We take multichannel audio for granted, but not even AV old-timers who can remember the original Dolby Surround decoders were the first kids on the block. Furthermore, multichannel music predated the closing credits of a film soundtrack – never mind hi-res formats like DVD-A, SACD and Blu-ray audio. For domestic surround sound's beginnings, you need to go back to the early 1970s and the crazy world of quadraphonics.
To achieve the best real-time playback from most quad albums you needed, until recently, to acquire the sophisticated decoders of the era. Needless to say, specimens that still work are expensive and rare. The SM465 Surround Master from Australian firm Involve Audio aims to rectify that problem.
On the rear panel of this slim box are a stereo input, and no fewer than eight phono sockets containing the outputs. In one operating mode, the Surround Master will deliver Involve's two-channel virtual surround system – Two Speaker Surround, or TSS – to two of them. A neat trick is that the stereo input is passively routed to these automatically when the Surround Master isn't powered up. In the other mode, the sockets are configured for quad (4.0) or 5.1. Just connect these outputs to your amplification. Of course, you'll need an amp/receiver with multichannel inputs. I used both an Onkyo TX-NR906 AVR and a 40-yearold Pioneer QX-949 quad receiver.
You may think the Surround Master apes older gear by performing Involve's proprietary decoding tricks in the analogue domain, but with more modern circuit techniques. Things are, however, more complex than that. Basically, the audio is fed into circuits that buffer and apply precise phase-shifts to the incoming stereo audio. The resulting signals are passed simultaneously to a pair of powerful chips that combine analogue-to-digital conversion, real-time DSP and digital-to-analogue conversion. Each of the Surround Master's two modes involves loading different DSP software-code at startup, so you have to 'power cycle' the unit after flicking the mode switch for the new setting to take effect.
The analogue outputs from these chips go to the eight rear-panel sockets via filters and buffer circuitry. The DSP is responsible for detecting spatial cues, extracting appropriate content and passing it to the relevant channels.
The Surround Master's 'Involve' process is claimed to work with the QS surround format, and lesser-known ones like Matrix-H that the BBC used occasionally for FM radio broadcasting in the late 1970s. It will also deliver results from Ambisonic material, matrix-encoded (e.g. Dolby) movies and regular stereo audio. It will not give optimal results from SQ software, which Involve claims is tricky to decode properly. As a result, the firm sells a separate model specifically for SQ use and owners of SQ-encoded vinyl LPs.
Note that Involve is swapping the Surround Master's casing from the basic-looking plastic one here to a slicker model in a blue chassis.
Getting surrounded
I firstly tried using the Surround Master's TSS setting with some regular CDs, and was on the whole impressed with what I heard. It seemed to extend the soundfield further into the room, and some instruments were given extra clarity. However, with lesser material – like mediocre cassette recordings – it can blur the soundstage and smear detail.
But it's conversion to multichannel that we're interested in. I tried a DVD of Star Wars: Episode IV, comparing the Surround Master and Pioneer quad receiver with my Onkyo given a multichannel bitstream over HDMI by a Cambridge Audio 751BD. That player's stereo analogue output fed the Surround Master.
Although much is going on and there's clear delineation between channels, the soundscape lacks accuracy relative to discrete surround. John Williams' orchestra – and, confusingly, some dialogue – is behind you! On other occasions, effects – like Death Star doors sliding open – don't seem to correspond to what's happening onscreen. This is a revealing test; music listening, remember, doesn't give you visual clues to what you should be hearing.
Sometimes, the system fares better. The 'whoosh' of Luke Skywalker's landspeeder is effective, panning correctly from rear-left to front-right. The background babble of the cantina sequence is also finely-etched, as are most busy scenes where so much is going on.
Now for music. Pulp's Have You Seen Her Lately? sounded like a discrete quad mix, the shimmering keyboards taking positions in the rear channels with Jarvis Cocker at the front. Pro-Logic II sounded anaemic in comparison. One EskimO's Astronauts also benefitted from the Surround Master's presentation, the expanded soundstage giving definition to acoustic guitars and brass instruments. At the close of the track, percussion passes with eerie conviction from one speaker to the next – it's almost as if it were mixed that way.
The sequenced synth that kicks off The Who's Baba O' Reilly moved with precisiontiming across the channels, setting the scene for an immersive performance; Pro-Logic II, and other DSP modes, were far less exciting. A CD of Bach organ works was less successful, though, insofar that the Surround Master extended the organ's pipes to the rear channels; what I should have heard from those is the reverberative effect of the venue's acoustic. It was exciting, just not natural. Similarly, during a performance of Mozart's Symphony No. 40 I felt as if I was sandwiched between two halves of an unconventionally arranged orchestra.
Enter the Matrix
And surround material? I dug out an old Matrix-H tape of a Genesis Knebworth performance, but this sounded muddled and indistinct. The tape, I suspect, was to blame. A DVD performance of another prog band, Gentle Giant, fared much better – the Matrix-H soundtrack had come directly from the Beeb's archives. The track Free Hand was certainly enhanced. Vocals were uncannily assigned to different speakers, while the positioning of vibraphone, organ and guitars helped to convey a definite sense of space.
The Surround Master was superior to my Pioneer's basic QS/RM decoder when it came to Charlie Freak from Steely Dan's QS-encoded Pretzel Logic LP. There was far less leakage between front and back, as the track's violin and sleigh-bells demonstrated. Another QS album, rock-opera Moses and the Impossible Ten, yielded an expansive soundstage, with the opening brass locked into the rear channels, and given more definition than offered by either the Pioneer or Pro-Logic II.
SQ-encoded LPs got an interesting, but inaccurate, four-channel mix. The alternative SQ version of the Surround Master (the SM-465SQ) was, however, fantastic – on a par, at the very least, with the last of the great analogue decoders. I was in a position to compare the SQ-encoded Alan Parsons mix of Pink Floyd's Dark Side of the Moon with the four-channel version available in the Immersion box set, and the two were very close. The clocks at the beginning of Time appeared as long-lost sonic treats.
Another SQ album that fared well was Mike Oldfield's Tubular Bells. With Andre Previn's Carmina Burana, though, the effect was more subtle – the choral layers were better-defined than they were with the elderly Pioneer receiver's decoder. The newer Onkyo's DSPs, in contrast, tended to thicken the sound or add artificial ambience.
Overall, I'm taken with this modest, unique unit. It's audibly different to the surround modes you'll find on the average AVR. The Surround Master is surprisingly transparent – it doesn't alter tonal balance or add appreciable distortion. Purists may scoff , but the unit can add a dimension to stereo listening and give you fresh insights into your music collection.
For movies I would always recommend a discrete multichannel soundtrack. But for matrix quadraphonic material – SQ or QS – there's currently nothing around to touch the Surround Master. Retro enthusiasts keen to buy just need to choose the right model...
Specifications
CONNECTIVITY: Stereo phono inputs; 8 x phono outputs (can be used for 2.0, 4.0 or 5.1)
DIMENSIONS: 210(w) x 30(h) x 125(d)mm
WEIGHT: 0.3kg
FEATURES: Custom Involve DSP code; three-band processing; cables included; external power supply; two-channel bypass; two-channel virtual or 4.0/5.1 mode; QS, Matrix-H and Ambisonic (standard non-SQ model); SQ-I (mathematically accurate) and SQ-V (for compatibility with non-optimal sources) modes on SQ model