Audiovector R 8 Arreté loudspeaker Measurements

Sidebar 3: Measurements

As with the Magico A5 loudspeaker that Jim Austin reviewed in the July issue, I drove my test gear to his apartment to perform the measurements of this large, heavy speaker. I used DRA Labs' MLSSA system, an Earthworks microphone preamplifier, and a calibrated DPA 4006 microphone to measure the Audiovector R 8's behavior in the farfield. (We maneuvered one of the speakers onto a dolly and aimed it across a room diagonal so that it was maximally distant from the sidewalls.) I used an Earthworks QTC-40 mike for the nearfield and spatially averaged in-room responses. (For the latter, the loudspeakers were in the positions where JCA had auditioned them.)

The R 8's sensitivity is specified as 92.5dB/W/m. My estimate was slightly lower, 90dB(B)/2.83V/m, but this is still usefully higher than average. Audiovector specifies the R 8's impedance as 8 ohms. Using Dayton Audio's DATS V2 system, I found that the impedance magnitude (fig.1, solid trace) was less than 8 ohms across the audioband and remained below 4 ohms for almost the entire bass and midrange. I checked this measurement with the other R 8 sample; the impedance values were identical. The minimum magnitude was 2.52 ohms at 43Hz and 2.54 ohms at 250Hz. The electrical phase angle (dashed trace) is generally low. However, the EPDR (footnote 1) does drop below 2 ohms between 29Hz and 42Hz, with minimum values of 1.4 ohms at 36Hz and 1.63 ohms between 510Hz and 530Hz. The R 8's demand for current will be ameliorated by its high sensitivity, but it should be used with amplifiers that don't have problems driving 4 ohm loads.


Fig.1 Audiovector R 8, electrical impedance (solid) and phase (dashed) (2 ohms/vertical div.).

The traces in fig.1 are free from the small discontinuities that would imply resonances of some kind. When I investigated the enclosure's vibrational behavior with a plastic-tape accelerometer, I did find some resonant modes on the sidewalls and on the front baffle below the panel on which the forward-firing drive-units are mounted. The most significant mode lay at 375Hz (fig.2), with other, lower-level modes present at 336Hz, 508Hz, and 891Hz. However, all the modes are relatively low in level and have a high Q (Quality Factor), which will work against their having audible consequences.


Fig.2 Audiovector R 8, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of sidewall level with bottom woofer (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

With the R 8 supported on its spiked feet, its tweeter is 52.5" from the floor. This is well above the ear height of a typical seated listener, which a survey undertaken for Stereophile in the 1990s by Thomas J. Norton indicated averages 36". According to an email JCA received from Audiovector, the R 8's recommended listening axis is between 100cm and 110cm high (39.4"–43.3"). Accordingly, for the quasi-anechoic farfield measurements, I positioned the microphone level with the junction between the two upper woofers, which was 43" from the top of the dolly.

The black trace and the green trace above 400Hz in fig.3 show, respectively, the farfield responses of the tweeter and the lower-frequency drive-units on the recommended listening axis. The specified crossover frequency is 3kHz, but the tweeter rolls off sharply below 4kHz. Although the output of the lower-frequency drivers slopes down above 1.5kHz, there is significant energy up to 10kHz, with narrow peaks at 4.3kHz and 9.1kHz. The former peak is higher in level than the tweeter's output at the same frequency.


Fig.3 Audiovector R 8, acoustic crossover on listening axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the summed nearfield response of the woofers (green), the nearfield response of the internal isobaric woofers (red), the nearfield response of the middle port (blue), and the nearfield response of the bottom port (amber), respectively plotted below 420Hz, 300Hz, 400Hz, and 400Hz.

