Large Diaphragm condenser for choirs/orch/etc.

Posted: Fri Jan 25, 2008 11:48 am

Sweet. Thanks for the info... I did not realize this about the diaphragms.

Unfortunately, those mics recommended are FAR too expensive... I'm no professional yet! I just have a project studio that's probably only worth 2 of those mics. For recording live acoustic music (small choirs, chamber, solo, etc.), would a M/S (figure 8 ribbon paired with a LDC or SMD) work well?

Perhaps there are cheaper alternatives to SDC's which has a good balance between low self noise and off axis coloration? I guess low self noise IS indeed a big priority for me. Mostly because I'm using cheaper pre-amps (Presonus) and cables (Peavey w/Neutriks)... also, the hall I generally record in contains a lot of noise from the air system (HVAC I think it's called??!). I'm guessing that the only way to get a good balanced mic is to spend no less than $1000... Then it's either noisy mics, or less accurate mics... right?

Thanks for the help guys.

Posted: Fri Jan 25, 2008 1:08 pm

I would not focus on the low self noise at this point. Even the mics with self noise of 20+ dB would suit most every recordist and would still be lower in noise than the traditional concert hall of most mid-level ensembles.

Not to mention, self-noise is only have the equation. Sensitivity is the other. SDC can be made to be quite sensitive (although, usually beaten out by their larger siblings). A mic with a high sensitivity and a medium to low self-noise will seem quieter on the recording in most cases than a quiet mic with low sensitivity.

This is how Earthworks gets by with their "Quiet" series mics. Check the specs, they're no quieter than their non-QTC series mics, they're just far more sensitive.

In an affordable range of SDCs, you might want to consider the Shure KSM series, AT 4041/4051, Rode NT55 and similar.

Cheers-
J.

Posted: Fri Jan 25, 2008 3:08 pm

Cucco wrote:

A mic with a high sensitivity and a medium to low self-noise will seem quieter on the recording in most cases than a quiet mic with low sensitivity.

Yes, I used to think so, too, but that's not quite the way it is... Self-noise is not related to sensitivity, it's measured in SPL.

Other way round: Sensitivity is measured at 94 dB SPL. Regardless of the electrical level that 94 dB SPL will translate into (aka sensitivity), the mic's S/N ratio (usually quoted in relation to 1Pa/94 SPL as well) at e.g. 20 dB of self noise will be 74 dB, and at 6 dB it will be 88dB. Higher sensitivity will not change that. (Hope I'm not stating the all-too-obvious...)

I've found an Earthworks SR78 (which does not claim to be particularly quiet) to be way too noisy to be even used as a harpsichord spot mic...

As for good low-cost SDCs, I'd like to mention the Beyerdynamic MC930.
But I've also use a pair of AKG 414 B-TL (not TL-II) as AB main mic quite successfully...

Daniel

Posted: Fri Jan 25, 2008 3:19 pm

d_fu wrote:

Yes, I used to think so, too, but that's not quite the way it is... Self-noise is not related to sensitivity, it's measured in SPL.

I know what you're saying and agree - however, the quoted spec of a fixed dB noise rating for each mic is directly related to (or more accurately to say - "impacted by" or "affected by")the amount of gain applied to that mic using your mic preamp. Where you have to use less gain, you will have lower (relative) noise levels. However, there's no escaping the S/N ratio - it's a matter of maximizing the headroom and gain of the mic at hand.

Posted: Sat Jan 26, 2008 12:42 am

Ardroth wrote:

Unfortunately, those mics recommended are FAR too expensive... I'm no professional yet! I just have a project studio that's probably only worth 2 of those mics. For recording live acoustic music (small choirs, chamber, solo, etc.), would a M/S (figure 8 ribbon paired with a LDC or SMD) work well?

There are many suggestions being made here...

I'd forget about MS for now, mostly because you'll need a means to decode it, and also because it is not the most versatile technique around for the money.

I'd put in a recommendation for a pair of Rode NT5s, which are SDC cardioids and are sold in matched pairs. A pair of those will allow a range of near-coincident (ORTF, etc.) and coincident (XY) methods, making it equally useful for large or small ensembles.

If you can stretch the budget a bit further, a pair of NT55s with cardioid and omni capsules is also a good choice. IMHO, the NT55 with omni capsule performs well above its price point. That set-up won't cost you much and adds spaced omnis (AB) to the near-coincident and coincident methods offered by the cardioids.

They're also very versatile for close miking, which sometimes is the best thing to do...

