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Question: Have you come
across anyone with tips on how to develop the TLS80 - certainly by replacing the
drivers as they grow old, maybe in other ways. They have a wonderful sense of largeness
and bass depth, but I confess the mid range does not now compare with the best of
modern speakers.
Besides doing all the
"standard/simple" tweaks, the biggest weakness of the TLS80, which is common
to most speakers of that era, is the XO. The next big weakness would be too many
tweeters. Then i'd think about replacing the B110.
Fortunately the enclosure
for the B110 is in about the right place unlike the Atkinson TL -- which uses a B110/B139
and even more tweeters -- and it's mid enclosure is too close to the floor.
So in order of execution
this is the approach I would take.
- "Standard/Simple"
tweaks (these are intended as general directions to go as opposed to specific
directions as what to do).
- Better wire.
- Make sure the cabinet
is "tight". This might mean extra bracing (extra bracing has to be
done such that it doesn't use up too much space), caulking, etc. Attention to the
baffle might be particularily effective (ie a 1" x 1/2" strip vertically
on the back of the baffle between the B139 and the rest of the drivers)
In the TLS 80 particular attention should be paid to the mid enclosure. The mid enclosure
is a cardboard tube. Impregnate this inside & out with a liquid stiffening material.
One could use something like West System epoxy but probably most convienient and
way less toxic (ie you could do it in the living room) would be a puzzle-coat like substance. I am using
a brand called MOD PODGE which I find in craft stores. It looks & smells like
runny white wood glue. You apply 3 or 4 coats with an appropriate sized paint brush.
(reports back from England confirm that this makes a substantial difference)
- Duct Seal*.
This is the putty-like stuff pipefitters use to plug holes with. It remains "plastic"
forever (I am recycling stuff I first applied 20 years ago). A layer of this should
get applied to the baskets of the B139 & the B110 to damp out parasitic resonances.
Apply some to the ouside of the mid enclusure as well.
*(or plasticine
or any of many other damping compounds).
<the
above are useful on any speaker>
- Play with the mid-range
enclosure damping. Things like layering from the back a gradation of damping
material to make the mid box more like a TL. dense foam, less dense foam, wool/dacron
mix or fiberglass or miraflex (getting less dense as you get closer to the B110).
A more drastic move would be to extend the entire mid cabinet out the back of the
speaker and leave it open making it into a real TL.
- play with ways of
minimizing the grill cloth holder diffractions. Ideally both the grills
and the aluminum inserts to hold them would go away. If this doesn't meet with SAF
then a new grill with minimal structure offset from the surface of the baffle.
All the above fall into the doesn't cost much, just some elbow grease & ingenuity
required. I have yet to run across a speaker where these tweaks didn't make less
than subtle (usually dramatic) improvements.
The
following are in the class of throw money at the problem, and can make even more
dramatic improvements:
- Tweak the passive
crossover.
- Multi-amp.
This system should be bi-amped at a minimum. And with a fast XO. The B139 has some
nasty resonances that with the 12 dB/octave XO @ 400 Hz decidedly color the mids.
When we were building speakers using the B139/B110 in the late 70s a 200 Hz 18 dB/octave
XO made a huge difference. Nowdays I would use a LinkWitz-Riley 24 dB/octave XO and
tune it to the baffle-step frequency (or a little lower), which in the case of the
TLS 80 should be about 225 -250 Hz (baffle width of 18 inches).
- Replace the 2 Coles
with a single tweeter. Today there are alot of way better tweeters available
than were available when the TLS 80 was built. ScanSpeak, Vifa, Focal, Raven, on
and on. Take a visit to Bob's LDGS
and go shopping. Now the hard part about this is the XO. If you decide to tri-amp
then no problem, it is easier to integrate the tweeter with the B110. If not then
you would have to design an appropriate XO. That is a much bigger challenge. A more
appropriate approach might be to do 6 and 7 together at the same time and use someone
elses already well worked out passive XO.
- Replace the B110*.
If all active XO then just pick a good one. I just signed up to get some Seas MP14RCs
(Tim Garvey chakodile@hotmail.com) that a BASSList member is trying to get enuff
people together for a caselot. There are lots of other good mids. If you decide to
passively XO the mid & top then you should look for an already designed 2-way
minimonitor with a 5" mid/bass and use those for mid/tweeter/XO. The Vifas in
the TLb are a good example (and there is no simpler XO) -- cost of drivers and XO
for both your TLS80s about 125 USD.
* and you could mail
those to me ;^).
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