Volti Audio Rival loudspeaker Measurements

Sidebar 3: Measurements

I used DRA Labs' MLSSA system and a calibrated DPA 4006 microphone to measure the Volti Rival's frequency response in the farfield, and an Earthworks QTC-40 for the nearfield responses. (I measured Rival serial no.001.) Before carrying out any measurements, which were performed without the grille, I ensured that all the crossover resistor and capacitor choices on the rear panel were set as recommended in the manual.

The Volti's voltage sensitivity is specified as an unbelievable 100dB/W/m; ie, the Rival will play as loudly when fed 1W as a tiny LS3/5a would when fed 60W (assuming the LS3/5a didn't melt). Nevertheless, my estimate of the Volti's B-weighted voltage sensitivity was close to the specification at 98.2dB/2.83V/m. This is indeed a loud speaker—one of the highest-sensitivity loudspeakers I've measured!

The Rival's plot of impedance magnitude and electrical phase angle against frequency (fig.1) reveals that, other than a dip to 3.26 ohms at 110Hz and a combination of 5 ohms and –50° phase angle at 83Hz, the speaker should be relatively easy to drive. However, a sharply defined discontinuity at 168Hz in both the magnitude and phase traces, and a smaller wrinkle at 320Hz, suggest that cabinet resonances of some kind are present at these frequencies. Testing the behavior of the enclosure's panels with a plastic-tape accelerometer, I found strong resonances at both frequencies at various places, especially on the top panel (fig.2). I would have expected these resonant modes to add congestion and coloration in the lower midrange, but I note that Ken Micallef didn't mention hearing any problems in this region, perhaps due to the Rival's very high sensitivity. (I measure cabinet resonances with a standardized drive voltage, not a standardized sound pressure level.)


Fig.1 Volti Rival, electrical impedance (solid) and phase (dashed) (5 ohms/vertical div.).


Fig.2 Volti Rival, cumulative spectral-decay plot calculated from output of accelerometer fastened to center of top panel (MLS driving voltage to speaker, 7.55V; measurement bandwidth, 2kHz).

The impedance-magnitude trace (fig.1, solid trace) suggests that the Rival's port resonance is set at 32Hz, and its woofer's output, measured in the nearfield (fig.3, blue trace), indeed has a minimum-motion notch at that frequency (at which the back pressure from the port resonance holds the woofer cone motionless). The port's output (red trace) does peak at 32Hz, but extends higher in frequency than is usually the case, and has strong resonances present at 168 and 320Hz—the frequencies of the discontinuities in the impedance graph—and another at 500Hz. The lower two modes are strong enough to measurably affect the woofer's nearfield response. The woofer itself rolls off rapidly above 450Hz, and its farfield output appears to be set 3–5dB too high in level compared with that of the horn-loaded midrange drive-unit (green trace). The output of the midrange driver rises steadily to the 6kHz crossover point to the horn-loaded tweeter, which then appears to be set too high in level for strict neutrality. (Again, the measurements were performed with the factory-recommended crossover settings.) I suspect that this elevated treble was behind KM's finding the speaker unforgiving of every "pop, tick, and surface-noise goblin on less-than-perfect LPs."


Fig.3 Volti Rival, acoustic crossover on tweeter axis at 50", corrected for microphone response, with nearfield responses of midrange drive-unit (green), woofers (blue), and port (red) respectively plotted in the ratios of the square roots of their radiating areas, below 550, 350, and 800Hz.

In fig.4, the trace below 300Hz shows the complex sum of the nearfield midrange, woofer, and port responses. While some of the huge peak in the upper bass will be an artifact of the nearfield measurement technique, the Volti's woofer is balanced too high in level to sound natural. Again, this graph indicates that the farfield midrange response is balanced too low in level compared with the bass and treble regions. Predicting the subjective character of this kind of measured response is difficult, as which region the listener takes as a reference will be related to the music played. KM commented that the Rival's bass was "riveting, powerful, and forceful, and as full of tone, texture, and energy, as I've ever heard," and that the high frequencies were "smooth, wide open, and grain-free." I suspect, therefore, that he was referencing his auditioning comments to the bass and treble levels, which is probably why he felt he needed to change the crossover settings from the factory-recommended values.