Posted: Sat Jan 26, 2008 11:40 am

Decode it?
It does not take much effort at all to copy one track and phase reverse it.

Posted: Sat Jan 26, 2008 2:21 pm

Yes, but decoding it live while recording can be a bit more tricky. It's tough to monitor an undecoded MS signal without thinking you've been licking some acid earlier in the day.

Posted: Sat Jan 26, 2008 7:59 pm

Makes sense.

BTW, tones of really great info in this thread, so thank you every one for expanding my understanding of microphones.

Posted: Sun Jan 27, 2008 4:09 am

Cucco wrote:

It's tough to monitor an undecoded MS signal without thinking you've been licking some acid earlier in the day.

Prior to getting my Nagra V (which has MS decoding on board), I made half a dozen or so MS recordings without decoding during monitoring. By paying careful attention to the individual M and S signals, and judging what I thought *ought* to be in the centre and what *ought* to be in the sides, I figured I could do a pretty job of it.

Every single one of those recordings was a spectacular failure. I would've been better off dropping that acid when the curtain went up and spending the rest of the concert cowering in the corner of a bathroom, afraid of the soap dispenser...

Posted: Sun Jan 27, 2008 5:05 am

Cucco wrote:

d_fu wrote:

Yes, I used to think so, too, but that's not quite the way it is... Self-noise is not related to sensitivity, it's measured in SPL.

I know what you're saying and agree - however, the quoted spec of a fixed dB noise rating for each mic is directly related to (or more accurately to say - "impacted by" or "affected by")the amount of gain applied to that mic using your mic preamp. Where you have to use less gain, you will have lower (relative) noise levels. However, there's no escaping the S/N ratio - it's a matter of maximizing the headroom and gain of the mic at hand.

This is not correct Jeremy. The self noise figure is completely independent of sensitivity, by design. Its measured in equivalent sound pressure level, thus removing sensivity, ie mv/Pa from the equation.

Posted: Sun Jan 27, 2008 9:27 am

Well, the sensitivity and the self noise are related and it boils down to Signal to Noise Ratio. If the SNR is the same between two mics, the only variable at this point is the preamp and its noise imparted at given gains. So a low noise, low sensivity mic should, in theory, be no noisier than a higher noise higher sensitivity mic if the noise and sensitivity go up by equal levels and the SNR is the same.

Posted: Sun Jan 27, 2008 10:02 am

Let me just put it in different terms.

Take 2 mics. One of which has a 7 dB self noise and a low sensitivity (11dB/PA).

The second has a high sensitivity (40dB/PA) and a 20 dB self noise.

To get the same level of signal out of the first mic, you'd have to amplify it by let's say 13dB (I haven't done the math so I'm probably way off - let's just work on hypothetical.)

Now, the equivalent noise from mic a is 20dB since you've boosted the existing noise by 13dB. (Last time I checked, you boost everything that comes down the line, including noise.)

So, if everything else were equal between these two mics, you should get a pretty darn similar sound and noise figure.

If this is incorrect, please state how as this has been my understanding as long as I can remember.

Posted: Sun Jan 27, 2008 10:52 am

Let's put it in a less simple term -

SNR is determined by the delta between the fixed *input* level of 94dB at 1kHz (1 Pa) and its self-noise figure which is determined as the electrical *ouput* of the mic with no load and no gain.

Since this delta always results in a figure of less than 94dB, is it not safe to assume that NO mic is suitable for 24bit recording?

My point is, determining SNR is a good factor for demonstrating a mic's self noise, but little else of relevance since it would be more accurate to measure the output of the microphone with a specified input and its output with no input.

Since the self noise output does not vary based on input yet output signal does, how does the existing SNR have any relevance to actual performance of the mic?

Posted: Sun Jan 27, 2008 4:02 pm

I remember we had a debate about this very early on. Could find the thread but nevermind, he is the explanation.

Take two mics, A and B, with the same self noise of 15dBA, but mic A has a sensitivity of 10mV/Pa and mic B has 40mV/Pa.

Put them up in front of a lute which produces 25 dBA at 1m. Mic A preamp will be on a setting which is 20 log 40/10 more gain than mic B's preamp setting, but the recording will have the same SNR for both ie 10dBA, ASSUMING the mic preamps noise floor is insignificant.

This last assumption is my only qualificiation and is true for most modern pres, they have insiginificant noise floors compared to mics.

Posted: Sun Jan 27, 2008 5:32 pm

Whats depressing is that I am unable to fully understand what you just said.
I think it is time for me to do my home work.

This topic sponsored by: