Paul Barton: It Doesn't Get Much Better Than That:
Page 5
Atkinson: If you look at the measurements of speakers in Stereophile, so many two-ways will have a big crossover notch for a standing listener.

Barton: Absolutely! You know, you've just got to sit down, listen, then stand up. It's one of the greatest subjective speaker tests you can do. If the speaker sounds very similar in both cases, either the gods were in favor or the engineer was conscious of that. And that people's ears dominate the room from the seated position to the standing position, not from the seated position to the floor.

Atkinson: I was somewhat surprised to see that the Gold's woofer is in the exact center of its volume, its subenclosure. Intuitively, that doesn't seem right.

Barton: That was to locate the air inside the box as a lumped element so that the half-length from any high-pressure point—the boundaries of the enclosure—would be pretty much the same distance when the woofer is pressurizing or de-pressurizing the air. The port is located at the bottom of the enclosure, which is a high-pressure point as opposed to high-velocity. The two [factors] in combination result in a speaker that exhibits very little of the problems you usually get with slim enclosures, where two dimensions are much smaller than a third, defining a pipe of some kind.

Another factor in locating the port does not so much concern the lumped-element phenomenon that goes on inside the cabinet, but is a function of the higher frequencies that can escape through the port. And differences of inches in the position of that port with respect to the driver in that air space can change that dramatically. So, with all my designs, I experiment with reflections that occur inside the loudspeaker to try to minimize that phenomenon. The other alternative, of course, is to put the port on the back of the speaker, which attenuates it even more. In the case of the Gold i, the port is a big opening on the front of the box but it's optimally placed.

Atkinson: Perhaps you should explain that it actually doesn't matter where on the box you put the port or even the woofer, because they're so small compared to the wavelength of the sound they produce.

Barton: As we discussed earlier, at higher frequencies, when [the wavelength of the sound approaches] the size of the source of the energy, that sound source becomes very directional. The inverse is also true. When the wavelength is substantially larger than the driver, it tends to radiate omnidirectionally. So at the frequencies that the port covers, which are typically 50Hz and below, it doesn't matter what direction it's facing. The wavelength at 100Hz is 10', at 50Hz it's 20'. So when you have a port that's 4" in diameter [and] radiating wavelengths that are 20' long, it really doesn't matter where it is on the speaker.

Atkinson: The sound wraps around the box.

Barton: It just pumps up the power and energy around the speaker; just a little explosion going on.

Atkinson: The i is the first change in the Stratus Gold in seven years. And it's 10 years since you launched the Stratus series. What were you trying to achieve 10 years ago with the Stratus speakers that you hadn't yet achieved with the regular PSB brand?

Barton: Well, maybe I can go back and outline PSB's approach to design and what we wanted to present to the market: affordable, entry-level, and mid-fi, that was our corporate policy. But we wanted to have something we could hang our hat on; to say, "We're serious about this." When the relationship between myself and Lenbrook occurred, it was the first chance I had to develop a flagship. That's how the Stratus series came about. Since that first speaker, Stratus has evolved into a series that includes five models—soon to be six. The five models are the Stratus Gold i, the Stratus Silver, the New Stratus Mini, the Stratus C-5 center-channel loudspeaker, the C-6, which is a larger center-channel, and the Stratus Subsonic 4, which you saw at the WCES as a prototype. This will be a remote-controlled, high-powered 15" subwoofer built in the Stratus tradition.

Atkinson: Unusually, all the subwoofer's manipulation of the signal is done with DSP.

Barton: All of the filtering, compression, protection, position information, thermal information—all of those things are done in the digital domain. The Stratus subwoofer can have a 30-button remote control so you can control pretty much every parameter you can imagine from your listening seat. I think that what will probably end up happening is that we supply two different remotes: one with basic features, and one with all the ability to do anything the customer wants.