Is it a fallacy that dynamic microphones are better at rejecting room sound? - Page 1
Forum section: electronics / general

author: sfs1
author_rank: Contributor
timestamp: March 08, 2021, 10:55:02 am
content: I'm not having much luck with this question in music production circles, it very quickly goes into personal experience and received wisdom.It's commonly said that a dynamic microphone is better at rejecting background noise / room sound / reflections compared to a condenser microphone. I don't understand why this should be the case. When I look at the polar response graphs for different mics, I don't see any pattern that would let me determine that I'm looking at a condenser mic or a dynamic. They're just all over the place (you can get a shotgun condenser and an omni dynamic for example). So if the polar response isn't characteristic, what else could make a difference? Maybe it's just that there are lots of dynamic mics that have a tight polar response and lots of condenser mics that have a wider response, so when you look at a typical mic cabinet in a studio, that rule of thumb holds. But people (and manufacturers) talk about it as if it was an intrinsic thing. I'm interested to find out if I missed anything or got anything wrong.

author: dmills
author_rank: Super Contributor
timestamp: March 08, 2021, 03:47:10 pm
content: There is nothing intrinsic about either technology that impacts this, and contrary to popular belief in music circles the ONLY thing the mass of the diaphragm impacts is sensitivity.What I think may be going on is that a condenser is often really a large diaphragm condenser and those (because the diameter is greater then the wavelength at high frequency) tend to have significant side lobes in the response at high frequency, thus making them more prone to pick up reflections from a badly behaved room.Narrower patterns do of course pick up less room, and those are often (but not always) condenser designs.

author: JohnnyMalaria
author_rank: Super Contributor
timestamp: March 08, 2021, 03:59:50 pm
content: I suspect it's because, for many cases, a particular dynamic microphone is chosen because it is cardioid (e.g., Shure SM57). Hence, many people would simply associate the two and claim a dynamic mic is better for rejecting room sound.

author: TimFox
author_rank: Super Contributor
timestamp: March 08, 2021, 04:33:39 pm
content: The basic sensitivity patterns are omnidirectional and figure-8. The latter is the default pattern for a ribbon microphone, where both sides of the ribbon diaphragm are exposed to sound, and the voltage from one side is inverted in polarity from the voltage from the other side.Summing these responses with appropriate weighting produces the "cardioid" directional pattern (heart-shaped) and its variations. Some microphones (including condensers) incorporate electrical switching to set the response to omni, figure-8, or cardioid.Cardioid is the usual choice when response to sound from one direction needs to be attenuated, for example when acoustic feedback in sound-reinforcement systems is a problem.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 08, 2021, 06:32:00 pm
content: Quote from: JohnnyMalaria on March 08, 2021, 03:59:50 pmWell. Yeah. This point is certainly a major factor.Another, more objective one, is that condenser microphones tend to be more sensitive than dynamic ones. One side-effect of this, is that you tend to get a dynamic microphone closer to the sound source - which in turn will tend to get you a better signal-to-noise ratio. But this approach doesn't necessarily work well for recording everything. So, as always, the right tool for the job.

author: mansaxel
author_rank: Super Contributor
timestamp: March 18, 2021, 11:56:54 am
content: It is not the case.per se. I would suspect that it is more about the perception of what a typical microphone of either kind is; whereThe dynamic often is a close-talk affair with suitable sensitivity and a pronounced directivity with resulting compromises in off-axis frequency response and proximity effect (SM58 type of crap-turned-legend)The condenser is a "overhead mike" type of thing, with a slightly wider pickup pattern resulting in less proximity effect, higher output level (there's a buffer amp in it, for starters) and better off-axis response (Neumann KM84 style)You can do it the other way around, by tuning the output level, adopting the directivity, dealing with the proximity effect results, and you'll end up with the MD21 and the AKG C5900. The MD21 is a Druckempfänger, ie. non-directional, has no proximity effect, hears the room, and isvery dynamic. The C5900 has adopted output level, tighter directivity, some proximity effect, and works very well hand-held and is if not a true condenser at least a good electret.Good engineering can do both, and good microphone designers can make either work. The rest is opinion.My opinion is that average condensers often outperform the average dynamic in ways that will transform sound reproduction. Favourite example is guitar amplifiers. I would recommend anyone trying to get the sound of a guitar amp into an electrical current to try a large diaphragm condenser (It's quite sufficient with a china clone!), on-axis, instead of that "angle a SM57 at the edge of that Celestion and whack the console EQ" thing people have been failing at since the dawn of time.And, I strongly dislike the SM58.

