Category Archives: Microphones

Small diaphragm Condenser Modification Results

Last week I sent the small-diaphragm condenser mics from the post below to a friend in Nashville, John Billings. John’s been working in Nashville for years as a session bass player, and  has a very nice studio. I only wanted his general impression, but he went the extra mile and set up a quick A/B test during a recent session. Here’s what he had to say:

First off WOW, thanks for some toys to play with! Here’s what I’ve got so far:Did a session the other day. One song was just these mics out in the room, capsules aligned and secured. You can hear a distict but subtle difference. The mod is much smoother, whereas the stock mic seems to have a significant rise. The other song was a drum corp type of thing, just snare rudaments. Mics placed a few inches over the head, inch or two inside the hoop. I much prefer the mod, though if you need something hyped for top end, the stock mic might be the better one to go to. The mod is smoother, not brassy. Preamps were Yamaha, very neutral. No compression, straight to my SSL AD, 44k 24bit.

The snare mic setup at John’s studio. John Billings photo

I’ve been meaning to upgrade my WordPress account for quite awhile now, but John’s efforts gave me the final push. Now I can post these files here so you can hear the results and judge for yourself. First, the snare drum solo using the stock, unmodified CM90:

drum corp- Snare 1 N Stock

And next is the modified mic:

drum corp – Snare 1 N Mod

Now the same two mics placed further back as a room mic on a full drum kit. Again the stock mic is the first sample:

Drums Room Nady STOCK

And now the modified mic:

Drums Room Nady MOD

John’s studio is equipped with Genelec monitors, so he’s able to hear things very accurately. I listened to these samples on the best headphones that I have, a pair of  AKG 271s, and on my KRK Rokit 6 studio monitors as well. I noticed a slight drop in level on the modified track, and raising this a touch in Mixbus gives more closely-matched tracks in terms of level. (As you probably know, you’ve got to have levels very close when doing A/B comparisons. In blind tests, people always select a source that’s slightly louder as the better track. )

I tend to agree with John. I’m hearing an overall improvement in freq range, with a touch less upper-midrange and an increase in overall smoothness. It’s a subtle improvement… but when comparing them side-by-side, it’s noticeable.

But something that I always find surprising is the fact that really, these mics aren’t all that horrible right out of the box. I’m showing my age here, but in my studio days you couldn’t even approach this kind of signal for less than three or four C-notes. Sure, the quality control isn’t there… for example, the tiny screws that hold the mic body in place are chewed up and look like they were forced together at the factory… but I can’t really complain given the list price.

In order to make some proper mic comparisons, I’m going to have to buy a proper reference mic, so I’m currently selling some excess gear to buy a Neumann KM184. I’d rather have a vintage KM84, but they’re just much for my current budget to bear…maybe someday. And I’m also on the hunt for an affordable BV107 (or perhaps a suitable equivalent) mic transformer… I want to experiment with a transformer-balanced version of the above mod.

A Small-Diaphragm Condenser Rebuild

Back in my studio days, we had a pair of AKG 451s, and we thought we were hot stuff. The 451 is a beautiful microphone, and we’d been using them for several years with great results… my favorite job for these was stereo drum overheads. Then one day Robert brought in a pair of these tiny little microphones… Neumann KM84s. We set them up right next to the 451s as a pair of drum overhead mics, and switched back and forth to compare them and… wow… the difference was amazing. The KM84s sounded every bit as bright as the 451s, but smoother, as if they had more “air.” They quickly became my favorite mic.

Sadly, they went away when the studio closed. One got stolen… their tiny size makes them easy to pocket. And they were pricey even 25 years ago. But I’ve wanted my own KM84 ever since,  even though I don’t really “need” one. And the price has gone up since then… Neumann no longer makes them, their current model is the transformerless KM184. Some have said that the older KM84 is the preferred mic, as these are said to be “warmer” and “smoother” in their sonic character.

KM84’s can typically be found used for about $1200 or so. I still want one, but I can’t really justify spending that kind of cash on a mic unless it’s going to generate the same amount in revenue. (I did spend that much on my shotgun mic, but I use it on every shoot. A KM84 would mostly be useful on location as an interview mic.)

The Nady CM90 disassembled. I understand these are pretty much identical to a number of inexpensive small-diaphragm condenser mics available, like the MXL603.

I can, however, afford a Nady CM90. This mic is one of the thousands of Chinese clones that have flooded the market. It uses a capsule that is supposedly a copy of the Neumann KK84 design. The circuitry is derived from a Schoeps CMC6 transformerless amplifier. Nearly identical to the Nady CM90 is the MXL603, Apex 180, CAD GXL 1200, Cascade M39, and others. Some folks have reported that there is a difference in the diaphragm thickness… the Nadys have diaphragms that are 3-microns thick,  and MXL603s have 6 micron diaphragms. Personally, I can’t tell. I bought the Nadys because they were only $35 each from B&H Photo, and if I totally ruined them, it would be less painful.

