Tower Speaker Reviews

John Atkinson performed the measurements on the Pioneer TZ-F700 and TZ-C700 after I completed all of my listening tests.

Beginning with the TZ-F700, its sensitivity is a very high 93.6dB/W/m (B-weighted). This is about 5dB higher than is typical for, say, a THX loudspeaker, and indicates that the Pioneer should work well with modestly powered amplifiers. The impedance is shown in Fig.1. The minimum value, 3.4 ohms, falls at 387Hz. While this is close to the IRIS compound mid-tweeter's rated crossover frequency, the nearfield measurements indicate that this crossover is nearer to 238Hz (acoustical)—well below the specified value of 450Hz. The rise in the low frequencies is likely due to a series capacitor in the crossover to the powered subwoofer. (The curves in Fig.1 reflect only the impedance of the "unpowered" portion of the TZ-F700.) The TZ-F700 should not be a particularly difficult load to drive for any competent amplifier, but I would avoid receivers that are not rated to drive loudspeakers of under 6 ohms.

Fig.1 Pioneer TZ-F700, electrical impedance (solid) and phase (dashed). (2 ohms/vertical div.)

Fig.2 shows the on-axis response averaged across a 30-degree lateral window, combined with the nearfield woofer response (the latter derived from a complex sum of the woofer and port). Aside from a rise in the bass (the degree of which can be controlled by the woofer-level control) and a slight rise at 10kHz and above, the response is admirably flat, particularly in the region covered by the IRIS—which, from my listening tests and these measurements, appears to be a superbly designed device.

Fig.2 Pioneer TZ-F700, anechoic response on upper-midrange tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with the complex sum of the nearfield woofer and midrange-unit responses plotted below 400Hz.

The TZ-F700's horizontal dispersion is exceptionally well-controlled, the off-axis response rolling off smoothly and progressively with increasing frequency—a characteristic that should provide for pinpoint imaging. This is another indication of the IRIS driver's high quality. The vertical dispersion is also very wide. The treble response holds up well, to over 2' above and below the tweeter—an exceptional result—making listening height not at all critical.

The TZ-F700 has reasonable impulse and step responses, but, as with virtually all loudspeakers, the drivers are not time-coherent. The waterfall plot indicating the loudspeaker's delayed resonances is very clean.