EPI T/E 320 Series II Speaker System Review

The EPI Time/Energy (T/E) series of loudspeakers was designed to provide an accurate transient response as free as possible of “ringing” and other time-domain distortions. To achieve this, EPI (which makes all its own drivers) developed a dualcone construction that is used throughout the T/E series.

Each cone driver in T/E series systems, as well as the domes of the high-frequency drivers, is made of two layers, one rigid and the other compliant. The outer cone is formed of stiff, light clear-polycarbonate plastic. The inner cone, molded as an integral piece with the compliant edge-surround, is made of polyurethane foam and provides damping of cone resonances. The two layers are bonded by a combination of adhesives, pressure, and heat to form a single part with excellent mechanical properties, and additional damping is applied to the cone edge and suspension.

The EPI T/E 320 Series II is a floor-standing three-way system whose 10-inch acoustic-suspension woofer crosses over to the midrange driver at 300 Hz. This low crossover frequency allows the woofer to be located near the bottom of the front panel for optimum bass performance with a minimum of influence from the room boundaries. The midrange and high-frequency drivers are closely spaced and vertically aligned near the top of the enclosure, close to the level of a seated listener’s ears and slightly to the right of the speaker’s center line. The rear of the 4-inch midrange driver cone is isolated from the woofer by a dual-chamber housing. The crossover to the 1-inch dome tweeter takes place at 2,500 Hz.

The nominal impedance of the EPI T/E 320 Series II is 6 ohms, and its rated sensitivity is 88 dB sound-pressure level (SPL) at 1 meter with a 1-watt input. The suggested amplifier power range is 15 to 250 watts, and the rated frequency response is 38 to 20,000 Hz.

The speaker is housed in a handsome oak-grain, vinyl-clad cabinet measuring 34-1/4 inches high, 13 inches wide, and 10 inches deep. It weighs about 35 pounds. The dark-brown cloth grille unsnaps to reveal a fully finished speaker board. The spring-loaded connectors on the rear of the cabinet are designed to grip the stripped ends of speaker wires and will also accept twin banana plugs. Price: $550 a pair.

Lab Tests

The room response of the EPI T/E 320 Series II showed the usual bass and midrange irregularities caused by room-boundary effects, although its average level was quite uniform across the audio range. The close-miked response of the woofer peaked at 65 Hz, dropping at 12 dB per octave below that frequency and at 6 dB per octave above it. At the 300-Hz crossover frequency, the woofer’s output was 10 dB below its maximum.

We also measured the midrange driver’s output with close microphone spacing, and it varied about ± 2 dB from 300 to 2,000 Hz, falling off rapidly outside those limits. When the close-miked measurements were spliced to the room-response curves, the resulting composite frequency response was very close to EPI’s rating, within ±4.5 dB from 38 to 20,000 Hz.

Quasi-anechoic response measurements made with our FFT analyzer showed an output variation of only ±3.5 dB from 300 to 23,000 Hz on the axis of the system. The response at 45 degrees off-axis began to fall off above 8,000 Hz and was down about 15 dB at 15,000 Hz. The group delay varied only ±0.2 millisecond from 2,000 to 23,000 Hz, indicating a highly linear phase response.

The system’s sensitivity was 89 dB spl, slightly higher than rated. Its impedance reached a minimum of 4 ohms at 1,000 Hz and a maximum of 20 ohms at the 45-Hz bass resonance; it varied between 4 and 10 ohms, with an average of close to 6 ohms, over most of the audio range. We measured the bass distortion with an input of 3.2 volts (equivalent to 90 dB spl at 1 meter). From readings of under 0.5 percent above 75 Hz, the distortion increased smoothly to 6 percent at 50 Hz and 11 percent at 40 Hz.

The T/E 320 Series II acquitted itself very well in high-power tone-burst tests. At 100 Hz, the woofer gave a slight rattle with an input of 580 watts into its 4.8-ohm impedance. At 1,000 Hz, where the system’s impedance was 4 ohms, it had no difficulty handling the 1,580-watt output of our amplifier at its clipping point. At 10,000 Hz, amplifier clipping once again set the limit to our measurement, at 1,215 watts into 5.2 ohms.

Comments

The sound from the EPI T/E 320 Series II was uncolored and very neutral. It did not impart unnatural heaviness to voices, and its upper range was clean and extended. In fact, there was little one could criticize in its sound, which was always musical and listenable.

Obviously, the lowest bass is not this speaker’s forte, although it does not give an impression of being bass-shy. This is understandable when you consider that its bass response, despite falling off below 65 Hz, was still present in useful amounts down to 40 Hz and lower. Even the rapidly rising bass distortion below 60 Hz or so was not as much of a drawback as it might seem, since it consisted almost entirely of third harmonics and did not sound irritating. In fact, it gives the listener an illusion of deeper bass than is really present.

The EPI T/E 320 Series II is not only easy to listen to, it is good to look at. It is one of the very few speakers we have seen that looks at least as good with its grille removed as with it in place. The shiny gray plastic cones and attractive wood-grain finish are certainly more interesting to look at than a featureless grille! Priced at little more than an ordinary bookshelf speaker, it strikes us as a genuine bargain in today’s market.

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