System Frequency Response Optimization:
The frequency response of a sound system is not a constant function within any venue. Essentially there are two elements that determine overall frequency response of a sound system within a venue. Unsurprisingly, these two elements are the sound system itself, and the venue.
A sound system that is set up according to the Sunsonic Criteria, and that employs well designed, high quality system components, will exhibit an acceptable, even frequency response. What this means is that the ratio of output level of the system to input level will be fairly constant regardless of the frequency of the input signal. However, there are a number of issues that make this all more complex than many sound equipment manufacturers would like you to think.
Almost all sound systems have substantially different directivity at different frequencies. Very low frequencies have omnidirectional propagation characteristics, whereas higher frequencies can be more easily directed. This is simply due to the fact that to manipulate the directivity of a sound wave, a horn structure is required. The size of a horn structure required to implement a given directivity is proportional to wavelength, which is inversely proportional to frequency. To provide a high degree of directivity at a frequency of 20Hz for example, requires with a horn structure with a throat length of over 30 feet. The result with most sound systems is then generally that the full range cabinets are much more directive than the bass cabinets, so if one stands far from the speakers, along the axis of the horns in the full range cabinets, the bass will be much lower relative to the mids and highs. In contrast, if one were to stand near the speakers, but to the side, and hence not on the axis of the horns in the full range cabinets, the bass would be much louder than the mids and highs. So, in this type of system, there is already a large amount a variation in the frequency response of the system based simply on where the listener happens to be.
The fix for this issue is simple: Use full range cabinets that have low directivity. This ensures all frequencies are radiated with fairly equal intensity across the entire view of the speaker cabinet.
For very large sound systems, frequency response and SPL uniformity concerns become major design issues. However, upon review of the “Characteristics of Dance Music” Section in this document, it becomes clear that SPL uniformity is not always our goal. Thus these design issues, which can be very complex, are not much of an issue typically for underground dance music. In a sense then, the old principle of K.I.S.S. (Keep It Simple, Stupid) proves itself here to be true.
This document © David X (United Records, Sunsonic Sound System) – http://www.unrec.com/ & http://www.unrec.com/sunsonic/sound2.htm
