What am I hearing?

S

Steve Ogden

Well-known member
Hi all,

After a long time on the sidelines, I'm starting to rebuild my kit & gain more experience. I just purchased an AT4053b and a DR100-MK2. I did an informal comparison test by recording direct to a DR100MK2 mic input, then recorded to the same recorder's line-in using the preamp of an old M-Audio Duo interface on 'stand-alone' mode. Mic distance to my mouth (12" or so) stayed the same & had the levels peaking at the same place (-12 db or so). When I played back the files, the "all DR-100" recording had much more room noise - it was very loud and I could hear everything in the room behind my voice. When I played back the recording where I went into the line input of the DR100 from the M-Audio Duo preamp, I didn't hear much of the room noise. It was barely perceptable and it's a noisy room. The background room noise seemed a lot further away although the voice didn't sound as loud. It was an amazing difference.

Is this 'signal to noise' ratio? I've always assumed S/N referred to the internal/self noise & not to the ambient room noise. Hope this isn't too stupid of a question - I'm self taught & not sure how to interpret this & I'd appreciate your observations & comments. My next investment is a Sound Devices 302 & I'll assume that's the reference point for good preamps, but until then I'm trying to learn about what I'm hearing & making do with what I have.

Thanks for your comments.
Steve

Current audio kit: AT4053b, AT BP4029 (MS Stereo Mic), ME-66, Countryman EMW Lav (wired & wireless), DR100MK2.
 
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This seems very strange to me, and sounds much more like a difference in mic distance or position, or some effect or filter that may have been on. Have you looked over the settings?

Signal to noise ratio refers to the difference between the desired signal and unwanted signals, which includes both mechanical and background noise. Sometimes it's used in the other way you are referring to, as in the difference between the desired signal and a systems mechanical noise, but this is more commonly referred to as a systems noise floor.

The 302 is a very good mixer for small gigs, and can be useful even as you expand your kit - a good buy. You may want to look for it used used as they hold their value very well, or even a SD442 (that can sometimes be found for not much more then a new 302). The preamps are excellent and similar to the ones in most professional field gear. It also has nice limiters and monitor options.
 
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If you see it in a specification for a device the "noise" will be the noise the unit generates compared to a standardized signal source. So what it refers to depends on usage.

So in your case you could say you had a different S/N ratio but that would be very misleading because it would imply that the "noise" you are talking about was effected by the change in input. The "noise' that changed with a better, or worse, mic pre will be the hiss of the electronics not the "room noise".

And I really doubt that the room noise changed significantly. It's possible that the external preamp has a roll off in the frequencies that happent to dominate your room noise and that would affect the room loudness. But I suspect that actually nothing changed that much and you are hearing the perceptual difference of the overall levels. It's lower over all and you can mentally compensate better for your own voice than for random noise so you voice doesn't seem much lower to you but the room noise does. I bet if you took both files and put them in a DAW and set the volumes on your voice the same the room sound would be about the same. Of course if you talked lower or were farther away from the mic in one take that one will have more room noise. Mic preamps don't change the pickup patterns of microphones.
 
Thanks for your comments, Jema & Scott.
I was careful to speak at the same level (but I'm no pro. . .), get peaking levels the same, and careful to keep the mic position the same. The results seemed very strange to me & were unexpected - I was expecting & looking for some difference in the self-noise/hiss, not the loundness of the background noise & tone of my voice. I did have the hi-pass on with the DR100 test, and the external preamp doesn't have that feature. But I didn't turn it off (on the recorder) for the line-in/external preamp test. I'll get both files into the DAW this week & look. Also, time permitting, plan to do the same test with the external preamp, the DR100MK2, & the DVX100 mic in and have a ruler or piece of string handy to make sure about mic distance.
 
sfogden said:
I did an informal comparison test by recording direct to a DR100MK2 mic input,
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What does that mean? Does that mean you were using the microphones that are attached to the front of the DR100?

then recorded to the same recorder's line-in using the preamp of an old M-Audio Duo interface on 'stand-alone' mode.
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What does that mean? Does that mean that you were using the AT4053b into an external mic preamp, and then line-level into the DR100?

Let's us ASSUME that you were comparing the built-in mics on the DR100 with an external high-quality hypercardioid mic and an external mic preamp.

