acoustic system resonators

Placement is key for best results with most resonator devices, at least the one that are intended to reduce standing waves in the room, such as room lens, tube traps, even mpingo discs. Arbitrary placement can lead to, well, non-optimum results. While the ear can often achieve pretty good results, much better results are achieved using test tone and sound pressure level meter, so the precise location of standing waves (high sound pressure zone) can be ID'd. The resonators should be placed where the exceptionally high sound pressures are observed.

For example, a tube trap might actually hurt the sound when placed directly in room corner (as is often suggested); but when placed according to test tone/SPL meter a couple feet from the corner, the sound is much better.

~ Cheers

A Sound Level Meter can determine locations in the room for resonators with better accuracy in many cases than following general instructions or the old "move and listen" technique. YRMV.