Setting up 31 band EQ

[Cliff]

What is the difference between using the ringing out the monitors method of setting up an EQ and the Tone generator method.

Or even using pink noise?

Don't they all find the hotter frequencies which you then lower on your eq?

[Brad Weber]

Originally Posted by Cliff

What is the difference between using the ringing out the monitors method of setting up an EQ and the Tone generator method.

Or even using pink noise?

Don't they all find the hotter frequencies which you then lower on your eq?

Perhaps there is some confusion between the 'ringing out' of monitors and the 'ringing out' of wiring using a tone generator.

'Ringing out' monitors is usually referencing improving gain before feedback and can include applying equalization as well as the locations and aiming of mics, speakers, nearby boundaries, etc. The equalization applied is usually reducing the offending band levels (equalizer bands, not if the band playing is offensive, that's a different aspect). However, there are also other aspects to the overall equalization for monitors and different potential approaches that can be applied to that and 'ringing out'.

'Ringing out' wiring relates to identifying specific wires or conductors. Typically, a tone generator is applied at one end of the cable or conductor and then by using some type of receiver device such as an inductive amplifier probe one can identify that cable or conductor at the other end or potentially at any point along its length by listening for the tone. Say you have a bundle of cables from the stage to the mixer and they are unmarked, you 'ring out' those cables by putting a tone generator on a cable at one end and using a probe on the other end to listen for the tone, thus allowing identifying the other end of that cable.

Does that explain it or did I misinterpret the question?

[wogster]

Originally Posted by Cliff

What is the difference between using the ringing out the monitors method of setting up an EQ and the Tone generator method.

Or even using pink noise?

Don't they all find the hotter frequencies which you then lower on your eq?

For EQ what you really need is a stepped frequency sweep, which should match your 31 bands, where say it gives you 15 seconds of each frequency then moves to the next, you monitor the sweep making notes as to where there are issues, then go to your EQ make adjustments, then go listen again to see if those issues are resolved, then go to another spot and listen. You will rarely get issues in the middle of the room, but that is where you start, then move around the room, walls and corners will have potential issues, as will the leading edge of a balcony. Treat the walls around a balcony as two separate places, one downstairs another upstairs. Yes this might be a full day project. It's almost impossible to get it so there are no issues anywhere, but with a room full of people, they will probably be less then with it empty.

Once your done, do one of two things:

1) Make notes as to where each slider is located or take a digital photograph.

or

2) Get a cover plate that fits over the EQ, and screw the cover plate in place.

If you don't tone some idiot will come along and change them all for you, so that it all ends up sounding like a dollar store AM radio.

[Brad Weber]

Originally Posted by wogster

For EQ what you really need is a stepped frequency sweep, which should match your 31 bands, where say it gives you 15 seconds of each frequency then moves to the next, you monitor the sweep making notes as to where there are issues, then go to your EQ make adjustments, then go listen again to see if those issues are resolved, then go to another spot and listen.

The points about the effects of equalization potentially varying throughout the space are very good, however for type of equalization described I would much rather use a random broadband noise source or a source that represents the normal program content as those can also address more complex issues and band interaction.

I think an important factor is that how you might EQ the house and how you would typically EQ monitors may be different. Another common issue in regards to monitors is to 'ring out' the monitors on an empty stage only to have things change significantly during actual use, the closer you can come to emulating the situation during use, the more likely for any adjustments made to be relevant to the actual use. A similar issue exists for house systems where it is common to tune systems a bit 'bright' for an empty room to compensate for the effects of an audience.

Another common occurrence is to watch people try to equalize out things that can't be fixed with EQ. For example, on stage a reflection from a monitor speaker off the floor, a music stand, etc. arriving at the microphone could cause cancellation or summation at certain frequencies. Since that is a result of the relationship of the direct and reflected signals and any equalization would affect both equally, you may be able to increase or decrease the level by applying equalization but that will not alter the summation and cancellation effects. Thus the proper solution for such situations is to address the phase and level relationships of the direct and reflected audio signals, for example trying to absorb the reflection or using the microphone pattern to increase pickup of the direct sound and reduce the indirect or reflected signal level.

