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Re: dynamic microphones

Subject: Re: dynamic microphones
From: "Dan Dugan" dandugan_1999
Date: Wed Mar 7, 2007 9:49 am ((PST))
>  >> I contacted Heil a few weeks ago asking them to consider building a
>>>  dynamic omni similar to their studio cardioids. Being a less-is-more
>>>  kind of guy, I keep nursing the notion that high-quality dynamics
>>>  could greatly simplify things in the field -- if the compromises
>>>  would ever become tolerable.
>>
>>  But at -53, the Heil dynamic cardioid's output is still at least 13 dB
>>  below typical electrets, and over 20 dB below some.
>
>Would you be willing to explain this further, Dan? I don't think I have
>a real clear understanding about the relationship between sensitivity
>and output voltage.

They are the same thing, just expressed in different figures. I have
an old Shure slide-rule calculator (SRC-1) that I use to compare the
figures, though it has a serious flaw in the dBV scale--they have an
arrow for dBV/uBar (74 dB SPL), but not one for dBV/Pa (94 dB SPL),
which is the more common measuring point. I just added another arrow
to mine.

Typical correspondences:

dBV/Pa   Open Circuit mV
-60         1.0
-50         3.2 (hot dynamic mic)
-40        10.0 (condensor mic)
   0      1000.0 (1 Volt)

You could set up a spreadsheet to do the same calculation. I prefer
using the dBV scale just because it tells me instantly what the
difference between mic sensitivities is in dB.

>And on a related topic, I've played around lately with a pair of Audio
>Technica AT804 dynamic omnis, which have a relatively high output
>compared to some common dynamic vocal mics.

The 804's output is -49, 4 dB hotter than the Heil's spec. So that
tells you what you need to know about the levels--you'd have 4 dB
more preamp noise with the Heil.

>High-end response of the
>804s drops off too quickly for them to be a lot of use for my purposes,
>but I find it interesting that I sometimes prefer hearing clean preamp
>noise to the dirty self noise of, for example, the Shure WL183s. Walt
>has made this point several times before. The CHARACTER and QUALITY of
>a condenser mic's self noise (not merely its level) is something worth
>considering when making evaluations.

Yes, a single number doesn't tell you the spectrum or the texture of the no=
ise.

-Dan Dugan




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