Is it OK to connect a BH or RH amp to a single cab rated 250 watts and 8 ohms? Would the amp not overpower the speakers ??
Yes it is OK to connect a single cab to an RH or BH amp - for the following reason:
1. At 8 Ohm load (connection of a single cab) , the power is lower than for 4 Ohm. See the power rating chart:
TCE Power rating and Active Power
2. There is usually less risk to damage a speaker with an amplifier that can supply more power than the specs of the cab, compared to the opposite situation:
An amp with plenty of power has a lot of headroom and can drive the cab without any problem. Of course you will still need to use your common sense (and your ears) and will set the volume level to a point the cab can handle it. A power amp that is underrated for the cab, will have difficulties to drive it, and will end up distorting. This could in fact be more damageable for the cab speakers.
You can use a single RS112 with a RH450, RH750, BH500 and even a Blacksmith. Keep the volume at a reasonable level and nothing will be damaged.