About playing bass thru guitar cab. My final words on the matter.

Hi everyone!

This is my first post here and a sort of introduction as well i guess.

I've been visiting this (and others) forum for a long time now and what finally got me to sign up was the topic concerning playing bass guitar through a guitar cab.

This has been discussed A LOT, probably since the guitar and bass amps were invented and it allways sparks feuds and debate.
Now I just felt like doing my part in hopefully bring clarity to this matter from a more theoretical point of view.
I will not delve into the matter of playing bass through a guitar amp. That is a matter that is very dependent on what amp you use. No this is about cabs and speakers.

Ofcourse you CAN play your bass through either a guitar or bass amp into a guitar cab. It might even in the best circumstances sound great!

However..
Bass and guitar operate in different spans of frequencies. With a guitar you are rarely going below Hz in the lower 100s.
Bass on the other hand has a lot of power below these frequencies. This is where you find that warm and pumping sub bass that is so essencial to bass.
Naturally the amps and cabs are made to handle the frequence span of the respective instrument.

So if we agree that the bass guitar has most of its power and value in the lower 2 and 3 digit frequencies we can take a look at sound waves, which a speaker produces in large amounts.

A sound wave is built by sine waves in different dynamics and for a sine wave to be complete (and therefore audible), it has to travel a certain distance.
Ex. a sine wave at 20Hz (which is the lowest limit of human hearing) has to travel 17 meters/55.7 feet, to become audible.

A 100 Hz sine wave only has to travel 4 meters/13 feet to be complete.

Now, bass guitars and bass amps are made to put out very low frequencies at high volume.
This means that the speaker has to deal with both the volume and frequencies produced.
The lower the frequence, the harder it is to percieve. This is why bass amps often has much more wattage than guitar amps. Simply to be able to produce low frequencies louder. And to do that, the speakers has to be able to move air a long distance and the longer the distance the more possibility for movement the speaker needs.
A speaker designed for guitar does not have the in/out movement needed to produce such low frequencies. It has a tighter move span which makes it a lot more suitable for midrange and the lower parts of high frequencies.
The amp does not know or care if the speakers can't take the presure, it amplifies what you put into it.
And when a solid 150dB 80Hz wave hits a guitar speaker, the speaker max out and stops short.
In the worst case the rubber bearings crack and the speaker moves no more. Or if it doesn't crack, the paper membrane continues forward when the speaker stops. This will destroy the membrane and quite possibly the coil as well.
Bare in mind that if the speaker only had to stop the membrane when maxed out, it would be fine. But when the heavy magnet is moved, it takes a lot to stop it.

The speaker could in best case experience speaker exhaustion, which means the rubber bearing has been stretched and temporarily looses elasticity which would make it sound dull or perhaps go quiet. The speaker will recover from this a couple of times, but not much more.



What about octave pedals?
This is possible because the fact that the guitar amp does not amplify those frequencies the same way a bass amp does. They are pretty weak and lack the power that a bass guitar and amp would have.
If you play guitar with an octave pedal though a bass amp and guitar cab however, it would be a completely different story.
But the fact is that a bass string produce lots of harmonics that a guitar string doesn't, octave pedal or not. It really can't be compared.



Well this was what I had to say about this subject.
Hopefully this will answer some questions and/or confirm an allready worn out subject.

Best regards/ Philip