Most guitar players today can get by in a live situation with an amplifier that’s 50 watts or less, cranked up or even a 16 watt amp mic’ed up. However, most bass players need to come to the gig packing a little more power. Here we will look at how power fits into what you may need for your bass rig.
Guitar vs. Bass
There are several reasons bass guitar needs more power than a guitar. In many situations the guitar is being played with some level of overdrive or distortion. Even a lighter blues overdrive is playing to the top end of the amp for a nice power amp bite. Now a clean jazz guitar player will want to have more power like a bass player, even though he may not play as loud. The reason for this is headroom. Headroom is the key to a very dynamic clean sound. Headroom is the amount of power you have left for clean peaks, over the average power you are using. Headroom is not really an easy measurement in guitar and bass instruments, because you are playing to your feel and your spot in the band mix. You usually don’t have a decibel level specified like a PA system being designed for a venue. You may average 50-100 watts, but a slap or heavy accent hit may require 4 times the wattage to stay out of clipping.
Another reason a bass guitar needs more power is based on your hearing. Bass frequencies take much more power to amplify, because the human ear naturally hears the midrange frequencies of the guitar and vocals more prominently than the bass.
Bigger bass amp or just more cabinets?
Most people will tell you that bassists should select a bass amp that puts out twice to four times the power of the guitar amp(s). While this is a very good rule of thumb to start with, you will have to look at the band make up (not the black eye liner kind), the style of guitar playing and amps, style of bass tone clean or dirty, number of bass cabinets and PA available at your gigs.
The band make up is important to look at (no pun intended), because you may have two guitars or even three guitars to compete with, and more guitars will be louder. Keyboards can also put out the same low frequencies competing directly with your bass range in the mix. This would throw off the guitar rule of thumb quickly, but you may just need to go closer to the 4 times.
The style of guitar playing will throw off the 2-4 times, such as if the guitar has a high dynamic raw distortion tone or if the guitar is tuned lower or has lower strings competing in your range. Tube guitar amp wattages are a little deceiving over solid state wattages, because a guitar player may be pushing into the power amp section on a tube amp for that power amp overdrive tone where he would want a solid state power amp to be cleaner, getting his tone from the preamp. An over driven tube amp will present more output than a solid state amp of the same wattage, due to the how the power tubes enter a soft clipping at their rated output with more headroom to hard clipping than solid state amps. The rule of 2-4 originated in the tube amp days where both the bass amp and the guitar amps were mostly tube, so keep this in mind you may not need as much if you are playing with solid state guitar amps.
The style of bass playing can be a major factor. If you like a little overdrive, then you may not need as much headroom. Using overdrive pedals or amps with drive are reducing the dynamics of your signal, so you may not need as much headroom over you average output. If you use a slap technique constantly, you may need more headroom for the detail to cut through the mix. This is a very high dynamic style of playing and dynamics need headroom. If you want your lows to be clean you will need more power.
The number of bass cabinets or style of bass cabinet is very important. The overall volume of a bass rig is heavily dependent on the speakers. The more speakers the more air that moves and the more output you have. You can have double the speakers with less wattage and double your headroom. You may not get much more headroom if you double your wattage with the same speaker, especially if you are already near the wattage the speaker can handle. Here you are looking at power amp wattage, impedance and speaker handling, so be sure to look at your rig as a whole. If you’re struggling with your current setup, you may just need to add another cabinet. This will also lower the impedance on your amp, so be sure it can handle the lower impedance. The lower impedance will also increase your amp’s output wattage.
Finally look at the PA system available. This is important because if the PA and monitor rig at your shows is good, then you may only need an amp for your mic’ed tone and stage volume. You could even get away with a DI box and preamp going through the monitors. This is very rare for most players and it is better if the sound guy can mic your rig along with a DI box connection, so your amp tone you have worked hard tweaking is put through the PA. This is especially good when your tone is a little overdriven, because that would not be present in the DI box off your bass. Also, your speakers do not respond to the overdrive signal as fast as an amp DI output making your tone more brittle and clicky in the PA than what you are hearing through your cabinets.
Overall volume is not only about wattage. When evaluating how much power you need, try to get a good idea of your band’s real world volume (and don’t forget to get an amp that’s loud enough to be heard over your drummer, too!) If you are playing small coffee shops, small bars or shows with good PA systems, 200 watts with a small cabinet like the Carvin Audio MB Series or the BX700 with a single 210 cabinet could be more than enough. For larger venues, shows with poor (mostly vocal) PA systems, or a very loud band, a BX1600 or B2000 with 2000 watts and two BRx10.4 cabinets would be more suitable. While most venues will DI your amp or mic you up, it is important that you have at least enough volume to cover what you need on stage. You will always play better when you are comfortable with your sound on stage. When in doubt, get an amplifier with more wattage than you need. You can always turn it down, and bass rigs thrive off having clean headroom helping to maintain a solid, powerful foundation for your band. All these different aspects of your playing situation are the major factors in determining how much amp you need.
What is your rig and for what type of shows?