BenQ treVolo S - World’s Smallest Bluetooth Electrostatic Speaker

General Information

  • ELECTROSTATIC TECHNOLOGY: Hear all the details in your music with Electrostatic Speaker Technology
  • DUAL WOOFERS and DUAL AMPLIFIERS: Enjoy a rich and expressive bass performance with dual woofers and dual amplifiers
  • NON-DISTORTED 3D SOUND: Enhance your audio enjoyment with non-distorted 3D and duo modes
  • DUO MODE: Enjoy lifelike sound (Stereo Mode) or maximize your auditory experience (Party Mode)
  • CONVENIENT CONNECTIONS: Connect to devices conveniently with NFC + USB DAC/charging

Latest reviews


Reviewer for The Headphone List
ryanjsoo's Reviews
Pros: - Very detailed
- Balanced sound
- Long battery life
Cons: - Low maximum volume
- No life-proofing features
- Very directional treble
Introduction –

When thinking of BenQ, monitors, TV’s and household appliances probably spring to mind. When the company announced their first portable speaker, the very ambitious treVolo, it was quite a shock. The vast majority of portable Bluetooth speakers are uninspiring when it comes to sound quality. Most prioritise brash marketing and volume over quality and nuance, targeting beachgoers and park dwellers over discerning audiophiles. The newly updated treVolo S, however, sets out with a very different demographic in mind. Featuring stereo electrostatic tweeters, two full-range dynamic drivers and two passive radiators, the treVolo represents thoughtful engineering.

Electrostatic drivers, in particular, enable considerably lower distortion, superior imaging and greater resolution than any other driver type on the market; with electrostatic headphones from STAX and the highly renowned Sennheiser Orpheus representing the pinnacle of personal audio to many enthusiasts. This is unprecedented within the portable speaker market, remaining a rarity even on studio monitors, where electrostatic tweeters are limited mostly to very high-end products with price tags that eclipse the $200 treVolo S. Further reading on the speaker here.

Disclaimer –

I would like to thank Gines from BenQ very much for his quick communication and for providing me with the treVolo S for the purpose of review. All words are my own and there is no monetary incentive for a positive review. Despite receiving the speaker free of cost, I will attempt to be as objective as possible in my evaluation.

Accessories –


The treVolo S has a pleasing unboxing and accessory set. Sliding out the internal tray reveals the speaker, manuals and soft carrying pouch. It doesn’t provide much protection from shock but does effectively mitigate scratches.

Design –

The treVolo’s angular design forms a stark contrast to the cylindrical, fabric cloaked models from other manufacturers. Subjectively, it’s a nice looking speaker with a modern design that compliments a home setting. And combined with its lack of rugged or life-proofing features, it’s clear that this speaker was designed more as a portable indoor listening solution over the lifestyle “take it with you everywhere” kind. BenQ’s elegant typeface exudes an elegant aesthetic complemented by its clean silver/white colour scheme, a refreshing departure from flashier competitors.


The speaker’s exterior is mostly plastic with metal accents around the front-facing drivers. The driver enclosure and main structure of the speaker is metal to provide additional solidity, there’s no flex to the chassis at all. All surfaces have a nice speckled texture that increases perceived quality in the hand while adding some tactility and texture. Of note, I would suggest that the black model will hold up better in the long run as the white model is easily marked.


What’s perhaps most unique about this speaker is its fold-out electrostatic tweeters that provide additional stereo separation and a compact form factor when not in use. They’re covered by metal grills on either side to permit unimpeded sound output while protecting the delicate membranes inside. Though its tweeter construction is thin with moving parts, the treVolo S has held up brilliantly in my past 3 months of testing. The speaker has an angled rubber base that provides traction and prevents the speaker from wandering at high volumes. As treble tends to be most directional, it ensures the tweeters are directed closer to ear level.

Usability –


The main interfaces can be found at the rear of the speaker; a micro-usb charging port and 3.5mm input. Not only does the usb port accept power, it also enables the speakers internal DAC to interface directly with the source. At the top are the controls; power, pairing, volume up and down, play/pause and a dedicated eQ button. All are clicky though it does take some time to memorise the position of each function. Two status LEDs lie just anterior to the controls, offering battery and pairing status accordingly.


The speaker is easy to pair, with similar controls to most speakers. Once paired, connection was solid and range was among the best portable speakers I’ve tested. The speaker communicates via quick audio chimes that are less obtrusive than most. Implementing Bluetooth 4.2 enables the user to pair two speakers to provide a wider stereo image or simply a larger coverage of sound. This can be done through the BenQ Audio app that also enables users to toggle the 3D Mode eQ and monitor remaining battery.

On that note, the treVolo S excels with battery life. BenQ quote 18 hours, and though I wasn’t able to match that claim, I did get very close, consistently beating 16 hours of medium-max volume use before requiring a charge. That’s hugely impressive considering both my Envaya Mini and UE Boom barely scrape over 10 hours at similar volumes. BenQ don’t state the battery capacity, but I would assume it to be quite large as charge times are significantly longer than most. This isn’t as much of an issue as the treVolo S lasts as long on a partial charge as most competitors.

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.

Comparisons –

Denon Envaya Mini ($150): The Envaya Mini is my personal reference as it does everything a portable speaker should do and, for the most part, it does it well. The treVolo S does successfully provides a much more balanced, nuanced sound though it does so at a significantly higher price and within a larger, non-ruggedized form factor. Immediately, the Envaya Mini is more bass focussed, it extends a noticeably further, delivering more impact and slam. It has more mid-bass and considerably more upper-bass producing a much richer, warmer sound. However, it also lacks the control and separation of the treVolo S, sounding muddy and ill-defined by comparison. Still, it’s very full and engaging, better suiting larger spaces where low-frequencies tend to get drowned out.

