had an inquiry from our VP of programming concerning his office
speakers. Were they blown? The JBL 4408s were his favorites; was
there anything we could do?
1: Parts are laid out for the start of the big repair.
yes, there was something we could do: Replace them immediately with
perception that the larger speakers would sound better was perhaps
not entirely justified (and they’re hungrier for power now); but it
was an easy “sell” and a quick fix. And I used a Brother P-Touch
labeler to create a position called “11” on his amplifier’s
volume control. Suffice it to say that he was happy to get the larger
speakers to debut new music ads on the station.
back to the troubled 4408s.
they were in our shop, a little investigation revealed their real
problem. The foam component surrounding the epoxy-impregnated speaker
cone was completely rotted and required replacement. What had
contributed to the foam’s early demise? I was unsure; but that
particular speaker sat in direct California sunlight all day long on
a credenza in an office with large windows. Its sister 4408 had been
in a darker area in the PD’s office and showed no signs of early
little Internet research turned up SpeakerWorks.com
a supply house for DIYers that appeared committed to a high level of
customer service, as evidenced by the detailed instructions supplied
with each order. After prowling around the website for about 15
minutes I established that I could repair these woofers myself in our
San Francisco shop for less than $11 per speaker.
ordered the parts recommended for JBL 4408A repair and moved on to
other projects, thinking that it would be a week or so until I’d
see the new surround and gaskets. Before my soldering iron could cool
from another job in the shop the next day, my order had been
delivered via Priority Mail.
2: Removing the old foam surround can be a little intimidating.
the contents of the package onto the bench, I found two new surrounds
and foam gaskets seen in Fig. 1, plus a small amount of the proper
glue, small artistic applicator brushes and thoughtful step-by-step
instructions, including a phone number for assistance if necessary.
disassembled the woofer from the speaker cabinet. The
SpeakerWorks.com instructions told me to remove larger pieces of
surround foam with my fingers, and the rest using isopropyl alcohol
and a cotton-tipped swab to soften the adhesive.
speakers also have a gasket over the top of the old surround, as the
JBL 4408s did; a broad thin flat-blade screw driver was helpful in
prying it away from the speaker frame.
trick is to get the lip of the metal frame as clean and free of the
old adhesive as possible. Use finger-held safety razor blades;
cotton-tipped swabs as applicators to apply isopropyl alcohol to the
old glue; and a 1-inch paint brush to tip the alcohol uniformly into
nooks and crannies of the frame.
enhance your chances of project success by preparing properly and
thoroughly; this job was no different. Done in a well-ventilated and
clean work area, this phase can be performed efficiently in 30 to 45
minutes. At first I worried that I might slice the speaker cone
inadvertently with the razor blade; but as work progressed I
established a systematic and progressive path around the frame,
separating the old foam from the speaker cone.
SpeakerWorks.com is succinct about removing all of the old foam from the speaker
cone, using the razor blade to slice it apart from the paper speaker
cone if necessary. I found that using the 1-inch paint brush as an
applicator for the isopropyl alcohol was helpful.
3: Clean surfaces are ready for test fitting of the new foam
focused on a quarter of the speaker frame at a time, developing
confidence as I went. Working on a quarter at a time is necessary
because the alcohol evaporates quickly, and the foam pulls away more
effectively if it is still damp from the isopropyl application.
SpeakerWorks.com does state, “Rather than putting a lot of effort into removing
the old material from the bottom of the cone in order to provide a
clean gluing surface, you can install the new surround on top of the
next steps were straightforward.
went over the edge of the speaker basket with a paper towel dipped in
rubbing alcohol to remove as much of the loose surround material as
it was the step I’d been waiting for, the test fit of the new
surround before applying glue to any of the surfaces. For the
surround to fit correctly, it must be in contact with the cone. In
this instance I was fortunate. All went well and I determined that I
could move forward with applying the adhesive supplied in the kit.
urges care in centering the surround on the speaker cone during the
test fit. This assures that I would not be guessing about contact
surfaces during the critical next step of applying glue on the
surround and the speaker cone itself.
4: Centering the speaker coil is important prior to gluing the outer
edge of the surround.
glue is white upon application but dries clear. Still, the
instructions recommend that you wipe off any excess. I took their
hint of placing small dense objects around the inside edge of the
cone, and temporarily used some 5/8-inch lag bolts we had in the
drawer to ensure that the glued surfaces remained in contact and set
most critical part of the repair requires centering the voice coil
properly. I practiced by pressing down near the dust cap on both
sides of the speaker cone with equal pressure, making sure the coil
was not scraping or making contact as it moved up and down, which it
must do to operate.
procedure is well described in the instructions, and through practice
I was able to locate the sweet spot to apply glue on the surfaces to
complete attaching the surround to the speaker frame. I again used
the 5/8-inch lag bolts around the circumference of the speaker frame
as pressure clamps to ensure that the mated glued surfaces remained
in contact, and left it overnight to set properly.
this speaker repair required laying in a multi-piece gasket around
the frame edge and gluing into place. It set up quickly within an
hour, then I anxiously carried the speaker cabinet back to the bench
to reinstall the woofer into it.
10 minutes I had an older Crown D-60 amplifier, which I’d recently
repaired, connected and driving test tones from our Audio Precision
wanted to ensure that the speaker moved easily and freely through its
frequency range. I was impressed with the amount of movement the
40-ounce magnet induces into the assembly. The next test was with
Carlos Santana’s“Evil Ways,”which always puts a
smile on my face.
5: The repaired woofer is on the left.
was pleased with how simple this procedural repair was. Now I am
prowling our studios for wayward and tired monitor speakers.
carries speaker coils, frames, transformers and cones should you
decide to be adventurous and try building your own creation. It also
has a selection of repair surrounds and cones.
you feel time management won’t allow you to take on something like
this, but I disagree. After the initial cleanup of the old foam, this
repair took about 15 to 20 minutes per day over about a three-day
an age of slim engineering staffs, we often lose sight of the fact
that there’s still a place for bench work. In fact I find it almost
therapeutic, after hours at a computer working on spreadsheets and
the latest compliance inventories, to do this work. The project
doesn’t require extraordinary tools or knowledge, and
SpeakerWorks.com provides helpful products and support.
is an inexpensive bench repair that will place your prized monitor
speakers back into service quickly and hopefully make you smile too.
Bullett, CPBE, is chief engineer for KITS(FM/HD), KMVQ(FM/HD) and
KZDG(AM) in the San Francisco Bay area. His amateur call is W1AEK.
Contact him at email@example.com.