Everything you need to know about bass amp watts, power and efficiency

We previously discussed matching the impedance load of your cabinets to your bass amp. This month, we look at the crucial speaker cabinet power handling and dispel a few illusions about it.

What exactly are watts?

A watt is an electrical or thermal power unit.

Isn’t the wattage of a lightbulb measured in watts?

Yes, and we tend to believe that the brighter the bulb, the more powerful it is – but this isn’t always the case with amplification. Because of the intricate interplay between the bass amp, the power supply, and the attached speaker loads, power does not exactly equal how loud a system is.

What is it about those words that makes my heart sink…

Don’t worry, the farther you delve into the applicable theory, the more difficult it becomes. It doesn’t help that the marketing department of a certain amplifier maker may have had some influence over the published results as well. You can disregard terminology like ‘Watts PMPO,’ ‘MPO,’ ‘Total Power,’ and other ‘creative’ naming conventions. Ignore the watts indication near the power socket on your bass amp as well. That is obviously not the output; it is simply the consumption of mains power.

Is there a reliable standard of bass amp I can rely on?

Yes. The power handling of a cabinet is frequently expressed in watts RMS, which stands for Root Mean Square. This test shows you what a speaker can handle over time, as opposed to getting a peak reading, which can be considerably higher but could risk damaging your speaker coil within a shorter length of time.

Is there a connection between decibels and all of this?

They do, in fact. Sound pressure level (SPL) is expressed in decibels (dBs). This is an effective method for determining how loud something is. However, power handling in watts is more usually mentioned.

So, how much power do I need to be heard?

That’s an excellent question. If they’re in a conventional rock band, I urge bassists to aim for roughly 500W RMS. This is due to the possibility of plugging into an underpowered cabinet, in which case 500W should be sufficient to make you heard on most gigs. However, if you’re only using a single 12″ speaker, don’t expect a 500W amp to be able to see off your two guitarists’ 4×12 rigs.

In that scenario, experiment with more cones. You’ll be able to move more air, which will help you get heard over the loudness of your bandmates. If given the option of doubling my available woofers or using an bass amp with an additional 100W of power, I’d take the former every time.

What exactly do you mean by inefficiency?

The ability of a speaker cabinet to convert incoming electrical signals into outward sound defines its efficiency. This efficiency is measured in decibels (dB). If this quantity is provided, it may be followed by something like ‘1w/1m,’ indicating that the signal was measured from one metre away while the speaker was given one watt. But be cautious: manufacturers test with a variety of signals, and there doesn’t appear to be a standardised system in place that everyone confesses to utilising for readings.

So, what do you recommend when it comes to combining bass amp and cabinet power?

Pay close attention. Is the speaker causing distortion when you expect a clear sound? In that instance, you might be pushing it too far. Reduce the volume! Another piece of good advise, given that RMS is an average value, is to ensure that the amp and cab are matched similarly in terms of impedance and watts, or just check that the cab’s power handling is higher. Finally, if you’re not sure what you’re doing, always seek qualified help.