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[Jason Lucas]

If you're going to test the system, test it with all the mics in their usual spots.  It's OK to try it with a mic next to the sub or the mains, but that's not going to tell you how the system balances out under typical use.

Feedback frequencies will be position-dependent.  Often, if you move a mic 6 inches one way or the other, the feedback it was producing will disappear.  So if you set it up not to feed back by using a measurement mic right at the speaker, that doesn't mean you won't get feedback with the mic in another position.

Test in regular stage placement.

Test with ALL mics on.  When you encounter feedback, mute the mics one at a time to identify the culprit.  Deal with that mic.

In that case I should probably just have someone walk all over the stage with a mic, since stage placement changes frequently.

The sub feedback occurred even if only one mic was on. I'll test with all mics on anyway though, just for good measure.

[g'bye, Dick Rees]

In that case I should probably just have someone walk all over the stage with a mic, since stage placement changes frequently.

The sub feedback occurred even if only one mic was on. I'll test with all mics on anyway though, just for good measure.

So if you turn off the sub, does the feedback go away?  Same question for the mains.  If you turn them off but leave the sub on, does the feedback go away?

It still sounds as if something basic is not right. 

With aux fed subs, there would be no mics going to the subs, so it would be impossible for the scenario to repeat.

Hook up the system with the crossover.

Proceed.

[Thomas Harkin]

In that case I should probably just have someone walk all over the stage with a mic, since stage placement changes frequently.

The sub feedback occurred even if only one mic was on. I'll test with all mics on anyway though, just for good measure.

This is what you are doing to get your "aux fed" subs, right?

http://www.prosoundweb.com/article/a_detailed_explanation_of_the_aux_fed_subwoofer_technique/

[Jason Lucas]

So if you turn off the sub, does the feedback go away?  Same question for the mains.  If you turn them off but leave the sub on, does the feedback go away?

It still sounds as if something basic is not right. 

With aux fed subs, there would be no mics going to the subs, so it would be impossible for the scenario to repeat.

Hook up the system with the crossover.

Good question, I can try turning the sub all the way down and see (can't turn it off with the mains on).

@Thomas: Yes, that appears to be how we had the aux fed subs setup in the past.
Proceed.

[Jason Lucas]

Okay, so I had a chance to try a couple of things tonight:

First of all, there is a very noticeable difference in output levels between the left and right channels on the sub.

Second, when I had one speaker hooked up through one channel of the sub, I was able to walk all over the room holding a mic, including right up to the sub, with a HPF setting of 140Hz with no low end feedback. Below 150Hz was a little boomy for me but it was still acceptable. I didn't try going lower than 140.

So, what that tells me is that the high cut out on the sub is working perfectly fine on the one channel. So there's nothing wrong with using the high cut out on the sub.

So now what I want to try to do is run one of the JBLs through that channel, and then daisy chain the other JBL from the first JBL.

It turns out I might not need the crossover after all.

[Samuel Rees]

Glad you got it working. I'd want to do aux fed anyway, but that's just my preference where the situation is anything less than perfect. You could use 1 channel for the center cluster at least.

[Jason Lucas]

Glad you got it working. I'd want to do aux fed anyway, but that's just my preference where the situation is anything less than perfect. You could use 1 channel for the center cluster at least.

AUX feeding isn't off the table, I just want to see if I can get the system working right without having to do that.

Got a 100 ft XLR cable coming in the mail that I'm going to use to daisy chain the JBLs. We'll see how that goes.

[g'bye, Dick Rees]

AUX feeding isn't off the table, I just want to see if I can get the system working right without having to do that.

Got a 100 ft XLR cable coming in the mail that I'm going to use to daisy chain the JBLs. We'll see how that goes.

Aux feeding the subs IS the way to get it working right.  Keeping the mics out of the subs by feeding them only the LF stuff will put you way ahead.


You should really try implementing the advice you've been giving and stop wasting time trying to get along without it. 

[Jason Lucas]

Aux feeding the subs IS the way to get it working right.  Keeping the mics out of the subs by feeding them only the LF stuff will put you way ahead.


You should really try implementing the advice you've been giving and stop wasting time trying to get along without it.

AUX feeding doesn't appear to be the standard approach at all. I see very few people running AUX fed subs and they don't have any issues with LF and vocals.

If the system works fine without AUX feeding, why would it be necessary?

If, after I'm done testing, I find I'd prefer to go AUX-fed, I will.

I appreciate the help, I'm thankful for it, but I'm also going to try things out before I decide to change anything.

I don't believe any of what I'm doing right now is a waste of time. I'm simply troubleshooting. I'd rather find the cause for something than just apply a band-aid. In that sense I actually am following the advice given in this thread, I believe.

[Scott Wagner]

AUX feeding doesn't appear to be the standard approach at all.

For actual audio professionals, AUX-fed subs ARE the standard.  Your big complaint is that you have feedback from the vocal mics in the subs.  AUX-fed subs directly address this issue.  I don't understand your reluctance.

No offense intended, but your knowledge level is seriously lacking.  Those who have replied to you here have some serious credentials, and they know enough to know that even they don't know everything.  If you follow their advice, you'll have a much shorter path towards actually resolving your issues.  If you choose not to, prepare yourself for a long and frustrating experience while you learn the hard way.  We are here to help, but you have to actually allow us to help you.  Eventually, they'll stop trying.

[ProSoundWeb Community]