How much does an Alex Attenuator cut watts to the speaker?


Just curious if anyone has a definitive answer here. I'm running a Germino Club 40 head (65-70 w output when cranked) into a 2x12 cab with Celestion RI Greenbacks (50 w total handling capacity). Lots of folks say that this is safe, lots of folks say it is not. There is that "general rule" that a speaker cab should be double the wattage of the nominal power rating of the amp - so 100w cab for a 50w amp.

However, I do use this rig with the Alex Attenuator, and generally attenuate around 6 - 9 db. I read somewhere that even -3 db cuts the power an amp is sending to the speakers in half. So... if the Club 40 is putting out somewhere around 70 watts when cranked, and the Alex is running at -3 db of attenuation I would guess that even with an OD pedal in the mix the speakers are seeing about 35-40 watts max, which means a 2x12 Greenback loaded cab ought to be safe.

Does anyone have any information to share or to confirm/refute this theory? I'm especially interested in whether anyone has definitive information on just how much the Alex Attenuator reduces actual wattage from the amp to the speakers at various levels of attenuation.


Gold Supporting Member
the overall formula your trying to use is a bit flawed.

The approximation of doubling wattage to get another 3-4 db is just that, an approximation.

There are a bunch of ways to state wattage. If you are trying to protect your speakers based upon amp and speaker wattage rating you can only come close.

For example... I have a twin reverb that I run with only 2 of 4 power tubes. That's 80 watts down to 40. Then I use an attenuator to knock off 3-4 db's. Approximately 20-25 watts. I have two old 15-20 watt speakers, and I rarely have the amp above 5 on the volume. It's close enough for me to feel safe.

The attenuator absorbs energy and reduces volume. The 'wattage' is an amp output rating, not a direct volume rating. Hope that helps.


You can always email me my email address is right on the back of the attenuator. I'll happy to help. My attenuator takes little less than half at -3 db and it is down to a quarter at -6. The typical rule still says to have double the speaker wattage for the amps output. But loads of people report all the time that they exceed that.

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