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Post subject: Feedback issues
Posted: Fri Dec 18, 2015 11:43 am
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So other than all the cool talk about gear and great photos of cool gear, there's lots of tech advice one can get from people with more knowledge. Brotherdave seems to have a wealth of knowledge on guitar/bass models/setups, etc and now I'm hoping Contracaller or anyone else on here can shed some light on a recent issue I/we've had with our Expo setup.

We've had them for over a year, about April last year we added a powered sub to our 3 Expo's for a little extra oomph on the kick drum. Life was good, worked for our outdoor gigs over the summer, loving life with these.

But now over the last 4 or 5 gigs I've had an issue trying to eq the system and have had to crank the midrange WAY down to avoid feedback. Let me start by saying changes to equipment, same mic's, wireless, guitars etc. Just to rule that out.

I've set up the PA in the same configuration regarding placement so nothing has really changed, just a new problem.

The only equipment that has been changed was a bunch of XLR cables. Since this is the only real change I've already ordered a packet of 5 "heavy" 20 gauge cables from Musicians Friend to rule that out. Not sure what gauge the others in question are but I know out of 6 that were bought 2 have already gone bad with the connectors.

So just wondering if I'm barking up the wrong tree by replacing these. I mean we need them to be reliable so the new ones will be good. But can anyone give an opinion on whether or not a low quality cable will really affect the sound system that much?

Remember, I'm doing this by the seat of my pants so no laughing at the simple stuff. :D


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Post subject: Re: Feedback issues
Posted: Tue Dec 22, 2015 11:07 am
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My first suspicion is that the EQ crossover for the subwoofer may be set too high. In other words, you want the subwoofer to enhance the kick drum, right? But the kick drum doesn't play any mid-range notes, so you don't want mid-range notes coming out of the subwoofer, especially if there are any microphones near the subwoofer to feed back that frequency. The cutover should probably be down around 150-250Hz. Any higher than that, and the subwoofer is playing frequencies that should be coming out of the Expos, not the sub.

During the summer, you were playing outdoors, where feedback rarely happens because the entire atmosphere of planet Earth is trying to eat your sound. Back indoors, I think that subwoofer is causing your problem.

I'm glad you got nicer cables. Good connections between the wires and XLR tips -- that's the important part that is often crappy on cheap cables. It's where the cables usually fail. But the cables won't cause feedback. Also, for good cables, are anti-intuitive as this may seem, better signal integrity comes from SKINNY cables. You want fat cables for passive speaker wires. You want skinny cables for microphones (and active speakers). Good shielding and good physical connections are more important than fat wires.

Think of electricity as if it were water. Get an eye-dropper and use it to deliver exactly one drop of water. That's your electrical signal going through a skinny XLR cable.

Now pull the rubber bulb off that glass tube that makes up the eye dropper and stick it in one end of a swimming pool, and try to get it to deliver one drop of water to the other end of the pool. More metal is not a good thing for carrying a tiny, wiggly signal through a wire accurately, any more than a whole swimming pool is good for delivering a precise drop of water.

Most of the time, feedback is acoustic. Sound comes out of a speaker, goes through the air, into a microphone, gets amplified and played out of that same speaker... louder... and gets picked up... louder... by that same microphone. Eventually the system can't play that sound any louder. That's feedback.

Your single-speaker sub playing mid-range sound is more likely to do that than the mid-range array of the Expos. Most active subs have an adjustment for the frequency of the cutover. You probably have it "maxed out", which means that instead of turning up the volume, you have turned up the high frequency being played by this speaker. Turn down the frequency setting.

And check all your mic stands to make sure the rubber feet are still good. If one is missing or if the metal foot pokes though it and touches the floor, that's a path for acoustic feedback. You don't want anything with a microphone connected to it to touch the floor. Isolate it with rubber feet or a piece of carpet. Do the same for feet of any guitar stand, since even an electric guitar can acoustically feed back if it is touching the floor without padding.

