Intonation perception

jtlownds · #1 03-25-2007, 07:16 PM

I have been playing double bass for 51 years. Mostly jazz, but for the last 2 years have been playing with my church band, a blue grass gospel group. We have a couple of guitars, a mandolin, and the bass playing thru combo amps on stage, with the rest of the group going thru a couple of condenser mikes.

Last month, we had a guest band play at the church, all acoustic, the bass player (one of my students) tied an SM57 under her tailpiece and played thru the church PA. This was the first time that I got to sit in the audience and hear the mix from that perspective. I was blown away at what a great sound they produced.

I suggested to the church band that we ditch the amps. They agreed, and the difference is stunning. I had been using a full circle into an AI Contra. I replaced that with an AKG C419 condenser mike into the church PA. I can't hear myself in the monitors, but the congregation raves about the tone, and says that it is plenty loud.

Now to my question. When playing thru my amp, my intonation (to my ears) would run just a little sharp or flat. Nobody else noticed it, but it was bugging the hell out of me. Since playing acoustic, my intonation seems to be spot on. I don't understand this. I have a theory that maybe my amp was generating overtones in my bass, causing my ear to be off? Anyone out there ever experience this phenomenon? Drurb, you're a psycoacoustician, you have any thoughts on this?

farmerdude · #2 03-26-2007, 09:52 AM

..."I have a theory that maybe my amp was generating evertones in my bass"...

I would agree with that theory...

JazzCat_88 · #3 03-26-2007, 08:28 PM

I guess that the overtones are always present. They make an instrument sound like an instrument. Eg. a piano sounds like a piano, and a bass sounds like a bass. These all happen due to overtones. The amplification may accentuate the overtones. It goes like this: If you play a low E, that's about 41.2Hz. If you have a loudspeaker that only produces that frequency with no overtones, it will sound like a test signal. A low beep. With a good amplifier with a flat response you can get the same tone as your bass. Only louder. So you hear the overtones, that make your bass sound like a bass, clearer.
I don't think it is the fault of the amplifier. You are only hearing the problems now because the amplifier has magnified them.

Tim Skaggs · #4 05-19-2007, 08:50 PM

Considering your years of experience, I can't say that I could give much advice you haven't experienced. It sounds like your theory is probably correct. Some amps color basses with some very strange tones. If you play in front of your amp, you may be resonating your bass at some freq the strings alone won't due to lack of volume. It sound like your problem is solved anyway by playing through the PA.

moles · #5 06-07-2007, 02:41 PM

I meant to respond to this post when I first read it...better late than never I guess

You know, it may not have anything to do with overtones created by the amp. Its a known fact in audio engineering circles that a sound will be perceived as sharper the louder it gets. This is why recordists don't pump a whole lot of bass into a singers' headphones during a take in the studio, why arena rock bands originally started tuning down half a step when they played live (so the material would sound the same to the audience and not sharper - though personally I never would have thought anyone would notice, but thats the story I hear anyway).
My educated guess is that after 51 years of playing, your muscle memory has your intonation pretty dang constant - but when you're amped and louder, it sounds sharper than when you're unplugged.
I would really be curious to find out how this effect changes the further you get away from the amp - ie does the audience hear it a tad sharp when you're amplified also? Or is the effect lessened as the low frequency waves develop..?

boombloom · #6 06-07-2007, 06:14 PM

After about a dozen years playing upright, I recently added an electric upright to my herd. I noticed right away that my intonation sounded off. Interesting. I asked around and other folks thought it sounded OK. I was wondering if for some reason it's because the sound was coming toward me from somewhere else (amp) instead of projecting away from me out of my bass...

damonsmith · #7 06-07-2007, 07:48 PM

One thing I have learned is that "wrong" is often percieved as out of tune.
A different tone than what we are used to will sound wrong to us, it may or may not be out of tune, but we bassists are preconditioned to look to intonantion first.
Having said that, I have yet to hear anyone who's intonation is always "Spot on", so it could be hearing it through the amp is actually hearing the reality.
The other side of that coin would be that amplfiying is interfering with
the process you use get it spot on.

bluegrasscat · #8 06-07-2007, 11:43 PM

Quote:

Originally Posted by damonsmith

A different tone than what we are used to will sound wrong to us, it may or may not be out of tune, but we bassists are preconditioned to look to intonantion first.

this kindof sounds like, when you talk or sing into a recorder, and you play it back and say that, "that is not my voice", but your buddy says it totaly sounds like your voice!!

a mic seems to sound more natural than a amp.. or is it because when you amp it you dont have to play as hard to be loud? causing the intonation to sound different?

jtlownds · #9 06-08-2007, 10:51 AM

Thanks for the responses guys. I never experienced this phenomena anywhere besides this church, so it may just be the acoustics of the room. Nobody in the band or audience noticed it, but it was driving me nuts.

moles · #10 06-14-2007, 09:34 AM

Slightly related note here. I got my DIY pickup put together a couple of days ago, and last night was the first time I've really been able to jam and high volume. After sorting out all the feedback issues (I thought) it turns out there was still a low level amount that made the whole thing sound a bit out of tune. When I say low level I mean low too - like if I let it be the feedback wouldn't take off, just trail away - so I didn't realy notice it til I really focused on what was happening with the amp sound I was getting. It made the 'amp resonating' argument make a little more sense to me.