mtloriginal,
I generally agree with willand that bookshelf monitors with a good quality sub can equal or likely better the performance of a pair of floorstander speakers, if $$ and quality are equalized.
Acoustical experts have proven that frequencies below about 200 hz interact in any given room very differently than frequencies above 200 hz interact. Low frequency sound waves are much longer than mid-range and treble sound waves. A 20 hz sound wave is about 56ft long while a 20,000 hz sound wave is less than an inch long. Basically the lower the frequency, the longer the corresponding sound wave and the higher the frequency, the shorter the corresponding sound wave.
Because of the above, the room size is also an important factor in how bass sound waves interact within the room and affects how the bass response sounds in that room. Generally, the smaller the room, the more difficult good bass response becomes. This is because the very long deep bass sound waves launched from the sub are likely longer than any room dimension within the room. This means these waves will be forced to continue to bounce off the room boundaries (walls, floors and ceiling) until they run out of energy.
Further complicating the situation, the sub is continually launching additional bass sound waves, of varying frequencies and lengths, into the room. The result is that these long direct and reverberated sound waves inevitably crash into each other, causing something called bass standing waves.
These bass standing waves are audible at the specific room locations they occur as bass peaks (perceived as bass over-emphasis), bass nulls (perceived as bass under-emphasis) and bass cancellations (perceived as a complete absence of bass).
If given a room's dimensions, ceiling height, room boundary materials and location of the low frequency drivers (woofers/subs) within the room, acoustic experts are able to accurately predict and plot the bass response throughout the entire room; including the specific locations at which bass peaks, nulls and cancellations will exist.
If you were to play music with good and repetitive bass content and walk around your room listening for how the bass sounds at various positions within the room, it's obvious exactly where the bass response is good and where bass peaks, nulls and cancellations exist.
The only empirically proven method discovered to date for providing very good bass response that is well dispersed throughout any given room is the use of a Distributed Bass Array (DBA) system.
The DBA system was initially theorized by 2 PHD Acoustical engineers, mainly Dr. Geddes and to a lesser extent Dr. Toole. Through experiments they discovered that the more bass point sources (subs) present in a room of any size, the fewer bass standing waves exist in the room. This means the more subs in a room, the better the bass response and the more evenly it is dispersed throughout the entire room.
Of course, they realized there was a practical limit to the number of subs consumers would find acceptable in their commercial (theaters, clubs and bars) or domestic (residential) rooms. Fortunately and critically, they also discovered that the use of four strategically located subs eliminated the vast majority of standing waves in any given room, with only marginal improvements obtained through additional subs.
This is why most commercially available complete DBA systems, such as the $3,000 Audio Kinesis Debra and Swarm systems, consist of four 4 ohm subs along with a 1,000 watt class A/B amp to power them.
I'm definitely not an acoustical expert. I just learned the above through my extensive internet research in an effort to find a good home bass system solution that would provide very good bass response for both 2 channel music and HT use and integrate well with my Magnepan speakers.
I'm going to end this post here before I write a book. But I'm willing to assist you in finding a good bass solution for your room. It doesn't need to be a $3,000 DBA system since I have some other ideas. Please let me know your room size, budget and whether you'll be using your system for music, HT or both. I'll continue my advise on a future post if you'd like.
Tim
