Mic specs

[Greg Miller]

I've seen a lot of mic specs that list a maximum SPL level (before the mic goes into bad distortion). Right now I'm reading specs for a mic that does *not* list maximum SPL. The specs do list "dynamic range" of 85dB.

In my mind, that is not the same as maximum SPL. "Range" implies "relative to something." To use "range" to specify maximum SPL, it would need to be relative to some other SPL level.

The specs also list S/N = 58dB, as well as maximum output = 150mV. As far as I can figure, these don't tell me anything about maximum SPL.

Supporting that thought, it's hard to imagine that the mic's maximum SPL is only 85 dB SPL.

Am I on the right track here, in thinking that the three specs listed above (dynamic range, S/N, mV output) do not help me know the maximum SPL level for this mic?

Thanks as always!

[Pete Cofrancesco]

In my experience most mics will be ok as long as you use them as intended . Most problems come from misuse, or using the wrong mic (for example putting a condenser mics too close to loud speakers will distort it).
The only time I ran into a problem was a really loud rock concert. If you're looking for a mic that can't be overloaded go for a dynamic mic. These type of mic can take a singer going full blast only an 1" away. Because their not very sensitive work best for sound sources that are very close and loud.

[Patrick Tracy]

Dynamic range is measured from the noise floor to the onset of distortion (at some percent THD). For comparison, S/N is measured from the noise floor to a nominal level (e.g. 0dBVU), with some amount of headroom before the onset of distortion. Neither of these measurements directly specifies maximum SPL, but if something (e.g. the noise floor) is correlated to SPL it could be found indirectly.

[Greg Miller]

Thanks for both of those replies.

Pete, I agree with all your comments. In this case I'm looking at a specific mic, which meets some other criteria. Yet I can't foresee every possible future use, so I want to know where it will overload to avoid using it some day in the wrong situation.

Patrick, you're stating clearly what I thought was the case. A lot of measurements are relative, not absolute. For example, I've seen maximum level specified as SPL or as output voltage. I've seen noise specified as voltage, or as equivalent SPL. If you have the right set of numbers, you can figure out the other numbers.

In the case of this mic, dynamic range is given in dB, but relative to what? Output level is given in mV, but at what SPL is that voltage obtained? Etc. So unless someone convinces me otherwise, I'll stick to my original belief that it's not possible to ascertain maximum SPL from the numbers that are given.

Thanks again.

[Don Palomaki]

Do they list a sensitivity of the mic (e.g., mV or dBV output at 1 Pa SPL)?
The output impedance?
Conditions for the maximum output voltage (e.g., open circuit, 2K load, etc?
Power source (e.g., battery, phantom power, sound card DC bias, etc.)

S/N is also often specified for a certain frequency profile (e.g., A-weighted)
If they list sensitivity one can calculate other parameters.

Making some assumptions based on the standards used by AKG, AT, and Rode: in their mic specs:
Mic maximum SPL is often specified for 1% THD.
S/N is often referenced to 1 Pa (94 dB SPL)
Noise floor is sometimes given in equivalent SPL
Dynamic range is noise floor to 1% THD

150 mV corresponds to -16.5 dBV
So noise floor might be 94 - 58 = 36 SPL
max SPL might be 36 + 85 = 121 dB SPL
If 121 dB SPL = -16.5 dBV
94 dB SPL = -43.5 dBV or 6.7 mV

The confusing spec coupled with the 58 dB S/N sounds like an economical condenser mic, possibly one intended for use with a PC for informal voice (e.g., Skyping) rather than recording.

[Pete Cofrancesco]

In my experience, it’s better to have a variety of value mid range mics made by trusted names like Sennheiser, Audio Technica, Rode than it is to have only one high end or many cheap mics. Don’t get caught up on specs or deals. You can’t go wrong buying popular well reviewed mics from authorized dealers. I wouldn’t recommend too good to be true deals on ebay. Old or knock off mics aren’t a good value.

