A N S W E R S

My DAT deck has an unbalanced mini-headphone jack for an analogueue input. How do I get the best sound through that tiny jack -- what types of adapters would give me the best results?

The size of the jack has nothing to do with sound quality so long as it makes good contact. But they wear out soon, so avoid lots of plug-in, plug-out cycles. Make adapter cables with flexible cable rather than solid adapters that put a lot of sideways load on the little jacks. [dj]

My DAT deck has unbalanced RCA analogueue inputs -- how do I maximise sound quality?

Same answer as {32}. Plus, use a good external mic preamp. [dj]

What are the sources of mic noise?

I assume you mean hiss rather than hum or extraneous pickup caused by poor wiring. In a typical recording setup, exclusive of the A-to-D or tape, in order of decreasing loudness, the sources are mic preamp noise from its circuitry, mic noise typically from the front end FET, Brownian motion noise of the air inside the mic capsule, and thermal noise from the wire and other resistance between the mic and the preamp. [dj]

Tony Berke reports on experiments he's done with various mics re noise level, and comes to the conclusion that large capsules and omnis are quieter, but that there's no really conclusive explanation why this might be so, and why there seems to be such a disparity in specs from the various mic makers. (Sorry if I have paraphrased too crudely, Tony!)

This is a big problem, and one that until recently the mic makers have not addressed exactly openly. Like most aspects of mic design, it's also very sparsely covered in the literature. The only really cogent treatment of the subject, and this is still incomplete, is an article by Dick Burwen in the May 1977 Journal of the AES, which fortunately is reprinted in the AES anthology of microphone articles. I have seen two other relevant articles, "Microphone Thermal Agitation Noise" by Harry Olson in the Journal of the ASA, Vol. 51, No. 2; however, like most Olson work, this deals with the measured effects on a ribbon (pressure gradient) microphone rather than a condenser (predominantly pressure) mic. There is also a useful paper in the December 1970 AES Journal by Herman Wilms on the vagaries of noise measurement, "Subjective or Psophometric Audio Noise Measurement: A Review of Standards."

Noise is typically referred to in microphones in terms of equivalent sound pressure level. But there's a major catch here. The measure used is typically dBA: decibels above the hearing threshhold of 0.0002 microbar, A-weighted. But A weighting is designed to measure the annoyance factor of sounds in the normal background noise floor level -- 40 to 80 dB SPL more or less -- not things that are below the ambient noise floor in theory but are still audible and objectionable, as nearly all mic noise is. Usually, the A-weighted curve is used because the number looks the best, but, quoting from the CCIR working group, "...the A-weighting network curve...is not considered suitable for the measurement of audio-frequency noise in broadcasting and sound recording systems, as in this case it is the effect of the noise on the program rather than the loudness of the noise itself which is important." The standards by which microphone noise are measured are also not shared among the various makers. Neumann tries to cover the bases by referring to both the DIN/IEC 651 standard and the DIN 45405/CCIR 468-1 standard. But both standards ignore the effect of the capsule -- these are both just weighting curves for the equivalent SPL of the noise generated by the electronics with a replacement capacitance connected in place of the capsule. There is a DIN spec 45590 for measurement of self-noise of the entire mic, but few mic makers use this spec; it's difficult to do and the result looks too bad.

Over the last ten years, I have bought every microphone book in every European language I could find, and they all fall way short of anything really thorough on any of the important topics of mic design and comparison. The most useful is probably _Acoustics_ by Leo Beranek, now back in print as an ASA paperback. Of the popular books, the Lou Burroughs book _Microphones_ is probably the best, but long out of print (and the ^*&^$# who borrowed my copy didn't bring it back!). Careful reading of the articles in the AES anthology volume on mics taught me more than either of those, however.

The electronics of the microphone can easily be modelled, measured and improved. Nearly all condenser mics use an FET operating as a source follower, or a low gain common source stage. The FET and its source and drain resistors are typically the major noise sources. The noise current from the high value gate bias and polarisation resistors is delivered into the capacitance of the capsule; the resultant RC pole results in a lowpass filter that, with any reasonable value of resistance, puts most of the noise in the infrasonic range, where it's blocked by coupling caps, servos, etc later in the chain. Earlier mics used lower value resistors - 150 to 250 mega-ohms - while modern mics use 1 to 3 giga-ohm resistors, and Burwen uses a 20 giga-ohm resistor in his design. The cheapest electret capsules use no resistor, just a reverse-biased diode whose leakage current biases the FET (no polarisation resistor is required in an electret).

