Your sub experience: Easy or hard?

Much easier with two than with only one, and also much more noticeable sonic improvement with two.  I would like to try three or four.

Good information Eric, but my desire to change the sub's output level is solely related to low level listening, where I enjoy a little more kick - sort of like the loudness controls we used to have on our receivers back in the day.

I have decided to try the Marchand balanced, second-order, passive, high pass filter at 40 Hz, under the premise that any detriment to the signal above 50Hz will be offset by the benefit of not having my main amps/speakers trying to reproduce those lower frequencies.  Marchand claims a S/N ratio "much better than 110 dB", so worth a try. fixed at

I have just this week been looking at some changes to my sub situation. My main speakers with two 9-inch drivers each in a very inert acoustic suspension cabinet perform very well with bass down to around 40Hz. I have been very happy with the sound resulting from rolling in two subs and cutting them off at around 40 Hz.

In discussions with the manufacturer of my speakers, he believes what I am doing is fine, but that I could gain improvements with a high pass filter set for 45 Hz, which could reduce doppler distortions resulting from the woofers reproducing lower midrange frequencies up to 360 Hz while at the same time trying to reproduce very low frequencies in the 30-45 Hz range. Marchand is in the process of building a passive balanced HP filter for me.

It is also my speaker/sub manufacturer's experience that two subs run in stereo (which is how I use mine) are superior to one mono, or running two in mono. He believes we can localize stereo sounds in the low bass to some extent making it worthwhile to run the subs in stereo. Regarding more than two subs, it is his experience that adding a third sub run in mono and located in the back of the room can provide significant improvements in bass, while going from three to four subs is much less of an improvement. He recommends adjusting phase using a trial and error method from the listening position. I have been planning to add a third sub but haven’t yet found one of the SW-12s that I use anywhere close to where I am located.