When it comes to complex recording setups involving multiple mics, phase problems can be hard to avoid. Drum-set miking provides the classic example: with so many sound sources being picked up by an array of mics, some parts of the kit will often “cancel out” or undergo tonal changes when tracks are panned and mixed together. The phase difference between a bass DI signal and a miked cabinet can also lead to engineering headaches.
Polarity-reverse switches partially address these problems by permitting a 180-degree phase shift in a problematic signal. However, though polarity reversal sometimes leads to a better sound, often it is too extreme. The only consistently effective way to minimize phase problems has been careful microphone positioning — that is, until the introduction of this “secret weapon” from Little Labs.
The IBP (In Between Phase) Analog Phase Alignment Tool ($550) allows continuous phase adjustment of a mono signal from 0 to 180 degrees. This processing is accomplished using high-quality passive analog filters, and without using digital or analog time delay. There's a lot more juju going on in this rugged little box than can be covered in a short review. Suffice it to say that the IBP is a powerful problem solver. As usual with Little Labs products, the manual divulges a wealth of information and helps to unravel many technical mysteries.
Ins and Outs
A front-panel ¼-inch DI instrument input and adjustable line-level output adds to the IBP's value. Also helpful is a “re-amp” circuit, which allows you to run line-level signals from a recorder into an instrument amplifier. Phase alignment can be bypassed or engaged on the DI and re-amp functions. Balanced XLR input and output connectors are located on the rear panel, as are two unbalanced 1¾4-inch outputs.
Front-panel controls comprise six buttons and a single phase-adjust knob. From left to right, the buttons are labeled Line/Instrument (selects input, includes status LED); Earth Lift (ground lift); Phase Adj (adjust) Bypass; Phase Invert (polarity reversal); Phase Adj 90°, 180° (selects a sweep range of either 0 to 90 or 0 to 180 degrees); and Phase Center Lo/Hi. The Phase Center button toggles between two analog filtering modes, optimized for either wide-bandwidth audio or low-frequency signals. The easy-to-grasp phase-adjust knob to the right of the switches is encircled by white dots, which are useful for calibration.
Utilized on a variety of prerecorded tracks, the IBP made a believer out of me in no time. On a troublesome pair of tracks with bass DI and amp signals, I obtained a dramatically improved bass sound after a brief period of adjustment. The impact of phase-aligning the bass DI to the amp was astounding; it resulted in improved sustain and transients, chest-thumping punch, and about 4 dB higher gain.
Applied to an ambient mic track for rock drums, the IBP impressed me with its ability to fine-tune big drum sounds, making it possible to selectively nudge the kick, snare, or cymbals forward in the mix. Throughout the trial period, the IBP's passive filters worked their magic transparently, without noticeable coloration, added noise, or gain reduction on processed tracks.
Not surprisingly, the IBP was unable to improve upon drum overhead tracks that were recorded with a phase-coherent XY mic pair. On one occasion — when activated on stereo drums in the 0-degree position — the unit produced some minor phase shift that disappeared when bypass was engaged. However, a similar test conducted on stereo acoustic-guitar tracks (again recorded in XY) yielded subtle but exciting tonal and presence enhancements with a small amount of phase manipulation.
For tracking and mixing in any analog or digital studio environment, the IBP is an indispensable tool in the battle against phase problems. I can't imagine why no one has marketed such a device before, but I'm glad that Little Labs has done it now — and done it right.