Members daklander Posted December 16, 2006 Members Share Posted December 16, 2006 I had this weird thought the other day. Yeah, it's normal for me to have weird thoughts... How close would a person come to a real Blumlein Pair setup using four cardiod mics set up do their patterns resemble the figure 8 patterns of the normal Blumein setup? Link to comment Share on other sites More sharing options...
Members mobobog Posted December 16, 2006 Members Share Posted December 16, 2006 Well you are not alone in that thought... I have had that thought about using my 2 3035 and 1 2020 to m/s stereo miking. I havent tried it because i dont have any ms decoding unit, i know you can make your own cable etc, but with that arragment i wouldnt know how to do it... Link to comment Share on other sites More sharing options...
Members philbo Posted December 16, 2006 Members Share Posted December 16, 2006 I suppose if you wanted to be technically correct, you should invert the phase of each of the mics pointing away from the sound source before mixing it with those pointing towards. The only other quibble would be things like diffraction around the extra mic bodies... but that's on the verge of getting too anal about it. Link to comment Share on other sites More sharing options...
Members Not Serial Posted December 16, 2006 Members Share Posted December 16, 2006 it would not work. two cardioids back to back do not make a figure 8, even if you could somehow coincide the diaphragms - which you cannot. for an inexpensive blumlein, use two cad m179's for $400/pair. i have these and i like the sound of the blumlein better than when i use a pair of 414's. otherwise, use the two cardioids in a coincident or near coincident pair. look closely at a figure 8 pattern - it is not exactly the shape two cardioids would make (assuming it could be succesfully done). Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted December 16, 2006 Share Posted December 16, 2006 look closely at a figure 8 pattern - it is not exactly the shape two cardioids would make (assuming it could be succesfully done). The side null points are far more effective on a bi-directional microphone than two cardioids back to back would be. Two cardioids back to back is far closer to an omni than it is to a figure 8. The four cardioids, with the rear ones phase reversed, might be interesting, but it wouldn't be Blumlein. I'd stick to XY or ORTF with a pair of them instead, or look for a good bi-directional for M-S, or two for real Blumlein. Link to comment Share on other sites More sharing options...
Members Martin Kantola Posted December 16, 2006 Members Share Posted December 16, 2006 Hmmm, you're saying that two cardioids back to back will not make a figure eight... Yet the double-diaphragm capsule invented by Braunm Link to comment Share on other sites More sharing options...
Phil O'Keefe Posted December 17, 2006 Share Posted December 17, 2006 you're saying that two cardioids back to back will not make a figure eight... Yet the double-diaphragm capsule invented by Braunm Link to comment Share on other sites More sharing options...
Members daklander Posted December 17, 2006 Author Members Share Posted December 17, 2006 Well, I didn't figure it would be exactly the same, but a somewhat similar result, going solely by the patterns. I do know that there would be some overlap on the back side of the cardiods but....Now, throw in another pattern, a hyper-cardoid. Even with the rear pickup area I'm thinking it may work better because the base/main pattern is more akin to half a figure 8 pattern and I would think the opposing mic's main pattern would cover that rear bulb of the hyper.Hmmmm. Anyway, I have an idea to give the idea a shot this coming week. Link to comment Share on other sites More sharing options...
Members Martin Kantola Posted December 17, 2006 Members Share Posted December 17, 2006 Originally posted by Phil O'Keefe ... but if you're using two seperate microphones, the positioning of the capsules is going to be far different, and I submit that the frequency and phase relationships are going to be substantially different than if you had two diaphragms, with a shared backplate, built into the same capsule. (...) The distance between the capsules and the resulting arrival time and phase and frequency differences being my primary concerns. Couldn't agree more! But this is almost exactly what the Soundfield is trying to do, and with some success too. It works, but how does it sound? Martin Link to comment Share on other sites More sharing options...
Members Martin Kantola Posted December 17, 2006 Members Share Posted December 17, 2006 Originally posted by daklander Well, I didn't figure it would be exactly the same, but a somewhat similar result, going solely by the patterns. I do know that there would be some overlap on the back side of the cardiods but.... Forget the hypercardioid because if you think about it, that "back side overlap" you just described so well is exactly what gives the resulting figure eight its (90 degree) side rejection when you sum the cardioids with different polarity! Full cancellation. You've got it! And it will work, but with the limitations described by Phil above. Please let us know how your experiment sounded! And don't forget that Blumlein is crossed pairs. Martin Link to comment Share on other sites More sharing options...
