Anybody got any specs for the SM7b mic?

The Shure website seems to be missing info for Self Noise and Max SPL levels...

If anyone has these specs I'd be grateful if you shared.

Thanks, Dave

Not aware of specs - what's your application? They'll easily handle kick and I haven't noticed any particular issues with self noise on vocals, though the mic is designed to be worked fairly close.

Bob

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www.bickerton.co.nz

Thanks for the response Bob,

I'm currently trying to cover all bases for an organ recording job I have. Unfortunately I'm not going to get into the venue until the day so I'm trying to cover all possibilities. I'm going to take an ORTF stereo pair, spaced omni flanks, spaced omni room mics and I'm hoping to use a single mic right up close to the bass pipes (up to 32' long!). In my other organ recordings I've used this mic to add a little extra bass end when the organ is playing 'way down there' as my ORTF pair (KM184) have a roll off at about 100Hz and I want to catch everything I can on the day.

I already have one of those baby Neumanns, the TLM102, which is actually a really great little mic, and should do for this application as it's max SPL is quoted my Nuemann as 0.5% THD at 144dB which is pretty impressive.

I am hoping the 102 should work perfect but I overheard some people the other day saying that the Shure can handle up to 180 dB! Whether that is true or not (probably not) i thought I'd check it out and I'm just curious. And if it is anywhere near that I'm assuming its because it's got some kind of -30 dB switch on it or something crazy like that?

Anyway, If any one knows I'd love to see some data!

Thanks, Dave

www.microphone-data.com

Reg

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Google less; read more!

A dynamic mic can only have a "self noise" due to the DC resistance of the capsule, transformer and in the SM7b's case the hum bucking coil. I doubt that all adds up to 200R but if it did that is -131dBV, even Prisms don't get that good!

As for max SPL I found some data for the SM57 which was 1%THD at 100Hz (worse case F)at 150dBSPL and the output was getting on for one volt! You could easily drive "proper" 600Ohm studio cans from that!

Yous going to need some inline XLR slugs friend.

Dave.

180 dB figure quoted here:

Recording Hacks

Quote RegressiveRock:

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www.microphone-data.com

Reg

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Thanks Reg but if you have a look then you'll see that there is no data for those properties on mic-data website...

Mike, thanks for that link!

Dave, thanks for your input. When you say slugs do you mean inline attenuators? I'm assuming that would only be needed if you actually started to push that 180dB limit? Also, the lowest note on that 32' bad boy stoops as low at 16 Hz. Do you think THD will be higher down at the mics lowest pickup frequency?


Thanks, Dave

Quote Jonesd90:

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Quote RegressiveRock:

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www.microphone-data.com

Reg

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Thanks Reg but if you have a look then you'll see that there is no data for those properties on mic-data website...

Mike, thanks for that link!

Dave, thanks for your input. When you say slugs do you mean inline attenuators? I'm assuming that would only be needed if you actually started to push that 180dB limit? Also, the lowest note on that 32' bad boy stoops as low at 16 Hz. Do you think THD will be higher down at the mics lowest pickup frequency?


Thanks, Dave

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Oh that's odd, they normally quote the Max SPL.

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Google less; read more!

Quote Jonesd90:

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The Shure website seems to be missing info for Self Noise and Max SPL levels...

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That's because it's a dynamic mic. You won't find those specs for any dynamic mic from any manufacturer (other than dynamic mics with built-in buffers or gain stages) because they are largely meaningless and pointless.

The self noise is only the thermal noise of the mic's output impedance, which is negigible and will be utterly swamped by the preamp's self noise. The max SPL level is determined by the combination of magnetic field strength and allowable coil movement and will be more than high enough for any conventional application -- typically well over 150dB SPL, anyway.

The self-noise and max SPL figures are quoted for electrostatic mics (capacitor and electret) because they are determined by the impedance converter electronics and have a significant impact on the technical performance of the microphone.

Hugh

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Technical Editor, Sound On Sound

Quote Jonesd90:

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...I overheard some people the other day saying that the Shure can handle up to 180 dB!

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Dynamic mics generally become progressively less linear as the SPL rises (ie, the THD figure rises), but I wouldn't be surprised if it can, theoretically, manage that kind of SPL before mechanical clipping occurs (and bearing in mind that 192dB is more or less the clipping point of the atmosphere!).

Quote:

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if it is anywhere near that I'm assuming its because it's got some kind of -30 dB switch on it or something crazy like that?

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No switch, just simple electromechanics!