The green trace below 400Hz in fig.3 shows the summed nearfield output of the three midrange/woofers on the front baffle. (The top midrange/woofer's output extends into the treble; the middle woofer's output starts to roll off above 650Hz, the bottom woofer's above 300Hz.) While their nearfield output is relatively flat above what appears to be a high-pass corner frequency of 50Hz, the usual boost in the upper bass that occurs with nearfield measurements (footnote 2) is absent. Also absent is the notch at the port tuning frequency, which the low-frequency saddle in the impedance magnitude trace in fig.1 suggests is 43Hz. The blue trace in fig.3 shows the nearfield output of the second port from the bottom on the R 8's rear, which I was told loads the two lower woofers. (I have truncated this trace at 22Hz and 400Hz, as below and above those frequencies the measurement was contaminated with crosstalk.) This port doesn't extend the woofers' low-frequency response. However, Audiovector's R&D manager and founder, Ole Klifoth, mentioned in an email that they "try to avoid any compression build up. ... [T]he drivers become able to deal with more power with very low distortion."

The isobaric woofers fire downward into the R 8's vented base. Their output (fig.3, red trace; truncated below 30Hz and above 300Hz because of crosstalk) is specified as operating below 100Hz, which was confirmed by the measured nearfield response. This rolls off below 50Hz, no lower in frequency than the front-firing woofers. The amber trace in fig.3 shows the nearfield response of the bottom port on the R 8's rear panel, which reflex-loads the isobaric woofers. The port response peaks between 30Hz and 60Hz, extending the isobaric woofers' output. The port behind the top woofer is where a rear-firing midrange unit vents; I haven't shown it in this graph.

The black trace below 300Hz in fig.4 shows the complex sum of the nearfield responses, each weighted in the ratio of the square root of the radiating areas and compensating the acoustic phase for the differences in distance from a nominal farfield microphone position (footnote 3). It peaks in the region covered by the internal isobaric woofers; the rolloff below that region has an approximate slope of 18dB/octave. Above 300Hz in fig.4, the trace shows the R 8's farfield response, aver aged across a 30° horizontal window centered on the recommended axis. The balance is relatively even. The depression in the presence region may well have contributed to my estimate of the loudspeaker's sensitivity being slightly lower than the specification. The output between 100Hz and 450Hz is also a little lower than that between 500Hz and 1.6kHz.


Fig.4 Audiovector R 8, anechoic response on listening axis at 50", averaged across 30° horizontal window and corrected for microphone response, with the complex sum of the nearfield responses plotted below 300Hz.

Fig.5 shows the R 8's horizontal radiation pattern, normalized to the response on the recommended axis, which thus appears as a straight line. (The physical limitations of performing the measurements in JCA's room restricted the off-axis measurements to 45° to the sides rather than my usual 90°.) The loudspeaker's dispersion is relatively even, with apparent peaks and dips off-axis compensating for dips and peaks in the on-axis output. The tweeter starts to become directional in the top audio octave, as expected. Fig.6 shows the Audiovector's vertical dispersion, again normalized to the response on the recommended axis. Usefully, the response 5° below the recommended axis, which will be close to JCA's listening axis, is not dissimilar to the response on the recommended axis, though the depression in the mid-treble deepens a little. A large suckout develops at 3.55kHz more than 5° below that axis. The output in the tweeter's passband increases a little as you move above the recommended axis.


Fig.5 Audiovector R 8, lateral response family at 50", normalized to response on listening axis, from back to front: differences in response 45–5° off axis, reference response, differences in response 5–45° off axis.


Fig.6 Audiovector R 8, vertical response family at 50", normalized to response on listening axis, from back to front: differences in response 25–5° above axis, reference response, differences in response 5–10° below axis.

The red trace in fig.7 shows the Audiovector R 8s' 1/10 octave-smoothed, spatially averaged response in Jim Austin's room. (The spatial averaging (footnote 4) tends to average out the peaks and dips below 400Hz that are due to the room's resonant modes.) The blue trace shows the spatially averaged response of the Magico A5s taken under identical conditions, other than the presence of subsonic noise from JCA's building's heating/ventilation system, which could not be turned off on the morning that I performed the A5 measurements. The heating system was not operating when I measured the Audiovectors; the red trace in fig.7 therefore plots their output down to a lower frequency than the Magicos'. Because the loudspeakers have different sensitivities, I have normalized their outputs in the lower midrange and mid-treble in this graph.


