Sound at the BBC Television Center (part 8)
Equipping For Stereo
“Although we launched stereo formally only a short time ago, we have been doing stereo programmes here for quite a long time. We have been broadcasting in stereo regularly since 1986, but not with an announced service, and all that time we have been building up techniques and putting equipment in place. By the time we announced a formal service last year we were in a position to say right from the start that all your favourite programmes are in stereo. We were saying 60% of the programming was in stereo, and in the evening hours it was more than that. At Christmas time and some weekends we were getting up to 100%. Because we didn’t want to say 'Look how nice this is’, and then have people search the Radio Times to find the odd programme, we said right from the start that we would do everything in stereo that we possibly can. And when people say, 'What does this particular programme gain from being in stereo and why are you doing it?’, we just say 'Well why not?’. It’s like colour, we just do everything. If it doesn’t gain then it doesn’t lose either. On some programmes surprisingly you do gain quite a lot. One instance is the talking head type of show. If there’s a little bit of air around the presenters and guests, a little bit of displacement from side to side, it does help to pick up who’s speaking next. The obvious shows of course are the music programmes which benefit enormously.
“We have been re-equipping and experimenting with microphones and other equipment. In particular, like a lot of other people, we have been chasing manufacturers to make single bodied MS stereo microphones. MS microphones generally work better for us because they have got a single forward facing microphone so you are guaranteed to get a mono compatible signal - the front of one microphone capsule is incomparably better than the sides of two. We did a lot of playing around with the MS stereo microphones that there were. None of them was particularly suitable for boom work in the studio until our old friends at AKG came up with an MS version of a microphone they already had. AKG in the UK are a very forward thinking organisation. They could quite easily see that there was business to be done so they got Vienna to make up an MS version of the C522 for us which they did very well. The good thing about them is that they match our standard mono cardioid, the C460, very well so we can mix them in combinations with no joins showing at all. We have just bought our first ten or twelve and we are buying some more. At the same time we have been re-equipping our booms with stereo cables. It’s these kinds of things you tend to forget, but rigging two cables on a boom is a real pain so we had to look for a stereo cable The Japanese Canare company make a double quad cable and we are installing it on all our booms.
“All of this takes money and time. We have had to develop new specifications for things like consoles with stereo channels, and we will pay more attention to stereo imaging when we are doing our acoustics in future. We have also had some interesting times with the distribution circuits. Dual channel Sound in Syncs has given us some fun, the earliest versions of which were not at all fun when there were vision disturbances. But we cracked the problems and now the dual channel Sound in Syncs is now more robust than the old mono one and even quite iffy vision links will carry it successfully.
“NICAM is brilliant. It produces a quality you couldn’t manage by anything other than a digital system and you have to be listening under severe test conditions to hear any kind of impairment at all to the signal, compared with say a 16 bit linear system. Curiously now, because the developments in digital technology have been so fast in the last few years, it looks rather wasteful, there are much more efficient ways of compressing digital audio signals which make much bigger bit rate reductions, albeit with more obvious artifacts. There are virtually no audio signals that show up NICAM badly but most of the others have a bete noir somewhere and something will show them up”.