Are four subs better than one? With more AVRs sporting four discrete subwoofer outputs, can quad-sub performance outweigh the backache, cabling and visual carnage? In another top Essential Install Review, and with some help from REL, Richard Stevenson dons the weightlifting belt to find out.
Four discrete subwoofer outputs are becoming the norm on high-end AVRs and processors, and flagship EQ systems from the likes of Audyssey and Dirac now offer individual measurement and EQ for each. Is this just manufacturer Top Trumps or are there genuine benefits in going for a x.4.x configuration?
Never afraid of ridiculous challenges, we called our good friends at REL and secured four S/812 subwoofers to find out.
Should audio guru Dr. Floyd Toole et al be relied on for audio wisdom, four individual LF-producing transducers spread around a rectangular room should prove sonically superior to a single unit. Cited benefits include more even bass distribution, minimising room nodes, greater dynamic range and placement flexibility. More to the point, is a four-sub configuration a solid value-add sale to those customers looking for the very best?
Physical space, accessible power socket, signal cabling and aesthetics are likely to present challenges to varying degrees. In my room, two subs at the front is easy, integrating two at the rear, less so. The main door is in the way of near-corner placement and signal cabling across the room entrance would be a comedy trip hazard.
Thankfully, I had installed power sockets in the rear wall for just this eventuality and Rob Hunt at REL, knowing my room, brought along a pair of REL AirShip II wireless TX/RX systems.
The front layout hadn’t changed with two subs facing forward about a quarter way in from the side walls. The rears were facing forward, flush to the back wall, and about a third of the way in. You still wouldn’t want to rush into the room with a tray of wine glasses as the rear subs stick out into the walkthrough from the main door behind sofa.
Aside from assigning four individual subwoofers in the reference Marantz AV-10 pre-amp, the initial set-up was an old-school analogue. With EQ for the four LFE channels switched off, Rob balanced the levels and cut-offs to the main speaker system by ear. Much listening to known cinema soundtracks, Dolby Atmos music and even a bit of stereo in 2.4 was undertaken.
Latterly, the entire system was measured and equalised Audyssesy MultEQ-X and then Dirac Live Full bandwidth with Bass Control, reviewing the same content for each. That is a whole lotta faff – and all without a glass of wine.
ODDS OF 4:1
Of results predicted by audio gurus such as Floyd, I would say LF smoothness across the listening positions is the most obvious effect of stepping up to four subs. A quirky suck-out just in front of my sofa was all but gone, and you could shuffle around the seating positions with barely a change in bass balance. Most interestingly, Mrs S, who is adept at complaining that plates are falling off shelves in the kitchen two rooms away during big LFE effects, was strangely silent. With the same measured volume in the cinema room, there was significantly less bass escaping along the corridor and into the kitchen.
Interestingly the perceived LFE performance difference between Bass EQ on and Bass EQ off, with either system tested, was notably less dramatic than with a single sub. Ironically, for the LFE channels alone, I would go with Rob’s baseline set-up without EQ as it felt slightly more edgy and punchier than the EQ’s version. Depending on the room, your audio mileage may vary.
One other notable sonic benefit, although I am at a technical loss to explain it, is that the four sub-systems sounded well-integrated into the whole sound mix at a far wider range of volumes than a single sub. I am forever ‘tweaking’ the gain on a single sub when the volume goes up or down, and the relative outputs of main speakers and sub diverge when you move away from the measured EQ SPL (usually 85dB). With the four subwoofer system, the effect was very much smoothed out, even when flicking between music tracks with notoriously varied recording gain.
The two potential benefits that didn’t leap out of the test were greater dynamic range and placement flexibility. Having had some truly epic REL subwoofers do some amazing dynamic magic in my relatively small room, perhaps I simply don’t have the space to get any improvement in transient attack or scale from the quad set up. Of course, nudging up the LFE gain a little can have a similar effect, so in the spirit of thorough testing, the four RELs got pushed to night-club levels. It was a stupendous high-volume, high-power performance from the S/812 array, two of which (unspiked on carpet) moved several inches out of place.
As for placement flexibility, if placing four subs and dialling them into the room is more flexible than a single sub, the customer’s room must be the size of a village hall!
Of the potential sonic downsides, I encountered no obvious phase issues. The overall effect, with and without EQ, sounded smoother across more seats in the room and offered better integrated LFE across a far wider range of listening volumes than a single sub.
Verdict
The cost and complexity of four subs are significant – adding circa £10k on the retail systems price as tested here. Yet, with more AV electronics and EQ systems offering four individually controllable LFE channels, the concept certainly has merit for well-heeled customers wanting the best in cinema sound.
