4. With monitors, I find that less is more. They are meant to be loud, not sound good.
I find good-sounding monitors mean they don't need to be that loud for the artist to hear what they need. Clarity and volume are correlated, sure, but other factors are at play.
To the OP,
Measuring speakers can be a tricky business - that's why the people that are good at it can make money out of it!
Anyway. The key is practice, and figuring out which bit of the measurement is an artifact of the environment, and which are the products of the speaker itself. After that, you'll need to learn what to do now you understand the graphs.
I'd recommend learning the basics (and testing the measurement setup) indoors where you're not pushed for time or worried about weather or annoying the locals.
Take a speaker that you don't mind abusing a little, and do some measurements. Try these:
- Close to the cone
- Around 1' away, on and off axis
- Around 10' away, on and off axis again.
Note how each measurement has an amount of "fuzz", and that "fuzziness" generally increases as you move the mic away from the speaker. That's from reflections creeping into the measurement.
Next, EQ the low-frequency response so that, when the mic's close to the cone, it measures flat (NB - best done with sealed speakers). You might need 20dB of boost, which is fine for playing around at home but should be avoided when setting up the PA system.
Now the LF response is nice and flat, take the mic out into the room again. Measure in a few different positions in the room. Note how the once-flat low-frequency response is now anything but. Also note how the response changes according to location.
It's stuff like that which we can't really EQ out. Everyone's getting a different response, so "fixing" one might make the others worse.
Sidenote - I'm quite lucky at the moment - the living room gives a peak at around 45Hz pretty consistently. Knocking that down a bit benefits pretty much every seat. Other peaks and dips do occur and I have to live with that. There's another one at 15Hz, which is useful - means my sub runs flat to 15Hz without needing loads of power to get there.
Okay, so I'll assume you've got to the point where you've measured everything you can with a small speaker indoors. You've EQ'd it, can spot reflections vs speaker effects, etc.
Lets get the PA system out.
I'm gonna run through setting up a tri-amped system (2-way mid-high, plus sub(s)). Some of this will apply, some of it won't.
LF/MF crossover is fairly easy: the cabinets are basically omnidirectional, and there's limited scope to damage anything so long as you're sensible.
Pick a crossover point that's suitable for the cabinets in play (ie, you might run a 15" down to 70Hz to meet a 15" sub that's only reinforcing a bit, or you might run that 15" down to 120Hz if it has a couple of 18"s to do the heavy lifting).
100Hz is usually a safe bet for most cabinets, but it's something you get a feel for.
Throw an LR24 crossover at it, and see what you get. LR24 crossovers are useful in a few ways (they sum flat, offer plenty of driver protection).
Next, invert either the LF or MF band, and run the sweep again. By tweaking the delays, you'll be able to get a nice deep and symmetrical notch. Set cabinets back to normal polarity and you should get a seemless blend between the cabinets.
MF/HF crossover is more tricky.
This time, you've got to consider how much stick the compression driver/horn combo can take, as well as off-axis response.
Things to consider:
- As the wavelength approaches that of the diameter of the cone, the cone speaker will start to show narrowing directivity.
- We want the off-axis response to be smooth.
- As you go higher in frequency, cone drivers will start to have a fairly rough response. Some drivers are smoother at the top end than others.
- You don't want to drive the compression driver/horn lower than the manufacturer says is safe, unless you're doing something odd. Example - I'm running a 1" driver down to 1.6kHz, but it's only keeping up with a 6" midbass. ie, it's not gonna go that loud. If you tried to run a 1" driver down to 1.6kHz and keep up with 2x15"s, you're gonna be replacing diaphragms most gigs.
- As you move the mic around, you'll be closer to one driver and further from another. Your phase curves will move accordingly.
So, a 15" 2-way cabinet with a 60-degree horn might have a higher crossover point than the same with a 90-degree horn.
Armed with that information, you might look online and find the HF unit is fine down to 1kHz, the horn loads down to 700Hz, and the midbass driver starts getting rough at 2kHz.
That means you'll have a band of 1kHz up to a little under 2kHz to get things lined up in terms of matching the directivity of the cone and horn. Matching them up nicely will get you a nice smooth off-axis response, which is a Good Thing. Have you ever listened to a 15" 2-way box with a tiny 1" HF driver? - Even if it sounds good directly in front of the cabinet, moving a couple of steps to the side will yield a very different sound.
When it comes to EQing things, here are some general guidelines: (some are more set in stone than others - it's up to you to decide which ones are more flexible in your case)
- Avoid boosting below the port tuning frequency.
- Every 3dB of boost means the driver is receiving 2x the power in that area. 6dB = 4x power, 10dB = 10x power.
- A narrow notch in the response is rarely worth the power required to boost it to flat, and usually only occurs in one mic position anyway (see note above about making sure the EQ is beneficial in more than just one seat)
- Narrow peaks sound worse than narrow notches. If some seats get a peak and others don't, it's often best to bring the peak down and give some people a notch in the response.
- Don't worry much about >15kHz. Your HF driver may roll off at 16kHz, and be 10dB down at 20kHz. At live music volumes, nobody will notice. EQing 20kHz back to flat isn't going to be noticed, but will mean the HF driver gets that bit warmer.
Apologies for the long post. I hope some of it comes in handy.
Chris
PS - +1 on everything Frank said above. Good info there.