there's just no way on earth a 6.5" or even an 8" woofer would be able reach 20hz, let alone 10hz. not at the listening position and not at the spl levels required at that position. it's just physic-ally impossible.
unless it's 1" from your ears. but that's just stupid, putting the drivers that close to your ears during playback. but some people doesn't seem to mind.

there's a reason some drivers are called subwoofers, and some are labelled as MID-woofers. because they're just that, an intermediate from the midrange to the woofers.
a 6.5" or 8" might play 20hz, or even 10hz if you put the mic close enough to the drivers. i reckon even a 4" driver will play 5hz if you put the mic 0.5mm from the cone. but assuming they will do 120db surges 3 meters away at the LP is just plain stupid.

henceforth,

assuming this nearfield measurement of a whatever speaker will be similar to the measured response at the LP is just plain ridiculous. even though it says the speaker will do 20hz.

this:

turned to this:


this:

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this:

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this:

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construction is underway (refer the build thread) but considering it's right smack in the middle of monsoon season things keep getting delayed. i've repaired the access road 3 times now since the rainy season started.
the rain soaked, soft soil just can't take heavy machinery running across them. you could literally see the soil bucking under the weight.