low bass response

thx, again... the basic configuration CANNOT be changed...the cabinet contains all my equipment, except amp, speakers, and shunyata, and 1000+ LPs.....despite what is the "gospel" about things inbetween speakers, my system has wonderful soundstage, including depth....

my question about measuring bass maybe needs to be clearer....of course, the response at listening position is . in the end, what is important, what i wish to understand is . if one plays a 20 Hz test tone and places the db meter just in front of the woofers, should one get a reading, or does one need to be quite a bit further away to get any reading at all?  I guess I am hungup on the "length of such a wave, and where, in relation to such a wave, does one hear, or in this case, feel it?

@jw944ts , if you were to measure your situation, at the listening position you are probably rolling off below 60 Hz. Very few speakers can project bass well below 80 Hz particularly low frequency dynamic impulses. The frequency response quoted by manufacturers is very misleading. You do not sit one meter from your speakers and bass rolls off fast with distance. I use four 12" subs and it still is not enough. I am going to go to eight 12" drivers. In your situation two 12" subwoofers would be the minimum. If used correctly your system will become cleaner at volume and go a lot louder. The two hardest issues to deal with  in HiFi reproduction are bass and imaging. With bass it is important to focus on what you feel, not what you hear. On the bright side it is much easier to remember what you feel than what anything sounds like. I use small jazz venues for comparison.

Try reversing the polarity on 1 speaker, not both.

@jw944ts 

You want to measure from your listening position. Bass response will vary from location to location in your room due to room modes.

If you've tried moving the speakers and/or your listening position and you know your gear's frequency response is flat down to 20 Hz, then you should probably consider adding a sub. 

You don’t need room for bass but you kind of do…, I mean headphones make good low bass with zero distance but you hear the direct wave.  A 20hz wave is 54’ long and will bump into walls, bounce back and cancel itself out. Like two baseballs coming from different directions and hitting each other. 

35hz is 32’ long so the 1/4th wave will be 8’. 1/4th wave matters as because once it bounces off the wall and comes back it is a 1/2 wave and 100% out of phase with the first wave. 
 

That is 8’ from the acoustic center of the 3 woofer and port combined. So your ceiling will be canceling the bass at 9’ but the side and back walls will not be. They all sum together.  Anyway I would just move the speakers around a bit and see what happens. Closer to the walls for more low bass. Same goes for your seat. 
 

In a domestic home I personally think subs with DSP is the only way for flat low bass.