How to stop feedback on string bass?

1 - Get away from the moniters and guitar amps.
2 - Get a hair scrunchi and put it around the neck and strings on the peg board side of the nut until crazy volume gives you that sympathetic vibration and then flip the scrunchi over to the playing side. This will dampen the open strings and decrease this sympathetic vibration.
3 - low pass filter or notch filter

 

a) tennis ball (or towel) between the tailpiece and the top table (body).

b) I think high pass filter (low cut filter), not low pass filter? is that correct Grant?

 

If the source of the feedback is the bass signal itself I would say a high pass filter could help, but what the OP is saying is that the volume of the guitars is causing the strings to vibrate and feedback generated from the open string harmonics. In this case I'd say a HPF would do nothing, but a low pass filter or a notch filter in the higher frequencies may filter out some of the harmonics preventing the feedback from starting.

 

Magnetic pickup if you're using steel strings.

 

Ah, got it. Thanks Grant.

 

It will not sound "zactly like it did" but try a Krivo pickup. More speakers will also help. I can stand right in front of my Ampeg 410, 115 stack and play LOUD without feedback. I have a cheapo plywood bass, my guess is that the better your bass is acoustically, the worse it will be for feedback when amplified. this picture has been here before but shows my point.

 

One thing I've noticed that helps is a smaller cabinet, so a my MAS 1/8, an Acme Low B-1, or the Euphonic Audio 1/8's are a little less prone to feeding back

 

As you already know, the settings that need to be tweaked are not at the bass amp...

When strings vibrate, the air moves the top and the bridge moves with the top and sets a string with a similar frequency or harmonic on it in motion.
Sometimes turning the bass into a different direction will help (or moving the loud speakers in a different place or pointing away from the bass).
Stuffing the f-holes with foam reduces air resonance and can help but doesn't need to. Tennis ball between top and tailpiece influences the top resonance and can help too.
You need to try things and be prepared that what works on one location might not work on a different one, so try it all, be prepared to have all things with you so you can change on the fly at the soundcheck if needed.

 

Also check this thread.
Phase shift and high pass filter help significantly fighting feedback.

If however the sound from the guitar amp resonates your bass body so it amplifies the guitar more loudly than the bass itself, then the preamp would help only too little. (This happened to me once when I was playing with a bass synth geek; I wouldn't believe it can happen otherwise. It wasn't even such a big volume.)

Try position the bass sideways to the guitar amps. Little turn or little move can help a lot. Count with spending an extra hour of sound check with this. Explain the band that it's not just your problem, but that all of you need to find right places for all the amps or the bass gets killed. The best would be convincig your partners to play more silent of course.

 

I'd be sorely tempted to cut some guitar cables.

 

Friendly amendment: and monitors

 

Try a wet towel.
Rattail the guitar players.

Rat tail!

 

Notch filter.
Empress makes the Para eq.

 

Toad's Rules from 10 years ago:
Stopping Feedback in LOUD Settings

 

You'd be surprised how much will be eliminated with a smaller cab. If you are going direct then you just need enough volume to hear yourself.