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Old March 29th, 2013, 10:05 AM   #1
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XLR cable length question?

Hi Everyone.

A few questions about XLR cables.

1) what is the maximum length cable you would/could run from a field mixer to mic? I probably wouldn't need to run any more than 25-50 feet.

2) same rule of thumb apply to both phantom powered and battery powered mics?

3) Is it ok practice to plug two or more cables together to get greater length?

4) At what point (length) might there be latency issues if any?

Thanks for your help.

Jonathan
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Old March 29th, 2013, 10:12 AM   #2
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Re: XLR cable length question?

1. A balanced audio run will have no issue running 50'. The only issues would be if there is RF contamination. (For example, if there are lighting dimmer packs or other contamination sources)

2. 50' is fine for phantom power. I run 100' frequently with no issues.

3. A longer run is always better than joining 2 cables, all things considered due to the POSSIBILITY of RF or poor contacts but it is done all the time. Better connectors equals better signal transmission. I like Neutrik, some prefer Switchcraft but any good name brand connector will suffice. I prefer to keep all my connectors the same brand.

4. Latency isn't an issue on cables within any reasonable run. In fact, audio will run significantly faster on cable than through air. In live events, I often hear the board feed on my headphones BEFORE I hear the in-room audio.
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Old March 29th, 2013, 10:12 AM   #3
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Re: XLR cable length question?

Quote:
Originally Posted by Jonathan Levin;17873341)
What is the maximum length cable you would/could run from a field mixer to mic? I probably wouldn't need to run any more than 25-50 feet.
That's nothing. I wouldn't give it a second thought until I reached around 250-500 feet. Of course, this assumes conventional professional microphones and decent cables.

Quote:
2) same rule of thumb apply to both phantom powered and battery powered mics?
Yes

Quote:
3) Is it ok practice to plug two or more cables together to get greater length?
Perfectly OK. Again, assuming decent connectors and cable.

Quote:
4) At what point (length) might there be latency issues if any?
You will run out of cable before latency becomes an issue.
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Old March 29th, 2013, 10:48 AM   #4
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Re: XLR cable length question?

Shaun and Richard, thanks so much for that.

You will both be proud of me as I am going to try to learn to solder and make a few of my own cables.

I have a friend who is a real electronics geek and has the right soldering iron and can show me how to do this. This should help offset the staggering cost of these cables.

I have one of those soldering irons that looks like a gun. Not the right thing.

Do you guys have a good how to for proper cable making I can refer back to?

Have a great weekend.

Jonathan
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Old March 29th, 2013, 11:50 AM   #5
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Re: XLR cable length question?

Quote:
Originally Posted by Jonathan Levin View Post
You will both be proud of me as I am going to try to learn to solder and make a few of my own cables.

I have a friend who is a real electronics geek and has the right soldering iron and can show me how to do this. This should help offset the staggering cost of these cables.
Good for you. Raw cable and connectors aren't that expensive. I get nearly all my stuff from Redco. I don't believe in "botique" expensive "name-brand" cables. If you know how to solder, you can save a LOT of money making your own cables, and it comes in handy for repairing or even building your own gear.

Quote:
I have one of those soldering irons that looks like a gun. Not the right thing.
It would do in a pinch, but even an inexpensive small soldering iron would work fine.

Quote:
Do you guys have a good how to for proper cable making I can refer back to?
There are some video tutorials on YouTube like these...


Neither of them are perfect, IMHO, but they each make some useful points.

Recommend getting some old discarded electronics gadgets and practice soldering where you can't hurt anything.
Once you are comfortable with soldering, terminating XLR connectors is one of the easier soldering tasks.
REMEMBER to put the shell over the wire before stripping! If you forget, you have to take everything back apart and do it over. :-(
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Old March 29th, 2013, 12:55 PM   #6
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Re: XLR cable length question?

Also keep your fingers off the hot tip of the iron. Trust me! ;-)
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Old March 29th, 2013, 02:50 PM   #7
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Re: XLR cable length question?

Don,

My wife reminds of that every day ;-}

Richard thanks again.

Jonathan
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Old March 29th, 2013, 03:20 PM   #8
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Re: XLR cable length question?

Ok. One other question. Should I be looking at getting Quad microphone cable which has four conductors or do I just need standard three conductor?

