Hales Design Group Transcendence Five loudspeaker Measurements

Sidebar 2: Measurements

The Hales' sensitivity was only moderate, at an estimated 85dB(B)/2.83V/m. However, its impedance plot (fig.1) indicates it to be a demanding load, especially in the middle of the midrange. There the magnitude dips below 2 ohms between 440Hz and 680Hz, and the phase angle is also extreme—it reaches –49º at 385Hz, a frequency where the magnitude is only 3.5 ohms. I'm not surprised that RD found he needed the beefy Bryston amplifier to drive these speakers.

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

Note the small wrinkle in the impedance traces around 170Hz in fig.1. This is due to a relatively mild cabinet resonance—as can be seen in fig.2, a waterfall plot calculated from the output of a simple plastic-tape accelerometer fastened to one of the Five's side-panels, 12" from the base. This mode was present at a low level on the front baffle but was much stronger on the speaker's rear panel, and is joined by a strong mode at 150Hz. The fact that this panel faces away from the listener will work against its audibility.

Fig.2 Hales Transcendence Five, cumulative spectral-decay plot of accelerometer output fastened to side wall 12" from base. (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz.)

The woofer crosses over at around 400Hz to the midrange, which in turn hands over to the tweeter at around 3kHz. The Transcendence Five's overall response, averaged across a 30º horizontal window on the tweeter axis and spliced to the nearfield woofer response, is shown in fig.3. It is impressively flat in the midrange and treble. A very slight swayback can be seen in the presence region, but, all things being equal, this should not be heard as a lack of impact. RD did note the "air" in the T5's character compared with the Dunlavy, and this might be associated with the slight boost in the high treble (though the speaker's HF dispersion will also contribute to this perception). The ultrasonic tweeter resonance is very high in level, but this should not be a factor in bandwidth-limited CD playback. But play LPs with an MC cartridge having a resonance in the same region as the T5's tweeter peak and you might notice some intermodulation.

Fig.3 Hales Transcendence Five, anechoic response on tweeter axis at 50", averaged across 30º horizontal window and corrected for microphone response, with the nearfield woofer response plotted below 300Hz.

The T5's low-frequency behavior seemed to be a perfectly competent sealed-box alignment tuned to 29Hz, exactly as specified—29Hz is therefore the –6dB point compared with the level at 100Hz. There seems no reason, therefore, for the problem RD had with the bass quality. It could well be that the new attic trapdoor in his listening room is a factor, but at low frequencies, most things short of solid masonry are equally transparent. In this respect, a wooden trapdoor is not going to be too different from the original Sheetrock.

The speaker's horizontal dispersion is shown in fig.4, with the off-axis curves normalized to the on-axis response. The cursor shows a slight flare at the bottom of the tweeter's passband, which will compensate for the slight on-axis depression in this region. Otherwise, the off-axis radiation is well controlled, indicating well-defined, stable stereo imaging. Vertically (fig.5), the use of fourth-order crossover filters results in very little change in the speaker's balance with height. Only a standing listener will notice a suckout at the upper crossover frequency. The tweeter axis is an optimal 35" from the floor, pretty much the average height of a seated person's ears.

Fig.4 Hales Transcendence Five, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90º–5º off-axis, reference response, differences in response 5º–90º off-axis.

Fig.5 Hales Transcendence Five, vertical response family at 50", from back to front: differences in response 10º–5º above HF axis, reference response, differences in response 5º–10º below HF axis.

The Transcendence Five's impulse response (fig.6) is typical of a speaker using high-order crossover filters and is overlaid by the ringing of the tweeter. The step response (fig.7) indicates that the tweeter, midrange unit, and woofer are all connected with the correct positive acoustic polarity, but that the speaker is not time-coherent.

Fig.6 Hales Transcendence Five, impulse response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.7 Hales Transcendence Five, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Finally, the Five's cumulative spectral-decay or waterfall plot (fig.8) is superbly free from resonance-induced ridges—other than the tweeter's ultrasonic mode, of course. Overall, this superb measured performance indicates excellent engineering.—John Atkinson

Fig.8 Hales Transcendence Five, cumulative spectral-decay plot at 50" (0.15ms risetime).

Hales Design Group
16812 Gothard Street
Huntington Beach, CA 92647