I hope this helps.


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Post subject: Re: Feedback issues
Posted: Wed Dec 23, 2015 6:39 am
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Thanks for the info Contra, I thought you would have some good suggestions.

Checking the crossover cutoff on the sub is a great idea. Something I may have never thought of but def makes sense in that it's adding mids where not needed. Our guitar player bought that and has it but I'll ask him to look at it and check for that setting.

I did get the mic cables late last week. The cables are a little heavier true, but the real difference can be seen/felt by examining the connectors on the ends. Much heavier duty ends and they really "click" in with a more satisfying connection. Whether it caused feedback or not a better connection is still a good thing.

I will have our singer check his mic stand, he is the only one that uses the round metal base kind. The guitarist and I have the foldable kind and I know the rubber feet are on those. As for guitar stands we only plug in one each at a time, no connections to others sitting on stands so those shouldn't be a contributor.

I really think the sub may be a huge part of it since we added that after last spring/early summer. It makes sense.

Thanks for the info, appreciate it, I'll let you know how it goes. Our next gig is 1/1/15, next Friday so will get to try this out.

Have a great Christmas too!


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Post subject: Re: Feedback issues
Posted: Sat Dec 26, 2015 7:12 am
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So I got the info from our guitar player on the powered sub.

Contra, here is the link to the subwoofer, any recommendations on how to set this up to be sure that I am killing all freq's except the low's that we want?

Thanks for your help.

http://www.sweetwater.com/store/detail/B1200DPRO

My thought is setting at 90 hz with boost on to boost the lows, and set the high cut @150? Am I barking up the right tree?


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Post subject: Re: Feedback issues
Posted: Mon Dec 28, 2015 2:45 pm
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Sounds good. Mostly, make sure the High Cut switch is ON. I would think 150 should be low enough, but you can experiment anywhere from there to as low as noon (straight up) and see what the sound quality is.

If the High Cut switch were off, I'd expect it to play high frequencies that aren't being cut. You should be able to boost anything low you like. That shouldn't give you mid-range feedback.


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Post subject: Re: Feedback issues
Posted: Mon Dec 28, 2015 2:52 pm
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Thanks for the reply. We are playing this Friday so I'll be doing some experimenting for sure!

Appreciate it! 8)


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Post subject: Re: Feedback issues
Posted: Sat Jan 02, 2016 10:19 am
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Well last night we played at one of our favorite local bars.

I was sure to set the high cut to on on the powered sub and set the cut off at around 100.

The only real change I had to make eq wise was a little low end out of the vocal mic's, and we were golden. We did get some comments from our "regulars" that the sound was really nice last night so the work, time, and playing around made a difference. They described the sound as more "full" or a nicer "presence."

One downside to the night, we had everything plugged in and ready for soundcheck, after about 2 mins my amp, my nice new Rumble 500 started making this bad buzzing, no output, just noise. Really!? So I checked and swapped out a cable, but I also noticed that even with my wireless transmitter for my bass turned off the receiver was lit up, picking up something. So back to a cable for the bass!

After that hiccup it was a fun and trouble free night.

Thanx again for the info and assistance Contra, can't tell you how much I appreciate it.


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Post subject: Re: Feedback issues
Posted: Wed Jan 06, 2016 11:46 am
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Wireless mics and pickups are going through troubling times. How old is your wireless system for your bass? According to info on a mailing list I'm on:

"As of June 12, 2010, use of wireless microphones (and similar devices certified as *low power auxiliary stations*) operating in frequencies between 698 and 806 MHz (the 700 MHz Band) is prohibited."

Basically, the government agency in charge of deciding what frequencies are used for TV, radio, WiFi, radar, our mics and instruments, etc. have changed the standards in 2010 and will likely change again soon. Each time they change, the FCC's advice is to throw away our old gear and buy new stuff that uses the new frequencies.

Charming.

What's a few hundred dollars among friends, right?

