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Author: Paul StamlerPaul Stamler Date: Nov 29, 2006 00:29
Hi folks:
A couple of months ago, after I'd reported the results of our experiments in
lower-impedance loading of the Shure SM57, a couple of folks asked about the
results on other microphones. Tonight in class we did the experiment; we
tried four microphones as drum overheads, plus two on acoustic guitar. (We
had to clear out of the studio at 10 pm to let the next person in.)
Microphones:
Shure SM57 (again)
Electro-Voice RE15
Electro-Voice PL20
Sennheiser MD421 (Mark I)
Preamp: Universal Audio 2-610, both channels set to 2k load
Loading device: Gizmo (XLR cable with 698 ohm resistor across pins 2 & 3)
Recorder: Radar system, working at 24/96.
With the Gizmo in line, I calculate the load to be 517 ohms.
We used our Studer analog machine's VU for a level meter, and after the
basic level on each mic was set, we matched the two channels to within 0.1dB
(1 pointer-width) using a tone generator feeding into a guitar amp.
Results on drums:
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Author: Jim GillilandJim Gilliland Date: Nov 29, 2006 03:37
Paul Stamler wrote:
>
> Microphones:
> Shure SM57 (again)
>
> Preamp: Universal Audio 2-610, both channels set to 2k load
>
> Loading device: Gizmo (XLR cable with 698 ohm resistor across pins 2 & 3)
>
> With the Gizmo in line, I calculate the load to be 517 ohms.
>
> SM57: Dramatic difference again; what had been a brittle, harsh, edgy sound
> became something one of the students, a confirmed loather of SM57s, said was
> "not...half...bad". To me it actually began sounding sort of like my guitar,
> which it sure as hell didn't with the 2k load.
Paul, thanks for posting this report.
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Author: Peter LarsenPeter Larsen Date: Nov 29, 2006 05:41
Paul Stamler wrote:
[lotsa interesting data]
> MD421: Some sort of change in the midrange with the lower-impedance load,
> and nobody liked it. Everyone preferred the sound with the 2k load.
Sennheisers recommendation for loading their dynamic mics used to be to
load with 10 times their source impedance, nominally it is a 200 Ohm
microphone.
> Paul
Peter Larsen
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Author: FedericoFederico Date: Nov 29, 2006 06:55
In your opinion is the Shure SM7B sensitive to loading too?
F.
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Author: GKBGKB Date: Nov 29, 2006 07:19
What is your opinion [ having some experience with this ]
on making a box with a low range pot or switch ? not worth the effort
for the difference in values ]
regards Greg
"Paul Stamler" pobox.com> wrote in message
news:rxbbh.385393$QZ1.107113@bgtnsc04-news.ops.worldnet.att.net...> Hi folks:
>
> A couple of months ago, after I'd reported the results of our...
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Author: H. SchaapH. Schaap Date: Nov 29, 2006 08:18
> Hi folks:
>
> A couple of months ago, after I'd reported the results of our experiments
> in
> lower-impedance loading of the Shure SM57, a couple of folks asked about
> the
> results on other microphones. Tonight in class we did the experiment; we
> tried four microphones as drum overheads, plus two on acoustic guitar. (We
> had to clear out of the studio at 10 pm to let the next person in.)
After I read the article of, i think it was, Scott I made a gizmo and
tried
the SM57 with a Chandler Germanium on a resonatorguitar. While fiddling
the feedback on the Chandler the (Gizmo)SM57 gave a beautiful tone.
Now the gizmo is always a try when using the SM57.
Other dyn. like the MD421 and some AT didn't give better results.
Henk
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Author: Mike RiversMike Rivers Date: Nov 29, 2006 11:50
GKB wrote:
> What i was suggesting is that the shure attenuator , gutted may give you
> three level of load , but perhaps one is enough and cheaper !
But the Shure attenuator costs $50 or so, and there's no reason for one
to ever break (at least not in a way that you could still use the case)
so it seems silly to buy one and gut it just to make an adjustable
load.
Get a small box, mount a male XLR on one end and a female one on the
other end, and put a rotary switch in the middle with as many different
resistors as you want.
If you read Paul's article, you'd know that the optimum load for the
mic is not just the resistor in the gizmo, but that resistor in
parallel with whatever the input impedance of the mic preamps is. So,
for the same mic, you'd want a different resistor for a preamp with a
1K ohm input impedance than one with a 2.5K ohm input impedance.
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Author: MarkMark Date: Nov 29, 2006 14:54
>> No, the claim is that dropping to about 500 ohms does
>> seriously good things to the SM57, hard-to-hear mild good
>> things to the RE15 and PL20 (presumably the RE20 as well)
>> and doesn't sound so good on the MD421 Mk I. Most pres
>> these days are about 1500-2500 ohm input impedance. I
>> don't know what dropping that to 1k would do, not having
>> tried it, but it's reasonable to assume that it would do
>> less than dropping to 500 ohms.
>
> 500 ohms it is.
>
>> For about $9 you can buy two XLR plugs or a barrel
>> connector and a resistor, and try it for yourself. Based
>> on our tests, I recommend a nice thumpy fingerpicked
>> acoustic guitar as a revealing sound source.
>
>
Why go through all this trouble...
you can do the same thing with an EQ during mix, and you can adjust it
after the fact... ...
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Author: MarkMark Date: Nov 29, 2006 17:13
Scott Dorsey wrote:
>>
>>Are you claiming that you can get a response curve by changing the mic
>>loading that you can't get by using an EQ? I doubt it.
>
> Absolutely! Changing the loading changes the impulse response. If the mike
> is ringing like hell because it's not loaded enough, no EQ in the world will
> fix it.
>
>
Well EQ changes the impulse response too....
So if there is a resonance that rings at say 10kHz, you don't think an
EQ notch at 10 kHz will compensate for that just as well as additional
damping due to mic loading??
I think if both are mic and EQ are minimum phase systems then they can
compensate each other... but perhaps you are right, an underdamped
resonance might not be a minimum phase system, let me think about it.
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Author: MarkMark Date: Nov 29, 2006 19:21
>>
> Besides, ringing isn't just a peak in response that you can notch out.
No not true..... that is exactly what ringing is...
if it is a LINEAR system, (which a mic with peaking is) then it cannot
ADD any new frequency components, only modify the amplitude and phase (
and group delay) of the ones already there.
If there are new frequency components then it is not a linear system
and we usually call this distortion as in harmonic or intermodulation
distortion.
A PA system in feedback by the way is a non linear system, if it was
linear the feedback tone would without bound.
Mark
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