I also noticed that connectors come in 3 and 4 pin. Which do you recommend? I'm guessing with the four pin I'd use the quad cable. Just want to make sure.

I did notice when I took apart one of my cables that in addition to the terminals 1, 2, and 3, there looked like there was a larger blade-like terminal. Extra ground?

And just to confirm:

Pin 1 = ground
Pin 2 = Hot
Pin 3 =Cold

Guess it doesn't matter as long as they match up at the other end of the cable.

JL
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Old March 29th, 2013, 03:55 PM   #9
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Re: XLR cable length question?

Blimey. I must have made thousands of solder joint over the years. My tips would be to constantly clean the iron tip with a damp sponge, and to get a little tin of flux. Even if using cored solder, the flux works like a magic trick. Use just enough flux, and then the solder will flow where there is flux and enough heat. I wouldn't 'tin' the plug because it is already going to have an easy flow surface. So tin the cable, put a tiny dab of flux in the plug connection, insert the tinned cable, and use the iron.

Try and find some rubber cable sleeves to slip over the cable _before_ you make the joint, and then slide down over the connection. You'll need some slippery to put the sleeve on the cable, but a dab of washing up liquid will do. Let the joint cool down before sliding the sleeve down, or it might cause the still soft cable insulation to plough up in front of it.

Heat shrink sleeving is even better, and if you don't have a heat gun, you can use the solder iron if you are careful.

But after all that, a point I was going to make is that I've generally found it cheaper to buy premade cables.

quality xlr cables | eBay
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Old March 29th, 2013, 04:52 PM   #10
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Re: XLR cable length question?

Quote:
Originally Posted by Jonathan Levin View Post
Ok. One other question. Should I be looking at getting Quad microphone cable which has four conductors or do I just need standard three conductor?
Apparently in 50+ years of using XLR cables, I have been so lucky that I have never encountered a situation where a quad microphone cable made any difference.

I have some quad cables, but I use them for STEREO where I have the left and right microphone signals with just one cable.

Quote:
also noticed that connectors come in 3 and 4 pin. Which do you recommend? I'm guessing with the four pin I'd use the quad cable. Just want to make sure.
Practically every conventional monaural microphone made in the last several decades use 3-pin XLR. I don't know of ANY mainstream microphones that use 4 pin XLR. 4-pin XLR are used for special applications like 12V power and intercom headsets. Two applications that have NOTHING to do with regular microphones. Don't even think about 4-pin XLR connectors in connection with microphones.

Now there are STEREO microphones which have 5-pin XLR connectors (two balanced pins for Left and two balanced pins for Right, plus ground pin). That is how I have my quad cables wired so I can use my several stereo mics (or two regular mics with a special "Y-cable").

Quote:
I did notice when I took apart one of my cables that in addition to the terminals 1, 2, and 3, there looked like there was a larger blade-like terminal. Extra ground?
If you look carefully, you will see that it is probably the termination to the connector shell. The general convention is to leave the shell floating (NOT connected to ground). There are some special cases where you may need a capacitor between pin 1/shield and the connector shell (like high-RF environments), or maybe even a hard connection, but that is rare and I wouldn't do it as a rule.

Quote:
And just to confirm:
Pin 1 = ground
Pin 2 = Hot
Pin 3 =Cold
That is correct.

Quote:
Guess it doesn't matter as long as they match up at the other end of the cable.
True. But it is handy to have your own "rule" so you can remember and get the two ends wired properly when you can't see the other end. For example, I use the colored (or brightest color) wire as "Hot" (pin 2) and the neutral (white or black) or darker color for "cold" (pin 3). Of course, the outside braid/wrap is always ground/shield/pin 1.
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Old March 29th, 2013, 07:38 PM   #11
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Re: XLR cable length question?

See this Rane technical note - highly recommended!

There's a tremendous amount of reference info there, but do be aware that some of it pertains to how to wire chassis connectors, which most of us never need to do. The second cable in Figure 1a is how to wire a typical XLR cable. Figure 1b can be confusing - it refers to chassis connector wiring.
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Old March 29th, 2013, 11:17 PM   #12
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Re: XLR cable length question?

Quote:
Originally Posted by Richard Crowley View Post
You will run out of cable before latency becomes an issue.
That's an understatement...

