Odd subwoofer question.

@jjss49 , Absolutely true (the last paragraph)

I have been living with less than ideal subwoofers since....1978. The benefits have always been worth the problems but accuracy in the lower octaves frequently suffered. I have been using ESLs almost exclusively since then with a 6 year diversion into Apogee Divas. Getting the low bass out of these speakers improves their performance by an order of magnitude. I have been chasing a subwoofer system that matches their accuracy since 1978. At this point in time the only commercial subwoofers I would consider are the Magico Q series and they have two major limitations, size and price. I can do better in DIY terms in both size and price. The last set I constructed are about 80% of the way there. The next set should be state of the art. 

The problem with the vast majority of commercial subwoofers is that they are built to a price and take short cuts to make implementing them easier and less expensive. A good example of this is the use of simple low pass filters instead of  full two way crossovers. There are compromises that they have to use in enclosure construction. Put you hand on your subwoofer while playing. That vibration you feel is distortion. There should not be any, even at the loudest volumes. Most main speakers benefit by having the low bass taken away from them to one degree or another depending on how high up into the midrange their subwoofer goes. The higher the greater is the benefit in terms of lowering distortion and increasing power handling. No subwoofer should be crossed over below 80 Hz. If  a subwoofer can not run up to 80 Hz without a noticeable degradation in sound quality it is a poor design. The best drivers are perfectly capable of running cleaning up to 150 Hz. The problems usually arise with the enclosure, crossover and amplifier. I prefer passive subwoofers because IMHE large class AB and A amplifiers make more dynamic bass than the class D amplifiers used in practically all subwoofers. I find it interesting that many audiophiles are willing to go to great lengths isolating their electronics from vibration but are willing to accept an amplifier in a vibration pressure cooker. The problem with high powered class A and AB amps is that they get hot which is highly problematic inside a subwoofer enclosure. Passive subwoofers allow you to use any amp and a multitude of great crossovers to achieve the best results. You can take any subwoofer and turn it into a passive one by disconnecting the internal electronics which is a viable option for someone who does not have the capability to build his own.

Sub bass is very difficult. It is not just a matter of what you hear. It is more about what you feel. To get the right idea go to a small Jazz club like the Blue Note in NYC. Try to sit dead center of the band. Reproducing this level of sound quality at home is possible but it requires lots of subwoofer, in my case eight 12" drivers, lots of power, each pair gets 2000 watts and digital bass management (crossovers and room control). You have to remove as much bass as you can from the main speakers which will clean them up and increase their headroom by a substantial margin. I cross over at 100 Hz. 

The subwoofers themselves are another world of problems. Keeping the enclosure from resonating is extremely difficult as bass is very powerful. Put your hand on your subwoofer while playing. Feel the vibration? That is resonance and that is distortion. Ideally you would not feel anything other than a cold surface. Building such a subwoofer is very expensive and not viable commercially with only the Magico brave enough to give it a spin with their Q series. Since most of us are not up for spending $40K on a single subwoofer the DIYer is left to his own devices to make it work.  

If you like tight precise bass you are better off without subwoofers unless you have a lot of money to spend. The only commercial subs I have heard that produce "tight, precise bass" are the Magico Q series subs. To do it totally right you need a digital preamp with bass management and room control. I prefer passive subs with out board amplifiers.

I have a Sonos system in my house and have one of their subs in my exercise room. It is not tight and precise but it does add bass to the system and it integrates with their other equipment nicely. It is also big fun to turn the whole house on, sounds like a big venue.