1) The microphones built-in to the DR100 are most likely closer to omnidirectional than cardioid. So they were picking up sound from a MUCH broader angle than the AT4053 which is a HYPER-cardioid pattern. This is NOT what we mean by S/N. This is called mic pattern directionality and ambient noise.
2) The self-noise of a $2 mic capsule (such as are used in those hand-held digital recorders) is MUCH higher than in a high-quality professional microphone like the AT4053.
3) The preamp inside most/all hand-held digital records are not notable for being high-quality. They are OK, but nothing particularly special. It is almost certainly the case that the M-Audio Duo preamp is higher quality (most notably lower-noise = higher signal-to-noise ratio, SNR)

Mic distance to my mouth (12" or so) stayed the same & had the levels peaking at the same place (-12 db or so).
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Good. Excellent experimental technique.

When I played back the files, the "all DR-100" recording had much more room noise - it was very loud and I could hear everything in the room behind my voice.
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Because the microphones in the DR100 have a broad pickup pattern. I'm not sure I would even call them "cardioid", but then I am not a marketing manager.

When I played back the recording where I went into the line input of the DR100 from the M-Audio Duo preamp, I didn't hear much of the room noise. It was barely perceptable and it's a noisy room. The background room noise seemed a lot further away although the voice didn't sound as loud. It was an amazing difference.
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Presumably you also mean that you were using the AT4053 hyper-cardioid microphone. That by itself would account for MOST of the difference between the wide "cardioid" mics in the DR100 and the very narrow hyper-cardioid pattern of the AT4053. Now you know why the 4053 microphone costs more than the entire DR100 mics, preamps, recorder, etc.

Is this 'signal to noise' ratio? I've always assumed S/N referred to the internal/self noise & not to the ambient room noise. Hope this isn't too stupid of a question - I'm self taught & not sure how to interpret this & I'd appreciate your observations & comments.
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From your description, you are describing the difference between a rather wide microphone (the DR100 built-in mic) and a very narrow mic (the AT4053). No, this is not what we typically call S/N. You are correct that S/N or SNR typically refers to the INTERNAL noise of the equipment (the microphone, the mic preamp, the recording medium, the transmission medium, etc. etc.)

My next investment is a Sound Devices 302 & I'll assume that's the reference point for good preamps, but until then I'm trying to learn about what I'm hearing & making do with what I have.
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There is no question that a SD302 (or ANYTHING from Sound Devices) is a premium product. However I cringe at people throwing money at a problem without first identifying exactly what the problem IS.
 
Hi Richard, Thanks for the observations & sorry for the lack of clarity in my description of the test.
Never used the DR100MK2 built-in mics in this test- used the AT4053b for both recordings. I was curious to hear the difference between the DR100's preamps and the external unit's preamp (M-Audio Duo). The 1st recording was the AT4053b into the DR100 preamps, the 2nd recording was the AT4053b into the M-Audio Duo ('stand alone mode' just using the preamps) & connecting its' line-out to the DR100 XLR line-in. I expected to hear everything the same except for some difference in the preamp noise - at least that's what I wanted to hear. But was surprised to notice the difference in the loudness & quality of the room/background noise/ambience. So rather than having a quick comparison to learn about preamp noise, I've got more questions than I started with and need to do a better 'test' design.
I really don't want to just throw money at a problem, but do want to get all the links in my chain to be good so that I can focus on the project and not the equipment. Right now the weak link is the preamps and I wanted to get a sense of how much difference do they make.
 
Assuming the same microphone (AT4053) and that your voice was the same level in both tests, the background noise difference cannot be explained simply by the different mic preamps (the DR100 vs. the M-Audio Duo). That is NOT the kind of thing we would expect to hear by simply changing mic preamps. Could you post a sample of the two clips? It would be interesting to hear this phenomenon.

Assuming that you CONFIRMED that you really were hearing the AT4053, and not the built-in mics for the "all DR100 test".
 
"Assuming that you CONFIRMED that you really were hearing the AT4053, and not the built-in mics for the "all DR100 test".
+1 .. Or if one preamp had a high pass filter engaged and the other didn't.
Yes, post clips of these 'tests'.
 
Is there any chance the DR-100 limiter was switched on when your AT4053 was plugged into the MIC input?

Limiters can raise the loudness of the ambient room noise because they allow you to record with more gain applied to your signal while still preventing your audio from clipping.
 
Yes, the limiter was on. I kept the levels down to -12 db, but will turn it off for the next test. I don't think it ever kicked-in, but wil make sure it's off for the next test.
 
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