Springbok10,
I don’t want to come across as trying to “sell” you on our speakers. This is a difficult fence to straddle though. What I will do is explain the physics involved in simplest terms and what our Revelations can accomplish in your situation. Other than that, there’s not much more that I can say. I’m not about to try and convince you or make you “feel good” about purchasing SP Tech product as I believe that to be unethical. First and foremost I’m an engineer – not a salesman. Besides, once a customer understands the principles involved, our products tend to sell themselves.
To begin, I have the greatest respect for Roy Allison. He was one of the pioneers that helped identify the issue and importance of room power response. Much of his philosophy has been a guiding principle behind our product design. In that, he developed speakers with the consideration of how speaker placement affected the final sound – hence, his corner placement concept. The physics behind his designs are as valid today as they were then.
The idea is that as you place a sound source (speaker) within the “pressure zone” (a function of wavelength) of a nearby boundary, that boundary effectively “disappears.” This means that the path length difference between the direct sound emanating from the driver and that reflected from the boundary is so short that no phase cancellations occur at any point distant from the source. Essentially, this means that there appears to be no reflection or “echo” whatsoever, even though the sound is reflecting off of the nearby boundary. The principles involved “pressure zone” theory are a bit involved, so I’ll only provide a cursory overview.
Besides the “apparent” elimination of reflection effects, what also happens is that the effective sound pressure doubles. This will cause a 6dB increase in SPL with respect to the sound pressure that would be measured if there were no nearby boundary. Now… not to confuse you, but that also means the total acoustic power radiated appears to double – an increase of 3dB. This is not really the case though – no new energy is being created. What is actually happening is that the field of radiation that the driver “sees” is being cut in half. This assumes that the boundary extends infinitely in all directions. To clarify, a speaker held up high in the air would radiate into a full spherical space – we call this 4pi space. When the source is placed against an infinite baffle, that space is cut in half or becomes a hemispherical space. We call this 2pi space.
This process is repeated for a second and then third boundary, which is what we encounter when placing the speaker in a corner. If the speaker is placed far enough into the corner, then the corner seems to “disappear” and the bass output greatly increases. This is also why the Klipshorns were designed to be placed in a corner and also why we designed our “Infra-Wave” subwoofer for corner placement. Essentially, by doing so one gets what appears to be a lot of “free energy” or extra bass output for no added electrical power input. If the speaker is designed to take advantage of this free “acoustic gain” then the demands on the woofers (and the driving amplifier) can be greatly reduced. You must remember, a reduction in drive power from the amplifier of only 3dB means that the amp only has to deliver ½ of the power that it otherwise would. When you consider the acoustic gain provided by corner placement, a 200-watt amp seems more like an 800-watt unit when driving a speaker designed for corner placement.
So…how would the Revelations work in a corner placement scenario? Well, if the system were left “untreated” you’d end up with enormous amounts of bass output. Also, the closer you get them into the corner, the SMOOTHER the frequency response would be. Yes, it would be greatly boosted in output compared to that at mid and higher frequencies, but over the region that is “acoustically amplified” by the corner, the actual frequency response would be smoother than if the speakers were placed out further into the room. This is one of the great advantages of “pressure zone” placement, beyond that of the extra bass output. In fact, this effect is often taken advantage of by recording studios to eliminate early room reflections. Often studio designers will mount the speakers into the control room wall, such that their front baffle is flush with the wall.
Now, with the Revs you obviously can’t get their front baffle into the corner like the Allisons, so there would be a “transition zone” where the radiated field that the speaker sees changes from approximately 1/2pi space (the corner effect) to 4pi space (a spherical “no wall” condition). This will cause some “ripple” in the frequency response through the transition region and consequently affect the soundstage and imaging abilities a bit. FORTUNATELY though, due to the waveguide technology employed in the Revelations, this “ripple” (and any consequential impact on imaging) will be greatly minimized as compared to virtually any other high-end speaker design.
This is for two reasons. First, the waveguide controls and narrows dispersion from about 1KHz on up to 10KHz such that the horizontal field is limited to about 120 degrees (+/- 60 degrees from the main forward axis). This is not a trivial advantage. Second, the waveguide allows us to crossover at 700Hz. This helps to “slow down” or make the transition a more gradual process as the front baffle limits the radiated field from the tweeter to a 2pi (hemispherical) field down to about 650Hz. Seeing that the front baffle can be no closer to the wall than 15.75 inches (the depth of the enclosure), this places the waveguide/baffle out into the room a fair distance such that the wave front will have expanded out into the room considerably before reaching the walls and reflecting.
The upshot is that yes… imaging will be affected slightly, but far less than virtually any other speaker design. In fact, in the critical upper mid and high frequencies where the ear is most sensitive, the side walls will have essentially no negative impact on the sound field. Actually, in that respect the Revelations would even be superior to the Allsions. If you notice, their tweeter and midrange will suffer far more from sidewall effects as they have no form of “wave directing” device. As they are essentially mounted on a flat baffle, they will exhibit an immediate 2pi (180 degree) radiation pattern. Since they are not close enough to the side walls to be in the pressure zone over most of their operating frequencies, the sound wave emanating from them WILL reflect off of the sidewalls in such a way as to cause significant frequency response ripple. Again, this would most likely result in a fairly significant degradation of soundstage and imaging – especially seeing that the effect would occur throughout the highly important upper midrange and high frequency regions. I can virtually guarantee that over that frequency region, the Revelations would easily outperform the Allisons.
