BenQ treVolo S Review – Electrostatic Bluetooth Speaker

Sound –

The treVolo-S was harder to evaluate than most portable speakers on account of its rather unique driver setup. Chiefly, its electrostatic tweeters are highly directional, with high frequencies quickly muting when listening off axis. As such, the treVolo-S performs best when placed at ear level, such as on a shelf, where high-frequencies are crisp, clear and nicely extended. Utilising two internal amplifiers, the treVolo S sounds clean with no audible hiss unless within a few centimetres of the drivers. Even in quiet environments, background noise is practically imperceptible.


I was also interested to find that the treVolo S is one of 3 treVolo speakers. It is one of two second-generation treVolo speakers that feature improved woofer drivers over the original. The S has the most mainstream appeal, an alternative to the treVolo 2 with a tuning more suitable for Pop music. It has a smaller design alongside smaller electrostatic tweeters combined with a greater focus on mid-bass and vocals. The treVolo S is the bassiest of the 3 and the only to support 3D Mode eQ.


Volume –
The treVolo-S does not get loud at all making it unsuitable for parties and larger listening spaces. It’s adequate for near field, even outdoors and has plenty of volume in small-medium sized room, but its maximum sound output is fairly limited compared to the competitors such as the UE Boom, Bose Soundlink Mini and Denon Envaya Mini. On a side note, I was happy to see some moderate volume compensation occurring, which retains a fuller bass response at lower volumes. Though it’s not quite as rich as the Envaya Mini, the treVolo S sounds balanced throughout its volume range making it one of the better choices for low volume listeners.


Tonality –

One would consider the treVolo S to have quite a vibrant sound given its driver configuration, but what BenQ provide is instead very balanced and quite mature. Coming from a lot of portable speakers, the treVolo S can seem mellow, even a little veiled, but in comparison to a reference earphone such as the UE18+ Pro, it’s immediately clear that this is not the case. Rather, the treVolo S has a considerably more linear tuning than essentially any portable speaker I’ve heard. It lacks the boosted bass of Bose and Denon speakers and the clarity of UE’s speakers, but its treble extends the furthest and its low-end is full and engaging if not ground shaking. It has suprising vocal presence and clarity without becoming over bright or thin. The result is a coherent compact sound system that offers some genuine nuance and a natural tone that can be listened to for hours on end. The speaker received over 100hrs of burn-in to ensure optimal performance during evaluation. Further break down will be with 3D Mode switched off.


3D Mode –

BenQ reps highly advised evaluating the speaker with this mode activated. Alongside a hearty volume boost, the eQ plumps up mid-bass, reduces lower midrange and elevates the upper-midrange/lower-treble to produce a punchier, clearer and slightly more V-shaped sound. Though I’m not usually a fan of eQ’s, it seems that the treVolo-S was tuned with this mode in mind, which effectively brings it more in line with other portable speakers. With 3D mode activated, the speaker remains fairly balanced but becomes more engaging in its delivery, especially at low volumes where bass tends to take more of a backseat. Besides signature changes, I was pleasantly surprised how natural the eQ mode was, with no strange echo or artificial soundstage processing. This is a very useable setting that provides more clarity and bass punch than the treVolo-S’ stock form. I’m sure a lot will prefer this mode though those prioritising a linear midrange will want to leave it off.


Wired –

Though designed to be used as a wireless speaker over a Bluetooth connection (and I will evaluate it as such), I wouldn’t be doing the speaker justice if I didn’t test its maximum potential through a wired connection. To test this out, I employed the iBasso DX200 ($900) loaded with lossless files. 3D Mode works regardless of the source. The differences weren’t enormous. a positive in my book is as it suggests no artificial processing is being applied, ensuring as much fidelity as possible. Unfortunately, that also means the speaker’s deficiencies aren’t appended; bass extension for instance, didn’t improve. The largest differences to my ears resided within the higher frequencies. Through a wired connection, the treVolo S was noticeably more detailed and dynamics were improved. Otherwise, users shouldn’t feel that the wireless circuitry is holding the speaker back too much.


