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Refoaming square woofers


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#1 Fatdog

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Posted 05 April 2011 - 03:19 PM

This was originally posted by member Prime over at S2G on September 28, 2008. Since a lot of great, older posts seem to disappear over there, I thought I would post it here too.

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A year or two ago I was searching Ebay for boomboxes and came across a box that caught my eye. It was another component box that had large bass vents on the back of the speakers. The speakers themselves were a little unusual because they were flat and square. It was the Pioneer CK-5. I ended up winning it for a song. It was a nice warm day when it arrived so I unpacked it and carried it to the picnic table in the backyard. I ran a cord over, plugged it in and tuned to some hip hop station. I cranked it up a bit and was stunned by the bass output! It was literally vibrating the whole picnic table. This box was delivering bass on a Telefunken Studio 1 level yet it was just half the size of a JVC PC55.

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After about one minute of loud volume the bass was lost and the speakers began rattling violently! The surrounds had failed. The surrounds were initially intact but after my short but loud test drive they crumbled and that was the end... for now. Getting replacement surrounds for these speakers is not possible. So after a lot of thought and some trials and errors, I made my own square surrounds. The process is quite time consuming and tedious but the end result is well worth it. Here's a brief step by step illustration of the refoam process.

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Notice the rotted surround around the white rectangular diaphragm.

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More cracks can be seen from the backside.

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Here's another shot.

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The foam turns into some sticky gunk that sticks to everything. It all has to be scraped off.

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Once the outer edge is clean the inner edge is next.

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After scraping all the residue off, it looks like this.

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Pieces of the old decayed surround.

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The cone tweeter surround is also removed but the chrome ring is saved.

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The diaphragm often becomes convex (curved inward) after the surrounds break down. This has to be fixed since it needs to be flat when we align the voicecoil. I used to get the thing damp, then press it as shown and waitfor it to dry. The lamp speeds the process. I don't do it this way anymore because it sucks. The picture below shows the latest way with carbon fiber strips.

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The carbon fiber strips are placed like a floor joist to prevent the diaphragm from curling. They work great!

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The outer perimeter of the diaphragm is so long that EACH speaker takes TWO surrounds normally meant for a 6.5 inch speaker. These surrounds also work for the Panasonic RX-C100 which was what I initially bought them for.

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You have to do some trimming here and there.

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Then make a clean cut here. Do this to 4 surrounds for a pair of these speakers.

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The outer edge of the surround is glued first at one centimeter intervals. You have to use gel superglue. You must tug and pull as necessary to get itto lay right. This is a very difficult thing to do without ripping the surround.

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Here the outer edge is almost complete.

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The diaphragm is flat on the table while the inner surround edge is glued (Elmer's glue). This step is critical so that the voice coil is aligned correctly.

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Here's one with the outer surround completed.

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Here's a completed set with new tweeter surrounds and chrome rings back in place.


Regarding the Tweeter

It is a whizzer tweeter driven by the woofer voice coil.

The outer edge of the tweeter is isolated from the main backplane via a 4 inch (10 cm) surround. The tweeter moves in cadence with the main diaphragm for low frequencies.

At the other end of the spectrum, the tweeter projects the highs directly from the woofer voice coil without getting dampened by the mass of the main diaphragm.

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The whizzer tweeter uses a 4 inch (10 cm) surround.

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The chrome ring is glued on top of the new surround just as it was originally.



Brett

#2 redbenjoe

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Posted 05 April 2011 - 03:32 PM

thanks a lot fatdog -
for capturing important old s2g posts

#3 oldskool69

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Posted 05 April 2011 - 05:46 PM

And if you look at the old s2g posts you will notice....those in the pics are the one which reside in my house! :-D Prime did a fantastic job of repairing these for me. Mine were the first he did the carbon fiber strips on because the corners had started to curl and he wanted them to remain straight. I cannot thank Brett enough. :thumbsup: :thumbsup: :thumbsup:

#4 Gluecifer

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Posted 05 April 2011 - 06:26 PM

My Pioneer still needs this doing to her, I think I'll tackle it soon after this inspirational reminder.
Thanks Bobby!



