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As I said on the other website, a little 6.5" or 8" woofer is too small to produce the very low frequencies (down to 20Hz to 25Hz) of a sub-woofer.
You posted the spec's of a little 6.5" woofer that makes boom-boom sounds at 200Hz. I have 6.5" woofers that are flat down to 52Hz. With some bass-boost they go down to about 35Hz.
Didn't you see the fairly inexpensive 10" REAL sub-woofer with good spec's and enclosure designs that I posted?
He is not on another website. He has TWO threads about this little woofer here and the first thread is: https://www.edaboard.com/threads/301456/
The cheap little woofer that has a peak in its output at 200Hz and a resonance of 52Hz is linked in post #16 on the other thread.
There is NO WAY the cheap little woofer can sound like a REAL sub-woofer.
If the dimensions are huge then the little 6.5" woofer will go down to about 50Hz in the type of ported enclosure in your photo. Then one entire octave of sub-woofer sounds will be missing.
The enclosure in post #5 has such a tiny sealed box (0.3 cubic feet) at the rear of the speaker that it will have a peak at about 120Hz then roll off at lower frequencies. No bass.