Dropped speaker advice needed
ju...@halfmagic.com
I love my son dearly, but this morning his exuberant 5 1/2 year old play
succeeded in knocking over one of the speaker stands. My AudioMaster LS3/5a
speaker crashed to the hardwood floor. The thing's built like a rock. It
looked fine externally. It didn't sound so fine when I reattached the leads.
Scratch, scratch, scratch. It sounds like the station's tuned perfectly on
the undropped side, and tuned just a bit to one side on the other. I did not
injure my son, though I may have spoken a bit severely....
I pried the front cover off and found a pretty normal-looking setup -- I
didn't SEE any problems. So what's likely to be wrong with these? Did the
fall jar one of those heavy magnets loose, or is it more likely that the
staticy sound comes from wiring problems? (I think I know what I WANT the
answer to be!)
I would rather fix these than replace them, since I like the sound. What do
we think these 17-year-old speakers are worth?
How should I proceed?
Thanks for your help,
Howard Hansen
howard@halfmagic**NOSPAM**.com
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Richard D Pierce
In article <6hdd9u$9mc$1...@nnrp1.dejanews.com>, <ju...@halfmagic.com> wrote:
>I love my son dearly, but this morning his exuberant 5 1/2 year old play
>succeeded in knocking over one of the speaker stands. My AudioMaster LS3/5a
>speaker crashed to the hardwood floor. The thing's built like a rock. It
>looked fine externally. It didn't sound so fine when I reattached the leads.
>
>Scratch, scratch, scratch. It sounds like the station's tuned perfectly on
>the undropped side, and tuned just a bit to one side on the other. I did not
>injure my son, though I may have spoken a bit severely....
>
>I pried the front cover off and found a pretty normal-looking setup -- I
>didn't SEE any problems. So what's likely to be wrong with these? Did the
>fall jar one of those heavy magnets loose, or is it more likely that the
>staticy sound comes from wiring problems? (I think I know what I WANT the
>answer to be!)
You'll probably have to wish VERY hard, because the problem is VERY
unlikely to be a simple, easy-to-fix problem like wiring.
Your symptoms are completely consistant, regretably, with a misaligned
voice coil/magnet assembly. If they are real LS3/5A's, the woofer is a
KEF-B110, which is a fairly large magnet on a stamped steel chassis. A
fall could easily have bent the chassis enough (and it realy doesn't take
very much) to misalign the voice coil quite permanently. I have also seen
examples where the staking points (early B-110's used screws to attach the
magnet and basket, later ones may use staking pins) were slightly deformed
or even torn enough for the magnet to shift.
Sorry to say, but it's likely your worst fears have been realized. In all
likelihood, the ONLY effective repair is to replace the woofer outright.
The tweeter is probably okay, since its magnet is smaller and more
securily attached.
Despite the claims of some LS3/5A manufacturers and proponents, a stock
B-110 IS the standard replacement part, and you could probably find one
at one of the distributors in this country (try Madisound?) for not a huge
amount of money.
--
+---- Dick Pierce ---------------------------------------------+
| Professional Audio Product Development |
| Transducer Design and Measurement |
+---- (781) 826-4953 (Voice and FAX) DPi...@world.std.com -----+
Daniel J. Marshall
I think I would remove the speaker, noting the orientation of the fall
and see whether there is any visual indication of a bent frame.
Also, sometimes a magnet assembly can slip out of radial alignment, but
I am not familair with the construction of that particular speaker, so
don't know whether this could happen to it or not. I have seen an Altec
421A which had slipped out of radial alignment, no doubt from being
dropped.
If it is a bent speaker basket, as Dick suggests, I would first check it
for dragging by gently and evenly grasping the cone on ether side
between thumbs and forefingers and gently moving the cone in and out to
confirm whether it is dragging. Or, if convenient, just drive it to a
reasonable excursion with a low frequency sine wave.
If you have access from the back side, you might want to try something
as simple as driving it at a low frequency where the drag becomes
audible and then tweak on the magnet in different directions noting
whether you can affect the amount of the drag. I have one speaker with
a cast frame that will drag, or not drag, depending on where on the
frame edge it is picked up, or how the mounting screws are torked down.
If it is a bent frame and the bend is slight you might even get away
with something as bone-head simple as adding a wedge of some sort in the
enclosure to apply pressure on the magnet assy in the proper direction.
That is sort of a far out speculation, but stranger things have
happened. You will need to first assess what actually happened and the
the severity of it to be able to come up with the best fix.
