Given the content of this issue, it's only right that I use this column to stress the importance that enclosures play in the sound quality of our loudspeakers, in both acoustic and mechanical terms. Keith Howard provides a detailed theoretical analysis of the situation on pp10-14. More subjective approaches may be found in Steve Harris' interview with Ole Lund Christiansen (pp35-39), and in my own reviews of the metal-jacket MBA speakers (pp6-7) and the wall-mounted vintage GoodmansTriaxiom driver (p15).
Stan Curtis even touches on the same general subject in his column this month, at least when it deals with the bass end of things. He plans to go for a wooden enclosure, but one that features Briggs' classic sand-filled panels – which may well be the most effective technique for using traditional wood panels. In subsequent correspondence I asked Curtis whether he had thought of wall-mounting, but he replied that the only reason he had abandoned that approach was that he was contemplating moving house!
All of these articles point towards the undesirable role of the enclosure in distorting the sound we hear from the variety of speakers that we use, and one could certainly add the considerable progress that the young US company Magico has made in this matter, to the point where Martin Colloms felt obliged to purchase an example of the S5 that he reviewed for this journal (Vol7 No4) as a reference (as well as a source of considerable pleasure!) I recently spent quite a bit of quality time with another free-space floorstander called a Kaiser Kawero! Classic, which I was reviewing for another magazine. This is a very costly speaker with an enclosure that's fabricated from something called 'panzerholz' (which roughly translates a 'tankwood'), an extraordinary material that might well be considered the ultimate in enhanced wood. It's created by injecting beech ply with resins at high temperature and pressure, and the very dense end result maintains the self-damping advantage of a basically cellular form. Although it wears out tools rapidly, it can be machined accurately, so in several respects it's an ideal enclosure material, and I understand that it's also added to the doors of limousines in order to render them bulletproof. Whatever, it certainly represents a fascinating and very effective alternative to the metalwork favoured by brands like MBA, YG Acoustics and Magico.
All the above use various techniques to remove some or all of the errors of the traditional wooden enclosure. The 'soffit' technique that recording studios have been using to mount their full size monitoring loudspeakers for a number of years also goes at least part of the way down a similar road by effectively eliminating the acoustic effects of positioning loudspeaker enclosures in space.
I guess it was just luck that I was in the position to insert a couple of orifices in the structural wall behind the place where I normally locate loudspeakers. It's a little ironic that the initial stimulus for making these holes was the simultaneous arrival of a number of flush-mount 'wallspeakers' from several brands at the beginning of 1993, most of which were seriously handicapped by inadequate mounting arrangements. By-passing the latter and cutting the baffles needed to mount a 165mm KEF Uni-Q driver rigidly provided the clue that led to using the big Tannoy DCs. That said, twenty two years on I still haven't got around to moving the door to shut the rearward radiation off from the rest of the house.