Arrows show the new capacitors.

Typical circuit improvements are the replacement of some capacitors, changing ceramic types with polyester film types. Face it, at $35 you can expect to see the cheapest components that’ll work in mics like these. I switched out three, using some parts I had on hand. The values are the same, it’s just the cap types that are different.

A side note: I didn’t come up with the actual number-crunching engineering to figure out the electronics. There is a small community of microphone builders on the internet (examples HERE and HERE) who, thankfully, are willing to share their experience and knowedge. A few of these folks actually did design work in the factories… it’s a real treat for sound geeks like myself to have access to these people. Without their help, I’d surely have a pile of dead mics as a result of my experiments, so I have to express my gratitude to these folks.

Increasing the back vent area with my Taig milling machine. (Taig tools are the perfect size for machining microphone parts, BTW.)

The next modification was to the back vent area. As I understand it, (from Michael Joly of OktavaMod) decreasing the back vents increases the high frequency (HF) response of the mic, and these are known to exhibit a typical HF “peakiness.” Even though the Nady probably didn’t need it, (there are more back vent slots on the Nady than on the MXL 603)  I fired up my trusty Taig milling machine and cut away the ridges in the back vents. I cleaned up razor edges with a small file and replaced the screen.

The other reported problem with these mics is the capsule mount. Again according to Michael Joly, the diaphragms on the chinese clones are set back into the body of the mics about 5mm, where the KM84s diaphram is positioned much closer to the top of the mic. That 5mm ridge around the diaphragm is enough to cause all sorts of HF problems. So I very carefully disassembled the capsule, chucked the shell up in my lathe, and shaved down the pocket. I also took the extra step of beveling the sharp edges, making it look similar in shape to the KM84.

Parting off the face of the capsule shell in the lathe. The brass is a little bit thin and easy to scratch, so I wrapped the shell with masking tape. It machines beautifully, though. This operation could be done with a file in a pinch, but using a lathe gives better-looking results.

I screwed everything back together and powered up the mic. The modified mic is clearly better than stock… the high frequencies do seem more extended and better defined. The stock CM90 exhibits a very slight kind of “splatter,” if you will. Make no mistake, my mic does NOT sound as good as a KM84. I didn’t expect it to. But it is interesting, and a little bit fun as well. I think I’ll send these up to another engineer in Nashville to see what he thinks.

The next step in my upgrade path will have to wait a little while. I want to see if I can build a true KM84 amp and see how this sounds when coupled with the modified Nady capsule. An important part of the KM84’s sound comes from its transformer, and the Nady circuit is transformerless. I haven’t been able to find a source for a BV107 transformer (the original part used by Neumann) or a small enough substitute. I understand that Cinemag 2510 will work in this circuit, but I think these are physically too large for a KM84-sized body… I’ll keep you posted.

The completed mic. I’m looking for some finer brass screen for the next one, but this one looks and works pretty good.

A New Microphone

NOTE: This mic is for sale… $230, includes a custom built walnut case. Email me for more info.

It’s always fun to get a new mic in the studio. This one is twice as nice, since I built it myself. It’s based on a typical large-diaphragm cardioid pattern mic from China… identical to most of the ones you see from ADK, Behringer, MXL, etc. This one is different. It uses the stock mic diaphragm, transformer, and metalwork, but the circuitry was completely replaced with higher-quality components from Mouser. I got help from the folks on the Micbuilders groupon Yahoo.

My new mic setup for testing. Stock mic is on the left, modded mic is on the right, in the iso mount

I’ve built a pair of these in the past that were all stock, so I have a baseline to compare changes that I make. This latest mic is better… the difference is very subtle, but I think that I could pick out the modified mic in a blind test. There is a slightly extended bass and more definition overall. This is probably due to the capacitors… the stock mic uses tantalum caps, the mod uses all polyester film and Nichicon electrolytics. I think this probably contributes most to the improvement in the sound.

Some other changes that I’d like to try are some different transformers, though this can be a pretty expensive upgrade with an unknown benefit. Only one way to know for sure. But I’ll likely save that experiment for another mic. Right now, this one is good enough to put directly into inventory to either use or sell. It was a fun build, though mic #2 took me quite a while to finish. I thought I’d popped a JFET, but it turned out to be a bad solder joint on a capacitor that took me forever to track down. All straightened out now, though.

A pair of mics under construction. One of the capsules has lost tension, it was replaced. I’m still having difficulty getting #2 to work… I believe I have a bad JFET caused by me miswiring the transformer.

