rosa Posted September 29, 2016 Report Share Posted September 29, 2016 From what I understand, 2 cardiod capsules, back to back, and out of phase, create a figure 8 pattern. If this is correct, which way is front and back of the created figure 8? Looking at the graphs I would think the sides of the cardiods are now front and back of the figure 8, and the two fronts of both cardiods, being out of phase, cancel each other out. Is this correct? Quote Link to comment Share on other sites More sharing options...
pkautzsch Posted September 29, 2016 Report Share Posted September 29, 2016 It's exactly the other way round. The cardioids' fronts make up the front and rear lobe of the fig-8, and the sides of the cardioids cancel each other out. Sound that hits both cardioids from 90° is equally loud in both, but one of them has polarity reversed and thus the sound will cancel itself out. Mixing the two cardioids at different levels enables you to continuously vary the pattern from cardioid to fig-8 - or from cardioid to omni if you don't reverse one cardioid's polarity. This is how the MKH 800 TWIN basically works. Switchable (dual-diaphragm) multipattern mics, like TLM 170, create their patterns not by mixing the signals in different ways, but by different polarization voltages for each diaphragm. Quote Link to comment Share on other sites More sharing options...
rosa Posted September 29, 2016 Author Report Share Posted September 29, 2016 Thanks, and a cardiod pattern itself is created by mixing omni and figure 8, correct? So in the case you mention, how are the two cardiods created to start with? Is it Physically or electronically? Quote Link to comment Share on other sites More sharing options...
pkautzsch Posted September 30, 2016 Report Share Posted September 30, 2016 You *can* create a cardioid that way, yes. The more common way, however, is to have one capsule that has an acoustic "delay line" built in a way that sound from the front hits the diaphragm's rear later than its front (large pressure gradient --> large diaphragm motion), and sound from behind reaches both sides at the same time and with same polarity (no pressure gradient --> no diaphragm motion - same as 90° on a fig-8) Without the acoustic delay line you'd get a fig-8, with a closed back you get an omni. Quote Link to comment Share on other sites More sharing options...
James Bull Posted September 30, 2016 Report Share Posted September 30, 2016 Theres a great book about this, freely available from Neumann: http://www.neumann.com/downloadmanager/d.php?sid=lj4q1ljbge3a92anuc35pl5c24&download=docu0002.PDF Quote Link to comment Share on other sites More sharing options...
rosa Posted September 30, 2016 Author Report Share Posted September 30, 2016 Yes, I was reading parts of it earlier today. Thanks to both for all the information. What I don't get is why certain microphones use two cardioids for figure 8 rather than a single capsule without the delay line? I am sure there is a good reason for it. Quote Link to comment Share on other sites More sharing options...
ivanovich Posted February 10, 2017 Report Share Posted February 10, 2017 to me it seems like if i were to put two cardioids back to back i'd get an omni type feel(with proximity effect unlike omnis). i feel like the null of figure 8's are quite extreme. specially on ribbon mics. i've got a 77dx and a 44bx and you wouldn't believe how much the signal drops if you put the sound source in the null. one of my friends was telling me that radio broadcasters used this to their advantage. you'd have the person talking and reading the paper which was right by the null and you would never hear the paper sounds at all. i doubt you'd get that kind of behavior with two cardioids back to back Quote Link to comment Share on other sites More sharing options...
Mobilemike Posted May 26, 2017 Report Share Posted May 26, 2017 On 2/9/2017 at 9:48 PM, ivanovich said: to me it seems like if i were to put two cardioids back to back i'd get an omni type feel(with proximity effect unlike omnis). i feel like the null of figure 8's are quite extreme. specially on ribbon mics. i've got a 77dx and a 44bx and you wouldn't believe how much the signal drops if you put the sound source in the null. one of my friends was telling me that radio broadcasters used this to their advantage. you'd have the person talking and reading the paper which was right by the null and you would never hear the paper sounds at all. i doubt you'd get that kind of behavior with two cardioids back to back You're correct if you simply put two cardioids back to back. As the original post stated though, flipping the phase on one of the cards (the "rear" mic) is what gives the figure-8 pattern as opposed to an Omni-like pattern. The coincidence of the diaphragms also determines how accurate the pattern is. That's why single diaphragm figure-8 mics like the MKH30 are so highly regarded. Ribbon mics also use a single element for both sides of the pattern, hence the deep null. Simply putting two cardioid mics back to back will never get the diaphragms close enough to give an accurate figure-8 pattern. -Mike Quote Link to comment Share on other sites More sharing options...
mikewest Posted May 30, 2017 Report Share Posted May 30, 2017 What would you use a figure 8 for?? mike Quote Link to comment Share on other sites More sharing options...
soundmanjohn Posted June 1, 2017 Report Share Posted June 1, 2017 Well, M/S, for a start, but I find them useful in many circumstances because of the side null. In tight spaces in orchestra pits, for example, or in odd acoustics to minimise reflections from side walls. John Quote Link to comment Share on other sites More sharing options...
tourtelot Posted June 6, 2017 Report Share Posted June 6, 2017 On 6/1/2017 at 6:30 AM, soundmanjohn said: In tight spaces in orchestra pits, for example, or in odd acoustics to minimize reflections from side walls. John This is a very under-used function of a figure-of-eight mic. Good reminder! D. Quote Link to comment Share on other sites More sharing options...
jhharvest Posted June 6, 2017 Report Share Posted June 6, 2017 Continuing with the music applications: I typically use 2 figure of 8s for singing guitarists. You can have two almost perfectly clean tracks with very low footprint in the picture when you use the nulls to your advantage. Quote Link to comment Share on other sites More sharing options...
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