Review of Nakamichi CM300 mikes

For all those people who've been internet searching for information on these microphones, I've seen a variety of questions asked about these microphones on the net, and some wacky answers, here's some correct info.

I bought three of these microphones (CP1 & CP2 capsules with CM300 backends), and two CP4 shotgun capsules, way back when I started video production in the early 1990s, and have been using them ever since.  They cost me $1800 at the time, and have proved to be dependable and do a very good job.

Before I started working for myself, I'd worked in other people's studios and had really grown to hate the lack of interest in good sound equipment.  From using awful mikes, trying to use a group of mikes with radically different audio characteristics together, only having one mike to cover everything, mikes with very short leads ending in phone jacks, horrible noises getting into unbalanced lines, etc.  And when I bought my first camera, it came with a truly dreadful mike.  So purchasing decent microphones was at the top of the “to do” list.  Fortunately one of the local audio/video dealers understood what I wanted, and sold me these.

What I ended up with was three virtually identical mikes, with omni- and uni-directional capsules, and a couple of super-directional shotgun capsules.  With these mikes, the interchangeable capsules screw into the backend, giving you a kit that can be assembled for the type of pick-up pattern you need.

They were only battery powered, but that didn't bother me at the time, since my (then) camera had no phantom power supply, though having to deal with batteries was a nuisance.  More recently, I modified the CM300 mike backends to run off phantom power, to carry on using them with other equipment, rather than replace the mikes.  I've never really cared for phantom power (with any cable and connection gremlins you get horrible crackles and crunches, some mixers produce nasty hums when their phantom power is used, few mixers let you switch phantom power to each input individually, etc), but it is a useful thing to have (when it's working well).

One might comment about the frequency response being a bit limited, and the odd ±3.5 dB points instead of the standard 3 dB limits.  But at the time, 15 kHz was the standard bandwidth for television and radio, better than most compact audio cassettes could handle, about as good as the average adult's hearing, and mike frequency response charts are notoriously bumpy.

For those unfamiliar with a “shotgun” mike, its pick-up pattern is meant to be a narrow cone in front of the mike, with very strong rejection of sound from all other areas.  It's not like a parabolic spy mike that's used for concentrating on sound from a great distance.  You often used to see them in news gathering, where the scrum of sound recordists held one on a boom above the head of the person being filmed.  Because of the way they reject sound (hearing through a long tube, with interference-pattern slots cut in it) they can have some peculiar audio characterstics if you use them when recording music.  Though mine never sounded too bad, I think my Sennheisser ME80 was slightly better.  My CP-1 and CP-2 capsules were the best ones for music.  I tend to favour the spaced-omni technique for stereo sound.  If I had any kind of single mike failure, or if I ever needed something in mono, I just ignored the second mike.

Replacement batteries

When I bought mine (brand new) in the 1990s, there was an older CM-100 model that ran off a 1.5 volt AA battery, and a newer and better CM-300 model which ran off a similarly sized 9 volt battery.  And, I was told that there was a different back-end that could run off phantom power, but I have no information about it.

I've found that electret microphones with higher battery voltages to drive their pre-amplifiers seem to be better at handling very strong audio levels without overdriving.  Plus, the battery can flatten quite a lot before it's too flat to work.  The batteries do last a long time, but the microphone signal quality drops significantly by the time the battery gets to around 6 volts (sensitivity drops, and it sounds muffled).  They aren't going to work, or work well, if you put an even-lower voltage 1.5 volt AA cell into them.

The original 9 volt batteries aren't available, anymore (they were banned for containing mercury).  Alternatives were available, and some probably still are, but are hard to find, and might need to be imported.  The listed compatible batteries were H-7D/A, Mallory TR-126, or Eveready E-126.  Possibly an Eveready 206, too.  An older style A1611 industrial 9.0 volt industrial battery used to be a contender, but was redesigned and is now too fat to fit inside the mike.

