High SPL Damages Mics, Fact or Myth?

A

AcoosticZoo

New member
Is anyone aware of any the scientific research that proves High SPL damages mics. There are two opposing camps so who can you trust?

I'm just trying to understand why loud spl doesn't hurt mics. Maybe someone with more technical MIC knowledge can chime in.

If you overload an electrical circuit long enough you can shorten it's life span or even change its physical state permanently, why doesn't this apply to microphones?

Thanks.

Josef Horhay
Mixing Engineer
www.acoosticzoo.com
 
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Well if there is scientific research that *proves* it, we don't need a discussion, just a link, no?

I suppose first we have to define a SPL. I'm pretty sure that 180dBSPL would damage some if not most mics (many dynamics could take the punishment though). The issue is how robust the diaphragm is, but I don't know much about mechanics so we'll leave that there.

As for electrical components, condenser mics almost all have very robust components at their front end: tubes or discrete FETs. The FETs will typically have a gate-source breakdown voltage of ~25V. That would be achieved at something like 154dBSPL for a typical condenser mic without its pad engaged, assuming the diaphragm hadn't bottomed out already. Since distortion would be unacceptable for at least 10dB before that point, one would hope the engineer would have noticed.

ICs can be much more fragile than discrete FETs, but it's pretty rare to see them as the first link in the chain.
 
With this as my source, I say that 250 db would vaporize most mics
http://www.makeitlouder.com/Decibel Level Chart.txt

I like 310 db:

310 (N)KRAKATOA VOLCANO ERUPTION-1883 A.D., CRACKED ONE FOOT THICK CONCRETE
AT 300 MILES, CREATED A 3000 FOOT TIDAL WAVE, HEARD 3100 MILES AWAY,
SOUND PRESSURE CAUSED BAROMETERS TO FLUCTUATE WILDLY AT 100 MILES
INDICATING LEVELS OF AT LEAST 170-190 DB (P) AT THIS DISTANCE OF 100 MILES
EVEN WHEN SHOUTING IN SOMEONES EAR, COULD NOT BE HEARD AT 100 MILES
CAUSED FOG TO APPEAR AND DISAPPEAR INSTANTLY AT HUNDREDS OF MILES
ROCKS WERE THROWN TO A HIEGHT OF 34 MILES. DUST AND DEBRIS FELL CONTINOUSLY FOR 10 DAYS AFTER BLAST. PRODUCED VERY COLORFUL SUNSETS FOR ONE YEAR, EJECTED 4 CUBIC MILES OF
THE EARTH. CREATED ANTI-NODE OF NEGATIVE PRESSURE AT THE EXACT OPPOSITE SIDE OF THE EARTH.SOUND COVERED 1 / 10 OF THE WORLDS SURFACE, SHOCK (SOUND) WAVES “ECHOED” AROUND THE EARTH 36 TIMES AND LASTED FOR ABOUT A MONTH! -REF.19.


Even my trusty SM57 couldn't take that!
 
Well, if you are greater than 194dBSPL, that means you are inside of a shockwave; probably not a pleasant place for a mic to be (and see their note about wind pressures from blasts being much greater than sound pressure).

One bit about Krakatoa is wrong, the tsunamis recorded were at most about 150ft (still a kickass tsunami). 3000ft is like large asteroid impact size.

Also, the 4 cubic mile figure sounds impressive, until you realize that is a mere 0.000000005% of the Earth.:p

I would have used a Beta 52 :cool:
 
In Austin, TX, you get a ticket at 86dB. Large drumcorps produce in the 100dB - 110dB range. Lightning which is missing from that list is typically called 120dB. Bear in mind that mics have greater proximity to the sound than most human ears. dB at the source is not quite the same as dB at the audience.
 
Any SPL without a distance to source stated is fairly meaningless. But for recording music, close micing a drum can be upwards of 140dBSPL at about an inch off the head, when hit very hard. A blaring guitar cab right at the grille could be 136dBSPL.
 
mshilarious said:
Any SPL without a distance to source stated is fairly meaningless. But for recording music, close micing a drum can be upwards of 140dBSPL at about an inch off the head, when hit very hard. A blaring guitar cab right at the grille could be 136dBSPL.
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I've always wanted to know that, was actually planning to grab my spl meter and go get some readings on the kick drum, but since I'm by myself today, I think that's not going to work. :spank:

I can only think of the Kick and cabinets been the loudest things in a recording studio.

would it be safe to say that nothing in the studio could generate a high enough spl to damage any mic (excluding ribbons)?
 
AcoosticZoo said:
I've always wanted to know that, was actually planning to grab my spl meter and go get some readings on the kick drum, but since I'm by myself today, I think that's not going to work. :spank:
Click to expand...

It wouldn't work anyway, the transient peak on the kick is too fast for the usual type of meter. Instead, calibrate a recorded tone at 94dBSPL on the meter (1kHz, so weighting doesn't matter). Leave 50dB of headroom. Now, using the same setup, record your kick drum and compare the two levels.

would it be safe to say that nothing in the studio could generate a high enough spl to damage any mic (excluding ribbons)?
Click to expand...

Generally, yes. Even ribbons can tolerate high SPLs, it's wind pressure that causes problems for them. Don't stick them in the port of a kick drum or a cabinet.
 
mshilarious said:
Even ribbons can tolerate high SPLs,
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Let's put it little differently--out of all microphones ribbons can tolerate the highest SPL ;)

But again, the problem is not the SPL, but sound blasts. Kicks can ruin not only ribbons, but constant exposure to such blasts can destroy even condensers...

Best, M
 
Marik said:
Let's put it little differently--out of all microphones ribbons can tolerate the highest SPL ;)

But again, the problem is not the SPL, but sound blasts. Kicks can ruin not only ribbons, but constant exposure to such blasts can destroy even condensers...

Best, M
Click to expand...

Would you please clarify what you mean by sound blasts? Is this equivalent to a wind blast caused by the drum skin moving or plosives from vocals?
 
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