System Tuning For Musical Weight


Marshall Nack

23 October 2002

I've come upon a nice tweak for system tuning. This one is sure to set the objectivists on edge.

One of the most common problems I hear in high-end systems is a tendency towards brightness and is characterized by a timbral balance favoring the treble. Frequencies, from the bass register on up into the lower mid-range, are all shelved down. Typically the sound is thin, unsupported, and lacking musical weight and body. Quite often we seem to wind up here as a result of our quest for more detail, speed and accuracy. You certainly do get more clarity if you have a shelved down low end. I've been focusing on this lately because it's been a problem for me also.

We all know about mass loading: putting heavy weights on top of components. This will certainly lower the timbral balance, improve the soundstage by making images more stable, and add weight (no pun intended!). There's no end of subtle tuning effects achieved by using materials of differing pliancy or mass. Mass loading works but has its downside, as I've noted in these pages before. I hear it in the treble range, where it can create a ceiling that limits extension. The voice or instrument ascends and then hits a barrier. It sounds closed in. I hear it as a reduction in midrange overtone complexity resulting in a homogenized, less life-like quality. In my book, these tradeoffs outweigh the benefits, unless there are some very severe problems.

Lloyd Walker of Walker Audio gave me the tip that the shelf itself, and for that matter, even the component rack, can be tuned. His lead and brass resonance control discs are designed to be placed on top of and below the component. But he also suggested I try putting a disc in the center of the shelf and on any unused shelves. I let this idea percolate for a while.

It turns out that tuning the shelf is a wonderful method of adding musical weight to a system. The effect of putting a weight on the shelf is similar, but smaller in magnitude, to placing it on top of the component - but without the downsides mentioned above. Timbre is lowered, and there is more image focus and less blended sound. No ceiling is imposed on the treble, nor is there any reduction in midrange complexity and overtone information.

Note that I'm hearing these effects with PolyCrystal racks, which are very sturdy and rigid. This makes me think the weight's effect is not so much in physically stabilizing the component on the shelf, but rather has something to do with tuning the resonant frequency of the shelf itself. This supports Lloyd's theory that resonances in the component are drained off through the spikes (or whatever you're using under the component) onto the shelf, but there is also some return feedback of those resonances in the other direction - from the shelf back into the component.

I discerned audible differences when using the Walker resonance control disc, Mapleshade Heavy Hat brass weights and a VPI Brick. You can tune the sound depending on the type of weight you use and where you place it, just as with conventional mass loading. Best results were attained when the weight was in the center of the PolyCrystal shelf. When placed on one of the Mapleshade Component Support System maple slabs, however, violin tone suffered.

Personally, I don't need to fully understand the physics underlying this effect. It works. Try it!