Ribbon Mic Audio Samples: before/after transformer upgrade

[Giganova]

Hi ribbon mic fans --

Up for a challenge? Below are audio files (in AIFF and WAV format) of a dual-ribbon microphone (Avant Electronics CR-14, also known as the Alcron HRM-14B, picture below) before and after I swapped the Chinese stock output transformer for a Lundahl LL2912 transformer. Keep in mind that the mic only costs about $175.- (Ebay). The Lundahl transformer costs $60.-.

Can you hear a difference?
If so, which sound do you prefer?
Which one is the stock and the Lundahl output transfomer ribbon mic?

Transformer a: AIFF | WAV
Transformer b: AIFF | WAV


Here are some technical details: to make sure that I have reproducible results, I recorded a song from CD (Seal "Get it Together") through my audio speakers. The ribbon mic was at the exact same position directly between the woofer and tweeters. Signal path: ribbon mic -> M-Audio Tampa -> M-Audio MobilePre -> Ableton Live 6 on a MacBook Pro. No eq, no compression. The only difference is the normalization as one output transfomer has 4dB less output (wanna guess which one?).

[gutsofgold]

thanks for doing this!

i'm not sure i could say one is better than the other. it's pretty obvious which one is the modified one but i still can see how the stock one would work awesome as drum overheads and or sax. the stocks a bit muffled but in a smooth way while the lundahl opens the mic up more and seems to give it a touch more depth.

i think you would have done better recording a single instrument with the mics but the tests still give an alright distinction between the two. in the end i think i would just spend more on a nicer stock ribbon mic than put any money into modifying it.

[ericzang]

I like b, more open higher end. I'm guessing that's the modded one.

[darjama]

I dunno , A felt like the bass was a lot tighter. I'm going with A as the modded mic.

[Pluto]

I say B was the modded one. Just sounded better, way more high end.

[TAVD]

Did you also try removing the perforated steel plates and screening? It makes a big difference, imo.

[Giganova]

One of the inner metal meshes has been removed. There is still one left that is glued directly onto the ribbon motor.

[alba359]

To my 53 yr. old abused drummer ears and on crappy computer speakers b seemed a little more detailed.

[1m1]

I've been curious about this mod, so I am happy to be able to compare! Thanks for doing this. B is more defined in the low end and more extended in the high end, so that's the one I'm guessing is modded. Not a great deal of difference though.

[Giganova]

The mic sounds actually much better on an actual acoustic source ... the speakers that I recorded are rather bad, but it should give you an idea what a mod can do to a ribbon mic.

Let me know when you want to know the results of which audio file corresponds to which transformer.

[cramseur]

On my crappy in ear headphone (I'm at work), the B sample had a broader range to it. More highs and lows and a broader deeper sound.

I choose B as the modded mic, and the better sounding of the two.

[jakromm]

I have a pair of oktava 52's and would definately like to hear an AB on an acoustic source, prettttttty please!

[Giganova]

Originally Posted by jakromm

I have a pair of oktava 52's and would definately like to hear an AB on an acoustic source, prettttttty please!

Since I have replaced the transformer already, I can't do an A-B with an acoustical source anymore (I am not going to swap the transformer twice again as a ribbon mic is a rather fragile thing). Sorry!

[JesseJ]

A sounds lazy and sluggish compared to B that has overall more power, the bass sounds tighter and the treble side is clearer. same overall improvement as everything modded I have heard with Lundahls...

It would have been lovely to hear an acoustic guitar or drum overheads as an example thou...

[Giganova]

Well, guys, you might be in for a surprise:

A) Lundahl transfomer
B) Chinese stock transformer

I think that the Lundahl transfomer has a much tighter bass, but the Chinese stick transformer has more high-end. Also, the Chinese stock transformer has a +3dB higher output signal, which surprised me and is critical as the ribbon mic requires a very high gain anyway.

Overall, I think that the $60.- Lundahl transformer did not give a dramatic improvement in sound to justify the costs -- if any improvement at all. So, next time you hear fairy tales about how an output transformer mod will "open up" your ribbon mic sound you know how to interpret these statements.

[CrankyRayHanky]

wow, interesting thread

[darjama]

So what do I win? ;) Kidding...

I think the Lundahl-modded mic might benefit from better preamps and converters as well. At that point you might start more out of the mic. I've got an oktava ml52 that has the lundahl mod, and it's got a lot more depth and detail after the mod. I've got 3 other ribbons (2 from the tape-op group buy, 1 a sample from a chinese factory equivalent to the smaller shiny box model), and those aren't modded except for removing one of the interior screens.

