To Find Out ...Surround Sound system in home studio

To Find Out ...

How to setup a Surround Sound system in home studio?

Surround Monitoring
If you've been following this series, you'll know that a surround monitoring system comprises six speakers, one of which is a sub-bass or LFE unit handling low-frequency effects below 120Hz (for more details on the speakers and how they are arranged spatially, see part four of this series). Of course, the first difference between this and the monitoring system you probably have at the moment is that you're going to need more speakers, and space to put them in! In the smaller studio, finding space for surround monitoring can be a real problem, but if you don't have room for five full-range speakers and a sub-bass unit, you can opt for a system that uses five smaller speakers, such as the popular Genelec 1029A (another advantage is that Genelec also make a dedicated, separate sub-bass speaker for these). However, simply increasing your number of speakers, finding a suitable sub-bass unit and arranging them all appropriately isn't the end of the story; how do you drive them from your mixer? Unfortunately, there are few project-studio mixers currently available that offer surround buss outputs plus surround monitoring — most still only provide for the connection of stereo monitoring, even if they have some kind of multi-buss surround mode. Even assuming you have the necessary number of spare hardware outputs from your mixer, when you want to turn the overall monitor level up or down, how do you control the channels together so that their relative levels remain constant ? Adjusting several controls in tandem is not really practical.

If you use passive monitors, the solution is relatively affordable and straightforward — there are reasonably powerful domestic surround amplifier/decoders available with separate analogue inputs in addition to the more usual optical input, and you can connect your master surround output busses to these, and drive the speaker from the amp's speaker connections. Not only is this the most cost-effective option, it also provides you with a one-knob means of setting your monitor output level via the amp.
If you use active speakers, however, the optimum setup is less obvious. There are commercial surround decoder/amplifiers that have individual line-level ins and outs, and you can use amps like these in the signal chain as described above, to drive your active monitors and control the level, but these are more expensive.
One practical, though not entirely satisfactory solution is to use the multiple buss outs (either as discrete analogue feeds or as a composite digital feed if a suitable interface card is available) from a mixer configured for surround mixing to feed a multitrack recorder such as an ADAT or DA88, which you'll be using for six-channel surround mastering anyway (more on mastering in a moment). The outputs from the recorder (which must be left in input monitor mode) are then routed directly to a set of active monitors as shown in the diagram on the left. Note that you could also record onto 18 tracks of a 24-track hardware recorder and then mix your six surround channels to the remaining six tracks to avoid the expense of a separate mastering machine.
However, the problem when monitoring directly from the multitrack outs is that when the optimum level is being fed into the recorder, the monitors will play back at a fixed level determined by how you set the trim pots on their back panels. It's quite possible to set this up for a sensible monitoring level, but there's no simple way to control that level. When you're at the tracking stage, you can turn down the mixer buss outs to feed a less-than-optimum level to the multitrack recorder, and that will bring down your monitoring level accordingly, but when you're doing your final mix to the multitrack master recorder, the level is effectively fixed as you need to record at an optimum level. Of course, if you use passive speakers powered by a surround amp (again fed from the multitrack outs), you can still control the level via the amp. Professional six-way level control boxes are available, such as the Audient ASP10 shown on the previous page, but these are still a bit expensive for project-studio use (the ASP10 retails for just under £2000). As expressed in my Leader column in August last year (see www.soundonsound.com/sos/aug01/articles/leader0801.htm), I'm still waiting for the affordable box that functions as a surround monitoring volume control.
Surround 'Mastering'
When we complete tracks by mixing them into stereo, most of us consider them finished. These days, we can even burn those stereo files to a CD-R which can then be played back on any domestic CD player. A surround equivalent to these procedures is harder to come by. Firstly, you have to have a surround mix recorder — something capable of recording six tracks simultaneously. This isn't too difficult — six spare sequencer tracks in a software-based setup, or a stand-alone multitrack recorder capable of recording six or more channels simultaneously, like an Alesis ADAT, or Tascam DTRS machine, will suffice, provided you note carefully which track relates to which channel of the final surround mix! But playback of this 'master' is then only going to be possible from that computer, or from that type of multitrack recorder. To arrange it such that your mix can be played back on domestic systems, you need to get it onto DVD, and this requires more hardware and/or software. First you need to create files that DVD players will recognise, and for the greatest chance of player compatibility this currently means AC3 files (for Dolby Surround) or DTS files. Not only do these have to be encoded by software, there are also many settings which have no counterpart in stereo mastering — the metadata — which have to be determined at this stage, as explained in part four of this series. Dolby Digital AC3- and DTS-encoding software is available for use with Digidesign's Pro Tools, but it's still fair to say that affordable, project-studio oriented software to create these files is scarce at the time of writing, although I think it can only be a matter of time before suitable solutions become widespread.
The second part of the process involves a DVD burner to get the encoded files on to the actual disc, and again, the hardware, although falling in price, is still expensive compared to that of stereo CD-R burners.
Of course, mastering houses and the top studios have access to expensive top-end DVD encoding and production software, as well as the necessary hardware writers. If you're prepared to pay to use such facilities, you can produce DVDs from six-channel computer sequencer files or ADAT/DTRS tapes that you've prepared. However, this method is expensive, and takes the last stage out of your hands, which can be irritating if you're used to producing a finished product in your home studio yourself.
If all of this sounds impossibly daunting, it's important to remember that there are nevertheless people mixing in surround — and not just at the top end of the industry, either. We spoke to two engineers at very different ends of the business to see how they are coping with some of these issues.