7 sm57's compared (Unidyne III / Made in Mexico / Made in USA etc)

[MirrorProfiles]

@MirrorProfiles How do you like the current production 545SD compared to the 57?

They’re cool. Not sure there’s any difference to a standard 57 other than being cooler. You get the switch and dual impedance. Hard to pin down 545 vs 57 because they all vary. Just have to kiss a few frogs to find the ones you like.

Also, would you say in your experience that preamp input impedance affects the 57/545?

Oh it affects a 57 quite substantially. I remember reading Glenn Fricker’s guitar cab micing guide on the sneap forum YEARS ago (well before Youtube) where he was adamant about 300 ohms sounding better. Took me a while to realise I way prefer 1200 ohms most of the time. 300 sounds stiffer and less open. Sometimes it’s cool, but to me it just sounds like a mic that is trying to work but something is restricting it. It’s a fun tonal tweak if your preamp allows it.

Neve preamps change in impedance depending on how many gain stages are in use, so it can be anything from 300, 600 or 1200 ohms depending on how it’s set. My Chandler TG-2 is probably my favourite preamp, and is selectable between 300 and 1200 Ω. Focusrite ISA has 4 different impedances. I think API is typically 1000 or 1200 IIRC.

I’ll do a shoutout if you like (I may even have some files handy).

 

[James Freeman]

Oh it affects a 57 quite substantially.
I’ll do a shootout if you like (I may even have some files handy).

Really?

I've tried a 500ohm dongle with my SM57 but aside form a slight volume drop there was no difference in frequency response.
Maybe a mic preamp with an input transformer does something else?

I've been using Focusrite interfaces for almost 2 decades, so I've only worked with flat uncolored clinical preamps.

 

[MirrorProfiles]

Bought another Unidyne III 545 this week, underestimating how difficult it is to find Amphenol 4 pin connectors these days. The only sane thing to do is buy one more mic that includes a cable with it, right?

@James Freeman



Here's a comparison of the TG-2 and 1073 at 1200 Ω vs 300 Ω with an sm57.

I adjusted volume by ear so it might not be 100% perfectly levelled. 1200 Ω sounds more open and quick. 300 a little boxier and stiff.

 

[MirrorProfiles]

Speaking of preamps, these are such an insane deal for 8 channels. They're much better sounding than you might imagine. Nicer sounding than interface preamps for sure. Fredrik Nordstrom loves these too, if that counts for anything. Plenty on eBay for £300 or so.

Pardon our interruption...

 

[AlbertA]

Speaking of preamps, these are such an insane deal for 8 channels. They're much better sounding than you might imagine. Nicer sounding than interface preamps for sure. Fredrik Nordstrom loves these too, if that counts for anything. Plenty on eBay for £300 or so.

Pardon our interruption...

Are those ADAT?

 

[MirrorProfiles]

Are those ADAT?

Nah, just straight analog preamps. IIRC there were designed by some well known designer. They do have MIDI which can allow Pro Tools to control them remotely although USB would have been so much more convenient.

I’ll try and do a comparison against a few other preamps.

 

[MirrorProfiles]

A 57 broke on a drum session last year, saw some more Unidyne III’s come up at reasonable prices (and was the easiest way of getting hold of Amphenol connectors) so 3 more are here. Need to test them out still, but it’s quite interesting that one has a different/textured finish. I believe in the mid 70’s they changed to a smoother shiny finish

 

[James Freeman]

I wonder how those early 70s Unidyne III's sound compared to the modern SM57.
There are many comparisons on youtube and all make it clear to me that the Unidyne III is pretty much the same since it was released in 1959 within production tolerances.

 

[James Freeman]

Got two new production Shure 545SD mics.

It's just a modern SM57 in a different body.
And that's why I claim that the SM57 is the most consistent mic in history.

EDIT:
The two 545 are 2026 Made in China from Thomann (Europe).
The two SM57 are from 2022 and 2026 Made in Mexico from Amazon (US).

 

[MirrorProfiles]

just doing some preliminary testing before testing these new (old) Unidyne III's.

