Eclipse TD520SW Audiophile Subwoofer – HiFi Review

Eclipse TD520SW Audiophile Subwoofer – HiFi Review

I’ll start by making it clear that I am a big believer in the sonic benefit adding a subwoofer can bring to a stereo speaker system. Several years ago, I had the pleasure of reviewing a pair of Jern 14 DS small standmount speakers. The Danish loudspeaker maker is known for engineering its speakers from cast iron and the 14 DS design is intended to be partnered with a subwoofer. No surprise then that when this 40kg audiophile subwoofer from Eclipse arrives, I’m keen to hear how it performs with the Jern speakers that I’ve been using since my 2017 review.


Eclipse TD520SWThe TD520SW is the smaller of the two subwoofer models in the Eclipse range and retails at around £3,250. The design brief behind the TD520SW is to reproduce a rich and powerful bass that is fast enough to complement a two-channel speaker arrangement. Subwoofers are in the business of moving large amounts of air but rather than using one big cone to push the air, Eclipse uses two smaller 20cm cones that are coupled together by an aluminium shaft to create a high speed and strong base reproduction. The aluminium coupling ensures the two speakers are driven in phase. Eclipse uses what it describes as a ‘special material’ to float the drivers in an airtight structure within the cabinet and this arrangement helps to minimise unwanted vibration.

Bang & Olufsen’s ICEpower digital amplifier rated at 250W power output is used to drive the twin speakers with a high degree of accuracy. The Eclipse TD520SW has two inputs – input 1 is designed for multi-speaker home theatre configurations using line-level RCA or XLR inputs, while input 2 is for stereo speaker arrangements as reviewed here. In the stereo speaker arrangement, the subwoofer sits in series with the speakers as the audio signal passes via speaker cables from the amplifier through the subwoofer and on to the speakers. There is a low-pass filter (LPF) setting that enables users to control the low frequency signal being passed on to the main speakers, which seems to blend the output as explained in the comment below from Eclipse when I asked about its function.

The LF dial filters the frequencies output by the subwoofer allowing you to ‘blend’ the speaker and subwoofer together. It can be turned off when using an AV receiver with subwoofer setting options.

The passthrough frequency is adjustable via a rotary control on the back of the sub to allow smooth integration with the speakers you are using, or there is a switch to turn it off. A remote control is supplied and in conjunction with the digital display on the sub unit that gives a visual indication of the settings, the volume level can be tailored from the comfort of your seat to suit your room acoustic and listening position, which is very useful indeed.

Eclipse TD520SWI have been setting the LPF at just above the lowest frequency of the main speakers that I’ve partnered with the Eclipse – for example, at around 48Hz with Fyne Audio’s F1-5 standmount speaker as that’s the lowest frequency specified for that model. With the Jern 14 DS speakers I adjusted the setting to 100Hz, and with a pair of Focal Chora 826-D floorstanding speakers (lined up for a 7.1 AV test next month), the control is set to 48Hz once again.


The Eclipse TD520SW is heavy weighing in at 40kg, so I enlisted some help to get it into position in my listening room. Build quality is high and the binding posts for hooking up passive speakers have good access. The soft piano black finish is rather good looking and something of a talking point for anyone that sees it.


I am using a T+A PA 2000 R integrated amplifier to drive the sub in a series configuration with the speakers. My main playback sources are an Oppo BDP-105 disc player as well as the Auralic Vega G2.1 streaming DAC. With the addition of a short-throw projector, I also watched the movie Tenet, which was seriously good fun with the Eclipse subwoofer handling all the big bass action in this configuration. I used Kudos speaker cable to the Eclipse TD520SW, then QED Supremus speaker cable to the speakers. As part of the reviewing process, I have partnered the Eclipse with the aforementioned Jern 14 DS speakers, Focal’s Chora 826 floorstanders and the tremendously agile Fyne Audio F1-5 standmounts.

I was advised by Eclipse to place the subwoofer front and centre between the main speakers in my listening room. This positioning might be controversial for some in terms of space or aesthetics but in my dedicated listening space, it wasn’t an issue. This configuration would be a problem in my lounge-based stereo, however.