The noise from the electronics is generally white above the 1/f corner of the FET used. In modern design this is usually below 100 Hz and seldom a problem, and the resulting A-weighted noise is around 1 microvolt RMS, or -120 dBV. Unlike most mic and console makers, I don't use dBm. dBm refers to noise _power_ (it is dB ref 1 milliwatt into 600 ohms) and is only relevant when a matched transfer of power is taking place. The output impedance of a microphone is seldom, if ever, matched these days into the load impedance of the preamp which would make a power measurement meaningful. If you ask the manufacturers about this, they will shuffle their feet and say, "oh yes, we mean dB referenced to the voltage level (0.775V) that 1 milliwatt from a 600 ohm source makes across a matched 600 ohm load." Arrgh.

The bigger problem, now that we have good quiet FET's, is the noise from the capsule. Of course smaller capsules will have lower output, and the electronic noise will predominate in relative terms. But the output level at the capsule of a 1/2 inch omni and a 1.25 inch dual-cardioid like the C414 is fairly close, around 12 mV/Pa. This is so because the size of the diaphragm isn't the only contributing factor; larger diaphragms need to be stretched more tightly and are often spaced away from the backplate further than the small ones.

I have not yet seen a good explanation of the noise generation mechanism of the air behind a backplate. One of the best engineers at AKG in years past told me of an article in the Journal of the ASA about turbulent behaviour of the air between the diaphragm and the backplate but I have been unable to find it. The Burwen paper notes without comment that his omni capsule was some 10 dB quieter midband than the cardioid, and the bare electronics were 10 dB quieter than the omni. This was using a Schoeps MKT45 capsule, which is a switchable omni/cardioid. The response is switched by opening or closing vents in the capsule backplate, so diaphragm thickness, tension and spacing are unchanged.

What does change between the various capsules, and what seems to cause the major difference in _perceived_ noise floor, is the damping impedance presented to the diaphragm by the air behind it. In theory, the "thermal acoustic" noise is caused by Brownian motion of the air molecules; this is modelled as a voltage which appears across the mechanical impedance of the diaphragm. A capsule spaced very close to the backplate will be more constrained by the air cushion behind it than if you were to open the backplate up to sound arriving from the rear (as is done in cardioid mics). Close spacing also boosts the output (better for noise) but requires lower polarising voltage or higher diaphragm tension (worse). This damping impedance is also usually reactive -- therefore the tonal colour of the noise changes with capsule type. You can have two noise sources, one white and one red, measured to have identical dBA equivalent loudness, and sound very different.

What all of this comes down to is that different mics will sound noisier or quieter in use, with little direct relation to their specs which can almost be pulled out of the air. Someday, mic makers will publish noise spectral curves just like transistor and IC makers do, so that this can all be compared sensibly. Making an isolated chamber that’s _really_ quiet is on my list of things to do so that I can do this. So far only B&K has published anything relevant in this field, and then only for their measurement microphones. [dj]

How do I keep mic noise to a minimum so I can have a decent S/N ratio on quiet recordings?

Use mics that have a low self-noise, and use a quiet mic preamp. [dj]

What's the difference between the capsules in a Neuman TLM-170 and a Neuman KMi86?

Ooo, why did you choose this particular pair of mics?! The capsule in a TLM170 is essentially identical to that in the U89. It is about an inch in outside diameter, and follows the Braunmuehl-Weber design which has two diaphragms sharing a common backplate/resonator/phase shift assembly. The two diaphragms produce two cardioid signals which are added together electrically in phase or out of phase to produce the desired pattern. Sometimes this is done by taking the audio output off the common backplate and varying the polarising voltage, sometimes it's done by mixing the two separate audio signals. The other Neumann Braunmuehl-Weber capsules are the KK67 family, found in the U67, U87, SM69, and the like, and the KK47 family, used in the U47 and M49. These types all have a centre point contact, where the diaphragm is attached to a post coming out of the backplate. The TLM170/U89 capsule has no centre point, it is attached only at the circumference (like the Braunmuehl-Weber capsules made by AKG). There was also a KK56/KK88 capsule which is centre-point-less like the TLM170 but smaller. The KM86 and KM86i use a back-to-back pair of KK84 capsules, which are also found in the KM84 front-address mic. [dj]

The KMi86 (a short production run several years ago) consists of two KMi84 capsules mounted back to back, with the primary pickup direction being perpendicular to the axis of the mic body. It contains internal electronics to allow for pattern switching between omni/cardioid/figure-8.

