K47 vs M7 - How different are they really?

[Melodeath00]

This is perhaps not the most appropriate place to ask this question, as it's not necessarily project-specific, but more project-general. Also, I figured I would get better/more reliable/less subjective and exaggeratd info here than Gearslutz, or somewhere else. My question is, how different are the K47 and M7 sound-wise? I know they are different designs, and different materials, but the following story is what got me thinking...

I was listening to a shootout yesterday of some nice mics on an acoustic guitar. The shootout included a U67, vintage Telefunken U47, C800G, Manley Reference Cardioid, and others. What I immediately noticed and found interesting was that the U47 and U67 sounded extremely similar. There were differences, but I would definitely call them "slight." The difference between those two mics was MUCH smaller than the difference of those two mics compared to the C800G and Manley. Those two more modern mics were much brighter. Actually, the Manley and C800G sounded pretty similar to each other, in fact. They had slightly different resonances in the mids and highs, but overall their character/tonality was pretty similar, and definitely within a "family." And it makes sense - they are both K67-type capsules in a flat circuit. However, I would say the difference between the Manley and C800G was even bigger than the difference between the U47 and U67. This seemed maybe a little odd, when you consider that the U47 and U67 use different capsule-types even.

Of course, I am not shocked the Manley and C800G sound very different than the Neumann and Telefunken. What surprised me was how similar the U67 and U47 sounded. I do not know if the U47 had an M7 or a K47, but it got me thinking. How different do a K47 and M7 sound? Is it a pretty slight difference that often gets exaggerated? Or do the K47 and M7 actually sound more different than this particular U67 and this particular U47 sound to each other?

And of course, this is pertinent because I am about to build a U47-type mic using the Beesneez K7 hybrid-ish capsule.

I hope this all makes sense, and thanks for reading!

 

[micaddict]

The vast majority of the original M7s had PVC. That alone makes an important difference. I could elaborate, but a lot has been said about that already. And there are some more, physical, differences. For in-depth discussions, your best bet is Klaus Heyne's REPforum. And Neumann's own forum has some info, too. Some posters there are the same guys BTW, as can be seen in this thread:
http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1077849858
BTW Klaus posted that in 2004. That was right before the Gefell M7 got leaner sounding, in any case in his opinion. Also, Thiersch apparently wasn't doing PVC at that point.

 

[Melodeath00]

The vast majority of the original M7s had PVC. That alone makes an important difference. I could elaborate, but a lot has been said about that already. And there are some more, physical, differences. For in-depth discussions, your best bet is Klaus Heyne's REPforum. And Neumann's own forum has some info, too. Some posters there are the same guys BTW, as can be seen in this thread:
http://www.neumann.com/forums/view.php?site=neumann&bn=neumann_archive&key=1077849858
BTW Klaus posted that in 2004. That was right before the Gefell M7 got leaner sounding, in any case in his opinion. Also, Thiersch apparently wasn't doing PVC at that point.

I know the M7 was made with PVC and glued, and replaced by the mylar K47 which was screwed on. I think they have a different through-hole pattern, but I'm not positive. Either way, I'm curious about the sound difference. I found that post by Klaus as well, but it seems as if he doesn't compare their sound characteristics, but more is saying they are both of extremely good quality, and one is not better than the other.

 

[Scrappersa]

I've had the sane question for a while. Sorry I can't contribute but I would love to see some more information on it!

 

[Rossi]

The K47 is a slightly modernized version of the M7. The hole pattern is basically the same or very similar, which is why they sound similar.

There's only one original K47/K49 capsule, the Neumann one, but there are several legit M7 versions, mainly the Neumann/Berlin one and the Microtech Gefell/Neumann (east) one. The Gefell M7 is still manufactured, the Berlin M7 was replaced by the K47/K49.

I've never heard a (post-war) Berlin M7, the one in early U47 mics, but apparently they are a bit brighter than the Gefell M7 and pre-war M7 capsules. As PVC deteriorates over time, there aren't many Berlin M7s left in original state.

Its hard to make general statements. I can only compare a Neumann U47 with a (relatively fresh Sennheiser-made) K47 and a Gefell UM92S with an M7, PVC-reskinned by Thiersch. Obviously, neither the head baskets nor the circuits are identical. The U47 sounds more hifi and open. The UM92 sounds darker, it's response is essentially flat. Subjectively, the U47 seems to have higher resolution, the UM92 (although newer by several decades) sounds more vintage. Essentially they're both very balanced.

As I said, the mics aren't identical. And of course, non-original K47 and M7 style capsules will likely sound different anyway.

 

[micaddict]

Yeah, I know this is about sound and I wasn't done, yet. 
Although the title doesn't explicitly say so, I did read the opening post. It's just that there are a couple variables here and before you know it we'll be comparing apples, oranges and possibly even more fruits.

Like I said (and as you know), first there's the PVC issue. It's poured rather than rolled, it's thicker and it's stiffens (considerably) over time rather than loosens (subtly if at all). But not all M7s, then and now, had or have it. Plus, according to Klaus, modern PVC has a different composition (he probably means the added plasticizers). All this will affect sound.

Then there are the (other) physical differences. The most apparent one being the gluing versus screwing. I believe there's a difference in diameter, too (M7 is 32 mm?). And yes, I think there's some difference regarding the through holes, or Ben Sneesby's cross breed (K7) probably wouldn't make much sense. And what about the gunmetal (bronze) in earlier capsules versus brass, with even a plastic ring (talking K47 here obviously) in later ones? Finally there's the membrane to back plate distance. Minute changes make a considerable difference and this could have varied, accidentally or deliberately over time, in the originals, as it won't be the same from maker to maker today. Ideally, I guess when comparing the sound difference between M7 and K47 you'd like to have this distance the same in both (one variable less). But was it meant to be the same?

So in short, I'd say when comparing the sound, we first have to know exactly (or very close) what we are comparing.

Perhaps a good test would be to have a late fifties (late) M7 and (early) K47 reskinned with the same material and by the same person. (Only few persons would qualify BTW).

 

[Melodeath00]

Those are all great points. Thanks for the replies! I guess my main thought was "if a U47 and U67 can sound so similar, I wonder if the M7/K47 difference is even more subtle." Obviously that is something that would need to be tested, and I don't have the opportunity. At least not until I built my alternate-tube U47 and then get a pure K47 and a pure M7 and do the test myself. I'm not sure if I will ever take the time to do that. I'm hoping to just be extremely pleased with the U47 and K7 as is.

I saw that big shootout of M7 capsules by Martin Kantola, but it's from 2008. That was before the Thiersch Blue Line was released. I don't know the history, but it may also be before the current Red Line was released, even though he had a polyester-made M7. I haven't seen a M7 vs K47 shootout.