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Subwoofer driver failure

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IainStinson

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Subwoofer driver failure

PostTue Feb 16, 2021 7:04 am

I recently notice a few rather nasty notes on my 18 year old subwoofer. This is what I found.
Image
I was surprised it didn’t sound worse.

I’m thinking of using a repair kit to try and restore the driver. Any advice appreciated.

Iain
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mdyde

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 7:32 am

[Topic moved here.]
Best regards, Martin.
Hauptwerk software designer/developer, Milan Digital Audio.
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BarryG

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 10:13 am

Hi Iain,
FWIW, I successfully repaired several old speakers in similar condition a few years ago. Was pleasantly surprised that it was relatively easy to do. You just need to find the right-sized repair kit. Certainly worth a try!
Barry
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engrssc

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 10:50 am

Reasonable carefulness is called for.

Thorough cleaning of both the cone and the frame is important, the old surround can usually be rubbed off. Then spread an an even bead of glue all around the edge. Some advise applying the glue to the frame. I apply a minimum amount (evenly) to both the cone and the frame. Tap it down all around.

Most repair kits come with (just barely enough) glue so keep that in mind. As a backup source, I've used Elmer's (construction) glue. Not too much either. After the glue is applied and the cone is centered (you can gently press on it as it really self centers), I use the old fashioned wood clothes pins (in the USA - available at Home Depot) around the perimeter to hold the cone in place until the glue dries (like several hours, I do overnight). After the glue has dried, you can press (gently) again on the cone to verify that the voice coil is not rubbing.

Rgds,
Ed
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rayjcar

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 11:29 am

I had very good success putting new foam surrounds on four Rodgers 12" woofers. Speakersworks.com on their web site shows you how to measure the surround dimensions accurately. You need to measure the inside and outside diameter of the surround, and the outside diameter of the speaker cone. I found a perfect fit, even though it was for a brand I didn't recognize.
https://www.speakerworks.com/foam-surro ... g-s/63.htm
They list special sizes for subwoofers which have large rolls for extra travel.

Alternatively, you can try Simply Speakers which lists a plethora of brand-specific kits.
https://www.simplyspeakers.com/speaker- ... -kits.html

As Ed mentioned, careful gluing is the key. Do not try to glue both the inner and outer parts of the new surround at the same time. I found that the latex-type glue takes a long time to set on the frame. I believe I glued the surround to the frame first. You may have to press down around the circumference repeatedly for a half hour while the glue sets up, until the surround remains in place without lifting. As per Ed, the cone does self-centre, so once the surround is glued to the frame and has set overnight, you can apply the glue to the edge which attaches to the cone, and it will set very quickly.

Also key to a good job is careful removal of the old surround, Peel it away very carefully from the cone. Tease the inner edge, and then pull gently. If necessary use a razor knife on the speaker frame if the foam bits won't come off.

Ray
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rayjcar

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 11:32 am

As a follow-up, I see that Blue Aran has many brand-specific kits as well, and they are situated in the UK.
http://www.bluearan.co.uk/recone/

Ray
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larason2

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 1:12 pm

I used the kits from parts express. They come with plenty of glue, and were easy to install. It’s not too important to remove all the old glue, just make sure there are no bits of foam left in it. I used a hobby knife to scrape the old foam off. If after the first pass it’s not perfectly glued, you can add a second coat. Just be careful not to tear the paper of the cone! I glued the inner seal first, then the outer seal. Make sure you use the driver spacers to ensure the surrounds don’t pull the edges of the cone into the driver.
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engrssc

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 2:14 pm

larason2 wrote:It’s not too important to remove all the old glue, just make sure there are no bits of foam left in it. I used a hobby knife to scrape the old foam off. If after the first pass it’s not perfectly glued, you can add a second coat


I've found it best to clean off the old glue because on the subs I have, the design (called air suspension) relies on an air tight seal between the speaker and the speaker case/housing. The entrapped air acts to stiffen the speaker's cone. Could be other designs are less critical in this regard.

You can literally feel the air being pushed by these subs when they are fed very low tones. If the air tight seal is not maintained, the low frequency response is effected substantially. Those very low tones rely on moving air which you may not hear but definitely can feel. These subs are driven by a 1200 watt power amp. Without that entrapped air (spring) and that kind of power, I would imagine the cones could be overextended and destroyed.

Rgds,
Ed
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IainStinson

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Re: Subwoofer driver failure

PostTue Feb 16, 2021 7:35 pm

Thank you for the very helpful information.

The sub is a Paradigm PS-1000 which was made in Canada (but bought in the UK from a popular budget HiFi shop). I have ordered a repair kit, which is correctly sized for the PS-1000, from Simply Speakers in Florida (via their UK eBay portal). It will take a couple of weeks to arrive in the UK. (The UK company Ray mentioned did not have the appropriately sized kit.)

Iain
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IainStinson

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Re: Subwoofer driver failure

PostSat Feb 27, 2021 2:01 pm

Repair kit arrived on 23 Feb (from USA to UK). Well packed and it was the correct fit for the blown sub. Installed following their advice and videos (and comments) above. Sub now sounding fine.
Iain

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