Warm Audio WA-19 (AKG D-19 clone), mechanical HPF, phase issue?

[garp]

Another debate is the employment of neodymium magnets (also in dynamic microphones) in place of the good old alnico's from the past. The neodymium that appears in the music industry in the middle of the 80's, was mainly due to geopolitical aspects and the increasing price of the cobalt and nickel employed, neodymium can be produced chimicaly and doesn't require complex and expensive minning. In the sonic perspective, i never liked the modern versions of the old "classics" (421, 57, SM7, 409,441 ...) and i don't have any ribbon with modern magnets to compare. Sure that they will deliver stronger signal than the old ones but are the frequency curves and headroom the same ?

 

[abbey road d enfer]

Its definitely not like the original as far as i can tell. Neither is the AEA for that matter. The original had an extra tap off the secondary that they used as an inductor (i think they called it a reactor in the manual) where you can change the voicing of the mic (M (music) and V1, V2 (which were 2 roll offs)).

It has to be considered in the period context, where mixers didn't have EQ and HPF were separate units that had to be patched in the signal path.
However, the performance of these built-in features was very dependant on the characteristics of the preamps, which resulted in significant variability.
It's very likely that these built-in filters would not work so well with some modern preamps, particularly transformerless types that have very high impedance.

 

[sr1200]

Another debate is the employment of neodymium magnets (also in dynamic microphones) in place of the good old alnico's from the past. The neodymium that appears in the music industry in the middle of the 80's, was mainly due to geopolitical aspects and the increasing price of the cobalt and nickel employed, neodymium can be produced chimicaly and doesn't require complex and expensive minning. In the sonic perspective, i never liked the modern versions of the old "classics" (421, 57, SM7, 409,441 ...) and i don't have any ribbon with modern magnets to compare. Sure that they will deliver stronger signal than the old ones but are the frequency curves and headroom the same ?

Ill say the Royer 121 (and just about any of their other mics) sound fantastic. The high end isn't rolled off as much and still has bottom end for days. I've shot out vintage vs new and found there to be little to no difference. (did a whole thing with the SM57 and 545, new vs old, USA vs Mexico vs China. The difference was no more than picking 2 different 57s off the shelf today). AEA mics are also quite good. I dont think i've had a recording with drums without my R88 since I got it. The AEA KU5A is my go to for horns.

I was able to play with the WA44 over the weekend a bit. The proximity is unlike anything i've seen with other modern mics and behaves much the same as the original (gotta be a good 12-18" back before the proximity effect levels out). Thursday I'm grabbing an original 44BX (actually a pair) for a project, client insisted, through another studio in the area that has them. I hope to be able to do a shoot out between the two mics to see whats up.

It has to be considered in the period context, where mixers didn't have EQ and HPF were separate units that had to be patched in the signal path.
However, the performance of these built-in features was very dependant on the characteristics of the preamps, which resulted in significant variability.
It's very likely that these built-in filters would not work so well with some modern preamps, particularly transformerless types that have very high impedance.

Thats interesting. How would the filter effect the interaction between the mic and the pre? From the schematic, it looks as though the "patch" to engage the filter IS after the transformer so perhaps a heavy load messes with the filter "coil". Very interested in how that stuff works. (is a 2000 ohm load from a transformer seen differently than a non transformer 2000 ohms load?)

 

[abbey road d enfer]

How would the filter effect the interaction between the mic and the pre? From the schematic, it looks as though the "patch" to engage the filter IS after the transformer so perhaps a heavy load messes with the filter "coil". Very interested in how that stuff works.

The response of a passive filter depends on the impedance that drives it and the impedance that loads it.
A filter that sees too high a load impedance sees its response peaking around the turnover frequency.

(is a 2000 ohm load from a transformer seen differently than a non transformer 2000 ohms load?)

A 2k load from a transformer is actually quite variable with frequency.
This picture shows the different responses of a basic 1st-order HPF in 3 settings:
One (brown) with a 2k resistive load such as presented by a transformerless preamp
The second (green) where the preamp has a transformer which obeys the 10:1 bridging rule down to 20Hz (most commercial designs don't respect te rule)
The third one (red) with a most common preamp with xfmr input that obeys the 10:1 bridging rule only down to 40Hz.


Now if we take the case of a 2nd order HPF optimized for an impedance of 2k, and we connect it to a preamp with an impedance of 5k, which is not uncommon, it gives these graphs, where purple is 2k and green is 5k, we can see that the effect is not trivial.


I guess now you can understand why mic mfgrs don't want to run the risk of crossing over with electronics designers.