Fyne Audio F1-5

With the Fyne Audio speakers in my smaller lounge driven by Naim’s NAP 250 power amplifier, there’s enough low end to keep me interested but in my larger dedicated listening space, I wasn’t quite getting the engagement I was after. With the Eclipse TD520SW in place, however, things changed. With the LPF set to 48kHz (approximately) the pressure on the Fyne Audio speakers was relaxed, allowing them to simply let the music flow. The Eclipse sub delivers a tight, fast, nimble bass performance that in no way overwhelms the music presentation as it augments the Fyne Audio’s detailed delivery without being too forceful.

One interesting thing I noticed when the LPF system is activated on the Eclipse, was that it seemed to have the effect of reducing the pressure on the IsoFlare surround of the Fyne Audio speakers. I could see the speaker doing less work in the lower frequencies, allowing it to concentrate on the detail in the low-to-mid frequencies and, of course, the high end, which all sounds like a remarkably good thing to me.

Jern 14 DS speakers

As previously mentioned, the Jern 14 speakers are designed with a subwoofer in mind. Its Scan-Speak paper bass cone falls off at around 100Hz and means I need the Eclipse TD520SW to do more work to support the curtailed lower frequency range of the pod-shaped speaker. I usually use a REL T/5i subwoofer to partner the Jerns – a far smaller and more affordable subwoofer – and it does a very decent job.

Once set up with the Eclipse in place, the sound is enveloping and wonderful. I have the crisp, detailed and dynamic presentation I am used to from the Jerns, just as I like them.
With more complex classical tracks, for example, Rachmaninov’s Piano Concerto #2, Moderato (Daniil Trifonov, Philadelphia Orchestra) streamed in 24/96 from Qobuz through the Auralic Vega G2.1 streaming DAC, there is no confusion between the instruments as can sometimes occur as the piano and violins swirl together in the piece. The Jerns are dynamic and in their element with the Eclipse subwoofer supporting their performance beautifully. Compared to the Fyne Audio speakers, I get the feeling that the Eclipse is supporting rather than augmenting the Jern speakers by increasing the lower frequency range of the overall performance. A subtle but notable difference.

Oppo BDP-105 universal disc player

Watching the movie Tenet via the Oppo Blu-ray disc player and a pair of Focal Chora 826 floorstanding speakers, the Eclipse subwoofer delivers plenty of tight bass extension throughout the film. Dialogue is very clear and largely remains unaffected and the mass of confused explosions didn’t feel in any way over powering or fretful. It was certainly noticeable how fast the bass delivery was throughout the movie’s explosive action sequences, and there was less ‘rumble’ than I expected as the sub helped deliver a more engaging movie experience.


As a hi-fi listening experience, the Eclipse TD520SW offers substantial low frequency support for most speaker setups and was a remarkable addition to my listening with smaller designs such as my much-loved Jern 14 DS speakers. Although the price is a bit too high and beyond my current means, I wouldn’t hesitate to include this subwoofer in my setup for its sonic enhancing capabilities and the sheer levels of enjoyment it brings to any playback media. Its series configuration and flexible integration make it an attractive addition to almost any hi-fi setup, including the somewhat finicky Naim electronics I own. It gets an Editor’s Pick from me.

Crisp bass
Configuration flexibility
Serial set up
It wasn’t quite so expensive


Eclipse TD520SW
Eclipse TD520SWColour: black
Type: horizontal back facing floor type (enclosed)
Speaker unit: 20cm cone shaped woofer, valve x 2
Frequency: 25 – 150hz (-10dB) bass mode LPF 150Hz
Nominal output: 250W (THD 1%)
LPF: 30Hz – 150Hz (ON/OFF switch available)
Mode switch: BASS/DIRECT
Harmonic distortion: 0.05% (50Hz ½ nominal output)
S/N: over 95dB
Input: Line (Stereo) x 2, Speaker level x 1
Input sensitivity: 50mVrms (for 250W output)
Input impedance: For LINE input 10kΩ / Speaker level input 3kΩ
Output: Line (Stereo) x 1. Speaker Level x 1
Power consumption: 65W
Standby power consumption: 0.33W
Dimensions: 459 x 420 x 444 WHD
Weight: 37Kg