Bass –

Despite BenQ stating a frequency response that extends down to 60HZ, bass roll-off is very apparent and sub-bass is essentially non-existent. This is likely a limitation of the speaker’s size as no portable speaker I’ve tested reproduces any meaningful sub-bass. On the flipside, the treVolo’s well-realised mid-bass response already puts it ahead of most portable speakers in terms of bass extension. Exemplary speakers such as the Denon Envaya Mini and Bose Soundlink Mini II still hold a noticeable advantage in this regard but bass remains punchy with slight elevation contributing towards full but not muddy or bloated bass notes.

The treVolo-S’ reasonably well extended, mid-bass focussed low-end also permits a cleaner upper-bass that integrates smoothly into its midrange. This is a common issue with Bluetooth speakers that lack the ability to reproduce mid-bass such as the UE Boom, that instead resort to upper-bass emphasis. While an upper-bass boost does result in a fuller sound, lows become tubby and the midrange thick and muffled. The treVolo S is considerably more balanced, its bass contains more detail and its midrange is more transparent as a result. It may sound flat and a little uninspiring coming from the aforementioned Denon and Bose speakers, both of which possessing hearty emphasis, though the treVolo S is easily the tightest, most balanced and defined among them.


Mids –

Though not perfectly even compared to a $2000 set of in-ears, relative to other portable speakers, the treVolo S is very well done; demonstrating refinement in its delivery of vocals without pushing instruments too far into the background. Where most portable speakers pursue either a warm/lush or bright/clear midrange presentation, the treVolo S is fairly linear and well-articulated. It’s a little vocal-forward in its delivery on behalf of an emphasized centre midrange, but the speaker sounds both refined and focussed due to some well-considered sculpting. Chiefly, though its bass is full, no spill is apparent due to slight attenuation of the lower-midrange that saps some body but heightens bass/midrange separation.


It’s a slight adjustment that doesn’t skew timbre too significantly or produce any dissonance, rather, its midrange becomes just slightly cool in tone. This is counteracted by a slightly subdued upper midrange that produces a smooth, dense and grounded expression, effectively preventing an overly forward or fatiguing presentation. This is aided by a well-judged lower-treble that provides accurate articulation and avoids emphasizing sibilance entirely. I was also surprised to find the treVolo S resolving some background details, providing some nice layering to its presentation. Though vocals always remain centred due to its mono full-range driver configuration, the stereo electrostatic tweeters do provide a decent stereo image, certainly wider than most, in addition to well-resolved directional cues.


Highs –

Crisp, detailed and extended, the treVolo S is quite an oddity amongst competition that barely extends into the higher frequencies at all. When placed at ear level, the speaker provides a slightly crisper lower-treble that brings details to the fore in addition to excellent detail retrieval that’s easily the highest I’ve heard from a portable speaker. As its middle treble is slightly subdued, it lacks pristine clarity and air, contributing towards a smoother presentation with a clean background. Upper treble extends nicely with hints of sparkle at the very top that is not present on competing solutions. Since the treVolo S has a more subdued upper midrange, treble instrumentation can sound thin and the speaker does have slight metallic tinge, though the tasteful nature of its emphasis prevents highs from becoming piercing or harsh.

In the same vein, the treVolo S completely avoids sounding peaky or strident within its higher frequencies due to its wide band emphasis and clean background. This is topped off with very pleasing resolution that contributes to the speaker’s detail retrieval and grants each note with greater clarity without resorting to excessive emphasis. Though not as pristine as speakers like the Envaya Mini, the treVolo S is easily the most detailed and natural (despite its thinness), with superior extension and higher resolution. I haven’t heard such nuance from a portable speaker though, for the sake of complete transparency, competitors don’t set the bar very high. Still, the treVolo S is detailed enough to compete with lower-end desktop speakers though its form factor makes it a lot more directional and high frequencies fall off fairly quickly with distance.

Next Page: Comparisons & Verdict 



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Ryan Soo

Avid writer, passionate photographer and sleep-deprived medical student, Ryan has an ongoing desire to bring quality products to the regular reader.


2 Responses

  1. There are two modes for pairing two speakers configurable through the app. Party mode is duplicate, with both speakers playing both left and right. Duo mode is stereo with one speaker dedicated to each channel.

  2. Would the duo mode be like left and right channel’s or would they just be duplicates?

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