Wayne Parham Messages: 18789 Registered: January 2001
Illuminati (33rd Degree)
I doubt the use of a 4Ω or 8Ω speaker will damage the amplifier in your intercom, so I'd just replace the 16Ω unit with another speaker that would physically fit. I woudn't bother with adding a series resistor, because I don't think the additional current will hurt the amp. If it has a volume control, then just don't turn it all the way up and you'll be fine.