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Lowthers & DiatonesJohn Rivers I was most interested to come across your web page today. I have been interested in the topic of single driver speakers for some time and I would like to offer you some observations on this complex topic. First some background. I built my first 2A3 push pull amp in 1988. Soon afterwards I decided to build a single ended 2A3 amp. I had been researching the early amplifier designs for the movie theatres and slowly working my way backwards through the Radiotron Designer's Handbook (I had one of the earlier editions). I asked Sowter's if they could supply a suitable transformer for a single ended amplifier. At first they refused but when I persisted they took the problem to Dr G Sowter and he obliged, although they insisted that the design was difficult and impractical and the transformer would only be supplied as an "experimental" device. I believe that these were the first single ended transformers to be made by Sowter's for audio use for many years, or perhaps the first ever, since they started up around 1937 when push pull was the rage. I still have their initial letter in which they politely refused the commission. I still have these transformers and they work rather well. I wonder how many single ended transformers they have made since then? A single ended low power amplifier needs an efficient single driver speaker. At the time that I built the 2A3 amplifiers Lowther's seem to have been going through a bad patch and communication with them was very difficult. I bought my first Lowther's from Audio Innovations who seemed to have been their export agents. Over the next few years I bought six pairs of Lowther drivers and built about five pairs of cabinets. I began with TQWTs, a version of the Decca corner speaker and some Lowther designs. I never did get around to building the TP1 or Audiovector enclosures. I used Lowther's for about six years. I liked Lowthers for about 4 of those years. What do I like about Lowthers? They are dynamic. They have presence and a vivid quality. I liked using them in the upward firing position. Yes, there is a great deal to be said for the Voigt "open-window" effect. Yes there is much to be said for re-visiting some of the 1950's designs and re-exploring the virtues of "lossy", light cabinets and other peculiarities. Lowther speakers do some things very well that other speakers don't do at all. They produce a vivid and lively sound. What Lowthers don't seem to be able to do is produce a smooth and even sound. Firstly, they are light in the bass. It's an interesting fact that many people who take up Lowthers will tell you that at first they thought they were light in the bass but after a while they realised that the bass was there after all. Actually it isn't there, it's just that their ears have made a psychological compensation for its lowered level. Secondly, the bass shows persistent notch filter, raggedness, lumpiness, or what have you effects. The most difficult of these to adjust to over the long time are the notches, the absences. Thirdly, Lowther speakers have some shouty, screamy effects in the upper registers. All these things show up over the long term in the music. But it depends what kind of music. If it's rock music or orchestral music you may not notice the effects at all, or when you do you may ascribe it to the colorations of particular instruments, recording timbre, etc. You will, however, eventually come to notice these effects if you listen to a lot of piano music and the human voice, especially opera. The unevenness will be quite clear if you listen to a piano playing a descending scale for example. You will find some strange breakups in tenor voices. You will find a nasal scream in a soprano note. Worse, you will come to know exactly what note to expect these effects on. You will start to avoid playing discs that do these things. You will realise that you are choosing the music to suit the system. This will send you scurrying away to build a better set of enclosures, or to re-arrange the stuffing in the enclosures that you are using. Or you may decide to give up Lowthers. Which I did. What do I use now? For the last year I have used Diatone speakers. I purchased them from EIFL in Japan. I built the reflex enclosure following the design that was enclosed with the speakers. They work extremely well. I think they are better than Lowthers. Why? They sound a lot more smooth and even. The bass is there, they have good presence and a wide and spacious sound stage. They don't seem to be less dynamic than the Lowthers. You rate them as 90dB efficient. The curve supplied rates them as 92 plus dB efficient. I think in the enclosure they sound about 94dB (I notice somebody else rates them at about this figure). Whatever, they sound more than adequately loud. To run them I use a selection of amplifiers including home-built 2A3 single ended amplifiers (with the original Sowter transformers), home-built single ended WE310A/WE300B amplifiers (again with Sowter transformers) and a Consonance amplifier. This latter is a very interesting Chinese hi-fi amplifier, it uses a 6DJ8, 12BH7 driver and parallel SE pairs of 300Bs. It is an integrated amplifier and it is "family-friendly" with a nice soft start. It delivers about 14 -18 watts per channel, is built to a high quality and can be purchased directly from the manufacturers for a very good price. The sound is excellent, almost equal to the WE310A/WE300B amplifier. The source I use is a Pioneer DVD 24/96 player. The nice thing about the Diatones is that I like them, without feeling that I have made some kind of ideological commitment to them. I don't choose to play music because it sounds good through them. I play discs I avoided with the Lowthers. There is an appealing simplicity to the cabinet design. I have examined the photos of the double cabinet design that you list. The inner cabinet looks to be about the same dimensions as the cabinet I use, except made with thinner walls (i.e. a "lossy" design) and placed with a larger enclosure to attenuate vibration transmission. The arrangement looks to me like a version of a "studio monitor" type design, probably made for the Nippon Broadcasting originally. I probably won't build a version of this double cabinet. I see a lot of woodwork for an imperceptible gain. I could wax on a lot more about the Lowthers, especially the double cone and the mechanical crossover and its effects, which are usually ignored by the enthusiasts. I have heard and listened closely to a number of variants on Lowther themes, including back loaded Fostexs and the Lothx. This latter is a very praiseworthy attempt to deal with some of the Lowther problems. Some Lowther drivers I bought in the early 90s were very badly made; the Litz wires broke, cones became unglued and foam turned to dust (I don't believe these problems affect current production). As a Lowther enthusiast I persisted, and accepted things that I would not have tolerated from some, more commercial, product. The Lothx speakers use a different cone, phase plug, foam surround and (I believe) spider with the original Alnico magnet and cast chassis. The horn design is more refined. But still, at the end of the day, there are some things about Lowthers that I think just don't sound right. I think you are correct in pointing out the basic problem of designing and constructing a horn to a good standard - too many bends, too many flat sides, too many compromises, not to speak of integration of the registers when you have done all this. I hope you find these notes useful. I have no interest in hi-fi controversies, but I do have quite a lot of experience with Lowthers and I have been reading quite a lot about them lately. But I find that there is a critical and evaluative gap in the comments made by enthusiasts who have just built their first pair and what I have to say is intended to try and fill that. Please feel free to add this letter to your useful site. Cheers, John Rivers P.S. To add perspective to all this: my speaker using experience includes original QUAD ESLs, home built ESLs (but one day I will build a pair following the Leak push-pull idea), LS 3/5As, Linn Kairns, Gales, WE 555 electromagnetic horns, JBL's and some early Jordans, not to mention sundry others which are best left nameless. Top
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