Another amplifier question: acoustic guitars

Is there a good scientific explanation for why an acoustic guitar with a pickup sounds so much better plugged into a bass guitar amp than plugged into a guitar amp? To my ears, anyway, an acoustic guitar run through an electric guitar amp sounds clangy and extremely harsh, but run though a bass amp it sounds crisp and clean, like it’s supposed to.

There are a couple factors I can think of:

• The physical speaker/driver is much more essential to an electric guitarist’s sound than to an electric bassist’s sound. This is one reason it’s fairly common for bassists to plug directly into the mixing board (both live and in the studio), while guitarists prefer to mic their cabs. I’ve noticed that a lot of time if there’s a bass guitar amp on stage, it’s pointed at the bassist, not the audience; the bassist’s main signal is going through the house system, and the amp is just there for the bassist’s benefit.

• Bass amps and cabs are usually designed to avoid “coloring” the tone of the instrument, and this factor is also desirable when amplifying an acoustic guitar.

Basically, to my ears anyway, an acoustic guitar plugged into a regular guitar amp ends up sounding like an electric guitar, but plugged into a bass amp it sounds like an acoustic guitar.

It’s also worth noting that I’ve come across a number of amps that are sold as being "bass/acoustic guitar " amps, which lends credence to the idea that similar amp characteristics are desirable for both bass guitars and acoustic guitars.

There are plenty of acoustic amps out there , never seen one for bass/acoustic. My acoustic sounds fine played through my Mesa Boogie amp but I have never tried a bass amp.

I’m not the best person to ask, because I hate the sound of a quacking Piezo-electric pick-up more than the teeth of death. This strong prejudice renders about 98% of the folk, rock and blues played in the last 20 years irritating to me. Can’t help it, though; I hear that ‘Sprak’ of the first chord and I just cringe.

That all being said, electric guitar amps are built to shape the sound as well as amplify it, and electric guitars often play in a higher register than an acoustic. Even when electric guitarists play the open low ‘E’ string, they may well be wanting more overtones than would be natural for an acoustic guitar.

In contrast, most people want to hear the natural sound of an acoustic guitar, just louder. That’s harder than it might seem; all amplification imposes a certain amount of change to the timbre of the sound. Bass amps don’t necessarily add a lot of treble to the sound, so they might sound closer to natural. I’ve never tried an acoustic through a bass amp, so I haven’t noticed that of which you speak.

I prefer keyboard amps, such as the Traynor K2 or K4 - in fact, the K4 is my amp of choice, but there again, keyboard players don’t tend to want the amp to change their sound - they want to do all that modification at source and have the amp faithfully reproduce it. That’s why doing something like putting a distortion pedal on the line between your Fender Rhodes and the amp seems like such a crazy thing to do…

My $.02…

When you hear an album they could have miked the acoustic guitar rather than using a built in piezo pickup. For live shows they normally plug in but some people still use mics in smaller places. Saw a few guys using mics this week at a local coffeehouse.

I should have mentioned that I was speaking from personal experience. I’m primarily a bass player, but I used to play a lot of guitar, mostly acoustic. I always hated the way my acoustic sounded plugged into my electric guitar amp, and never did come across a guitar amp that made my acoustic sound good. But when I took up the bass I happened to plug my acoustic into my bass amp one day and thought, “Wow, that’s what it should sound like!” It sounded just like my acoustic sounded unplugged, just louder, like Le Ministre de l’au-delà said.

Acoustic amps have not been around for a long time and I think more people use them now . I guess it depends on if a guy is willing to spend money for 2 types of amps if he plays a lot of acoustic guitar live.

Mister Rik - I don’t know acoustic or bass amps as well as I know straight-up electric guitar amps, but I have an hypothesis: as you mentioned in the tube amp thread, you like the sweet spot on your bass amp - it adds mustard to your hot dog, right? :wink: So there is a sweet spot, designed to push the tubes when your bass is playing certain frequencies.

So I am kinda assuming that your acoustic guitar’s pickup doesn’t push those frequencies nearly as much as a bass, so you are still within the clean headroom of the amp. So you get the warmth and a bit of compression from the tubes, but no distortion, per se, which is cool since you aren’t looking for any. That’s why you don’t like an acoustic through an electric guitar amp - the amp is designed to be pushed by the acoustic’s frequencies, since they are the same as the electic’s - so you get the distortion you look for with an electric…

Again, all conjecture on my part, but I think it makes sense…

And I agree with **Le Ministre **about piezos…flat and bright usually…

Here’s my totally unfounded (other playing bass and guitar) conjecture:

Most of the acoustic guitar sounds we are used to are the sounds of a big, Dreadnought acoustic. The harmonics that all make the sound of one special are mostly in the thump (rather than say a cheap archtop’s plink) at the beginning of the note’s attack. My guess is the speakers/eq on the bass amp are better at reproducing this, and the lack of piercing highs is actually a happy accident, since I imagine you’re using a piezo pickup, which are the king of all high and not much else.

