Mordaunt-Short MS3.30 Speaker System Review

As Mordaunt-Short succinctly describes it, the MS3.30 loudspeaker is a “medium-sized vented system with front-facing reflex port, intended for use on floor stands, in small to medium-sized listening environments.” To this can be added that it is a two-way system, with an 8-inch woofer and a 1-inch dome tweeter, and that it is affordably priced.

In common with many other products, however, especially speakers, there is a lot more to the MS3.30’s design and construction than can be conveyed by such a brief description. The particleboard cabinet (about 5/8 inch thick) has a two-layer, injection-molded front baffle made of a poly-propylene-based plastic. The baffle is light in weight, with molded internal ribs to control vibration. Considerable care has been taken to minimize diffraction by rounding the side edges of the baffle and fitting rubber rings around the driver frames, effectively eliminating any discontinuity at the junction with the front panel. The frameless cloth grille, with elastic sewn into its edge, is retained by inserting its edge into a groove around the periphery of the cabinet.

The nominally 8-inch bass driver, which has an actual cone diameter of 6-1/2 inches, is constructed on a die-cast aluminum basket. Its 32-millimeter-diameter voice coil is wound on an aluminum former and bonded with high-temperature resin. The cone is formed of polypropylene, with a synthetic rubber surround and an injection-molded dust cap bonded directly to the voice’ coil.

The woofer was designed to have a natural response rolloff above its pass-band, eliminating the need for a low-pass filter section in the crossover network. This omission of the usual series inductor is also said to improve the driving amplifier’s electrical damping effect on the woofer.

The 1-inch aluminum tweeter dome is supported by a polyamide suspension. Magnetic fluid in the voice-coil gap stabilizes and damps the dome’s motion and improves heat transfer from the voice coil to the magnet system. The tweeter dome is said to operate as a piston well beyond audible limits, with its lowest break-up mode occurring at 25,000 Hz. As with the woofer, the crossover components have been reduced to a minimum, with only a single polypropylene capacitor in series with the tweeter voice coil.

To protect the system from damage by overdriving, each driver has a Positec device (a type of bistable resistor) in series with its voice coil. Normally, these have a very low resistance and do not affect the speaker’s performance. When an excessive signal voltage is applied, the resistance of the Positec device increases rapidly and reduces the current through the voice coil to a safe value. When the overload is removed, the resistance quickly falls to its original value.

The MS3.30 was designed for optimum performance with the cabinet placed from a few inches to a foot in front of a wall, at least 18 inches from a side wall, and high enough to place the woofer axis (near the top of the cabinet) approximately at the listener’s ear level. Mordaunt-Short makes a novel speaker stand, whose height is adjustable over a wide range, that can be used with any of the five speakers in the MS3 series (the MS3.30 falls midway in the line).

The MS3.30’s specifications include a frequency response of 60 to 22,000 Hz, a sensitivity of 90 dB, and a nominal 8-ohm impedance. It can be used with amplifiers rated between 15 and 300 watts per channel, although the suggested upper limit is about 100 watts. Gold-plated multiway binding posts that accept dual banana plugs are recessed into the rear panel. Each speaker measures 18 inches high, 9-1/4 inches wide, and 10-3/4 inches deep and weighs 18 pounds. The cabinet is available in black-ash or rosewood vinyl laminate, with a black front panel and grille. Price: $459 a pair; MS3.1S stands, $129 a pair.

Lab Tests

We installed the MS3.30 speakers on the MS3.1S stands at their full height of 21-1/2 inches. Although the manufacturer supplied response measurements run on our samples of the MS3.30, we found very little correlation between those data and our own. Clearly, the test environments and conditions were quite different.