The TLM170 is a shorter, stouter mic, with a larger diameter capsule, which is also oriented perpendicular to the mic body. The 170 is also switch selectable for omni/ subcardioid/ cardioid/ hypercardioid/ figure-8/ user-definable. The user-definable pattern feature will be offered as an electronics upgrade some time in the next year. A special power supply (phantom/pattern controller) will be required.

Having used KMi84's, KMi86's and TLM170's to master with, I think that I prefer the 86's. The 170's are nice, but the 86's have a warmer sound. That may be because the 86's I use have been pro 'tweaked' to be the best mic that they can be. [td]

What is a PZM? How do I modify one?

The following mod is affectionately referred to the ‘Rastocny’ mod. I'm still using this modified mic in a lot of situations, but I have a few others that I use when conditions are right. The problem is finding the right place and a big enough surface to use them properly. [dv]

RECORDING TIPS WITH THE PZM

About recording pianos, Crown recommends that you tape two of them inside of the lid. I place the mics in various positions depending upon the room. When recording in a large hall, I place them on the floor about five feet apart and 12' from the bend in the sound board (it's an unconventional approach; I've never seen anyone else use it). When recording in a small room, I tape them to the lid in various positions, depending upon the type of piano.

Crown has several published tips on using the PZMs. If you can find a dealer near you, they may have these articles in stock.

PZMs are wishful-sinful mics: they sound pretty good but they need to be placed against a large surface to work properly. Sometimes this is just not possible and you have to try other mics or go to extremes to find a surface. And unfortunately, PZMs have a rising top octave response :-( But they are seldom seen by the audience!

INTRODUCTION

The RS PZM microphone is an omni-directional electret microphone patterned after a principal invented by Crown International called the pressure zone microphone (hence, PZM). The output impedance of the stock microphone is about 600 ohms (unbalanced) and it requires a phantom supply voltage from -1.5V to -12V DC for operation. The stock microphone has a supply module and built-in line-matching transformer to convert 600 ohms unbalanced to about 10K ohms unbalanced. The problem with this stock PZM is twofold:

1. you cannot use long cable runs on the mic since the line is unbalanced
2. the matching transformer used in the module is terrible

So the mods outlined below address these two problems by describing a method of using a standard balanced microphone cable in conjunction with an unbalanced (single-ended) microphone input configuration common to most consumer tape recorders. There are compromises made when using this approach, but the benefits in the case of this PZM far outweigh the compromises.

MODIFYING THE RADIO SHACK PZM MICROPHONE

The stock assembly consists of a mic, a coax cable, a supply module, a twinax (2-wire shielded) cable and a 1/4" phono plug as shown next.

1. Cut off the 2-wire shielded cable between the 1/4" plug and the power supply. Toss the phono plug.
2. Take the mic apart (screws on the bottom). Unsolder the coax cable from the mic element and replace with the 2-wire cable from step #1 above. This is a somewhat static sensitive device so work with a grounded soldering station and appropriate clothing. Connect the low side to the dark colour wire and high side to the light colour wire. DO NOT CONNECT THE SHIELD TO THE LOW SIDE!
3. Connect the other end of the 2-wire cable to an in-line male XLR connector. You should now have something that looks like this:

4. Make some long mic cables from some twinax or 2-wire microphone cable. I made three 75' and three 25' cables for my setup. Shields are connected on each end to pin 1 and the case on one side (I think it's the female side) as shown next.

The next step is to build an in-line supply that also adapts the XLR connectors to the 1/4" phono mic input of most consumer tape recorders as shown next. There should be one of these supply boxes built for each mic used.