BTW, If you run into an Ampeg vt-22 in a pawn shop or anything, try it out. 2-12, 100w, pushes like a 200w bass amp, usually really cheap, very nice EQ for the era they were made. I used to own one, it was the most bassy, punchy guitar amp I ever owned. I loved it, but at the time (early 90’s) you couldn’t find the 7027a tubes. and so when they got old, it got sold. You can find the tubes on line now. Most electric guitar folks pass it by, because it’s tube, and the models with master volume will not distort, so they don’t see the point I had a pedal that just went muddy when you mixed it with tube distortion, so I loved it. (wow, that was long - my point is, it’s basically a bass amp with a guitar oriented EQ on it - only drawback - jesus it was heavy for a 2-12 combo)

And on further reflection, try a silverface 4-10 fender bassman or the reissues. My roommate had one, and it was very much like the vt-22, with just a bit less bass.

Nope, no piezos. My acoustic guitar is a early-60s/early-70s Gibson (that’s all the further I’ve been able to narrow it down - the particular model, BN-25, was apparently built from 1963 to 1972), and so no built-in electronics. The pickup I use* is a Dean Markley stick-it-in-the-soundhole thing.

WordMan - aside from the “sweet spot”, I’ve wondered how much the speakers themselves play a part. Bass drivers, as I understand it, are built somewhat different from guitar drivers so that the low frequencies don’t throw the coils out of alignment. Essentially, if I plug my bass into a guitar amp, crank it to 10, and thump a big, loud, low E, it’s liable to throw the speaker coil so far that it can’t recover, literally “blowing” the speaker. But the coils in a bass amp’s speakers are designed to counter that by compensating for the low frequencies. So maybe this has the effect of producing a “tighter” or “more focused” sound when playing a guitar through a bass amp.
*Well, “used”; I hardly ever play guitar any more. I’m so accustomed to the bass that I’m completely cramped on a guitar neck.

Your acoustic sounds cool - that is the Gibson model that followed the LG-2 which was produced from the mid-40’s until the early 60’s. I can’t remember if the BN-25 has X bracing (better; it is what the LG-2’s have) or Ladder bracing (not as good). Either way, they are going up in value so make sure you wipe it down after you play it!

As for speakers - well, I am sure you are right. I don’t know that speakers in bass cabs are designed for bass - for the most part I think a speaker is a speaker, although a lot of bass cabs have 15-inchers, which clearly can handle lows better vs. their smaller counterparts (assuming the speakers are of the same build quality). Also, bass cabs are typically closed-back; guitar cabs are often open-backed - with a closed-back, you don’t have as much speaker travel because the air is locked up in the back of the cab and offers resistance to the speaker’s movement to volume spikes. An open-backed cab can mean that the speakers pop further when hit with a volume spike since there is no push-back from the trapped air. Just a WAG on my part.

Sigh. Unfortunately, wiping it down isn’t going to help anything at this point. I was given the guitar in 1980 or '81 by my grandfather, who was drunk at the time, having fallen off the wagon after a number of years of sobriety. I was 14 and just learning how to play guitar, and I had a cheap piece of junk no-name acoustic that I was learning on. He looked at it and said, “You can’t learn on that! Here, you can have this one!” (He sobered up again soon afterward, but never asked for it back.) Anyway, it was in cherry condition when I got it. But, being 14 and just learning (and not yet appreciating the meaning of “Gibson”), my pick technique left much to be desired. I fairly quickly wore the finish off the wood below the soundhole (that exposed bit between the hole and the pickguard), I didn’t know any better than to wear a metal-buckled belt while playing, and there are any number of dings in in the finish from inadvertently/carelessly banging it into things. There’s also a crack in the top, on the lower bout, though I deny causing that one; in my mid-20s I came home one night and my then-roommate told me a drunk friend of his had gone into my room and got hold of my guitar, which the roommate then took away from him and threw his ass out of the apartment because “you don’t do that shit”. I don’t know for sure that that’s where the crack came from, but it was shortly after that that I noticed it.

So, it’s kinda beat up. Still sounds awesome, though, and that’s what’s important. In any case, I have no plans to ever sell it.

Okay, that’s what I was thinking of. I knew there was some construction factor that limited speaker travel, but I spaced off the closed-back aspect.

Most small combo amps are open back but the big 4x12 cabinets like Marshall are closed back.