Question on small bass drivers in tower speakers


I noticed that many speaker manufacturers have been offering tower speakers with a multiple array of smaller bass drivers in their latest designs. I understand that having a series of smaller bass drivers in a cabinet can provide very fast and accurate bass response but I often wonder how these smaller drivers fair when it comes to reproducing the lower registers of the frequency range at louder volume levels (95+db).

I've seen claims of bass response down to the low 20hz range using two 6.5" woofers from some manufacturers like Proac as an example.

My question is this, how can these small drivers be capable of reproducing such low frequency when stuffed into a box when if you look at the manufacturer website of the speaker drivers themselves and see a listed Frequency response that shows the woofer only being able to play down to 40hz at best when taking a speaker of no more then 7" in diameter into consideration?

If someone was in the market for an almost "Full Range" speaker how likely are they to be happy with a tower that only uses 6.5-7" drivers at most that claim low 20hz capabilities verses some other manufacturer who uses 8" or larger drivers with similar advertised capabilities?

Even if I take into consideration the most inert cabinet designs available for these small drivers I still find it difficult to grasp the idea that they will be able to play bass that low on the scale with any real authority.

Please add your thoughts and experiences with small driver tower speakers and if you were impressed or disappointed with their capabilities of playing low and loud despite the advertised claims ..Thanks
eniac26
My Focal 836v speakers have an array of three 6-1/2 inch bass drivers and they often surprise me with their bass. I actually have a subwoofer, but I don't use it often for stereo listening, it's reserved for home theater. I have my speakers fairly close to the wall which increases the bass, but there are some songs that if I had the room I'd move them out from the wall and reduce the bass slightly. They don't handle "low rider" bass with authority so they have their limits, but I certainly consider them full range.
A couple of the parameters of bass production are volume displacement of the driver and the air volume of the enclosure, plus, if ported, port length/diameter. Porting helps "stretch" the bass extension of smaller drivers. More smaller drivers may equal the surface area of a single larger driver, but one needs to consider the total air volume displacement. Smaller drivers usually have shorter throws and thus less volume displacement. It takes even greater numbers of smaller drivers to make up for the shorter throws. The enclosure's air volume is important too. As the number of drivers are increased, the enclosure size needs to increase. Without the larger air volume behind the drivers, the compliance goes down, the resonance frequency goes up, and the bass production suffers. Also consider what the specs are not telling you, i.e., the SPL at the claimed frequency range. They could very well produce 25 Hz, but only at 85 dB—output may not increase proportionally with power input or the distortion may increase dramatically—that's not impressive.
A compromise in design for increased sales, hi WAF ,less shipping, construction, packing,and material costs for manufacturer, distributor. Lastly the multiple smaller woofers are needed to approach the bass of a proper sized transducer. Which they do not really do.
Agree with Johnk - it is entirely WAF cosmetic, cost and footprint driven.

There is NOTHING true about the MYTH "can provide very fast and accurate bass response"

Most of these woofers use voice coils that are no bigger than a tweeter!!!!!

There is a place for small woofers - small near-fields.
Well designed small woofers like the 3.75" magnesium/aluminum ones in my Silverline Preludes (second/current series woofers with slightly larger woofers than the original series) can sound amazing...d'Appolito amundo! Proper porting/box loading and crossover design are the key...with great (and I mean GREAT) midrange being the primary benefit with fast bass that almost goes as low as advertised. Might have something to do with the huge double woofer magnets and long throw of the woofers. I recommend a small decent sub (I use an old REL Q150E) with any small woofed drivers and you get the best of both worlds.