USB Mics Show Promise, Inconsistencies - Radio World

USB Mics Show Promise, Inconsistencies

Ira Wilner Tries Three Models From Samson and MXL
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The Universal Serial Bus (USB) has become the de facto standard for PC connectivity with a USB 3.0 standard about to be released that will permit extremely high-speed data capable of supporting the fastest external disk drives and HD video streaming. So it is no surprise that USB microphones have recently appeared on the scene.

The USB microphone is the culmination of the dream to provide affordable digital microphones. Neumann's original digital studio microphone retailed for over $13,000, not exactly within the budget of the average radio station or Webcaster.

When you move the analog-to-digital converter into the microphone itself you can elegantly solve several problems.

First and foremost, the critical weak signal from the microphone does not have to be transported through many feet of cable to the preamplifier and recording gear. Instead, the preamplifier and analog to digital converter is less than an inch away from the microphone capsule.

This vastly reduces susceptibility to externally introduced electrical noise and distortion. The preamplifier can also be designed to provide the perfect match between capsule and converter.

What makes a USB condenser microphone a practical popular alternative to conventional microphones?

For one, it replaces both the preamplifier and the sound card. Many built-in computer sound cards suffer from inferior audio quality and excessive noise due to the electrical environment inside the typical computer. As a result, serious direct-to-hard drive recordists often will use outboard sound cards and dedicated microphone preamplifiers to obtain better quality. A USB microphone contains the essence of a sound card. Nothing more has to be toted around with your notebook computer.

Shrink that computer into a palm-sized unit, running Windows XP, and you'll have a near pocketsize remote broadcast system that'll get your audio home wherever there is a Wi-Fi connection.

Unfortunately and conversely, the USB umbilical cord makes it impractical to use the mic in a recording studio/control room setting. You can't get sufficient USB cable length. And you cannot use existing in-wall microphone lines and patch bays.

While USB microphones are dirt cheap and pretty good by comparison, the old maxim "you get what you pay for" still holds true. I took a look at three similar, yet quite different, products.

Podcasting: MXL Studio 1

The first is a new entry sold as a "Desktop Recording Kit."

The Studio 1 from the Marshall Electronics' MXL multimedia division is well packaged in a padded plastic carrying case that also holds a screw-in mic stand adapter tiny tabletop tripod, USB cable and soft cleaning cloth.

It looks like a typical large capsule condenser mic until you look at its bottom. Instead of the standard three-pin XLR-style male pin connector, this mic sports a mini USB jack.

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Most large condenser mics copy the basic body design of the expensive Germanic variety. Unscrew a bottom ring that threads around the body of the mic connector and you can remove the body sleeve revealing a frame containing the electronics.

The Studio 1 uses a tiny double-sided printed circuit card, with one side being mostly a solid copper back plane for noise immunity. One FET impedance converter transistor and a 32-pin surface-mounted IC makes up all of the active circuitry. A pair of 100 µF electrolytic capacitors are onboard to couple audio out to the headphone jack.

Yes, this microphone has an obviously labeled 1/8-inch mini earphone jack just below the capsule! What sets this entry apart from most others is it is essentially a full-duplex sound card. The USB data path allows the microphone to play back audio from your audio editor's timeline directly into your headphones! No computer sound card required.

Just above the headphone jack but hidden behind the capsule grille is a red LED indicator light that illuminates when the mic is receiving power through its USB port. So, you can tell at a glance if it's properly plugged into a powered port and ready to work.

You might ask, why bother to put a headphone jack into a USB microphone when most computers have built in sound cards? The reason is the limitation of the Windows Sound Manager to work with more than one sound card at a time. If you choose the USB sound device, so you can record from it, you cannot bring its output into your Windows Sound Mixer applet to permit playback monitor mode through your computer's built in sound card. The work-around is to put a full bidirectional sound card interface inside the microphone itself. How well does it work? Unfortunately, I found the preset mic output level too low to be useful in monitoring yourself while speaking into the microphone.