As the treVolo has the more neutral bass response, its midrange is significantly more transparent. The Envaya Mini is darker and thicker, with poorly mastered albums it can sound muffled. It also has very recessed vocals relative to the treVolo S, though it has pleasing clarity that ensures voices are never drowned out. Still, the treVolo S excels with its midrange balance and linearity, midrange elements are more in focus and the treVolo’s sound has a lot more detail through this range. The treVolo has a more prominent lower-treble than the Envaya Mini, sounding crisper and clearer. However, it simultaneously sounds more detailed as it’s more linear and even from its upper-midrange; where the Envaya sounds more spiked due a more jarring transition from its recessed midrange.

The Envaya rolls off quickly after that initial crispness, it’s nicely detailed but provides little nuance beyond face value. The treVolo S on the other hand extends much further, even though these frequencies are more subdued to preserve a clean background. As such, the treVolo S produces a more layered presentation with greater micro-detail and noticeably more ambiance than the Denon. The Envaya Mini actually has some psycho-acoustic processing that lends the impression of a larger soundstage, though the treVolo S achieves a similar effect through more natural means; greater treble extension, superior separation and a wider stereo image.

UE Boom ($200): The UE Boom is not an especially great sounding speaker, but it has achieved huge popularity due to its effective 360 degree projection of sound, very high max volume and excellent battery life. The UE Boom has a pretty disappointing bass reproduction. It has little extension with a an upper-bass hump to compensate. The treVolo S extends further, delivering more punch and its more linear bass is more detailed and defined. The UE Boom has a pleasant midrange, it’s clear with an emphasis on upper midrange and articulation. The treVolo S doesn’t have the same sense of clarity, but it lacks the same upper-bass chestiness and sucked out lower-midrange. As such, it sounds a lot more natural if less vibrant.

The UE Boom is a little sibilant and lacks nuance, it’s a fairly superficial presentation, especially compared to the treVolo S and Envaya Mini. Both speakers have similar lower-treble quantity, making them crisper than neutral. That said, the UE Boom is sorely lacking detail. The UE Boom has no extension above its initial crispness while the treVolo S extends significantly further, delivering higher resolution and greater micro-detail retrieval. The treVolo has much more separation enabling the listener to discern layers and intricacies that the UE Boom glosses over entirely. Given its design, the UE Boom has zero stereo image, both speakers can be paired in stereo though the treVolo has the added advantage of providing some soundstage even on its own. This demonstrates that popularity isn’t always the best buy!

Edifier MP700 ($250): This isn’t a fair comparison as the MP700 is considerably larger than the treVolo S, but it’s also a very sophisticated speaker with a balanced tuning, and one that has a similar asking price to the BenQ. The MP700 provides a fuller, more extended bass response, which probably isn’t surprising as the speaker is significantly larger with 5 drivers dedicated to the low-end. It has significantly more depth and dynamics in addition to greater control and definition. The MP700 is actually tuned very similarly, slightly fuller in its mid-bass but not overdone and nicely balanced on a whole. Where the two speakers start to diverge is within their midrange.

The MP700 has more lower-midrange, producing a slightly fuller presentation where the treVolo S is slightly cooler. Neither is more neutral, they simply lie on the opposite sides of the tonal spectrum. The treVolo S is slightly more vocal forward where the MP700 has slightly laid-back vocals with a small upper-midrange bump. As such, both have pleasing but not overdone clarity, though the MP700 is a little more natural in its voicing as its treble is more neutral, where the treVolo S has more emphasis on articulation. Up top, the treVolo S is crisper where the MP700 is fairly neutral. In addition to being crisper, the treVolo S is actually slightly more detailed, showcasing the prowess of those electrostatic tweeters.

Both extend very well up top and produce cleaner backgrounds, though the treVolo S is slightly airier. The MP700 produces a slightly wider soundstage due to its physically larger dimensions though both resolve layers and smaller details that the majority of portable speakers don’t even glimpse. Of course, the MP700 has the ability to get much louder, and it does boast a more powerful sound as its size would suggest, but it’s still impressive to see how small the differences are besides bass.

Verdict –

As an audio enthusiast, I could fawn over the treVolo S’s sound all day. But in reality, the majority of portable speaker users will likely have more mixed use cases than myself. In this regard, the treVolo S falls short; treble is very directional, maximum volume is limited and its lack of life proofing makes it a questionable choice for some users. Because the treVolo S ironically represents bold underlying innovation within a market infatuated with the superficial. Where many are content with colourful lifestyle speakers with similarly coloured sounds, the treVolo S instead targets the discerning listener searching for greater balance and nuance.


It’s also a statement from BenQ; this isn’t a half-hearted throwaway, but a determined, fully realised effort to compete with the best. To my ear, they’ve achieved that feat. The treVolo S is balanced, natural and immensely detailed. It also does so without compromising form factor and excels with an extensive 18hr battery life. Utilising electrostatic tweeters, the speaker competes with much larger solutions in terms of resolution and detail and provides greater stereo separation. This costs the consumer, but its higher price is justified through BenQ’s effective implementation of technologies that provide genuine benefit to sonic performance. The treVolo S, therefore, suits those that prioritise sound quality, and to that end, it delivers with aplomb.



A slick looking, interesting gizmo for sure.
I'm a sucker for stuff like this though I'd really have no practical need for it.
Very informative review as always sir.