Double Bass Live Sound Problems

[jb6884]

All -

I'm pretty clueless about PA Setup, and so is the rest of my group. I was wondering if anyone might share some ideas regarding our problem. Here is the setup:

Mackie 808M
2 JBL MPRO 15" Mains
2 JBL 12" Wedge Monitors
4 SM58's for Vocals
3 AKG C1000S's for Banjo, Guitar & Mando
Fiddle plugs in directly to the PA
I (DB) use an amp with no PA support usually

The problem is that we are not able to get very much volume out of the monitors before feedback.. in fact, the last gig was a near disaster because several of us could only hear ourselves and a little bit of whomever was next to us. Anytime we are in a real noisy room we have this problem. We've tried making sure the monitors are not in direct line with the mics, but still have the same problem. Thanks in advance

 

[JansenW]

Perhaps I can give you some suggestions.

Are you performing regularly in the same space? Do you have vocal or instrument feedback?

Your feedback is being picked up by your mics from either your 1) mains or the 2) monitors (or both). A louder setting would require you to raise the level of both your mains and monitors.

1) Mains: Are your mains in front of all your mics? In other words, all your mains should be closer to and facing the audience, and all your mics should be further away and facing away from the audience.

2) Monitors: Are all your mics facing directly away from the monitors? In other words, are all your monitors located in the dead spot (check your cardioid-mic polar patterns) of all your mics?

Most likely your feedback is from your instrument mics. You might want to replace the instrument mics with pickups (transducers) for the bass, banjo, guitar and mandolin. This would make the biggest diffence in feedback. Instrument mics work well for the studio but can be a pain in live situations.

 

[scottbass]

Monitor feedback is always a problem. We control (not solve) it by using a feedback eliminator from Behringer. You turn up the monitors until you get feedback, and this gizmo analyzes the feedback and takes small slices of those frequencies out of the monitor mix. The mains are still fine, and your tradeoff is missing a few narrow frequencies in your monitor mix in exchange for much more volume.

One word of warning - it's downright painful to intentionally induce the feedback and then let the gizmo find and eliminate it, so put your fingers in your ears, do it before the audience has arrived, and/or warn everybody what's about to happen.

 

[jb6884]

Are you performing regularly in the same space? Do you have vocal or instrument feedback?

No we play all over.. Usually the same place only once, sometimes twice in the same month. I would say there are a dozen places in our regular rotation of venues. Feedback seems to come from the C1000 instrument mics. I will check the deadzone, but they are faced away from both monitors and mains, and yes they are behind the mains usually by a couple of feet.

I don't like the idea of inducing feedback.. are there any gizmos out there that do it on the fly? Before feedback is audible?

 

[Gufenov]

A friend and I had the same problem with a similar setup. We solved it by ditching the C1000s for Shure PG57s - I would think SM57s would work well, too. Plugging in the instruments (guitar and bass) directly changed the tone too much from the acoustic sound we wanted.

We also tried the Behringer "Shark" Feedback Destroyer. It helped - some - but didn't allow the volume increase we wanted.

I've simply concluded that condenser mics are great for certain venues. Outdoors, or large facilities where stage noise can be kept to a minimum. We play a lot of small locales - coffee houses, nursing homes, church "multi-purpose" rooms. These often have many hard surfaces and poor acoustics in general. We stick with the dynamic microphones for these.

 

[mje]

I thinking using transducers for the instruments is a good idea. Sing close to your SM58s- that's what they're designed for- so you can keep the gain low.

Put some EQ on the monitors to get rid of the lows and some of the mids. You don't need to hear them.

Or get an in-the-ear monitor system. They're pretty cheap these days. You can get a 4-channel headphone amp for $100.

 

[mchildree]

If you like the sound of the C1000s, you might check the pattern setting and make sure they're set on the tightest pattern with the most rejection at the rear. Using condensers onstage pretty much guarantee that you'll need to cut your monitor volume, too. It's rarely possible to get the same monitor levels with condensers as you'd get with dynamics.

 

[jb6884]

I agree, I'd rather use SM57's or some other dynamic mic but I need to exhaust all options with the C1000's before i suggest to the guys they each have to drop another bill for new mics. We will try the hyper cardoid converters and the EQ suggestion. Thanks, and keep the suggestions coming!

 

[Uncletoad]

Another thought might be a perspective shift. I try to get the front of the house sounding its best before cracking the monitors on at all. I try to get everyone used to hearing it out front first and then add just enough monitor in front to get the definition. Doesn't always work with those that want in their face monitors but for those who want true acoustic sound its always best to monitor ones self with true acoustic sound first.

Quiet monitors are best.

 

[larry]

I have to agree that using condenser mics for live sound is asking for trouble. Unless the room is really good and you have some room to spread out, I would not even consider it.

I know it sucks to think about replacing mics, but I really think that is the problem. Try to find some used SM57's. Can't get cheaper than that while still being good.