If it is dragging, and it is visually apparent that the frame is bent, I
would securely clamp it down by the frame edges face-down to a sturdy
surface, say like a table saw or a drill press table, or the like, using
the mounting bolts and perhaps some additional C clamps, etc., and, by
some convenient means means attach a sturdy lever, say like a 2 by 6 (or
whatever suitable material available), then have a go at torking it back
into alignment. Perhaps a hole in a 2x6 or 2x8 the size of the magnet
would work, depending on the speaker construction. You might tork the
magnet assembly entirely off, yet OTOH, you might luck out and tweak it
sufficiently back into alignment that it wll work OK. And, if it indeed
is bent, you would have little to lose. Your odds of success may not be
high, but you will never know until you try it. I have lucked out
occasionally on similar things. Try torking a little and noting whether
there is improvement. Repeat the drag test between torking sessions,
being careful, a little at a time. You might be advised to try tweaking
the basket legs while applying pressure from the lever, maybe with a
crescent wrench or other suitable device, as appropriate. I would not
throw up my hands and quit until I had given it the old college try.
Additionally, if you can clamp the frame such that there is an opening
below it, you can carefully apply a low frequency sinewave during the
torking session and note the effect from applying a gentle force in
various directions until you find the precise direction that minimizes
the drag, then continue to tork in that direction. Anyway, Good luck.
If you are not a tweeking kind of guy, or do not have suitable
fixturing, send it my way and I will have a go at it, best efforts only
of course, with no guarantees, you pay shipping both ways. I have a fair
assortment of shop equipment and a considerable amount of ingenuity for
such hare-brained ideas.
Dan Marshall
Howard Hansen
Sadly, I think you're exactly right. On the advice of another fine netizen,
I carefully pushed the woofer in and out and it definitely makes a rubbing
noise (unlike its undropped twin). I opened the thing up and found it to be
nicely constructed and visibly undamaged.
The woofer had a KEF sticker saying "MO 880", another that said "SP1003", a
more understandable one announcing its impedance as 8 ohms, and finally a
small sticker on the magnet with the letter "W". I only include this
information because I expected to see B-110 or some such. I also seem to
recall seeing people selling LS3/5a's that were 15 or even 11 ohms.
I'm sorely tempted to take a hammer to the magnet and see if I can't align
it that way, but I think I'll demur! On these 18-year-old speakers, should
I replace the woofers in both speakers, or just the one? And probably more
to the point, what do you expect this thing to cost me? And can any old
hack with a screwdriver and a soldering iron (I think I still have one in
the basement!) do the replacement?
Thanks for your sage wisdom (and quck response).
Howard "Just wants his old sound back" Hansen
Richard D Pierce wrote in message ...
Richard D Pierce
In article <6hdtum$ovh$1...@brokaw.wa.com>,
Howard Hansen <ju...@halfmagic.com> wrote:
>Sadly, I think you're exactly right. On the advice of another fine netizen,
>I carefully pushed the woofer in and out and it definitely makes a rubbing
>noise (unlike its undropped twin). I opened the thing up and found it to be
>nicely constructed and visibly undamaged.
>
>The woofer had a KEF sticker saying "MO 880", another that said "SP1003", a
>more understandable one announcing its impedance as 8 ohms, and finally a
>small sticker on the magnet with the letter "W". I only include this
>information because I expected to see B-110 or some such. I also seem to
>recall seeing people selling LS3/5a's that were 15 or even 11 ohms.
The designation "SP1003: indicates that it is, in fact, a B110 SP1003, the
stock, off-the-shelf unit. Other variants are things like SP1057 and so
on with different voice coils, cone profiles, and so on.
But definitely, a B110 SP1003 is precicely what you want.
>I'm sorely tempted to take a hammer to the magnet and see if I can't align
>it that way, but I think I'll demur!
The most likely result is that you will crack or shatter the magnet.
>On these 18-year-old speakers, should
>I replace the woofers in both speakers, or just the one?
You'd probably do fine just replacing one. The construction and materials
used in this driver lead to pretty good unit-to-unit consistancy and good
long-term stability.
> And probably more
>to the point, what do you expect this thing to cost me?
Haven't looked lately, but $50 and up would not be unheard of.
>And can any old
>hack with a screwdriver and a soldering iron (I think I still have one in
>the basement!) do the replacement?
Any old hack that can make a good solder joint can do it, sure.