Why two Mics ?

[BILL POSTERS]

Theres been a lot of early 70s live stuff on TV lately, anybody else noticed that a lot of bands had 2 different Mics taped together for vocals ? I remember seeing it a lot at the time, but have never really been sure why it was done that way.

Was one of them for foldback, or recording or what ?

Edited July 17, 2012 by BRANCINI

[bremen]

[quote name='BRANCINI' timestamp='1342526318' post='1736516']
Theres been a lot of early 70s live stuff on TV lately, anybody else noticed that a lot of bands had 2 different Mics taped together for vocals ? I remember seeing it a lot at the time, but have never really been sure why it was done that way.

Was one of them for foldback, or recording or what ?
[/quote]

It's anti-feedback. They are wired out-of-phase, so sound arriving at both (ie from the PA) is cancelled out. You just sing into the one, so you don't get cancellation.

[Bill Fitzmaurice]

[quote name='bremen' timestamp='1342526600' post='1736527']
It's anti-feedback. They are wired out-of-phase, so sound arriving at both (ie from the PA) is cancelled out. You just sing into the one, so you don't get cancellation.
[/quote]+1, a technique pioneered by the Dead, necessitated by their Wall of Sound. They didn't use monitors, rather the entire system provided both the FOH and personal monitoring as they were set up in front of it. That required the nearly 100% common mode rejection of sound that was picked up by both mics while not affecting the sound picked up by only the one mic that they sang into.

[bremen]

I think Motorhead still do it. Probably not so much to avoid feedback as to avoid further amplifying the incredible racket bouncing around onstage.

[BILL POSTERS]

Thanks, Hadnt thought of that. Sounds like a good idea to me.

Just two in series, opposite ways, or with a one stage pre amp or something to invert one of them ? I think I might try it.

[bremen]

[quote name='BRANCINI' timestamp='1342538437' post='1736792']
Thanks, Hadnt thought of that. Sounds like a good idea to me.

Just two in series, opposite ways, or with a one stage pre amp or something to invert one of them ? I think I might try it.
[/quote]

It'd be messy to wire them in series. Easier to stick each through its own preamp, invert the phase on one, and sum them.

[Bill Fitzmaurice]

[quote name='bremen' timestamp='1342538589' post='1736797']
It'd be messy to wire them in series. Easier to stick each through its own preamp, invert the phase on one, and sum them.
[/quote]You'd parallel wire them into a single channel, one with the cable reverse polarity, using a dedicated Y connector to do it.

[Chris Horton]

I have seen this on TV and never really gave it too much thought ,
I have learnt something new today , thanks

[Lozz196]

And strangely enough, it gets the vocals over better through the pa, even though they`re both set to the same eq/volume. I would never have believed that, until in my old band, the singer did it at a rehearsal studio, as the pa was rubbish. With each mic alone, he couldn`t be heard - together, he could be.

[geoffbyrne]

So tell us more - what's a simple way to do this considering most have XLR plugs on the cables? Any circuits etc?

G.

[geoffbyrne]

And why hasn't someone(!) designed/invented a double mic rig & cable to do this very job if it works that well? (I claim the rights on that, by the way! )

G.

Edited July 19, 2012 by geoffbyrne

[Ian Savage]

Isn't it a bit of a ballache getting the mics far enough apart to just sing into one of them whilst having them close enough together to provide a decent CMRR though?
Never tried it, but with the mics, say, 5cm apart a bit of back-of-a-fag-packet maths says that they'll already be out-of-phase at around 3300Hz, so wouldn't reversing the phase cause reinforcement and potentially make feedback problems worse?

[bremen]

[quote name='geoffbyrne' timestamp='1342689099' post='1739197']
And why hasn't someone(!) designed/invented a double mic rig & cable to do this very job if it works that well? (I claim the rights on that, by the way! )

G.
[/quote]

I'm sure you can get noise-cancelling mics using this technique but right enough I haven't seen any 'off the shelf' ones for live vocals.

[BILL POSTERS]

[quote name='geoffbyrne' timestamp='1342689035' post='1739194']
So tell us more - what's a simple way to do this considering most have XLR plugs on the cables? Any circuits etc?

G.
[/quote]

They always seemed to be two different mics, rather than two the same, probably a reason for that. I guess with a balanced mic, you could reverse the two unscreened wires in the XLR, or open the Mic and reverse the wires to the insert, with a single screened lead mic youd have to reverse the wires to the insert.

[bremen]

[quote name='BRANCINI' timestamp='1342695420' post='1739386']
They always seemed to be two different mics,
[/quote]

http://www.thegearpage.net/board/showthread.php?t=803194&page=2

"
Lemmy from Motorhead loves loud monitors, so his monitor engineer
taped two 57's together, and played with the position of the mic capsule
to use phasing to achieve higher,clearer gain before feedback.

Once he found the sweet spot, he gaff taped the crap out of it and they used
that rig for ages! If you look around the internet you can probably find pictures of it.
They only sent one of the mic feeds to FOH of course."

[Bill Fitzmaurice]

[quote name='BRANCINI' timestamp='1342695420' post='1739386']
They always seemed to be two different mics, rather than two the same, probably a reason for that.
[/quote]If the mics are not identical the technique won't work, so if that's the case the mics are being fed to two different consoles. That was done a lot in the 70s, using one console for the FOH and the other for the recording, as most consoles then didn't have the ability to do both simultaneously.
[quote]with the mics, say, 5cm apart a bit of back-of-a-fag-packet maths says that they'll already be out-of-phase at around 3300Hz, [/quote]Not if the elements are on the same plane.

[bremen]

[quote name='Bill Fitzmaurice' timestamp='1342700896' post='1739529']
If the mics are not identical the technique won't work, so if that's the case the mics are being fed to two different consoles. That was done a lot in the 70s, using one console for the FOH and the other for the recording, as most consoles then didn't have the ability to do both simultaneously.

[/quote]

Seems an odd way of going about it. Why not just use one mic, one transformer, two mixers?

Perhaps the 'different mics' were the capsule taken out of an SM57 and an SM57.

[Cosmo Valdemar]

Always wondered this myself - particularly watching Free live at the Isle of Wight.
You learn something new every day don't you.

[Bill Fitzmaurice]

[quote name='bremen' timestamp='1342701437' post='1739544']
Seems an odd way of going about it. Why not just use one mic, one transformer, two mixers?
[/quote]Easy to say that today, in the 70s not so much. Much of what we take for granted today didn't exist then. Keep in mind that in 1970 the Shure Vocal Master was state of the art.

[bremen]

[quote name='Bill Fitzmaurice' timestamp='1342704884' post='1739627']
Easy to say that today, in the 70s not so much. Much of what we take for granted today didn't exist then. Keep in mind that in 1970 the Shure Vocal Master was state of the art.
[/quote]

You're telling me the spiltter transformer was invented in 1980?

[Bill Fitzmaurice]

[quote name='bremen' timestamp='1342705117' post='1739632']
You're telling me the spiltter transformer was invented in 1980?
[/quote]I doubt that, but they would not have been common items in everyone's kit. True FOH consoles as we know them today were still few and far between even in 1980. Most of what was being used through the 70s for touring was studio gear, and most of that prior to 1975 was originally made for broadcast, not live sound. Even balanced mics using XLR connectors weren't standard until the mid 70s. They existed, but most PA mixers made prior to 1975 had unbalanced 1/4" inputs.

[bremen]

I like your sig.