Mic impedance - and some other things

[Guest]

Archived from groups: rec.audio.pro (More info?)

Hi!

Finally I got my new Focusrite TwinTrak Pro. I bought it to be able to
record my 4x12 Marshall cab with 2 mics, while being able to compress them
altogether. Previously I used a Focusrite TrakMaster and a Behringer
Ultra-Voice Pro for the 2 mics, but they weren't linkable.
Now I find that the sound of the TwinTrak is much more enjoyable than that
of the TrakMaster. The AIR button is really interesting...
But I have a problem and that's my question. I use two different mics to
capture my cabs sound:
- Shure SM57
- Neumann KM 84i.
I have some other mics but I found these 2 giving the best results.
The new Focusrite TwinTrak has knobs to set mic impedance (60 - 3K Ohms). My
real question is that how to set these knobs for the above mentioned two
mics?
Thanks a lot for answering!

bence

 

[mark]

Archived from groups: rec.audio.pro (More info?)

whoops, my bad...

look up the rated load impeadance for those mics and set pre to those
values

Mark

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

Locsmándi Bence <locsmandi.bence@chello.hu> wrote:
>But I have a problem and that's my question. I use two different mics to
>capture my cabs sound:
>- Shure SM57
>- Neumann KM 84i.
>I have some other mics but I found these 2 giving the best results.
>The new Focusrite TwinTrak has knobs to set mic impedance (60 - 3K Ohms). My
>real question is that how to set these knobs for the above mentioned two
>mics?

You'll find with the KM84 that it doesn't matter... the mike will sound
pretty much the same no matter how the knob is set. With the SM57 you
will find that the load changes the sound a lot, but you'll have to figure
out which sound you want.
--scott
--
"C'est un Nagra. C'est suisse, et tres, tres precis."

 

[mark]

Archived from groups: rec.audio.pro (More info?)

what are the mics connected to?

Mark

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

Thanks Scott for answering!
The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms actual)...." -
which one to set?
The KMi manual says: "The KMS has an electrical source impedance of 150
ohms. All the other microphones have an electrical impedance of 200 ohms.
[...] The input inpedance of the following amplifier should be at least five
times as great, i.e.>= 1000 ohms or >= 250 ohms respectiverly." - this is
for a general manual for the KMi series.
So, what value to go for?
Thanks again!

bence

"Scott Dorsey" <kludge@panix.com> az alábbiakat írta a következõ
hírüzenetben: d3esvc$mb9$1@panix2.panix.com...
> Locsmándi Bence <locsmandi.bence@chello.hu> wrote:
>>But I have a problem and that's my question. I use two different mics to
>>capture my cabs sound:
>>- Shure SM57
>>- Neumann KM 84i.
>>I have some other mics but I found these 2 giving the best results.
>>The new Focusrite TwinTrak has knobs to set mic impedance (60 - 3K Ohms).
>>My
>>real question is that how to set these knobs for the above mentioned two
>>mics?
>
> You'll find with the KM84 that it doesn't matter... the mike will sound
> pretty much the same no matter how the knob is set. With the SM57 you
> will find that the load changes the sound a lot, but you'll have to figure
> out which sound you want.
> --scott
> --
> "C'est un Nagra. C'est suisse, et tres, tres precis."

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

You can read about it in my first letter.
Anyway, they are an SM57 and a Neumann KM 84i.
Thanks

b.

"Mark" <makolber@yahoo.com> az alábbiakat írta a következo hírüzenetben:
1113257224.502561.233650@g14g2000cwa.googlegroups.com...
> what are the mics connected to?
>
> Mark
>

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

On Mon, 11 Apr 2005 22:46:53 GMT, "Locsmándi Bence"
<locsmandi.bence@chello.hu> wrote:

>Thanks Scott for answering!
>The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms actual)...." -
>which one to set?

Reread the last sentence Scott wrote below. You'll have record
something at each setting of the switch, then listen back, and then
(this could be the hardest part) decide which setting gives the sound
you like best (for that particular guitar/amplifier/song).

>The KMi manual says: "The KMS has an electrical source impedance of 150
>ohms. All the other microphones have an electrical impedance of 200 ohms.
>[...] The input inpedance of the following amplifier should be at least five
>times as great, i.e.>= 1000 ohms or >= 250 ohms respectiverly." - this is
>for a general manual for the KMi series.
>So, what value to go for?

As Scott says below, it doesn't matter (phantom-powered mics have
small preamps that buffer the element, eliminating changes in tone due
to different loading, though there may still be slight changes in
volume), but I'd go for the highest setting, to put the least load on
the mic and give the most voltage transfer. OTOH, try each setting and
see if Scott is right in saying it will likely sound the same.

