Class D Amplifiers for tweeters ?

[gainphile]

There's few manufacturers (like ADAM) who insist using Class AB for tweeters. I'm curious as I've heard nothing wrong with my Sure 4*100 Amps driving paralleled XT25 as part of my active 4-way dipoles. That's 2 ohms nominal load.



I swapped the amplifiers with Gainclone 3875 and noticed that it's more airy. But soon it is clear why. The ClassD do not like being loaded so much at high frequency.



The loss is first order lowpass, and very easily corrected with shelving highpass filter. This deviation does not happen with single tweeter (4ohms load)



The correction gives back the airy sound.

It would be interesting if instant-switching of the amps were possible, but swapping them around I do not notice one being better than the other. Safe enough to say they sounded the same, and certainly nothing to draw attention to.

[Saturnus]

The output filter in a class D amps is always designed to a specific load impedance. Loading it with a a different impedance will affect the high frequency cut-off point. Specifically loading it with half the impedance will halve the cut-out point, and this is what you have experienced here.

The fault therefore is not on the class D amp but on the user using it outside its specified working area. Find an amp that is designed for 2 ohm loads instead, or change the output filter.

[gainphile]

Yes, that's correct. However to compare, gainclones doesn't mind that.

The PDF of the comparison study is here:

ClassD vs Gainclone amplifiers

In summary, Class D is as good as linear amps even for tweeters.