BenQ Trevolo S Bluetooth Electrostatic Speaker Review

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BenQ Trevolo S


Overall Design


Sound Quality






Battery Life



  • Good sound quality with low distortion and thumping bass.
  • Unique, foldable design that keeps it compact.
  • Battery life is decent.
  • Feels solid, heavy duty.
  • Dual woofers provide nice bass quality for its size.


  • Micro USB charging is a bit outdated. USB-C would have been more-ideal.
  • No official IPX rating - must take pre-caution to make sure it isn't exposed to rain or moisture.
  • Only available in one color scheme.
  • Could me more durable.

With all the options in the market today, it’s fair to wonder whether we’ve reached maximum Bluetooth speaker saturation. Manufacturers can choose many different angles to differentiate their products from the masses. Whether it’s a very small size, big sound production, extreme ruggedness, or water resistance, you can find a Bluetooth speaker to suit just about any specific scenario you might encounter.

One aspect that may not receive as much focus as you’d expect is the pure quality of the sound produced. Since Bluetooth speakers typically get used as portable devices of convenience, the focus often falls on aspects that enhance your ability to use them on the go. If you want to use a speaker outdoors at a beach party, for example, you’ll care much more about water resistance and speaker volume than you will about the fidelity of the cymbal crashes during a drum solo.

BenQ looks to shift the focus back to sound quality with their Trevolo S portable, electrostatic Bluetooth speaker. Electrostatic speakers, generally only found on high end equipment, have a reputation for producing high quality, accurate audio. However, we’ll need to investigate to find out if the advantages of this unique speaker design translate well to a portable device.

BenQ treVolo S

Electrostatic Versus Dynamic Speaker Design

Most people have familiarity with conventional, dynamic speakers. Even if you don’t understand the finer details, and even though some differences exist between models and brands, the basics remain the same. An electrical signal passes through a coil of wires surrounding a magnet. This creates a changing magnetic field which in turn forces the coil to rapidly move back and forth. Attached to the moving coil, a typically cone-shaped diaphragm moves as well, creating vibrations in the air also known as sound waves.

Regardless of size, this is how the vast majority of speakers work. Complex systems use more speakers of different sizes to better respond to high, mid, or low range frequencies of sound. Generally, producing louder sound requires larger speakers, particularly with lower bass frequencies.

Electrostatic speakers use a vastly different technology. Instead of cones moving the largest volume of air possible, electrostatic speakers are incredibly thin and flat. They typically consist of a sheet of plastic coated with some type of electrically conductive substance. This sheet resides between two conductive grids separated by an air gap on either side. The audio source gets converted to electrical signals and the two charged grids vibrate the thin membrane to produce sound.

Electrostatic Pros and Cons

With a fundamentally different design, electrostatic speakers have some definite advantages and disadvantages compared to traditional speakers.

First, depending on space constraints, it may prove advantageous to have a thin, flat speaker design over a thicker, deeper speaker box. Generally, electrostatics are chosen for accurate sound reproduction as they exhibit low distortion and musical transparency.

With dynamic designs, the weight of the speaker and design of the boxes can create resonances that cause inaccurate sound. With such light membranes, electrostatic speakers have a unique purity and accuracy to the sound they produce.

Unfortunately, it isn’t all positive for electrostatic speakers. The wide electric field and small air gap make them sensitive to humidity levels. Additionally, since the membrane doesn’t have a lot of room to move or the benefit of an enclosure, it can prove challenging to produce loud bass frequencies. Sophisticated manufacturers continue to find ways to compensate for this weakness, but it often is addressed by simply pairing the electrostatic speaker for mid to high frequencies with a traditional dynamic loudspeaker for lower frequencies. Electrostatics are also more susceptible to room dynamics and placement with a frequently smaller ideal zone for listening.

Finally, electrostatic speakers have a tendency to attract bugs, dust, particles, and moisture which can impact quality and longevity. Given these characteristics, let’s explore the treVolo S to see if we can unpack why BenQ chose this unique speaker design.

BenQ treVolo S

BenQ Trevolo S Overview

The Trevolo S is a vertical rectangular box. The front edge includes two round speaker grilles while two panels fold out from the side. This hybrid design places two woofers in the main box area of the speaker for lower frequencies while the folding flat panels house the electrostatic speakers for mid-range and higher frequency sounds.

This design immediately gives the Trevolo S a highly unique look that is sure to draw some attention. With two color options, black and silver and white, the Trevolo certainly captures a professional and refined look in different environments. While the unit feels relatively well-made, the unique design of the folding wings makes it seem a bit more delicate in nature. This certainly isn’t a rubberized, waterproof speaker you can toss in a bag without thinking about it.

