PSW Recording Forums: Klaus Heyne's Mic Lab => "Maximum SPL"

Members

FAQ

Home

Home » R/E/P » Klaus Heyne's Mic Lab » "Maximum SPL" - How Is It Defined?

Show: Today's Messages :: Show Polls :: Message Navigator

E-mail to friend

"Maximum SPL" - How Is It Defined? [message #328243]

Thu, 27 March 2008 13:05

wildplum
Messages: 33
Registered: May 2004
Location: Oakland

Member

How do I interpret the following specifications (from the Mojave Audio MA-100):

MAXIMUM SPL: 120dB
DISTORTION: head amp only , not to exceed .4% @ 140 dB SPL

Am I correct to assume that the capsule distorts at 120dB while the mic amp can go to 140dB (at .4%)? That is, the capsule will distort before the amp. If this is the case, then the usable max SPL (assuming usable means a non distorted signal)is 120dB- although the amp can handle more, you will get distortion above 120dB because that is all the capsule can handle. Yet I see reviews of this mic stating it can handle 140dB. So I am a little confused.

Paul Tumolo
Wildplum Recordings
a micro label, studio and remote recording service

Report message to a moderator

Re: max spl?? [message #328294 is a reply to message #328243 ]

Thu, 27 March 2008 15:33

Martin Kantola
Messages: 234
Registered: June 2005

Active Member

By coincidence I found the specs for another microphone today, the Didrik de Geer one:

Sensitivity:
A sound pressure of 100dB presents -27dBm at the output terminals

Max SPL:
140 dB

Max output level:
+14 dBm

Frequency response of amplifier and transformer:
8Hz - 200KHz (-3dB)

Noise level at output terminals:
-112dBm A weighted

Polorization voltage:
Front membrane 0v
Stator 120v
Rear membrane 240v

Not always that easy to compare these specs...

Martin

This message may have been edited by the moderator without my knowledge.

Report message to a moderator

Re: max spl?? [message #328313 is a reply to message #328294 ]

Thu, 27 March 2008 16:09

Schallfeldnebel
Messages: 589
Registered: October 2004
Location: Europe

Gold Member

Martin, are you sure about this?

Polorization voltage:
Front membrane 0v
Stator 120v
Rear membrane 240v

I cannot believe De Geer puts 120 V polarization on that capsule, the membrane's must collapse. Or he must have used larger spacing between backplate and membranes, which indeed will lower the mechanical distortion.

Erik Sikkema

(I found the source on internet, it is clearly stated)

Sound of the Month, Steinway, Het Concertgebouw Amsterdam:
http://webzoom.freewebs.com/eriksikkema/Steinway.mp3

Report message to a moderator

Re: max spl?? [message #328461 is a reply to message #328313 ]

Fri, 28 March 2008 02:59

Martin Kantola
Messages: 234
Registered: June 2005

Active Member

In an earlier thread here about these microphones it became clear that he does some extensive capsule modifications including re-tensioning the diaphrams. My guess is that the unusually high polarisation voltage is needed to keep the S/N reasonable. Believe that the noise specified would translate to 15dB(A), which would be 21db(A) with 60V. Please correct me if my math is bad here.

But to return to the subject, the max SPL is to me another specification that really doesn't tell anything about how the microphone works in a recording situation. Except if it's a very low number of course. Finding the noise level spec to be equally misleading sometimes, because there is less and more annoying types of noise spectrums.

It could be interesting to try to assemble a list of the features/specifications that really define the microphone. Doubt that they can all be measured and printed, but who knows. At least we should be able to get a better picture than with today's typical numbers.

Martin

This message may have been edited by the moderator without my knowledge.

Report message to a moderator

Re: max spl?? [message #328462 is a reply to message #328313 ]

Fri, 28 March 2008 03:00

Tomas Danko
Messages: 3263
Registered: May 2004
Location: Stockholm, Sweden

Platinum Member

Didrik once told me these figures as well. He used to buy the CK12 capsule and spent about a week to "fix what was broken". IIRC he did a lot of tweaking around with the tension and backplate, there may be some previous discussions about these things here on PSW. Last time I heard, he told me he was going to in-source the capsule/membrane and make it himself but that would take a few years because he was moving to a bigger place and it'd take a long time to reset and align all his tools.

Regarding noise, he has also told me that while his microphone may not be as quiet as others, the noise profile of his is a lot more "musical" and less offending than other examples. His point-of-view was that noise is not as harmful as some people would say, as long as it's the "right" kind of noise that is less obvious and/or annoying. So he'd rather trade the noise floor for something else. Whatever that may be.

"T(Z)= (n1+n2*Z^-1+n2*Z^-2)/(1+d1*z^-1+d2*z^-2)" - Mr. Dan Lavry
"Shaw baa laa raaw, sidle' yaa doot in dee splaa" . Mr Shooby Taylor

Report message to a moderator

Re: max spl?? [message #328473 is a reply to message #328462 ]

Fri, 28 March 2008 04:36

Schallfeldnebel
Messages: 589
Registered: October 2004
Location: Europe

Gold Member

Tomas Danko wrote: "So he'd (De Geer) rather trade the noise floor for something else. Whatever that may be".

