What cable/wiring to use with electret condensor mic

[seagull369]

Would anyone happen to know what would be an acceptable (as in inexpensive) cable to use with an electret condensor microphone? I have 4 of these mics and would like to run separate cables to each of them at about 10ft long. That would make total length of cable I'd need to get at about 40ft. Only one mic will be powered at one time.

The mics will be used in an automobile, so there could be alternator/ignition interference concerns.

If it helps, the specs on the mic I'm using can be found here.

Many thank yous in advance

 

[davenn]

Hi there
Welcome to EP

dual core screened audio lead would be a good start

 

[seagull369]

Hi there
Welcome to EP

Thanks for replying. Good to be here

Might that cable go by another name? I wasn't able to find much specifically when searching the moniker you gave..

 

[KrisBlueNZ]

Stereo or twin, screened or shielded, audio cable. It has two separately insulated cores inside a woven wire screen.

Have some links.

http://www.digikey.com/product-sear...cts=0&ColumnSort=1000011&stock=1&pageSize=250 - anything here will probably work but you may find something more suitable on a specialist cable supplier's web site.

http://www.thecableco.com/Catalog/DIY-Cables - not much information in this summary list though.

The big problem with searching for cables is that you'll mostly find pre-made cables with connectors already installed on both ends. You need to search for bulk audio cable to find just the actual cable itself.

Avoid sites that use vague words to tell you how amazing their cables sound. They are directed to audiophiles (aka audiophools) who are prepared to spend vast sums of money on ultra-pure special cables that have never been demonstrated to sound any better than normal cheaper cables. They are a waste of money.

SOME of the cables on these pages may be suitable:

http://www.parts-express.com/cat/microphone-cable-signal-cable/1610

http://www.performanceaudio.com/browse/Bulk-Wire-Cable/4,130,141/
-- http://www.performanceaudio.com/item/west-penn-25291b/11132/ $0.13/foot
-- http://www.performanceaudio.com/item/mogami-w2697/5601/ $0.31/foot, looks good

http://www.markertek.com/category/Bulk-Audio-Cable

http://bswusa.com/SearchResults.aspx?q=&departmentId=501&departmentName=Microphone Cable (sold in 100 foot reels, probably)

http://info.sommercable.com/2__default/ (go to Bulk Cable / Audio / Microphone)

 

[seagull369]

I don't mind lopping off the connectors on pre-made cables if I have to. I found this cheap one on eBay. It has an XLR connector on it, which appears to often be used with the type of cable you described.

For the $10 asking price, I don't expect perfection but I'm not looking to get superb sound quality either, esp. from just an 85 cent mic.

What do you think?

One other question if you don't mind: Does the shielding need to be wire woven (braiding, I'm assuming) or can it be something else and still work decently?

 

[KrisBlueNZ]

Sure, try it. Cheap cables can be microphonic (i.e. they pick up vibrations and convert them into signals), they can have high capacitance (which will show up as a lack of high-frequency response), and they can use very thin copper and therefore break easily, and the shielding is not likely to be very thorough, so they may be susceptible to interference. But it's probably worth a try.

It might also help us advise you if we had some idea of what you were using the microphones for! You said it's an automotive application but that doesn't tell us much.

 

[seagull369]

It might also help us advise you if we had some idea of what you were using the microphones for!

Very good point! And thanks for the quick reply

I'm basically trying to make a quasi-homemade version of this tool. It basically helps you hone in on the location of a problem noise on your car that only occurs when it's moving.

What I did is I took a "personal listening device" similar to this one, disconnected the internal mic and ran the 2 wires out of the thing into a 4 position (2-pole) switch. Coming out of the switch on the other end were 4 separate cables (I originally used coax) going to 4 separate mics. Each mic was attached to its own alligator clamp. In operation, only one mic is energized at one time via the switch. Changing the switch position turns on a corresponding mic/clamp. I listen in with my little headphones, flick the channels and try to figure out where the noise is the loudest. If I'm lucky enough to keep track of which clamp went to which switch setting, I will have found the (approximate) spot where the noise is.

The wires coming out of the Listen Up only travel a few inches to the switch, so I'm happy to leave them as they are. The wires coming out of the switch (going off to their respective mic) are a different story since they're the the ones traveling the 10ft.

Hope that makes some sense

 

[seagull369]

Should the shielding be wire woven (braiding, I'm assuming) or would another type work as well?

 

[Bluejets]

I would think fully braided should be more efficient at keeping out noise rather than a standard "laid -up" shield.

Really one of those applications you could try the latter if nothing else available but automotive apps have a lot of stray noise so the former probably recommended.
Cost difference would be next to nothing.

 

[KrisBlueNZ]

I don't know whether foil screening would be more or less effective than braiding. But definitely avoid the simple helical type of screening used with cheap cables.

I suspect you'll have problems with electrical interference if you use the microphones near the engine. And not just in the cables; the microphones will pick up noise internally because they're electromagnetic.

Possibly MEMS microphones (see http://www.digikey.com/product-sear...000b,fff80048&stock=1&quantity=1&pageSize=250) would be better, with battery power and radio communication to a central point. Or you could try a stethoscope approach instead.

 

[Bluejets]

Built a stethoscope style of engine noise detector years ago...had an extended metal rod connected to the pickup......not sure if it used magnetic or crystal style earpiece as a pickup.
Perhaps the former, but didn't suffer any noise problems.

Then again, it was the noise i was looking for...........

 

[seagull369]

Braiding it is....

I forgot to ask, Would the metal braiding get soldered to either of the mic terminals or no?

 

[KrisBlueNZ]

Solder the braid to 0V at the circuit board (along with one of the inner conductors) but don't connect it at the microphone end.