5. Cut a 24" piece of 2-wire mic cable and connect an in-line female XLR to it as you did in step 3 above.
6. Cut a 24" piece of coax and connect an in-line 1/4" male phono plug to it.
7. Cut holes large enough in a small steel project box to run the cables through. Add chaffing and strain relief to these two cables.
8. Connect the shields from the two cables AND the low side of the 2-wire mic cable to the same point (single point) on the project box. (If you prefer to use chassis mounted XLR and phono connectors, insulate these connectors from chassis ground and wire the cases internally to this same single-point ground.)
9. Connect the "+" side of a 9V transistor radio battery jack to this single point ground.
10. Connect the "-" side of this battery jack to a 2.2K ohm 1/4 watt resistor.
11. Connect the other end of the resistor above to the high side of the 2-wire cable.
12. Connect a 10 uF mylar or metalized polypropylene capacitor from the high side of the 2-wire mic cable to the centre conductor of the coax cable.

You should now have something that looks like this:

When the mics are not connected, there is no drain on the battery so there is no need for a switch.

Close up the project box and plug in the microphones and the tape recorder. I think you'll be surprised by the improvement in these otherwise inexpensive and ho-hum mics.

ONE LAST THOUGHT

If you are *ABSOLUTELY POSITIVE* that the input stage of your tape recorder or mixer has an input capacitor (of adequate voltage) and then a load resistor, you can replace the 10 uF cap with a piece of wire. (See below.)

If you decide not to or cannot replace the input stage cap with wire, you should replace the input stage caps of the tape deck or mixer with an equivalent value of equal or higher voltage mylar or metalized polypropylene capacitor to obtain the best performance.

VARIATIONS

You can eliminate any or all of the XLR connectors if you wish to make a custom length, dedicated mic setup. The reason that I suggest the XLRs is that as soon as you get serious about recording, you instantly find out that you need about 1092' more of cable than what the custom lengths are to do what you want. With the XLRs, you can add or remove cable for each situation.

For permanent installations in a mixer or tape deck, you could build a phantom supply similar to what is shown next.

You can gang the passive RC components together to run several channels from the same bridge. You could also put all of this inside of a "Bud" box. I recommend using all similar value components since parts are cheaper by the dozen.

This concept provides more than adequate ripple rejection and if you want a bit improved high frequency clarity, shunt all 220uF caps with 0.1uF polypro.

I've also done this for budget portable systems. I use one per channel:

I drag a pair of these supplies with hard-wired 20' cables, a Sony Walkman Pro, and a light weight pair of earphones out with me backpacking and get some wonderful wildlife and wilderness recordings on batteries!

You can also replace the massive square metal plate with a piece of Plexiglas with tapered edges. The edges do influence the response of the microphone, but in some situations, what you place the mics on or near will equally degrade the response, so what the heck. My portable rig uses the Plexiglas plates; I usually pack in about 45 pounds worth of stuff and shaving off every ounce that you can helps.

QUESTIONS FROM PREVIOUS POSTINGS

One person asked ‘Why such a big capacitor?’ Well, it has to do with the uncertainty of the input impedance of your tape recorder or mixer. If you have a low input impedance (say 1,000 ohms or less) you need this big of a capacitor to get the low frequency response available with this microphone. If you have a high input impedance (say 10,000 ohms or more), you can get away with a smaller capacitor. If you use a lot of different tape recorders and mixers or if you don't know what the input impedance will be, it's better to use the big cap (and that's why I recommend it).

Some folks have asked why I don't shunt the mylar with a small exotic cap. The answer is simple: the PZM has a rising top octave response. The mylar tames a little of the peak; a shunt cap would only exaggerate it.

SOURCES OF CAPACITORS

Some sources for 10uF esoteric capacitors are:

I haven't had time to research all of the sources. I'd appreciate it if you could contact me if you have other sources to contribute or corrections/updates to this list. Addresses and telephone numbers for the above capacitors are:

• Digi-Key, 701 Brooks Ave S, PO Box 677, Thief River Falls, MN 56701
  Panasonic
  (800) 344-4539
• Electronic Concepts, PO Box 627, Eatontown, NJ 07724
  (201) 542-7880
• Gateway Electronics, 5115 N. Federal Blvd., Denver, CO 80221
  Paxton
  (303) 458-5444
• Illinois Capacitor, 3757 W Touhy Ave., Lincolnwood, IL 60645
  (312) 675-1760
• Meniscus Systems, 3275 Gladiola SW, Wyoming, MI 49509-3224
  Mylar; best prices on ChateauxRoux
  (606) 534-9121
• Seacor Inc., 123 Woodland Ave, PO Box 541, Westwood, NJ 07675
  (201) 666-5600
• Sidereal Akustic, 1969 Outrigger Way, Oceanside, CA 92054
  SiderealKap, ChateauxRoux
  (619) 722-7707
• Sprague Electric Co. There's probably a sales office in or near your
  town. Ask for Engineering Bulletins #2092 and #2752, and catalogs
  #ASP-420K and #C-567A.
• TRT, Box 4271, Berkeley, CA 94704
  IAR "Wonder Caps"
  no telephone number published

What kind of capacitors should be used with a mic pre-amp? How does choice of cap. affect the sound?

