Rel Acoustics T-Zero: the best small subwoofer to boost your compact speakers?

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The REL Acoustics T-Zero subwoofer is the smallest model in the Welsh manufacturer’s range, but also one of the most compact on the market. Its dimensions make it an ideal choice for integration in a small room or for those who are looking for a discreet subwoofer.

The Rel Acoustics T-Zero subwoofer is visually discreet and can easily fit into a small room.

The REL subwoofer features a 6.5” long-throw driver loaded in a reinforced anti-vibration cabinet. This downward-firing driver guarantees omnidirectional sound wave distribution, which makes it easier to position the subwoofer in the room. The driver is powered by a 100 watt RMS class D amplifier.

Sold for €575, the RELAcoustics T-Zero subwoofer seems to be the perfect solution to extend the bass response of a pair of bookshelf speakers, in particular more compact models equipped with drivers measuring from 4 to 5 inches.

Despite its compact size and modest power, can the Rel Acoustics T-Zero subwoofer change the listening experience in a 2.1 configuration?

Rel Acoustics T-Zero: the brand

The Rel Acoustics company is based in Bridgend in Wales and was founded by Richard Edmund Lord in 1990. One of the keys to the success of Rel Acoustics subwoofers over competing models is the systematic use of a high level connection with the amplifier (except for the few Rel Acoustics subwoofers designed specifically for home theater). It is powered by the signal from the final output stage of the amplifier, the same one that drives the speakers, which ensures a very consistent overall sound signature and allows the subwoofer to be connected to any amplifier.

Rel Acoustics has used a specific high level input since 1990. All Rel Acoustics subwoofers equipped with a high level input use a professional standard Speakon connector and come with a dedicated cable. The Speakon connector is valued for its robustness, ease of use and anti-pullout locking system.

Like most Rel Acoustics subwoofers, the Rel Acoustics T-Zero is equipped with a Speakon high-level input. It comes with a cable for connection to the amplifier’s speaker terminals.

Another major advantage of Rel Acoustics subwoofers is their high current amplifier. Current (intensity), not voltage, is the key element to set the subwoofer’s large drivers in motion. Since 1998, the Welsh engineers have made sure that the integrated amplifiers in Rel Acoustics subwoofers produce a high level of current. This ensures that they reproduce not only the attack and body of a note, but also the echoes during the decay of a sound.

Not all integrated subwoofer amplifiers are created equal, and the amplifiers of Rel Acoustics subwoofers are specifically designed to reproduce the lowest notes.

Today, Rel Acoustics is recognized across the globe as a leading brand in the premium audiophile subwoofer market. The Welsh company offers several ranges of subwoofers to suit all budgets and uses.

Rel Acoustics T Series and T/i Series (hi-fi and home theater)

Rel Acoustics HT Series (home theater)

Rel Acoustics S Series (hi-fi and home theater)

Rel Acoustics Reference Series (hi-fi and home theater)

Rel even offers a subwoofer specifically designed for easy integration that can be used on the floor or mounted on the wall: the Rel Acoustics Habitat 1, which features wireless connectivity for even easier placement in the room.

https://dfxqtqxztmxwe.cloudfront.net/images/dynamic/Caissons_de_basses/articles/Rel_Acoustics/RELHABIT1NR/Rel-Acoustics-Habitat-1-Noir-laque_L2_1200.jpg
The Rel Acoustics Habitat 1 is designed to be wall-mounted.

Rel Acoustics T-Zero: packaging & accessories

The Rel Acoustics T-Zero subwoofer comes with a power cable (1.8m) a high-level connection cable equipped with a Speakon connector at one end and speaker cables at the other end, and a user manual. Everything comes in a compact box inside of which the subwoofer is wrapped in a plastic cover and protected by two polystyrene blocks.

Rel Acoustics T-Zero: presentation

The REL Acoustics T-Zero subwoofer is a very compact model that is only 26cm deep, 24.1cm high and 21.6cm wide, making it very easy to place in the room. It features a very appealing lacquered finish (our test model had a white lacquer finish) like the other models in the range. This lacquered finish adds to the premium look of this cabinet, but be careful: it attracts fingerprints very easily and can generate reflections during home theater sessions, depending on the placement of the cabinet in the room.

