Wednesday, May 30, 2012

Getting To Know Your Boxes

EQ is a very deep subject. When you're making adjustments to the graphs on the main outs of a system there are a myriad of factors involved. Reflections, reverberation, absorption, diffusion, temperature, humidity, and the list goes on and on. Something that can help out is to know exactly what you're dealing with right from the speakers and take that into account when you're EQing the room.

There are a million little tricks to learn. The little quirks that each box has. Like that high mid thing with JBL Vertec boxes, or the way Yamaha horns always seem crispy. While it's good to hear all that and file it away, you never know how true something like that is. An engineer talking about a particular box may have only heard it inside, or even just in one particular venue. The best way is trial and error and start your own file.

Most people don't have access to an anechoic chamber so you have to figure out how to hear the box in question without hearing all that a room will impart to the sound. Going outside is a great way. On a still day there won't be a lot of effect from the wind, and setting up over grass and away from buildings will help minimize reflections. Even if you can't do that, just get in the near field of the speaker, where you're just getting the blast of air directly from the drivers and not anything else. Be reasonable about this. If you're checking small studio monitors you can get your head right in there. If it's big try-amped boxes, protect your ears, listen at sane volumes for the distance you're at.

To start off get things so the system is as flat as possible. Then throw on some music that you know really well and take a listen. Don't try to figure out anything just yet. Take a listen all the way through a couple of tracks and make a few mental notes about stuff you hear, don't hear, or don't sound quite right.  Then you can get into the graphs a little and start to see what you can do. Things to look for are a "hump" or build up in a particular frequency range. Stuff that sounds great for DJ work will often sound like garbage for vocal work. Listen to the highs and see if they're bright or murky, if there's anything missing or over accentuated.

After a little touch up, start the tunes over again and start to move around. How far off to the sides can you get before things start to fall off? Are there any spots where there are weird interactions between cones and horns? Run the volume way up and way down. What differences do you hear? Keep touching the EQ until you're about as happy as you can get it. When that's all done try some different program material. If you've been checking rock, try pop, jazz, country, or classical. Plug in a mic and do some talking.

When that's all done you can do one more thing just to double check. If you have access to a pink noise generator and an RTA (real time analyzer) you can check to see how flat (or not) the speaker is now that you've adjusted it to taste. A lot of phones can do this for you these days so it shouldn't be tough. Notice too how we're doing this pretty late in the game, instead of starting out with it. Technology is a terrific aid but you want to trust the processor between your ears first and use the tech to back it up and improve it.

Keep in mind that when you're looking at the curve on an RTA you really don't want to see a flat line. Good sounding systems will usually have a really big hump down in the lows and then from the high miss up to where only dogs can hear things should gently taper off, how much is a matter of debate so just go for what sounds good to you. What you're looking to knock out is any big peaks or dips. A spike at 300 Hz will make vocals sound boxy and a dip at 2.5 kHz will make final consonants hard to hear and speech less intelligible.

Lastly, if you're going to be using more than one box in a stack it's a good idea to see how the boxes interact with each other. Trapezoidal cabinets have angled sides to allow you to stack them tightly and wind up with a splay that makes the drivers overlap nicely in the listening area. It's not always right though and there are a few designs that I've found work better with the spacing changed. Some work better stacked vertically, sometimes with the top boxes inverted to get the horns closer together. There's a lot that goes on in the way boxes interact with each other so be as thorough as you can. Keep in mind at this point the EQ will be less effective and the greatest changes will be made by moving things around physically.

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