Totem Acoustic Signature One loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Totem Acoustic Signature One's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. The Totem's specified sensitivity is 87dB/2.83V/m, which is the same as that of the earlier Model 1 Signature; my estimate, however, was much lower, at 83.5dB(B)/2.83V/m, which is 3dB lower than that of the 2008 speaker. Fig.1 shows how the impedance and electrical phase vary with frequency. The impedance is significantly higher than that of the Model 1 and Model 1 Signature. While those speakers had an impedance that dropped to 3.8 ohms between 200 and 300Hz, the new speaker drops below 8 ohms in only one region, with a minimum magnitude of 7.4 ohms at 200Hz. And while the phase angle is occasionally extreme, the magnitude at the same frequencies is high, mitigating any drive difficulty. The Signature One is an easy load for the partnering amplifier.

118TotS1fig1.jpg

Fig.1 Totem Signature One, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The traces in fig.1 have small discontinuities at 490 and 600Hz that suggest the presence of panel resonances at these frequencies. When I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I found a strong mode present at 600Hz on the sidewalls (fig.2), and a slightly weaker mode at 490Hz on the top panel. When I measured the Model 1 Signature in 2008, I found a strong vibrational mode at 675Hz on all surfaces, but felt it was sufficiently high in frequency not to have audible effects. On the earlier speaker I had also found two lower-level modes, at 290 and 320Hz, which I conjectured were connected with the lower-midrange warmth I'd occasionally noted with piano recordings; these modes are absent in the 2017 speaker.

118TotS1fig2.jpg

Fig.2 Totem Signature One, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

As in the earlier Model 1 variants, there were pipe resonances in the Signature One's rear-facing port. However, as can be seen by the blue trace in fig.4, which shows the Signature One's port output measured in the nearfield, the 2017 speaker's resonances are very much worse. Not only are there strong modes at the frequencies of the two panel resonances noted earlier, there is another strong mode at 700Hz. I heard these resonances as a vowel-like coloration as soon as I switched on the MLSSA noise signal, and once I'd identified it, it was as hard for me not to hear it in the music as it was for Herb Reichert when he thought he could hear the Totems' cabinets coloring the sound of Skip James's "She's All the World to Me." "A narrow band of noise or confusion somewhere in the middle of the midrange (500–600Hz)," Herb also wrote.

The port's legitimate output peaks narrowly between 30 and 50Hz, and the corresponding notch in the woofer's output (fig.3, red trace) lies at 39Hz, very slightly lower in frequency than that of the 2008 speaker. At the other end of the woofer's passband, its output rolls off rapidly above 3kHz, with the crossover to the tweeter (green trace) occurring at 3.5kHz. Like all metal-dome tweeters, the Totem's has a high, sharply defined resonant peak above the audioband, at 27kHz. This resonance should be sufficiently high in frequency to have no audible consequences. The traces in fig.4 compare the farfield responses of the 2017 Signature One (red trace) and 2008 1 Signature (blue). They are almost identical, though the earlier speaker's woofer alignment appears to be more highly damped.

118TotS1fig3.jpg

Fig.3 Totem Signature One, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield responses of woofer (red) and port (blue), respectively plotted in the ratios of the square roots of their radiating areas below 350Hz and 1kHz.

118TotS1fig4.jpg

Fig.4 Totem Signature One (red) and 1 Signature (blue), anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield woofer and port responses plotted below 300Hz.

The Signature One's horizontal dispersion (fig.5) is wide and even up to 6kHz, which correlates with stable, accurate stereo imaging. The radiation pattern narrows above that frequency, as is typical of a 1" metal-dome tweeter. In the vertical plane (fig.6), a sharply defined suckout develops in the crossover region immediately above the tweeter axis; a comparison of this graph and the red trace in fig.4 suggests that the most even treble response is to be heard just below the tweeter axis.

118TotS1fig5.jpg

Fig.5 Totem Signature One, 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.

118TotS1fig6.jpg

Fig.6 Totem Signature One, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 45–5° above axis, reference response, differences in response 5–45° below axis.

Turning to the time domain, the Totem's step response on the tweeter axis (fig.7) reveals that both drive-units are connected in positive acoustic polarity, with the tweeter leading the woofer. The decay of the tweeter's step blends smoothly with the start of the woofer's, suggesting optimal crossover design. Some slight undulations in the decay of the woofer's step can be seen; these correlate with the delayed energy at 3.3kHz in the cumulative spectral-decay plot (fig.8). Other than that, however, this plot is superbly clean, supporting HR's comment that the Signature Ones offered quickness, transparency, and flow.

118TotS1fig7.jpg

Fig.7 Totem Signature One, step response on tweeter axis at 50" (5ms time window, 30kHz bandwidth).

118TotS1fig8.jpg

Fig.8 Totem Signature One, cumulative spectral-decay plot on tweeter axis at 50" (0.15ms risetime).

Other than those cabinet and port resonances, Totem's Signature One measured better than its predecessors.—John Atkinson

COMPANY INFO
Totem Acoustic
9165 rue Champ D'Eau
Montreal, Quebec H1P 3M3
Canada
(514) 259-1062
ARTICLE CONTENTS

COMMENTS
dalethorn's picture

The LS3/5a's I bought circa 1975-1976, adjusted for inflation, come out to about the same price - mid-$2000's. But those Rogers speakers gave me anxiety, especially given that my loaner pair had a blown woofer. This new Totem reads like a bargain.

Ray in Michigan's picture

Try the Watkins Gen 4
Same tweeter but with a dampener that really makes the hi freq smooth
$1995 for the pair.Made in U.S.A
I have been running a pair for a month now and couldn't be happier

X