Sealed cabinet

The REL Acoustics T-Zero is a sealed subwoofer. Underneath its reinforced anti-vibration cabinet is a down-firing 6.5” long-throw driver. The omnidirectional dispersion of sound waves makes placement of the subwoofer easier. The class D amplifier module delivers 100 watts RMS.

Connectors

The REL Acoustics T-Zero subwoofer’s connectors include a mono RCA low-level input, a dedicated RCA LFE input, and a stereo high-level input in Speakon format. This professional-grade connector is valued for its robustness, ease of use and anti-pullout locking system. The manufacturer recommends using a high-level connection that allows the sub to receive exactly the same signal as the speakers. A dedicated 10-meter long cable comes with the subwoofer for this purpose. The user manual provides many examples of connections depending on the type of amplifier used.

The REL Acoustics T-Zero subwoofer has a mono RCA low-level input, a mono RCA LFE input and a stereo high-level input (Speakon connector).

Settings

In order to optimize the performance of the REL Acoustics T-Zero subwoofer to the associated speakers, the phase (0 or 180°), the high cutoff frequency (30 to 120Hz) and the gain can be adjusted.

It is possible to connect the subwoofer to two amplifiers at the same time: an AV receiver connected to the LFE input and a hi-fi amplifier connected to the high-level input. This is why the gain for the high and low level inputs is independent of that of the LFE input. This way you can have two separate settings for hi-fi and home theater use.

Finally, in addition to the main power switch, there is a switch to activate or disable the energy saving mode that allows the sub to automatically enter standby mode when it is not being used.

The high and low level inputs have a separate level control from the LFE input, allowing the subwoofer to be connected to both hi-fi and home theater amplifiers while maintaining a separate setting for each listening situation.

Rel Acoustics T-Zero: key specifications

Design

  • Sealed enclosure
  • Down-firing 6.5” long-throw driver

Amplification

  • Class D amplification module
  • Power: 100 watt RMS

Measurements

  • Low frequency: 38Hz (-6dB)
  • High level input impedance: 150k
  • Low level input impedance: 10k
  • LFE.1 input impedance: 10 kohms

Settings

  • High cutoff frequency: 30 – 120Hz
  • Phase: switch, 0 – 180°
  • Gain: 80dB, separate for the high/low level inputs and LFE input
  • Main power switch: on/off
  • Power modes: Energy Saver (automatic standby on) / Always On (automatic standby deactivated)

Connectors

  • Low level input (mono, RCA)
  • High Level input (stereo, Neutrik Speakon)
  • LFE .1 input (RCA)

General

  • Dimensions (W x H x D): (feet, connectors and buttons included)
  • Weight: 6.8kg

Accessories

  • Power cable
  • Speakon stereo connection cable (10m)
  • User manual

Rel Acoustics T-Zero: listening conditions

We mainly tested the Rel Acoustics T-Zero subwoofer with the Sonus faber Lumina I speakers that we will be reviewing in the near future. Mounted on NorStone Stylum 2 speaker stands, they were powered by the excellent Lyngdorf TDAI-1120 WiFi/Bluetooth stereo amplifier using NorStone Arran MC speaker wire mounted with banana plugs. The subwoofer was placed in line with the speakers, near the left speaker.

We also paired the subwoofer with the Jean-Marie Reynaud Lunna speakers we recently reviewed for a few listening sessions.

Following the manufacturer’s recommendations, we first connected the Rel Acoustics T-Zero subwoofer to the amplifier with the supplied cable, connecting the red and yellow cables to the right and left positive speaker terminals and the black cable to one of the negative speaker terminals. As soon as the power was turned on, the cabinet started to “hum”, indicating a grounding problem. By connecting the black cable to the ground connection of the Lyngdorf TDAI-1120 (the one intended for the phono input), the humming disappeared immediately. In the absence of a ground connection, it is possible to connect this cable to the chassis of the amplifier by winding it around one of the screws on the rear panel.

