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Iain

Acoustic bass PA feedback

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Hi Folks,

Looking for some advice about dealing with feedback when playing PA-amplified acoustic gigs.

Gigs are in lively wine bars mainly so our trio use out PA for the guitars and VOX. Generally stage space is tight so I'm always in close proximity to the PA speakers and, as the night wears on the set livens up I tend to spend half the gig fighting feedback. Take last night - we had great balance at the start but the guitarist, who was on top vol from the start altered his EQ adding more bass. Wasn't until after the gig he admitted to this having watched me fight the feedback for the last 40 mins. We'll be having words...

Bass is a Breedlove Stage and the Phase switch helped to an extent. PA is powered speakers and a very simple desk, not monitors or other amps.

So, any devices or tricks that can help? Last night's problem note was F# so, in theory I could add a more flexible EQ to tune that out but that's not realistic to do mid-set.

Obviously I could move to using a solid body bass - I've a lovely fretless Warwick but the optics aren't great and I'd need to add some form of monitor for that to work.
I could break the bank and buy something like a Rob Allen MB-2 but the gigs don't justify the spend really.

We also discussed changing the mixer for something more modern that may have electronics in it capable of managing feedback though on-board DSP.

Help!

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have you tried a plug yet? they do wonders

https://www.amazon.co.uk/d/Musical-Instruments-DJ/Planet-Waves-Screeching-Acoustic-Soundhole/B0010SHU18

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I'd go with blocking the sound hole too, trying to fight the feedback on my upright was a thankless task and I've fitted a mag pickup in the end!

I've got an Ozark acoustic bass, it sounds really nice but it's impossible to amplify.

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agreed hole stopper would be my first port of call

alternatively have a look at a graphic eq pedal which would give you the ability to notch out the troublesome frequencies

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Thanks guys - hole plug arriving tomorrow, next amplified gig at the start of July so we'll see how it goes.

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[quote name='owen' timestamp='1496507048' post='3311985']
Buy a Rob Allen.
[/quote]

Clearly the best suggestion :) Also a tad out of budget.

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Use a solid bass. If you're playing amplified there is no tonal benefit in having an acoustic bass, and as you've discovered it's got plenty of disadvantages.

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[quote name='BigRedX' timestamp='1498553776' post='3325393']
Use a solid bass. If you're playing amplified there is no tonal benefit in having an acoustic bass, and as you've discovered it's got plenty of disadvantages.
[/quote]

Mmmm, don't entirely agree with this. I've used my Washburn AB20 with an eight piece band, and with careful positioning
of amplification I found I could [i]just [/i]get the level needed to sound okay, whilst retaining some of the inherent acoustic-ness
of the tone. Shoving acoustic basses through conventional bass amps does rob them of much of their signature sound,
but using them into a good PA can still maintain this IMHO.
I've gigged mine for years in an acoustic duo to good effect, usually with a small Yamaha / Bose PA for café / pub gigs.
Also use my Countryman bass uke for more upright tones too. :happy:

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Another option that has not been mentioned is to turn down the bass. Using a graphic EQ or a high pass filter (on the PA desk?) you can take out the bottom octave and probably not notice it has gone, except that your bass will be clearer and have more punch. If you use a variable high pass filter e.g. the FDeck design, you can take out more lows, and your sound will become more 'low-mids' focussed, but will be less likely to feed back and will still cut through. Finally, if the stage volume is still too much for you to cope with, go for a smaller-bodied instrument - my Countryman bass uke works long after I have given up with my jumbo-bodied Ibanez.

David

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has anyone ever had the peizo go straight to the PA and had a separate magnetic pickup for just the stage monitors? I wonder if that'd be much better?

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This is where a RTA and 31 band EQ on your PA can work. The rooms that you are in have resonant peaks - the 31 band eq will help solve that. Then, if there's any hot notes, which there shouldn't be because the RTA and tuning phase should fix that, you can then apply a separate notch filter (either back on the 31 band eq or a separate EQ pre the output) to the problem note(s). This should give you a lot more volume before feedback.

