Liam Smith has left a new comment on your post "SNR Podcast #14":This episode touches on phase between microphones micing a single source. Can you do an entire episode... or two entire episodes on phase and deploying speakers? I am working on learning this properly... but I am still bad at math (i am working on that). Also, no smaart.
Well Liam we're always glad to try to answer questions from listeners. Heck, we're just glad to hear there are listeners at all! I've been mulling this over quite a bit lately and now that I sit down to write a response I'm thinking that it has less to do with what's between your ears (the math) than your ears themselves. The truth is that relying on the math, the simulations and the SMAART readings can sometimes get you in more trouble than it's worth.
Programs like SMAART are great. If you're under pressure to get a touring rig to sound great night after night in tough rooms then you'd be sunk without them. They're also great for setting up installed systems. But for the vast majority of traveling sound guys (and girls, we don't discriminate here) you'd be better off spending your time and money differently. On most gigs you have very little choice about where you put your cabs. Sight lines and safety concerns may not leave you with many options. Letting the lighting guy beat you to the venue may leave you with even less. At least that's been my experience for the last twenty years.
I'm going to go in a little bit different direction than you might have expected with this. There's a lot you should know about dealing with reflections and interactions between adjacent boxes, but for the new guy starting out you're better off learning by experience and having some conversations with other people in the business. But there's a lot you can do right from the console to make sure your cabs are playing nice together.
The first and most important is to not run your system in mono. In nature there isn't one single instance of the same sound coming from two places at once. That's why to our highly developed sense of hearing, phase interactions between speakers making the same sound come across as odd. You brain has spent a lifetime quietly interpreting the sounds it hears and deriving spatial information from them. The easiest way to avoid confusing the audiences brain is to take full advantage of a stereo mix.
Hard panning every input is one way to make dead sure you don't have the same sound coming from both sides of the room. I don't need to tell you that it will be an awkward night if you do that though. So how do you go about it? Let's break down some of the more common inputs you'll see mixing rock shows and see where it goes.
Drums are mostly transient sounds, they happen quick and before your brain can get a bearing on them they're gone. Your brain is good enough to pick up on location cues from panning the toms, but unless they ring out really long there shouldn't be a lot of phase issues with drums.
Bass guitar has a ton of information down low where sound is more or less omnidirectional. If you look at the polar response curve of most subwoofers you'll see that they're only slightly more effective on the side facing the crowd. That said you can do a ton of research and planning to come up with a complex system to delay your various sub boxes to minimize throw onto the stage and smooth out the power alley... and then have your plans fizzle when you can't place the boxes where you need to or you get surprised by a room mode. Go ahead and put the bass right up the middle and worry about the power alley when you get into bigger gigs.
Keyboards have the advantage of almost always having stereo outputs. Just buy another direct box and hard pan your keys. It won't work flawlessly for every patch but it will add more interest to your mixes and has the added benefit of making keyboard players feel more important.
Guitars. Here's where the money is. It means investing in more mics, and you might need a bigger mixer than you have now, but it's worth doing. Guitar players will thank you. It's common practice to pan guitars a little toward the side of the stage where they're standing. If you go too far though you can cheat people on each side of the room out of half the performance (assuming two guitar players). What you can do though is mic each cab twice and hard pan those. The possibilities are endless. Use two of the same mic or two different, EQ them the same or different. Push the levels back and forth. You can really have some fun with it and the guitars will explode in the mix.
Vocals are a bit of a tough customer but if you've done all your panning carefully up to this point you've left a nice spot right up the middle for the lead vocal. If you feel like applying the same principle as the guitars, rather than using two mics just use a Y splitter at the mix. Then you can process each channel a little differently and pan them out. Backup singers are a little easier, especially if there's more than one, push them to the sides a little and you get a great, wide sounding vocal mix.
I know that wasn't what you were fishing for when you wrote in Liam but I hope you'll give it some serious thought. When you don't have many options for speaker placement you can do a world of good for the show from the comfort of the mix position. I hope that was useful and I hope the rest of the Brethren of the Knob and Fader will give it some thought too. There are too many bad sounding gigs going on out there and all for the lack of a little critical thinking and a couple hundred bucks worth of stuff from Guitar Center.