Is the cute little desktop tripod a replacement for a mic boom or floor stand? If you need to travel lightly yes, but if you need to protect your posture, no. You will have to curl yourself over to get close enough to the microphone to address it properly unless you place the tripod on a stack of books. The tripod and the stock stand adapter have no shock absorbing quality. There is no foam windscreen.

The USB mic is mostly plug-and-play, with no drivers to install as they are already built into Windows XP and Vista (should be the same for Macs).

So, how did the Studio 1 sound? In a word, muddy. It is tubby with way too much proximity effect bass boost and insufficient highs for broadcast use. The lesson is that the cheaper microphones that are obviously aimed at the novice market are not likely to be broadcast quality. Move on to other choices.

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Samson CO1U Bargain: Samson CO1U

Sometimes less is more.

The Samson CO1U comes packed in a smallish plain cardboard box. Its accessories include a cloth pouch instead of a hard case, a stand adapter, tabletop tripod and USB cable. In addition there is a European thread adapter screwed into the stand adapter, which was a pain to extract but a nice touch for those with non-North American mic stands.

The accompanying user's guide is well written with lots of useful information.

The mic is a little larger than the MXL Studio 1 and resembles costlier Shure KSM studio mic line. It too is not supplied with a windscreen. The tabletop tripod is similar but has plastic threads in its adapter that can be more easily damaged by crossthreading. Again, this accessory does not position the mic well.

The mic has a unidirectional digital interface, no headphone jack. As a result, I had no difficulty getting Adobe Audition 2.0 to recognize it as a recording device. What you do lose is the ability to hear yourself live while recording. Hey, do like the old timers and cup your hand over an ear.

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The CO1U has some professional features accessible through an optional device driver not supplied with it but downloadable from the Samson Web site. The SoftPre driver permits you to remotely control three internal settings of the microphone. You can change the preamplifier gain, thus preventing distortion or reducing internal noise. You can switch in a high-pass filter to reduce rumble and breath noise. And you can switch absolute audio phase 180 degrees!

These are highly professional touches. Are they needed? Out of the box, no. The CO1U's default internal gain structure is right where you'd like it to be. In testing this mic it did not distort or clip. And the mic fader in the Windows Sound Mixer applet could be raised more than half way to get a good record level. Absolute phase is correct. And the mic does not seem to exhibit much of a proximity effect. So no need for the bass rolloff filter.

So, how does it sound? Better than a $100 dollar mic has any right to sound. I really like its sound. It is quite flat, has a nice crisp high end and isn't muddy or mushy. Will you like it as a voice mic? It has a somewhat lower propensity to pop, but it may be too thin on the bottom for some tastes. It won't turn a shrimp into a gorilla. And it won't create a lot of midrange air. But you'll experience good voice articulation and smoothness not normally heard in this price range.

If you are a budding musician and want to lay down a few instrumental accompaniment tracks, this USB mic is musical enough to capture the nuances of your guitar strings without sounding boxy.

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MXL USB.009 Reprise: MXL USB.009

The third and more expensive USB microphone of the lot is the MXL USB.009.

Like some of MXL's mics aimed at serious engineers, this one comes packed in an aluminum flight case with lockable latches. The case is quite a bit deeper than necessary and has room for far more than the included accessories. The extra space can be put to good use if you purchase the optional foam windscreen.

The mic adapter clip is the same as provided with the Studio 1, but the folding mini tripod is replaced with a weighted base with a 3 inch high threaded pipe stub. Unfortunately the base is too small and light to afford good stability. The mic sits on it quite precariously.

The microphone's build is solid and reasonably well machined. It has a rather long body, almost 8-1/2 inches from stem to stern. As a result it sits a bit higher on your table requiring less arching of your back to address it properly.

This mic also has a 1/8 inch headphone jack with a built-in duplex sound card interface like its little brother. But here's where the similarities end.

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The USB.009 has three volume controls in a vertical line. The top control is a mic level trim that permits you to adjust the preamp output driving the A/D converter. This is an important feature as it allows you to maximize bit depth without clipping the converter.

