What's a watt? Yes, I know that sounds like one of our thoroughly daft headlines, but haven't you ever found yourself confronted with two ostensibly identically rated combos with one sounding maybe twice as loud as the other? It happens to us all the time and it seems to be getting increasingly hard to make any sense at all out of manufacturers' quoted output figures, which are nearly always given as watts RMS.

That RMS business relates to what, in technical terms, means root/mean/square, a measurement of the average power delivered by an amp's power amp stage to the speakers. But what about speaker efficiency? As more and more players desert stacks in favour of combos, the whole question of speaker efficiency becomes increasingly important.

Pump 100 watts into a 12" speaker of limited efficiency and the actual sound pressure level that you hear will be held-back by the speaker in question, especially compared with an identical power amp stage delivering its load into a similarly sized loudspeaker of greater efficiency.

This has more actual bearing on the perceived volume of an amp than possibly any other factor and that, let me say, begs the considerably more complex question of the way in which perceived volume fluctuates as a result of such esoteric technical parameters as speaker loading, damping factors and cabinet design.

Accordingly a rating in watts can become relatively meaningless when the actual sound pressure levels of a combo are measured. Isn't it about time then, that we stopped talking about 100 watt combos and quoted the actual sound pressure level measured at one metre per watt of input — one standard parameter of most sensible tests of decent studio monitors and speakers?

One thing we've found is that substituting some original speakers for more up-market types can produce a tremendous effect on both the perceived volume of the combos/amps in question and the quality of the sound itself.In some cases this can result in a negative effect (believe it or not). A cheap speaker may 'break-up' the sound for distortion purposes better than a high quality one but (especially for uses in Bass, PA and Keyboards) this isn't really the point.

We'd suggest a rating as a measured figure of maximum output measured at 1 metre from the cabinet and quoted in decibels. It would, admittedly, be a figure regardless of the amount of distortion in the sound and that would continue to be very much a subjective judgement of whether one actually liked the sound of that distortion or not — but it would, if nothing else, be a more relevant figure than a statement of output from the power amp stage in watts alone, which is what we have at present.

If any makers disagree with this we'd like to hear from them. But, and we are looking into this right now, if something isn't done to separate one 100 watt combo from another we might have to start making our own measurements of output power in terms of measured decibels. We'd appreciate any comments from makers on that subject.

Anyway, it's time to shut-up now and let you get on with this month's issue of MUSIC U.K. We've the usual blend of news, new products reviews and interviews, plus a feature about buying secondhand gear safely. Please don't forget, we really do appreciate any readers' letters and enquiries, so if you have a point to make or a question to ask, please drop us a line.

In the meantime, here's wishing you a superb 1983, and all the good luck in the World. Finally, here's a thought for the New Year — tell a musician friend about MUSIC U.K. — and we'll arrange for a visit from the MUSIC U.K. Good Luck Fairy — now (while we strap the gossamer wings on our advertisement manager and sprinkle her hair with a dubious looking glitter mixture) let's get on with the show!