Originally Posted by boobar
So I should be considering 25 x 16 x 7 (2800 cubic feet) as my room size?
You really need to call/email SVS and speak with Ed Mullen or whoever is manning the customer service desk these days.
That is a large space and you should be concentrating on total SPL so ported subwoofers are probably going to make you happier than sealed unless you have $$$ to spend on a huge sealed subwoofer.
IMO what you should be considering in such a space is two PB1000s or PB2000s, unless you have a desire for the following:
Bass to 14Hz that you can actually hear and feel
Bass that rattles your brain and makes your ears bleed
Bass that is technically 'pure' because all the sound comes from a woofer not a port with 360 degrees of phase delay from the woofer, not that you are likely to notice the difference if you already use ported main speakers full range anyway and cannot tell that part of the sound is coming from a port. I cannot really tell the difference myself with competently designed ported speakers.
Two subwoofers accomplish the following:
1) placed within a quarter wavelength of each other (for deep bass that means placed just about anywhere in the room) they combine and couple acoustically with each other to add 3dB of output because of the larger radiating area. The effect is similar to what happens to efficiency with a larger driver of double equivalent area. This table demonstrates the equivalent single driver size of a given dual subwoofer wrt efficiency:
For SVS subwoofers, even the PB1000 will reproduce below 20Hz and two of them are equivalent to a 14" 600W subwoofer in output capability down to about 19Hz. Below that, the highpass will roll off steeply even though boundary reinforcement from walls and floor does help the low frequency extension a little if it is placed in an edge or corner.
2) The biggest advantage of two subwoofers is that the coupling between them also effectively dilutes or eliminates some of the room modes that tend to color the frequency response.
3) Two of them placed either side of the sweet spot also allows a much higher crossover frequency for the center channel to sound 'natural' since the subs create a 'phantom center' effect. Two of them placed at different distances from the sweet spot leads to delay issues that can color the sound but not severely IMO and tweaking the delay setting on the closer sub can help with that a little.
If you are really under a tight budget you should consider buying used. SVS products are robust and if it works when you pay for it chances are good it will continue to work for a long time afterward. You can also buy from SVS 'outlet specials' page and get products with the same minor cosmetic defects yours will have after a year or two of use anyway.
The older discontinued SVS technology is also a great price/performance market. I purchased three used PB10s (equivalent to the PB1000 but with older analog signal processing inside and a slightly larger cabinet) for $270, $270, and $320 from local Craigslist (the third was just last night). These analog subwoofers have nearly identical performance to the newer DSP subwoofers. The biggest disadvantage of the older analog tech is the highpass and limiters are not as good at protecting the driver, so be careful to keep the volume low at the opening of Edge of Tomorrow etc. or risk blowing the drivers with 10Hz high-amplitude square waves.
If you do buy used you will need to check frequently because the deals come and go quickly. Basically to buy a used SVS subwoofer at a decent price you have to be the first or second person responding to the ad and aggressively close on the deal. Same goes for the Outlet Specials on SVS web site, check frequently and when you see what you want, buy it immediately.
If you have an active used market near you, consider it a great place to save money on quality speakers and enjoy whatever system you end up with!