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4ohm, 8ohm speakers and output power

Assuming that two speakers both have the same sensitivity rating, but one having 4ohm and the other having 8ohm.
For example 88db/watt/meter.

Now usually and in most cases, a given amp can have its output power doubled when driving a 4ohm loud vs. an 8ohm load.

Does this mean that in theory, the 4ohm speaker can play louder than an 8ohm speaker given they use the same amp since the amp can deliver twice as much power to the 4ohm speaker? And since they have the same sensitivity, more power equals more louder.
andy2
gs5556
1,237 posts
 
If both speakers have the same sensitivity but different nominal impedances (8 and 4-ohms), the one with the 4-ohm impedance will not play louder. The 4-ohm impedance will attempt to draw more current (power) than the 8-ohm, but any extra current (power) it coaxes from the amplifier will be dissipated as heat - not as additional cone displacement. In other words, the speaker acoustic efficiency drops as the nomimal impedance drops. The amplifier notwithstanding.
andy2 OP
1,555 posts
 
I was thinking that if the speakers are rated using Volt instead of Watt then the imdedance will be taken into account.

For example if both are rated as 88db/2.89V/meter then they would play to the same loudness. The 4ohm speaker will just draws more current and therefore double the input wattage.

BUT I STILL think if they are using wattage as a reference then the 4ohm must be able to play louder given the same input wattage. I still don't see it any other way.
gs5556
1,237 posts
 
At the same input voltage a 4-ohm driver will draw 3db more power than an 8-ohm driver. If both drivers have the same SPL at a given watt then, yes, the 4-ohm is louder. Both have the same efficiency.

But now you have two different sensitivities because with the 4-ohm driver you get 1 Watt from 2 Volts whereas you get 1 Watt from 2.83 Volts from the 8-ohm driver.
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