Tannoy PS-115

A no-frills, all-bass powered subwoofer that gave small nearfields a full extra octave - and low-end authority they never had on their own.

Overview

Every small-studio owner runs into the same problem. Nearfield monitors, however well behaved in the mids, can't move enough air to reproduce the bottom octave cleanly. Tannoy's answer was to hand the lowest two octaves to a dedicated box - a 15-inch driver in a sealed cabinet with its own amplifier and active crossover - and let the nearfields handle the rest of the music.

The PS-115 was the working engineer's sub, not a flagship. Tannoy already had the more sophisticated AMS 210A active subwoofer for people who wanted to match a high-end nearfield without compromise. EQ (January 1997, p.94) described the PS-115 as a stripped-down version of that model. The trade-off was deliberate. Buyers gave up some flexibility and got a straightforward, purpose-built low-frequency engine.

At the center is a stiff 15-inch driver in an 18-inch H × 20-inch W × 20-inch D cabinet (450 mm × 500 mm × 500 mm) that houses the power amplifier and active crossover. Tannoy's own literature describes the driver as a 15-inch long-throw transducer that extends low-frequency response to −3 dB at 33 Hz while still delivering high SPL, up to 114 dB peak. The amplifier is a modest 100 watts RMS. The whole thing is convection-cooled and needs nothing more than a few RCA cables to drop into an existing setup.

The active crossover is where the PS-115 earns its keep. It has a fixed 80 Hz high-pass filter that strips the low frequencies out of the full-range nearfields before they ever see them. That reduces cone excursion, stress and distortion on the smaller satellite drivers. Tannoy's documentation claims cone travel on the average nearfield is cut by two to three hundred percent as a result, which gives a cleaner, tighter mid-band from the decrease in group delay. A variable low-pass control then lets the user set the sub's upper cutoff anywhere from 50 Hz to 130 Hz to match where the nearfields naturally roll off.

Three things need adjusting: crossover frequency, subwoofer level relative to the nearfields, and subwoofer location. A bass guitar played up the scale should stay consistent in tone and perspective as it crosses the transition range. Tannoy includes a concise manual to help, and the review noted that a few minutes of adjustment was generally enough to reach a satisfactory tonal balance.

The connection scheme is simple and dated in ways that matter. A fully balanced version was said to be planned for spring 1997. The captive AC power cord has no ground lug, so all noise must be grounded through the RCA connection to the audio system. In very quiet rooms, a slight buzz radiates acoustically from the power supply transformer and is audible from the unit, not unlike some power amplifiers. The level control is also a little fussy, and it takes accurate gain setting to get the best integration.

The PS-115 does best in exactly the situation it was built for. EQ (January 1997, p.96) concluded that it was a very cost-effective way to add subbass to a monitor system, and that in most situations it would be a significant improvement in the ability of the system to produce low frequencies at higher listening levels. It let the nearfields "relax and produce the rest of the music with the tone that convinced you to use them in the first place." The output was judged capable of keeping up with anything from a modest 6-inch nearfield to punchy midfield units. At a list price of $1,095, it undercut the AMS 210A while doing the same essential job, giving a big, solid low end that can be tuned to match the room and the mains.

For collectors and studio owners today, the PS-115 is a purpose-built subwoofer from the mid-1990s project-studio boom. It uses a genuine 15-inch Tannoy transducer and a simple, serviceable amplifier/crossover package. The RCA-only input and ungrounded power cord are limits of the period rather than defects, and the transformer buzz and fussy level control are things an owner learns to live with. The 33 Hz to 130 Hz ±3 dB response and 114 dB peak capability are still useful numbers for a nearfield-plus-sub system. The fixed 80 Hz high-pass on the satellites is a feature many modern subs still don't offer out of the box. Parts availability and service documentation are the usual concerns for gear of this age, and buyers should verify the driver and amplifier work before committing.