The Spendor BC1 was designed in the late 1960s by Spencer Hughes who worked at the BBC. Along with co-designer Dudley Harwood, they used Bextrene (originally used for making egg cartons) which, when covered in gunk, became suitable for making loudspeaker diaphragms. The resulting 3-way design used an 8 inch Bextrene mid-bass driver, a Celestion tweeter and a Coles supertweeter. The drive units are mounted in a thin-walled reflex enclosure and at the time gave impressive stereo imaging and detail, sounding smooth, clear and with low distortion.
The BC1 was part of the system I assembled of the ‘best’ Hi-Fi available in 1973. I was one of the first British Hi-Fi dealers to be allowed to sell it (I remember that Spendor took some persuading to allow non-professional studio users to buy them in the very early days). This was the system that so disappointed me for its lack of musicality, it was just so boringly ‘Hi-Fi’. I now know how to overcome this limitation with all parts of that system (and any other).
The main problem with the BC1 is the rather complex crossover network. The efforts to deliver consistency and response ‘accuracy’ make it low on efficiency and limits dynamic range, softening bass and making the treble rather ‘hard’ in character.
My answer is in two steps.
The conventional approach – Type A – is to upgrade crossover components, rewire with Kimber 4TC speaker cable, remove the foam rubber sheets that line the inside of the cabinet and replace it with Acousti-Wool. The result is a very big step towards giving the sound more life and dynamics and tightening the bass.
The more unconventional solution – Type B – is to remove the crossover completely, wire the mid/bass direct to the input, then feed the treble with a 2uF Kimber Kap and the Supertweeter with a 0.33uF Kimber Kap. The result of this is revelatory. You usefully gain around 6dBs in sensitivity, a sweeter, clearer treble and a tight, clean and deep bass. The music becomes truly involving, detailed and dynamic, yet still smooth and ‘tidy’. And it plays rock and roll! Interestingly, the frequency response graphs are very similar and the modified one is arguably flatter. I have applied this solution to dozens of speakers now and had very consistent results. Interestingly, much of the ‘characteristic’ distortion I associate with dome tweeters turned out to be an artefact of the crossover networks used; specifically the use of inductors.
If you have a pair of BC1s and want to have a more modern, expressive and involving experience with your music, give Type B upgrade a go; you can easily put the old crossover back if you don’t like it. I think you will fall in love with them all over again.
Fact file
Date launched: 1969
Date discontinued: 1994
Type: 3 way
Sensitivity: 84dB / 1W / 1m
Nominal impedance: 8 O
Frequency response: 50Hz – 15kHz
later to 45kHz – 25kHz
Power handling: 20W RMS later 55W
Weight: 14Kg
Dimensions: 635mm x 300mm x 300mm HWD
Please note: The Torlyte Speaker stands shown, are not included as part of the upgrade.
