(excerpt from “Optimizing ASC TubeTraps” by J. Peter Moncrieff)
Alignment of TubeTraps
ASC TubeTraps are designed to absorb the full frequency spectrum (down to their bass cutoff) on one side, but to reflect and diffuse most of the frequency spectrum above 400 hz from their other side. That engineering feature becomes a very powerful and flexible tool for precisely adjusting perimeter reflection control.
Recall that we spaced TubeTrap columns about 3 feet apart to control the mud factor, between 100 hz and 400 hz. The entire spectrum above 400 hz, include fog the midrange and trebles, is a different matter entirely. It consists of short wavelengths which are directional, and which can be directionally steered to sonic benefit, rather than simply absorbed everywhere.
By simply rotating the cylindrical TubeTraps, you can determine how all frequencies above 400 hz will be steered in your room (with the half round model, you are more limited, and you must preselect and orient the reflective direction if any). The subtlest change in rotation of any cylindrical TubeTrap in the room can make a significant difference in truly optimizing the sound of your system (that’s why we recommend the full round rather than half round models, if you can afford them).
Rotating TubeTraps to absorb energy (above 400 hz) on short primary reflection paths (within the Haas window) can work wonders to improve stage imaging and coherence, and eliminate glary hot spot colorations. And rotating TubeTraps to reflect and diffuse later reverberant energy on long secondary, tertiary, etc. paths can work wonders to improve imaging ambience and depth.
The basic strategy is shown in Figure 5. The line radiating from the center of each circle represents the seam sewn along the length of each TubeTrap; this is the direction of maximum high frequency absorption. The setup shown in Figure 5 will give decent performance, but it really intended just as a starting point, from which you should further fine tune by ear. If you have also installed any horizontal rows across the ceiling, they should be rotated to point similarly into the room as the equivalent TubeTrap columns at that point along the side wall, and then fine tuned from that starting point.
The sets of TubeTrap columns along the side walls that are off to the side of the listener are an interesting case study. The Damaske effect says that you can best hear the hall ambience in a recording when randomly diffuse incoherent information is presented at the side of the listener’s head. Thus, all TubeTrap columns along the side walls (and rows across the ceiling) are rotated to optimize the following two factors. Absorb those unwanted coherent packets of energy coming along the short reflected path from the speakers to the side walls to the listener (especially those that come at the listener from his front). And meanwhile reflect and further diffuse reverberant energy that has come on a long, multiple reflected path and is already incoherent and delayed (especially that which will come at the listener from his side).
Meeting these two desiderata simultaneously yields the rotational alignments seen in Figure 5. If you look closely, you’ll notice that the seams of the TubeTraps near the speaker along the side walls point almost perpendicularly’ into the room. Then, as you go backward in the room toward the listener, the rotational alignment of each successive column progresses toward having the seam point parallel to the side wall, and toward the front of the room. |
The reflector buttons seen here are positioned opposite the seam, and indicate the midpoint of the treble-diffusing half of the TubeTrap.