Using the Uberschall and Mesa 2002 cab. Chandler TG-2 preamp into RME ADI-2 PRO FS R BE A/D.

doing both 300 and 1200 ohms which is quite interesting to hear again. Presumably pushing the 300 button in is switching TO 300 ohms from 1200. Is it correct for 300 ohms to sound about 3dB louder?

Is there anything anyone in particular wants to hear?

I know JF wants to hear pink noise with a solid state preamp but I dont have a suitable SS amp at the moment (and for now I'd rather reamp amp tones).

 

[James Freeman]

Is it correct for 300 ohms to sound about 3dB louder?

300 ohm preamp load should sound quieter than 1200.
The mics impedance forms a voltage divider with the preamp load.

Assuming a Neve preamp:
250ohm (SM57 capsule impedance) into 300 will be -3.6dB quieter than 250 into 1200., and even quiter still if preamp input impedance is higher than 1200. ie the higher the load impedance the louder the dynamic mic will be.

As a side note, in my experience a 300ohm preamp load (flat resistive) does not make the SM57 sound any different, just quieter.
Maybe there is something special about transformer coupled impedance taps in the never preamp other than just resistive load.

Is there anything anyone in particular wants to hear?

The comparison video you did was very well made, same format will be great.
Just include words like 'vintage' 'unidyne iii' in the title and/or description to get more views, people are searching for these specific words.
Oh and plenty of images of these historic mics in the video to captivate the audience.

 

[MirrorProfiles]

Assuming a Neve preamp:
250ohm (SM57 capsule impedance) into 300 will be -3.6dB quieter than 250 into 1200., and even quiter still if preamp input impedance is higher than 1200. ie the higher the load impedance the louder the dynamic mic will be.

It’s a Chandler TG-2, I believe it’s an old EMI design. I guess the button behaviour must be flipped as 3.6dB was exactly where I landed when level matching by ear.

I can hear (and see) a very slight difference in the top end between the two impedance settings.

I’ll get on it this week

 

[bikescene]

I get a volume boost when I use the lower impedance on my Neve-style preamps. The lower impedance historically was aiming for maximum power transfer by closely matching the output impedance of the mic to the input impedance of the preamp. Although it’s been many years since I’ve gone through that academically, so I could be misquoting the concept.

I’ve made IRs with the hi and low impedance switches on my preamps. Even when normalized, there is a tonal difference to my ears. I’ll need to dig them out, but I know I did the experiment a few years ago.

Edit. I should mention that Neve circuits use input transformers, and not resistors, to load the mics to avoid confusion.

 

[MirrorProfiles]

I get a volume boost when I use the lower impedance on my Neve-style preamps. The lower impedance historically was aiming for maximum power transfer by closely matching the output impedance of the mic to the input impedance of the preamp. Although it’s been many years since I’ve gone through that academically, so I could be misquoting the concept.

I’ve made IRs with the hi and low impedance switches on my preamps. Even when normalized, there is a tonal difference to my ears. I’ll need to dig them out, but I know I did the experiment a few years ago.

Edit. I should mention that Neve circuits use input transformers, and not resistors, to load the mics to avoid confusion.

This totally matches what Im experiencing here (TG-2 has transformers too). Absolutely hearing a difference between the different impedance mode. I've done other comparisons on preamps with far more options than just 300 and 1200 and they change the tone slightly

 

[MirrorProfiles]

Audio here, just from the 3 Amphenol connector mics. The one labelled "Shiny" to me isn't sounding so great. The other 2 are rad though. I'll try and compare against my other Unidyne III 545's and 57's, it's just a bit boring to do them all at both impedances. I lowered the 300 Ω ones by 3.6dB but haven't adjusted any other levels (so tolerances between mics may vary a bit).

Link to download files:

6 files - 145.08 MB

Files sent via Smash, a fast, secure and responsible service for sending (super) large files.

fromsmash.com

Link to stream:

https://samply.app/p/KzuZvsMo4ov8Udl6SURR?si=J0UMGf38XHOuODMXmQKCeM3zX2d2

Think I prefer the Green one at 300 ohms and the sticky one at 1200. Hard to pick between those two, there's aspects I like about each other(and some small normal 57 things I dislike that are different between them).

 

[James Freeman]

I get a volume boost when I use the lower impedance on my Neve-style preamps.