Anyway, if you look at the manual for your unit, there's probably a procedure for testing a channel at the receiver to see if something is using it while your transmitter is turned off. If so, change the channel on the receiver until you find an unused channel, then change the channel on your transmitter to match the receiver. Most of these units can be configured to use a range of 10 or more channels.

... or throw away your wireless unit and go buy another one that uses government approved frequencies. We don't want to be outlaws, right?


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Post subject: Re: Feedback issues
Posted: Fri Jan 08, 2016 8:39 am
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Funny thing is I must be in outlaw territory.

My bass wireless is a Samson that I bought when my older daughter was a couple months old. She's now a freshman in college! So based on age alone I'm fairly certain I'm in prohibited frequency range. It's so old there's no settings for different channels, turn it on and go.

It's a basic true diversity system that's performed very well for many years, I know it's time but I've been buying other toys.

Anyway, your other info was helpful and wanted to let you know.

Our vocals were loud and crisp, makes singing on key much easier. And for the first time in awhile I was able to sing/play without the added stress, really enjoyed the night.

Let's see if I can share this video. The owner is a really good guy that pays us well considering the size of his bar. The bartenders are great ladies and we always play Brown Eyed Girl for them, yeah, a tired old standard but if you're in it for fun then you do things like this. So here's the owner Jay playing his "big drum" with us.....at least he's got some rythym!

https://www.facebook.com/jackie.hendrickson.94/videos/10153695637413046/


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Post subject: Re: Feedback issues
Posted: Wed Sep 13, 2017 11:06 pm
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Interesting post learned something new today. :mrgreen:

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Post subject: Re: Feedback issues
Posted: Sun Sep 17, 2017 2:05 pm
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So I'm back again to pick the brain of a valued expert, ContraCaller. 8)

So one of our Expo's went belly up, prohibitive cost to ship and repair and with members leaving and taking another with them we were down to one, so.....

We now have 2 1200 sub's and 2 Mackie Thump 12" for our mains, seems like pleny of power and our first couple gigs with them have gone well....BUT

One issue, I seem to have alot of my bass that "bleeds" into the tops/Mackie's, enough to distort them if I hit a low "E" unless I EQ the crap out of the bass. I have the high cut on on the subs, and I'm using the "output" from the sub to the tops because if I understand the manual the hi-cut doesn't affect the "through" jacks. Hope that makes sense. I've turned that high cut on the two subs down to 1/4 of the way, 9 o'clock for reference and I still have alot of bleed through. I've also turned the low end way down on the Mackie's as a way to help eq the bleed over bass to them.

I'm not one to like a "funky" and too bright bass tone. As a 3 pc group I think the lower thump helps me to add bottom end and help the group not sound so thin when the guitarist is soloing.

So, if you have any advice on that situation I'd appreciate it. I've read the manual but not much there, and I've been experimenting but still not found the sweet spot.


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Post subject: Re: Feedback issues
Posted: Wed Sep 20, 2017 8:21 am
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The main issue here is that so long as you send everything to the subwoofer and rely on its crossover to feed the Mains, you are at the mercy of the sub's crossover. It's a tough job to do well, and some sub makers do it poorly.

The better approach is to try to control the sound before it gets to the speakers with separate output channels. Unfortunately, your mixer only provides one output for the Mains and another for AUX, and you probably want AUX for monitors.

If you gave up the monitors and put the house speakers high and behind you to get your monitors from them, you could use AUX just for the bass instruments (kick drum and bass, mostly) to get a little more control on balanced sound.

The best world would be a mixer with more output channels, so you could get a separate mix and separate EQ controls for the subs.


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Post subject: Re: Feedback issues
Posted: Tue Sep 26, 2017 7:10 am
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Thanks for all you input CC via messages.

I have several options that I'll be trying, I believe if I get a better handle on the gain staging I can make the problem better, but in the meantime I'll run through some of the options we discussed.

You da man! 8)


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