Dynamic mics - why so difficult to reproduce?

[OneRoomStudio]

Can you buy (say) an RE20 body off the shelf?

Because even if the moving coil assembly is right, it won’t sound close to correct in a different body

I think that’s what they may have meant

You may not be able to find an RE20 (yet), but you can definitely find Chinese clones of SM57s, e609s, SM7s, Beta52a's, etc.

 

[OneRoomStudio]

Maybe I need to ask a more specific question.

Sennheiser (and Chinese cloners) are clearly able to make microphones with similar housing to the MD409. What is preventing them from creating a capsule similar to the MD409? In various tests, while the e906 is closer, all the modern takes on it have a presence peak and sound/measure differently. They used to be pretty consistent, even when they launched the "Blackfire" range.

The same question could be asked about Beyerdynamic's M380, or Shure's SM5B.

 

[engineerkyle]

A blast from the past, just to tickle imagination.

A 58...
https://www.globalmediapro.com/dp/A032C4/797-Audio-CD58-Dynamic-Microphone/

Can you link to where that photo of their version of the 441 is? That link doesn’t go there.

 

[ricardo]

And that's the problem. Directivity issues with louspeaker can easily be solved by imposing a dedicated listening poit, microphones can't be sold with a warning "not to use with large sound sources or in reverberant environment"

A speaker in a room will give "good sound" in an "area". Better speaker, bigger & better area. Turning that speaker into a microphone ala Baxandall will pick up 'good sound' IN THAT AREA. The effects of reverberation will be heard on both the speaker sound and the 'microphone' sound ... as will the off axis faults.

Quite often, 1m on treble unit axis bla bla isn't the best position to listen to a speaker and such a speaker will not be a good microphone at 1m on treble unit axis either.

 

[ricardo]

samic said "in my opinion it is 10x complicated to manufacture than a K67 static capacitor capsule!"

If you believe this, you don't understand how condenser capsules work. There's nothing static about condenser capsules. And it is extremely difficult to get even the simplest capsules right. Which is why we are starting to see just recently WIDELY AVAILABLE accurate replicas of k67.

I'm not denigrating how difficult it is to do condensor capsules. IM not so HO, there are a literal handful of people today who can do good condensor capsule design from scratch and they don't do it often cos they know how difficult it is.

But I'm with samic in saying designing and making dynamic mikes is EVEN MORE DIFFICULT

 

[abbey road d enfer]

A speaker in a room will give "good sound" in an "area". Better speaker, bigger & better area. Turning that speaker into a microphone ala Baxandall will pick up 'good sound' IN THAT AREA. The effects of reverberation will be heard on both the speaker sound and the 'microphone' sound ... as will the off axis faults.

Quite often, 1m on treble unit axis bla bla isn't the best position to listen to a speaker and such a speaker will not be a good microphone at 1m on treble unit axis either.

I believe I already answered that.
When listening, you can choose speaker placement and listening position. When recording, you can't choose the position of the source, because the mic picks up everything, including room noise and reflections/reverb.
In other words, by choosing a listening position, you can improve the signal-to-garbage ratio.
Just the same, you can improve it by restricting to single (almost point) sources, which is a serious constraint.
Or alternatively an Ambisonic system.

 

[abbey road d enfer]

That doesn't really make sense. Sure, you can buy finished condenser capsules "off the shelf," but that would be the equivalent of buying a moving coil assembly off the shelf - no machinery needed in either case. If you're making condenser capsules yourself, you absolutely need the the machinery to drill the backplates, stamp/cut the spacers, cut the film for the diaphragm, etc (just ask @soliloqueen)....the same way you would need machinery to make the components of a moving coil mic.

I think what you're saying is that there are already a lot of condenser capsules and parts available to purchase? But that gets back to my original question - why so many condensers being made and so few dynamics?

I think lack of demand is the real answer, but not a very satisfying one.

I believe the problem is that you're comparing different paradigms.
There are different levels of DIY.
Buying a dynamic capsule and a ready-made body is at the same level as buying a condenser capsule, a PCB and a body.
When it comes to actually building capsules, there is a huge difference.
One can make a decent condenser capsule with minimal resources, the most costly being a lathe.
For a dynamic capsule, one needs a precision winding machine, a lathe, a precision plastic forming apparatus for the diaphragm, probably a plastic molding facilty.
In addition, a condenser capsule can be assembled with one very simple jig, for stretching the membrane. For a dynamic capsule, you need at least two, of high precision, one for gluing the voice coil to the diaphragm, one to insert and glue the diaphragm into the magnet assembly.

 

[MicMaven]

Sidebar comment: I am intrigued by the apparent "reciprocity" in all of this, i.e., using a big speaker to project sound over a big area, while it captures a big area used in reverse as a microphone. (crude, non-technical paraphrasing...)

Sidebar question: Are there similar reciprocal aspects lurking about in the weeds? Are there similar relationships in dynamic cartridges, capacitor capsules, and other stuff? Is there a law of physics working here ... or am I trying to hard this time?

(typing pensively, not intending to derail the thread ... and recalling curiosity killed the cat ... )

Happy trails - James

 

[OneRoomStudio]

I believe the problem is that you're comparing different paradigms.
There are different levels of DIY.
Buying a dynamic capsule and a ready-made body is at the same level as buying a condenser capsule, a PCB and a body.
When it comes to actually building capsules, there is a huge difference.
One can make a decent condenser capsule with minimal resources, the most costly being a lathe.
For a dynamic capsule, one needs a precision winding machine, a lathe, a precision plastic forming apparatus for the diaphragm, probably a plastic molding facilty.
In addition, a condenser capsule can be assembled with one very simple jig, for stretching the membrane. For a dynamic capsule, you need at least two, of high precision, one for gluing the voice coil to the diaphragm, one to insert and glue the diaphragm into the magnet assembly.

That’s a fair point, although there aren’t too many people truly “DIYing” condenser capsules these days either.

 

[abbey road d enfer]

Sidebar question: Are there similar reciprocal aspects lurking about in the weeds?

Yes.

Are there similar relationships in dynamic cartridges, capacitor capsules, and other stuff?

Yes. A disk cutter head is a big moving-coil cartridge driven by a power amp. An electrostatic actuator, used for example to calibrate microphones, is condenser mic driven by a voltage. A generator is an electric motor receiving mechanical energy and turning it into electricity.

Is there a law of physics working here ... or am I trying to hard this time?

The reciprocity law is everywhere in physics, often with a different name, like the Lenz law, or action/reaction.

 

[ricardo]

Sidebar question: Are there similar reciprocal aspects lurking about in the weeds? Are there similar relationships in dynamic cartridges, capacitor capsules, and other stuff? Is there a law of physics working here ... or am I trying to hard this time?

Yes. It's worth reading the Baxandall paper just to marvel in awe at a true master of Reciprocity.

The other Baxandall paper which uses Reciprocity to gain new insights into a subject is the one describing the QUAD ESL 63. That's in the AES library and may be co written with Peter Walker

IIRC, there's one on condensor microphones too.

He isn't Great Guru Baxandall for nothing