[Mat Nieuwenhoven]

On Tue, 23 Apr 2019 03:20:06 -0700 (PDT), wrote:

Mat Nieuwenhoven wrote:




Technically, you are correct. The 1998 book "Testing loudspeakers"
from D'Appolito gives the formula in chapter 2.8.3.

** Ya don't say.

I like to provide references if possible.


** A tedious pretension to non existent expertise - I'd say.

I do not doubt your decades of experience in this field, but I prefer
verifiable references.



For practical use with given amp, a speaker with a higher SPL at
2.83V will sound louder than one with a lower SPL, even though the
latter one might be more efficient when looking at SPL/Watt.


** Sorry, that makes no sense at all.


Say if I were to replace the small speakers of my home stereo by ones
that can provide a decent SPL at much lower frequencies, and I have
the choice of two, one with an SPL of 80 dB and the other with 85 dB
(both measured with 2.83 V), then the one with 85 dB will be
noticably louder with the same volume settings. That is obvious.
Now if these speakers are 6 ohm, and there is a 12 ohm version also,
then driven with the same amp the 12 ohm version will be less loud
(its SPL at 2.83 V). Yet if one measures both speaker units with
regards to efficiency (sound per watt), the 12 ohm one could be more
efficient.


** Complete ********.

Try actually reading my earlier post directed to YOU and see that the spec is for an *applied watt*" so the rms noise voltage used *DEPENDS* on the speaker's nominal impedance.

2.83V for 8 ohms, 4V for 16 ohms and 3.46 for 12 ohms.

I did read your posts, and it is exactly what I wanted to point out.
The _efficiency_ is defined per applied watt. A given amp gives out
voltage. If the amp is capable of say 40 Vrms output, then a lower
impedance speaker will get more watts than a higher impedance one,
provided the amp can supply enough current. An 8 ohm speaker will
then take 200W, a 16 ohm speaker 100W. The 16 ohm one would have to
have twice the efficiency per watt as the 8 ohm one in order to
produce the same SPL. And unless you're power-constrained, achievable
SPL will likely be preferred over internal speaker efficiency,
especially with guitar speakers.

Mat Nieuwenhoven