The BenQ HT1075 has a single 10 watt speaker. It happens to be located on the right hand side (if you are facing the front of the projector). What's impressive is that it throws a good deal of sound. Certainly there's plenty to fill my 400+ home theater, and there was plenty last week in my front yard, watching some 30 Rock on a warm "summer" night.
Now that I have commended the projector for having significant volume to carry a good sized room, let's talk about sound quality.
There's plenty of mid-range, and not a lot of real high end, so it sounds reasonably balanced, not tinny.
That's a good thing, of course. What the HT1075 does not have, however, is any serious bass.
OK, it's fine for watching the average movie, but when it comes time to "rock the house" you just can't expect a projector that's a lot smaller than a small subwoofer, to produce real bass whether Lord of the Rings, or Transformers, or any action flick for that matter.
The good news is that there is an audio out, so you can feed the sound (if it's coming from an MHL device) to an external speaker system. If your source material is coming from cable/satellite, or DVD/Blu-ray, then you can run audio directly from your source to your AV receiver to "rock that house."
One disappointment, as with many home entertainment projectors, although there is that audio out, it disables the internal speaker. Too bad, otherwise, you could buy a small, inexpensive powered subwoofer, to add the bass the internal speaker lacks. It really is a shame, and I've complained every time a manufacturer auto disables the speaker when plugging something into the output.