graham67

Help me fix this flatulent bass driver !

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Hi,

Looking for some help on diagnosing this problem, on a Rogers LS2.

The first few seconds is a subsonic tone then I switch to a frequency sweep.

https://1drv.ms/v/s!AvReE5AaGPrehNNddC_fVKOXgWF0OA

In normal playing it sounds pretty decent and its not immediately apparent something is wrong.

The other speaker doesn't exhibit any of this vibration when playing the same tracks.

I can't detect any obvious air leak around the driver enclosure or cone but that isn't to say there isn't one 😉

Any advice much appreciated. 

Many thanks

Graham

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Sounds like a rubbing / bottoming out voicecoil on my phone, but I can't say I do subsonic sweeps on a phone more than once ever...!

Sent from my BLA-L09 using Tapatalk

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Thanks James.  I can't hear any scraping when I depress the driver so bottoming seems a.likely explanation.  I assume this would only be solved by replacing the rubber surround?

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Hi Graham,
Best wait for those with more experience to help, I'm as much at sea as you are!

Sent from my BLA-L09 using Tapatalk

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Super Wammer
On 13/07/2020 at 21:43, graham67 said:

Thanks James.  I can't hear any scraping when I depress the driver so bottoming seems a.likely explanation.  I assume this would only be solved by replacing the rubber surround?

Depending which way you’re depressing the driver, there is an old trick that might work.  Some drivers sag after many years, due to gravity.  If you remove the four retaining screws and carefully rotate the drive unit by 180 degrees it might just fix it.  It is free too!  

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Do you want to borrow another pair Graham?

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I had some time to experiment, so am now almost positive the rubber surround is, er, rogered.

Compared to the good driver, the noisy driver can be pushed in much easier, can be easily angled off centre to make contact with voice coil and the rubber distorts unevenly, unlike the good driver.

The driver looks like it was made by Kef, the basket and magnet appears very similar to the Falcon b110 reproduction  The rubber looks the same size though I have been informed it is not the same stiffness. So, I think the next step will be to attempt to find a b110 pattern rubber surround with a suitable stiffness.

If that fails, other option is to to try the Falcon b110 drivers in the LS2.

surround pt25 wam.jpg

falcon rogers pt25 wam.jpg

falcon b110 wam.jpg

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Hi Graham 

Use the b110 drivers but make sure you change both.

The Ls2 drivers are based on the b110 but have longer throw to accommodate being in ported cabinets.

Personally I'd switch to Monacor drivers and keep your Falcon b110 drivers as spares for your ls35a 

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Super Wammer

Also the LS2 driver is Polypropylene and the B110 is bextrene. If you have not got this sorted, I think I may have a spare surround for an LS2, let me know.

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Hi Greybird

I'm sure Graham will be over the moon

Top Man:^

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Super Wammer

Found and posted the replacement today :^

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