Lower distortion

If he enlarges the space between backplate and membrane, and compensates the lower output by using a higher polarization voltage, he is lowering the distortion.

Erik Sikkema

Sound of the Month, Steinway, Het Concertgebouw Amsterdam:
http://webzoom.freewebs.com/eriksikkema/Steinway.mp3

Report message to a moderator

Re: max spl?? [message #328708 is a reply to message #328473 ]

Fri, 28 March 2008 18:07

Klaus Heyne
Messages: 2026
Registered: April 2004

Platinum Member

I am not happy that this discussion meanders towards third party hearsay, which is discouraged in the forum's Ground Rules.
If Mr. DeGeer does not want to participate in our discussion personally, it's his choice and everybody's loss.

In the absence of direct testimony, nonsensical rumours like "retensioning" CK12 diaphragms ensue: These diaphragms are cut to size after they are glued to the ring, and their tension cannot be altered afterwards.

Klaus Heyne
German Masterworks
www.GermanMasterworks.com

Report message to a moderator

Re: max spl?? [message #328774 is a reply to message #328708 ]

Sat, 29 March 2008 03:24

Martin Kantola
Messages: 234
Registered: June 2005

Active Member

OK, for sake of clarity, here's the first hand information Thomas got:

"I had the pleasure to get a visit by Didrik de Geer today, he came by to say hi and we had a brief chat about this and that. I took the opportunity to ask him a few of the questions from this forum.

He does indeed favor the recent capsules as opposed to the vintage NOS, since he feels they are superior in terms of electrostatic properties, for instance, not to mention being more uniform in response between individual units. He is tweaking with the cavity and the shims to alter the tensioning. Furthermore, he keeps repeating that the capsule is not made of teflon but of nylon (the only teflon part would be around the cable). I don't know who said it's made of teflon, but I will pass this message on nevertheless.

The problem is that he is not willing to give all the details about what he does (of course), in all he is spending about 72 hours to "fix" the capsule since it is "wrongly set" from the factory. And as far as problems happen, I'm not even remotely up on par with the technical issues the way you guys are. If you want me to define what some of this is supposed to mean (ie cavity, shim) I can only relay the information to Didrik and write it down for you. I hope you are able to extract some information out of this, however small.

Didrik de Geer does not have an Internet-connection, let alone a computer or a television set. And he doesn't want to have anything to do with such things."

The last part explains why we can't expect Mr. de Geer to participate any day soon...

Anyway, this is interesting but drifting off topic. How should we best read specifications (or should we mostly ignore them and listen?) and could there be a better set of specs that would tell us more?

Martin

This message may have been edited by the moderator without my knowledge.

Report message to a moderator

Re: max spl?? [message #328775 is a reply to message #328708 ]

Sat, 29 March 2008 03:30

Martin Kantola
Messages: 234
Registered: June 2005

Active Member

Klaus Heyne wrote on Fri, 28 March 2008 23:07

These diaphragms are cut to size after they are glued to the ring, and their tension cannot be altered afterwards.

Here's a weak theory; could it be that he adds an extra spacing ring which pushes the glued diaphragm outwards, creating more tension and at the same time increasing the distance to the backplate? He would then have to modify the backplate to compensate for the effect on the frequency response.

Martin

This message may have been edited by the moderator without my knowledge.

Report message to a moderator

Re: max spl?? [message #328782 is a reply to message #328708 ]

Sat, 29 March 2008 05:44

Tomas Danko
Messages: 3263
Registered: May 2004
Location: Stockholm, Sweden

Platinum Member

So far all my posts in this thread regarding Didrik de Geer's microphones contain information from 2nd party (ie, myself) and not 3rd.i Bearing in mind previous discussions about these microphones I only bring forward what came out of Didrik's mouth straight to my ears.

I was under the impression this was confident enough information to be forwarded to the forum.

Apropos the "tensioning" I recall a previous post years ago where we rectified this, after I had spoken to Didrik to ask this particular question among other queries. Also, someone else posted a response he got from Didrik, due to other reasons. All in all, IIRC Didrik stated that he did not cut out and reglue the membrane, but that the so called "tensioning" was done in by other means.

I'm rather lousy with the PSW search engine, so apologies for not including links to these posts.