Fig.4 Volti Rival, anechoic response on tweeter axis at 50", averaged across 30° horizontal window and corrected for microphone response, with complex sum of nearfield responses plotted below 300Hz (black).

The plot of the Rival's lateral dispersion (fig.5) reveals that the sharply defined suckouts in the mid-treble fill in to the speaker's sides and that the radiation pattern is even, though narrow above 1kHz. In large or well-damped rooms, this will work against the excess top-octave energy on the tweeter axis. In the vertical plane (fig.6), the traces are normalized to the response on the tweeter axis, which is 38" from the floor. Again, the treble suckouts fill in above and below this axis, though more than 5° below the tweeter, a suckout appears in the crossover region between the woofer and midrange.


Fig.5 Volti Rival, 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.6 Volti Rival, vertical response family at 50", normalized to response on tweeter axis, from back to front: differences in response 15–5° above axis, reference response, difference in response 5–10° below axis.

The step response on the tweeter axis (fig.7) indicates that all three drive-units are connected in positive acoustic polarity, although, as is usually the case with a horn-loaded speaker with a flat baffle, the output is not time-coincident. The output of the midrange unit arrives at the microphone 0.55 millisecond behind that of the woofer and 0.75ms behind that of the tweeter. The cumulative spectral-decay plot on the same axis (fig.8) is disturbed by ridges of delayed energy at the lower crossover frequency and at 3.3kHz, but is actually cleaner than I expected.


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


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

Summing up the Volti Rival's measured performance is difficult: Its perceived balance will depend to a greater degree than usual on the listener's choice of music and the size and acoustics of the room. Against those reservations must be balanced the speaker's extraordinarily high sensitivity. I hate it when an audio writer says, "Listen for yourself"—but in the case of the Rival, that's all I can say.—John Atkinson

Volti Audio
6100 Nashville Highway
Baxter, TN 38544
(207) 314-1937

mvs4000's picture

Upon further reflection, post deleted by author.

es347's picture

..indeed. $3500 for different finishes is bad enough...$500 for grill cloths?

jonathan.fisk's picture

Superb sound, cabinet questions, numbers and pictures that don't add up...just like the sensitive, squat, celebrated DeVore Orangutan series. Or the O/96 at least, as Stereophile did not publish measurements with their latest O/93 coverage --an odd omission for a perennial Stereophile "Speaker of the Year." I hope Stereophile will conduct additional listening tests of the Volti Rival, as they've done with both Orangutan models. A relevant and reasonable expectation, given the similar storyline and respectfully recognizing DeVore and Volti are competing for the same ears and $$$.

blacktruffle's picture

Hi Ken,
great review, thank you!
I didn't understand completely the final setup of loudspeakers.
Could you explain a little more?
Best regards!

ken mac's picture

BlackTruffle, I thought the setup description was rather graphic:" After some trial and error, I lessened their degree of toe-in from 45° to where I could just see each inner side panel. In short, the Rivals ended up 66" from my listening chair, with the centers of their panels 32" from the front wall—a few inches back from the DeVores' positions."
Greg took a crack at setup, then I followed up, the results above. Trial and error....Thanks for your comment.

Anton's picture


1) "...once you hear horns, you never go back."

Now that you've gone horn, can you go back?

2) Did the speakers ever descend Mt. Micallef?

3) Did seeing JA's results change your interpretation of things you heard?

(The review, overall, made me want those speakers.)

4) In JA's Figure 4, the frequency response curve looks alot like those old "equalizer settings" I'd run into in people's car stereo set ups in the late 70's and early 80's. The "smiley face pattern!"

5) I would love to see on of JA's frequency response graphs in room like he does with some other speakers.

6) Is near field a problematic way to 'measure' horn speaker performance, in particular? I've always thought of multi-way horns as needing alot of 'intergration distance.'

ken mac's picture

2. The Rivals did descend and depart. 3. I see the results of JA's tests same time as everyone else: when I receive the issue, not before. Thank you.

