Some listeners claim that this ringing is audible and objectionable, even though the ring decay time is almost always much shorter than that of the system feedback which the filter suppresses. Others observe that wisely used notch filters can suppress the apparent room reverberation as excited by the system, thus improving its sound quality.
In many cases, feedback suppression can allow the system level to be turned up enough to make a very desirable improvement in performance. But always keep in mind the key portion to this approach: notch filters must be wisely used or they can have a highly negative impact.
In my previous article, I began the discussion that has continued here, regarding factors that define a “good” system.
Note that with regard to all of them, as a group, the professional audio industry has a long way to go before reaching many concrete solutions. Why is that?
Our problems are interdisciplinary, and require “in-situ” measurements of many factors in both subjective and objective domains. This requires proficiency in several rather complex disciplines.
To this point, very few in our industry possess these specialized skills, and further, as a group we’re not prepared to fully understand this information. Don’t get me wrong—we’re not stupid, it’s just that the issues are highly complex. Multiple variables can be involved, but not readily apparent.
A major problem is simply isolating the variables from one another. At this point in time, it’s a huge challenge. Further, the parameters involved are poorly defined. In fact, a major goal of research in this area is simply to isolate, identify, and define the significant parameters. It would seem that this is the obvious starting point, but many issues are so poorly understood that such is not yet possible.
Bob Thurmond’s sound system performance evaluation. (click to enlarge)
Plus, we’re all human, with significant opinions and prejudices. This is always a danger in any type of scientific investigation, but it may be even more significant here because of widespread prior experiences, good and bad, with sound systems.
Finally, sound reinforcement professionals often respond to the research results that do exist with skepticism or outright rejection. It seems that many of us like to feel that our knowledge and understanding of the craft is more than adequate, and to be honest, we can feel threatened by any challenge to our competence.
And now we’ve come full circle! The key problem is the lack of understanding of the relationship between objective and subjective factors.
Until we reach some sort of consensus, real progress on the true definition of a good system, let alone the application of what we learn, still seems a long time coming.
Bob Thurmond is principal consultant with G. R. Thurmond and Associates of Austin, Texas. This paper was originally presented at the 146th Meeting of the Acoustical Society of America, Session 4aAAa.