We then adjusted the level of the subwoofer (High / Low Level knob) to match that of the speakers, then we set the high cutoff frequency of the subwoofer slightly above the low cutoff frequency of the associated speakers (set at about 75Hz with the Lumina I).

Rel Acoustics T-Zero: listening impressions

With the Sonus Faber Lumina I speakers

The extremely compact Sonus Faber Lumina I speakers are somewhat limited in the low end of the spectrum by their 5” driver and modest load volume. The frequency response announced by the Italian manufacturer attests to this with a low frequency of 65Hz. It is therefore very interesting to pair them with a subwoofer such as the Rel Acoustics T-Zero, which is also very compact and therefore easy to integrate and ideally sized for this type of speaker.

Once the subwoofer was set up and turned on, we enjoyed more extended bass with real physical presence. Where other speakers only sketch out a bass line, the small Rel T-Zero conveyed it with depth and conviction. Of course, 38Hz is not incredibly deep, but it really helped establish the acoustic message.

When you associate a subwoofer with small compact speakers, it is in fact the whole acoustic image that is enhanced. The bass produced by the T-Zero brought texture to the sound, emphasizing the mids, which then seemed to gain substance and density. The extension of the lows also benefited the higher frequencies which, by contrast, seemed more legible and more detailed. The music was rendered even better than it was with the speakers alone, and had more body and substance. The contribution of the Rel Acoustics T-Zero subwoofer in the low end of the spectrum also improved the overall spatialization of the soundstage, which seemed more extensive and spacious.

The Rel Acoustics subwoofer was lively and responsive, without any lag. The attacks were clear, the bass was even quite impactful on songs laden with low frequencies. The 100 watt amplification, which may seem rather low on paper, proved to be enough to offer fairly robust lows and to control the 6.5” driver.

With Morcheeba’s bass-heavy track Never Undo, the Rel Acoustics T-Zero subwoofer allowed us to enjoy the music without any frustration. The bass was generous, lively, deep and well nuanced.

On Tracy Chapman’s The Love That You Had, the percussion gained impact and vigor, the bass line was well defined and displayed beautiful depth. The song became more realistic and intense.

With Melody Gardot’s song C’est Magnifique, the bass line, which is rather timid when using only speakers, gained a nice presence that in turn provided some welcome texture. The bass was well defined and perfectly in place, underlining the melody without overdoing it.

For home theater, the Rel T-Zero provided explosions and collisions with more substance and contributed to the credibility of the soundstage in its entirety. The sound had more texture, intensity, substance and impact.

With the JMR Lunna speakers

The Rel T-Zero and Jean-Marie Reynaud floorstanding speaker pairing was much less interesting. This can be explained by the fact that these speakers can go almost as low as the subwoofer, with nice presence and great articulation even at low level, thanks to their excellent tuned triangular transmission line enclosure. The contribution of this subwoofer isn’t significant. It’s best to opt for the Rel Acoustics T-7i or even the Rel Acoustics T-9i to enjoy any real benefit.

The Rel Acoustics T-Zero subwoofer is designed to be mainly used with small compact speakers. However, it could be interesting to pair it with small floorstanding speakers that are a little timid in the lows or that provide lower bass levels than the JMR Lunnas, such as the Jamo S 805s, the Dali Oberon 5s or the Highland Audio Oran 4305s.

Rel Acoustics T-Zero compared to the Dali Sub E-9 F, Elipson Prestige Facet Sub8 and Cabasse Santorin 21 M2

Dali Sub E-9 F

Only slightly less expensive than the Rel Acoustics T-Zero, the Dali, which costs €549, is larger (30 x 28 x 31cm) because it uses a bigger driver (8.6”) and has a bass-reflex enclosure. This requires a larger load volume than a sealed design. The Dali sub can therefore deliver denser and more intense bass thanks to its larger emissive surface and bass-reflex design.

The downside is that the lows are rounder, a little fuzzier and less responsive than those offered by the Rel T-Zero. In addition, the Dali Sub E-9 F’s front-firing driver and rear port can make it more difficult to position. For example, placing it in the corner of the room has a much greater impact than it would have on the Rel Acoustics model.

