If you want to use Manipulate, you could use something like the following (using ControlType -> None):
Manipulate[
Column[{Dynamic@Plot[Sin[(a^b*x)], {x, 0, 6}],
Dynamic@Plot[Sin[(a*x)], {x, 0, 6}],
Row[{Control[{a, 1, 10, ImageSize -> Tiny}],
Control[{b, 1, 2, ImageSize -> Tiny}]}]}], {{a, 1},
ControlType -> None}, {{b, 1}, ControlType -> None}]
You can also use DynamicModule as well:
DynamicModule[{a, b},
Panel@Column[{Dynamic@Plot[Sin[(a^b*x)], {x, 0, 6}],
Dynamic@Plot[Sin[(a*x)], {x, 0, 6}],
Row[{Control[{a, 1, 10, ImageSize -> Tiny}],
Control[{b, 1, 2, ImageSize -> Tiny}]}]}, Background -> White]]