Why do guitar amps only use one type of speaker cone?

Question

In HiFi systems and house sound setups, a speaker cabinet nearly always has multiple speakers of different diameters to handle different parts of the audio frequency spectrum (and bass is typically handled in specialist cabinets entirely).

Electric guitars don't go far into bass territory but do cover both mid and high ends of the spectrum so why do most (all?) amplifier cabinets and combo-amps employ a single speaker, rather than for instance having a separate tweeter and main speaker cone?

If you're going to mic up a single cone and then split it across low/mid/high speakers, wouldn't it be better to mic up multiple separate cones directly from the amp... aren't you losing something with a single cone?

Answer 1

Hi fidelity reproduction of high frequencies is undesirable in electric guitar amplification. If you look at what actually comes out of a guitar amp, things get really messy around 5 - 6 kHz and then drop off rapidly after that.

This is a good thing. If you ever use any kind of amp or pedal distortion designed for guitar and then run it directly into a mixer or mic pre and then amplify it with a full-range system, you'll find you get a very challenging ear-piercing sound. That kind of sound can work in some contexts, but it's not the traditional guitar sound that has made the electric guitar so popular.

There are also many aspects of a speaker cone that color the sound. Normally this is a downside of speaker cones when we want hi-fidelity sound reproduction, but it turns out the the guitar sounds that we all love are partly reliant on the speaker cones that were used in the amps that we are hearing.

The real reason why guitar amps and speaker cabinets are the way the are is twofold:

1. When the first guitar amplifiers were designed, modern technologies were not available and engineering realities (e.g., cost) influenced the initial designs to be a certain way.
2. Listeners grew to love the sound as it was at the time and "modern innovations" only change and take away from that sound, so amplifiers are still made the same way they were in the 60s and 70s (more or less).

Answer 2

It's really quite simple.

Your Hi-Fi stereo speakers are designed to produce the full range audio spectrum that might be found in recordings that you would play through your system. This will include the lowest notes of a bass and a kick drum to the high frequency of a cymbal or highest notes of an 88 key keyboard.

The frequency bandwidth that an electric guitar is optimally contained within a much narrower band width that can be effectively and optimally reproduced with a single speaker. There is no reason to complicate matters with multiple tweeters, woofers, and mid range speakers and crossover mechanisms.

One speaker is usually more than adequate for the limited bandwidth that we expect from an electric guitar.

The reason you see bass cabinets with multiple speakers (usually the same size) is that the lower frequencies produced by a bass guitar or upright bass are more faithfully reproduced by moving larger volumes of air. This requires either a very large speaker cone (15 - 18 inches), or multiple smaller cones which can deliver a tighter punchier bass sound as opposed to a muddier sound when using a single larger speaker to move the same volume of air.

Answer 3

"Electric guitars don't go far into bass territory": Uh, we are talking about E2 here. Which is absolute bottom of the range for bass-baritone singers. Top is something like B5 (19th fret). Which is top range for choir sopranos but does not require a violin player to stray from first position. So we are not talking about particularly high material for clean play, and for clean play, guitar has pretty moderate harmonics.

Things are quite different for overdrive. Now you don't want to "accurately reproduce" the electrical signal for overdrive (listen to it on a Hifi box or good headphones to see that it's not all that pretty without an amp similator) rather than get a nice and consistent acoustic representation. Not having to rely on a crossover and different speakers is a boon.

Another boon is that overdriven signals have disproportionally large high frequency content. Tweeters have smaller membranes and heat dissipation, and consequently smaller total rated power. It's actually comparatively easy to damage them using overdriven signals. A broadband speaker, in contrast, can shoulder quite higher power even if its directional characteristics and reproduction of high frequencies is not all too pretty.

But the main point is that a guitar amp is part of "the instrument" like your effect boxes are, not part of the reproduction chain or PA. So it can afford to shape the sound, and the characteristics of the broadband speakers used in guitar amps tend to fit in with that reasonably well.

Answer 4

There are guitar and bass guitar amps that feature multiple frequency dedicated speakers, and even multiple amplifiers. These ones are usually aiming for higher fidelity, as for amplification of acoustic instruments, jazz guitars and the like.

As a bass player, I've tried and disliked some of these amps that featured high frequency horns because they tend to have uneven "spikey" frequency response that emphasizes the percussive clicks and noisy part of the sound from the strings, not the musical notes. The previous answer makes the most important point that the characteristic tone of a speaker in an amplifier is considered part of the instrument itself. Often "bad" speakers (in high fidelity terms) can have a great sound if you are looking for a certain tone, for instance a soft character when being over-driven, which is a trait of older, weaker speakers with paper cone edges.

On the other hand, if you want a pure tone, plugging directly into a quality high fidelity system works fine - I plug my bass guitar direct into my home computer recording rig which has a yamaha subwoofer and Alesis near field monitors and it sounds good. Many pop records have been recorded with bassists playing "direct" into the mixing board, and some guitarists will even play that way for a bright, clean sound. If the frequency response of a system is flat and realistic for music playback, then a good instrument is going to sound good playing through it.

So the reasons you see single speakers are more practical and cultural than technical.

Answer 5

It's also due to the fact that guitar amps traditionally only deal with mono signals.

Although not all amps are created equal! The Roland JC120 & JC40 have stereo speakers which give a great sense of space when using stereo chorus or delay.

Answer 6

Single guitar amp speakers are more than capable of producing the frequency range generated by an electric guitar. If you used tweeters the human ear would not be able to withstand the terrible sound of high frequencies when distorted, delayed, modulated, compressed or overdriven. As for bassist a 15" woofer would produce the heavy bass boom that one would feel in your chest. The 4 x 10" is BS. Ampeg combo's have a tweeter and that is to take care of the sound produced by slap bass. I have been making tube amps for the last 62 years and played lead guitar until I was given 4 bass strings a few years ago due to my advancing age. My father even taught me how to set voice coils when replacing speaker cones. The rest of the discussion is for Audiophiles who like to own multiple speaker cabinets with crossovers for impressing their friends. Most people hear about 22k when 18 yrs old and by the time you get to my age you only need a woofer and even then you feel it more than you hear it.