SM58 quiet Vs other dynamic mics?

[SoundArfa]

Hi

I own a cheap T-Bone MB 55 and two Mackie EM-89D mics. Yesterday I got myself an SM58 on offer from the Amazon Shure official store.

Trying it out tonight, and comparing it Vs the other two, I noticed that the 58 is quite a bit quieter (Behringer 2442FXUSB on a 60dB preamp channel via XLR)

On PFL, to get just out of the greens I needed to go past 1 O'Clock. The Mackie only needed to go to about 10 O'Clock and the T-Bone around 9 O'Clock. Is this quite normal, maybe due to a.lower bass response, or simply cheaper mics just being louder?

I heard the Beta 58 is louder than the regular 58. Anyway, the sound of the 58 was very nice, fairly uncoloured I thought. but through the LR Mains headphone listen, with some reverb, was very satisfying and crisp. The volume differences between the three mics also seemed less pronounced through the LR mains with reverb.

Interested in your thoughts.....

[AlecSp]

Specs show the sensitivity of the three mics as follows:

T-Bone MB 55 -53 dBV
Mackie EM-89D -52 dBV
Shure SM58 -56 dBV

To understand these figures, the sensitivity is telling us how many decibels are required to produce 1V of output from the mic.

So, yes, the SM58 is less sensitive than the other two mics. Does that make it quieter? Not really. All mics vary in sensitivities, which is precisely why we have a gain control on our mic pre-amps, to adjust for the sensitivity.

True, in days of yore, a mic with a very low output used to require enough gain that the noise floor of the pre-amp became a problem. That's much less the case these days and, anyway, the differences we're seeing with these mics are not huge.

[Sam Spoons]

Which suggests that if the SM58 is a lot* quieter than the others there may be something wrong with it? Can you borrow another SM58 to compare it with?

* If the difference is small in real terms then, as Alec says, it's not a problem.

[James Perrett]

Specs show the sensitivity of the three mics as follows:

T-Bone MB 55 -53 dBV
Mackie EM-89D -52 dBV
Shure SM58 -56 dBV

To understand these figures, the sensitivity is telling us how many decibels are required to produce 1V of output from the mic.

That's not quite how it works. What those figures actually tell us is how much voltage the mic puts out for a standard sound level (usually 94dB SPL which is 1 Pascal). 0dBV is 1 Volt so -60dBV is 1mV and -54dBV is 2mV.

On a mixing desk with a padless preamp, most of the gain is bunched up beyond 3 o'clock so there is probably surprisingly little difference in gain between the 10 o'clock and 1 o'clock settings.

[SoundArfa]

I forgot to mention that I took the mesh grill off the 58 and it became a lot louder. I have noticed that the other two mics have much flatter topped mesh grills, especially the Mackie.

I wonder if I'm just able to get closer in on the flatter topped mics and thus get more volume out of those....

[SoundArfa]

Specs show the sensitivity of the three mics as follows:

T-Bone MB 55 -53 dBV
Mackie EM-89D -52 dBV
Shure SM58 -56 dBV

To understand these figures, the sensitivity is telling us how many decibels are required to produce 1V of output from the mic.

That's not quite how it works. What those figures actually tell us is how much voltage the mic puts out for a standard sound level (usually 94dB SPL which is 1 Pascal). 0dBV is 1 Volt so -60dBV is 1mV and -54dBV is 2mV.

On a mixing desk with a padless preamp, most of the gain is bunched up beyond 3 o'clock so there is probably surprisingly little difference in gain between the 10 o'clock and 1 o'clock settings.

So does this suggest that the 58 is pretty much spot on if I'm dialling in a preamp gain just past 1 O'Clock, and that the other two mics might be a bit on the lord side, especially the T-Bone at 9 O'Clock????

[Hugh Robjohns]

Trying it out tonight, and comparing it Vs the other two, I noticed that the 58 is quite a bit quieter ...

In terms of specified sensitivities, the 58 is 3 to 4dB less sensitive at 1kHz. That's noticeable, but not what I'd describe as a lot quieter in normal use.

However, the mic is designed to be used very close to the mouth – within about 3 inches – and if you are further away than that the bass response falls away rapidly. As a result, the output level also falls away rapidly with increasing distance (especially on male voice) and that might be contributing to the differences you note.

On PFL, to get just out of the greens I needed to go past 1 O'Clock. The Mackie only needed to go to about 10 O'Clock and the T-Bone around 9 O'Clock. Is this quite normal...

It's not abnormal. And as explained above, the gain knob scale is not linear. Often the gain change is quite small at the low end of the range, so there maybe 6dB change between 7 and 11 o'clock, while you might get the same change between 4 and 5 o'clock at the high end.

In other words, don't worry about where the knob is pointing. All that matters is whether you can make the mic loud enough, and whether it sounds alright when you do. It sounds like that's the case, so don't over think it!