I took some readings with a time domain reflectometer. Wire has an electrical property known as Velocity of Propagation, or Vp for short. It's how fast the electons move through it and is referenced to the speed of light. A Vp of 1.00 would be the speed of light. My XLR cable came in at 0.52 (155,892,078.16 meters/sec).

If I shot a scene using on-camera mic and the sound source was 10 meters away, there would be a latency of 0.029 seconds caused by the relatively slow speed of sound through the air.

To attain that same amount of latency using a wired mic at the source, you would need to hook up 4,600,000 meters of cable, give or take.

Okay, putting away the calculater now.
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Old March 30th, 2013, 06:19 AM   #13
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Re: XLR cable length question?

The first mic I bought came from a guy who made up his own cables. I wished I could remember the details but he was very particular about his cables and essentially demanded the best he could put together. Unfortunately, I don't remember the cable brand/type or the connector type but one thing I remember is they weren't cheap.

Nothing to do with soldering, but with the care and use of cables.

Back in the day when I worked in construction we were told never to walk on the cables and these were really heavy-duty cables, say 3/4-inch or 2 cm in diameter that supplied power to tools like table saws, radial-arm saws, skill saws, and the like. The XLR cables are really light-weight by comparison, with the shielding and really small conductors inside.

The rule to myself is to never walk on my cables. I string them in out-of-the-way places and where that is not possible, like going from tripod or mic boom to a row of chairs for example, I just have to remember not to not walk on it. If there are other people this presents a challenge.

Question: How do others handle XLR cable protection, for example, walking on them? Or if you even try?

Besides just using it, how can one test a cable, like with an electronic test instrument? Or is this even necessary?
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Old March 30th, 2013, 09:14 AM   #14
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Re: XLR cable length question?

IME, decent cables do not need coddling. Of course, you wouldn't want to have vehicle traffic driving over them on a regular basis. I have been making my own cables (audio, video, RF, etc. etc.) for over 50 years. I started out using Belden cable and Switchcraft connectors and still prefer those. There is a tradeoff between
pliability vs. ruggedness. I have some very "limp" Canare cable that lays flat very nicely, but I fear that it isn't as rugged as the old-school Belden, et.al. I still have a few XLR mic cables that I made back in the 1960s. I tend to loose them (or maybe they are stolen?) before they "wear out".

There are rather inexpensive cable testers available for XLR, TRS, RCA, BNC, Speakon, etc. If you have long runs of cable used for digital signals (like AES/EBU, etc.) then techniques like TDR (Tme-Domain Reflectometry) are used to locate cable faults. But that typically isn't necessary for ordinary baseband audio signals.

As far as walking over cables, etc, my biggest fear is that someone will trip over them and hurt themselves (or pull a mic stand over, etc.) So anywhere cables cross a public walking area, they get taped down to the floor with gaffer's tape. If I have more and/or larger cables, I use something to cover them. I have several rolls of "runner carpet" which are useful for covering cables, etc. And those rubber extruded things that you can run cable through (although I cut off the bottom so I can just lay them over the cable already in place). And for larger bundles/cables, there are special plastic devices that are made for cable crossings, including those rugged enough for vehicular traffic, etc.
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Old March 31st, 2013, 07:31 AM   #15
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Re: XLR cable length question?

Walking on is not the cable killer - any half-decent cable copes with walking. Foot fall from a flat shoes is negligible. A high heel stiletto is quite capable of slicing through the insulation if the heel edge is sharp, and leaving a sizeable dent if place dead centre. The crush of damage is often not a big deal if it's small and the cable outer intact. Rolling between the thumb and first finger often restores 'circularity'. Last night I was working on an Osmonds show, and some of the loudspeakers were on four castor trucks - and tipping the scales at over 200Kg - nearly half a ton - meant that the sound people routinely accelerated them over cables - often with care if the cables were sound cables, but in a more er, cavalier manner when the cables were video or lighting. That means a fast moving heavy weight hitting a mic cable, and giving it some fairly severe treatment.

Nobody cares, eventually when a cable has been mistreated this way for a few times in the same location, it may fail. If it does, the chances are it will be binned, or maybe, if it's a very long one, shortened and repaired. Most, however, end up being scrapped as uneconomic to repair.

Few of the cables being used in less stressful circumstances get this treatment. Pro audio simply buy decent cable - usually decent meaning tough, not stupid claims over audio quality differences. Decent cable doesn't mean ultra expensive, just not rubbish!
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