If you believe in the Philosophy of "Less Is More" then the fewer electronic components in the audio signal path the better. Like the Matrix, no one can accurately describe to you how they sound. You have to hear a pair of SLAB's for yourself to truly understand them. "FREE YOUR MIND" find out what it sounds like to literally "Listen Outside The Box"
SLAB's operate "Full Range" within the low frequency drivers natural frequency range. Starting around 40 Hz and dropping off naturally on their own at around 3,000 Hz. This eliminates problems with volume level & crossover matching commonly associated with conventional powered subs as described below.
SLAB's lay down what I visualize as a coherent "Low Frequency Stage / Foundation". Then visualize your Mains sitting on and playing seamlessly above this "Low Frequency Stage / Foundation" . The coherent nature and accurate reproduction of the lower frequencies is uncanny and can only be equaled by a "Live Performance".
In a typical Powered Subwoofer configuration the Sub has a separate power amplifier, variable crossover circuit and variable volume control. Lets assume for this example the variable crossover circuit is set to 80 Hz. For sake of simplicity we will say the Subwoofer is producing frequencies below 80 Hz and the Mains are producing frequencies above 80 Hz.
My first observation is that Bass in music is not limited to frequencies below 80 Hz . The human brain knows what good Bass sounds like from past listening experience. Bass and Mid-Bass go well up into and beyond the 200 Hz range. So from the start a traditional Sub is only capable of augmenting a very limited range of the Bass frequencies contained in most music.
My second observation is that most of a traditional Subwoofers amplifier power is not that useful in music applications. To properly integrate the Sub, you increase the Sub's variable volume control until it approximately matches that of your mains. Lets say you play an 80 Hz test tone with the Sub powered OFF and record 80 dB from your mains. Then play the 80 Hz tone with the Sub powered ON and mains disconnected, adjust Sub volume to produce 80 dB. Now you have matched the output level of the Sub to your mains. In many cases your Sub's volume control will be at about 30% of maximum.
In the example above you like what you hear but want for more of that "Fat Low End". So you start to increase the Sub's volume control. You find very quickly that instead of sounding BETTER, your brain is saying this does not sound RIGHT. The problem is that as you increase the Sub's volume control you are only increasing the output volume of frequencies 80 Hz and below. The Human Brain however recognizes that Bass in music extends well beyond 200 Hz. Bottom line is as soon as you boost Sub output volume 3-6 dB above that of the mains the Brain senses a disconnect. The music no longer sounds coherent in it's transition from frequencies below 80 Hz to frequencies above 80 Hz.
OK, in the example above your crossover is set at 80 Hz, you like what you hear, you want more of this but as you increase Sub volume further it all starts to go South. Huh, well lets try reducing the crossover setting to 50 Hz. That sounds OK and I can even increase Sub volume from 30% to 40% now. Any more than 40% and things start to go South again. Any of this starting to sound familiar ??? As you set the crossover Lower and Lower the Sub is augmenting Less and Less of the audible frequency range.