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Wooly sound when singing close to mic?

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Wooly sound when singing close to mic?

Postby ultraGentle » Thu Feb 25, 2021 4:25 pm

I'm hearing something I'd like to understand better:

If I sing right up against a condenser mic, there is sometimes a "wooly" or "fuzzy" quality to the recording.

Clearly, I can avoid this by *not* singing too close, but what's actually going on?

My guess: If you get close enough, you create your own little "room" against the mic, and the sound waves bounce back between your mouth and the diaphragm, with some resonances.

Other observations: the exact nature of the fuzz differs per microphone, but subjectively, it seems to happen in the mid-bass region; and the effect seems to be reduced by rotating the mic slightly.

Finally, depending on the mic, sometimes I do like to sing quite close to work the proximity effect; any suggestions for doing this without the attendant wool?
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Re: Wooly sound when singing close to mic?

Postby Hugh Robjohns » Thu Feb 25, 2021 4:35 pm

ultraGentle wrote:If I sing right up against a condenser mic, there is sometimes a "wooly" or "fuzzy" quality to the recording. Clearly, I can avoid this by *not* singing too close, but what's actually going on?

It's called the 'Proximity Effect' or 'Bass Tip-up'. it affects all mics that have an element of pressure-gradient operation -- which means anything with a directional polar pattern. Fig-8 pattern mics suffer from this the most, and cardioids less, although the actual construction of the mic also affects the severity of the effect.

Pressure operated mics -- meaning true omni-directionals -- don't suffer from it at all and, useful fun fact: if the sound source is exactly at the side of a cardioid mics (90-degrees off access) it will have no Proximity Effect at all either... ;)

My guess: If you get close enough, you create your own little "room" against the mic, and the sound waves bounce back between your mouth and the diaphragm, with some resonances.

...it seems to happen in the mid-bass region; and the effect seems to be reduced by rotating the mic slightly.

See comment above! It affects all low frequencies progressively and is due to the physics involved in the way a pressure-gradient mic works, with sound waves being able to reach both the front and rear of the diaphragm.

Finally, depending on the mic, sometimes I do like to sing quite close to work the proximity effect; any suggestions for doing this without the attendant wool?

Nope. If you want the bass boost that comes with the Proximity Effect it's gonna sound wooly... Just the same as if you dial in loads of bass boost on the EQ!
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Re: Wooly sound when singing close to mic?

Postby ultraGentle » Thu Feb 25, 2021 4:49 pm

Thanks for the explanation!

> would happen if you dialed in loads of EQ

Are there nonlinearities in the proximity effect (since it's a physical response) that would result in a subjectively different sound quality from an equivalent, level-matched, frequency-matched EQ bump?

The reason I ask is that there seemed to be a point where the proximity effect degenerated into wool, as though I'd crossed a physical threshold -- but maybe this was a matter of degree, and not kind.
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Re: Wooly sound when singing close to mic?

Postby Kwackman » Thu Feb 25, 2021 4:51 pm

ultraGentle wrote:The reason I ask is that there seemed to be a point where the proximity effect degenerated into wool, as though I'd crossed a physical threshold -- but maybe this was a matter of degree, and not kind.

Maybe you were overloading the capsule or mic amp into distortion?
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Re: Wooly sound when singing close to mic?

Postby ultraGentle » Thu Feb 25, 2021 7:03 pm

@Kwackman, re: overloading capsule: Is there a way to determine this objectively? Or if not objectively, do you know of a sonic reference for what an overloaded capsule sounds like, so I could compare? It's probably not the preamp (?) as gain is only 20% capacity and levels are peaking around -12. I'm singing at a full, but not shouty level into an Audio Technica 2035.
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Re: Wooly sound when singing close to mic?

Postby Kwackman » Thu Feb 25, 2021 8:31 pm

ultraGentle wrote:@Kwackman, re: overloading capsule: Is there a way to determine this objectively?.
Probably, but beyond my knowledge, but if it sounds distorted....

ultraGentle wrote:do you know of a sonic reference for what an overloaded capsule sounds like, so I could compare?.
Sorry, I've no idea if such a thing exists. But, if you say you're preamp isn't going into the red, then IF there is distortion, it's probably the mic!

This is only a guess (the mic capsule getting overwhelmed) , so don't be assuming I know what I'm talking about as there is a lot of evidence around here that I don't!
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Re: Wooly sound when singing close to mic?

Postby ultraGentle » Fri Feb 26, 2021 12:43 am

Thanks! Trying to work though this, and wondering:

If I engage the pad on the mic, does that work at a physical level, thus preventing capsule overload while allowing proximity effect? Or does the reduction happen after overload would occur?
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Re: Wooly sound when singing close to mic?

Postby Tim Gillett » Fri Feb 26, 2021 5:21 am

There is a small amplifier inside the mic. The pad reduces the signal level fed to the amplifier. It doesnt prevent all distortion but means you can sing louder/closer before the amp overloads and distorts.

