I have noticed the K's are very prone to standing waves....and you guys just thought I was a slob!! It's standing wave breakup treatment!!
Sorry Lee, you’re just a slob.
To your point about the K-horns being prone to standing waves, this is certainly true, since they are corner loaded. This is a compromise used to increase the effective mouth area of the low frequency horn, extending bass response, but being in the corner excites all room modes maximally. Since the speakers are locked into the corner, the only effective tool you have to minimize the effect of these maximally excited modes is to vary listener position for flattest overall SPL.
Since I find dynamics to be very important to musical enjoyment, I think that this can be a reasonable compromise providing that a “flat enough†response can be had at some listening position. Outside this position though- watch out! Those bass modes will bowl you over in some places and be unsatisfyingly absent in others. High voltage sensitivity is something I strive for in a speaker, and the K-horns have that in spades. I have not had a chance to hear these, but I’d love to.
To the O.P.
The 901’s are an interesting design. They’re meant to be placed near (but not against) the rear and side walls to augment bass response. This will tend to emphasize room modes as I mentioned in my response to Lee above. Since they are locked in the vertical direction by the provided stands (and listener height) you should play around with placement in the other two directions for the most even bass response at the listening position as well as experimenting with location of the listening position. This is a balancing act wherein you shoot for the best compromise between lowest bass extension, overall SPL evenness, and stereo image due to separation distance. I tend to switch back and forth between static frequency response and Pink noise RTA to try to get a better picture of perceived sound. You can do this with your ears and no mic, but without a reference, it gets tricky, since you will end up with many different responses and it’s difficult to know which is “bestâ€. Add in the tone controls and… Lots of playing around will get you there though, and this can be a fun and instructive exercise if you understand what is happening with the different placements.
They also have the bulk of their drivers reflecting off the rear and side walls directly- as opposed to reaching your ear, then the wall behind you, then the wall behind the speaker. This will emphasize reflection over the first arrival sounds- which the brain naturally emphasizes. The effect of which, is to have less “pinpoint imaging.†But, as long as these reflections arrive within 50mS of the direct sound (Haas effect), the brain will integrate the reflections with the direct sound and perceive them as the direct sound.
Whether these are good compromises depends on (at least) Room size, available listening positions, musical type and listener preference. For example, orchestral music would tend to be enhanced by spaciousness while chamber music would benefit from pinpoint imaging.
You may know all of this- I don't know. But, some of us likely don't, and I hope this helps them, since it applies to all speakers/ rooms.
Zach
p.s. As always, I'm open to correction/ modification.