Heads up on the Digi MBox... Electronic Musician reviews

[theblue1]

[see my post below for an update...]

Judging from the December 2002 Electronic Musician Review of the Digidesign MBox it doesn't look like it would be a very good pick for music production:

Although the Mbox is great for live recording, sound design, mixing, and general audio use, I have reservations about using it as a primary unit for overdub-style multitracking. The problem is latency. As with all host-based recording systems, there is a discernable time lag between the audio coming into and the audio going out of the system. The time lag sounds like a slapback echo, and on my G3/600 MHz it felt like somewhere between 40 and 80 ms. That makes recording tracks over a rhythmic bed a dicey proposition. Your internal musical timing can get confused, making it really tough to nail a part.

The Mix knob that affects the balance between the input and the playback is meant to alleviate the problem somewhat by allowing you to focus to a greater or lesser degree on the new part or the background tracks. But mixing a blend of the incoming signal with the same signal going out in sync with the backing tracks makes everything coming in sound flammed.

Moving the Mix knob all the way to the playback position lets you hear only your audio as it is being recorded relative to the backing tracks. But then there is a disconnect between your fingers playing the instrument and the resultant sound emanating from the box. (Digidesign recommends lowering the volume on the record-enabled track in Pro Tools LE to prevent the delayed signal from coming back into the headphones.)

Not only that but...

The problem with new products is that they often suffer from problems that more mature products have already worked out. The Mbox suffers from a number of hardware and software problems that range from mildly irritating to thoroughly annoying.

The first issue is that there is no master volume control for the analog outputs. There's a headphone volume knob, but it doesn't control the line outputs. As I mentioned earlier, the input/playback Mix knob blends the relative levels of the incoming signal with the internal playback signal and then routes the mix to the outputs. If there is no input signal, the knob works as a volume control because it is mixing between the playback signal and silence. But if you have any input, such as an open mic in the room, that approach doesn't work. I understand the desire to create new paradigms, but an output volume control is an essential feature for most audio devices.

Another welcome feature would have been MIDI In and Out. I assume that there would not have been enough bandwidth on the USB bus to accommodate it, but it sure would be a useful addition.

The Mbox also suffers from a series of hardware and software glitches. To start with, the box outputs noise and ticks when it's powered up but before the Digidesign extensions have loaded. That means you have to turn off your audio monitors every time you reboot. In addition, upon first powering up, the Mbox often outputs silence or distortion rather than a normal signal; the problem occurs with Pro Tools LE as well as with other audio software. My work-around is to boot up with the Mbox connected to my Mac and then disconnect and reconnect the unit before starting to work.

The Mbox is also persnickety when it comes to switching back and forth between Pro Tools LE and other audio software. Problems even occur when using a program like Peak; if I quit Peak and then launch Pro Tools LE I might on occasion only get silence instead of an audio signal. The issue involves using the Digidesign sound drivers to output non — Pro Tools audio from the Mbox. The work-around is to output all other audio through the Mac's headphone output, which involves adding a mixer to the situation, taking away from the simple, portable aspect of using the Mbox in the first place. You may often need to unplug the Mbox from the USB connection and then plug it back in to clear hardware glitches, so you'll want to keep the Mbox close at hand when you're using it.

When Digidesign learned about the problems that I was having, it promptly shipped out a new Mbox. When I installed revision 20 of the firmware, Digidesign USB driver 1.0.1, and Pro Tools LE 5.2.1, a number of other problems that I had been experiencing disappeared. The problems that I've just described, however, remained.

 

[theblue1]

[writer's note after the fact: I did some digging and found that you can actually monitor with zero latency -- but each new track must be manually shifted by the conversion latency* (not the much longer monitoring latency described above) amount after recording it and before recording subsequent tracks. There is, apparently, no latency offset functionality in Pro Tools. (!) That seems quite odd to this 6 year veteran of PC based HD recording... and selling the Mbox as a "studio-in-a-box" when it requires this klugey workaround for any overdubbing is a stretch, it seems to me.]


*This conversion latency is 164 samples, according to most of what I read, which, at 44.1 kHz works out to just under 4 ms. This is a short enough amount of time that it is probably unnoticeable to most folks... but if timing cues are taken from subsequent tracks and not the very first -- this unadjusted amount could "add up" -- in a highly unlikely worst case scenario of a 16 track project where timing cues were taken from the most recently recorded track each time a new track was recorded, you could end up with a timing gap over 50 ms between the first track and the last. So, it is clearly appropriate to take Digi's recommended solution and manually shift ("nudge") each track 164 samples toward the beginning of the project after recording it and before recording subsequent tracks.