 

[mchildree]

Now, I don't agree that using condensers for live duties is ALWAYS a problem. My band does 100+ dates a year and that's all we use. We play every variety of venue you can imagine...barbecue joint one night, 2K seat performing arts center the next, and somebody's back yard the next. We get lots of compliments on our sound. Here's some things we've done:

1. As mentioned, get used to monitoring yourself in order to keep the monitors as low as possible. You'll be amazed what that does for your vocal harmonies as well. It's one of the joys of playing acoustic music to be able to do this.
2. Make sure everyone is properly working the mics. Condensers are sensitive and everyone needs to discipline himself to back in and out when needed.
3. Always start with the eq flat...don't change it unless you have to, and that'll usually entail cutting problem freqs, not boosting.
4. The feedback eliminators haven't worked well for us. They do cut feedback, but they suck a much-too-wide freq range and leave you pretty toneless. Get a 31-band eq and get used to pinpointing problem freqs and pulling them down...only as much as you have to. Those Behringer things are the equivalent of taking a cannon to kill a bug...way overkill.
5. Don't assume you can set the eqs and leave it. Every room is very different. Start flat every time and work from there.
6. If you're using a bass amp, try to forego it. It makes it harder to hear. Get used to using the mains or just the sound of your bass, as mixed with the group. I've gotten to the point now where I only use an amp when we play places that have house systems that are too small for me to send my bass through the PA.

These are things that have worked well for us...not necessarily for others.

Edit: I might add that some condensers work better than others. We could not get the ubiquitous AT4033 to work well for us at all...feedback way before good volume. We switched to an AKG C3000 (the older black one) and it works great. We use one C3000 for guitar, banjo, mandolin and vocals, one C1000s for the fiddle and I send a direct signal to the PA.

 

[JansenW]

Excellent points.

 

[driver800]

Personally, I detest the feedback eliminators, though I have only used some of the cheaper ones.

the most effective way to minimize feedback while maximizing volume is to "ring out the monitors". it's best to do with a 31 band eq. the technique i use:

1. set all the eq bands to just below the center position.

2. turn up the monitor volume until you just begin to hear some feedback. then back it down just a touch so it does not feedback.

3. turn up each eq band individually. if you max it out and it does not feedback, return it to the center position. if it feeds back, set it well below the center mark. continue with each eq band until you've located and adjusted all bands causing feedback.

when I'm done, I'll sometimes repeat steps 2 & 3, but only with the bands set at the center position.

there are other similar methods for ringing out the monitors (google it) and the same can be done for the mains.

the "problem" freq. will usually be different for every room and every configuration used. It is also a good idea to warn people before doing this because it can be very annoying as you will produce feedback. However, it is very effective.

good luck.

 

[speedster]

Good sound guys/gals are hard to find and if it was easy there wouldn't be a need to have them for big concerts and festivals etc.

Having said that they are also very expensive for a small group and not affordable for a lot of smaller venues.

As I've been the lucky candidate to get stuck as the "sound guy" when we do small clubs etc I've read a whole bunch of books, magazines etc etc. on the subject.

Mic placement is always critical not only mic placement with the monitors but mic placement between each mic and mic placement from the mains etc. Phasing of frequency's always seem to start and a loop is realized which continues to amplify itself and hence feedback is a result.

Finding the culprit frequency's help and if your lucky enough to have a huge equalizer with lots of band width you can eventually usually drop the bad one or ones out but if you don't have lots of band width (lots of knobs) then you end up cutting lots of good frequency's with the bad and the sound turns to mush.

There are mathematical equations based on db levels etc that can be done too get you close to calculating your allowable head room.... its way over my head but can be done.

Bottom line is usually to get enough distances from mic's to main speakers, followed by enough distance mic to mic to monitor and finding your limit on head room for a given room.

Sometimes all it takes is to point the main speakers slightly out or into the middle of the room to remove the feedback frequency.

Experimentation is the key prior to getting going with the gig, and then just when you think you have it the audience fills the room and all the acoustics change....

Adding reverb increases the feedback responses, the double bass is always a culprit for causing feedback as it has such a large vibrating surface area, the banjo isn't usually a problem if the player has good right hand and we've used small condensors on the banjo and the mandolin with good luck.

The Shure 57's are always a good fall back though for either instrument.

I never run the bass through the monitors (too much trouble with feedback etc.) always use an amp on stage set behind the band facing the crowd, you can rig a mic to run to the mains if that is the sound you want but with a good amp and a good pickup (ie) underwood, realist etc you get a good driving sound lining out of the amp to the mains.

That elimination in the monitors alone gives you alot more head room on the volumes for the monitors and the mains and cleans up everything allowing the vocals to come through much clearer and the guitar frequency's to be adjusted easier without trying to figure out if it is the bass or guitar causing you the headaches.

I would never suggest putting pickups on the banjo and guitar if your after a "bluegrass band sound" or acoustic folk sound which it appears is where your coming from.

There are back issues of "Bluegrass Now Magazine" which have an entire section set out in them each month dedicated to doing acoustic sound by a Princeton or Wales Prof. who gives you all the background knowledge and math stats to go at the sound from a small group setting.

