclosure ?

This was for my MSTC7 as I didn't want to pack the wooden Schoeps case each time. But now I am transporting it in the original case. Too bad if it gets knocked about.

That’s my thinking also, when I pack my sE ribbon mics original (bulky) wooden boxes for concert duty.

Occasionally it’s worked out that I’ve been able to remove the sculpted foam insert from an original box and place it in a new (same-sized) travel case, but usually there’s a case-size disparity which prevents that.

So sorry to hear, David.

I encourage everyone to check their polyurethane foam in all packing regularly for signs of degrading, it's wildly variable. The stiffer polyethylene foam does not seem to degrade. The current dual Neumann KM18x boxes appear to use the stiff foam. Maybe time to go back to velvet over wood.

I like polyethylene bags for protection, but might consider some dessicant packs, too. I use thick poly freezer bags on things like a wooden mic boxes before tossing into a Pelican, but don't seal airtight. I was thinking some little laptop sleeves or packing cubes might work for some items.

That's one of the things I find attractive about the tubes that Voltronic recommended. No need for any foam since the tubes lock down tight on each end of the mics. No rattle. I think that if I needed extra protection, I'd just throw the tubes in a Shure pouch.

From years of my mics riding around in a sound-cart drawer in tubes in the back of a camera truck, I found that they were pretty darned impervious to damage. Yeah, dropping a Schoeps on a concrete floor was a problem. Having one hit by a swinging broadsword was a problem (true story). Living in a PCV tube? All good. Keeps out the dirt, provides shelter. That's it and it's fine.

My Schoeps tend to live in their "Schoeps" wooden boxes, and have for a while. My DPA "sets" with clips, pop screens, grids, etc. tend to live in their "DPA" boxes. My 4015s came in a, for a pair of pencil mics, giant Pelican case. No need for that. Two Voltronic tubes and a Shure pouch and Bob was my uncle. Two KM100s in a large wooden box? Nope. Two Voltronics tubes and a Shure pouch. Yeah!

Anyway . . . .

D.