Need replacement woofers for my ProAc Response Twos

Her are the Theil and Small parameters of the driver, copy them and send them to OEM driver manufacturers and ask if they have something very close.
Or go the original $750 ones from Proac, UPS should cover the cost if Millersound backs you.

http://www.scan-speak.dk/datasheet/archive/18w-8543-00.pdf


These could also still be available
http://www.kijiji.it/annunci/audio-tv-e-video/reggio-calabria-annunci-reggio-di-calabria/midwoofer-scanspeak-18w-8543-00/71914811

Cheers George

http://www.speakercity.com/Merchant2/merchant.mvc?Store_Code=SC&Screen=PROD&Product_Code=18W-8543-00

I saw someone post that the woofer was made by Seas. I've owned a few units of this woofer- Proac R2S, R3, R3.5... it's for sure a Scanspeak. I'm not sure if the suspension is absolutely the same, but the standard 18W 8543 was the template driver that Proac used. 
Good luck.

I saw someone post that the woofer was made by Seas.

Yes that was for the Proac Response D 2, a later speaker.
 https://homemedialimited.co.uk/wp-content/uploads/2014/10/proac_responsed2-ebony.jpg

Cheers George