Thanks for the post.I've never had issues with my FLEA PSU's nor my old Neumann either w multi patterns.But informative read. I did purchase an Elam251 copy yrs ago that had a rattly switch on the mic n RFI noise I never could sort out.I even tried 1958 new GE6072, then a Lear(branded GE from the seller-I shan't reveal the name for he sent another 251 w another valve but still issues)I'm thinking now had we switched to a different PSU that might've been it.Alas I find the Flea C12's n other Flea's cover everything.12's perfect on grand piano, acoustic guitars, even certain vocals.My favourite mic to sing is M49.My Son's is U47 n FET47.CheersI've been thinking about sharing this for a while now as i've never read anything about this before. Please understand that there are exceptions, and if you like using your favorite LDC in figure of eight (or omni) there is nothing wrong with that, but you might want to understand what is really going on.
I almost never use multi pattern mics. There are several things happening at the same time, so i'll try to break them down.
The first issue is something I call ''electrical polar pattern fighting the mechanical one''. The other issue is the fact that sound is picked up by two membranes spaced apart by the thickness of the backplate. So you get phasing issues.
Electrical polar pattern fighting the mechanical one.
Let's take double sided/dual membrane K67(or k47, c12) capsule as example. Now imagine only one side is active, the other is not and for all intents and purposes doesn't exist in cardioid mode. You get frequency response like this:
We are interested in the green line which is 180 degree response. Most people think of cardioids as if they reject everything coming from the rear. This couldn't be further from the truth. 180 degree response is just 5 db bellow the 0 degree response at 5K where our ears are quite sensitive. This 180 degree response is created by the sound hitting the FRONT diaphragm coming through the mechanical delay network of the capsule's backplate, and not the REAR diaphragm which is in this mode disabled.
Now imagine we activate the rear diaphragm in such manner that we form figure of eight pattern. And we do get indeed, with an ideal capsule, F8 pattern with identical responses. The sound coming from each side of the capsule is now dominated by the sound coming from both physical diaphragms. We have achieved this by applying polarization voltage, and now both diaphragms are engaged. But what happened to that green 180 degree response we had in the previous image which was created by the sound coming through the rear diaphragm and the backplate and eventually hit the front diaphragm in opposite phase? Did it disappear? Well that's the thing people don't usually think about. It is still here, masked by the electrical signal created by the rear diaphragm. It is still just -5db at 5K, and it is mixed with the electrical signal. However it is PHASE SHIFTED by the distance between the diaphragms (approximately backplate thickness)!!! Of course this is true for the sound coming from both sides, there is no front or rear diaphragm per se, the capsule is symmetrical.
The issue of two diaphragms
This is basically explained above, but to simplify it even further, by using double sided capsule you actually have two microphones facing in opposite directions, however due to the capsule nature they are always somewhat phase shifted due to diaphragm separation. If you line up two mics as close as possible for any source in front of them, why would you do it any different in this case? Ideally you wouldn't, the same principle applies. Which brings me to the point. See how simple and elegant construction of a ribbon mic is. One ribbon, symmetrical construction, the sound coming from all around is hitting the diaphragm (the ribbon) at the same time, no delay of any sorts, no backplate in between, and no ''electrical'' signal messing with the ''mechanical''.
The same really goes for omni mode, or any pattern in between.
There is also one more issue with a lot of multi pattern mics. The electrical paths from the front and back diaphragm of the capsule to the impedance converter are rarely identical. Which can make all sorts of issues, mediocre both polar and frequency responses for example. In some, quite common topologies, one side of the capsule can stay charged even though the pattern is changed, which could mean you are using some random pattern between F8 and omni without realizing, yet thinking you are in cardioid.
If I want F8 response I simply use a ribbon mic. If I want omni, I just go for omni mic which utilizes one diaphragm. There are some different, yet exotic solutions, special capsule designs that try to avoid these issues. I personally use, if I have to, dual out mics such as Townsend Labs Sphere which allow me to virtually move diaphragms closer to each other by time aligning signals. The electronic path from both sides is also identical. But again, it will never give me phase coherent signal as ribbon or omni mics.
Why you should never use multi pattern mics
- Thread starter kingkorg
- Start date
Help Support GroupDIY Audio Forum:
This came up in another forum. I think it was Martin Schneider or even Wolf himself who confirmed it was Bernhard Weingartner who designed the CK12 & C12 for AKG.
My info is a bit more direct.
The history of Calrec is that Clem Beaumont, my mike mentor, built a DRS and showed it to Bernhard when AKG used to come to the Audio Show when it was at Harrogate, Yorkshire. They became great friends and his encouragement led to the formation of Calrec and later the Soundfield Microphone and my involvement.
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I know this is completely derailing the topic, but I've reached a realization that two is just always better than one. So why should that be any different with capsules?
Only if you're trying to use a dual-diaphragm as a distance mic. And who even does that?
k brown
Well-known member
Umm - countless people, all the time . . .
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When you use a mic even at close proximity even with vocals you are dependent on how that mic rejects low end from the rear. It's not like capsule is deaf from behind if you are in front of it. This is tricky subject, could be difficult to wrap head around.
You can make anything difficult. Getting up on a mic and hearing less boom and fewer pops isn't that.
I mostly mean those who have access to SDCs.
k brown
Well-known member
Yes, same answer.
Not me, it's physics, and physics are difficult. Thankfully you can make great recordings with minimal understanding of it, and i'm sure that's the case with you.
I mean, if you're mic'ing an orchestra and you insist on using your dual-diaphragm LDC over the Schoeps, then go ahead and be that guy. No judgements here.
k brown
Well-known member
I was just answering your question - I never use them for distance micing for all the reason in the OP, and more (weight, size, visual obtrusiveness) - but a whole lotta people do.
Both of which sound more like hacks than ideal technique.
You just posted an entire white paper on something that can be summed up and observed in five minutes of fiddling around with a microphone. So point well made.
@keithricker , you joined the forum and started by asking about the difference between fet, and non fet electret. Also how to swap one electret capsule for another. Then you jumped straight into some of the most complex topics like this one, obviously not trying to learn anything, nor contribute in any way.
I hope those first questions you posted weren't just a nice way to get yourself introduced so you could go into a full trolling spree. That has happened before here, and is very easy to spot.
I hope those first questions you posted weren't just a nice way to get yourself introduced so you could go into a full trolling spree. That has happened before here, and is very easy to spot.
boys...boys...you're both pretty...
The "two is always better than one" comment I'll admit was a low-key troll if you could call it that. lol But other than that, I'm not posting click-baity titles like "NEVER use [insert whatever it is you should never use]." Pure pot-stirring. But I get it. You were pointing out that there are some disadvantages, and you did it in a fun spirit (at least I hope). So I merely pointed out in a similarly fun-spirited tone ... that your white paper mentioned at least 2 such advantages they posses. I thought we were just having fun. This is why we can't have nice things.
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Marik
Well-known member
Besides the obvious fact the "two" have different properties, for many reasons it is nearly impossible to optimize the performance of "two" to the level of a "single" cardioid only, not to mention to reach level of performance of simple and pure native patterns like ribbon fig8, or true pressure omni.
Best, M
Not arguing that, but there is the other argument for some of the side benefits of just having two capsules in cardioid mode. Which some might think defeats the point, but there are readily observable differences in proximity effect and plosive handling in close-mic'ing situations (due to difference in directionality at lower frequencies), which the white paper Kong shared elaborates on.
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