They are still available at reasonable prices the info is great and would sure go along way to pointing you in the right direction..................Cheers and good luck

 

[jb6884]

You guys have definitely given me a lot of things to try, so I will experiment and see if our situation improves.

I understand what you mean about harmonies.. I sing some leads, and a lot of harmonies - and it's a whole other animal when you can't hear the people you are singing with like you do acoustically at rehearsal. I typically try to stay in the back (life a bass player eh?) and lean in for harmonies on someone else's mic but we play some venues where I have to stand inline with everyone else and some of the guys I'm singing with are up to 10 feet away - that plus not being able to hear them through the monitors.. Yikes.. talk about leaving it to chance that the harmonies are going to come out at all.

 

[speedster]

I would certainly suggest trying to line out to the mains with your bass rather than cranking it up to fill the house off the stage.

You will undoubtedly gain significant head room immediately, remember that low end 12 - 20 k range frequency's are feeding each and every mic on stage and they then send that frequency back through the monitors etc...

Use your amp as your monitor, place it behind you up on a chair or milk carton pointed slightly sideways down the stage if your on the end as you say you are sometimes.

When directly behind face it straight out toward the crowd.

Roll a little bit of the bottom end off your amp (more so than the sound you like to hear on recordings etc.) That will help you pull it out of the mix. Give yourself enough volume on the amp to comfortably hear yourself and be able to relax and play.

Send the line out to the board and if you have a long cord like mine walk out front and set your main mix with everyone playing their instruments and you play the bass. Eq the bass and set the volume to a mix you like and then go back on stage and have at er...

It ain't a perfect world but I think you'll find that alot of your problems will definately go away...

Vocally the rest of the band will likely want to kiss you for the way the monitors clean up !!! That can be a good or bad thing depending on your bandmates....LOL

 

[Doug Ring]

If you like the sound of the C1000s, you might check the pattern setting and make sure they're set on the tightest pattern with the most rejection at the rear.

This might be the cause of your problem: this statement isn't true.

The "tightest" pattern is hypercardioid. It has a narrow pickup angle at the front of the mic...and a significant pickup from the rear too. A hypercardioid is meant to have the monitor placed off to the side of its rear lobe by 15 or 20 degrees, or even two monitors, one either side.

It's the cardioid that has most rejection at the rear, so with it you should place the monitor directly behind the mic. The penalty (there's always one, eh?) is that it has a much wider front pickup area.

It's best to find out what pattern your mics are and try siting your monitors accordingly before you go out and buy new ones.

 

[mesmithnm]

This might be the cause of your problem: this statement isn't true.

The "tightest" pattern is hypercardioid. It has a narrow pickup angle at the front of the mic...and a significant pickup from the rear too. A hypercardioid is meant to have the monitor placed off to the side of its rear lobe by 15 or 20 degrees, or even two monitors, one either side.

It's the cardioid that has most rejection at the rear, so with it you should place the monitor directly behind the mic. The penalty (there's always one, eh?) is that it has a much wider front pickup area.

It's best to find out what pattern your mics are and try siting your monitors accordingly before you go out and buy new ones.

Good point!!! I play in band w/a mando player that brings a C1000 to the gig. For the longest time, the mic was set up with its hyper-cardioid pattern and was always a feedback producer. I guess that if cardioid is good, hyper-cardioid is better But a quick look at the spec sheet for the C1000 shows that in the hyper-cardioid pattern, the response from 250-4000Hz at 180 deg (directly behind the mic) is about -10dB In its cardiod pattern, the rejection is -20dB. This is a huge difference!! So when our mando player switched to the cardiod pattern, the problems went away. If you take a look at the response plots Invalid Link Removed
it seems like that one will always be better off in most live sound applications with the C1000 set in the cardioid pattern unless you can very carefully control the monitor placement. The cardioid pattern will tend to be more forgiving if you get a little off-axis with respect to the highest rejection area of the pattern.

 

[WalterBush]

I believe your solution will involve replacing the C1000 mics. AKG and Audio Technica both have excellent lines of miniature condensor mics made specifically to be mounted on the bridge of a banjo/mandolin/DB/violin etc, or mounted near or in the soundhole of a guitar. I'd look into these. Since they're much closer to the sound source, they don't require as much gain, and aren't as affected by low-level stage monitors.

Having said that, I'll also cheerfully recommend you look into Sabine's line of feedback eliminators. They're a little less user-friendly (and much more expensive) than the Behringers, but the tradeoff is that they're much more accurate, transparent, and respond to feedback long before the audience will hear it, once they've been set properly. If you don't have the time to properly set a 31-band monster before each show, the Sabine units may be your answer.

 

[mchildree]

The points made about the patterns are accurate...I should have left of the word "tightest". The rear rejection is what I was trying to get to. Pardon me...

Something that make the instrument-mounted mics less-than-desirable is that you lose the ability to "work the mic". If there's not a damn good sound man behind the FOH, it only leaves the player with the option of playing lighter when he wants to reduce volume. On many acoustic instruments that causes a big tonal loss.