Regarding connectors, the Dali subwoofer has a line input (RCA stereo) and an LFE input (RCA mono) but does not have a high level input. Consequently, it is mainly intended to be used in a home theater system to boost the sound of movies and series, or with a stereo hi-fi amplifier equipped with a SUB output or a pre-amplified RCA output. It’s not possible to connect it to the speaker terminals of a classic stereo amplifier.

More lively (sealed enclosure and smaller driver) and more nuanced, the Rel T-Zero is particularly suited to high-fidelity listening. Easier to place thanks to its down-firing driver, it has a wider range of connectors that allow it to be used with any stereo or A/V receiver.

Elipson Prestige Facet Sub8

More affordable with a price under €500, the Elipson subwoofer also has a very nice lacquered finish. More imposing than the Rel model because of its 8” driver and its bass-reflex enclosure, it is still easy to place in a small room. Its 150-watt class D amplifier efficiently drives the frontal driver, which delivers deeper and fuller bass than the Welsh sub.

Despite not having a high level input, the Elipson Prestige Facet Sub 8 subwoofer is equipped with a line input in addition to its LFE input and can therefore be used with any A/V receiver as well as with hi-fi amplifiers and sound bars that have a mono or stereo pre-amplified output.

In practice, the Elipson subwoofer proves to be quite spirited with an expressive character that works wonders for home theater. For hi-fi listening, however, it is a little less refined and nuanced than the Rel T-Zero, which is more nuanced but also more incisive.

Cabasse Santorin 21 M2

The Cabasse Santorin 21 subwoofer has been a reference in the French manufacturer’s catalog for many years and is designed to accompany among others the Cabasse Alcyone 2 and Cabasse Eole 4 satellite speakers, in 2.1 stereo setups as well as in 5.1 (and greater) home cinema systems.

Sold for €599, this subwoofer features an 8” driver and a bass-reflex enclosure (rear port) and is therefore bigger than the Rel Acoustics model (33 x 33 x 35cm). As a result, it delivers more intense (larger emissive surface and bass-reflex enclosure) and deeper lows with a low frequency of 35Hz. Its driver is down-firing, which means it can be positioned more easily in the room as the sound is distributed across 360°. The Cabasse sub has more connectors, with Line inputs and outputs (RCA stereo) and high-level inputs and outputs (screw speaker terminals).

While the Cabasse model outperforms the Rel T-Zero with the depth and amplitude of the bass that it delivers, the Welsh subwoofer takes the lead in terms of liveliness and musicality, with a sharper sense of nuance.

Rel Acoustics T-Zero: conclusion

Its 6.5” driver and 100 watt amplification don’t allow the Rel Acoustics T-Zero to explore the lows as thoroughly as more powerful models with larger drivers. Therefore, it is not intended to be installed in a large listening room or to support a home theater system that uses floorstanding speakers.

But it really works wonders when paired with satellite speakers or small compact speakers with 4” or 5” drivers. The bass it produces is sufficiently intense and responsive to integrate seamlessly with the higher frequencies without the listener being able to tell whether the speakers or the subwoofer are playing. While not extremely deep or physically impactful, the bass is lively, well-structured and nuanced, with just the right amount of presence and energy to energize the sound. It provides texture and substance without ever being overpowering or overwhelming the listener with its presence. The result is a more balanced, airy, realistic and immersive listening experience.

When paired with the ultra-compact Sonus Faber Lumina I speakers, The Rel Acoustics T-Zero subwoofer provides an even richer, more balanced listening experience.

If your compact speakers are slightly restricted in the lows and you have a medium size listening room, don’t miss out on this small Rel Acoustics T-Zero subwoofer that’s unbeatable at enhancing hi-fi and home theater listening.

What we liked

  • The very responsive and nuanced lows
  • The compact format making it easy to position 
  • The elegant finish
  • The connectivity

What we would have liked

  • For it to be available in a matte finish to reduce reflections for home theater use


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