 

[abbey road d enfer]

Another debate is the employment of neodymium magnets (also in dynamic microphones) in place of the good old alnico's from the past. The neodymium that appears in the music industry in the middle of the 80's, was mainly due to geopolitical aspects

Not exactly. The increased difficulties in sourcing nickel and cobalt resulted in the use of ceramic magnets, mainly for loudspeakers, where the quantities are much bigger that in mics.
The increased use of rare earth magnets was fuelled by the numerous improvements resulting, in terms of level, frequency response, transient response, and manufacturing cost.
The size of magnets has always been a limiting factor in the achievable HF response, S/N ratio and consistency of directional pattern.
So, no, the frequency response and level are not the same.
As to headroom, I don't know what it is for a dynamic mic.

 

[garp]

What i call headroom is the ability of the transducer to preserve "constant" frequency response even at hi SPL, a lot of microphones like "pinch" to medium hi pitched response when in front of loud sources.

 

[Paul W]

What i call headroom is the ability of the transducer to preserve "constant" frequency response even at hi SPL, a lot of microphones like "pinch" to medium hi pitched response when in front of loud sources.

I can't parse that and don't know what you mean by "pinch."

 

[sr1200]

I think what hes getting at is at higher SPL, the frequency response changes and certain areas of the response suffer. Ive seen this kind of thing happen, but only at like RIDICULOUS levels when doing testing, never in a real world scenario. Unless you're miking jet/rocket engines, not sure when this would happen. Even at festivals, the stage volume usually isn't crazy. Of course you get that jerk that thinks that hes outdoors he can just turn his stack up to 10... thats why we have monitors buddy, turn it down.

 

[garp]

When the frequency response narrowed to a very thin band in the medium range, i call it "pinch" (sorry i am french and my terms maybe sometimes inadequate)

 

[sr1200]

The response of a passive filter depends on the impedance that drives it and the impedance that loads it.
A filter that sees too high a load impedance sees its response peaking around the turnover frequency.

A 2k load from a transformer is actually quite variable with frequency.
This picture shows the different responses of a basic 1st-order HPF in 3 settings:
One (brown) with a 2k resistive load such as presented by a transformerless preamp
The second (green) where the preamp has a transformer which obeys the 10:1 bridging rule down to 20Hz (most commercial designs don't respect te rule)
The third one (red) with a most common preamp with xfmr input that obeys the 10:1 bridging rule only down to 40Hz.
View attachment 129169

Now if we take the case of a 2nd order HPF optimized for an impedance of 2k, and we connect it to a preamp with an impedance of 5k, which is not uncommon, it gives these graphs, where purple is 2k and green is 5k, we can see that the effect is not trivial.
View attachment 129170

I guess now you can understand why mic mfgrs don't want to run the risk of crossing over with electronics designers.

Thats really cool to see thank you! First order isnt really doing any "damage" just seeing different responses on the roll off.
Second order might mess you up a bit with that bump, if you're not expecting it. Let me put the filter on, OMG its a boost! lol

 

[sr1200]

WA is SLIGHTLY larger.

After doing some tests w piano, I wouldnt be able to tell which is which without a reference. Its not a night and day difference. Same kinda vibe.

The WA is obviously higher output. (Significantly higher). The rca sounds a little more wooly (if thats even an adjective for this) in the bottom end. Top end on both are pretty comparable.

 

[ElSmurf]

After doing some tests w piano, I wouldnt be able to tell which is which without a reference. Its not a night and day difference. Same kinda vibe.

Thanks for doing the test and sharing your findings. This one is definitely on my list now.

 

[Paul W]

How on earth can Ber****ger sell an LA2A “clone” for under $400? Easy- the target audience has never worked with a real LA2A. And futher to that- they have zero technical understanding of how the unit works and where the corners get cut to deliver such a circuit for relative pennies.

Have you seen this thread over at GS?

https://gearspace.com/board/so-much-gear-so-little-time/1405126-expensive-vs-cheap-gear.html

It starts with a guy who owns a real LA2A comparing it to a Klark Teknik (Behringer) KT2A costing well under a tenth as much, and letting people judge the difference blind. The Behringer doesn't sound exactly the same, but holds its own.

It's also funny that his real LA2A costing thousands and thousands of dollars had a capacitor that wasn't soldered at all on one of the pins.

 

[Timjag]

Ok I bought 2 for work, won’t get a chance to use them till next week but what I can tell you is they extremely well made and weighty. Will show more when I have time,

 

[Paul W]

Re the Klark Teknik 2A-KT (which I incorrectly called the KT2A) , I forgot there's an older thread about it right here at GDIY (of course), started by kingkorg (also with some samples vs LA2A for comparison, naturally); it appears to be active again recently.

https://groupdiy.com/threads/klark-teknik-kt-2a.71506/