low bass response

Subwoofer is needed. I have a room just a bit bigger and the same problem. Even though my speakers are rated at 20 - 20k they don't have low bass. One sub was a tease. Two Rel S5 did the job

 Sounds great now.

BTW I tried all the above fixes. They didn't fix the problem.

The frequency of the low E string on a bass guitar is 41Hz. The wavelength would be 837 cm or 8.37 m. You mention that you are listening in the near field. How far back are you sitting? Perhaps there just isn’t enough distance between your speaker and listening chair for that waveform to hit your ear.

I agree with the poster above and try walking around. I found that two Rel T/i5 subs did the trick nicely in my room.

Best of luck!

Nice system BTW.

Like @ozzy62 posted, you need to quantify what you mean by 'low bass response'. To do that, use a test tone to find out the bass extension you're currently getting and how even that response is. I've used the following audio test from Audiocheck in the past - link. Unfortunately, this test leaves out the vinyl playback chain.

You can try adjust the speaker settings / positioning as well as your listening position (if you can). For example, if the speaker sounds too bright, set the treble control to -0.5 dB or -1 dB. Adjust the bass control to 'Normal' if set to 'Contour' or 'Boundary'. Move the speakers closer to the back wall.

As @wlutke mentioned, try walking around the room while the test tone is playing to identify potential listening positions with the level of bass you're seeking.

If none of these seem to work, then it's time to consider adding a subwoofer or two.

I would measure the room. Can just be test tones streamed and a simple DB meter. 
 

The only other thing I would add is distances between the front and side walls. You really need to be below 39” or over 7’ not to cancel out the low bass. This is due to the wave length at 1/4 of its length. Anyway try moving the speakers closer to the back and or side wall (driver less than 39” and less is better to not cancel low bass) and see what happens. Avoid the side wall and back all distances being equal. 
 

The revels have plenty of bass (I am a fan) but it is a little flat in the bass for my tastes. I personally run 2 subs regardless of the chosen speaker. I have yet to hear a speaker where high-passing the first octave (63hz and under) does not improve the sound. 
 

I'd say it's probably the listening position and/ or the speaker positioning within the room that is causing a perceived bass loss at your listening position.  A quick way to find out if this is the case is to simply move your listening chair 1-2 feet forward and backwards from where it is now, in 1-foot increments to see if the bass improves at all.  If so, then you know you're onto something.