Digidesign Mbox 2 Pro

By Garrett Haines | June, 2007

In the last few years, Digi’s famed Mbox line in particular has undergone numerous changes — growing from a single device to a whole family of portable LE interfaces. From the ultra-compact Mbox 2 Mini to the new Mbox 2 Pro, users have been offered a range of Mbox interface choices. But how does this new-fangled design hold up? What distinguishes this particular piece from the rest of the pack and, more importantly, how does this upgrade apply to you?

OVERVIEW

Presently, the Mbox 2 Pro is the most feature-rich (and physically largest) unit of the entire family. While the rest of the line uses the USB 1.1 protocol, the Mbox Pro 2 is FireWire-based — taking advantage of the bandwidth increase compared to USB 1 to support up to 24-bit/96kHz resolution. (Note: For laptops or desktops that have 4-pin instead of the full 6-pin IEEE-1394a FireWire connectors, users will need to use the supplied 12 volt DC adaptor — test for this before taking it on location.)

For most recordings (done in 24-bit 44.1 or 48kHz), the Mbox 2 Pro supports six simultaneous inputs and eight simultaneous outputs. Other new features worth mentioning are MIDI In and Out and a BNC word clock I/O. A surprising, and very useful, addition comes in the form of a set of RCA phono preamp connectors (see sidebar). This makes the Mbox 2 Pro a great choice for archival, sampling, or DJ work.

I was really happy to see the small security receptacle on the side panel. This is the same lock slot found on laptops and other high-value electronic gear and while not foolproof, it’s a significant deterrent against would-be thieves.

Above that, I was impressed by the unit’s heavy-duty design. I had expected the knobs to get ripped off within two weeks of no-punches-pulled, on-the-road recording, but it stood up to some serious field testing — making the Mbox 2 Pro a great companion for remote assignments.

APPLYING THE MBOX 2 PRO

On the subject of remote assignments, I used the Mbox 2 Pro to record a live concert with Irish troubadour Mark Dignam. The first thing I noticed was that the two pres were pretty nice sounding: clear, relatively uncolored, and giving a good bit of gain before getting noisy. Likewise, the instrument inputs are solid, with a touch of midrange that proved to be flattering on Mark’s Taylor acoustic (and in other tests with a Yamaha bass loaded with EMG pickups).

The headphone jacks seemed to be more powerful than the original Mbox, and were definitely less noisy at high volumes. Having individual adjustment options is a plus, especially when tracking multiple players. But having MIDI available with my LE interface was probably one of my favorite features. As an original Mbox user, I’ve always needed an additional interface to hook up sound modules. That’s now a thing of the past. At about 10" wide and 9" deep (excluding rear connectors) the Mbox 2 Pro fits beneath most laptops, and helps declutter most MIDI setups.

DJs, remixers, and people who want a copy of their vinyl transferred to CD will be happy about the phono pres. There’s even a grounding post — a prerequisite for phono work. We do a bit of preservation work at Treelady Studios, so I can say the Mbox 2 Pro doesn’t have the rich sound of a $900 Acoustic Research phono preamp, but it’s as good or better than the common $50 Rolls phono pres I see in many studios.

I also used the Mbox 2 Pro as a digital-only interface. Recording a voiceover spot, I used a Millennia Media TD-1 going into the new Waves MaxxBCL as my A/D. I connected the S/PDIF out of the Waves into the Mbox 2 Pro, and added some BNC cables to handle word clock issues. The team worked seamlessly, but there is one thing to remember: The Mbox 2 Pro cannot be used as the clock source when choosing a S/PDIF input — so it’s important to make sure your digital source is capable of handling clock duties, or you’ll need a dedicated system clock.

The only real issue I had was a buffer underrun when recording sessions with a single mono track. Many of us have experienced buffer overruns; these happen when the audio data is coming in faster than what the interface/computer combination can handle. My problem was the exact opposite — which is fairly humorous when you think about it. The Mbox 2 Pro is essentially saying, “I’m much too powerful for your silly project. Why don’t you come get me when you need to track a band?” Fortunately, Digidesign’s tech support was able to help me remedy the problem, so no real complaints here.