author: VintageTest
author_rank: Newbie
timestamp: March 22, 2021, 03:38:29 pm
content: What Tim Fox has just said is completely true regarding polar responses of microphones. In addition, you must considersensitivityandfrequency response, as this will impact the use to which the microphone is put. The gold standard live vocal mic has been the Shure SM58 for a few decades, but unlikely to be used in a studio for the same purpose. Those that can afford it will use Neumann U87's, Electrovoice RE20's or the like, with AKG 414's or 451's being popular for drum kit overheads, AKG D12 for kick drum, Shure SM57 for guitar cabs etc. I'm old, so my reference was "techniques of the Sound Studio" by Alec Nisbett, but it was published in the late 70's, so there's probably a lot more current info available today.Good luck,Mel

author: themadhippy
author_rank: Super Contributor
timestamp: March 22, 2021, 04:01:46 pm
content: QuoteAnd then try a shure ksm313, youll never go back to condensers let alone 56/57s or 609's.

author: SiliconWizard
author_rank: Super Contributor
timestamp: March 22, 2021, 06:07:22 pm
content: Quote from: themadhippy on March 22, 2021, 04:01:46 pmIt's a ribbon microphone right? Pretty expensive stuff. It's 13x the price of a SM57...

author: mansaxel
author_rank: Super Contributor
timestamp: March 22, 2021, 07:27:37 pm
content: Quote from: themadhippy on March 22, 2021, 04:01:46 pmActually, something along those lines was what got me thinking on how to capture the amplifier sound. I read an interview with Steve Albini at least 20 years ago, where he spoke warmly of the RCA ribbons, and also the Coles ribbons, as optimum devices for amplifier miking. He was very insistent that one puts the microphone about 25-30cm away, aiming for the center dome, trying to get the microphone ribbon/diaphragm exactly 90° to the movement axis of the cone. I started wondering whether that would not work with a large-diaphragm condenser, and of course it does.

author: Yansi
author_rank: Super Contributor
timestamp: March 22, 2021, 07:30:53 pm
content: Dave Rat to the rescue with a beautiful practical presentation.

author: Cerebus
author_rank: Super Contributor
timestamp: March 23, 2021, 12:39:13 am
content: Quote from: TimFox on March 08, 2021, 04:33:39 pmThat is slightly misleading, as most cardioid (and supercardioid and hypercardioid) mics do not do any electrical manipulation to get the polar pattern but do it by physically channelling the sound waves around the microphone capsule in a selection of interesting ways. This is one of the things that leads to all the little oddities that give different microphones their 'character'. The same principle is at work, mixing the pressure and pressure gradient responses, but it's done physically.One of the more entertaining examples, the schematic view of an Electrovoice "Variable-D" microphone from 1958, heavily engineered to have a cardioid response with low proximity effect. You can see the various paths at different frequencies (and path delays) leading to the back of the diaphragm as well as to the front.From Eargle's Microphone Book. p103

author: mansaxel
author_rank: Super Contributor
timestamp: March 23, 2021, 06:52:50 am
content: On the subject ofvariabledirectivity, it is nearly always (if intentional) done with two diaphragms that are mixed electronically with varying levels and polarities. One counter-example is the AKG C1000 which comes with an extra physical attachment that is stated to make this dull-sounding cardioid into an equally uninspiring hyper.The fixed directivity is achieved as Cerebus illustrated by channeling sound out of polarity to the back of the membrane. And, the "oddities" are indeed a lot of the character. That's my main issue with a Very Famous Vocal Mic. It's off-axis response is shit.The most common directivity modification method, though, is known as "cupping", where the hand turns a pressure gradient transducer into a pressure transducer. Having frequently done monitors for people known to perform this act of directivity vandalism, I can assure the reader that it is indeed effective, both as a pose to make the alleged talent look stupid and as a destroyer of monitor mixes.

author: Bassman59
author_rank: Super Contributor
timestamp: March 31, 2021, 04:12:55 pm
content: Quote from: mansaxel on March 18, 2021, 11:56:54 amThis is the truth!QuoteAs a long-time FOH mix guy, I agree. What's the point of using the SM57 with its presence peak on a guitar amp which by its very nature already has a presence peak? And it's made worse when the cabinet is on the floor and facing the guitarist's knees, so he dials it brighter so he hears it the way he wants. And then you get odd looks when you suggest using those nice legs Fender puts on Twins to lean them back ... "But then it's too bright!"Anyway in the early 90s I bought a pair of CAD E-100 large-diaphragm condenser mics at the NAMM show, specifically to use on guitar amp cabinets for live shows. I figured for $200 each (!) if they got broken or stolen, I wouldn't feel as bad as I would if an AKG C414EB got broken or stolen. These mics have a supercardioid pattern so the proximity effect is more pronounced than a cardioid, but the mic also has a built-in high-pass filter which mitigates that.Before using them on a show we set them up in at the studio and directly compared them to the "standard" SM57 and the results were undeniable: condenser mics on a guitar amp cabinet are the way to go. The CADs had definition and air (extended HF response) without the presence peak that is a spike in your ears. We did put up for comparison a 414EB and a U87 and those two were also as you would expect excellent, but they are not something you'd want to take on an indie rock tour.If you look at big stages these days (or when we can do shows again), you'll see that a lot of mix-people are using various condenser mics on amp cabinets -- certainly most of my touring mix friends use them instead of an SM57. I still use those E-100s, though I'm at the point where I'm considering retiring them so they don't get broken. (On a lead guitarist's amp, I use the E-100 and an EV 308, the latter being a dynamic with a larger diaphragm than a 57. For solos I punch in the 308 and it sounds different enough so the leads stand out. Old trick.)And while we are bashing the SM57, I remember my first introduction to the wonder that is the Beyerdynamic M201. I did a show at a college and the sound company that came in had a case full of them. The company owner said, "you'll love these" and suggested them for all of the drums except kick, as well as the guitar amps. And he was right. Totally excellent. I own and use two of them. The 201 is my go-to snare drum top mic. As Steve Albini says, "The Beyer 201 is what the SM57 would be, if the SM57 was a microphone."QuoteSame here.This is fun. I wanna do shows again!

