The benefit of 4 ohm variant over 8 ohm variant of the same cab is only apparent when the amp can not drive the 8 ohm load adequately.
If one only looks at the rating (watt @ 8 ohm) on the back of the amp and the cab and try to match those number, it would seems most amp does not have enough power at first.
However, the numbers on the back of a cab is merely a thermal rating, which in 99% of bass cab is much higher than the displacement limit in the bass guitar frequency region.
Now, if one also takes into consideration that the power handling of a bass cab is almost always limited by displacement rather than thermal, then those head/cab matching at 8 ohm now seems to make more sense.
If one only looks at the rating (watt @ 8 ohm) on the back of the amp and the cab and try to match those number, it would seems most amp does not have enough power at first.
However, the numbers on the back of a cab is merely a thermal rating, which in 99% of bass cab is much higher than the displacement limit in the bass guitar frequency region.
Now, if one also takes into consideration that the power handling of a bass cab is almost always limited by displacement rather than thermal, then those head/cab matching at 8 ohm now seems to make more sense.