CONCLUSIONS

Mbox users have been waiting for quite some time for increased throughput, MIDI ports, and improved mic preamps; the Mbox 2 Pro delivers these, and a good bit more. From multiple lines out to the phono preamp stage onwards, this unit packs a lot of flexibility in a relatively small package. Original Mbox owners will want to look into this unit for the improvements in the headphone amps alone. The short of it: This is a roadworthy, resilient unit that offers greater mobility and flexibility for Pro Tools LE users than its ancestors. My only complaint is that now I just can’t wait to look at those 003 units.

just the facts

Product type:
Hi-def portable audio/MIDI interface/production system.

Target market:
Engineers looking for a multitrack mobile recording system.

Strengths:
Roadworthy. Increased feature set including good sounding pres/headphone jacks. MIDI ins and outs. Built-in phono pre. BNC word clock in and out.

Limitations:
Nothing significant.

Price:
$799 (list)

Contact:
www.digidesign.com

PHONO INPUTS AND THE RIAA CURVE

You may have seen gear with a “phono input” before. This is more than a marketing term: A dedicated phonograph circuit is needed for correct playback of vinyl records. (Sure, you can plug a record player into any line-level RCA jack, but the sound will be thin and tinny.) Since the 1940s, records have been manufactured using a “pre-emphasis” equalization curve. To reproduce the original recording, you need a way to apply inverse curve to undo — or deemphasize — the original equalization. The reason has to do with a problem of basic physics, and a devilishly ingenious way to overcome it.

WHY THE CURVE?
By the 1940s, the predominant consumer format was a rigid platter made from the secretions of the shellac beetle. These discs were played at 78 rpm (revolutions per minute), earning them the nickname “78s.” (Actually, a lack of mastering standards meant playback speed ranged from 71.29 up to 80 rpm. Different manufacturers cut masters at different speeds.) Shellac discs were resistant to scratches, but very brittle, making them susceptible to breakage in shipping and everyday handling. In general, a 78 could hold one song per side. (That means you would need 8 to 10 discs for a contemporary 18 song hip-hop release.)
It did a record company no good to mail a disc to a radio station only to have it arrive in pieces. So vinyl records were developed for promotional, or “throw away,” use. Unlike shellac discs, vinyl records could be shipped without fear of damage. And though they were less resistant to scratches, vinyl’s physical flexibility quickly won over critics and consumers alike.
Meanwhile, some clever mastering engineers figured out a way to improve fidelity and fit more than one song on each side of a platter. First, the cutting process was adjusted to slow down the playback speed from 78 to 33-1/3 rpm. This extended playback time a bit, however something still had to be done about the groove size. Consequently, a pre-emphasis equalizer was applied to the cutting signal. The exact amount of boost and cut was not arbitrary, but nearly every company releasing vinyl had their own way of doing it. EMI, HMV, Columbia, Decca FFRR, NAB, Ortho, BBC transcription, and numerous others developed individualized methods. (First the 78 speeds, then the repro curves! Notice a theme? No standards. Welcome to the music industry.) This proved somewhat problematic, so the RIAA (Recording Industry Association of America) established a standardized pre and post curve, earning it the name, RIAA curve.

HOW DOES IT WORK?
As audio engineers, we know that low frequencies are larger (have a higher amplitude) than high frequency sounds of the same perceived loudness. To cut a groove big enough to reproduce bass sounds caused a few problems. First, they took up more space, which decreased the amount of music that could be placed on the side of a disc. Second, large bass grooves made it difficult for the playback cartridge to follow, which would lead to high distortion, skipping, and perhaps even launching the stylus off of the platter. High frequencies also posed concerns. When cut at their standard size, high frequency grooves are very tiny. During playback, the physical contact between the stylus and the groove creates high frequency noise. This unwanted noise would leak into playback of treble and quiet parts, reducing the overall quality.
To resolve this problem, mastering engineers began to artificially lower bass frequencies as well as raise high frequencies during the cutting process. The smaller bass grooves allowed more music to fit on each disk. Upon playback, the curve is reversed, so that high frequencies are deemphasized and low frequencies are boosted. In a properly setup system, the result should be a reproduction of the original ‘flat’ master recording. This meant more running time because of smaller bass grooves. Meanwhile, the larger high frequency grooves yielded a better signal/noise ratio as the noise is reduced by the playback curve.
So next time you’re at a party, throw out this little story about the RIAA curve. If the girl/guy you’re talking to sticks around for the whole thing, you know you’ve found a keeper.