[Wonks]

The T-bone MD55 has a neodymium magnet, the Shure has a standard ferrite magnet. Neodymium magnets are a lot more powerful than ferrite ones for a given size of magnet, and so can be used to provide a greater output signal.

The Beta 58A is Shure’s neodymium ‘version’ of the SM58 in general looks and size (though in reality it is best viewed as a different sounding mic but with a similar name used for marketing purposes). The output level of that is similar to the MD55.

The Mackie mic doesn’t state the magnet type, but given its output level, it is almost certainly a neodymium magnet. According to the manufacturer’s mic frequency response charts (always to be used as indicative rather than 100% factual) it also has a much wider treble boost range than the SM58. So it has a pretty flat 5dB boost (compared to the 1kHz value) between 2kHz and 8kHz, whilst the SM58 peak rises much more slowly between 1kHz and 4kHz for a 5dB boost, then has a significant dip around 7.5kHz before riding again to another peak at 10kHz.

That extra early boost above 1kHz is also helping to make the Mackie sound louder than the SM58, as there’s a lot of vocal energy in that region to boost. But it won’t sound quite as natural as the SM58 and could be too bright on some voices.

[ef37a]

Getting enough level from a dynamic mic is much more often a complaint in forums from people recording vocals, especially speech. Not at at all common for live work as singers tend to be belting it out anyway!

As the others have said, just because you need to advance the gain for the 58 relative to the other mics does not mean the Shure is faulty in any way. So long as you can get enough level that is all you need. Hugh's point about working the mic closely is also important. Watch any rock singer and he/she will usually have their lips touching the grill. In any case, the usual limitation for vocal projection is keeping acoustic feedback at bay. The sensitivity of the microphone is largely irrelevant.

Going back to the recording situation. People are often bothered because they find they need the gain on their interface near or at maximum to get speech in the 'magic' -20dBFS region. My Native Instruments KA6 is like that but since the noise level is so low it matters not.
In fact with most modern interfaces the limiting factor for noise of all sorts is their room and external noises.

I have also discovered that the two other mics have a nominal impedance of 600Ohms which will, all things being equal (never are) give a greater signal voltage into the common 1k2-2k mic pre input compared to the 150 Ohms of the SM58. The latter employs a transformer. I doubt the others do?
Dave.

[Dave Rowles]

On PFL, to get just out of the greens I needed to go past 1 O'Clock. The Mackie only needed to go to about 10 O'Clock and the T-Bone around 9 O'Clock. Is this quite normal, maybe due to a.lower bass response, or simply cheaper mics just being louder?

To me those figures seem completely normal. I'd usually have the gain on an analogue desk at around 1 o'clock for a 58. The others I can't comment on, but my sE V7s have a much higher output than my 58s and as such I run the gains lower for those mics.

Realistically, if you've got enough volume out of the mic for your purposes, and you're not getting a load of extra pre-amp noise, then the gain setting is right. While specs and figures can be important, in live sound there is also the element of "it sounds good, therefore it's right" for me. You can go too far into the numbers rabbit hole and lose sight of the end goal...which is good sound.

[Tomás Mulcahy]

The Beta 58A is Shure’s neodymium ‘version’ of the SM58 in general looks and size (though in reality it is best viewed as a different sounding mic but with a similar name used for marketing purposes).

Yes it is a different sounding mic. Any idea what else was changed in the design to create this difference? Or is the change to neodymium the cause of the change? I guess I'm asking about the secrets of magnets, the kind of stuff that mic manufacturers tend to keep to themselves? Or should I be looking in the Journal of Materials Science?

[Wonks]

One fairly big difference is the Beta 58A has a supercardioid pattern, whilst the SM58 is cardioid.

With guitar pickups, the more powerful the magnet used, the brighter the sound is (given say the same humbucking pickup and just changing the bar magnet beneath it) which can be offset by using more winds of thinner wire to up the output and increase the inductance to dull the sound a bit at the same time.

I'd imagine it's something similar with neodymium mics. They generally seem to have a higher upper frequency range (which is less important with most amateur-level PA systems than when recording) and sound a bit brighter.

[ef37a]

The question of magnet types affecting sound is an interesting one.

In guitar speakers there are two main magnet 'camps'. Alnico for the well heeled and ferrite for us mortals. The difference between the two materials is that Alnico is a good conductor of electricity and ferrite isn't. That fact is bound I think to have an influence on the speaker's response?
AFAIK Neodymium alloy magnets are also insulators.

Just to confuse matters further many 'hi fi' speakers use insulating ferrite but then put a socking great copper ring on the pole piece end!

Whether these different materials change a microphones characteristics I do not know.

Dave.

[SoundArfa]

Thanks all for your reassuring responses. The non-linear scale of the gain knob and the differences in magnets make sense.

Special thanks to posters who looked up and explained the specs and frequency responses of my three mics. I guess I could have looked this information up myself but you have deciphered what those specs actually mean in practical use.

[Tomás Mulcahy]

Thanks Wonks.