Be careful about regarding proximity effect too highly. As Hugh said, it's just a side effect of a directional mic. We get proximity effect "thrown in for free" when we buy a directional mic. Most of the time it's an inconvenience and it takes extra time and effort to mitigate it in recording and mixing.

For a directional mic which doesnt exhibit bass tip up, or at least controls it, we have to pay extra. Here's an example.

https://www.shure.com/en-US/products/microphones/ksm8
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Re: Wooly sound when singing close to mic?

Postby Hugh Robjohns » Fri Feb 26, 2021 11:31 am

ultraGentle wrote:If I engage the pad on the mic, does that work at a physical level, thus preventing capsule overload while allowing proximity effect? Or does the reduction happen after overload would occur?

It's not the physical capsule that overloads -- that would be almost impossible to achieve in normal, everyday circumstances. Rather, it's the impedance converting electronics (the 'small amplifier', as Tim calls it) that can be overloaded under very loud conditions.

As Tim says, if the capacitor mic has a 'pad' switch, that reduces the signal level going into the impedance converter and thus reduces the risk of overload when working with close, loud sources. Many capacitor mics have a -10dB pad, while some offer more options (the AKG C414XLS offers -6, -12 and -18dB, for example).

Some microphones also have a (high-pass) 'filter' switch and these are generally designed to compensate for the proximity effect when intentionally using the mic close to a sound source. If so, it will have a gentle 6dB/octave slope starting from a relatively high turnover frequency (typically 150Hz or higher).

However, some mics are provided with a steeper (12dB/oct) high-pass filter with a much lower turnover frequency (perhaps 60Hz or lower) and these are designed to reduce unwanted subsonic noises like mechanical vibrations (rumbles), traffic noise, and the like.

And some mics, have both... a good example being the AKG C414 XLS mic which has three filter options of with turn-over frequencies of 40, 80 or 160Hz. Although not indicated on the mic itself, the first two are steep filters intended for removing unwanted subsonic noises, while the last is gentle and intended to correct for proximity effect -- as this plot from the manual illustrates.

AKG C4141XLS filters.jpg
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Re: Wooly sound when singing close to mic?

Postby ef37a » Fri Feb 26, 2021 6:47 pm

ultraGentle wrote:Thanks for the explanation!

> would happen if you dialed in loads of EQ

Are there nonlinearities in the proximity effect (since it's a physical response) that would result in a subjectively different sound quality from an equivalent, level-matched, frequency-matched EQ bump?

The reason I ask is that there seemed to be a point where the proximity effect degenerated into wool, as though I'd crossed a physical threshold -- but maybe this was a matter of degree, and not kind.

On the matter of EQ 'going in', virtually no interfaces give you any and only a very few even have a high pass filter (bass cut). You can of course use the EQ in your DAW but if you want to have it in real time you will get a delay, latency and that can be very off putting on speech, even in low rates.

One solution (and I get a lot of stick for this quite often!) is a small mixer. The mic channel will have at least bass and treble controls and even quite cheap models, mid band boost and cut as well and best of all you get absolutely zero latency from the headphone or main outputs.

Note, I am not suggestion a USB mixer, the really budget ones have quite severe limitations no, just a basic, 2 mic input mixer with EQ. The mixer feeds the line inputs of the AI.

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Re: Wooly sound when singing close to mic?

Postby CS70 » Mon Mar 01, 2021 1:09 am

ef37a wrote:On the matter of EQ 'going in', virtually no interfaces give you any and only a very few even have a high pass filter (bass cut).

Not sure if I get you right, but there are plenty interfaces with onboard DSP which give latency-free EQ.

For example the Steinberg UR28M which I use often on location has onboard EQ, reverb and compression, and it's far from the only one. My Apollo Twin does it as well, of course.
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Re: Wooly sound when singing close to mic?

Postby ef37a » Mon Mar 01, 2021 1:31 am

CS70 wrote:
ef37a wrote:On the matter of EQ 'going in', virtually no interfaces give you any and only a very few even have a high pass filter (bass cut).
Not sure if I get you right, but there are plenty interfaces with onboard DSP which give latency-free EQ.

For example the Steinberg UR28M which I use often on location has onboard EQ, reverb and compression, and it's far from the only one. My Apollo Twin does it as well, of course.

True but I had assumed the OP was using an AI in the lower price regions? You can get a really good AI for around £200 but are there any with EQ via DSP in that price bracket?

A very good Focusrite/ Tascam whatever and a small mixer is still well under 400 quid. And, I would aver, rather more versatile?

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Re: Wooly sound when singing close to mic?

Postby CS70 » Mon Mar 01, 2021 9:24 am

ef37a wrote:True but I had assumed the OP was using an AI in the lower price regions? You can get a really good AI for around £200 but are there any with EQ via DSP in that price bracket?

