Looking at the manual, it appears that there is only one output tap, which is stated to be optimized for 5 ohms, consistent with the comment by Rrog.
My GUESS is that using a 16 ohm speaker on an output tap that is optimized to work into a 5 ohm load does not represent a disparity that is large enough to cause amplifier damage, that can result from "inductive kickback" if a reasonable load is not connected to a tube amp that has an output transformer.
However, Hifitime and Ghostrider are correct that power output will be reduced. The amount of reduction will depend on the feedback setting you use and your choice of UL or triode mode (since both of those things affect the amplifier's output impedance), and the impedance of the speaker. On a percentage basis, the worst case reduction will probably occur where output impedance is lowest, which in this case is 1.28 ohms occurring for the maximum feedback and triode mode settings. According to my calculations the corresponding reduction into a 16 ohm load may be as much as approximately 3.75 db. That represents a loss of more than half of the amp's power capability, compared to a 5 ohm load driven with those settings.
Sonics may also be adversely affected by the mismatched loading of both the output transformer and the output tubes. Ringing may occur in the transformer, at least to a small degree, and the distortion performance of the output tubes may not be optimal.
As has been said above, high speaker impedances can certainly be advantageous, but not if the impedance is severely mismatched to what the amplifier is designed to drive.
All of that said, though, touching base with Manley as suggested earlier would certainly seem to be in order.
Regards,
-- Al
My GUESS is that using a 16 ohm speaker on an output tap that is optimized to work into a 5 ohm load does not represent a disparity that is large enough to cause amplifier damage, that can result from "inductive kickback" if a reasonable load is not connected to a tube amp that has an output transformer.
However, Hifitime and Ghostrider are correct that power output will be reduced. The amount of reduction will depend on the feedback setting you use and your choice of UL or triode mode (since both of those things affect the amplifier's output impedance), and the impedance of the speaker. On a percentage basis, the worst case reduction will probably occur where output impedance is lowest, which in this case is 1.28 ohms occurring for the maximum feedback and triode mode settings. According to my calculations the corresponding reduction into a 16 ohm load may be as much as approximately 3.75 db. That represents a loss of more than half of the amp's power capability, compared to a 5 ohm load driven with those settings.
Sonics may also be adversely affected by the mismatched loading of both the output transformer and the output tubes. Ringing may occur in the transformer, at least to a small degree, and the distortion performance of the output tubes may not be optimal.
As has been said above, high speaker impedances can certainly be advantageous, but not if the impedance is severely mismatched to what the amplifier is designed to drive.
All of that said, though, touching base with Manley as suggested earlier would certainly seem to be in order.
Regards,
-- Al