Our composite response curve was very smooth through the bass and midrange, varying only ± 2 dB from 50 to 2,000 Hz. At higher frequencies the response, though still very smooth, sloped downward by about 5 dB from 2,000 to 10,000 Hz and then rose by about 3 dB from 10.000 to 20,000 Hz. The curves plotted from the left and right speakers had almost identical shapes, although the right speaker’s output, measured 30 degrees off-axis, was 3 to 5 dB lower than the on-axis output from the left speaker over the range from 1,500 to 20,000 Hz. This result is fairly typical, representing the speaker’s increasing directivity at high frequencies.

Mordaunt-Short does not specify the system's crossover frequency, but the company’s test data suggest that it is about 4,000 Hz. No clear evidence of a crossover was visible in our measurements. The bass response (close-miked) was flat within ±1 dB from 85 to 600 Hz, with irregularities appearing at higher frequencies because of interference from energy received from different parts of the cone. At low frequencies, the output sloped off at 6 dB per octave below 60 Hz, to -11 dB at 20 Hz.

Quasi-anechoic response measurements made with the IQS FFT system essentially confirmed the room-response measurements in respect to the downward-sloping high-frequency response. Similarly, the horizontal-dispersion measurements over a 45-degree angle followed the pattern we had observed in the room response. The curves measured on-axis and at 45 degrees off-axis were very similar except for their levels, which differed by 5 or 6 dB over the full range from 1,000 to nearly 20,000 Hz. The tweeter resonance at 28,000 Hz caused a rise in output above 20,000 Hz, to a maximum of +12 dB, followed by a sharp 22-dB drop at 29,000 Hz. Group delay was constant within 0.1 millisecond (ms) from 3,000 to 20,000 Hz, but this variation increased to 0.4 ms or more at several frequencies within the woofer’s operating range.

The minimum system impedance was about 7.3 ohms at several frequencies between 180 and 400 Hz and between 15,000 and 20,000 Hz. The maximum of 22 ohms occurred at 73 Hz.

The MS3.30 had a sensitivity of 91 dB sound-pressure level (SPL) at 1 meter with an input of 2.83 volts (equivalent to 1 watt into 8 ohms), slightly higher than the rated 90 dB. Distortion at a 2.55-volt drive level (corresponding to a 90-dB SPL) was between 0.4 and 0.5 percent from 100 to 2,000 Hz, rising to 1 percent at 4,000 Hz. The output from the port predominated below 80 Hz, and its distortion rose from 1 percent at 80 Hz to 20 percent at 40 Hz.

A single-cycle tone burst at 100 Hz produced a loud rasping sound at a level of 355 watts into the speaker’s 12-ohm impedance at that frequency. This signal apparently was not sustained long enough to trip the Positec protection, and it did not harm the speaker in any way.

Comments

With some program material, the MS3.30’s sound had a slightly bright quality that seemed inconsistent with the shape of its response curve. Sometimes this quality was heard as a “presence,” or forward character, to the sound, which is usually associated with an increased output in the upper midrange. Most of the time, however, it was not obtrusive and would not be noticed except in comparison with speakers not possessing it. We found the MS3.30 to be a pleasant-sounding, always listenable speaker, easily able to hold its own (or better) in a comparison with other speakers in or not too far above its modest price range.

Compensating in some measure for its brightness, the MS3.30 proved to have exceptional imaging qualities, as demonstrated by the Chesky “Jazz Sampler" CD. Not only did it have excellent left/right imaging, but its vertical imaging was among the best we have heard from any speakers playing that disc.

The Mordaunt-Short stand is unusual, being composed of a number of small modules (“vertebrae”) that can be stacked to form a column (“spine”) to support any Mordaunt-Short MS3 series speaker at a height from a few inches to 21-1/2 inches off the floor. The three-point base can be fitted with flat support feet or adjustable spikes (we chose the feet). Although the support column had some lateral flexibility, as befits a spine, it appeared to be very rigid on its vertical axis. At any rate, it was an ideal support for the MS3.30 speaker, which screwed firmly to its top plate.

In sum, then, the Mordaunt-Short MS3.30 is a fine value in its price range and altogether a very satisfying speaker to listen to and live with.

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