If we break down the sonic palette, the deep and mid bass of the Blue Hawaii are very good. We know that the SR-009s can offer impressive bass and are capable of delivering dynamic and detailed low frequencies without much bloat or blur. We know this because you can hear the SR-009 deliver accurate drum and string bass sounds (accurate when compared with the sound of live music) through other amps like the Woo WES. With the Woo, you just get the sense that the headphones are being well controlled, yet supported with excellent power and drive. We’d say the Blue Hawaii SE isn’t quite as good as the Woo WES in terms of absolute neutrality (provided the Woo has been fitted with optional, upgraded driver and output tubes), because the BHSE provides a little more upper bass than we’d hear live. But apart from hair-splitting comparisons with the more costly, upgraded Woo WES, the bass of the BHSE remains top notch.
The midrange of the Blue Hawaii SE is also quite natural. Essentially, all headphones have some frequency response errors that lead mid- and upper-range instruments to sound a little distorted, especially on certain dynamic passages. The SR-009s reduce these distortions significantly when compared to many headphones, but they can, at least with some amplifiers (e.g., the Woo), occasionally over-emphasize upper midrange transients to a slight degree. We thought the Blue Hawaii SE did an excellent job of taming this tendency of the SR-009s, in the process showing just how neutral and smooth-sounding the SR-009s can really be.
In a sense, we are talking about ways in which different amps manage and balance sonic qualities that, while positive in an abstract sense, also have the potential to become double-edged swords. If we look in more detail at the upper midrange and treble performance of the Blue Hawaii SE as compared to the Woo WES (with upgraded tubes), several things become apparent. First, the Woo conveys an almost otherworldly quality of purity and continuousness, and gives the impression of offering almost boundless reserves of resolution and detail. For listeners who highly prize those specific qualities, the Woo may be the amp of choice. Second, the Blue Hawaii SE has an absolutely uncanny ability to capture the constituent elements of music in a subtle and revealing way (not quite as microscopically revealing as the Woo, but close), while at the same time—and this is hugely important—showing how those musical elements combine to form a cohesive whole. Thus, the Woo tends to deconstruct music into its component parts, while the Blue Hawaii SE reveals the parts but deftly reconstructs them to present a musical whole that makes sense.
Interestingly, planar drivers often have a bit of resonance in their measured decay patterns, so in the unlikely event that you encounter moments when the Blue Hawaii SE/SR-009 combo does sound a tiny bit rough-edged (a very rare occurrence), we can’t help but wonder if the BHSE might actually be more revealing than some competing amps. This question comes to mind because of the excellent small signal accuracy shown by the Blue Hawaii SE. Small signals are important as the basis of spatial presentation because they are what you hear when listening for the acoustics of the venue where a recording was made (e.g., the reflections of sound off of walls and floors, etc.). We found the Stax/HeadAmp combination does a great job of revealing the spaces in which various recordings were made Likewise, the overtones of an instrument are, along with delicate transient and textural details, the source of its color, but only if they are reproduced in proper proportion to the fundamentals of notes (e.g., the decay of a plucked guitar string should be audible, but not louder than the body of the note). Once again, the Stax/HeadAmp pair comes through with overtones, textural details and the like that are easy to hear, yet perfectly integrated with the fundamental sounds of the instruments that produced them.
Related to, but different from, detail resolution is the idea of instrumental separation. In live music, one can often hear the band or orchestra as a whole, but also hear individual instruments without everything being muddled. The Blue Hawaii/Stax pair is superb at allowing you to focus you attention broadly or narrowly, just as you might do when listening to live music. This ability is a hallmark of dynamic capability, and indicates the circuitry can handle passages where signals swell dramatically or become diminished in level—all without any increase (or noticeable change) in distortion. No matter what the music does in a dynamic sense, the BHSE sounds delightfully consistent and unflappable.