[Paul R Johnson]

Mics usually fall into categories - condenser vs dynamic or sensitive vs deaf or nice sounding vs nasty.

It's quite rare to buy mics based on their specs, because the manufacturers rarely give them in any meaningful way, or use different test processes. A dynamic range figure and a s/n figure are pretty pointless in an advert because they could indicate something useful or not, so listening to mics is the only real way to choose between them. If you look at the specs for a Shure SM7B it seems to be an insensitive mics with low output and poorer noise figures, but it's a very popular mic. Some condensers have very high outputs but unless the spec gives an output figure for a specified sound pressure level, the specs are meaningless. Noise again can be very confusing but you have to define the 'kind' of noise. Dynamics have a noise figure but for practical purposes, don't generate any - while some condensers hiss - if they have a high output level, you turn them down and don't notice the hiss. See the problem? Your paper specs could be good or bad, but they're not detailed enough to know. Maximum output of 150mV? Probably just dictated (assuming it's condenser) by the available voltage in the power supply.

The only mics that really start to distort with loud sound are badly designed ones. Most that could distort get a -10dB or -20dB pad to sort it, while others have pads but never seem to need them. Most mics at the kinds of SPLs where they could distort, would be deafening to adjust in situ.

Sticking a dynamic of almost any kind inside a kick drum rarely troubles them, and with a pad, most condensers are happy too.

[Allan Black]

Originally Posted by Pete Cofrancesco

In my experience, it’s better to have a variety of value mid range mics made by trusted names like Sennheiser, Audio Technica, Rode than it is to have only one high end or many cheap mics. Don’t get caught up on specs or deals. You can’t go wrong buying popular well reviewed mics from authorized dealers. I wouldn’t recommend too good to be true deals on ebay. Old or knock off mics aren’t a good value.

I agree. It’s frightening how many $20 Asian condensers are available

But that how Rode got started. Pete Freedmans dad Henry ran a shop fixing guitar amps. in Sydney. One day a guy bought in a cheap Chinese mic. to be repaired. Henry figured he could improve it, he did and gave it back to the musician who couldn’t believe the sound. Word got around so Henry made a few of his own design mics.

Some guy says, ‘This mic. will sell like a rat up a drainpipe’ rodent, Rode. And that’s how Rode got started with their first NT mics.

Recently Pete bought Event Electronics, Aphex, (which I’m not a fan of) and SoundField mics.

Btw you won’t read this story on Rodes site, but it’s true, we still enjoy it.

Cheers.

[Pete Cofrancesco]

Originally Posted by Allan Black

I agree. It’s frightening how many $20 Asian condensers are available

But that how Rode got started. Pete Freedmans dad Henry ran a shop fixing guitar amps. in Sydney. One day a guy bought in a cheap Chinese mic. to be repaired. Henry figured he could improve it, he did and gave it back to the musician who couldn’t believe the sound. Word got around so Henry made a few of his own design mics.

Some guy says, ‘This mic. will sell like a rat up a drainpipe’ rodent, Rode. And that’s how Rode got started with their first NT mics.

Recently Pete bought Event Electronics, Aphex, (which I’m not a fan of) and SoundField mics.

Btw you won’t read this story on Rodes site, but it’s true, we still enjoy it.

Cheers.

The OP isn’t giving us much information. Sounds like he saw an inexpensive mic and looked up the spec to see if it’s good. If it's for a paid gig I would simply buy something decent and call it a day. If you're not doing high end studio work you can get by with most anything.

It’s not say only name brand equipment can do well it’s just a matter of whether it’s worth the risk of trying to save a little coin.

[Don Palomaki]

Perhaps the OP could give us the make/model, or a link to it if they are interested in more information.

[Greg Miller]

Originally Posted by Don Palomaki

Do they list a sensitivity of the mic (e.g., mV or dBV output at 1 Pa SPL)?

