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Replace Woofer in KRK 10S Sub? Studio Monitors
Old 3rd March 2014
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noka's Avatar

Replace Woofer in KRK 10S Sub?

Hey guys,
I'm pretty much a lurker around here, but hoping someone can help.

I've got a KRK 10S Subwoofer and the unthinkable has happened. I believe I have blown the woofer speaker.

I removed the grill, unscrewed the main front speaker screws, but the speaker itself won't budge. I am hoping it's not glued in.

Does anyone have any experience replacing the woofer in this unit? Any tips or wisdom? I had (wrongfully) assumed this would be simple.

Old 3rd March 2014
Lives for gear

If it is glued in, it wasn't done at the factory - more likely a pliable gasket meant to establish an airtight seal. If you can get access to the rear of the driver, you should be able to press it out - start at one side, rather than trying to pop the entire circumference at once. Otherwise, try an engine valve guage or another very thin bladed tool to try to break the seal from the front side. Depending on the construction, if you're able to loop a piece of stranded wire through one of the screw holes or get a hook under a screw hole at the edge of the frame, it may allow you to pull the woofer free without applying leverage to the baffle.

A less recommended method would be to remove all screws except one at the top and a couple at the bottom - leave the top loose a turn or two, leave the bottoms backed out almost a quarter-inch, making sure you still have a 3 or more turns left before the screw lets loose. Pick the front of the cabinet up slightly, and let it drop...
Old 3rd March 2014
Originally Posted by noka View Post
... I believe I have blown the woofer speaker. ....
Before you go through the trouble of removing the woofer, you should be sure that it's blown. Have you checked the voice-coil with an ohmmeter? (is it open?). Is the voice coil rubbing?

Have you passed a test signal through the amplifier and confirmed that there is output from the amp, but no sound from the woofer? If not, you may be premature in removing the woofer.

If you're absolutely sure that the woofer speaker itself is blown and that amp is OK, then there is no reason the be "gentle" during the removal process. Pry it out, but be careful to protect the cabinet front panel. The old woofer is now trash anyway.

Be sure to get an exact replacement from KRK so you have a driver that is properly matched to the cabinet and the amplifier.
Old 3rd March 2014
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noka's Avatar

Thanks for the responses, ripple_fx1 and Lotus 7 - VERY good input, thanks!

Lotus - to your point, I admittedly don't know much about speaker tech in general. The speaker itself does appear visually intact, but the issue is that when there is sub-bass (I have tested this and isolated it to the sub itself), the speaker emits a rattling mid-frequency sound... as if the paper cone is rubbing against something. The amp/components seem healthy because it still renders a very heavy and loud bass sound - but it has that annoying extra buzz now. If I put my hand on the speaker cone and gently press-in, this strange noise disappears (and it sounds the way it used to sound - nice, clean bass). I've had the sub for about three years and it's never really done this until recently. It's VERY annoying and challenging to mix with it emitting this sound. I had just assumed that the speaker itself was blown. Is there anything else that could be a factor here?
Old 7th March 2014
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noka's Avatar

Still baffled by this... Any monitor/sound/speaker techs care to chime in regarding my previous post? I'm trying to figure out A) How to remove the woofer. B) If the woofer itself is indeed blown or if it's something else going on.

The problem: I'm hearing an annoying and strange mid-higher frequency rattling sound when a decent sub signal is sent to my sub.
Old 8th March 2014
Lives for gear

It's likely you've cooked the glue holding the voice coil winding to its form - it's bubbled, and a bit of the coil has detached from the form and is rubbing in the gap.
If you don't want to pop the amp off the back and push the speaker out (hint, hint), then shock it loose in the manner I've described, or rip the paper from the basket and pull it out by the roots.
Be not baffled - Lotus has given you a troubleshooting checklist, and I've given you removal info that will work if the speaker hasn't been glued in by a foolish previous owner.
Examining it closely and pressing on it gently will not fix it...The sound you've described is well known to monitor/sound/speaker techs, and if you're able to remove the speaker intact, you'll be able to take advantage of the 1% chance that it's not a cooked coil, but something that a recone shop can fix, or perhaps simply re-dressing a wire or something else loose inside your box will cure.
It's all up to you to now, Noka...ready to earn your merit badge?
Old 17th March 2014
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Hey I bought my sub used and it just rumbles now. It may be the same problem your having. Sorry I can't be of any help as I need help myself. Can a shop fix this and if so how much do you guys think this would cost?
Old 21st March 2014
A factory-new replacement woofer for a KRK 10S Sub is KRK Part/Number WOFK10202 and sells for US$56.60 (street price from an authorized dealer).
It comes with a new compressed paper gasket attached.