The middle control adjusts the headphone monitor mix balance between the zero delay analog feed directly from the mic preamp and return audio from your computer as it plays out your sound files. Even if you use a low-latency ASIO sound card driver, one of which is recommended in the MXL user's guide for download, the live return audio will still have a slight delay since it has to pass through digital buffers and a D/A converter. If you set up your multitrack recording software to playback only the tracks you want to sing with, minus your voice, you'll want a 50/50 mix of the computer tracks and the direct sound from the microphone.

This capability alone makes the USB.009 far more useful than its Studio 1 cousin.

The lowest knob is headphone volume. This headphone amplifier has a much higher and useful output. While you'll appreciate having all three controls on the mic you will not like their feel. The controls are stiff. The knobs are so short they are hard to grasp. If you have fat fingers you might have to ask a child to adjust them for you.

Finally, this microphone sets itself apart by its digital converters. It can record at a 24-bit depth at a 96 kHz sample rate. It can record serious digital audio sound files with studio quality bit depth and resolution. Unfortunately I was unable to test at the higher performance settings (see below).

The USB.009 is plug-and-play at default CD audio quality settings, 16-bit/44.1 kHz. My computer immediately recognized it and rerouted playback audio through the microphone's headphone jack. Very cool! And, of course, at the same time I could monitor the microphone audio directly.

Unfortunately you can only select the USB microphone sound card interface sample rates under Windows Vista operating system, not under XP. So, I was unable to test the mic with higher definition sample rates and bit depths.

Adobe Audition 2.0 was unable to connect to the USB microphone using the Windows sound system, but the older Cool Edit Pro had no problem at all. I was finally able to get Adobe Audition 2.0 to work after I installed the recommended ASIO4ALL free ASIO sound driver. But it too would not permit higher resolution settings except for 24-bit mode.

How I Tested the Mics My test bed was a custom ASUS laptop computer. The sound card was an external FireWire MOTU Traveler. The USB microphones were individually connected to the laptop. Cool Edit Pro and Adobe Audition 2.0 were used to capture the USB audio. Using my voice, which is highly asymmetrical, negative going peaks, I was able to judge absolute phase for each mic. I compared the mics to each other and to an assortment of other mics recorded via the MOTU to sound files at 16-bit/44.1 kHz. These are driver and software compatibility issues that should have long been worked out. MXL would do better to provide their own device drivers designed to get the most out of their hardware rather than relying upon third parties to write shareware drivers. MOTU's own drivers for my Traveler work fine enabling me to record 192 kHz sample rate files on the same computer under Windows XP.

How does it sound? I evaluated the microphone's sound quality in two ways, first recorded at 16 bits at 44.1 kHz sample rate played back through its headphone jack. Then I compared it to the playback through my MOTU sound card.

The built-in headphone amplifier does not have sufficient headroom to comfortably drive medium low-impedance loads such as the beyerdynamic DT-770. The tracks sounded cleaner and more effortless through the MOTU. So, for critical monitoring I would not use USB playback. It is adequate for self-monitoring while laying down a voice track or for editing. Also, MXL got the absolute phase right on this mic.

The USB.009 has an extended seismic low end, so much so that it really needs to be mounted in an isolation mount such as the MXL-57.

Don't even think about hand-holding this mic. You can hear every subsonic muscle tremor or even the lightest tap on a desk or table. The upper midrange has a slight peak which adds pleasant brightness useful to enhance vocal articulation. The highs are crisp though not quite as silky as my better studio mics.

Overall the USB.009 could be used successfully for vocal or instrumental recording. It does sound decidedly darker than the Samson CO1U. Those who find the Samson a bit thin will like the low end on the USB.009. And unlike the Studio 1, this mic does not sound muddy at all.

For under $300 you get a nice-sounding microphone with a complete built-in sound card facility with playback monitoring and simultaneous live mic monitoring. All done with the convenience of a single USB cable.