The stereotypical example of of these coming together is a tech ringing out the monitor system in advance only to experience feedback once the performance began that they had difficulty resolving with equalization. The problem turned out to be reflections from the monitor speaker off the broad brimmed hat the vocalist wore for the performance. As they brought the mic up to their mouth the resulting reflections would sum at certain frequencies causing feedback at those frequencies, while the summation frequencies would vary as the singer moved the microphone or their head.

[wogster]

Originally Posted by Brad Weber

The points about the effects of equalization potentially varying throughout the space are very good, however for type of equalization described I would much rather use a random broadband noise source or a source that represents the normal program content as those can also address more complex issues and band interaction.

I think an important factor is that how you might EQ the house and how you would typically EQ monitors may be different. Another common issue in regards to monitors is to 'ring out' the monitors on an empty stage only to have things change significantly during actual use, the closer you can come to emulating the situation during use, the more likely for any adjustments made to be relevant to the actual use. A similar issue exists for house systems where it is common to tune systems a bit 'bright' for an empty room to compensate for the effects of an audience.

Another common occurrence is to watch people try to equalize out things that can't be fixed with EQ. For example, on stage a reflection from a monitor speaker off the floor, a music stand, etc. arriving at the microphone could cause cancellation or summation at certain frequencies. Since that is a result of the relationship of the direct and reflected signals and any equalization would affect both equally, you may be able to increase or decrease the level by applying equalization but that will not alter the summation and cancellation effects. Thus the proper solution for such situations is to address the phase and level relationships of the direct and reflected audio signals, for example trying to absorb the reflection or using the microphone pattern to increase pickup of the direct sound and reduce the indirect or reflected signal level.

The stereotypical example of of these coming together is a tech ringing out the monitor system in advance only to experience feedback once the performance began that they had difficulty resolving with equalization. The problem turned out to be reflections from the monitor speaker off the broad brimmed hat the vocalist wore for the performance. As they brought the mic up to their mouth the resulting reflections would sum at certain frequencies causing feedback at those frequencies, while the summation frequencies would vary as the singer moved the microphone or their head.

Your right, not everything can be fixed with EQ, however getting the room tuned for EQ, means that if an issue that crops up, it probably isn't something that can easily be fixed with EQ. Really, I would prefer to have a professional sound engineer to come in to get an equalizer or DSP set up. However, the church doesn't always have the budget for that, so the poor church technician needs to set it up the best he/she can. The reason I suggest a stepped frequency sweep using the same frequencies as the EQ device uses, is that it allows the tech to see what frequencies in isolation cause issues, if you can get those dealt with, then there probably isn't much else you can deal with using EQ, so you need to use other techniques to resolve the issues.

Your feedback example is one of them, there isn't anything you can do about that hat, with a 31 band equalizer, because your not going to have a clue what to change to make it work, unless of course you have been tuning EQ for several decades and have a piano tuners pitch.

[Brad Weber]

Originally Posted by wogster

Your feedback example is one of them, there isn't anything you can do about that hat, with a 31 band equalizer, because your not going to have a clue what to change to make it work, unless of course you have been tuning EQ for several decades and have a piano tuners pitch.

In that case there isn't anything you can really do with an EQ regardless of experience and addressing such situations effectively does not take special tools or skills, just a little thought.

When addressing gain before feedback think about what is actually causing the feedback, things like how the microphone, which may have some directionality, relates to the monitor speaker (which is also directional), amps on stage, reflecting surfaces, etc. And before reaching for the equalizer think about where you may be able to affect the feedback by moving/reaiming a speaker or microphone, changing to a different pattern mic, covering up or moving a reflecting surface and so on. In terms of increasing gain before feedback, equalization should usually be the last step rather then the first.

[Tim Padrick]

Problems are seldom at the center frequency of an EQ band. Problems are most often quite narrow. As such, using a stepped frequency sweep they would likely be missed completely.

[pdc]

+1!

I can solve more problems (usually) with less bands on a parametric, all pass filters, etc.