Can we hear sound above 20kHz!

[nopiano]

Is having a tweeter being able to produce super high frequencies above 20khz better for the frequencies under 20khz in terms of smoothness or resonance?

I’ve always broadly believed that, yes. Because from 15kHz to 30kHz is only an octave, and it’s generally accepted that young humans can hear up to 20kHz. After that it rather depends on the design, but most dome tweeters resonate north of 20kHz, and the higher the better.

As you say, the further the resonance is from any likely signals the better. An unfortunate side-effect of hi-res mastering can be spikes outside audibility, and we don’t want those modulating wanted signals either.

You can see the HF resonances in reviews of speakers in Stereophile and Hifi News, many of which are searchable on their websites.

 

[AJM1981]

Is having a tweeter being able to produce super high frequencies above 20khz better for the frequencies under 20khz in terms of smoothness or resonance?

Frequency ranges of a well configured tweeter don’t overlap with the midrange and are not smoothing anything out.

The “super tweeters” I came across are mostly ribbon or AMT and they give a different signature within the audible. Placing them on top of a loudspeaker to replace another type of tweeter will both change the literal position and the signature of the tweeter. So you basically end up with a “different loudspeaker”.

The inaudible frequencies won’t do anything.

 

[Jasonovich]

Frequency ranges of a well configured tweeter don’t overlap with the midrange and are not smoothing anything out.

The “super tweeters” I came across are mostly ribbon or AMT and they give a different signature within the audible. Placing them on top of a loudspeaker to replace another type of tweeter will both change the literal position and the signature of the tweeter. So you basically end up with a “different loudspeaker”.

The inaudible frequencies won’t do anything.

Yes it has changed the character slightly, on my Dali Oberon 3 but in a good way. The range on my Dali's is 47-26k Hz. I have my extender tweeters set to 10kHz and onwards.

The enhanced support of the upper frequencies reminds of that song by Lou Bega Mambo No. 5 (a Little Bit of...).

It gives that nice bit of sparkle and a lift. It may not work with all speakers but it actually does nicely with the Dali's