@tomic601 wrote: " Duke...nicely thought out BUT in the case of an acoustic event recording in the space a nicely placed microphone captures first arrival and subsequent arrivals, that information IS encoded in the wave form over long periods of time, well past first arrival. So if the bounce is already in the waveform, why add another off the back wall ? "
Excellent question, goes right to the heart of the matter. Unfortunately my answer is not going to be as succinct.
When we listen to recorded music, there are TWO venues in play: The FIRST venue is what’s on the recording (whether it originated in an actual acoustic space or was synthesized by the engineers). The SECOND venue is the room we listen in. At the risk of oversimplifing: FIRST venue GOOD, SECOND venue BAD.
So we want to the first venue cues to be effectively presented, and the second venue cues to be as innocuous as possible.
An effective presentation of the first venue cues would have them come from all around, which implies having a lot of reflections. Also those reflections should have a spectral balance that mimics the first-arrival sound - when they do not, they are more likely to sound unnatural.
So, by correcting the spectral balance of the reverberant energy via a rear-firing tweeter, we are making the second venue cues less obtrusive.
But, we need to look at the time domain as well. The relatively short reflection path length of that rear-firing tweeter makes is an early reflection. And we know from the experience of countless Maggie owners that rear-firing energy sounds good when there is a long time delay, and bad when there is a short one (clarity is degraded and second venue cues are emphasized). So with speakers close to the wall a rear-firing tweeter may not always be a net benefit. Having spent a fair amount of time working with secondary arrays of drivers, I try to aim them in a direction that results in a relatively long reflection path length.
This long path length for the additional reverberant energy has an unexpected benefit: It makes the second-venue cues weaker!
Let me explain: The ear judges the size of a room by the time between the first-arrival sound and the "center of gravity" of the reflections. By injecting additional relatively late-onset reverberant energy via long-path-length reflections from additional drivers, we are pushing that center of gravity back in time, and we are making the second-venue cues more ambiguous. As a result the "small room signature" imposed by the second venue becomes less obtrusive, so it does not dominate the first venue cues as much as before. We hear more of the soundscape that is on the recording and less of whatever room we are listening in.
I don’t really expect you to believe me because this is a highly unorthodox idea being described by the guy who has a commercial interest in it. So here is my question to you: Are there any audio shows that you sometimes attend? I usually only do about one big show a year, but maybe just maybe we can cross paths at one.
Duke
