Speaker Power Ratings: What you need to know

I often field questions about speaker power ratings. They often are a source of confusion for players so here’s a guide to what you need to know:

1. When dealing with a multiple speaker cabinet the rating of the cabinet is product of the total number of speakers multiplied power rating of one of the speakers—- if they are same speaker. So a 4x12 with 60W speakers will have a total power rating of 240W. In an cab with a mixture of speakers you use the speaker with the lower power rating to calculate. If you have a 4x12 with two 60W speakers and two 25W speakers you have power rating of 100W.

2. You can and should use a speaker cabinet with a power rating that exceeds your amps output power. The power rating of speaker is immaterial so long is it at least 150% than the amp’s power. If you like a 150W speaker with a 5W amp that is just fine.

3. The power rating must be at least 150% of the amp power output to be reliable. An amp;s power rating is an average or RMS. It’s peak power is higher. Square wave signals (distortion) are much harder on speaker than clean signals and far more likely to blow a speaker. There are many examples of vintage amps with low powered speakers that were at or only slightly above the amp’s rating. These often blew.

4. Higher output to speaker power handling ratios will be more reliable. At Carl’s Custom Amps we generally use a minimum of 200%. Players would run their amp continuously loud and clipping will benefit from a rating of 400% to 500%

5. Not all speakers are as robust as their ratings suggest—- so use caution. This is especially true neo magnet speaker that do not have heat sinks. The magnet is so small it cannot act as heat sink so heat builds up in the voice coil and can cause failure. Small magnet Alnico speakers are also prone to overheating.