author: Bassman59
author_rank: Super Contributor
timestamp: March 31, 2021, 04:21:10 pm
content: Quote from: mansaxel on March 23, 2021, 06:52:50 amIts on-axis response isn't much betterThat microphone is the "gold standard" (as someone mentioned above) because it's cheap and familiar.A recording-engineer friend has been ranting against the use of the Sennheiser MD421 on drums. Why? The off-axis response is terrible. Put one on a floor tom with the ride cymbal nearby. Listen to the 421 on the tom as the drummer plays on that ride cymbal. YEEEECCCCHHH.Quote"Can you get my voice louder in these wedges?""Sure. Just hold the microphone properly and I guarantee you'll be able to hear your voice.""But this is how I hold it.""I'm a sound mixer, not a magician."

author: H713
author_rank: Regular Contributor
timestamp: May 11, 2021, 02:49:39 am
content: IMO, the SM57 is a great mic because it sounds acceptable, doesn't cost a whole lot, and can be chucked at a concrete wall a good number of times without dying.But I agree, there are a lot of things that sound better.

author: BradC
author_rank: Super Contributor
timestamp: May 11, 2021, 03:21:45 am
content: Quote from: Bassman59 on March 31, 2021, 04:21:10 pmI always used to say "you can't polish a turd, but you can roll it in glitter".We've had all sorts of problems with our "lead guitarist", so recently I bought him a 45 degree stand for his amp and started micing it up. The only thing I had to do was threaten to break his fingers if he touched any of the knobs on the amp after soundcheck.

author: themadhippy
author_rank: Super Contributor
timestamp: May 11, 2021, 06:33:32 pm
content: Quoteso the room acoustics have changed with the punters in,the drummers battering 7 shades of shit out his kit instead of the 3 he used at sound check and the keys player has his volume pedal smashed against the floor but the guitarist just has to live with it all or get busted fingers,nice.

author: Bassman59
author_rank: Super Contributor
timestamp: May 11, 2021, 09:36:24 pm
content: Quote from: H713 on May 11, 2021, 02:49:39 amThe cap of the SM57 falls off if you look at it crosseyed.It's the SM58 which functions well as a hammer.

author: Richard Crowley
author_rank: Super Contributor
timestamp: May 12, 2021, 02:29:00 am
content: Quote from: sfs1 on March 08, 2021, 10:55:02 amAlas, those audio/music forums are populated mostly by dilettante amateurs where the "received wisdom" bounces around the echo chamber until most people just accept it.QuoteFrom an strictly scientific perspective, the major difference is sensitivity. Which is mostly the result of the passive nature of dynamic microphone where the sound wave itself must move the diaphragm (and attached voice-coil) through the magnetic field. vs. a condenser microphone which typically has a much more compliant diaphragm where the motion of the diaphragm is sensed by non-contact capacitance.The result of the lower sensitivity is that the dynamic microphone will be unable to pick up quieter sounds like ambient noise and acoustical anomalies. AND it will force the user to speak louder for an equivalent signal level. And that will further enhance the perception of the dynamic microphone being better at "rejecting background noise, etc."QuoteAs you perceive, the polar response is determined by the physical design of the microphone case, completely independent of the capsule type (dynamic vs. condenser, etc.) Certainly, there are different designs, polar patterns, sensitivity, capsule type for various applications.For example, we often use "shotgun" microphones for relatively distant pickup during cine/video production. Because of the expected low audio levels involved, these microphones virtually always are designed using condenser capsules. At the other end of the spectrum, certain microphones are designed for "close talking" in high-noise (and often rugged) environments. So the more rugged (and impervious to humidity) dynamic microphone capsules are typically used.Because condenser capsules are extremely high impedance and produce a very low signal level, they require active amplification and impedance conversion. So they require power for the active circuit. A convention using 48VDC was devised by Neumann GmbH and Norwegian Broadcasting Corporation, NRK in 1966. It was subsequently established as DIN 45596 standard.