Speaker's amplifer minimum power recommedation

Speaker manufactures often list in their specifications a minimum amplifier power recommendation.  Is that power recommendation into a standard nominal 8 ohm impedance, or is it a recommendation based on the speaker's published nominal impedance?  I am looking at a speaker with a 4 ohm nominal impedance and the specifications recommend a minimum power of 40 watts.  Is that 40 watts into an 8 or 4 ohm impedance?


there is no standard for this

always assume worst case if you want to make sure you supply enough amp power, the amp being spec’d by the speaker maker should and will obviously be delivering its power into the actual speaker load, not some nominal 8 or 4 ohm resistor/test load

so in your case, i would take the recommendation to be 40 watts into 8 ohms (and best if it could do 80w into 4)

@testpilot I've always assumed the minimum power was the 8 Ohm rating, since that's typically what's sold, but of course, if your speakers are 4 Ohms or less you also wan to make sure that amp has the current drive for it. Ideally find the minimum impedance, and/or the minimum effective impedance.

So if your speaker maker recommends 50 W minimum, but is 4 Ohms you'll want an amp that produces 100W or close to it at 4.

Manufacturers often exaggerate this number compared to normal listening volume.  They specify a minimum to get maximum volume to fill an auditorium.  I know of one speaker with 96dB sensitivity that could easily be driven by a 1.5 wpc type 45 amp but they specify minimum amp of 30 wpc.