Originally Posted by Kain
Sorry for the noob question but what is the purpose of having a dedicated external subwoofer DSP or EQ? How is it different compared to simply connecting the subwoofer(s) to your A/V processor and having it apply the EQ?
Other posters have answered your question really well but I thought I'd relay my own experience. Maybe it will add some context...
I have a Yamaha AVR that does a good job of room correction above sub frequencies but nothing below 70 hz IIRC. I considered multiple subs, different placements, a new AVR etc. before finally settling on the following path:
1) starting with one SUB (PB1000) and experimenting with placement. I was going to go with a higher end sub but figured I'd eventually add a 2nd PB1000.
2) adding a DSP if necessary (my AVR is perfect absent the sub eq)
3) adding a second SUB if necessary
I found that my single sub located in the corner had plenty of output for my needs but something just did not sound right. I found some bass sweeps and realized that modes at 40 hz & 80hz were really pronounced. The AVR may have also been setting the sub too low due to the modes resulting in too little output below 30Hz while other frequencies still remained exaggerated. Moving the one sub around did not really help matters much so I returned it to the front left corner.
I added an 8033 cinema anti-mode and all my issues were solved. The 8033 fixed the peaks and the sub ended up being set a couple notches higher such that output below 30hz was more than I'd ever really need. My only complaint is that the secondary listening position (which is a couch on the right side of the room that is against the wall) has a bit too much bass. The MLP and just about anywhere else is great. A second sub would likely balance things out better but at the cost of aesthetics, and another $500.
I agree with everyone that says 2 or 3 or 4 properly integrated subs will sound better than fewer subs and that the law of diminishing returns is also a factor.
In my room, a modest sub "corner loaded", with an external EQ works great. I fully expected to have to purchase a second sub but I don't see a need to now.
If I'm you I'm starting with 2 better subs and equalization vs. 3 or 4 lessor subs (assuming budget is a concern)