Tuning PAs/Ear Training.

[Nick_1234]

Hello all.

I would like to improve my skills at tuning a PA. Being able to catch the frequency in which the system is feeding back, and put a halt to it would obviously be ideal.

Are there key frequencys that would be "go to" in such an event? Maybe even some ear training techniques that can be done at home within a DAW using a signal generator at multiple frequencys to obtain recgonition.

Respect.
-Nick

[dannyschmanny]

what problem frequencies arise are going to depend on the room and its characteristics. a good free tool you can use at home is actually called mapp. you can get it free from the meyer sound website. i used to be a an assistant tester for it. what it does basically, is let you type in the demensions and layouts of a room, place a virtual system in it and calculate what kind of coverage and trouble areas you will have in that setup. you can also look into books by bob mccarthy. one of the founder's of meyers sound analyzer called SIM. he tunes venues around the world.

[Jim vanBergen]

While I am a HUGE fan and user of SIM, (SIM 2 & SIM 3 certified) as well as being longtime associate and friend of Bob McCarthy, I think that learning how to accurately name pitch is a totally different art that room analyzation and correction. While Bob's book and SIM3 are a great tool, they won't help you to identify frequency well.

I'd look into the "Golden Ears" CD's which teach the art of listening & interpretation, as well as investing in a decent 1/3 octave EQ, a pink noise generator, and sweepable oscillator. I also highly suggest a device to measure frequency, such as an RTA, dual FFT, SMAART or SIM computer but ultimately using such a device allows you to "cheat" in finding the frequency.

Now, having said that: to accurately REMOVE an unwanted node in a performance space....(Taking mic and speaker placement into effect, you open a mic and as you increase the gain, you hear a resonant tone. You want to reach to your EQ and pull it out, yes?) You have to identify the frequency. By practicing with a 1/3 octave EQ and pink noise, you can listen to frequency bands. Enlist an associate to test you by doing the same thing, with pink noise as well as with swept tones.

Now...a 1/3 octave EQ is nowhere near as good or precise a device as a good parametric EQ, but once you are good with a 1/3 octave, the ability to dial exactly the proper freq, Q (width) and gain is an eye and ear-opening experience.

I hope this helps!!

JvB

[Nick_1234]

Danny.

I will check out MAPP, as well as SIM. I think those tools will serve a purpose in another thing I have going on. Thanks for the response, as it is much appreciated!

JVB.

The EQ I can probably afford as I can find one for $150 range. However I noticed that pink noise generators are not the cheapest thing to purchase as well. Any suggestions on a free RTA software that is worth using on my powerbook?

Or maybe some practice "drills" that I can do within Pro Tools at home. Mainly for freqeuncy recognition.

Respect.
-Nick

[Sound Chaser]

Originally Posted by Jim vanBergen

Now, having said that: to accurately REMOVE an unwanted node in a performance space....(Taking mic and speaker placement into effect, you open a mic and as you increase the gain, you hear a resonant tone. You want to reach to your EQ and pull it out, yes?) You have to identify the frequency. By practicing with a 1/3 octave EQ and pink noise, you can listen to frequency bands. Enlist an associate to test you by doing the same thing, with pink noise as well as with swept tones.

JvB

After specializing as a FOH engineer for 20 years I can tell you that if you tune a P.A. this way your in for a lot of trouble. There are 3 components for tuning a system and they must be done in a specific order. You have stated the third and least important step.

Step one: All zones (ie: sub, bass, mid and top) need to be interfaced and time aligned properly. In recent years this has been greatly improved with the advent of digital X-overs such as the DBX drive rack. They will also output a variety of test wave forms including pink noise and spectrum analysis. The crucial part in this step is to set each cross over point to interface with the natural response of the different drivers and still maintain phase coherency. For example, the horn will often have a different 'texture' and ballistic than the mids.
Step two: THE MOST IMPORTANT, is tried and true and the most ancient method. A P.A.'s job is to reproduce the human voice. If you do that along with aligning the components properly the response will yield excellent results on musical instruments as well. There is only one method to do this. You take the humble SM58 and talk into it with emphasis on vowel sounds and "p" and "t" consonants. You must make your voice as natural sounding as possible. IF YOU ONLY DO THIS YOU WILL HAVE A REASONABLY TUNED SYSTEM.
Step 3: is as you have stated. The purpose of this is to see the problems that arise if you open up the gain stage past the point of normal response. Feed back occurs when the microphones hear their own output (speakers) louder than their own input source, thus triggering sympathetic frequencies.

Though I still use Karke Teknic DN360's (1/3 octaves) many engineers consider them passe today as they introduce phase problems. Since they attack set points you are forced to compromise the actual offending frequency in relation to the natural response of the drivers. Digital EQ is far superior in this regard, but IMO you still need a physical fader when dealing with different acoustics every night. RTA's are only good as a visual representation. The absolute biggest mistake you can make is to set a flat response and expect the system to function properly. Swept tones are totally deceiving when aligning drivers at high SPL. Since the dynamic range of a live concert is so much greater than your studio monitors, I don't have to tell you what that does to your frequency loudness contour.

[Jim vanBergen]

Originally Posted by Sound Chaser

After specializing as a FOH engineer for 20 years I can tell you that if you tune a P.A. this way your in for a lot of trouble. There are 3 components for tuning a system and they must be done in a specific order. You have stated the third and least important step. .

Whoa nelly, let's slow down there and review.

I was simply suggesting he learn how to discern freq's by ear. NOT to try and align a sound system by ear!!!!

The original post referred to self-training at home for improvement on the job, NOT "how do I tune a PA."

So, as far as working with a 1/3 octave EQ, ----PLEASE don't misinterpret my suggestion to think anyone should learn with a full-blown PA!!! My idea of practice is in a private space, much like a practice or reheasal room is NOT a soundcheck or performance. If I was unclear or obtuse, then I retract my statement and apologize for the confusion.

Not to split hairs, but the word "TUNE" as nomenclature is really inappropriate even though it is commonplace. If you think you can TUNE a room, you're wrong. You can analyze, equalize, time align a system, after you verify the components of the system- you can hopefully learn to assess, align, and correct anomalies and problems in a room. Hence the reason we end up using brands of analyzers as a verb "to Sim a system, to Smaart a room". When someone uses the word TUNE they really mean sonically optimize for sound performance and/or reproduction, and that's really not what TUNE means- tune means to align harmonically, to adjust in reference to a particular frequency. For sound mixers or engineers to say TUNE a PA, what we really mean is: "to adjust so acoustic or electronic reproduction is optimal, and in harmony with the ideal listening environment."
That's just in case I was not being specific enough.

And before anyone is saddled with a job mixing for a living, they should get a couple of SMAART or SIM3 certification classes and understand a solid amount of math and physics before they start pushing faders for a living.

Hope I have corrected myself appropriately. If not, I'll be happy to try again.

[Nick_1234]

Both of you fellas make very valid points, and are each providing some useful information.

I am not always in the situations where I need to "correct" frequencies all the time. I work for an AV company and we get the live band here and there. As well as other time where I will get a 1/3 octave EQ for some wireless lavs. Which I have noticed are really touchy when it comes to feeding back.

I thank you guys for all your suggestions, I really appreciate them.

I think that I will get more experience with this if I find a bar/venue to do sound in a few nites a week. I just don't know if Im qualified enough.

Respect.
Nick