Aperion Audio’s PST MKII adds the highest frequencies your speakers might be missing. Most tweeters roll off around 20kHz. This planar-ribbon unit extends well beyond that, reaching into the ultrasonic range. The result is not a harsh boost in treble. Instead, it adds air and space to the soundstage. Cymbals have a more natural shimmer. The stereo field feels wider and deeper.

Setup is straightforward. You place the wood cabinet directly on top of your existing speakers. The crossover is fixed, so you don’t need to calibrate anything. It simply blends with whatever you have. The effect is subtle. You notice it most in the texture of high-frequency details—brush strokes on a snare, the decay of a piano note.

One limitation: the tweeter is passive, so it draws power from your amplifier. If your amp is already struggling to drive your main speakers, this adds a small extra load. It works best with moderately efficient speakers and a clean amplifier. For most systems, though, it’s a refined upgrade that adds depth without changing your speaker’s character.