Ah, now I see.
Due to being transformer coupled, the 300 tap (which connects the two coils in parallel) produces a higher voltage at the secondary (preamp side) of the transformer compared to the 1200 tap (coils in series), so that's either 1:2 or 1:4 voltage turn ratio which is +6db on the 300ohm tap, but since the lower impedance presented to the mic forms a higher voltage divider we don't get the full +6dB.
So it's not like pure resistive loads.

Neve 1073 Input Transformer for reference.

 

[James Freeman]

Audio here, just from the 3 Amphenol connector mics. The one labelled "Shiny" to me isn't sounding so great. The other 2 are rad though. I'll try and compare against my other Unidyne III 545's and 57's, it's just a bit boring to do them all at both impedances. I lowered the 300 Ω ones by 3.6dB but haven't adjusted any other levels (so tolerances between mics may vary a bit).

Link to download files:

6 files - 145.08 MB

Files sent via Smash, a fast, secure and responsible service for sending (super) large files.

fromsmash.com

Link to stream:

https://samply.app/p/KzuZvsMo4ov8Udl6SURR?si=J0UMGf38XHOuODMXmQKCeM3zX2d2

Think I prefer the Green one at 300 ohms and the sticky one at 1200. Hard to pick between those two, there's aspects I like about each other(and some small normal 57 things I dislike that are different between them).

I prefer the Sticky. I can't hear much difference between 300 and 1200 on any of them.

 

[Deadpan]

Audio here, just from the 3 Amphenol connector mics. The one labelled "Shiny" to me isn't sounding so great. The other 2 are rad though. I'll try and compare against my other Unidyne III 545's and 57's, it's just a bit boring to do them all at both impedances. I lowered the 300 Ω ones by 3.6dB but haven't adjusted any other levels (so tolerances between mics may vary a bit).

Link to download files:

6 files - 145.08 MB

Files sent via Smash, a fast, secure and responsible service for sending (super) large files.

fromsmash.com

Link to stream:

https://samply.app/p/KzuZvsMo4ov8Udl6SURR?si=J0UMGf38XHOuODMXmQKCeM3zX2d2

Think I prefer the Green one at 300 ohms and the sticky one at 1200. Hard to pick between those two, there's aspects I like about each other(and some small normal 57 things I dislike that are different between them).

I prefer the first clip.

The differences are interesting. Not miles away but definitely there.

Shiny does sound very off.

 

[bikescene]

@James Freeman That schematic does explain the difference in level quite a bit better.

I had a little time during my break to record a few sweeps of a SM57 on a V30 in my Mesa 4x12, 1" (~2.5cm) from the cap center against the grille. I left the SM57 in the same spot the entire time.
https://drive.google.com/drive/folders/1wt6ZEtJ2jIg8iCB8ky6h-SOXCsUg-sVm?usp=sharing

3 types of audio files:
-Sine sweeps 300ohm vs 1200 settings on my Stam SA-73 (more faithful clone) and Chameleon Labs 7603 (more Neve-inspired, not straight clone) preamps
-Normalized IRs of these sweeps
-Raw IRs of these sweeps, to compare volume difference between 300 vs 1200 ohms

You can flip through the IRs and get a feel for the difference in IR format.

Stam SA-73 Normalized - 300ohm (red) vs 1200ohm (green)

Chameleon Labs 7603 Normalized - 300ohm (blue) vs 1200ohm (orange)

What I see from the graphs is that the 300 ohm sweeps, normalized, have slightly less (0.5dB-1dB) in the 100-400 range. I thought that was surprising. I always thought the 300ohm setting sounded thicker, like in the clips that @MirrorProfiles shared. My sweeps do show less high end info, normalized, above 10kHz with the 300 ohm setting. The slight dip in high end is consistent with what I hear.

 

[MirrorProfiles]

I can't hear much difference between 300 and 1200 on any of them.

It’s subtle but 300 Ω pretty consistently has less top end, and the bottom end sounds more stuff.

My ISA preamp has 4 different impedance settings, maybe tomorrow I’ll do a pass with that. I can also do Neve and API, as well as Avid and stock RME preamps