Do you have a sub woofer with flapping distorted bass? Maybe the driver surround has torn with the dreaded foam rot? If so don’t throw it away, replacing the sub woofer speaker drive unit takes less than an hour and revives the deep clear rumble for around £30- £50.

Warning: Never operate you sub-woofer with the amplifier removed – there are exposed mains voltage connectors inside and the amplifier has a heavy transformer that can topple over!

I blame Star Wars Rogue One on the demise of my budget Paradigm PDR10 which I rescued in a previous post. By the end of the movie the woofer sounded awful with a flapping sound at even modest volume. As you can see the fault was the speaker driver where the foam surround had split.

Parading PDR 10 driver surround split

Parading PDR 10 Driver Foam Rot Fault

It’s possible to buy replacement surrounds for a few pounds and re-foam the speaker. But a gentle push on the cone centre revealed a rasp sound as the voice coil touched the magnet. It would be tricky to centre a new surround and the coil may be damaged due to surround failure.

To access the speaker you need to remove the 12 black screws that hold the rear amplifier panel in place – remove power cable first – see warning above. Don’t be tempted to try and take the front grille off as it’s glued in place – all servicing is done via the cutout in the rear. If your sub rattles or vibrates it could be the front panel glue has failed – see previous post detailing a fix for that.

My PDR10 had a 10 inch Paradigm speaker with a label – Made in Canada, Part number B156WPDR1000S. No details on impedance or power handling. So I used a multimeter and found the speaker measured a DC resistance of 3.8 ohms. Choosing a replacement from the myriad of sub-woofers out there was a challenge. I began by looking at car sub woofers as these have 4Ω impedance or 2 + 2Ω. However, most car subs seem to be designed for style and not suitable for front mounting in the PDR10. They also tend to resonate around 35 – 40Hz and have very high power ratings not required for the PDR10 which kicks out 100w.

So in the end I chose an 8 ohm hifi quality Fenton Audio driver that cost just over £30 from Electromarket. (Update: Similar part available under Skytec brand same model number: 902.214 – Product code CCA0138) Being 8Ω it would probably not offer the peak power the 4Ω original but has an extended low frequency response down to 25Hz.

The 10 inch Fenton fits perfectly sharing the same eight fixing holes and surround thickness. It has a slightly larger diameter magnet and similar depth so fits in the enclosure without fowling  the power amplifier. The Fenton’s spade connectors point to the front so it’s easier to connect the lead before installation. Don’t forget to attach the front led connector via the two pin plug to the socket on the amplifier board.

Shows internal view of sub woofer with replacement speaker installed.

Replacement speaker installed.

After re-assembly of the power amplifier panel I tested the sub with a low frequency oscillator to check response which sounded clean down to 20Hz. Reconnected to the Yamaha AV receiver I fired up Rogue One and fast forward to Ch19 Jedha Escape. Ah, that now sounds much better without the flap.  You can feel the deep rumble and the low frequency effects are convincing.

I also tried the sub with a variety of music sources such as Diana Krall’s Love Scenes (DTS) and it sounds good too. Probably should plug in the microphone and re-run auto set up on the Yamaha but as a simple driver swap I can recommend the 8Ω Fenton 10″ to restore a blown sub woofer.

Original drive with foam surround removed – shows cardboard gasket. Needs remaining cardboard and rubber foam scraping from driver before fitting new surround.

PDR10 Sub with surround and gasket removed

PDR10 Sub with surround and gasket removed detail