The built-in speaker simulation is an integral part of the CLASSIC series circuits. Each model is tuned to match the speakers/cabinets of this amp. It is designed for a smooth, consistent response would be achieved by a multi-miked box, without the peaks, valleys and notches associated with single micing. The shape of the speaker curve will not adversely affect or interfere with it Frequency response of your own box. There is no need to bypass the speaker simulation circuitry when using it with a guitar amp. The speaker simulation works in tandem with the EQ controls to customize the overall sound.