Tesla one's picture

It's nice to see another of Volti Audio's speakers well reviewed (like the all-horn Vittora model before it, by Mr. Dudley), especially being they're a different type of speaker than the ones usually chosen for review by Stereophile; namely large radiation area, high sensitivity speakers that are (at least partially) horn-driven. Mr. Roberts (among others) is to be commended for his effort to make available this "genre" of speakers to a broader range of costumers for what appears to be very fair prices. Whether a sign of maturation of horn speakers in general or a more deliberate, careful voicing his speakers seem to appeal widely with less focus on any particular horn-sound imprinting and more on their unconstricted, musical nature.

Regarding the review in question of the model Rival there's no questioning the positive, even ecstatic nature of it, but sadly I find it's more about an elated state of mind than any descriptive, cool-headed exposition. Any speaker has something distinctive sounding about it, even though one might find it to possess no immediate "house sound," and trying to come about this is essential in getting a grasp of what we're dealing with. It's not that Mr. Micallef's review is devoid of description, but that I find it to lack a contrasting ground to be viewed against - be it in comparison to other speakers than the DeVore's, or a more firm, dispassioned approach to the core DNA of what makes these speakers sonically tick.

I'm not bashing Mr. Micallef for a very positive review, that's not my intention, but merely want to express that I walk away from it less keen about a product's sonic specifics and more aware of someone's exaltation.

ken mac's picture

Tesla, I am sorry my review didn't meet your needs. I can only compare products under review to what I have in house--my DeVore O/93s, and I did!

markotto's picture

Reticle I would like to have the chance to listen to them,however here on Vancouver Island that won't happen. I can't comment on the "sound", but based on the pictures they look quite ummm...... Ugly. Owners please don't freak,just my opinion. I happen to own probably the ugliest looking speakers ever,Infinity Reference Standard 2.5. I enjoy them still. Maybe we need an an article about the "least attractive "speakers we have ever owned. Should be entertaining. Oh..."recticle" ....stupid spellcheck!!

johnny p.'s picture

This speaker joins the Tellig-reviewed La Scala and Emerald Physics's models which violate (2) of John Atkinson's rules of horns:

(1) They need to be 5-way
(2) Due to this, they will be very expensive

(in his Auditorium 23 review, last year).

Joshnich's picture

I happen to own a pair - In fact I am pretty sure mine are the natural birch ones shown in the article. And I think your review is spot on. The realism and dynamics delivered by these speakers cannot be denied. If you don't like your music to sound live then these are not for you.
Greg has done a remarkable job. These speakers can fill the room with music you can feel and they can also deliver incredible detail and magic at lower listening levels. Thank you Ken Mac for the honest and detailed review!

Volti's picture

Regarding the cost of "upgrades" - There is such a thing as honest ignorance. People simply do not know the costs involved with doing the type of work that I do. As a society, we've become so used to $59 microwave ovens at Wal-Mart that we no longer know how to place value on designing and hand-building a complex product like the Volti Audio Rival.

Perhaps a better way to think of the "upgrades" is to think of them as deductions instead. The Rivals, with veneer and grills at $11,900 represent good value in the marketplace. I'm offering the option of ordering them without veneer and grills to help those who are on a tighter budget get the Volti Audio sound into their systems. Isn't that an option you'd like to see available from other manufacturers?

Greg Roberts

Joshnich's picture

Good Point Greg! That is exactly the way I looked at when purchasing these fantastic speakers. In today's market, seeing what other speaker manufacturers are charging, the Rivals at 12K represent an incredible value.


Cosaxi's picture

Visit the Volti website. Can't help but think of Klipsch. Would be interesting to compare the Cornerhorn or the LaScala side by side with the Vittora.

Nagrapex's picture

I also have a strong preference for high-efficiency designs because of their great dynamics and freedom from strain. However, these clearly need more crossover design work. That top end emphasis might create the impression of clarity, but it would be fatiguing. Voices would sound a bit thin, and the upper bass likely boomy. I wonder if the designer is measuring them.

MikeP's picture

Some of the very best speakers ever made period !!

New Stage Accompany Master M57 or M59 with bamboo cabinets..

Stereophile will never review them though...