Trcns First I'm not into HT. But I can answer your first 2 questions.
1) The Sub peaks out at 25hz but is not cut off completely. Like the speakers are not cut off at 34hz they are still going to 27hz but at a lower loudness. And the sub is still adding above 25hz again at a lower loudness. You want to find the crossover point where the 2 blend together.
That brings up phasing/timing. If the sub is 180 degrees out of phase with the mains you will get very deep bass but a huge suck out at the lowest the mains can do because the low frequency waves are cancelling each other. Don't rely on the sub phase adjustment to get them to be in sync. You may need to move the sub a bit closer or farther to achieve that. Again you don't want the bass from the sub either leading or lagging the bass from the mains. IMO that's the hardest adjustment.
2) Yes it will but minor. I didn't believe that until I got a demo with Dyn C4's and a Rel B1 playing a track of Diana Krall. Her voice sounded much richer and fuller with the sub. What was interesting it wasn't that way with all tracks. When I asked why it wasn't the same with all tracks he told me he couldn't explain it. But when he was trained by Rel to be a dealer they suggested that track to use as a selling point (BTW I don't remember the track or cd) .
Hope that helps
1) The Sub peaks out at 25hz but is not cut off completely. Like the speakers are not cut off at 34hz they are still going to 27hz but at a lower loudness. And the sub is still adding above 25hz again at a lower loudness. You want to find the crossover point where the 2 blend together.
That brings up phasing/timing. If the sub is 180 degrees out of phase with the mains you will get very deep bass but a huge suck out at the lowest the mains can do because the low frequency waves are cancelling each other. Don't rely on the sub phase adjustment to get them to be in sync. You may need to move the sub a bit closer or farther to achieve that. Again you don't want the bass from the sub either leading or lagging the bass from the mains. IMO that's the hardest adjustment.
2) Yes it will but minor. I didn't believe that until I got a demo with Dyn C4's and a Rel B1 playing a track of Diana Krall. Her voice sounded much richer and fuller with the sub. What was interesting it wasn't that way with all tracks. When I asked why it wasn't the same with all tracks he told me he couldn't explain it. But when he was trained by Rel to be a dealer they suggested that track to use as a selling point (BTW I don't remember the track or cd) .
Hope that helps