Ex HiFi repair engineer, advice given

update

well the airtight no longer hums (well it does but you have to be within a couple of feet to hear it so quiet enough

autotransformer now hums away in its place so looks like I have to go to the trouble of installing it in the electrics cupboard and running a wire though to the lounge to supply my 220v

thanks for the tips - now to wondering if it has improved degraded or not affected the sound and mild concerns about house fire as it runs a bit warm (given its a 15 KVA one I thought it would take a pre and power amp in its stride)

rgds
darren

 

Re the big Kef with oval drivers, those old Kef speakers used a B139 bass driver. There was also a passive unit known as an Auxiliary Bass Driver (ABR) which was effectively a 139 with the motor removed and was driven by pressure changes within the sealed cabinet.

What you have might look something like this classic Kef 104ab:

 

Nice one Darren.

I wouldn't worry about the warm running - any transformer has certain minimum magnetisation loss depending on the winding design, and that could be quite normally 10-150W on a thing that size (15KVA). Enough to make it run warm, but entirely safe - it'd probably be 60-80degC or more at rated load.

 

Having done the humming transformer thing to death Fox's advice in this thread is spot on.

I had a couple of dimmers in my house that will make ANY transformer hum. The transformer is where the problem trail ends but it's highly likely not the cause. Especially if other's aren't humming !