Selecting a 1:4 transformer for dynamic mics.

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abbey road d enfer

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I have different kinds of 1 to 4 transformers, and I will check them out.
The ultimate answer is when you try them out.
The sound does not get as good as a sm7, but it gets closer, IMO..

I believe the "altered 58" has no transformer, just the capsule direct. It's a quite common mod to SM57's also.
Even with my 73 yo ears, I could detect the nasty fizz from the 58; I was not foolds one second.
 

MaxDM

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The ultimate answer is when you try them out.

I believe the "altered 58" has no transformer, just the capsule direct. It's a quite common mod to SM57's also.
Even with my 73 yo ears, I could detect the nasty fizz from the 58; I was not foolds one second.
Yes, there's a resonance there, that can be eq'd out.

I think the SM7 has an eq network (notch filter) to make a dip at that freq?

Still, a much clearer sound, with more bass
 

MaxDM

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I wonder if it's a question of loading the capsule, perhaps with a 50 ohm resistor.. might try that as well.
 

abbey road d enfer

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The SM58 response is similar to the Coca Cola receipe. Two generations of SE and performers have learnt to tame it.
You may EQ its quirks (passively or actively), it won't make it a great studio mic. However, as a live mic, its longevity is a witness to its intrinsic appeal.
 

MaxDM

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Well, the mic started out as a Studio Microphone, which is where the SM prefix comes from, and there used to be low impedance versions of it, or at least dual impedance, if I recall correctly.

Actually, a lot of famous records have had vocals tracked with the SM58, handheld, as well as the SM57, in the control room.

Off the top of my head, Bono, Peter Gabriel, Paul Rodgers.
 

abbey road d enfer

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Making a Studio Microphone is easy; you just write it on the datasheet.
Making a great studio mic is much harder.
I've made a few records with a less than stellar vocal mic, because the singer felt more comfortable.
The balance between perfect technical performance and perfect talent performance often justifies it.
 

MaxDM

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Test results for the SM58:

The transformer that was found in the SM58, with a source impedance of 30 ohms circa, is flat from 20-20 KHz, with a slight dip towards the top.

The primary and secondary DC resistance of said transformer is very low, it is a 1:4 ratio. I suppose that, the low DC resistance is an indication of good power transfer?

Using 150/200 ohm 1:4 mic input transformers worked as well, into the soundcard, perhaps because of the 'easy' load. I imagine that in a transformer coupled preamp, with a step up, the original is better suited.

I also used a 60's UTC transformer, which had low impedance taps and this worked best, in terms of level, but the bass response was rolled off, and there appeared to be some interaction between the voice coil and the transformer, in terms of resonance on the top end.

So, considering that the transformer furnished with the SM58, is itself relatively flat, when presented with a constant source impedance, I am guessing that the voice coil is quite sensitive to load.

The mic sounds best, to me, with a high impedance, although for close pickup, there is an excess of bass, due to proximity effect.

Also noteworthy is the effect that the size of the cavity inside has on the mic's response in the bass. Filling the cavity with a solid or foam changes it's response and overall sound to a degree.
 

emrr

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Look at a speaker impedance curve if you haven't. That's what the voice coil is like too. That interaction with other elements is what you describe as VC load sensitivity.
 
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