Sticking XLR's

[cedd]

Never seen this one before!

So today I turned up to a choir gig that I loan kit to every year. It was the last one and I was there to collect my stuff. Their engineer was looking very frazzled and reported that none of the XLR cables were fitting in the mics. I assumed he'd damaged the socket on one mic and nothing was fitting in to it. I was wrong, literally none of the female XLR's would plug in to the mics! I tried several mics and several cables. In the end we found the least bad cables (even if they were way too short) and forced them in (half an hour to start - no other option really!) though not far enough for the catch to engage (physically wouldn't go!) then connected them to the proper length cables. Cable to cable was fine.

 

Has anyone seen this before? I'm assuming either the mics or cable XLR's got hot and expanded. It's the only explanation I can come up with as to why every cable would stop fitting every mic. None of the cables felt warm, and we were using several makes and styles of XLR plugs.

If you have seen this before, what on earth can you do apart from not get them hot to start with (not my gig, so no control or idea on storage in this instance). Do you think they'll recover? I've not had chance to unload the van and check them yet.

 

All very odd! They must have got very hot if it is a heat issue!

[whisky-zulu]

I've had XLRs that have been a pain to get into the end of mics and desk outputs, but nothing on the scale you've described, and it's normally the non Neutrik connectors that I've found are those most susceptable to not fitting properly. As you say, they must have got very hot for them to have not fitted - is there anything in the rig that could have caused that? Then again, a usual gig rig shouldn't cause XLRs to become excessively warm to begin with. Is this the first time that someone has reported that particular issue to you? Other than that, I can't really offfer much help.

[KidRay]

If I remember my schoolboy physics correctly (the ball that doesn't fit through the ring until heat is applied, the ring expands relative to the ball etc.), I suppose it's possible if the cables were somewhere a lot warmer than the mics, and it was warm today.

If they fit okay when you get a chance to test them, then a heat differential between mics and cables is a likely candidate, but not one I've come across before.

[Brian]

Odd...

 

1) if the mics and XLRs were at the same temperature then they would have both expanded by similar amounts

 

2) if just the XLRs were hot then they'll have expanded by just 0.0013% for every degree temperature rise, assuming the outer is made from steel

[cedd]

Indeed, all of the above went through my mind. If the mics and XLR's had been in the same place in the same temperatures, surely they should have expanded together, and I know the numbers we're talking about are incredibly small. Makes it all the more unusual.

 

The expansion coefficients of plastics are considerably higher than that of metals, so I wondered if the plastic inners of the XLR's were the bits that had expanded?

 

Apparently all the equipment was stored in the church overnight and through the day in a room with large bay windows. As it was a sunday, I also guess it's a room that wasn't needed for other stuff (otherwise they wouldn't have let them store the kit there) and therefore wasn't opened until the kit was required. There's a possibility therefore that the XLR box (a plastic crate) was in direct sunlight for a prolonged time, but the box with mics wasn't. All guesswork of course!

 

I'm still not 100% convinced it was heat, but I can't think of anything else at all that it could be, and I know what I saw (and felt).

[mervaka]

I'm more inclined to believe the cause was a gaping wide tolerance at QC during manufacturing. Dare I ask what brand? The cannon style XLR shells Thomann use on their cheap cables I've had similar problems with.

[S&L]

IF this was expansion..and that's a big IF, then logically the mics and cables were not stored together - the cable ends would have to be the ones doing the expanding so as not to fit inside the mic. this would mean that the cable ends were an alloy and were kept in a black box absorbing heat in a warm place...car seat in direct sunlight all day etc.

of course this could be a poorly controlled manufacturering tolerance if this was first time use. I haven't seen it with sound gear yet but with electrical gear there are plenty of chinese fakes on the market that don't do the job but are made to look the part - along with those that are made as none brand name items and don't have a decent manufacturing standard. there is nothing wrong with chinese manufacturing as such - just that their factories are turning out lots and in some cases some factories are deliberately knocking out poor gear to decieve end buyers, aided smd emcouraged by unscrupulous western importers - circuit breakers that have no breaker inside but look the same as european circuit breakers complete with BS or other standard stamps - of course they aren't really compliant with those standards but you get the point!

The good news is that IF it was weather related you have the ideal opportunity to conduct a repeat experiment. leave a cable in a black box inside your hot car all day - or whatever the conditions were.

 

this is one of those weird things that has me curious now. would love to have an update if you find anything.

[cedd]

This sounds like a chance to carry out an experiment!

Hopefully tomorrow will be sunny and I'll get chance to play. I'll document my findings!

[timtheenchanteruk]

is it time to call...

 

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