I just taped together six LR44 cells, wound cardboard around them to make them a snug fit, and inserted that into the battery compartment with a banana terminal sitting on top, so it's the right length (or you could replaced the mike's internal battery spring with a longer one).  They're easy to buy everywhere, cheap, and still last a long time.  I might get a year or two's use out of them, so long as I don't forget to switch them off between sessions.  The batteries are more likely to go flat from self discharge, than the microphone draining them while in use.  If you're worried about leakage, you could use the more expensive SR44 cells, but I haven't had any leak, yet.

Another solution would be to extract the 3-pin XLR, replace it with a 5 pin, wire the battery terminals to the other two pins, and use an external battery box.  Or, for the brutal approach, drill a tiny hole in the casing to bring out wires for an external battery.  Then, either way, you could use those cheap rectangular 9 volt batteries that we used to use in 1970s transistor radios.  But the build-your-own battery-pack, described in the prior paragraph, avoids having to modify the microphone.

Replacement mike holders or clamps

Like most mikes it comes with its own custom clamp (the Nakamichi HD-62), and being a cylindrical rather than conical mike it's a bit more difficult to find a suitable replacement for missing or broken clamps than the usual hand-held mike (and this isn't a hand-held mike, by the way, it has no internal shock-mount to minimise handling noise).  While you can easily buy generic conical mike clamps in a couple of common sizes from many music stores, it's rarer to see cylindrical clamps on the shelves.

The section that holds the mike is hard black plastic, it has very little give in it for the mike to snap in and out of it, and isn't going to take kindly to be bashed about during inconsiderate handling of mike stands with the clamp left in place.  Though mine lasted thirty years before one split (glueing it only worked as a temporary fix).

And the section that screws onto the stand has an unusual thread, larger than the 5/8″ thread traditionally found on mike stand pipes here (where the pipe was often directly tapped), or the even smaller 3/8″ thread (where a small bolt is often crimped into the pipe), creating another problem for some people—finding a suitable thread adaptor.

My clamps came with a thread adaptor for 5/8″ mounting, and they've stayed firmly in place ever since I inserted them, but people buying these mikes second-hand may find it missing.  Leaving you with a few choices:  find a replacement thread-adaptor (I'm awaiting some info on what the actual thread is, and will update this page), pack the gap with something (wrap a rubber strip around the stand's pipe and screw the clamp over it), fill the cavity with something (epoxy?) and tap a thread into it, metal-glue a smaller thread adapator into the space, or replace the entire mike clamp.

Taking out the thread adapter, and measuring it with a pair of digital calipers (of allegedly ± 0.1 mm or ± 0.01″ accuracy), it's 20.6 mm (0.81″) diameter across the threaded section, and 18.1 mm (0.71″) diameter across the straight section.  Then measuring inside the mike clamp, it's 19.1 mm (0.74″) across the threaded opening.  So, I'm guessing that, somewhere, there was a sound studio using ¾″ or 7/8″ pipework on their mike stands, and Nakamichi designed it to fit.  Studio booms or deskmounts for the big chunky vintage microphones, perhaps?

Out of curiosity, I went digging through some of my removed plumbing parts from my house (the old shower rose, a leaky float valve from the airconditioner, etc) and it has the same threads.  They fit together very nicely—the mike clamp onto float valve, the thread adaptor into its locking nut, and into the shower rose.  I'm of the understanding that we have ½″ BSP-threaded pipework fittings, and the float valve has ½″(15) boldly emblazened onto it (in metric, it's a 15 mm fitting), but the threaded section is clearly wider than either of those measurements.  The outer diameter roughly measures as ¾″, though the inner diameter of the float valve is roughly ½″, but measuring the metalwork that way is very confusing.  A (much) larger-than ½″ fitting to go over ½″ pipes is the only explanation that makes sense.  I'm much more used to things like nut and bolt measurements being their actual size (as per the more usual 3/8″ and 5/8″ mike clamp threads).