Rock On.

#5 Lasonic TRC-920

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Posted 05 April 2011 - 07:11 PM

Wow, that is wild! Allot of work went into those speakers. Nice....Real Nice! :yes:

#6 sony_apm_fan

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Posted 05 April 2011 - 07:19 PM

Thanks Fatdog, this is great. Awesome! :thumbsup:

#7 neko

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Posted 06 April 2011 - 01:06 PM

Hmm, that lookd hard. Good work :thumbsup:

#8 mellymelsr

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Posted 06 April 2011 - 05:20 PM

That is some great repair work...great post!!

#9 oldskool69

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Posted 06 April 2011 - 06:32 PM

As a rcipient of the treatment for my CK-5F, I cannot begin to tell all of how much it's worth it to restore original speakers unless you can find an EXACT match. Which in these cases doesn't happen. Worth the effort guys. Worth the effort. :thumbsup:

#10 rngo219

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Posted 22 March 2012 - 06:27 PM

great write up!

#11 JustCruisin

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Posted 27 March 2012 - 09:05 PM

Question: Where do I get those replacement surrounds? I need to repair my Pioneer square woofers I just got yesterday.. :sad:
Much like the original poster I was impressed at the thump they put out and how much air they were moving, even with bass only turned up halfway!
I was bench testing them hooked up to my Realistic SCR-8, going through songs on my MP3 player.. They handled slammin Ice Cube tracks no problem, Electro songs, pop tracks on the radio, it was playing great continuously for over a half hour!
It wasn't until my favorite Borgore track was playing that the surrounds tore away instantly.. I guess I didn't learn my lesson, because I had fried a previous set of home speakers with the same song! :angry:
These are the square speakers, they don't look this nice anymore... :sadno:
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#12 typing3892

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Posted 19 April 2012 - 02:06 PM

you know you used a round speaker foam for the square speaker does it work good because i have a pair of sony Apm 10es old speakers and they have a square woofer but the foaming around has rot so i was wondering if it would work if i repaired them the same way you did ?

#13 JVC Floyd

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Posted 19 April 2012 - 02:13 PM

you know you used a round speaker foam for the square speaker does it work good because i have a pair of sony Apm 10es old speakers and they have a square woofer but the foaming around has rot so i was wondering if it would work if i repaired them the same way you did ?



you can buy replacement foams for certain apm models on ebay . they are not cheap and the dude that sells them is in russia.

http://www.ebay.com/... ... 4340.l2562

#14 typing3892

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Posted 20 April 2012 - 11:35 AM

yh thanks for the link but your right they are a bit too much i could use the idea of using circle foams and probably make a tutorial

#15 wills15

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Posted 20 April 2012 - 07:02 PM

My old work sold them: http://www.speakerbits.com, we had quite a range.

For members in Melbourne I might still be able to get discounts...

#16 mnt

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Posted 05 December 2013 - 04:44 AM

you can buy replacement foams for certain apm models on ebay . they are not cheap and the dude that sells them is in russia.

http://www.ebay.com/... ... 4340.l2562

I bought one of these sets, for my sony fh :-)



#17 Otari

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Posted 02 September 2018 - 04:43 PM

I have a National RX-CW200 with square speakers which need re-foaming. I may have to look at this solution unless anyone knows if

replacement surrounds can be obtained for this size speaker?



#18 caution

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Posted 03 September 2018 - 12:04 AM

Since square refoam kits are rare, you could try some for other models (like these) and adjust them to fit like this.



#19 docs

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Posted 03 September 2018 - 12:42 AM

An ebay seller in Russia has them, I was looking for some too.

#20 bibox

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Posted 27 April 2019 - 12:09 PM

This was originally posted by member Prime over at S2G on September 28, 2008. Since a lot of great, older posts seem to disappear over there, I thought I would post it here too.

 

 

I am glad this one was saved. I've refoamed many woofers (home stereo speakers) over the years but never attempted a square one.

 

Picked up a set of Sony car speakers in small cabinets last year and this gives me some hope I might be able to bring them back to life.