No, they do not, or I wouldn't have needed to ask my question in the first place.

Originally Posted by Don Palomaki

Conditions for the maximum output voltage (e.g., open circuit, 2K load, etc?

No, as above.

Originally Posted by Don Palomaki

Power source (e.g., battery, phantom power, sound card DC bias, etc.)

They list a range of bias voltage, but that in itself won't tell us about maximum SPL unless we know at least the sensitivity of the mic.

Originally Posted by Don Palomaki

S/N is also often specified for a certain frequency profile (e.g., A-weighted)
If they list sensitivity one can calculate other parameters.

But they do not.

My original question was, I think, quite specific:

Am I on the right track here, in thinking that the three specs listed above (dynamic range, S/N, mV output) do not help me know the maximum SPL level for this mic?

I also listed the numbers for those three specs. I think my original question has been asked and answered: We can't calculate Max. SPL from those three numbers.

Originally Posted by Paul R. Johnson

It's quite rare to buy mics based on their specs

I would never buy any transducer based only on the manufacturer's specs. But I might REFRAIN from buying one based on the specs. e.g. I would never buy a mic with LF rolloff starting at 150Hz for the purpose of recording pipe organ. Most importantly, specs will not tell us how the transducer actually sounds. Also, I suspect that if the specs are less than accurate, they are more likely to be inaccurate in the more desirable way. e.g. if Max. SPL were spec'd at 94dB, I think it's more likely that it would really be 91dB than that it would be 97dB. And if I saw a mic that claimed Max. SPL was 94dB, I wouldn't bother to go any further ... I'd reject that one out of hand.

Originally Posted by Pete Cofrancesco

The OP isn’t giving us much information. Sounds like he saw an inexpensive mic and looked up the spec to see if it’s good. If it's for a paid gig I would simply buy something decent and call it a day. If you're not doing high end studio work you can get by with most anything.

It is not for a paid gig. I'm retired, although I occasionally record a musical performance by one friend or another, just as a favor. In that case I have enough AKGs, Beyers, and ATs (and even a few Crown PZMs) to take care of the job.

However, from time to time someone in this forum asks "are there any good inexpensive mics" ? (Usually they're looking for lavs.) If nothing else I'm a curious bugger, so I sometimes speculate about the same issue. Thus, I did see an inexpensive mic, and I checked the specs for clues that it's pretty bad (i.e. if it had a really low Max. SPL). If I don't find any red flags, I might just buy a sample to see how it sounds. (Amazon Prime includes a wonderful return policy!)

Who knows, I might just find a diamond in the rough that's actually an acceptable mic for some non-critical jobs (which is why people are asking about such a mic in the first place). That doesn't mean I'm suggesting anyone go out and shoot a feature film with one.

Originally Posted by Allan Black

It’s frightening how many $20 Asian condensers are available. But that how Rode got started.

Exactly! Thank you for that comment, and the related story, Allan. That's where I'm coming from. Who knows, I might accidentally stumble upon a company that will become the next Rode.

In fact, I've written to the company who make this mic, asking specifically for a Max. SPL rating. Perhaps they'll send an actual number some day.

At any rate, my original question has been asked and answered. My thanks to those who made helpful contributions.

[Paul R Johnson]

Ah - light is dawning.

I think what you'll find is that the mic is probably a fine and competent performer, but the seller, often Chinese, has a small unit in a big selling centre and know as much about mics as they do knitting needles which they also sell. This is very common. I buy a lot of stuff from these people and they get offered access to items from within their complex, and they sell them. They copy and paste, and often badly copy and paste, the use google translate and end up with meaningless figures. Mic specs are a common example of wrecked specs. Sometimes they even include the wrong info. Like a loudspeaker system using 48V phantom, or a microphone that is 8Ohm impedance. Asking for info is usually a waste of time, as they've never seen the item out of a box, and wouldn't know what it was even if they opened it up?

If it looks good, it might actually be good. Always worth the risk!