Lo and Hi Impedance Mics ????

[GlowPlug]

I know that this is a brain dead question. But, Can someone delicately explain the difference between a low and hi impedance microphone,

And does it matter what type of microphone cable I use, and where on the mixer I plug the mics into???

and can I use XLR ---> XLR microphone cables with either type of microphone?

 

[bennychico11]

HI-Z mics are designed to run with a cable length of less than 30 feet. Because of the mic and cable's construction, running any cable length more than 30' would result in a loss of high frequencies as well as signal strength being affected.
HI-Z cables are also more prone to interference. Again, because of their design, LOW-Z mics can allow you to run up to around 300 feet without affecting the tone, signal level, and are more resistant to noise & interference.

There IS a different cable for each mic. HI-Z uses 1/4" connectors on the end of their cables and LO-Z use XLR. A LO-Z mike will work with a HI-Z cable, not at it's best, but it will work. It usually means you'll have to turn up the gain at the mixer to make up for some of the signal loss due to the mismatch. The correct way to use a lo-z mic into a hi-z input (like a guitar amp or cassette deck, for example) would be to use a XLR cable and connect an inline impedance matching transformer. This normally looks like a cylinder with an female xlr connector on one end and a 1/4 inch male phone plug at the other. Inside the cylinder is a transformer that converts the lo-z mike's impedance and boosts it's lower output signal up, to more easily operate with the hi-z mic input.

However, you rarely see hi-z mics plugged into a lo-z mic input. The mismatch between the two is so severe, it usually results in a distorted sound. You can get a HI-Z cable to plug into a guitar cab or a mixer with a HI-Z input: http://www.musiciansfriend.com/srs7/search/detail/base_id/135405/src=00633

or get something like this if you want to plug into a LO-Z input:
http://www.musiciansfriend.com/srs7/g=home/search/detail/base_pid/422414/

A DI box might work just as well too.

 

[GlowPlug]

Ahhhhhhhhhhhhh,OK! Now its starting to make more sense. Thanks BennyC!

So, in theory I could use an XLR cable to plug in a Hi Impedance mic if I keep the length less than 30 feet, . . But, I would get better results if I use a proper 1/4" connector cable for a Hi-Z,

AND where what input on the mixing board would work best for a Hi-Z microphone with a 1/4" connector at the end? I have an XLR input, and a LINE input.

AND of course my last question is, How do you determine the impedance, or the difference between a LO-Z, and Hi-Z mic????? can you tell by the ohms that the mic is set for. I think this mic that I have is 500, or 600 ohms. Tanks!

 

[bennychico11]

Ahhhhhhhhhhhhh,OK! Now its starting to make more sense. Thanks BennyC!

So, in theory I could use an XLR cable to plug in a Hi Impedance mic if I keep the length less than 30 feet, . . But, I would get better results if I use a proper 1/4" connector cable for a Hi-Z,

AND where what input on the mixing board would work best for a Hi-Z microphone with a 1/4" connector at the end? I have an XLR input, and a LINE input.

AND of course my last question is, How do you determine the impedance, or the difference between a LO-Z, and Hi-Z mic????? can you tell by the ohms that the mic is set for. I think this mic that I have is 500, or 600 ohms. Tanks!

no, that's the thing...it's not the cable that is HI-Z, it's the microphone. No matter what cable you're using, it needs to plug into a HI-Z input. Think of the microphone like it's a guitar. For plugging a guitar in direct with a mixer you need to transform it to LO-Z (which is what a mic input on a mixer accepts). Unless your mixer specifcally says it accepts HI-Z mics (which I think I only a few live PA mixers do), then you need to get something like the products I linked to....or try a DI box if you have one lying around.

to find the impedance of a mic, it will generally say in the specs whether it's hi or lo. 500-600 is rather high. A typical microphone is around 50-150. And a typical rule to follow is to plug it into a microphone preamp that is 10 times the amount of input impedance. So if yours is 500...you'd have to plug it into a 5000 ohm input! A typical preamp is around 1500 ohms unless you get a variable impedance preamp.

 

[GlowPlug]

Oh Ok, I getcha.

Hmmmmm, I'm not sure about the LINE input on my mixer, whether its Hi-Z or not. The spec sheet says. (47 Kohms, 1/4" phono plug) whats a kohm???

 

[notCardio]

K Ohm, not Kohm

which is what happens when manuals get written by people who don't speak the language they're writing in. K ohms means 1000 ohms. K is the scientific abbreviation for thousand. 5K = 5,000 10K=10,000 etc. Ohms is a measure of resistance, or in this case, impedance. Rule of thumb is that if it's a 1/4" input jack, like you find on a guitar amp, it's hi-Z.

What kind of mic is it, and what kind of mixer? Brand and model, please, and I'll try to look it up.

 

[notCardio]

On the other hand

maybe I'm butting in when Benny's got it covered. Sorry Ben.

 

[bennychico11]

Rule of thumb is that if it's a 1/4" input jack, like you find on a guitar amp, it's hi-Z.

not necessarily true. You have to check the specs of the gear you are using. Some 1/4" inputs accept high impedance...others don't and will ruin your sound. The rule of thumb should be...the output signal (source) should have a lower impedance than input load (destination).

A typical guitar electromagnetic pickup is about 7,000 to 15,000 ohms. They are made to connect to a load of a megaohm or more!
Now, the 1/4" Line input on your average Mackie mixer is only 10,000 ohms. This is not enough for our guitar input. So we use a DI box to reduce the load down to around microphone level.

SOME inputs are HI-Z inputs...you just have to read your specs. Most devices will tell you whether they accept HI-Z or not via 1/4". A popular example is the Digi 002 which allows you to plug in via 1/4" but you have to choose whether it's a HI-Z input or a Line Level input.

 

[Dani Pace]

You guys hash over the tech stuff, in application high Z mics tend to work better for room ambience or overheads, low Z is better for vocals and up cloce micing. Ok now you can get back to the numbers.

 

[bennychico11]

You guys hash over the tech stuff, in application high Z mics tend to work better for room ambience or overheads, low Z is better for vocals and up cloce micing. Ok now you can get back to the numbers.

more reason to know how to correctly use them. It would suck to lose high frequency content on your OH with a HI-Z mic.

 

[Pedro De Pacas]

Ben,
Nevermind the critics, your attention to details is much appreciated here.
I have a question, if I may but in.

I have an AKG C1000S condensor mic (lo-Z - I presume), and I was going to connect it to my current setup which is setup for a guitar. Here is my setup

AKGC1000S--->Preamp (GSP7 digitech - input impedence at appr. 20KOhm/ output 51 Ohm)--->Sony Minidisc recorder (I have no spec info for this).

I was going to use a transformer to connect the mic to the Digitech processor/preamp, and was wondering what you thought about the whole setup? thanks in advance