If you're living on the low end though, the difference probably isn't worth it. I'd spend the money on better preamps first.

[MichaelJoly]

In my opinion, recorded music played through a loudspeaker as a source masks the qualities a Lundahl can bring to the table .

The superiority of the Lundahl transformer would be heard in an A/B test with a single, complex acoustical source like an acoustic guitar. There are a couple of qualities to listen for 1.) better alignment of fundamentals and their harmonics (this is a time domain phenomena) and 2.) less HF distortion. It is not possible to hear these two improvements in this particular test.

On a similar note, the ability to hear how the transformer contributes to the overall sound of the mic is more apparent as acoustical resonators and filters are removed that mask transformer effects. In the Alctron HRM-14b, the surfaces of the outer perforated grille are parallel and create standing wave colorations across the high frequency spectrum. This makes it harder to hear what the Lundahl is capable of in the top end. A ribbon mic with multiple truncations of a cylindrical shape (commonly copied from the Neumann U87) will not suffer from parallel surface reflections to the same extent as the HRM-14b and will allow transformer effects to be more clearly heard.

I had two Tape Op group buy Alctron HRM-2 mics for a couple of years before experimenting carefully with the Lundahl LL-2913 on single acoustic sources. I always felt the stock transformers were fairly decent and the main issues I had with the HRM-2 were acoustical and mechanical - not electrical. But I finally got a few extra Apex 205 mics and some Lundahl transformers in-house to experiment with. There was a large enough improvement in HF output, lowered midrange distortion and better fundamental / harmonic alignment that, had I heard this modified mic a year ago I would not have acquired my Coles 4038.

I'm convinced that, like many other Swedes, there is indeed beauty in that tranny.

[Giganova]

I agree that a good source like an acoustic guitar would have been nice (I am not guitar player and don't have a player hanging around right now, so this was not an option anyway), but my method of recording a CD through speakers has some benefits:

1) The song I chose covers all frequencies (airy voice ... deep bass, and every thing in between,
2) The source is the exact same for both audio samples. They are even aligned, so you can put them both in the left/right channel of your DAW, or in two separate tracks and switch between them.

Of course I could have a better signal path -- who couldn't? Everyone can upgrade until bankruptcy, but the M-Audio Tampa delivers a rather clean signal and tons of gain (around 68dB, I think) needed for a ribbon mic. I consider getting a Blue Robbie or an AEA TRP, though.

While I was a bit disappointed by the "upgrade", I think the tighter low end is a significant improvement. The lack of output at higher frequencies can probably be eq-ed. When I record my tenor saxophone through the mic, it sounds actually very good (way better than, for example, the Rode NT2-A, AT4047, Sennheiser MD441, Neumann KM184 and Gefell M930, which are the mics I owned and tested).

Michael: I am not sure if your statement about the standing acoustical waves due to the parallel grill is valid: as opposed to most LDC designs, where the grill is much larger than the capsule, the ribbon motor covers most of the space inside the grill. I think there is not enough "empty space" inside the head of the mic for standing waves between the front and back end of the grill, but I might be wrong.

If you want, I could easily do an audio test with and without grill and post results here.

I can also post audio files of my tenor saxophones if someone is interested (the only instrument I play and record).

[Giganova]

Originally Posted by darjama

So what do I win? ;) Kidding...

Congrats -- you were the only one who said that sample A) was from the moded mic!

[MichaelJoly]

Originally Posted by Giganova

my method of recording a CD through speakers has some benefits:

1) The song I chose covers all frequencies (airy voice ... deep bass, and every thing in between,

Oh, I agree. The source you used covers a wide spectral range, so from a frequency domain standpoint the test is valid. But frequency response of the transformer is only one of the parameters that should be tested. Time domain performance and distortion are others.

Originally Posted by Giganova

Michael: I am not sure if your statement about the standing acoustical waves due to the parallel grill is valid: as opposed to most LDC designs, where the grill is much larger than the capsule, the ribbon motor covers most of the space inside the grill. I think there is not enough "empty space" inside the head of the mic for standing waves between the front and back end of the grill, but I might be wrong.

The smaller front / back dimension of the HRM-14b compared to a typical LDC means the standing waves are shorter and thus heard at a higher frequency. In fact, mics like the Nady RSM-2 or Apex 205 have "waffle plates" very close to the ribbon to create HF resonances to lift the top end - the downside is smeared transient response and dips, as well as peaks in the response.

