sry for the bad image paint job but here you go. (Note there are no other speaker area's/holes on the device front of back same as the HD7)
Also side note that nearly no mobile device has "surround sound" Since the speakers cant physically surround you. The HTC 7 Surround has more speakers then normal (one possibly 2 under the speaker area on the back and 2 or more where the slide out speakers are) This is what makes the device special. The Dolby Mobile is to enhance the sounds in the built in speakers and HEADPHONES which can now have base and surround sound built in around your ears.