BenQ treVolo S

The top of the unit has 6 buttons flush with the enclosure and an NFC connection option, while the rear has a micro USB port and 3.5-millimeter input jack. The USB port serves double duty. First, it charges the built-in battery which can deliver up to an impressive 18 hours of playback time. Also, BenQ went to the trouble of adding a USB digital to analog converter.

While Bluetooth may seem convenient, the limited transmission rate demands higher compression and therefore lower quality audio. If you don’t mind connecting with a cable, your mobile device can deliver higher quality source audio directly to the treVolo S by bypassing Bluetooth.

BenQ treVolo S

The Trevolo S is capable of entering “Duo Mode” which allows you to pair two units together. You can also select “Party Mode” which has each speaker producing both left and right channels or “Stereo Mode” in which one speaker produces only left and the other only right.

BenQ treVolo S


Before we cover the actual sound this speaker produces, it’s important to consider your experience using it. In our opinion, there are a few decent features outweighed by some glaring problems.

We appreciate things like NFC connection and the option to run via USB cable instead of Bluetooth. Also, 18 hours of playback time is quite respectable. Unfortunately, the limitations of electrostatic technology just simply don’t pair well with how we want to use a portable speaker.

BenQ treVolo S

As mentioned, while we wouldn’t say the Trevolo S has a low build quality, the wing design immediately makes it seem less durable. While not enormous, it certainly isn’t tiny. You could fit it into a bag or larger purse, but it definitely won’t slip into a pocket. Water resistance is out of the question, and beyond that, electrostatic speakers have more susceptibility to dust and humidity.

BenQ treVolo S

Operating the Trevolo S at home in a temperature, humidity, and low-dust environment worked without any problems. We were able to pair quickly using NFC and maintain solid connection throughout Bluetooth’s standard 30-foot range.

The BenQ app for Android and iOS was uneventful but functional, enabling us to monitor battery levels, set Duo mode, and adjust sound mode.

Though everything worked as expected in a controlled, indoor environment, we just wouldn’t have the confidence that this speaker would hold up well if we tried to take it out into the elements.

BenQ treVolo S

Audio Performance

Despite our concerns about using this as a portable speaker, we hoped that the amazing sound quality produced by the electrostatic speakers would more than make up for the lack of durability and versatility.

Unfortunately, we ended up with very mixed feelings.

First, we do need to say that, particularly with “3D Mode” enabled, the clarity and staging of some tracks was phenomenal for a small speaker. It handled vocals, classical, and acoustic guitar tracks exceptionally well. While BenQ isn’t especially clear about what 3-D mode entails, these tracks, particularly live recordings, brought on a very rich, clear, and immersive feel.

BenQ treVolo S

Our main complaints were not entirely unexpected with an electrostatic speaker. Overall volume was quite low, and bass in particular was very anemic. Even with the hybrid woofer design, the Trevolo S struggled to reproduce upright bass on jazz tracks and didn’t stand a chance against the booming bass from hip hop or dance samples.

Also, due to the directional nature of electrostatic technology, the sound didn’t seem to fill the room in the same way that other speakers would. Instead, while we had great clarity sitting directly in front of the Trevolo S, as we moved around the room the quality changed or diminished.

BenQ treVolo S

All in all, we’d consider this a good speaker for personal listening to particular types of music while sitting stationary in one location. We can’t really picture recommending the Trevolo S for a wide variety of outdoor scenarios or group settings.


Not every Bluetooth speaker needs to be the same. They don’t all have to be built like tanks to withstand the worst that nature or humans can throw at them. They don’t all have to pump out blisteringly loud, distorted music with thumping bass just because that’s what people at a pool party might want to hear.

BenQ treVolo S

We applaud BenQ for their boldness to do something different. The original Trevolo speaker was the first electrostatic Bluetooth speaker in existence and it doesn’t seem that any other manufacturers have been overly eager to follow in their footsteps.

In our opinion, the treVolo S seems to fall in the awkward middle ground where it doesn’t suit anyone’s needs exceptionally well. The unsophisticated listener isn’t discerning enough about audio quality to care. An outdoorsy, adventurous type of user might appreciate the sound quality but require a more durable unit. Anyone who likes hosting parties may not be able to get around the comparatively low volume. The ideal user profile gets narrowed down to audiophiles who appreciate quality music but want a portable speaker for listening to particular types of music either by themselves or with very small, quiet groups.

This level of specificity instantly rules out many users. This isn’t inherently bad. In fact, we love the fact that gadgets exist to cater to incredibly specific niche markets. This product diversity makes electronics fun and interesting instead of a procession of cloned products all designed to appeal to the masses.

While it can’t make many claims of versatility or durability, the Trevolo S furthers BenQ’s bold move to bring electrostatic speakers in a portable, Bluetooth package. As long as the Trevolo meets your needs, there’s really nothing else like it.

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