You should remove it from the subwoofer.

The magnet & coils will muck up the signal propagation and the ability to receive the return signal.

You could invest in some larger WiFi aerials, either unidirectional or omnidirectional.

This link will give you some ideas:

http://www.maplin.co.uk/Search.aspx?...&doy=30m5&SD=Y

Although UK based it will point you in the right direction for what to look for.

HTH

Steve