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That one note bass occurs either in bass reflex speakers and in some acoustic sealed speakers that are under damped(often put into over sized enclosures or into enclosures with no acoustic damping) that causes them to "boom" loudly at resonance frequency.

A speaker has what is known as an open air resonance frequency...the frequency at which the whole speaker literally vibrates(there are more technical things that happen like the speaker hits its maximum resistance at resonance ect, yet at the same time can be most efficient at converting enegy to sound ect)A speaker may have a frequency response that goes below its resonance frequency, often a speaker's "cut off" frequency (the frequency in which response is 3 db below the plotted main curve) can be as many as 5-10 hertz below resonance, though often times it matches.

If you've ever been in a bathroom stall or shower and modulated your voice up or down, while keeping the volume of your voice constant, often times you'll find one note that "sounds'" louder than the rest, that is the idea of resonance...even if you cut voice power to that note, you find that the note seems to "vibrate" while other notes above and below it need more energy and don't vibrate.

Poorly made speakers that rely too much on bass reflex or ported designs to make them sound "bassy" often have this"one note boom" problem. Often its an over sized driver in a smaller box, a small driver in an over-sized box, or no damping material is used. Also the resonance of the speaker rises or falls depending on the volume behind the speaker(giving us what is known as closed box resonance). So what happens is when such speakers hit resonance frequency all that energy unloads through the speaker and port with a characteristic "booming" at frequency. In the best designs at high end esoteric speaker companies, attempts are made to hand match the drivers and tune the ports to optimally minmize the problem. Bose is known for its excellent bass reflex designs(such as the 901 which as I recall uses multple drivers firing backward with dual drivers up front to provide the directional cues and two flared ports firing front ward to keep the ported augmented energy in phase with the mid bass, midrange and treble. An electronic bass enviromental unit is also included...is that your system js1138?)

Some of the best bass reflex box designs try to minimize this booming by the use of designs that spread out the resonance with the use of multiple porting porting with connections between a primary chamber and a secondary chamber both of which resonate at different frequencies(usually an octave apart).This spreads out the resonances and lessens "Boom". Stuffing a box with acoustic material can also improve booming by stifling internal reflections and changing the way the air in the box behaves, creating literally an effect that increases box volume by up to 10 per-cent and therefore lessening the frequency of resonace and increasing the energy needed for things to go "boom"(as long as one doesn't over stuff the box).

Acoustic sealed or acoustic suspension designs are much easier to make and design but they historically are more inefficient than bass reflex as more power is needed to produce usable bass energy from them. How ever newer materials and the advent of cheap beefier powered amplifiers make acoustic suspension speakers a much more attractive option. The mathematics I found to be simpler in designing them as well in that you get good results with drivers that you suspect may differ slightly from their published spects, and they have a much more gradual tail off in frequency bass response. You can more easily design a sharper rise at bass frequencies at cut off and resonance if you like a heavier bass for rock music(design in a "boom" for example). This design aspect is called adjusting the "Q", a simplfied way of describing the bass energy at resonance thru cut off and how the closed box "Q" can be effected by size of box, compliance of speaker, ect. The higher the Q, the more pronounced the bass at closed box resonance thru cut off, the lower the "Q", the smoother the drop off curve and the smoother the bass.

I like a "Q" of around .8 to .9 as I don't like the sound of augmented male voices in my speakers. Lovers of rock music might like "Q's" of around 1.2 to 2... any thing beyond that would cause the bass curve to rise dramatically above the cut off frequency of the driver and resonance frequencies to rise or a very loud "boom" at resonance might occur. Male voices would become overly distorted and the speaker becomes very boxy sounding.

So if you want to stick it to Bose...build your own acoustic suspension designs...I like tubed enclosures for subwoofers as they fit neatly in a corner or on their sides along a wall. I built one for my livingroom. I built an even larger one with a twelve inch driver for my church's sound system(with its own amp) which has a computed frequency of resonance of 35 hz and a cut off of 28 hz.(I used a Q of .8 as I didn't want to offend the old ladies of the church). Yet it will deliver the bass when called for!