This is from a discussion going on over in the PSA speaker thread but since it's dealing with subwoofers I brought it over here because it may be helpful to some guys who are considering adding a 2nd sub to their system.
Originally Posted by SuperFist
Hahaha! I hear ya. Because I love a challenge and I like disciplining myself, it was put to me to resist buying another one and this I shall do. Besides, I would definitely need to upgrade my existing speakers if I got another PSA V1500 or V1801 or more because the LFE would then greatly overpower and drown them out.
Another determining factor for me that I just realized by playing a movie at my -14dB listening level one night and going out in my backyard...
I have 3 full windowed sliding doors that face the backyard and A LOT of bass is getting through them even though they are closed shut. I am positive there will be someone who notices this sound with yet another mind-warping sub added to the mix and the last thing I want to do is irritate my neighbors in any way. But it was a fun ride, guys!
Those are definitely good reasons to resist adding a 2nd PSA sub right now. But allow me to add a couple of reasons why it might be good to do.
1. Usually adding a 2nd sub is more about smoothing out the bass at the MLP and other LPs than it is getting more output. Smoothing is the process of getting rid of peaks and valleys in the bass response. If you sit in a valley than the bass will be anemic in that particular frequency range. If you sit in a null than you will get no bass at at those frequencies. Having two subs can get rid of those pesky issues and two similar subs makes it even easier to achieve this.
2. The result of this is often an improvement in the over all sound quality of the bass in your room. I found the bass to be much fuller and more enveloping with two high quality subs.
3. Of course you will also have greater output abilities by adding a 2nd sub, it just may not be your main goal. But because the actual output is controlled with things like trim settings and the volume control (which we can adjust), adding a 2nd sub will not necessarily result in you irritating your neighbors... unless you want it to... which you don't.
4. With greater output there will be an increase of headroom which means neither sub is working as hard to produce the output you desire. This means you probably won't have to worry about the subs approaching their limits during those hard hitting low frequency effects that we all love so much.
5. You don't need to worry about your speakers being over powered because you have control over the trim level of your subs, so unless you are deliberately turning up your trim (running your subs hot and way above the level set by the room calibration software of your AVR) then everything should still be balanced.
Anyway, there are good reasons NOT to add a 2nd sub right now and good reasons TO add a 2nd sub right now.