Digital Room Correction vs Room Treatments

@captouch oh then I guess you gotta use the best fit that gives the least dip in the below 60Hz region. I thought it was just the front wall bare behind your speakers

@captouch, yes I'm talking about bass traps which because of the long wavelengths involved need to be large. Mine run floor to ceiling and are 3ft. across the width. It's a standard 600mm x 1200mm x 50mm rockwool or glassfibre board cut in half = 2 off 600mm x600mm squares then cut across the diagonal. If you are handy these things are simple to build inexpensively especially if you have demolishers nearby. I have picked up a truckload for 20% normal price and even some for free. Google DIY superchunk bass traps. These are to be placed in corners, any corners where walls meet including the floor/wall and ceiling/wall corners but is usefull just about anywhere. I helped a friend with a difficult room that had a deep recess that was used as an office and tunk receptacle which housed the vacuum cleaner, some suitcases and kids toys including bikes. I suggested filling with rockwool and made a framed rattan panel which looked very smart. A ceiling cloud acts as broad-band absorption and is useful down to mid bass frequencies.

You have a SVS ported sub with variable phase, great. I have the sealed box version. Two subs work well and will provide a much smoother response than just one. I suggest you position it where it is not an inconvenience, anywhere really and using REW dial it in to give the smoothest response, then plug the port and notice the change, now tweak the settings somemore. With the 2nd sub, again place it where it is the least intrusive perhaps even using it as a side table. Tweak again for smoothest response which will mean returning to the first sub for a little adjustment. By now you should have a plot that is vastly better to look at and to listen to. You will begin to understand why I avoid ported subs. Of course plugging the port on the SVS may produce a smoother result but that then is sheer luck.

Bass traps are hated by most who don't understand what is at play feeling they want all the bass they can get which is antithetical to trapping bass. Well looking at your frequency response you are missing a fair amount of bass. The bass traps absorb some of the low frequencies that build up particularly in corners but not exclusively. They help reduce the severity of room modes and standing waves.

There is a paradox here in so far as bass is being absorbed but more bass is heard. Prior to obtaining a smooth response the nulls apparent in your plots is revealing the frequency and the amount of bass absent from the performance.

Using Bass Traps and multi-subs together is a revelation. You have now effectively removed the room's acoustics from the performance, like listening to headphones, and are hearing the musical event. No new component nor DSP can achieve this.

Please report back and tell us what you saw and heard by plugging the port. 

Question for the group here.  I tried, just for learning purposes, to use my SVS sub to see if it would help fill in that 60Hz dip.  Here’s the FR curve.  While it did fill in the 60Hz dip, it blew up the 35Hz peak more.

The phase is set to 90 degrees on a variable dial that goes 0 to 180.  My question: would playing with phase at all help this curve?

And a more general question, what is causing this 60Hz dip? Cancellation of sound waves at 60Hz, right?  Theoretically, if I put big bass traps in the back corners of the room, does that solve this issue as well as potentially the 35Hz and 100Hz peaks?  Or is it not that simple?

Did you try plugging the port on your sub? Just push some foam or a sock into it. Yes of course playing with the phase (timing) will change the curve, that’s the whole idea. Get a second sub.

Does your SVS sub not have the ability to adjust remotely from your phone? There is more than phase to adjust. You need to also vary the output SPL, Raise or lower the crossover frequency, Change the slope of crossover from 6dB/octave to 24dB/octave, vary the Q and room gain. If you change any of these settings then go back and adjust phase again, and so forth.

Bass Traps?  from my post above:  The bass traps absorb some of the low frequencies that build up particularly in corners but not exclusively. They help reduce the severity of room modes and standing waves.

It appears you did not comprehend my long post trying to explain all this so the best advice now is to learn from the masters. Look at articles from Earl Geddes, Floyd Toole and Todd Welti on multi-subs. Fussing around with DSP will not get you there.

The issue is I have very limited adjustments on my sub.  See pic below:

So I can adjust phase and level, but nothing else.

I was also having some issues getting REW to output to mains and sub at the same time.  So when I played with phase using sub output only, it didn’t change anything because I think it’s the phase interaction with the mains that will cause different responses to the FR curve.  Just changing phase if the sub is the only thing playing the frequency does nothing to change the FR curve.