Making the boards work in the new mic is a trick, since the components are all physically larger, but I was able to coax them into place.

A New Shotgun

Thanks to some series work that I’ve landed in Knoxville, I’ve recently made an upgrade to my mic locker. My workhorse mic, a Sennheiser ME66/k6 combo, is a very good mic… for the price. They can be bought new for around $500. But it’s long been on my list of things that I’d like to improve, if ever I could afford it.

For critical applications, I have a MKH415T that I love. It’s a beautiful old mic, once used by the ORTF (the French equivalent of PBS). But there are some considerations that prevent me using this mic as much as I’d like. Mainly, it’s the fact that 415’s don’t like humidity, and begin to develop self-noise in damp air. Once things dry out, they return to normal, but the unpredictable nature of the mic means that it stays in the box 95% of the time. (According to Sennheiser, the 416 was a later development and uses improved circuitry to eliminate fluctuations in performance from humidity.)

The other soundperson on the series, Raleigh mixer Neal Gettinger, loaned me his 416T to use for the shoot, and it sounds markedly better than the mic I normally use. Thanks to some sales of used gear at Trew, I had a balance that I applied to a brand-new Sennheiser MKH416p48.

It doesn’t seem like much until you plug it in. Physically, it’s a bit smaller and slightly heavier than the 66, so I had to get new mounting clips for my Rycote suspension. Soundwise, though, there’s a big difference in the two. It’s hard to describe in words, but the 416 has a smoother overall quality… the top end is more defined, and the low end seems extended. These differences really show up when you compare the mics side-by-side and switch between them. But almost as important is the familiarity factor… most people know the 416, and it’s been a common player in movie production…. so much so that years ago, when the 416 was discontinued for a model with improved specs, the resulting uproar from the location sound community caused them to put it back into production.

I hate to do it, but I’ll probably sell my 415T to help pay for the new mic. I’ll most likely need to sell the ME66 as well, but I haven’t quite decided yet. The fact that the 66 can be battery powered gives it a slight advantage, since this mic can be plugged directly into any camera without the need of a mixer. Like many true condenser mics, The 416 needs  48 volts phantom power to operate properly, and some  cameras (and even mixers… older Shures are reported to deliver only 18 volts) can’t provide enough voltage.

How To Make Turtle Clips

I can hear you. You’re saying, “What the #%*& is a turtle clip?”… a reasonable response to the above headline, actually. I didn’t know about them myself until recently. A “turtle clip” is a mic clip with a little wire bail over it. The wire is there to keep fabric away from the mic, preventing clothing rustle.

A commercially available turtle clip for a Tram lav

If you’re flush with cash and short on time, you can buy these from B&H for $20 apiece. Or you could make them yourself. All you need are some bits of copper wire, something round (like a dowel or broom handle) to use as a former, a pair of needlenose pliers, and a pair of cutters. Optionally, you can use a soldering iron if you want to get fancy, but it isn’t required. The clips that I made require a bit of Topstik or Moleskin to secure the mic, but they work as well as the ones from B&H.

Any round object will do as a former. The size determines the diameter of the finished mic clip… about a half-inch or three-quarter-inch rod will do. Wrap the wire around the former as if you were winding a spring one and a half turns. It’s easiest to wind a little extra and then clip off the excess wire later.

Starting a turtle clip. Copper wire is wound around a round former, 1 1/2 turns

Now, using the needlenose pliers, bend a half turn of the wire up 90 degrees. Clip off any excess wire and you’re done, unless you want to solder the ends. Soldering only takes a second and does make the finished clips a tad stronger and smoother, but it isn’t required. If you haven’t done much soldering before, this step could be

Bend one of the loops 90 degrees. I used a vise, but pliers can work fine for this.

a little tricky, but it’s very easy with a little practice. (HINT: Heat the wires first, then apply the solder to the wires. Don’t apply solder to the soldering iron, except maybe to help transfer the heat to the wires.)

Once you’ve made a few of these, other variations and improvements will surely come to you…

Snipping off the excess wire. Having a little extra wire makes handling these a touch easier while you make them.

making clips with two bails, for example, or rectangular shapes rather than round. They will get rather bent out of shape with regular use, but they’re easily replaced and cost only a little time. And if you’re too busy to take the ten minutes it takes to make these, I’ll be happy to sell you some that I’ve made… only twenty dollars each!

My collection of homemade turtle clips. They didn't take long to make, and they get easier with a little practice.

Comparing Lav Mics

I don’t have a huge collection of lav microphones, but I’ve tried several different models over the years. All of them work amazingly well, though I’ve naturally developed a preference, and I do have one particular model that I tend to use as my “go-to” mic (which I’ll reveal in a moment).

