Tuning the Treble

Tuning the treble. This is the fifth and final installment in a series on the acoustic aspects of room tuning Zu loudspeakers via positioning.

Tuning to your desired treble qualities sits atop the position tuning sequence: bass, mids, treble. Without getting the bass and midrange right you are not likely to be satisfied with the highs—treble needs context or it will just float there in the mix, ungrounded, irritating you.

At this point you are done nudging the speaker’s position, treble tuning is mostly about the speakers firing axis, the toe and cant (lean-back) and elevation. The experience you gained with toe when tuning midrange will help you hear the more subtle aspects of treble tuning. Start with toe, try a degree or two inside of where you got midrange tuning. Then try a degree or two outside. Drill down on your sound and call it good after a handful of changes. Next move to the lean-back phase. For smaller rooms with low-slung seating no lean-back is typical. But for tall chairs, big rooms or listeners that prefer food prep or dancing, lean-back will likely improve overall sound.

Have a friend lean the playing speaker back, hinging on the back two footers. Two things are happening here, you are changing the firing axis which is angling the wavefront, and you are also elevating your drivers a bit further from the floor. The distance between floor and speaker is mostly impacting the midrange, but the audible changes are interpreted by most as change in the treble region. Okay, there are other things going on when you lean the speaker back, but these are the two primary. If your Zu speakers also have the finger ports on the bottom you will need to shim for the new gap. If you find you like the sound when the speakers are leaned back further than the angle that puts an inch or so [4 cm] of space between the lifted front footers and the floor, you’re likely to prefer the sound with the speakers on risers. If you start messing with risers you might need to refine your midrange tuning.


Now let’s talk about the final building blocks of this speaker tuning pyramid (ironically placed beneath the speaker). But before you start with risers, measure and note the distance from that speakers inside front corner to the side wall, and form the same inside front corner of the speaker to the front wall. Also note the toe angle. Now, turn your amp off, remove the speaker cable and move the speaker out of the way. Place the butcher block you grabbed from the kitchen, approximately where the speaker was. Then place the speaker atop the block. Reposition the speaker to your measures. Reconnect, and while playing have your buddy again lean the speaker back. If you find you like the sound with a lot of lean-back still, grab more blocks, or bricks. Once you are happy enough, mirror what you did to the playing speaker to its mate, perfectly mirrored. Now mirrored and connected, fire things up in stereo. Expect to be impressed. If not, make sure your speaker cables are both connected, and both in the same polarity—red to red and black to black. Yes, materials used for risers also influences sound, but not as much as the elevation.