CMS Author MikeRivers Posted December 17, 2006 CMS Author Share Posted December 17, 2006 Originally posted by daklander How close would a person come to a real Blumlein Pair setup using four cardiod mics set up do their patterns resemble the figure 8 patterns of the normal Blumein setup? You actually can put a number on "how close" but I don't know how to do it, and I don't have all the information anyway, but there is a mathematical definition of a perfect bi-directional mic. Given the appropriate measurement equipment, you could measure the mic you made and compare it to the standard. However, I think what you really want to know is whether you can use cardioid mics that you own to record using the classic Blumlein setup. You can certainly approximate it. Two cardioids pointing in opposite directions and subtracted (summed with the polarity of one reversed) make a bi-directional mic. How close it comes to the ideal depends on how accurate the directivity patterns of the mics you're using are, and how close to coincident they are relative to the distance to the sound source you're recording. For mics that you might have lying around the house like SM57s or MXL 603s, neither is terribly good. You'll get a partial null, but not a very good null. But if you look at real patterns of real mics (not what's in the marketing literature), you'll find that even higher priced dual-diaphragm condenser have figure-8 patterns that only approximate the ideal, yet still people manage to make some pretty decent "Blumlein" recordings with a pair of U87s. And many single-point stereo mics are actually M-S setups made from three cardioid capsules, two back-to-back cardioids and one facing forward, so that's three quarters of your Blumlein pair. The difference between those and what you might cobble together is that the manufacturer can do a better job of making the mics coincident because he isn't dealing with big clumsy things like cases. If you set things up carefully, you can probably get a different result than if you were recording using the X-Y setup, and that would be interesting. If you want to try it, I'd suggest recording four channels. Build up a rig that holds all four mics solidly (I'd recommend stacking them with a vertical line going through all of the diaphragms) and record their outputs separately. You can listen to each crossed pair as a stereo X-Y pair to give you an idea of the direct and ambient sound. This will help you to place the rig. Then in "post" you can invert the polarity of opposite mics, sum them, and see what you get. You'll always have the X-Y combination as a reference, and as a backup. I say go for it. You may not discover nirvana, but you can have a lot of fun and maybe learn something in the process. Submit your term paper by the end of May if you want to get credit for the course. Link to comment Share on other sites More sharing options...
Members daklander Posted December 17, 2006 Author Members Share Posted December 17, 2006 Originally posted by MikeRivers Build up a rig that holds all four mics solidly (I'd recommend stacking them with a vertical line going through all of the diaphragms) and record their outputs separately. That is essentially the layout I envisioned trying. Link to comment Share on other sites More sharing options...
Members Not Serial Posted December 17, 2006 Members Share Posted December 17, 2006 why go to this much trouble? there are plenty of coincident patterns that utilize cardioids quite well, even some near coincident patterns. if you really want to have some fun, build a jecklin disc. it works better with omni's, but there are situations i use cardioids on the disc. its pretty easy. get some high density 1" foam (truck cab insulations works best) and glue it to both sides of MDF cut into the shape of a record. your application of mic hardware is unique to your mics, i made my own setup to utilize KM series neumanns. the sound of this disc is amazing; we often have "pattern battles" here where we setup every pattern we can in front of an ensemble, the disc almost always wins -with blumlein and M/S coming up close. X/Y never wins, nor does ORTF or AB. on a side note, while the term blumlein implies a specific pattern now, who do you suppose actually invented M/S and more interestly, originally patented the baffled pair (jecklin disc)? these patterns could just as accuratley be labeled "Blumlein". i'll give you a hint: it was not Fletcher. Link to comment Share on other sites More sharing options...
Members daklander Posted December 18, 2006 Author Members Share Posted December 18, 2006 Originally posted by Coaster why go to this much trouble? there are plenty of coincident patterns that utilize cardioids quite well, even some near coincident patterns.if you really want to have some fun, build a jecklin disc. it works better with omni's, but there are situations i use cardioids on the disc. its pretty easy. Why? Just because. It's just an idea that came to me and I want to see how it works, if it does, and why, if it doesn't. As far as the Jecklin disk, I have the plans around here somewhere and it's been another project I want to do, just have't gotten around to it yet.I have a pair of old EV omnis dynamics that I want to try, a pair of cardiod dynamics and a pair of condenser hand helds as well. By the way, Here's one of the best Mic Info sites I've seen. Link to comment Share on other sites More sharing options...
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