ServoDrive Sound Physics Labs TD-1 Speaker

by Will James

Product Points

Applications: Live sound; contracting/install; theater Key Features: Compression-loaded speaker cabinet; 2x12", 4x5" speakers' 1" HF driver; ATM flytrack; passive, biamp or triamp operation; Neutrik NL4 and NL8 connectors Price: $3,495 Plus New full-range horn technology Clean sound Minus Pricey The Score A unique and innovative live speaker design that yields an impressively smooth and wide output. Contact: ServoDrive at 847-724-5500 Web Site

Most people - and audio pros are no exception - have a tendency to stick with tried-and-true tools. By doing so, however, we limit ourselves from some very happening new equipment. I am just as guilty as anyone else, but since I started reviewing gear for PAR, I have discovered some outstanding, exciting new gear and interesting new technology. One such product is a speaker system developed by ServoDrive called the Sound Physics Lab (SPL) TD-1.

Features

The SPL TD-1 ($3,495) is an interesting combination of components and design, created to offer extended coverage patterns, but packaged in a modestly sized cabinet. The cabinet is only 29 inches tall, 23 inches deep and 19 inches wide, weighing in at 120 pounds. Four conveniently placed handles and recessed ATM flytrack make it easy to place or hang the TD-1. The speaker can be operated passively, biamped or triamped by rotating a switch on the back panel, which also contains two Neutrik NL4 and two Neutrik NL8 cable connectors.

The placement of speaker components is unique - unlike anything I have seen before. The cabinet is essentially a 30-by 60-degree horn, with three different types of components, but all are compression loaded, feeding directly into the horn cavity. There is a pair of 12-inch transducers mounted opposing each other at 30 degrees, one mounted on the bottom inside surface of the horn facing upward, and the other mounted on the top inside surface of the horn facing downward.

At the rear of the horn cavity, just above the throat, are four 5-inch speakers facing into the horn. At the center is a 1-inch driver that faces directly into the geometric center of the horn cavity.

Remember, all the components are compression loaded, which generally presents some nasty problems. One problem associated with compression loading of multiple bandwidths into a central horn is the time/phase disturbance created by forcing several programs together that were created at different distances from the center of the horn cavity.

The idea behind the TD-1 is to position the varying components' acoustic centers at exactly the same point in space, thus eliminating those time/phase problems.

Another problem is that most horns have a cutoff frequency, just like a reflex cabinet - all enclosures, cabinets or horns are designed to propagate certain frequency ranges. There is no one horn that effectively radiates all frequencies equally. The TD-1 horn speaker is designed to eliminate such problems by properly blending the frequencies at the appropriate balance so that they peacefully coexist in one horn.

In use

I provide sound equipment and engineering for the Phoenix Symphony - truly a perfect setting to test the fidelity and listenability of a speaker system. One of the problems I have at Phoenix Symphony Hall is providing even audio at consistent levels for the balcony seating area. There are good speakers in use that attempt to address this issue, but they do not provide even coverage at that distance because of the narrow dispersion factor associated with conventional cabinets. This was the perfect opportunity to try out these TD-1s.

I placed them on the top of my own speaker system about 75 feet apart and aimed them up at the balcony in a crossfire fashion. I originally intended to tilt them up and back, but the black paint-spatter/orange-peel finish was too slippery (that finish being on both the TD-1s and my own system), so I rested them squarely on my speakers, relying on the exponential curvature of the TD-1 horn to do the work.

I must admit that when I first saw the Sound Physics Lab TD-1s I had my doubts. After hearing them, however, I was impressed. The TD-1s had a very smooth, flat frequency response in the zone ServoDrive said they would (60 Hz to 20 kHz +/-3 dB).

The horn broadcasted very nicely up to the outer reaches as well as the center of the balcony, with only three frequency cuts of no more than 4 dB on the graphic EQ. The horn dispersed all frequencies quite evenly throughout the listening area and did not suffer from the usual collecting of higher frequencies in the center of the horn throw.

I wanted to learn more about these speakers, so I contacted the manufacturer. ServoDrive recommended arraying the speakers side by side to see if I experienced another negative phenomenon associated with horns - the coupling of the mouths or apertures. This is typically a problem related to the horns radiating sound from two different starting points, causing even more time/phase problems.

The TD-1s were absolutely smooth at the confluence of their horns, with no negative coupling effects, proving the theory of radiating audio from horns sharing the same plane of origin, or as the manufacturer says "the same acoustic center."

Summary

The SPL TD-1 speaker is a very friendly speaker to listen to for extended periods of time. I was most impressed with the amount of knowledge and development on the part of the manufacturer. Horn technology is an aspect of radiating sound that is too often overlooked or presented improperly.

I believe that ServoDrive has come up with a most impressive solution to the horn problems that plague live sound applications. The TD-1s projected sound exceedingly well and represented all frequencies very evenly, not only in the usual mid-range and high-frequency range, but full spectrum.

It is a fairly new product and there are not many of them out there yet, but if you get the chance, I highly recommend giving them a listen.