ProSoundWeb Community

Please login or register.

Login with username, password and session length
Advanced search  

Pages: [1]   Go Down

Author Topic: Impedance matching question  (Read 2919 times)

Sidney.Pilien

  • Full Member
  • ***
  • Offline Offline
  • Posts: 122
Impedance matching question
« on: June 03, 2013, 01:02:01 am »

Hi everyone, I have a Yamaha EMX512SC powered mixer and I would like to somehow insert an external eq like the Rolls RPQ160b Parametric Equalizer if possible. I use this mixer for small venues where the the space is so small that often times the mics are directly in front of one of the speakers (Yamaha 10" wedges) spaced about 6 feet or so to the mics. The mixer has no insert point for eq so I as thinking of Stereo out > Rolls > channel in. Here are some of the specs:

Yamaha input
Mic line load impedance 2 K Ohm
For use with nominal mics  50-600 ohms mics

Rolls output
Output Impedance 50 ohms
Master level  -12db- +12db

I'm getting by on the graphs with no feedback but the cuts are too extreme. Thanks.






Logged
Sidney Pilien  
               
As Schultze would say "I know nutting!"

Jordan Wolf

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1384
  • Location: Collingswood, NJ
Re: Impedance matching question
« Reply #1 on: June 03, 2013, 07:54:34 am »

Hi everyone, I have a Yamaha EMX512SC powered mixer and I would like to somehow insert an external eq like the Rolls RPQ160b Parametric Equalizer if possible...The mixer has no insert point for eq so I as thinking of Stereo out > Rolls > channel in.
Sidney,

That won't work the way you want it to.  With that mixer, you don't have the flexibility you need to patch in an external EQ in any way that would be beneficial to using it as a powered mixer.

The only way to make it work is to not use the power amp section, and hook up the EQ inline to the (unpowered, line-level) Main Out 1/4" jacks on the front side.  You would have to use another amp or powered speakers, but it would work that way.

These little mixers are very limited in what they allow the user to accomplish; as long as you can work within those constraints, it's still usable - when you outgrow those, it's time to upgrade.
Logged
Jordan Wolf
<><

"We want our sound to go into the soul of the audience, and see if it can awaken some little thing in their minds... Cause there are so many sleeping people." - Jimi Hendrix

Frank DeWitt

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1010
    • LBP DI Box
Re: Impedance matching question
« Reply #2 on: June 03, 2013, 03:37:37 pm »

Two separate issues.  Impedance matching was once part of Audio.  It is not near a important anymore.  A 50 ohm mic can be plugged into a preamp with 10,000 input impedance with out any problem.

Second,  There is no equipment that allows you to violate the laws of physics.  A mic 6 ft in front of a speaker and in front of the speaker is going to be a problem.  If the speaker is a monitor you can get some help from a mic that is directional in it's pickup pattern. If the mic is truly in front of the speaker (speaker / mic / audience) then you can get some help by moving the mic VERY close to the talker. (a head worn mic.)
Logged
Not to Code

Scott Wagner

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 1020
  • Richmond, VA
Re: Impedance matching question
« Reply #3 on: June 07, 2013, 11:19:07 am »

Impedance matching was once part of Audio.  It is not near a important anymore.  A 50 ohm mic can be plugged into a preamp with 10,000 input impedance with out any problem.
You can do this without a problem, but the tonality will be different.  For an interesting experiment, grab something with variable impedance (like, say, a Summit Audio TD-100), and try sweeping the input impedance (or "loading" knob on the TD).  The results are not subtle.
Logged
Scott Wagner
Big Nickel Audio

TJ (Tom) Cornish

  • Hero Member
  • *****
  • Offline Offline
  • Posts: 4284
  • St. Paul, MN
Re: Impedance matching question
« Reply #4 on: June 07, 2013, 07:37:09 pm »

You can do this without a problem, but the tonality will be different.  For an interesting experiment, grab something with variable impedance (like, say, a Summit Audio TD-100), and try sweeping the input impedance (or "loading" knob on the TD).  The results are not subtle.
While this is true, modern console pre's which are 2K-3K ohms are a sufficiently light load as to not affect the mic much - dialing the impedance way down might be interesting as a studio effect, but you have a lot more ability to degrade the sound than improve it.

Passive guitar or bass pickups have less energy to drive an input, which is a larger issue for live sound than mics, and active DIs are available with extremely high input impedance to address this.
« Last Edit: June 07, 2013, 07:40:46 pm by TJ (Tom) Cornish »
Logged

Stefan Maerz

  • Full Member
  • ***
  • Offline Offline
  • Posts: 202
  • Knoxville Tennessee
Re: Impedance matching question
« Reply #5 on: June 07, 2013, 08:16:20 pm »

Second,  There is no equipment that allows you to violate the laws of physics.  A mic 6 ft in front of a speaker and in front of the speaker is going to be a problem.  If the speaker is a monitor you can get some help from a mic that is directional in it's pickup pattern. If the mic is truly in front of the speaker (speaker / mic / audience) then you can get some help by moving the mic VERY close to the talker. (a head worn mic.)
A parametric eq might help a little bit as he will have better frequency selection....like if it is feeding back directly between two eq bands, the cut won't have to be as drastic to accomplish the same goal. The bandwidth control on a parametric vs no bandwidth control on a graphic also helps minimize the destructive effect. I think he is doing big cuts to get sufficient GBF, and as a result the tone is really suffering....this way the cuts will still be big, but they will be placed better and affect a narrower bandwidth.

But yeah, I agree it is much more sensible to resolve this issue in some of the other ways if at all possible.
Logged

ProSoundWeb Community

Re: Impedance matching question
« Reply #5 on: June 07, 2013, 08:16:20 pm »


Pages: [1]   Go Up
 



Page created in 0.023 seconds with 20 queries.