Setting up EQ manually

[ackcheng]

Recently I came across a setup method for room correction using positive feedback as follows and wonder if anyone can give me some feedback

1. Lower each individual frequency by 12dB on the EQ and increase the total gain by 3 dB
2. connect the microphone to the mic preamp and than to the EQ
3. Increase the vol of the preamp until positive feedback
4. reduce the total gain on the EQ from 3 bB to O
5. So far we have made the preamp just about to have positive feedback
6. Now, starting from the high frequency, slowing increase the gain from -12dB to 0 dB and above until positive feedback
7. Once positive feedback is heard, the gain is stop and lower by 3dB
8. Setup the same way for all frequency and for each channel separatly.

Does this method work?

[chris ma]

Hi,

If you are using digital EQ, may I humbly advise you to post same thread in the digital forum as well. My be one for the video forum just in case your EQ is used for HT.

Hope this can help,
Chris

[tiroth]

While it will probably work to some degree, I would think the likelihood of feedback depends a lot on the phase of the various signals, not just amplitude. Since the phase is not constant for every mechanical and electrical part in the measurement chain, you will probably not be equally likely to get feedback for a given amplitude at all frequencies.

Lowest feedback != flattest EQ

Why go to the trouble of this dubious technique when you could just use 1/3 octave warbles or filtered pink noise?

[ackcheng]

Actually I am using DEQ 2496 but I found that if I use its auto EQ function, the sound is still not balanced after the function!

[tiroth]

I have noticed this as well, warbles don't measure flat even after DEQ2496 pink noise FFT looks flat. I have yet to break out the big guns and do a MLS analysis.

Obviously you can measure the spectrum by some other means if you know this, so I recommend you use that to set the EQ if you feel it is more reliable.

[azira]

Originally posted by ackcheng
Recently I came across a setup method for room correction using positive feedback as follows and wonder if anyone can give me some feedback

1. Lower each individual frequency by 12dB on the EQ and increase the total gain by 3 dB
2. connect the microphone to the mic preamp and than to the EQ
3. Increase the vol of the preamp until positive feedback
4. reduce the total gain on the EQ from 3 bB to O
5. So far we have made the preamp just about to have positive feedback
6. Now, starting from the high frequency, slowing increase the gain from -12dB to 0 dB and above until positive feedback
7. Once positive feedback is heard, the gain is stop and lower by 3dB
8. Setup the same way for all frequency and for each channel separatly.

Does this method work?

I don't know if this is the right method to be using to tune a room. I use basically the same method to tune a PA system for a live show. The idea in that setting however is to be able to play your system and more importantly your stage monitors little louder than it would otherwise be able to before the onset of feedback.

What you're doing is notching out the specific frequencies that are resonant in the room not correcting for a flat response. In live show setting killing feedback so you can increase volume is slightly more important than perfect fidelity. But at home, it's the other way around, for one thing you won't have feedback issues due to microphones.
--
Danny

[Ken L]

Originally posted by azira
But at home, it's the other way around, for one thing you won't have feedback issues due to microphones.

Yep, I agree.

I was thinkng the same thing when I read the first part of this thread.

Feedback through a microphone and reproduction of live sound are two different animals.

If the DEQ will function as an Independant RTA, use ir or borrow or rent a RTA. and EQ manually what is correct to your ear using the RTA to get starting points.

Or if you like, use the Auto - EQ setting as a start - lower DB and narrow the Q settings - What you want to do is _remove_ EQ as long as you keep getting improvement that sounds good to your ear.

When you've got it sounding pretty good, listen to it over a few days or weeks, and make only very small adjustments. Make sure you listen to a lot of different types of music.

It will just take a while - but it'll work _grin_

Regards

Ken L