Bass shakers not working

Hi All,

Sorry not very tech savvy but have had a go installing 2 dayton bass shakers, they work when used as speakers through Youtube and seem to work when coinnected to the LFE in iRacing but I can't get them to vibrate in Simhub. In the output selection screen I have engine vibration turned up and I can see the two blue bars flickering like the engine is running when I'm sat in the pits but the shakers do nothing.

Any clues?

Thanks