Long throw 5 1/4 woofer??

I use a pair of very dynamic Silverline Preludes (latest model) with two amazing 3.75" (I measured 'em) aluminum/magnesium woofers per speaker, and they sound great...I use a good sub but still, they somehow kick it. I informally (I may have been wearing shorts) measured them with a test CD and they woof down to the upper to mid 40s or so (hype/specs notwithstanding). Gigantic double magnets on each woofer, and although I haven't actually measured the "excursion", excurse they do!

Excursion might move some air but getting anywhere near limits is guaranteed distortion. Makes it seem to sound louder though.

These days, companies use the term "long throw" for anything over 5mm one way. Typical cheap woofers will have Xmax of 3mm, even less. But it's not like 5mm is gargantuan or even uncommon. Most decent woofers available from SEAS, Peerless, Scanspeak, SB Acoustics, have Xmax values of at least 5mm on their drivers of that size.
http://www.madisoundspeakerstore.com/approx-5-woofers/sb-acoustics-sb15mfc30-4-5-poly-cone-woofer/
It's great that small drivers can deliver decent bass levels and makes small monitors attractive, especially for someone who doesn't require concert level SPLs. But attempting to get 100dB at 40Hz from a single 5" woofer is just begging for massive amounts of distortion. High levels of bass energy are best left to drivers designed to produce it.

3/8" (roughly 9.5 mm) is indeed impressive x-max for a 5 1/2" midwoofer. It is harder to build that much excursion into a small-diameter suspension system than into a large-diameter one. In general there's a tradeoff relationship between long excursion and good top-end extension, but sometimes a dedicated designer can find a way to meet seemingly conflicting goals.

Duke
dealer/manufacturer/no affiliation with Totem