"T(Z)= (n1+n2*Z^-1+n2*Z^-2)/(1+d1*z^-1+d2*z^-2)" - Mr. Dan Lavry
"Shaw baa laa raaw, sidle' yaa doot in dee splaa" . Mr Shooby Taylor

Report message to a moderator

Re: max spl?? [message #328868 is a reply to message #328243 ]

Sat, 29 March 2008 12:26

Bbob
Messages: 30
Registered: May 2006
Location: Ashland Massachusetts USA

Member

wildplum wrote on Thu, 27 March 2008 13:05

That's how I interpret it. In other words, at 1 kHz, 120dB at the capsule will still leave another 20 dB of head amp headroom. It is necessary to have headroom for peak nonsinusoidal acoustic energy if the figure stated is RMS based. It does not mean that the capsule cannot handle something more than 120dB at some frequencies, and I do not think it means that there must be distortion above 120 dB, but I do think that means the designer is sure that it can go that high, probably with some margin for error.

It would be helpful if the manufacturer could chime in on these things and discuss how the measurements are made and/or calculated or extrapolated.

I know from experience that it is better to use a conservative number. BTW it is my opinion that a more meaningful number for actual users and not academics would come from SPL measurements across the usable spectrum, rather than at one frequency. Also, the techniques used to determine max SPL are not discussed here. Finally, a half a percent of harmonic distortion on top of what is probably already a distorted guitar amp or some super loud source may not be very significant.

Reviews could deal in superlatives, so, the bigger number may have been used.

Bob Crowley

http://microphonium.blogspot.com

BBob

Report message to a moderator

Re: max spl?? [message #328884 is a reply to message #328868 ]

Sat, 29 March 2008 13:37

Klaus Heyne
Messages: 2026
Registered: April 2004

Platinum Member

Mr. DeGeer is an intelligent, living, breathing being, and in his best years, for heaven's sake, not someone whose ideas need intuitive interpretation, because he is incapacitated.

Out of respect for the previous posters who in good faith posted DeGeer's opinions (from the perspective of the readers, that would be third party):
I will not delete the posts, but from now on, opinions will need to be expressed by the people themselves here, not interpreters, no matter how well-intentioned.

Klaus Heyne
German Masterworks
www.GermanMasterworks.com

Report message to a moderator

Re: "Maximum SPL" - How Is It Defined? [message #328906 is a reply to message #328243 ]

Sat, 29 March 2008 14:56

volki
Messages: 233
Registered: June 2004
Location: Berlin, Germany

Active Member

... to reply to the initial poster's question:

capsule (=head) and electronics (= head amp) can be looked at individually in terms of distortion. depending on the design, either capsule or electonics may be the limiting factor when looking at the distortion of the mic as a whole. in the "old days", the head amp used to be the limiting factor due to the lower headroom of most designs. today, with quite a bit of high-headroom designs around, the distortion of the capsule itself comes into play.

definition of a mic's max SPL: that SPL at which the mic's output signal reaches 0.5% THD (total harmonic distortion).

characteristics of capsule and amp distortion can be quite different. capsule distortion rises rather gently, doubling with every 6 dB of SPL - e.g. 0.5% @120, 1% @126, 2% @132... downwards, it's 0.25% @114, 0.125% @108... respectively.
the distortion characteristic of an amp can range from
a gentle rise towards - and even above - 0.5% THD (most tube designs) to being virtually non-existent below the overload point but followed by heavy clipping once that point is exceeded.

gentle increase of distortion is less audible than sudden clipping, which is especially true for transients. thus, especially tube mics may be operated beyond the max.SPL point in certain situations - the mojave, as a tube mic, most probably being in that camp, too.

Volker Meitz

Report message to a moderator

Re: max spl?? [message #328907 is a reply to message #328884 ]

Sat, 29 March 2008 14:58

Schallfeldnebel
Messages: 589
Registered: October 2004
Location: Europe

Gold Member

Klaus,

I must admit that the higher polarization De Geer is using has tickled my curiosity.

Erik Sikkema

Sound of the Month, Steinway, Het Concertgebouw Amsterdam:
http://webzoom.freewebs.com/eriksikkema/Steinway.mp3

Report message to a moderator

Previous Topic:	Good books on mics
Next Topic:	What capsules on KM100 preamps?

Goto Forum:

-=] Back to Top [=-

[ Generate printable PDF ] [ Syndicate this forum (XML) ] [

]

Current Time: Fri Jul 4 17:30:32 CDT 2008

Total time taken to generate the page: 1.18306 seconds

Recording Engineering & Production: The nuts and bolts of making records better, not just louder and cheaper. Some of the brightest minds from the creative and scientific world of audio discuss the elements of audio production that interest you most.
Sign up for the PSW Product Showcase newsletter!

Sponsored Links

Recording Engineering & Production: The nuts and bolts of making records better, not just louder and cheaper. Some of the brightest minds from the creative and scientific world of audio discuss the elements of audio production that interest you most.Sign up for the PSW Product Showcase newsletter!

Sponsored Links

Recording Engineering & Production: The nuts and bolts of making records better, not just louder and cheaper. Some of the brightest minds from the creative and scientific world of audio discuss the elements of audio production that interest you most.
Sign up for the PSW Product Showcase newsletter!