So if we say that the sweep is at 2.83V, then at 15V output, there is +14.5 dB of gain. So the Topping can hit 99 dB at 70 Hz and 104.5 dB at 1 kHz.

At 1 kHz, it is pulling 56W (2.5A) and at 70 Hz, it is pulling 9.4W (0.625A).

If you “could” deliver 56W into 70 Hz, then your amp would need to push 36.6V, and that would be a 22.1 dB gain over 2.83V or 106.6 dB. Even though that is only 1.525A, the LA90 cannot hit 36.6V because this sweep shows that the max voltage is ~15V.

So the impact of the high impedance “somehow works out” is that if you have the FR response curve and maximum voltage of the amp, you can do the math.

The other way we can do it (since I based it off the 4 ohm measurements) is that 24 ohms should be 1/8th of 4 ohm and 1/4 of 8 ohm, or 7W-9W give or take, which matches my 9.5W calculation earlier because it might be easier for the amp to drive at high impedance.

The impact is the “90 dB @ 1 watt” sensitivity. Here, if you assumed the LA90 hit 46W into 6 ohms, you would see 106.6 dB predicted but you don’t really get that.

**If you wanted 36.6V into 70 Hz, your amp would need to deliver 335W into 1 kHz, which is how the impedance affects the “power” of the amplifier you need when shopping, even though that is to get to 56W at 24 ohm.**