I've seen one page (the Windtech adaptor linked here) where it's said that the RCA mike clamp threads used ½″ NTP pipe thread.  Fortunately ½″ BSP thread is compatible with ½″ NTP thread (the only size where BSP and NTP will fit together, apparently).  So, it looks like an RCA mike thread adaptor is the way to go.  The Extinct Audio thread adaptors also look right, but they don't state the dimensions of the larger outer thread.  However, I've since been told that the Windtech M-11 RCA thread adaptor doesn't fit.  So I'd expect that these Extinct Audio RCA thread adaptors probably don't, either.  Even though all their photos look like they might, and people have said that RCA mike mounts used ½″ pipe threading (which does fit).

The mikes are quite narrow (21 mm diameter), and cylindrical, so need a special clamp to hold them, or need packing around them to fit a larger generic one.  Probably the more difficult aspect of ordering a replacement is finding one for a non-tapered cylindrical mike, rather than a conical mike (conical mike clamps won't grip properly).  Few of the generic mike clamp adverts describe their dimensions adequately.  You may see specifications that they fit 20 to 30 mm microphones, not quite sure if they're measuring the narrow and wide ends of a conical clamp, or the clamp stretches to fit those range of sizes, and the clamp may be for conical mikes without saying so.  For search keywords, you may find that drumkit, instrument, camera, shotgun, or boom mounting, mike clamps more likely to be compatible, as mikes used in those situations generally are cylindrical.

I've used a Røde SM5 shockmount for many years.  While it's a bit bulky, it also reduces noises coming up through the stand getting into the mike.

I'm told that a Schoeps SG20 mike clamp fits quite snugly, though may be a bit lightweight.

The AKG SA60 looks promising, it's supposedly made from tough flexible plastic that handles 19 to 27 mm mikes.

The On-Stage MY320 might be suitable, it even has a bit of a shockmount built into it.  I tend to favour rubber mike clamps over plastic.  Even if they fail with age (usually after many years), they tended to be better at handling more knocks, are a bit more grippy, and are more flexible with not-quite-the-right-sized mikes.

The adjustable SmallRig BSM2352 looks promising for hot-shoe/cold-shoe camera mounting.

Sprung clamps may or may not work well, some are tapered for conical mikes, and can be noisy.  But can be useful for mounting mikes in suspended upside-down positions.

The good

I've always liked the sound quality of the mikes, and they've proved good at being used for close-up and distant-miking.  The three mikes have virtually the same audio characteristics, so using them for stereo or group recordings means that you don't notice sonic oddities between them.

Being tube-shaped rather than conical mike meant that the mikes could be clamped in any direction without it sliding out of the mike holder.

Having a low-impedance transformer-coupled output is good for noise immunity over long lines, and has been compatible with everything I've used them with, including unbalanced equipment (simply by connecting the negative signal end to ground).

The mike is wired in the modern standard way:  A positive sound pressure against the microphone element produces postive voltage on pin 2 (and/or negative voltage on pin 3), of the XLR connector.  There is no centre-tap, pin 1 of the XLR only connects to the mike's body casing (which is also the audio ground for the unbalanced mike-facing side of the coupling transformer).

Being self-powered has meant that I could use them with any equipment with a mike input (though I later added a modification for phantom powering).

The windscreen/pop-filters for the omni and uni capsules is a coarse wiremesh backed by a fine wiremesh screen, so there's no decaying foam to worry about.

Having a built-in low-cut filter means that you can compensate for proximity effect, acoustic rumble, and windnoise at the mike, and use them with equipment that had no low-cut feature in itself.  And use them with ease with equipment that buries such controls inside cumbersome menus.

They have a switchable 10 dB pad in the head, before the preamp, so you use them in some extremely loud situations with distortion occurring.  Though having to unscrew the capsule to reach the switch is a bit of an inconvenience.

The power switch does completely disconnect the battery, so you do not need to take the battery out to stop it going flat.  Some people on the net falsely beleive that they need to, but they're wrong (and this is easily discerned by examining the internal circuitry).  Though it is a good idea to take batteries out if you don't plan to use the mike for a long time, so they don't cause damage if they leak when they get old and you've forgotten about them.  And while having any switches on the mike does lead to the chance of being accidentally mis-set, I've only had one careless person do that (grab the mike and shove the switch without even noticing that they'd done so), it is handy to be able to switch off a mike so you can determine which mike is which in a group.

