Audio theory question

[indigo7us]

Hi there,

I have an audio theory question, and am looking for input from others, from a speculative standpoint.

First, I am running a soundcraft si expression 3 board through a dbx driverack pa2 to tri-amped jbl vs-3115 speakers. Subs run from an aux

Both the driverack and mixer have graphic eqs built into them.

Would there be any advantage to pink noiseing and using An rta to flatten the board master bus outs and then using the driverack graphic eq to further tune the overall system (flat isn't always desirable), or would I be splitting hairs?

Let me know if anything needs clarification with the question.

Thanks!

 

[MNicolai]

Your Driverack should do the heavy-lifting for tuning. Any EQ in your console should be for your inputs to make the microphones and such sound good. If your Soundcraft craps out on you just before a show, you should be able to replace it with any other console without having to recreate your system tuning EQ.

Playing pink noise and walking the room, taking averaged samples from multiple audience locations should do the trick. Wash/rinse/repeat analyzing and making corrective adjustments until you can walk the room and get a mostly-flat response. If JBL has any specific EQ/crossover parameters for those cabinets in their spec sheets, you'll want to include those in your EQ corrections too.

While you're at it, check polarity on all your speaker elements. Any elements out-of-phase with one another because of a faulty cable or a manufacturing error will send you down a deep rabbit hole trying to ascertain why your system sounds wonky.

Don't leave your ears at home when you tune. A flat RTA response in one part of the room may be anything but flat in another area. The goal of a flat system isn't to give you perfect sounding speakers -- it's to give you a consistent, known EQ for your room. A starting place so when you do sound check every night, you've already minimized your potential for feedback and given yourself a balanced system. Once you've gotten a flat response, play some high-quality, full-range music tracks and see how they sound. If they sound awesome, then give yourself a pat on the back. If they sound wrong, try and identify what doesn't sound appropriate and try some minor adjustments and see if that improves. Could just be your music track was mastered poorly in recording, but it could also be your RTA isn't accurate at all frequencies.

If you have a professional RTA and a calibrated mic, trust your RTA more than a music track or your own ears, at least until you've gotten pretty far through tuning. If you have an iOS app and a $200 mic off the internet, trust your ears more than your RTA.

I've found for tuning house systems that people prefer a few dB bump on the low-end to make the sub frequencies more pronounced, but not so much so that it's boomy or overwhelming.

--

***Clarifying note: The above method is for tuning the house system in a venue. If you're tuning a portable rig, you'll probably want to do your speaker EQ in the Driverack, and as-needed do your room EQ on the outputs of the mixer as you switch between venues.

 

[MNicolai]

And don't forget, always cut before you add when doing EQ's. Cut the peaks first, then give small bumps if you need to fill a couple gaps. If you excessively mix 'n match cutting and adding, you'll be fighting against yourself trying to find a flat response.

 

[themuzicman]

Hi there,

I have an audio theory question, and am looking for input from others, from a speculative standpoint.

First, I am running a soundcraft si expression 3 board through a dbx driverack pa2 to tri-amped jbl vs-3115 speakers. Subs run from an aux

I'm not usually a fan of subs on aux, unless you need the aux send for something like dedicated sound effects, in which case the aux is there for use by the six and fed at the same level the Main L/R are fed by any other source material. Phase issues pop up when you start sending a signal to an aux sub at a louder level than the rest of the PA, negating the idea of a flat frequency response.

Both the driverack and mixer have graphic eqs built into them.

Would there be any advantage to pink noiseing and using An rta to flatten the board master bus outs and then using the driverack graphic eq to further tune the overall system (flat isn't always desirable), or would I be splitting hairs?

Most of the time I would start by tuning the room in the Driverack, and "tone-ing" the room in the desk, that way the room can stay tuned and each show can tone the room to how they see fit at the desk.

However, it seems like you are using the Driverack as a crossover and not as a system processor, I'm assuming you have a single Driverack and it is powering a single Left and a single Right speaker. In this instance, you have a crossover, and you should be loading in the crossover points of the speaker into it, or whatever manufacturer preset they have. With a little more knowledge of theory it isn't the hardest to make crossover settings, but it's something I wouldn't attempt unless you have a solid understanding of frequency and phase relationships.

In this instance, because your Driverack is a crossover, I would do the tuning on the outputs of the desk because you lack a system processor. The Crossover should stay tuned to match your speakers and shouldn't try to function any other way.

 

[JD]

Well, pink noise has it's uses and limits. It's good for picking up on a bump or notch that is in they system or the room, but trying to produce a flat room can be a venture into unnecessary frustration. The better use is to do a room walk and notice if there are obnoxious hot-spots that have to be dealt with. Equalizing the system will not change the distribution of hot spots. That is more of a "position of hardware" problem. The temptation is to make things sound good at the location of the board, which does not help the audience too much
A well designed and laid out system should not require much EQ. That said, all systems need a little. Whenever you are adding an EQ curve, you are trying to force something out of the system that it does not want to produce for some reason. If your graphic looks like ocean waves, something else is wrong. Still, doing a good noise check can help diagnose unknown issues such as polarity problems or botched crossover points.

 

[themuzicman]

Well, pink noise has it's uses and limits. It's good for picking up on a bump or notch that is in they system or the room, but trying to produce a flat room can be a venture into unnecessary frustration. The better use is to do a room walk and notice if there are obnoxious hot-spots that have to be dealt with.

I can't agree with most of your post. True Pink noise has uses and limits but it is also one of the best tools to clean up your system when used with a good FFT analyzer to read both Frequency response of a room and phase response of a room. We need to admit that when it comes to tuning, a computer will always be better than a human ear, assuming that we know how to interpret the data and provide a meaningful fix. Once we have a flat response with both frequency and phase, then we can tone it to liking (adding color) but I rarely see folks who deal with a lot of clean reproduction (musicals in particular) go with anything other than a flat room once you have run a Smaart rig through it for a few hours.

In a massive speaker system, the only way you are going to deal with unevenness is through a computer and the ability to figure out where you have destructive phase issues. You could do a lot of this with IR measurements too, but pink noise will allow you to walk a room and hear coverage issues and phase issues pretty quickly once you know what to listen for.

I do agree that a well designed system will require little EQ, but you still need to work with the room even with really good cabinets. You're always going to need to fight things like low-end pileup in the back of a room and manufacturing differences driver to driver but once you have a well tuned room, you will see huge advantages by not needing a ton of input EQ.