Tell your friend that his sub box if it is divided in two separate compartments should yield decent output. But, if they are not, it is strongly recommended not to this as it may damage the Boston Acoustic. If the sub is divided, as I said it is ok, but the Pyramid being of cheaper quality could color your sound and produce less than clean Bass. (Mind you this is for the person with an incedible ear, as Bass for most people is quite universal.