The bad

The use of a special battery was a bit annoying, at first.  They weren't cheap, though did last for a very long time.  Later, the battery became unavailable, so even more annoying, and I had to make up batteries by taping button cells together.  Not being phantom powerable is a bit limiting, but it was very easy to convert them.

The windscreen/pop-filters soon became loose, and were prone to sliding off.  I've had to glue the plastic framework back together a few times, but the grippy strips that's supposed to hold them on don't grip tightly enough, and are too slippery (friction fitting plastic against the metal of the mike body).  The foam windscreen cover for the shotgun mike eventually deteriorated after about twenty years, so I've got to find a replacement for it.  I was fortunate to discover this before it dissolved into goo and got into the mikes.  So if you've got boxed up shotgun capsules, you want to carefully inspect them.

The box they come in wasn't set up very conveniently.  You have to remove the wind/pop filter to put the mike away, leading to the filter becoming sloppy very quickly.  It would have been better to be able to put the mike away still fully assembled.  I ended up carving a large space out of the foam so I could do that.  I hate carry cases that make you needlessly disassemble equipment, it wears things out, and bits go missing.  These days I keep them in a plastic toolbox that is big enough for that, and to hold all the various accessories.

The shotgun mike is very long, much longer than the usual mike blimp windcages, so I've never bought one for it.  I'm in two minds as to whether to try and find a super-long one, or buy a newer mike that fits the usual windcages.  I've used the mikes on a few occasions where the original foam windsock just wasn't good enough to stop wind noise (I ended up wrapping my cleaning cloth around the foam windsock to muffle the wind).  And after some twenty years the foam completely disintegrated, though there are generic replacements you can buy.

The mikes have no anti-shock mounting, so handling noise is very noticeable (although they're not meant to be hand-held mikes).  Likewise for noise mechanically transmitted through the stand.  I've made shockmounts, and bought third-party generic ones to deal with that issue.

If you have to move a directional mike around, such as one mounted on a camera, or using a roving mike, you do hear the accoustics of the background sound change quite noticeably.  All directional mikes suffer from that, but it was surprisingly prominent with these mikes.

When I first bought my mikes, I tested one mike first, bought three when I was happy with it, and bought a couple of shotgun capsules.  One of the shotgun capsules was a bit naff, so I sent it back for a replacement.  The supplier sent me back my original mike as the replacement (there was a telltale internal scratch, and it came back in a box with my gaffer tape on it).  I wasn't pleased by the attitude of returned rejected goods being fobbed off unto another customer (the same customer, in this instance).

Having a switch on the mike body does chance the risk of them being knocked into the wrong position, though I've only had that happen once by someone being careless.  I actually pay attention to how I'm handling equipment, and don't treat it like I'm throwing firewood into a bucket.  I still like having the switches there, but they would have been better if they required more effort to change their position.  Covering them with tape doesn't help, apart from losing the ability to use them, they're still susceptible to being knocked.  I may try building up a barrier around them that protudes higher than the switch.

Summary

I suppose the ultimate comment about them is that I've used them for almost thirty years, and not wanted to replace them.  Over that time I've compared them with other mikes, and have never been displeased by their sound.

Naturally, I'd expect a more modern mike (mine are from the 1990s) would be better.  But all mikes sound different from each other, and just about everyone plays with the EQ on their mixer.  I don't do high-gain distant-mike work with them (any more) to be bothered by whatever their noise floor is.  And back when I did, the pre-amp in whatever I was using them with (mixer or recorder) would have been the noisiest thing in the chain.

If you'd like to hear them in use, this YouTube clip of The House of the Rising Sun used two of them for recording the organ in stereo, and one on the guitar.  Both are fairly closely miked, two or three feet for the organ, a few inches for the guitar.  The vocalist was on a Tandy Realistic mike with a Shure capsule (which was surprisingly good, considering these are allegedly the inserts that failed Shure's quality tests for using in their own mikes).  All of that recorded live, simultaneously, in a small room with only very tiny amounts of bleed-through into the other mikes.