These were marketed in
around 1980 by Technics, on the
surface they were just an average
bookshelf speaker but when you
looked closer there was some more
technology in there. They were
marketed as being 'phase linear',
meaning that they were designed so
that the sound coming from both
woofer and tweeter was matched in
phase, the reason the tweeters are
recessed slightly; this is exactly
what you want from sound if you're
using the speaker as a near-field
monitor. Also they had die-cast
aluminium cabinets to cut
resonances. They had a 6.5" woofer
and a 2" horn tweeter, both covered
by metal grilles instead of fabric.
These had been painted over the
years, I was asked to restore them.
The plan was a combination of paint
and polished metal finish and
upgraded internal wiring.
The speakers as I
received them, they looked tidy
but the paint had some damage.
First thing was to strip them
down to components and get the old
paint off, luckily this was fairly
straightforward with a good chemical
stripper, 2 hours later the
aluminium cabinets were bare. The
design was to have the rear parts of
the cabinets finished in anthracite
and the front panels bare aluminium
- it would be virtually impossible
to get a good polished aluminium
finish all over the cabinets and it
wouldn't be durable, lacquer
finishes cloud the metal and damage
easily, bare metal has the best
finish but shows every fingerprint
and mark. The condition of the metal
wasn't as good as I'd hoped, there
were some deep casting and score
marks from the factory hidden under
the paint, I spent a great deal of
time trying to get the fronts to an
acceptable finish with varying
grades of wet and dry sandpaper and
then a machine polisher.
Starting to
refinish the aluminium, even
getting to this point took
time, it's still not a
pretty sight. Afterwards the
aluminium is smoothed with
wet and dry and looks
perfect until first pass of
the polisher shows every
tiny defect again
After sanding and
first pass of machine polisher,
starting to look more like
polished metal
The rear parts of the cabinets
were stripped and then degreased and
coated with etch primer, 2 coats of
metallic anthracite colour (black
covers better than some other
colours, gold would probably take 3
coats upwards) and then 4 coats of
lacquer. Then the paint was wet
'colour sanded' with 2000 grit paper
and machine polished, this part
takes longer than the paint process
itself.
A set of dark chrome floor spikes
were fitted to the base of the
cabinets, spikes are designed to fit
to wooden cabinets so need some
modifications to fit into aluminium.
the holders were bonded into the
drilled cabinets with RTV silicone
and then the spikes screwed in with
O rings attached to keep the boxes
air tight (this is important for the
sake of bass response in a sealed
box design such as this).
The crossovers were rewired with
new Ampohm polypropylene capacitors,
these are far larger than the
originals so the crossovers needed
some reworking. In the ideal world I
would've preferred to build new
crossovers from scratch but it all
went back together quite well.
Original internal bell wiring was
replaced with 2.5mm OFC, the
original screw terminals were
replaced with binding posts.
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The
completed speakers |