Fig.7 Audiovector R 8, spatially averaged, 1/10-octave response in JCA's listening room (red) and of Magico A5 (blue).

Both pairs of speakers have an excess of midbass energy in-room, which I suspect will be due, at least in part, to the excitation of the low-frequency modes in JCA's room. Compared with the A5s, which have an impressively even balance at the listening position, the Audiovectors produce too much output in the upper midrange and slightly too little in the presence region. With an unflat response like this, whether the upper mids will be heard as exaggerated or the lower mids and treble will be heard as suppressed depends on the music being played.

I listened to one of my recordings on the R 8s—"In Paradisum" from the Portland State Chamber Choir's Translations album—and was impressed not only by the well-defined stereo imaging but also by the loudspeakers' excellent midrange articulation. This may well have been the result of the balance shown in fig.7.

The R 8s have a little higher output than the A5s in the top two audio octaves, but if you take as a reference the level at 1kHz, the in-room response slopes down in a generally smooth manner. A speaker that has a flat measured top-octave output in an in-room measurement will sound as if the highs are tilted up.

In the time domain, the R 8's step response on the recommended axis (fig.8) reveals that the tweeter and woofers are all connected in positive acoustic polarity. The decay of the tweeter's step smoothly blends with the positive-going start of the top woofer's step, but there is a second arrival, presumably from the middle woofer, 200µs later. The slight rise just before 6ms in this graph might be the output of the isobaric woofer—looking at its nearfield output revealed that it is also connected in positive acoustic polarity. Other than ridges of delayed energy at the frequencies of the treble peaks in the on-axis farfield response, the R 8's cumulative spectral-decay plot (fig.9) is relatively clean.


Fig.8 Audiovector R 8, step response on listening axis at 50" (5ms time window, 30kHz bandwidth).


Fig.9 Audiovector R 8, cumulative spectral-decay plot on listening axis at 50" (0.15ms risetime).

With its multiple drive-units, each covering a different passband but with significant overlap, the Audiovector R 8 is the most complex loudspeaker I have ever measured. Whether it is more complex than it need be can only be determined by listening, and for that I refer readers to JCA's auditioning comments.—John Atkinson

Footnote 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," JAES, Vol.42 No.9, September 1994, and

Footnote 2: A nearfield measurement assumes that the radiators are mounted in a true infinite baffle, ie, one that extends to infinity in both planes.

Footnote 3: See

Footnote 4: Using MLSSA to generate white noise, I averaged 20 1/10-octave–smoothed power spectra, individually taken for the left and right speakers in a rectangular grid 36" wide by 18" high and centered on the positions of Jim Austin's ears, which were 34" from the floor.

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MZKM's picture

It certainly looks amazing (not sure if $70,000 amazing), but I find it odd that the tonality can’t be more linear (doesn’t have to be flat, just smooth), but nice to see the wide directivity allowed by having multiple drive units of different sizes.

georgehifi's picture

"The R 8's demand for current will be ameliorated by its high sensitivity, but it should be used with amplifiers that don't have problems driving 4 ohm loads".

Looking at the fr and -phase epdr impedance across the bass, I think an amp that's not going to have any problems driving 2ohms is more the call, as many Class-D do 4 ok but into 2 many ????

Also looking at the spatially averaged room response, they look to be bass heavy and for a speaker this price I'd expect a flatter response, like the Sasha DAW
All the more reason with these to have an amp with dry vice like grip at 2ohms, any amp bloat will exaggerate that bass lift.

Cheers George

otaku's picture

That lead photo looks a lot better than it did in the magazine.

MauriceRon's picture

pink noise...?

hello ladieeeees

Lars Bo's picture

Thanks, Jim - very nice to read your positive review of a Klifoth speaker.

