A Question of Balance
From the outset, development of our new powered UPA speakers was a delicate balancing act. On one hand, we wanted to make the new powered versions as much like the non-powered ones as possible. The UPA Series has been a perennially successful product for over 17 years. That made us reluctant to tamper with basic design parameters.
On the other hand, we didn't want to merely insert an amplifier module in an otherwise unchanged product, since our latest research made significant refinements possible in overall performance.
So when the powered UPA project kicked into high gear in late 1996, we set down three fundamental design goals:
The Front Could Fool You
From the front, it's hard to tell the new powered UPA from the original. The cabinet has the same dimensions. The handles and rigging points are the same. The driver complement is the same: a 12-inch cone low-mid driver and a 3-inch diaphragm HF compression driver. The exterior finish is the same. And despite the considerable amplifier and processing power packed inside, the powered versions are only 10 pounds heavier-which means integration into most installations won't require new rigging.
In other words, from the point of view of sound designers and installers it's still a UPA. You can put it in the same place, and you will get equivalent response with the same underlying sonic signature. If you've designed a system and specified UPA-1Cs, you can safely substitute powered versions without redrawing your plans and starting your acoustic modeling all over again.
To satisfy a wide range of requirements, we built two different powered UPA versions. The UPA-1P uses a newly designed 100-degree x 40-degree horn for wide coverage from a single speaker, while the UPA-2P uses the same horn as the UPA-2C with a more tightly focused 45-degree x 45-degree pattern.
The new horn designed for the UPA-1P exhibits exceptional constant Q performance on both the vertical and horizontal axes. The -6 dB points are remarkably uniform across the full frequency spectrum, and it holds the 100 degree pattern all the way up to 16 kHz.
This new horn design was modeled on previous work for the CQ™ horn series. However, making the concept work successfully in the UPA package required long hours spent testing dozens of horn iterations in Meyer Sound's own anechoic chamber. Every prototype was checked at 1 degree angular increments with 1/36 octave frequency steps. This is still the only way to get absolutely reliable results. The computer programs for horn design, though improving, are still not sufficiently precise to predict horn behavior with complex shapes, at least not with the degree of precision we require.
Also, with the self-powered UPA we have implemented a higher level of phase correction. Phase response is held within ±35 degrees from 600 Hz to 14 kHz. The practical result is better image localization. As we move into more multi-channel "surround" sound in all kinds of entertainment systems, phase response will become an increasingly important consideration.
Also, both the horn designs and the processing electronics incorporate new approaches to establishing a common acoustical center at all frequencies. A common acoustic center allows powered UPA units to be stacked in line vertically and then rotated on a single, defined acoustic axis. This is handy if you can't array several units horizontally due to space limitations. You can stack them and splay the horns at different angles for wider coverage - but without lobing effects! The underlying principle marks a significant departure from conventional approaches, and a patent application is pending.
The two amplifiers inside each powered UPA represent the latest refinements of Meyer Sound's continuing development of complementary MOSFET designs. The amplifiers employ a bridging Class AB topology in full conduction mode, which means that the output devices are on all the time. (They are not switching on and off constantly like a conventional Class B design.) The result is a very smooth output with excellent control of the drivers.
In a sense, we took a conservative approach on the amplifiers. We could have saved a few pounds by pursuing a pure Class D digital switching design. But even the best new Class D amplifiers exhibit a grainy quality that we found unacceptable for delicate music reproduction. With the UPA's reputation for superior sonics at stake, we tipped the balance in favor of the best sonic performance. Saving two or three pounds, we decided, was not a significant benefit in a 70-plus pound unit.
The UPA amplifiers are driven by a differential balanced input circuit with RF filtering. Common mode rejection is typically better than 90 dB, and connection with inexpensive twisted pair cable is essentially noise-free on runs, even in intense RFI/EMI environments.
For those installations requiring computerized system control, the UPA-1P and 2P are compatible with Meyer Sound's RMS™ Remote Monitoring System.
For applications requiring exposed outdoor installation, weather protected versions of both speakers are available.
The powered UPA speakers are direct descendants (one generation removed) of one of Meyer Sound's pioneering UM-1 Ultra Monitor.
The Ultra Monitor was developed in response to the problems encountered by rock bands in the late 1970's, when increasing sound levels on stage were drowning out the stage monitors. Meyer Sound worked with several bands, most notably the Jefferson Starship and the Grateful Dead, on designing a compact, low-profile monitor that could achieve SPLs in excess of 110 dB. We discovered that conventional designs of any allowable size would go into overload at those levels, so we had to try another route.
Limiting the bandwidth, bass in particular, would allow us to achieve higher levels and excellent vocal intelligibility. But doing so at all times was unthinkable, since the vocalists want to hear full range music reproduction. Consequently, we developed a "smart" processor that introduced subtle bandwidth limiting only on the very high peaks, such as when the vocalist was shouting directly into the microphone.
This approach allowed us to push SPL up over 130 dB (at 1m) while maintaining low distortion. The processing generated no audible artifacts, and extensive tests showed the effect was transparent on all kinds of program material.
In 1980, we took the technology developed for the Ultra Monitor and applied it to a PA speaker, the original UPA-1. The primary difference was in the high frequency horn: the Ultra Monitor had a 'spotlight' horn to focus on a single performer, where the UPA-1 had a much broader pattern to cover wide audience areas.
At that time, speakers capable of producing a clean 120-plus dB were heavy, bulky and not designed for arraying. The UPA-1, in dramatic contrast, was small, relatively lightweight, and a patented trapezoidal cabinet specifically designed for rigging in arrays. Though relatively tiny, it could produce peaks at 1m of over 130 dB when used with a good 300W stereo amplifier.
It was an immediate sensation-particularly among sound designers for Broadway theatrical productions. The UPA gave them the ability to project higher levels of clean music program without cluttering stage sight lines.
The basic advantages are fairly straightforward. With powered speakers, you can design the amplifiers for optimum performance because reactance for each transducer is a known quantity. This allows significant weight reduction without sacrificing reliability, because there is no need to engineer the amplifier to deal with a wide variety of unknown operating parameters.
Also, with the amplifiers are inside the cabinet, you don't have to deal with high frequency losses from cable capacitance, or the sonic compromises of 70V distributed systems. System setup is simplified because you go from line level output directly to the speaker: no separate amplifiers or processors to hook up, so no chance of wiring mishaps.
On a more subtle level, the powered speaker concept just makes more sense in the new "post stereo" era of entertainment audio. The basic stereo model (two speakers driven by one stereo amplifier) is on the way out. The 5.1 standard of cinema sound is moving out into music recording, and we can expect an explosion of multi-channel sound as DVD takes hold.
Also, theatrical presentations (most notably in Las Vegas) are using multiple output channels for complex sound localization effects. In such systems, the complete powered speaker package offers much greater flexibility and ease of installation.
The UPA concept has a long and enviable track record. After over 17 years, it continues to outperform and outsell newer competitive designs. In the new UPA-1P/2P, Meyer Sound has taken this proven concept to a higher level of performance and flexibility.
True, it may look like, hang like and even basically sound like a
non-powered UPA. But in critical applications, we believe most users
will find that the powered UPA offers noticeable sonic refinements
along with the enhanced operating flexibility inherent in a self-powered
system with computer control facilities.