Site Logo

Bass feedback

Bass Fiddles

Why do I poke around with my gear? It boils down to three things.

1/ If I hear my bass sounding good, I feel good, I play better. I refer to the sound of my bass in the place where I am standing to play it on stage, at the same distance from the ground as my ears. If there's a good bass sound cutting through where my head is, I can enjoy playing with the band.

2/ I don't play an entirely acoustic instrument; it depends on amplification, which is a significant part of the bass sound; that is, a significant part of my instrument.

3/ I often play a venue which defies any attempt to control my sound, and I suddenly feel poorly equipped to do the job properly, and from then on I am distracted.

Certainly, some rooms will always defeat live music, but this page gives indicators of what I might expect from a venue, as a kind of tool to help me through the night, and perhaps you too.

Easily Led

I'm sure I'm not the only musician whose playing responds positively to a good sound. And if the audience gets the idea that something's cooking, and responds in kind, this also feeds back, and it's going to be a good night.

So my poking around is also a response to feedback from the show. Perhaps it would be better if I knew what the band sounded like from the front of the house, a truer(?) perspective of the sound, and my part in it, but I never will know that sound. What I hear is often a gross distortion of the truth, for many reasons, mostly only to do with bass instruments, as opposed to "treble" instruments.

A Brief History of Tone

A real double bass has a huge soundboard backed by a voluminous cavity to give its warm vibrant sound. But the study of physics tells us that the strings are too short, and the body too small, that it is a compromise. The uniqueness of its tone and expression has battled over the years with its inconvenience in size, projection and amplification, to lead to the evolution of the bass guitar, and eventually, the electric upright bass. Along the way, also for our comfort, it has changed from a hand-carved, tuned enclosure, to a mass-manufactured assembly of bolt-on parts, and inevitably, produces a very different sound to its forebear. At its debut, the bass guitar sounded so dissimilar that it became very quickly an instrument in its own right, and stopped "bowing" to its ancestor.

Without an amplifier for support, it is apparent that there is very little "tonewood" or "soundbox" available to offer any "bassiness" or "bottom-end" to its tone. Even in hybrid instruments claiming "authentic" reproduction of the double bass, almost all the bass comes from electrical boosting from the instrument's preamp or its amplifier.

Bassy sound comes from big instruments, but of course, then we get problems from lack of volume and feedback headaches, which is why the thing got shrunk in the first place.

There is nothing particularly bassy about a magnetic bass pickup, or a piezo pickup, or a microphone. Either device can amplify violins as easily as basses with little discrimination. For use with a bass instrument, an amplifier or preamp provides the simple reduction of high frequencies by filtering allowing low frequencies to be more prominent. Tone controls are often elaborate, but most of my sound is a balance between the volume knob and the bass knob.

Potential feedback paths at a venue

Do's and Dozens

The list has grown from playing many gigs in questionable venues, noodling with different basses, amps, speakers, pickups, and more recently, being able to record at home, with the luxury of free high quality tools, and the opportunity to pick up on techniques handed down from studio engineers.

1/ Proximity effect applies to instruments amplified by unidirectional microphone, causing over-production of some low notes.

2/ Bass traps. In studios, we learn that room corners are stuffed with foam and rubber "bass-traps" to get a grip on the bass sound. In a small venue however, either my ears happen to end up in one corner of a room, or my amp and speaker likewise, or both, and I know that bass sounds are going to go crazy in those areas, so I restrain myself from gratuitous twiddling and try to get opinions of people out in the room. Sometimes I can spread the bass signal (D.I.) to the p.a., but again, small venues mean small p.a. systems, which may not handle bass so well.

3/ Acoustic feedback, for bass, is simply the effect developing from leaving the instrument turned up and unattended; a string starts vibrating, and is sustained by the same note from the speaker pushing the air around enough to keep the string moving indefinitely. Sound waves from the speaker are transferring energy back into the string causing the endless sustain of the fundamental note. However the amount of energy transferred depends on the proximity of the player to the speaker, the proximity of these contributors to a wall, or to a corner, the size of the room. A piezo pickup with a peaky response will cause higher notes to be similarly sensitive.

4/ Mechanical feedback is experienced more by electric upright bass players than bass guitarists, through the one part of this instrument which the bass guitar lacks, the spike.

A wooden stage is rather like the soundboard or table of a double bass, very capable of transmitting and amplifying low frequency sound. It can send mechanical vibration through the spike into the strings again, just like acoustic feedback.

It would make sense to a) isolate the instrument from the floor, and b) isolate the bass speakers from the floor. A very effective method for both these steps is a pair of huge paving slabs. One for the speaker to sit on, and one under the spike. Only once have I attended a gig where the sound engineer was prepared for a spiked bass showing up, and had managed to bring along a portion of his neighbour's patio.

On a good p.a. desk, the engineer might have other tricks which can be brought to bear, like a compressor or graphic equalizer. The p.a.'s real advantage though, is that its speakers are relatively distant from the player, one hopes, and are sat on another floor level, one hopes.

For myself, it would definitely be an advantage to have good control of the amplified bandwidth specifically for my desired sound, which is why I have to sort and prune these thoughts on a web page!

I have to do something with the Em's T-foot