[drBill]

Michael, good to hear you're a fellow Swede!!! Hey, how is that 205 vs 4038 comparison doing? I had the opportunity today to record a loud Fender Deluxe / Strat with your modded 205, an i5 and a U87 on the room. AWESOME!! The 205 is HUGE on guitar. Nice combo. I had a little difficulty getting the i5 & 205 in phase although they seemed aligned on the grill. I guess I'll go in and align them in PT. Looking forward to #2!!

Bill

[MichaelJoly]

I think my sentence contruction was a little awkward. I'm not a Swede, but was trying to say that I admire many designs of Swedish origin, particularly when they're female.

re: 205 / 4038 - I got the audio files back from the engineer who conducted the tests but I haven't had a chance to edit and post them yet. I may have a chance to do that later today.

[Gilliland]

Originally Posted by Giganova

Well, guys, you might be in for a surprise:

A) Lundahl transfomer
B) Chinese stock transformer

I think that the Lundahl transfomer has a much tighter bass, but the Chinese stick transformer has more high-end. Also, the Chinese stock transformer has a +3dB higher output signal, which surprised me and is critical as the ribbon mic requires a very high gain anyway.

Overall, I think that the $60.- Lundahl transformer did not give a dramatic improvement in sound to justify the costs -- if any improvement at all. So, next time you hear fairy tales about how an output transformer mod will "open up" your ribbon mic sound you know how to interpret these statements.

I've stayed out of this discussion mostly because I've just gone through a similar process and already knew the answer. I purchased two Alctron HRM10s last year (same as Nady RSM-3). This year, I bought two Lundahl transformers for them. Rather than just installing both, I put just one in, then compared the two mics. The mic with the stock transformer had a much brighter sound - not bright, by any means (these are ribbons after all) - but much more usable high end on the stock unit than the Lundahl unit. I was very surprised (and disappointed) to see this result, but it is entirely consistent with Giganova's results.

The Lundahl did seem to extend the low end somewhat, but that's not what I was hoping to achieve. And for me, it is especially disappointing in cost terms. Since I bought my HRM10s in last year's group buy, the Lundahl transformers cost almost as much as the mics themselves!

The only thing I might point out is that both of these mics (Giganova's and mine) use a fairly high impedance ribbon when compared with some of the other Alctron ribbon mics. It may be that the Lundahl transformer just isn't a good match for these particular mics. They may behave very differently in other models. Note that both the HRM10 and the HRM14 (which is Giganova's CR-14) have a 600 ohm impedance in their stock configuration. Most other Alctron mics have a 200 ohm impedance.

Incidentally, my tests were made using real acoustic instruments and with the two mics positioned closely together in the same orientation. And I also tested with the two mics in reversed positions just to make sure that the inch or so between them wasn't impacting the results.

[JesseJ]

Woah! Very interesting, good thing this was posted! I was really sure the stock was the lundahl...

..and thank you Gilliland for your input also.

- Jesse -

[darjama]

Originally Posted by Gilliland

The only thing I might point out is that both of these mics (Giganova's and mine) use a fairly high impedance ribbon when compared with some of the other Alctron ribbon mics. It may be that the Lundahl transformer just isn't a good match for these particular mics. They may behave very differently in other models. Note that both the HRM10 and the HRM14 (which is Giganova's CR-14) have a 600 ohm impedance in their stock configuration. Most other Alctron mics have a 200 ohm impedance.

Correct me if I'm wrong, but my understanding is that the differing impedance is due to a difference in transformer ratios, right?

[jonesboy]

To my ears:

Sample 'a' sounds rolls off pretty aggressively in the top end and loses any semblance of fidelity once the bass kicks in. It distorts the midrange in the presence of the bass.

Sample 'b' has better high-end and seems to maintain some detail in the midrange even once the bass is there. It sounds generally 'smoother' to me.

I guess 'b' is the modded transformer. I like it better, one way or another.

edit: read the rest of the thread. Fooled me too!

-Matt

[Gilliland]

Originally Posted by darjama

Correct me if I'm wrong, but my understanding is that the differing impedance is due to a difference in transformer ratios, right?

The impedance of the ribbon/motor is the starting point. The transformer ratio squared becomes a multiplier that determines the resulting impedance for the mic as a whole. Unfortunately, I have no idea what the ratio is in the original transformer on these mics, nor do I know the resistance of the ribbon itself, so I have no basis for making any theoretical predictions for this transformer swap. I tried it because a great many people had reported such success with it. But in this case at least, it didn't work out well.

[Ironklad Audio]

I'm convinced that, like many other Swedes, there is indeed beauty in that tranny.

rrrreally....

[Giganova]

It must be its inner beauty