Yes Listens2 is correct, I should have used the term 'subsonic' in my 2d paragraph but some guy called Nsgarch called it a 'rumble filter', who was I to argue! :-)
FWIW my last unit with a filter called it a 'low' filter. But, a rose with any name still smells......:-)
FWIW my last unit with a filter called it a 'low' filter. But, a rose with any name still smells......:-)