A basic Ribbon Mic problem

[blunderfonics]

I recently picked up a pair of Chinese Ribbon mics via a group buy over at the Tape Op Message Board. When I started using them as a close pair it became apparent that the output of one was inverted from the other. I was able to determine which mic had the problem easily enough by comparing them to other mics. Quality control on budget mics being what it is, I initially assumed it was just a bad wiring job but when I disassembled them to correct the problem both were wired identically. I checked everything I could see without fully dissasembling the mic down to the last screw but didn't notice anything obviously out of place. So at this point I'm thinking that either:

a) The motor was physically inverted (either back to front or end to end) before getting wired.

b) The polarity of the magnets were not oriented correctly during manufaturing of the motor.

or

c) The polarity is getting flipped inside the transformer.

Do any of these theory's make sense? If there are any ribbon experts out there who might know the best way to test for proper assembly, I'd love to gain some insight before I take the mics apart again.

Thanks

 

[clintrubber]

[quote author="blunderfonics"]I recently picked up a pair of Chinese Ribbon mics via a group buy over at the Tape Op Message Board. When I started using them as a close pair it became apparent that the output of one was inverted from the other. I was able to determine which mic had the problem easily enough by comparing them to other mics. Quality control on budget mics being what it is, I initially assumed it was just a bad wiring job but when I disassembled them to correct the problem both were wired identically. I checked everything I could see without fully dissasembling the mic down to the last screw but didn't notice anything obviously out of place. So at this point I'm thinking that either:

a) The motor was physically inverted (either back to front or end to end) before getting wired.

b) The polarity of the magnets were not oriented correctly during manufaturing of the motor.

or

c) The polarity is getting flipped inside the transformer.

Do any of these theory's make sense? If there are any ribbon experts out there who might know the best way to test for proper assembly, I'd love to gain some insight before I take the mics apart again.

Thanks[/quote]

The obvious suggestion of course is just to swap the two signal wires in the XLR-plug and be done with it (if eventual EQ-differences are allowed),
but you'll likely have considered that already and you just want to know what's going on, right ?

 

[blunderfonics]

I have done that for now in order to make them usable as a pair without having to remember which one needs it's polarity reversed. I'm just wondering how 2 mics that appear to be electrically identical wound up out of phase. If there is a feasable mechanical or magnetic explanation for the problem I would like to fix it from that end if possible.

 

[rodabod]

Yes, A or B sounds most likely.

Just swap over the wires at pins 2 and 3.

Or, turn the ribbon motor around.

 

[rodabod]

[quote author="blunderfonics"] I'm just wondering how 2 mics that appear to be electrically identical wound up out of phase. If there is a feasable mechanical or magnetic explanation for the problem I would like to fix it from that end if possible.[/quote]

Is the motor symmetrical fro side to side?

If so, rotate it 180 degrees.

If not, turn the magnets round.

 

[pucho812]

the problem with most inexpensive mics is cheaps parts and no real QC(Quality control) flipping pins makes the mics work in proper polarity but there is still going to be an eq difference hell even if the mics were put together correctly it would still be an unmatched pair and need some eq tweeks. be happy you found a problem some people I happen to have as clients would not be able to tell the difference :shock:

 

[fum]

What pucho said =)

What you're looking for inside the mic is as follows:

The side of the ribbon motor that has the screws clamping the ribbon is the front(at least on my microphones), and should be facing the figure 8 symbol on the grill. Very easy to put it in backwards on the mic, which is what I often find.

The red wires coming off the top of the ribbon are the + side, blue wires -, red wires hook up to red on the primary of the transformer, blue to the white wire of the primary.

Green wire of the secondary hooks up to + (pin 2 of XLR) typically blue wire, black wire hooks up to - (pin 3 of XLR) typically white wire.

Hope this helps

ju