More than 30 years ago, my only second speaker on The Never Ending Hi-fi Journey was actually a kit by Ole Klifoth (satellite w/ bass module). The speakers provided years of much enjoyment.

To some extend I agree with your: "We like to say that's it about the music, but for me it's about the sound, too, equally. Music, after all, is made of sound. It is a distinction without a difference". I think most, if not all, audiophiles intensely enjoy the sheer "sound of sound". We react quite emotionally to certain drivers, be they spatial, micro dynamics, tone, klang, just to name a few. Or, indeed, as Herb, home recordings of Buddy Holly "being" in his NYC apartment. Or Art's "touch", perhaps similarly linked to a vivid humanness in sound. The aesthetics of sound is an intrinsic part of audiophile fascination, no?

But, generally and in hi-fi as well, I think music is distinctly different from "just" sound. Sound in itself is representational and of a concrete physical world; music is a sound-mediated, presentative art*. Like paintings are yet something other than their paint, and poetry more than its words, music is not reducible to sound (which, musically, is listened through). That doesn't mean the two phenomena are dichotomous; rather, in audiophelia, being about re-creating music (mostly) in our homes, they function hand-in-hand as the fidelity of real music play-back spans the two. Differentiation, though real, is somewhat of an abstraction. In practice, audiophelia pretty much seems to be about a hybrid fascination with the representativity of sound and alive music in authentic play. Perhaps, we all have our personal preferences of focus balances, but rarely, I believe, is intense enjoyment totally devoid of one or the other . Would e.g. (your, it seems to me, also partly musical "reading" of) the sound of tympani and the bass drum be equally emotional, if not skillfully played and conveyed in the context of a grand Mahler's 2nd?

On another topic in the September issue, in Letters, namely pitch of a record player, some additional comments/questions: The threshold for hearing a difference between two isolated pure tones is 1/20 of a semitone (semitone-frequences being ca. 6% apart (and 1,0595 ^12 = 2.0, i.e. an octave)). That translates to a critical pitch deviation of ca. 0.3%, or +/- 0.15%, no? Research shows that threshold is significantly lower for complex tones heard simultaneously, as in music. Along with e.g. in-press deviations, too (not to mention e.g. AAA recordings), vinyl is, on paper, not categorically free of possible audible pitch deviation. Even so, I think, we are many who hardly ever experience the slightest pitch-barrier for full musical and soundwise enjoyment on vinyl. Perhaps analog (heh) to rather high levels of measurable distortion in vinyl, well, simply not distorting.

As you state, people with perfect pitch can adjust to an overall off-pitch, say flat or sharp. But that is depending on music being in equal temperament; with older temperaments or some non-western temperaments this may not be so (as scale tone pitches vary within different fundamental, overall pitches). With equal temperament this is avoided. Then we have to live with a 5th harmonic being about three times greater (i.e. 0,83%) than the threshold for an off major third, a 7th harmonic six times more off a minor (or Mixolydian) 7th, not mentioning an 11th harmonic tritone. I imagine these patterns of off-pitched harmonics are also a part of JA's position on a specific profile of distortion being essential rather than merely raw levels?

Thanks again, Jim.

* As in Thomas Clifton's (Music as Heard): "Music is an ordered arrangement of sounds and silences whose meaning is presentative rather than denotative."

tonykaz's picture

Your PS Audio P10 is a power re-generating system, not a "power conditioner".

I suppose it's a small portion of your Associated Equipment grouping but it's a very large contributor to assured review confidence!

( In my opinion ) every reviewer of high resolution audio gear should have a reliable supply of clean power, shouldn't they ?

PS Audio is the only outfit offering gear like your P10.

Tony in Venice Florida

ps , the review loudspeaker veneer-wood is gorgeous but how do people keep them from scratches and damage? I had a pair of Meridian Loudspeakers in Rosewood that got scratched, ouch, too deep to repair. I also had a pair of Klipsch Corner Horns in Rosewood that were traded in with scratches, it's a pain that keeps on hurting to see and/or remember