Len Moskowitz writes in DAT-Heads digest #300 that the CSB mics use 2 uF polypropylene caps between the capsule and the output. Indeed polyprop (or polystyrene, which are impossibly large in this sort of value) would be the type of choice, with polyester or polycarbonate next on the list. Matching within 1% is probably not necessary but it can't hurt (the input impedance of the decks probably varies by 5% or more, negating any extra care taken in cap matching). The input impedance of the deck (assuming it's resistive, we’ll call it R) and the cap in series produce a low cut filter with the 3dB down point set by:

f=1/(2*pi*R*C) with f, r and c in Hz, ohms and farads.

This means that with the typical (?) 2K input Z of a DAT mic pre, the -3dBpoint with a 2 uF cap is 40 Hz. To change this to 200 Hz, you would use .4 uF caps. For lower input impedances the frequencies go up because R goes down, hence Guenther's comment that the capacitors sometimes need to be larger for proper bass response.

Normally, f is set way lower than you would ever need, to be sure that no part of the rolloff gets in the way of the music. 40 Hz sounds a little high to me, so 2K is probably not the right value for a typical mic pre input. But in the case of swamping the DAT input with low frequency signal, what we're trying to do is roll off some of the LF information so it isn't overpowering. Good luck... [dj]

What kinds of capsules are typically used in 'stealth' microphones? What's good/not good about them and why?

Several DAT-Heads have written or posted on the problems with the small electret capsules used in stealth mics. The capsule almost universally preferred for these is the Panasonic WM-063, or the WM-060, which is theoretically the same but with a phenolic circuit board rather than epoxy. They sound different, though. The capsules are available from Digi-Key (1-800-344-4539) for about $2. You have to buy a bunch and sort them, because there are major differences in sound. There are several problems with this capsule; some are endemic and some can be fixed.

Some complain that the output is too low; this can easily be fixed with a gain stage. Using a higher voltage and larger load resistor (7-9 volts and 10K, for instance) rather than the 1.4 volt that's normally found in tie-clip mics will also help and raise the maximum output level before clipping. The output cap can be changed to a bigger and better kind. A 200-300 uF elcap bypassed with 0.5 of 1 uF of mylar or polypropylene makes a difference.

The more difficult problems are noise and harshness. Because the active area of the diaphragm is so small, the output is low, so the FET contributes a lot of noise. You can fix this by opening the capsule, discarding the FET and reassembling the mic in a new housing. Then you can use a good FET and a 2-10 gigohm resistor for bias (which can cost more than the whole mic capsule), instead of the diode leakage current that is used in the "FET-IC" to bias the FET. You can also make the new housing with an opening to the front that is as big as the active area of the diaphragm, rather than the 2 mm hole covered with fuzz that's there now (a Helmholtz resonator is formed by the hole, the fuzz and the space behind it, which pushes up the HF response, but creates a pole that makes phase problems, thus harshness).

There are better capsules around, but they are hand-made and not cheap. You can use metal diaphragm instrumentation mic capsules, for instance the standard 1/2" from B&K, ACO Pacific, or Larson-Davis. But these cost $580 (ACO) to $777 (B&K). There are other electret capsules (Sennheiser, Lectret), normally available only to manufacturers, that aren't much better. I have made a study of all the other available electret capsules (Primo, NMB, Hosiden, Bo Sung, Pan, and others) but keep coming back to the Panasonic.

There are some other mods that can be done to improve the Panasonic capsule. They are generally the result of extensive experiment and are considered proprietary by those who developed them. The critical issues include: stabilising the ageing of the diaphragm and the back-electret film, getting the front of the diaphragm out into the air as much as possible, keeping the back of the diaphragm/backplate structure sealed from the air as much as possible, keeping the mic housing still while only the diaphragm moves, and operating the FET stage in the middle of a wide linear transfer function. Okay, I haven't given away any secrets, but inquiring minds ought to be able to work good solutions based on this list of problems. [dj]

Why do some shotgun mics have poor bass response?

