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Discovering The Lowther Acousta
What do I say when a fellow hi-fi enthusiast calls and asks if I know anything about Lowther speakers. He had just picked up a pair of Lowther Acoustas at a garage sale. Being totally unfamiliar with Lowther speakers I called Dan at VALVE who filled me in on the Lowther Voigt article in the Winter 94/95 (this is the current issue/) issue of Sound Practices. (Here's a plug. You guys should all be subscribing to Sound Practices. Besides supporting a truly great magazine, your bucks could go to buy editor Joe Roberts a sorely needed calendar. -- Dan)
I had to see (and hopefully hear) what these obscure English loudspeakers were all about, so I went over to my friend's house for a look. The cabinets were scratched and dented, but still in one piece. The foam surrounds on the drivers had dissolved long ago. The cones had punctures, rips, and creases. The voice coils were distorted and scraping in their gaps. A resistance measurement of 10.5 Ohms indicated that restoration might be possible, if the voice coils were still intact. I left, disappointed that I could not hear them.
Dan referred me to Tony Glynn in Salem Oregon. Tony represents Lowther state-side. After a lengthy and very informative telephone conversation Tony recommended re-coning each driver with a new Lowther cone assembly bolted to the original magnet structure. Tony forwarded helpful information to me regarding the Lowther design and current products available. I now had most all the facts and potential restoration costs at hand. It was decision time. Can the promise of unequaled sound reproduction from a single full-range, horn loaded driver be true? Well, I was hooked and had to find out for myself.
I offered to buy the speakers as-is. With the knowledge that replacement cones were available, I challenged myself to repair the speakers just enough to listen and decide if they were worth further restoration. I removed the drivers from the cabinets and completely disassembled them. They are quite impressive in design and construction. How do they wind that voice coil on the outside and the inside of the former. They also have quite powerful magnets made of huge Alnico chunks that seem to attract any¬ thing ferrous from miles away!
I cleaned the debris from the magnetic gaps with folded paper and masking tape; repaired holes and rips in the cones with Duco cement; trued the voice coils and cone joints with lacquer to stabilize them and eliminate any buzzing; re-glued the triangular foam spiders with contact cement; and installed a. homemade rubber cement coated foam surround. I reassembled the drivers, centering the voice coils in the gap, and tested them by applying a 60 Hz load.
I reinstalled the drivers in the cabinets and started listening for the first time. Very efficient! Somewhat directional, but good imaging. Thin bass response, but able to reproduce robust musical passages. Ignoring the attenuated bass (probably due to my makeshift, somewhat restrictive foam surrounds) the speakers sounded quite good for their condition. I felt there was the potential for even better response, so I ordered on 8" surround repair kit from Parts Ex press. Back to the work bench for new surrounds, realignment of the cones and voice coils, and retesting.
The new half-roll foam surrounds helped increase boss response. Using a test CD in my Phillips CD player directly fed (no preamp) to my Mac 225, the Lowther reproduced frequencies from about 40 Hz out to 15 kHz (my response rolls off there). I estimated that even though they will reproduce down to 40 Hz, a significant roll-off occurs somewhere below 80 Hz. There may also be a slight rise at about 10 kHz. Comparison between tube and solid state-state amplification is quite dramatic when listening to these speakers.
They really reinforced the fact that the tube electronics bring out the tonality, detail, dimension and other goad stuff that solid-state seems to miss. They also bring out the differences between different tube types! After listening to samples of several musical programs I felt the speakers were at their best with strings, piano and voice. Not bad for resurrected 1960's technology.
Now it was time to really get serious: I ordered new cone assemblies from Lowther. They sent new baskets with cone and surround as a complete as¬ assembled unit, ready to bolt on the magnet structure. The voice coils are still double wound, and now have a thin ferrous coating over the wire. When installing the new cone assembly the ferrous coated voice coils are "captured" by the magnet assembly, so centering is tricky. The new cone units are of typical British design, as they are much more difficult to assemble than the original (the bolts are oriented the wrong direction and a few screws must be shortened). After the 60 Hz test it was time to reinstall and listen.
I did one at a time so I could compare the old with the new. Could an efficient speaker be even more efficient and sound even more accurate? Definitely yes!! We quickly changed the other one out so I could listen to both. Now I have a set of spare cones which are a bit less efficient as not as forward sounding.
These are truly fine sounding instruments. The highs are directional, yet imaging is quite good. The phasing "bullet" and "whizzer" cone really do work. The speakers reveal all the detail contained in recordings. They are very forward sounding on complex symphonic material even though bass seems rather thin (more like because the bass sounds thin, I bet-- Dan). I feel they really perform best on quieter chamber orchestra or jazz recordings where individual instruments or voices are featured. These are very "intimate" sounding speakers.
The cabinets need a lot of work, both structural to eliminate vibration, and cosmetic, right down to replacing the wood veneer and vintage grill doth. I will address cabinet restoration in the next issue of VALVE. I should have the cabinets completed by the October VALVE meeting so Dan can power them with his SE amps. I look forward to the audition!
Thanks, Doug for this great resto info. Knowing your abilities as a restorer, I'm sure the cabinets will kick butt. We look forward to your next article (maybe with pictures?)