Floor Loudspeaker Reviews

As I suspected from reading WP's auditioning notes, the Hales Concept Five is not very sensitive. Driving it with 2.83V raised just 84dB at 1m (B-weighted), which means that it does need to driven quite hard by a reasonably powered amplifier. As can be seen from fig.1, however, its impedance is generally kind to the amplifier, staying above 8 ohms through the midrange and bass, and dropping only briefly to just above 3 ohms in the low treble.

Fig.1 Hales Concept Five, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

Note the glitch in both the magnitude and phase traces at 150Hz. Something like this is usually associated with a cabinet resonance problem. Indeed, using a simple plastic-tape accelerometer, I found a strong pair of resonances to exist in this region. Fig.2 shows a cumulative spectral-decay or waterfall plot calculated from the output of the accelerometer fastened to the front baffle between the midrange and woofer. While the midrange is totally free from resonant behavior, two strong ridges of delayed energy can be seen at the frequency of the impedance glitch. It is hard to say what they are due to and what their exact subjective effect will be, but I note that Wes was bothered by the speaker's lack of "swing." These resonances may be the appropriate "smoking gun" in this instance.

Fig.2 Hales Concept Five, cumulative spectral-decay plot of accelerometer output fastened to center of front baffle. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)

Fig.3 shows the individual responses of the woofer and midrange/tweeter section. Each trace is a combination of the farfield quasi-anechoic response above 500Hz or so and the nearfield lower-frequency response. The midrange and tweeter are both commendably flat in their passbands, though the tweeter does suffer from a big rise above 16kHz to a rather complicated-looking ultrasonic and therefore inaudible resonance. The woofer, too, looks pretty flat in its passband, rolling out gently below 60Hz to reach its –6dB point at a lowish 30Hz. Although this kind of nearfield measurement usually gives a curve that peaks slightly in the upper bass with a speaker that would measure flat in an anechoic chamber, the big Hales's nearfield trace is flat in this region. This confirms the designer's choice of a low-Q, perhaps overdamped sealed-box alignment. Although this does give the best time-domain performance, the danger, as Wes found, is that the speaker finds it hard to "give" in the bass. I was also bothered by this aspect of the Five's performance in my own auditioning.

Fig.3 Hales Concept Five, individual responses of woofer and midrange/tweeter at 50" on HF axis, corrected for microphone response, with nearfield woofer and midrange responses plotted below 600Hz and 800Hz, respectively.

The Concept Five's overall response on the tweeter axis, averaged across a 30 degrees horizontal window, is shown in fig.4. It is superbly flat, though I was surprised to see a small peak in the crossover region, revealed by fig.3 to be around 650Hz. This might throw the midrange forward in the soundstage slightly, making the region below it sound slightly lean/less warm. Though this can only be conjecture, I do note from fig.3 that while the woofer rolloff is fourth-order, 24dB/octave, as specified, the midrange rolls in with a third-order, 18dB/octave acoustic slope, which will make the crossover between the two units less than optimum.

Fig.4 Hales Concept Five, anechoic response on tweeter axis at 50", averaged across 30 degrees horizontal window and corrected for microphone response, with nearfield woofer response plotted below 300Hz.

Because of the speaker's mass, I was unable to measure its lateral off-axis response with my speaker turntable, which is limited to speakers weighing less than 150 lbs. The Concept Five, however, did appear to offer wide, even dispersion, correlating with its excellent imaging. Vertically, its response remained unchanged over quite a wide range, meaning that listening height will not be too critical.

In the time domain, the Hales's step response (fig.5) confirms its non–time-coherent nature: while all three drive-units are connected with positive acoustic polarity, the tweeter output arrives first, followed by the midrange, then the woofer. The sloping baffle of the Hales is thus only a matter of styling. The speaker's cumulative spectral-decay plot (fig.6) is superb. Other than the tweeter's ultrasonic resonance, the plot is almost completely free from delayed energy.—John Atkinson

Fig.5 Hales Concept Five, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.6 Hales Concept Five, cumulative spectral-decay plot at 50" (0.15ms risetime).