[Andre Majorel]

On 2005-06-22, Scott Dorsey mentioned that "an LC shunt network
across the input of the preamp would" properly dampen a Shure
SM-57 diaphragm.

In what range of values would you expect L and C to fall ? I'll
get some next time I order components.

I suppose a good, low DA cap would be preferred, like a C0G/NP0,
polystyrene or polypropylene...

Also, what kind of LC network ? Inductor and capacitor in series
between hot and cold ?

--
André Majorel URL:http://www.teaser.fr/~amajorel/
"Marque nouvelle. Dans le stock. Les navires de FL, les
Etats-Unis. Service de client exceptionnel garanti."

[PStamler]

On Jun 5, 7:48*am, Andre Majorel wrote:
On 2005-06-22, Scott Dorsey mentioned that "an LC shunt network
across the input of the preamp would" properly dampen a Shure
SM-57 diaphragm.

In what range of values would you expect L and C to fall ? I'll
get some next time I order components.

I suppose a good, low DA cap would be preferred, like a C0G/NP0,
polystyrene or polypropylene...

Also, what kind of LC network ? Inductor and capacitor in series
between hot and cold ?

I suspect you could get as good results, if not better, with a simple
resistor. For most preamp inputs 681 ohms is good.

Peace,
Paul

[Scott Dorsey]

Andre Majorel wrote:
On 2005-06-22, Scott Dorsey mentioned that "an LC shunt network
across the input of the preamp would" properly dampen a Shure
SM-57 diaphragm.

In what range of values would you expect L and C to fall ? I'll
get some next time I order components.

Don't do it. Try just a 680 ohm resistor. I played with doing a reactive
thing to emulate a transformer but the resistor sounds just as good.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Jay Ts[_2_]]

On Sat, 05 Jun 2010 23:36:51 -0400, Scott Dorsey wrote:
Andre Majorel wrote:
On 2005-06-22, Scott Dorsey mentioned that "an LC shunt network across
the input of the preamp would" properly dampen a Shure SM-57 diaphragm.

In what range of values would you expect L and C to fall ? I'll get some
next time I order components.

Don't do it. Try just a 680 ohm resistor. I played with doing a
reactive thing to emulate a transformer but the resistor sounds just as
good. --scott

Is the idea here to calm the resonant peak of the reactive coil in
the mic capsule? And if so, does anyone know what the frequency of
that resonant peak is? I've been wondering about this for a long time.

In Shure's published frequency response of the mic,

http://www.shure.com/idc/groups/publ...ts/webcontent/
rc_img_sm58_large.gif

the peak in frequency response at just below 1 KHz looks to
me like the resonant peak of an LC circuit, which acts as
a 12 dB/octave low pass filter in frequencies above the peak.

I'm guessing that Shure uses the resonance to extend the frequency
response of the capsule. I'm wondering if anyone can confirm this.
(Or confidently tell me I'm wrong.

I tamed the resonance in my guitar's pickup using a simple resistor.
I didn't know what resistance to use, so first I used a potentiometer
and with a lot of "play testing", dialed in the sound I liked best.
Then I replaced the pot with a resistor for long-term use.

Jay Ts

[Scott Dorsey]

Jay Ts wrote:
On Sat, 05 Jun 2010 23:36:51 -0400, Scott Dorsey wrote:
Andre Majorel wrote:
On 2005-06-22, Scott Dorsey mentioned that "an LC shunt network across
the input of the preamp would" properly dampen a Shure SM-57 diaphragm.

In what range of values would you expect L and C to fall ? I'll get some
next time I order components.

Don't do it. Try just a 680 ohm resistor. I played with doing a
reactive thing to emulate a transformer but the resistor sounds just as
good. --scott

Is the idea here to calm the resonant peak of the reactive coil in
the mic capsule? And if so, does anyone know what the frequency of
that resonant peak is? I've been wondering about this for a long time.

My guess is that open termination causes both the capsule to ring
mechanically and the transformer to ring electronically. Looking at the
high frequency stuff on an impulse (tapping the mike), I would bet the most
dramatic resonance is in the 5-10 KHz range.

In Shure's published frequency response of the mic,

http://www.shure.com/idc/groups/publ...ts/webcontent/
rc_img_sm58_large.gif

the peak in frequency response at just below 1 KHz looks to
me like the resonant peak of an LC circuit, which acts as
a 12 dB/octave low pass filter in frequencies above the peak.

I'm guessing that Shure uses the resonance to extend the frequency
response of the capsule. I'm wondering if anyone can confirm this.
(Or confidently tell me I'm wrong.

My bet is that you aren't seeing the ringing in that diagram because Shure
measured it into a Shure mike preamp (which is transformer-coupled). I bet
that if you did a response into an open circuit it would be very different.
--scott

--
"C'est un Nagra. C'est suisse, et tres, tres precis."

[Anahata]

On Sun, 06 Jun 2010 04:34:08 +0000, Jay Ts wrote:

Is the idea here to calm the resonant peak of the reactive coil in the
mic capsule? And if so, does anyone know what the frequency of that
resonant peak is? I've been wondering about this for a long time.

Whether it's electrical or mechanical, I suspect it's a very high-Q,
narrow band resonance at a frequency that varies from one specimen to
another, so if you were thinking of EQing it out that's not a practical
approach. The resistor flattens the peak without caring what the
frequency was.

--
Anahata
-+- http://www.treewind.co.uk
Home: 01638 720444 Mob: 07976 263827

[Tony[_11_]]

On Tue, 08 Jun 2010 16:50:24 -0500, Anahata wrote:

On Sun, 06 Jun 2010 04:34:08 +0000, Jay Ts wrote:

Is the idea here to calm the resonant peak of the reactive coil in the
mic capsule? And if so, does anyone know what the frequency of that
resonant peak is? I've been wondering about this for a long time.

Whether it's electrical or mechanical, I suspect it's a very high-Q,
narrow band resonance at a frequency that varies from one specimen to
another, so if you were thinking of EQing it out that's not a practical
approach. The resistor flattens the peak without caring what the
frequency was.

And the load resistor can be quite low, even under 100 Ohms. The result is a bit dead
(read "more accurate"), and you have to EQ the lows and highs a bit, but the rolloffs are
both first order, so eminently controllable.
Tony