MEASUREMENTS

Iused DRA Labs’ MLSSA system, a calibrated DPA 4006 microphone, and an Earthworks microphone preamplifier to measure the TAD Grand Evolution 1’s quasi-anechoic frequency- and timedomain behavior in the farfield. I used an Earthworks QTC-40 microphone, which has a small, 1/4" diameter capsule, for the nearfield responses. I examined the loudspeaker’s impedance with Dayton Audio’s DATS V2 system.

My B-weighted estimate of the GE1’s voltage sensitivity was 87.5dB(B)/2.83V/m, which is within experimental error of the specified 88dB/2.83V/m. TAD specifies the GE1’s impedance as 4 ohms. The impedance magnitude (fig.1, solid trace) was close to 4 ohms in the upper bass and midrange, rising above 8 ohms for most of the treble. The minimum value is 3.84 ohms at 70Hz. However, the electrical phase angle (fig.1, dotted trace) is occasionally high, which means that the effective resistance, or EPDR,1 is significantly lower. The EPDR lies below 3 ohms below 30Hz, between 43Hz and 95Hz, between 197Hz and 1183Hz, and above 7kHz. The minimum EPDR values are 1.6 ohms at 27Hz, 1.76 ohms at 56Hz, and 2 ohms at 608Hz. The GE1 is a very demanding load for the partnering amplifier.

The impedance traces are free from the small discontinuities that imply the presence of cabinet resonant modes, and the enclosure’s panels seemed inert when I rapped them with my knuckles. The only resonances I found with a plastic-tape accelerometer lay at 293Hz on the sidewalls level with the lower woofer (fig.2) and 379Hz on the top panel and on the front baffle below the woofers. As these modes are both extremely low in level and have a high Q (Quality Factor), I can safely predict that they won’t have audible consequences.

The two woofers behaved identically, and the sum of their nearfield responses (fig.3, blue trace) has the expected minimum-motion notch at 32Hz, which implies extended low frequencies. The downwardfiring port’s nearfield output (fig.3, red trace) peaks slightly below the tuning frequency and, other than slight lowlevel discontinuities at 150Hz and 300Hz, its upper-frequency rollout is clean. The output of the woofers crosses over to that of the midrange unit (fig.3, green trace) close to the specified 250Hz. There is little

sign of the usual nearfield low-frequency boost in the complex sum of the midrange, woofer, and port responses (fig.3, black trace below 300Hz). This suggests that while the TAD GE1’s low-frequency alignment offers excellent extension, it is optimized for articulation rather than maximum bass weight.

The black trace above 300Hz in fig.3 shows the GE1’s quasi-anechoic farfield response, averaged across a 30° horizontal window centered on the tweeter axis. Other than a slightly elevated midrange and a slight lack of energy in the presence region, the balance is even. The small peaks and dips between 6kHz and 20kHz are likely due to interference between the output of the coaxially mounted tweeter and the reflections of that output from the midrange cone’s surround. The tweeter’s response also rises above the audioband, with a peak just below 29kHz. The GE1’s behavior in the treble is very similar to that of the TAD CE1TX standmount that HR reviewed in June 2023,2 which also used a coaxial high-frequency/midrange unit.

The TAD’s horizontal dispersion, normalized to the response on the central tweeter

axis, which therefore appears as a straight line, is shown in fig.4. The dispersion is well-controlled up to 6kHz, and above that frequency, the peaks and dips in the on-axis response tend to even out. Both factors correlate with stable, accurate stereo imaging.

With the speaker sitting on its coneshaped feet, the GE1’s tweeter is 39" from the floor, which is a little higher than the average height of seated listeners. (A survey performed by Thomas J. Norton for

Stereophile in the 1990s found this height to be 36".) The dispersion in the vertical plane, again normalized to the response on the tweeter axis (fig.5), shows that the frequency response is maintained up to

15° above and below the tweeter axis.

In the time domain, the GE1’s step response (fig.6) indicates that all the drive units are connected in positive acoustic polarity. The decay of each unit’s step blends smoothly with the start of the next driver’s step, which implies optimal crossover topology. The GE1’s cumulative spectral-decay plot on the tweeter axis (fig.7) features a clean initial decay with a ridge of delayed energy at 9144Hz, indicated by the cursor position in this graph. This is the frequency of a small peak in the speaker’s on-axis response, again very similar behavior to that of the TAD CE1TX.

Putting to one side that demanding impedance, the TAD Grand Evolution 1-WN offers excellent measured performance. —John Atkinson

1 EPDR is the resistive load that gives rise to the same peak dissipation in an amplifier’s output devices as the loudspeaker. See “Audio Power Amplifiers for Loudspeaker Loads,” Vol.42 No.9, September 1994, and stereophile.com/reference/707heavy/ index.html. Stereophile TAD GE1 Impedance (ohms) & Phase (deg) vs Frequency (Hz) Fig.1 TAD Grand Evolution 1, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

2 See fig.3 at stereophile.com/content/tad-ce1txloudspeaker-measurements. Fig.4 TAD Grand Evolution 1, lateral response family at 50", normalized to response on tweeter axis, from back to front: differences in response 90°–5° off axis, reference response, differences in response 5°–90° off axis.

Fig.3 TAD Grand Evolution 1, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the nearfield responses of the midrange unit (green), woofers (blue), and port (red), and their complex sum (black), respectively plotted below 340Hz, 700Hz, 420Hz, and 300Hz.

Fig.2 TAD Grand Evolution 1, cumulative spectraldecay plot calculated from output of accelerometer fastened to side panel level with the lower woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

Fig.5 TAD Grand Evolution 1, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15°–5° above axis, reference response, differences in response 5°–15° below axis.

Fig.6 TAD Grand Evolution 1, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

Fig.7 TAD Grand Evolution 1, cumulative spectraldecay plot on tweeter axis at 50" (0.15ms risetime).