Quote:
Originally Posted by
buckley44 
bob, by looking at my sub graph how can you tell my sub goes down to 25hz,and how can i get it to go lower i should be able to go much lower, i have a paradigm signature series sub.
Look at any of the main speaker charts and focus on the dashed (Target) curve. Find the volume level for the flat part of that curve to the right of the crossover frequencies -- i.e, in the mid-range frequencies.
This is what I've been calling the "basic level" that ARC is targeting for your setup. In your case that's about 73dB. The hump to the left of that is the Room Gain that ARC is trying to preserve for your room.
Now go to the subwoofer chart and focus on the green (Calculated) curve which shows the results ARC thinks it will achieve with your subwoofer. Notice that this curve also has a hump -- rising above the basic target level you found above (again, roughly 73dB for your setup) over a certain span of frequencies.
Look on the left side of that hump and spot the frequency where the green curve drops down below the basic target level. In your case that's around 25hz.
This means you've got sub goodness down to 25Hz. Below that, your sub is dropping off. It isn't a hard cutoff but your sub is producing less and less energy below that frequency. Now this is only a rough measure of what your sub is doing down there, but it is still a good basis for comparison between sub setups.
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Now if you think your sub should do better (i.e., go lower) then look at the red (Measured) curve to see if it gives any clues. In your case you've got a sharp peak just above that frequency (roughly 28Hz) that ARC needs to eliminate. Then things really do drop off a cliff below that. The peak is likely a room resonance -- precisely the sort of thing ARC is designed to fix.
But the sharp drop off below that is likely a limitation of your sub itself.
Some subs have an adjustable "subsonic filter" which limits their low end. This protects the sub against very low frequencies that are often transients which may cause it to bottom out. See if you have one of those on your sub that you can set to a lower frequency. It wouldn't surprise me to learn that your sub has one set to 25Hz at the moment.
Also consider placing your sub closer to a solid wall or corner which will give you additional boost at the lowest frequencies due to "boundary gain" (and might also alter how the sub is coupling to the room and, with luck, reduce that peak at 28Hz before ARC has to deal with it).
But again, if ARC needs to clamp down on the sub to fix unwanted peaks a little higher up, you may not see any improvement in the lowest frequencies.
Finally, consider whether your sub is properly sized for the total cubic feet of air it has to pressurize in your listening room. If a sub is undersized for a room it will show up in the lowest frequencies first since that's where it has to huff the most air to get the same sound pressure level in the room. A sub spec'ed to go down to 16Hz for example, won't actually achieve that if the room is too big for it. Openings to other rooms increase the cubic feet of air volume the sub has to pressurize.
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Any such changes in sub setup or positioning (even inches matter) will mean you have to do a new Measurement pass in ARC.
--Bob
