Quote:
Originally Posted by
Audiolic 
Hi,
Thanks everyone for the comments re. my ARC Graphs. I will post the Targets sometime this week, but I kept the default ARC settings.
With regards to the Sub - I did turn the Frequency Knob at the back up to 180 Hz and I am running the cable from the Sub 1 output at the back of the AVM 50v. The phase is set to 0 at this stage. The sub is however currently positioned next to the wall, approx halfway between the 2 corners. I will take the advice and move it into the corner and use the ARC Quick Measure tool - still need to get familiar with it all. The room is however rather large, I would guess approximately 7m x 9m, so Bob you might be right that I need another / better sub.
Thanks again for the feedback.
The sub works by pressurizing the volume of air in the listening room -- which is why bass seems to come "from everywhere" instead of being localized to the position of the sub. So the height of the room also comes into this, as does whether there are openings to the rest of the house.
Some of the vendors include calculators on their web sites which will suggest what size or number of subs would be appropriate to a given volume of room. As you can imagine, these tend to be conservative as the vendors would greatly appreciate it if you would buy more and bigger subs. But they can give you an idea of how far off you might be in terms of sizing the sub for your room. If the sub is too small for your room, you won't get its rated performance, particularly at the low frequency end. It has to huff a lot of air to pressurize a room a 30Hz and below, and a small sub just won't move that much air.
The basic spec for movie LFE is that the sub has to handle 50-90Hz. That gets you the audible effects bass for things like explosions, but doesn't do anything for the bass that you more feel than hear below 30Hz, and probably isn't doing anything to extend the low frequency end of music for your main speakers either -- typically because subs with limited frequency range *ALSO* aren't particularly "accurate" -- i.e., not musical. The best subs will handle down to 20Hz easily (when properly sized to match the room) and will usually extend down to 15Hz. That last octave -- from 30Hz down to 15Hz -- is the chest thumping bass that people prize. The best subs will do this while maintaining accuracy, so that you can depend upon them for music as well (bass steered to them from the main speaker channels).
The "wavelength" of bass frequencies down there is large -- comparable to room dimensions. That means you get "standing waves" set up in the room according to how the sub's physical placement "couples" the sub to the resonances of the room -- including reflections from walls floor and ceiling. Moving the sub -- even inches matter at these frequencies -- changes how the sub couples and can have a dramatic effect on bass response, particularly as you move the ARC mic (or your head) around the seating area. That's why ARC needs you to space out the mic locations for its Measurements. But if the sub is too small for the room, even the best coupling position won't give you truly good bass response.
--Bob