You can change it yourself. A reputable shop would probably charge 1.5 to 2 hours labor to open up the Sub and replace the driver, and test the Sub. Probably more than a used one is worth.

Remember, an active sub has (2) major parts: The speaker driver itself, and the power amplifier (with crossover). Always check to confirm the power amp is not defective. A speaker driver is very simple electrically, just a strong magnet, some wire and a stiff cone. The amplifier, on the other hand, is much more complicated and includes many more components that can fail.

I'd get (2) so you have a spare ready for the next time it blows.
Old 26th April 2014
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Imza's Avatar

I joined this forum just to post on this thread.
I wanted to elaborate, I just replaced my KRK 10s sub after buying one from Full Compass. I ran into the same "glue" issue, and I decided to do a soft knock on the floor from about 4 inches off the ground...popped right out, no glue. It was just tight in there. New sub sounds good.
Old 27th April 2014
Thanks for your helpful input, and welcome to Gearslutz.

Sometimes a soft knock is called for and this is apparently one of those times. When a soft knock doesn't work, a hard knock is usually worth a try. I find that using some "colorful" language can also often help. If it doesn't cure the problem, at least it makes me feel better.
Old 10th July 2015
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MoseRobert's Avatar

Let the Bass Work

Thanks guys for this info. I couldn't find anything as helpful as this thread for addressing this issue and replacing the woofer anywhere else on the net. Was extremely helpful.

Just wanted to add that I got my woofer out by unscrewing it and then just letting a 4/4 kick drum from a house track knock it out of the case

It wouldn't budge before that, I tried knocking it as suggested - didn't help. I tried prying it out, but without knowing which part of the outer rim comes out and which part stays in (it isn't so clear if you haven't done this before), I was unsuccessful here as well. But after turning up the music quite loud and keeping a close eye on it, it didn't take long for that kick drum to kick it right out without any potential damage (could be helpful to put a cushion or something soft below if you don't want to damage the speaker anymore than it may potentially be damaged).

I think the reason it seems to be glued in is because of the foam parts lining the outer rim. They are glued to the metal rim and it isn't so clear that the metal rim underneath is actually part of the woofer.

Again, cheers and thanks for the expert advice.
Old 10th July 2015
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MoseRobert's Avatar

Easy Fix?

So after taking a closer look at my woofer I am wondering if I can get some expert advice or confirmation on what I am looking at here.

It looks like what was being described above with the coil having come loose? When the bass hits it sounds like paper flapping around so I am guessing this is what I am hearing? It seems like you could easily just throw some glue in between the coil/paper and the bottom part, would this work or is it more complicated than that?

Clearly I have no knowledge of the mechanics of these things, but it is interesting so any advice/knowledge bombs would be greatly appreciated.
Old 11th July 2015
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LeeYoo's Avatar

That's just a loose spider. Nothing to do with the voicecoil itself.
Easilly fixed with a bit of contact glue.
Don't lift up any more of that spider than you have to. You don't want to upset the alignment.
If more has come loose, glue the easy part first. Let it dry. Then do the rest.
Old 11th July 2015
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MoseRobert's Avatar

What kind of glue?

Originally Posted by LeeYoo View Post
Easilly fixed with a bit of contact glue.
Thanks so much for the reply Leo. Not sure what the appropriate glue would be. I have super glue or some PVC cement. Would either of those be appropriate or should I pick up something more specific for this application?
Old 13th July 2015
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LeeYoo's Avatar

NO super glue, NO PVC cement.

Contact adhesive. The brown smelly stuff. Used for e.g. rubber/shoes.

Also known as Ados F2.
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