Low at 40-50hz. Vtf15h mk2

[rman2222]

hi,
Am in the process of setting up two VTF15h mk2s. The only practical placement is in the front corners of a sealed room 14.5 by 16.5 by 8.5 approximately with an alcove about 3.5 ft deep on about half of the back wall (under steps)
Matched the subs to each other and balanced to rest of the speakers using the receiver test tones, using 1 port open, eq1 and q .7. However when using the test cd and the frequency tones it shows very weak in the 40-50hz range (down 6-8db) while strong (matching mains) above and below, all the way down to 16hz. Phase is zero for both and that shows as correct via meter.
Any suggestions for getting a more balanced response?
They look great btw!

Thanks in advance
Joe H