Hardware Reviews

Eclipse TD725SWMK2


I reviewed a sub for another publication recently and was surprised by how much it seemed to improve the sound quality in the mid and treble, how on earth could a low frequency driver that was limited to frequencies below 60Hz make the system more revealing higher up the range. I put this question to Hideto Watanabe, senior manager at Eclipse Home Audio who played bassoon and conducted in an orchestra in his youth, a factor that clearly informed his answer. Apparently it comes down to the ‘pyramid’ of dynamics that an orchestra needs to achieve for it to produce what Hideto describes as a ‘rainbow of harmonics’. The pyramid is a tonal one with bass at the bottom as a foundation, midrange notes in the middle and treble at the top; the wider the area of the pyramid that each tonal range occupies the greater the dynamics (power) required from that range. In essence bass notes need to be supporting the mid and treble to achieve a good harmonic result from the entire orchestra. One of the jobs of a conductor is to achieve this balance in the concert hall, studio or wherever the orchestra plays.

That being the case you can see how a subwoofer that’s limited to low bass frequencies can assist the main speakers in producing greater harmonic detail in a stereo system. This certainly proved to be the case with Eclipse’s largest subwoofer the TD725SWMK2. And it is big, weighing over 50 kilos and measuring over 50cm cubed, it makes its presence felt in the room especially if you put it in what Eclipse considers to be the optimum position (see below).


The TD725SWMK2 has two 10inch drive units arranged opposite one another with a torsion rod between them. The sub is actively driven by a 500 Watt ICEpower amplifier, the class D technology developed by Bang & Olufsen which was chosen for its combination of speed and power as much as efficiency. Eclipse are of the opinion that for a subwoofer to be beneficial it needs to time as well as the main speakers, this quality is a major strength of their single driver speakers such as the TD510Mk2 that I got a great result with in 2017. The need for speed is also the reason for the choice of 10 inch drivers which can be lighter and thus faster than the 12 inch variety found in many big subs. Eclipse makes up for the smaller cone area by using two active drivers facing in opposite directions, this is why there’s an aluminium brace between the two units and means that when the cube is sitting off square in the room the energy can be pointed towards the corners where the sound won’t be cancelled by reflections. This angled orientation can be used wherever the sub is placed.

Connections can be made in various ways, there are two selectable inputs with RCA only on the first and both high level speaker inputs alongside line level inputs on RCA and XLR sockets on the second. Input 1 is designed for home theatre applications primarily while input 2 is for audio, Eclipse have a preference for the speaker cable connection wherever possible. The latter can be taken from amp to sub and then sub to speaker or you can run parallel cables from the amp to sub and amp to speakers, I went for this arrangement as I only have a single run of my preferred Townshend F1 Fractal speaker cable which went to the main speakers as usual, I used some Townshend Isolda (which is very similar) to hook up the Eclipse. There are controls for low pass filter (LPF) which sets the highest frequency the sub will deliver (or switched off), and output level via knobs on the rear. Both of these alongside a number of other parameters can be adjusted remotely and there’s a display to show where each is set. You can also mute output, reverse phase or switch in the ‘bass’ setting which adds emphasis to the low end and is designed for non-acoustic material where a bit more welly can enhance the experience.


Sound quality
I used the TD725SWMK2 to augment a pair of Bowers & Wilkins 802 D3 loudspeakers, these are substantial floorstanders with a specified low frequency roll-off of 17Hz, which you would imagine is more than deep enough. However, just because a speaker has a wide frequency response doesn’t mean it has the power to do justice to the lower end of the scale. What you actually hear depends on the source, amplifier, cables and room and getting very low frequencies out of a speaker requires a surprising amount of power. This is why active speakers are usually better at delivering bass, they have a big amplifier connected directly to the drive unit with no crossover to absorb energy. A subwoofer is an active loudspeaker for bass only and this Eclipse is a particularly refined example of the genre. 

It not only delivers superb low frequency extension but does so in a clean, undistorted fashion which has the effect of making listening a more enjoyable experience. The presence of a remote control to adjust both volume level and roll-off is a real boon during set up but it also comes in handy when playing a broad selection of music. I didn’t find myself changing the level very often but once in a while a track would come along that had too much bass for my room at high ish levels, on those occasions the ability to turn it down from the listening seat was appreciated. 


Initially I positioned the Eclipse for maximum sound quality, which is also approximately the same place as minimum convenience given that it’s in between the main speakers and 80cm in front of them. Or the middle of the room as it’s known in my place, nonetheless the results were inspiring enough for me to leave it there for longer than I had planned. It really does make listening more engaging. This is primarily because it enhances timing. Nimble low bass is a very rare thing, you usually get either articulate bass that’s not very extended or low bass that seems slow and thick. With the TD725SWMK2 both are combined to powerful effect, that being the aforementioned rainbow effect of harmonics in the mid and treble becoming clearer so that the sound is more detailed but also more fluent than without the sub. It also takes the edge of what often seem to be forward or thin recordings. The 802s are ruthlessly revealing of such shortcomings even with a very clean source but with the Eclipse in the system everything is subtly fleshed out, tone is deeper, lyrics more intelligible and the groove totally irresistible. Especially when playing Missy Elliott’s finest work Da Real World, where not only was the bottom end reinforced but the mid was cleaned up to the extent that all of the lyrics from the likes of Eminem an Redman could be understood. This inspired me to play another hip hop album in To Pimp a Butterfly(Kendrick Lamar) where the bass exercised the air in the room but the jazzed backing was a total distraction, there is so much going on in tracks like King Kunta that you have to sit back and marvel at its inspiration.


Before reluctantly accepting that having a sub in the system would make reviewing speakers more challenging than usual I put it to the right of the right hand channel in a more convenient spot and was thrilled to discover that almost all of the goodness that could be enjoyed in the central position remained in the mix. The image had excellent 3D solidity and the integration was remarkable, you really can’t place the sub with your eyes closed on many tracks. I was inspired at this point to indulge in some of the more excessive bass tracks in my collection, including Lorde’s Royals which did need turning down, Kraftwerk’s Elektro Kardiogramm and their live version of Radioactivity (Minimum-Maximum), which is utterly superb in its combination of weight and articulation, and terrifying in its lyrical content. 

As you can surmise I got a great result with this subwoofer, Eclipse have proved that even with large loudspeakers and a powerful 150W ATC amplifier things can be improved by an active sub if that sub is executed with as much precision as the TD725SWMK2. It’s big and it’s expensive but if you have a great system already you will love what it does for your music.


Type: Sealed enclosure active subwoofer
Drivers: 2x 250mm paper/Kevlar
Inputs: Hi-level speaker input, low-level RCA and XLR
Output: speaker output
Frequency response: 20 – 150Hz (-10dB)
Amplifier power: 500W (THD 1%)
Controls: low pass filter (30Hz – 150Hz), gain, phase (0 or 180 degrees), bass/direct play mode, input selection, power (on/off).
Accessories: remote control, grilles, felt feet
Dimensions (HxWxD): 500 x 545 x 524mm
Weight: 51kg
Finish: piano black
Warranty: 2 years

Price when tested:
Manufacturer Details:

Denso Ten




Jason Kennedy

Distributor Details:

Decent Audio
+44 (0)5602 054669

Notify of
Newest Most Voted
Inline Feedbacks
View all comments