this is a review of the UAD Little Labs IBP plugin. IBP stands for in between phase.
The basic idea is that sound waves can be completely or partial out of phase anytime you record with more than one microphone receiving the same sound source (ie two mics on a guitar amp, a drum set multi-mic scenario, live recordings, a stereo pair with some kinds of placement (such as recording a grand piano)). When these signals are out of phase, because each frequency is a different length and because of other factors such as resonances in the room, often one range of frequencies will be more out of phase than the other (ie high vs low). Often just throwing the phase switch would make things sound worse than better.
The IBP was designed to accommodate those problems where things were not perfectly in or out of phase. It has a dial ranging from 0 degree to 180 degree phase and a button to select high or low emphasis. When UA designed the plugin, they also added a dial to adjust delay in milliseconds; this is helpful in cases where you have two or more mics on the same sound source at different distances, not just different angles (such as a snare mic 1" away from the snare and overhead mics 36" away from the snare).
My subject is an acoustic jazz quartet all recorded in one large room simultaneously: drums, bass, piano and sax. There were issues in these tracks of bleed, of course, that were making some instruments more masked than they needed to be. EQ can help, but getting the phase and timing correct can do a lot of good without changing the EQ at all.
On the drum set, I used IBP on the snare and kick. For the snare, I adjusted the timing (by ear) to align well with the OH mics to provide the best clarity, presence and focus of the snare drum. For the kick, I adjusted it to get the best clarity, focus and low frequency extension and resonance possible. Because of this, rather than having to roll off all the lows on the OH mics, I was able to leave them in which gave both clarity and body to the kick that would be almost impossible to simulate with eq without using some sort of reverb or resonance tool on the kick. Using the IBP allowed the natural resonance to shine through.
On the bass, I adjusted the phase and timing to give best rejection of the sax and to take advantage of the bleed into the piano mics to give the bass more body and clarity.
I wouldn't want to have to mix without this plugin anymore - it's way, way too useful to give up. That said, I'd give this plugin a 4 out of 5 stars because, though the plugin is excellent, I would love to have a read out for exact times of the milliseconds delay along with the ability to see it measured in samples vs milliseconds. In DAWs other than PT you can go into controls view to see that, and in PT you can automate that control and then check the value on your edit screen, but that's a bit of a pain. I did that a couple times when I wanted to conserve UAD processor power by using digidesign sample delay in place of the IBP where possible. It may also be nice to have up to 10 milliseconds just for effect, but not necessary. Kudos to the folks at UA for a great design job on this one!
Here's some audio samples of a mix with and without the IBP compensation - flies are 48k24bit: