Is it the sub or the crossover?

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A while ago, i got a bunch of audio stuff from my dad.
2 1.7 cu ft 2-way speakerboxes
2 home receivers
4 bookshelf speakers
2 satellite speakers
I basically set it up so that.
1 receiver powers the bookshelfs and satellites
and the other powers just the subs (tweeters disconnected)
All this is hooked up to my comp.

Recently I replaced 2 12" woofers that I had in 2 1.7 cu. ft boxes (which I ported to 40hz) hooked up to a stereo home receiver with a five band equalizer, with only the 50hz eq up and everything else down.

The reason why i replaced them is 1)i had no idea what the specs on them were, (they were some oem kenwood home woofers) and 2) they didn't go low enough.

I had replaced them with some oem jbl woofers
(JBL 12gg01).

Immediately, upon replacement i had noticed 2 things..the bass response was MUCH deeper, but all high bass that the old kenwood woofer had good response for was missing with the JBL's.

here are the specs i gathered on the woofer:

jbl 12" subwoofer
neoprene surround
2" kapton 4 layer voice coil
40 oz ceramic magnet.

Le(mh) 3.44
Qm 8.14
Qe 0.331
QT 0.318
BL(Tm) 15.18
EBP 75.00
EFF(%) 1.92
SPL(db) 91.00

after gathering the specs i then proceeded in lowering the box tuning frequency to 31 hz, this helped smooth out the peakiness that i also had

Basically, my prob is this. When i try to run frequency tests from 120hz - 27hz.. basically.. i notice that the sound output is quiet down to around 60 hz and then just gets louder and louder from then on. till around 28hz

basically the question im asking what could be causing my problem.. the sub only reponds to low bass frequencies..i miss having high bass..
First question, when you say that everything but the 50Hz slider is down, what's down? Set flat at 0dB or all the way at the bottom? It really sounds like you're listening to the effects of the equalizer about 60Hz, and then you're hearing the effects of the box below that point. (According to winISD, the box has a -3dB point of about 42Hz)

As an experiment, what happens if you bring the next slider over up as well? Does this seem to bring up the top end? If so, then its your equalizer. Personally, instead of the equalizer, try a low-pass filter, that's what you really want anyway. (Unless of course your just using the equalizer to figure out what frequency you want to cross over at)

By the way, subs are supposed to only work on low bass, 120Hz is pretty high for a sub.
3 or 4 " port

the dimensions im gonna be using only have a 10.5 inch depth....

my choices so far (cause i dunno how to implement a square port..) are to either use a 3 inch pvc port with a length around 4 inches..

or a 4 inch pvc port with a length around 8 inches (using a pvc elbow at the end, cause 8 inches straight is too long)

im thinking of just using a 3 inch port for simplicity..

my question is:
will i get too much port noise with a 3 inch port?
if so, should i use the 4 inch pvc port with the elbow instead?
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