No idea :) Just didn't want to leave the impression that there were no interfaces able to do EQ on the way in, as there are quite a bit which can (and the Steinberg is not that pricey at all, especially as you find many second hand these days).

As for the mixer, it's horses four courses I guess. An SSL Six is rather expensive, and for lower-grade stuff I'd rather not having things I don't need or made with live-sound quality in mind in my signal path, if I can avoid it. To say nothing of the bulkiness... on my desk, the thing most at a premium is space! On Friday I made a complicated routing thru my SPL TD, the EQ and a Drawmer gate I got on loan with TotalMix in 30 seconds, and boy I was glad I didn't have to move any cable.

But agree that for 99% of home productions the effect of a cheap mixer on the signal quality isn't a big deal nor the major factor, so it's just down to preference..
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Re: Wooly sound when singing close to mic?

Postby ef37a » Tue Mar 02, 2021 8:44 am

CS70 wrote:
ef37a wrote:True but I had assumed the OP was using an AI in the lower price regions? You can get a really good AI for around £200 but are there any with EQ via DSP in that price bracket?

No idea :) Just didn't want to leave the impression that there were no interfaces able to do EQ on the way in, as there are quite a bit which can (and the Steinberg is not that pricey at all, especially as you find many second hand these days).

As for the mixer, it's horses four courses I guess. An SSL Six is rather expensive, and for lower-grade stuff I'd rather not having things I don't need or made with live-sound quality in mind in my signal path, if I can avoid it. To say nothing of the bulkiness... on my desk, the thing most at a premium is space! On Friday I made a complicated routing thru my SPL TD, the EQ and a Drawmer gate I got on loan with TotalMix in 30 seconds, and boy I was glad I didn't have to move any cable.

But agree that for 99% of home productions the effect of a cheap mixer on the signal quality isn't a big deal nor the major factor, so it's just down to preference..

There is always this dichotomy whenever the use of a budget mixer is proposed. The facts are, such mixers use only 3 or 4 op amps in the 'mic/eq/pan/mixer/output path and contribute next to no degradation to the sound. This is especially true when said mixer is driving the line input of a "£150" interface since the input for say -18dBfs will be well below the output capability of the mixer (usually +22dBu max)

Then, 'we' keep forgetting the results of the Great Mic Pre Amp Shootout! This showed pretty conclusively that the actual electronics in a mic pre amp can cost next to nothing and still stand against designs many time the cost. Even quite low priced mixers have really very good, low noise pre amps with more gain and headroom than AIs have achieved until fairly recently.

The mention of the SSL (slurp) prompts me to say that the specifications are rarely tested and published for mixers at the nifty point. Might they be a bit embarrassing when compared to the Big Boys?

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Re: Wooly sound when singing close to mic?

Postby CS70 » Tue Mar 02, 2021 10:31 am

ef37a wrote:There is always this dichotomy whenever the use of a budget mixer is proposed. The facts are, such mixers use only 3 or 4 op amps in the 'mic/eq/pan/mixer/output path and contribute next to no degradation to the sound.

Sure, and no intention to be a zealot: it all depends on the need. I could also run a 15mt cable around my room, but why doing it unless I really need to? It's just more stuff that can go wrong. And it takes space.

If then we look at the EQ thing, onboard EQs on cheap mixers (with the idea of printing them for mixing) don't usually sound that great. Fine for a live job where the sound is inherently a compromise, but do you really want to print that EQ on your magnum opus?

In most situations where a cheap mixer would do, an interface just performs slightly better in some aspect. Of course not in every context: the one aspect where the mixer wins is of course the haptics. It's got faders and knobs that turn. And perhaps the portability - you can detach it and bring it live.

This is especially true when said mixer is driving the line input of a "£150" interface since the input for say -18dBfs will be well below the output capability of the mixer (usually +22dBu max)

Isn't this an additional reason not to use one?

Then, 'we' keep forgetting the results of the Great Mic Pre Amp Shootout! This showed pretty conclusively that the actual electronics in a mic pre amp can cost next to nothing and still stand against designs many time the cost. Even quite low priced mixers have really very good, low noise pre amps with more gain and headroom than AIs have achieved until fairly recently.

Very much agree, preamps in clean range are not necessarily the issue. However, it's worth pointing out that the article did not really compare Behringer 2012-style bottom-of-the-barrel stuff.. The "worst" of the bunch was perhaps the Mackie VLZ Pro which is certainly not boutique but not too shabby either.

I would guess there are still noisy, low-headroom preamps if one goes cheap enough... :D

The mention of the SSL (slurp) prompts me to say that the specifications are rarely tested and published for mixers at the nifty point. Might they be a bit embarrassing when compared to the Big Boys?

Not sure! Hugh does take measurements, doesn't he? :lol:
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