With regards to the bass, plugging the sound hole as suggested would be a good start. Ive seen guys with 335s fill the bodies with newspaper... that could be an avenue to explore if all else fails.

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[quote name='cheddatom' timestamp='1498568245' post='3325568']
has anyone ever had the peizo go straight to the PA and had a separate magnetic pickup for just the stage monitors? I wonder if that'd be much better?
[/quote]
A peizo on its own would need a high impedance which the PA input would not provide. If you had a buffer preamp, then you could feed into the PA, but the problem is the instrument's area of wood which picks up the local vibrations, and I don't see how having separate feeds to the PA and stage monitors would reduce that - am I misunderstanding your comment?

David

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Guest subaudio

The plug should help but if not, what I used to do with my upright in a loud band was, flatten the eq on your amp and turn up till it starts to feed back.
Asses what frequency is feeding back and cut it out till it stops using either the amp eq or your bass/preamp.

Then turn the volume up more till feedback and cut the offending frequency till it stops.

Keep doing this till your amp is at the volume you want.

You may not have the sound you want but its a balancing act.

Phase shift helps too.

Also make sure the pa is in front of you and position your amp where it feeds back the least.

I used to use a LR Baggs para di preamp and it did a fantastic job

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I used to play in a loud band (keys,sax, guitar, drums, 2 vox) with a Godin A5 semi bass and no issues. Secondhand they go for around £400ish, at least that's what i sold mine for!

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[quote name='Mottlefeeder' timestamp='1498580774' post='3325677']
A peizo on its own would need a high impedance which the PA input would not provide. If you had a buffer preamp, then you could feed into the PA, but the problem is the instrument's area of wood which picks up the local vibrations, and I don't see how having separate feeds to the PA and stage monitors would reduce that - am I misunderstanding your comment?

David
[/quote]

In my experience you get less feedback on an acoustic guitar when you go with the magnetic pickup as opposed to the peizo pickup. I'm not 100% sure on the science behind that but it's my experience.

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If you are getting feedback problems then you have a simple choice, turn down or sound s**t, in this case sounds like your guitarist needs to turn down.

There are a couple of things you can do to curb feedback generally. Often there are resonance spots in the room, so just moving to a different part of the stage can solve problems

Also moving your bass as far away from the speakers will help. You don't need any deep bass in the monitors so cut the bass there.

Try filtering any bass out of the vocal mic and the guitar. You'll probably have an 80Hz filter for each channel on your mixer

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[quote name='cheddatom' timestamp='1498638922' post='3325989']
In my experience you get less feedback on an acoustic guitar when you go with the magnetic pickup as opposed to the peizo pickup. I'm not 100% sure on the science behind that but it's my experience.
[/quote]
I have acoustic basses with peizo pick-ups and solid-bodied basses with magnetic pick-ups, but none have both, so I have no comparable experience to yours.

Possibly the magnetic pick-up majors on string vibration, while the peizo pick-up majors on body vibration if it is under the bridge and transmits string vibration to the body?

David

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I play in a band with a guitarist who plays acoustic. His acoustic has a peizo with preamp, and a magnetic pickup. If we use the magnetic pickup into the PA we can get it louder than if we use the peizo system. I'm not sure I have a good theory to explain so I'll not speculate but it'd be interesting to know

EDIT: I always expected a magnetic pickup on an acoustic to not sound very "acoustic" but it really does, it's ace, so it'd probably work for bass too

Edited by cheddatom
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Holy thread resurrection Batman

Thinking of adding a pickup to my Taylor mini Bass to increase my options. I get the idea I want to be looking at magnetic but struggling to find one for a bass. Any suggestions welcome.

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On 27/06/2017 at 09:56, BigRedX said:

Use a solid bass. If you're playing amplified there is no tonal benefit in having an acoustic bass, and as you've discovered it's got plenty of disadvantages.

Two years later and this is still nonsense, lol

  • Haha 1

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