Most shotgun mics are phase shift hypercardioids at the bass end and line interference types at higher frequencies. Hypercardioid capsules with good LF response are difficult to make, and often it is desirable for their main application (dialogue pickup) to roll off the bass, so there won't be so much (a) room rumble and (b) handling noise as the mic is panned around. [dj]

Which brands/models of shotguns have good bass response?

Neumann, Sennheiser and AKG all make shotgun mics that are used a lot. They all have rolled off bass. The Neumann long shotgun (KMR82) looks like the best, at -3 dB at 60 Hz. Others have the -3 dB point as high as 150 Hz. [dj]

What causes some mics to sound tinny or 'canned' in some situations? How can I avoid it?

Biggest problem is putting the mic where the sound is already tinny. Plug one ear and listen to the sound with the other ear, where the mic is, devoid of the psychoacoustic reinforcement you get when listening with two ears. Move the mic to where it sounds better. [dj]

How critial is it to aim a shotgun mic directly at the source? What happens if I'm off by 5 degrees? 10 degrees?

Look at the polar plot of the mic. With most, plus-minus 10 degrees makes little or no difference. [dj]

Why do recordings made with shotgun mics lack the 'presence' that other mics have? (it sounds like there's a hole in the center of the sound coming from my stereo system) What can I do to improve the 'presence' in my recordings?

By this definition of presence, you probably set the mics at too great an angle apart. Narrow it. Some of the presence also comes from the reverberant environment, which the shotgun mic is trying to get rid of for you. So use something else, like a good hypercardioid. [dj]

What is ‘binaural recording?’

Binaural recording actually predates stereo recording. In binaural recording two microphones are placed near or in a listener's ears (or alternately, an acoustically accurate dummy head's ears). The sounds that the two microphones record are exactly what the listener hears, including the effects of the outer ear (the pinna), the acoustic shadow of the head, and inter-ear phase and frequency response differences that provide localisation cues (the information that lets you determine where a sound is coming from).

When the binaural recording is played back over headphones, the ambient sound field of the recording location is reproduced more-or-less exactly. The sense of being there is amazing and you can pick out voices in the surrounding crowd and the placement of instruments to an unparalleled degree. Until you've heard a binaural recording played back over a good set of headphones, you haven't heard how realistic a sound recording can be.

(Stax sells a series of binaurally recorded CDs, including a demonstration disk, whose realism will literally make your hair stand up on end.) [lm]

What microphones are available to do binaural recordings?

Both Core Sound and Sonic Studios offer a range of miniature microphones that mount near your ears and are suitable for binaural recordings. For binaural recording purists, Core Sound offer a set of in-ear microphones that mount in your ear canals using custom made ear moulds. [lm]

I've heard that binaural recording are supposed to be listened to over headphones. How do they sound over speakers?

They sound good but different. Because binaural microphones have nominally omnidirectional pickup patterns, you get roughly the same effect as a spaced-omni microphone setup. But because the microphone spacing is a bit narrow (7 to 9 inches instead of the more typical 24 to 36 inches) the stereo image may sound a bit compressed. Some binaural microphones can be conveniently used with wider spacing. These provide the usual spaced-omni performance. [lm]

Do you have to hold your head perfectly still while making a binaural recording?

No. Slow movements or movements over a small range during recording are normally unnoticeable during playback. Fast, large movements can be perceived as a shift or rotation in soundstage. [lm]

Can I use headphones as microphones?

Ah yes. The old use-the-headphones-as-a-mic trick. I've tried this with some Sony headphones and it worked but not extremely well. Those Sennheiser HD 414's are a good choice because they come with wind screens.

A lot of people probably don't realise this, but you can also use mics as headphones. Be sure to use dynamic mics! Take a pair of Sennheiser MD 421's and duct tape them to your head. You'll need some female-female XLR adapters. This setup even gives you built-in tone controls! The mics will conveniently attach to mic stands (or in this case headphone stands), which might keep you from nodding off if you get tired. For safety's sake, be sure not to use any mic that is more pointy than your elbow as headphones. Shotguns are definitely out.

Also, omnidirectional mics may make excellent point-source speaker systems. [rg]

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