>Thanks again!
>
>bence
>
>"Scott Dorsey" <kludge@panix.com> az alábbiakat írta a következõ
>hírüzenetben: d3esvc$mb9$1@panix2.panix.com...
>> Locsmándi Bence <locsmandi.bence@chello.hu> wrote:
>>>But I have a problem and that's my question. I use two different mics to
>>>capture my cabs sound:
>>>- Shure SM57
>>>- Neumann KM 84i.
>>>I have some other mics but I found these 2 giving the best results.
>>>The new Focusrite TwinTrak has knobs to set mic impedance (60 - 3K Ohms).
>>>My
>>>real question is that how to set these knobs for the above mentioned two
>>>mics?
>>
>> You'll find with the KM84 that it doesn't matter... the mike will sound
>> pretty much the same no matter how the knob is set. With the SM57 you
>> will find that the load changes the sound a lot, but you'll have to figure
>> out which sound you want.
>> --scott
>> --
>> "C'est un Nagra. C'est suisse, et tres, tres precis."

-----
http/mindspring.com/~benbradley

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

Locsmándi Bence wrote:
>
> The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms
> actual)...." - which one to set?

> The KMi manual says: "The KMS has an electrical source impedance of
> 150 ohms. All the other microphones have an electrical impedance of
> 200 ohms. [...] The input inpedance of the following amplifier
should
> be at least five times as great, i.e.>= 1000 ohms or >= 250 ohms
> respectiverly." - this is for a general manual for the KMi series.
> So, what value to go for?

Scott's answer was right on (no surprise) but he left out some details
that might help you better understand it.

A SM57 is a dynamic mic. Its output terminals are attached to a coil
of wire wrapped around an iron core (a trnasformer) that eventually
leads to another coil of wire, a core and a magnet (the mic element).
The coils of wire, etc. have substantial inductance, resistance and
even some capacitance. How they respond somwwhat depends on what else
you attach across the mic's output terminals. On balance, the SM57 is
designed to be fairly resistant to changes in its response due to
loading. Most of the effects are at higher frequencies, some above the
audible range.

The Neumann KM 84i being a condensor mic apparently still has a
transformer, but due to the presence of an electronic buffer (powered
by the phantom voltage) it is less susecptible to changes in response
due to loading.

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

On Tue, 12 Apr 2005 00:46:53 +0200, Locsmándi Bence wrote:

> Thanks Scott for answering!
> The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms
> actual)...." - which one to set?
> The KMi manual says: "The KMS has an electrical source impedance of 150
> ohms. All the other microphones have an electrical impedance of 200
> ohms. [...] The input inpedance of the following amplifier should be at
> least five times as great, i.e.>= 1000 ohms or >= 250 ohms
> respectiverly." - this is for a general manual for the KMi series. So,
> what value to go for?

I think the KMi manual is right. Microphones are made by microphone
manufacturers. They do the best they can to get a good sound. It is a
strange idea you can improve the sound of the microphone by adding a
shunt resistor that would have cost the manufacturere $ 0.03 to add.
The normal way is to have a preamp input with sufficient high input
impedance and (a few k) and drive it with a source with sufficient low
impedance (50 - 300).

--
Chel van Gennip
Visit Serg van Gennip's site http/www.serg.vangennip.com

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

In article <x7D6e.985$0z2.299@news.chello.at> locsmandi.bence@chello.hu writes:

> The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms actual)...." -
> which one to set?

The one that you think sounds best. If you can't tell any difference
in the sound as you switch through the available choices, pick one
that's typical of most modern preamps, 1000 to 2000 ohms.




--
I'm really Mike Rivers - (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

In article <3c1ivbF6f6h49U1@individual.net> chel@vangennip.nl writes:

> It is a
> strange idea you can improve the sound of the microphone by adding a
> shunt resistor that would have cost the manufacturere $ 0.03 to add.

Maybe so, but most honest mic preamp manufacturers have some reactive
components associated with their adjustable input impedance. Some use
a tapped transformer (which might cost the mic manufactuer $75 to add)
and some use inductors and capacitors in a network that approximates
the complex impedance of an input transformer that they're trying to
emulate.



--
I'm really Mike Rivers (mrivers@d-and-d.com)
However, until the spam goes away or Hell freezes over,
lots of IP addresses are blocked from this system. If
you e-mail me and it bounces, use your secret decoder ring
and reach me here: double-m-eleven-double-zero at yahoo

 

[Guest]

Archived from groups: rec.audio.pro (More info?)

On 4/12/05 5:53 PM, in article znr1113272772k@trad, "Mike Rivers"
<mrivers@d-and-d.com> wrote:

>
> In article <x7D6e.985$0z2.299@news.chello.at> locsmandi.bence@chello.hu
> writes:
>
>> The SM57 manual says: "Rated impedance is 150 Ohms (310 Ohms actual)...." -
>> which one to set?
>
> The one that you think sounds best. If you can't tell any difference
> in the sound as you switch through the available choices, pick one
> that's typical of most modern preamps, 1000 to 2000 ohms.

I guess we shouldn;t wonder about what year 57 it is... And whether there's
a transformer IN there or not (used mics are Fascinating).