Some wired lavs- from left to right, unmarked EV lav, evCO90, Sony ECM44b, Sony ECM55b

The problem with comparing different lav mic models is that many wireless transmitters use their own wiring conventions. Lectrosonics uses a five-pin connector (a TA5), while Sony and Sennheiser use a 3.5mm jack… and the two aren’t interchangeable. So while I have a fairly diverse collection of lavs, they aren’t all wired to use the same transmitter. One of these days, I’ll get rid of my other transmitters and go “all Lectro,” but that’s a somewhat expensive proposition.

Two Sennheiser lavs

My lav mic locker includes the following:

  • Countryman EMW (wired for Lectrosonics)
  • Countryman B6 (Lectro)
  • Audio Technica 899 (Lectro)
  • Lectrosonics 119
  • Lectrosonics 152
  • Sennheiser ME102
  • Sennheiser ME104
  • Sony ECM44B (hardwire)
  • Sony ECM55B (hardwire)
  • Sony UWP lav
  • EV CO90 (hardwire)
  • EV MysteryLav- looks suspiciously like a Sanken COS11

These two mics are the ones I use most often... a Countryman EMW and my current favorite, the Audio Technica 899

There is a really good article about comparing several different models of lav mics at Ken Stone’s website- click here. I haven’t done extensive side-by-side comparisons of all the mics that I have, but I’ve got some favorites. I found a good deal on some Countryman EMWs. These are small, rectangular, side-address lavs, similar to Trams, which are kind of an industry standard. But Trams were too expensive and only available new. The EMWs small size and resistance to handling noise are big advantages and I used these for several years. But then I happened to try an Audio Technica 899 during a 3-person shoot… two people wore EMWs, and one wore an 899. While all sounded good, I was surprised at the reduction in room noise when I soloed the 899… there was a significant improvement in the amount of background noise. Since then I’ve managed to purchase a set of three 899s, and these are my favorite mics in most situations.

Any mic with a larger head is generally not my first choice on the set, since most clients would rather hide the mic in the talent’s clothing, even though this means a reduction is sound quality. My Sony 55b almost never gets used for this reason, even though it’s an excellent-sounding mic. My Lectrosonics mics have some rather questionable-looking cables, so I keep them to use as backup mics.

My First Place & the Ambient EMP Eumel

I was recently in Nashville, TN shooting an episode of HGTV’s My First Place. I was glad to finally get the gig… they’d called me a number of times before, and I was always booked. And because of the way things work out on this show, they don’t usually give their crew much notice (less than 24 hrs on one occasion). Scheduling last-minute shoots is difficult… I try to make them work, but I’m often booked. That’s how it’s been with My First Place in the past, so I was especially pleased that I was able to make this shoot work.

I worked with two Nashville freelancers, producer Laura Douglas and DP Chris Conder. Both have been working in and around Nashville for a number of years, and Laura had worked in news, so we all had similar experiences to share. The show is produced by High Noon Entertainment in Colorado. I’ve worked with them before, but this particular shoot was done with an all-local crew… no one flew in for the show.

One of two Ambient EMP 5s transformers that I recently bought. I've been needing these for a long time, and they work like a charm.

I tried out a new piece of gear on this trip… an Ambient EMP 5s eumel. (a eumal–pronounced “oymal–” is German for widget.) It isn’t a very sexy bit of kit, and it’s pretty pricey (about $118 each from Trew Audio) but it’s extremely handy to have. All they are is a transformer built into a nicely machined Neutrik connector. What they do is convert a wireless lav microphone– in this particular case, my Audio Technica 899– into a hard-wired version. Since these were going to be seated interviews, I figured this would be the perfect application. I’m happy to report they work like a charm. I have several mics that are wired for Lectrosonics transmitters, and now I can use these all as hardwires if the job calls for it. In the past, I have used a Sony ECM55b for my hardwire jobs, and while it works great, I have often wished to use a mic with a smaller head– like my Countryman EMWs or my ATs, since the Sony is a little harder to hide. My Ambient EMPs give me more options, and options are always nice to have on the set!

The guys that were buying their first place had a budget of $140K, and wanted a minimum of 1,000 square feet. Nashville is a nice town, but the real estate prices are pretty steep for most people. (In contrast, we’re looking at a 2,800 square foot house here in Chattanooga, and the selling price is $192K. That’s nearly 3x the house for about $50k more dollars. There’s just no music industry here, unfortunately.)

Producer Laura Douglas interviews first-time homebuyers Bret Marchbanks and Daniel Sircy for HGTV's My First Place. Chris Conder on camera.

The only bad part about the shoot was the drive home. I work as a local in Nashville for one-day shoots, so  had to drive home that night. We finished the interviews at 10PM local time, and since Nashville is in a different time zone than Chattanooga, I pulled into my driveway at 2AM. But I’m looking forward to working with them again soon.