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Re: experiences with sennheiser mkh 70 ?

Subject: Re: experiences with sennheiser mkh 70 ?
From: "Walter Knapp" waltknapp
Date: Wed Oct 18, 2006 8:12 am (PDT)
Posted by: "Gianni Pavan"

>       I love to make recordings with 2 Rode NT1A connected to a SD 722; 
> this way I make ambient recordings with very low hiss. I had the 
> opportunity to use, with the same recorder, a Sennheiser MKH 70 whose 
> specs indicate a self-noise comparable to the Rode mics but with 
> higher sensitivity.hus I expected to get noise free recordings as 
> well; instead my recordings were hissy, much noisier than those made 
> with the Rodes, with the hiss increasing above 8 kHz. Nonetheless the 
> sensitivity and directionality were higher, I was very disappointed 
> by the hiss and now I would ask to this community if somebody else 
> has experience with these mics. Before this experience I was willing 
> to buy one of them, but now I need to understand more.

I have a MKH-70. It's pretty much the same as far as self noise as my 
MKH-60's, there's only 1dBA difference and 10mV/Pa less sensitivity for 
the MKH-60's. In other words very quiet and very sensitive. I have the 
Rode NT1A and they are definitely not as sensitive. Of course they are a 
different polar pattern too, which makes a difference. The NT1A don't 
sound as quiet on self noise as the MKH-70 with my equipment, but it's 
hard to pin down because they are very different mics. I don't even 
consider comparing the two to be at all important, different uses. The 
higher sensitivity of the MKH vs the NT1A means you will use a lower 
gain setting when recording, which lowers the noise level in the recording.

The MKH-70 is rated with a sensitivity of 50 mV/Pa, and a self noise of 
5 dBA. The NT1A is rated with a sensitivity of 25 mV/Pa, and a self 
noise of 5 dBA.

One important difference between the NT1A and the MKH series is 
diaphragm size. This makes considerable difference in the character of 
the sound. The larger diaphragm adds emphasis to lower frequencies and 
resonance compared to the smaller diaphragms of the MKH. This will mask 
high frequency hiss somewhat all on it's own, even if it's sound from 
the environment. Some people rate MKH too precise in their sound which 
is probably at least partially diaphragm size.

Did you have the treble emphasis switch on? That's going to boost the 
higher frequencies. It will sound more hissy that way though it's just a 
increase in the level of the high frequencies. You should only really 
use the treble emphasis switch when your sound sources are pretty 
distant, it's there to compensate for the falloff of high frequencies 
with distance. This would be farther emphasized if you also had the low 
frequency rolloff switched in too.  I never use the treble emphasis and 
only rarely use the low frequency rolloff.

While you are checking the switches make sure the pre attenuation is not 
switched in either. (that makes 8dBA difference in the self noise)

Also, was there anything in the environment that may be the source of 
your hiss? Around here the pines hiss with the slightest breeze, for 
instance. The high sensitivity of the MKH-70 will pick up anything going 
on in the area that it's pointed at. This can bring out things that 
lower sensitivity mics won't. Things that may be quite distant. Around 
here dogs a quarter mile away sound right here in that mic.

Otherwise I'd try another MKH-70, it is always possible the one you had 
is bad. Have Sennheiser check it out and verify it's up to spec. They 
are pretty reliable, but anything can break. Your experience does not 
sound at all like mine.

BTW, before investing check out the MKH-60 as well. You might like it 
better. They are pretty similar. I'm using a MKH-60 in a M/S with a 
MKH-30 and it's excellent. Someday I'll accumulate enough stuff to try 
the same with the MKH-70. So far I've only used the MKH-70 mono. Some 
time I should also try a MKH-80 for the side with these mics, it's specs 
are closer than the MKH-30.


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