If you are concerned with capturing the genuine fundamentals of something like a pipe organ with true 32ft stops, then you'd be much better off using decent omnidirectional mics, rather than any kind of directional mic which will inherently have a curtailed LF response.

Typically, when recording pipe organs, I would use either a SoundField mic or some other coincident array for the main pickup, and supplement that with spaced omnis to extend the LF pickup. Finding a mic position that captures everything evenly without suffering from standing waves peaks or troughs can be challenging and time consuming!

And 'close miking' the pipes can reveal a lot of unwanted mechanical noise if you're not careful.

hugh


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Technical Editor, Sound On Sound

Quote Mike Stranks:

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180 dB figure quoted here:

Recording Hacks

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It does indeed say that but gives no distortion figure and my (ever suspect!) math gives an output of 35volts! Surely the traff would long since have saturated? And you need an incredible amount of energy to produce an SPL of 180dB (or a very,very small space) not sure if even NASA could manage that?

Dave.

Quote ef37a:

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And you need an incredible amount of energy to produce an SPL of 180dB (or a very,very small space) not sure if even NASA could manage that?

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Close! The Space Shuttle managed 170dB at 500 feet from the launch pad apparently:

www.dpamicrophones.com/en/Mic-University/Technology-Guide/~/media/PDF/MicU ni/Louder.pdf

And yes... A dynamic mic might 'cope' with such high levels before mechanical clipping, but it would be hugely non-linear (aka distorted).

Hugh

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Technical Editor, Sound On Sound

Hugh,
I doubt that you descend to my level and watch Mythbusters? But last night they reckoned they had produced an SPL of 161dB inside a car with a 52" mechanically driven sub woofer at 16Hz.

My guess is that they got a pretty high level but that the measuring mic "broke" long before they hit 160dB?

Dave. (sorry for the diversionary hijack!)

Haha, no worries for the hijack. I have my answers anyway and I've learnt something new

I am planning on using a (largely) space omni flanking method when recording this organ so hopefully I'll get the bass definition I'm after from those.

Anyway, please hijack away as that's usually when threads get interesting...

Dave

Quote ef37a:

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...they reckoned they had produced an SPL of 161dB inside a car with a 52" mechanically driven sub woofer at 16Hz.

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I think that is entirely possible, and there are certainly measurement mics capable of accurately measureing that kind of level.

I have seen genuine medical papers on the subject of self-inflicted collapsed lungs caused by excessive in-car sound systems. The atmospheric pressure differences that can be created by hefty subwoofers in a small enclosed space like a chav-mobile are apparently quite capable of ripping holes in the lungs of the muppets that indulge in such frivilous endeavours!

Hugh

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Technical Editor, Sound On Sound

Well fine Hugh but 160dB?!!

Given a 100dB/W sensitivity (unlikely at 16Hz!)even 50,000watts would only produce 147dB and that's a LOT of lead acids!

Dave.

Your forgetting the SPL enhancing effects of boundaries and standing waves, Dave.

hugh

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Technical Editor, Sound On Sound

Quote Hugh Robjohns:

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Your forgetting the SPL enhancing effects of boundaries and standing waves, Dave.

hugh

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In a TIN CAN Hugh!???

Dave.

The hifi in my car is rather more modest so I'm not deaf, and there's no need to shout!

Yes, a car is a tin can and a lot of LF will pass through the panels... but a lot wont and in such a confined space it is entirely possible for a substantial SPL to build up, even at LF. Moreover, a lot of these 'cars' have been heavily modified with concrete-lined panels, and they employs ludicrous amounts of amplification and drive units! Half a dozen 15-inch subwoofers with 20kW or more behind them isn't that unusual!

The world record set in 2002 for a car hifi was measured at 177dB SPL:

http://articles.cnn.com/2003-07-02/tech/popsci.stereo.kill_1_audio-system- sound-system-drag?_s=PM:TECH

...and there are plenty of other claims of cars reaching well over 160dB SPL...

http://www.pitch.com/kansascity/deaf-jam/Content?oid=2176182

It's all entirely pointless of course. Many record-breaking systems are only able to generate that kind of level at one resonant frequency. But if it keeps the yoof from mugging old ladies it's probably harmless!

Hugh


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Technical Editor, Sound On Sound

Well the guy doing the sound measurement said that 161dB was a world record in a car so who do you believe?

In any event with that many batteries that hardly qualifies as a car.

Dave.

Very sensibly, Guiness World Records appears not to publish a record for the loudest car sound system...

hugh

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Technical Editor, Sound On Sound