OP, for a reasonably inexpensive DSP solution with more potential tricks in it's bag of, you might look at a Behringer DEQ2496....everything in a tape loop that you could potentially want and then some.  The calibrated mic it uses costs 25$....
I've 2 of the older 8024s' that allow me to 'run flat' in a variety of spaces they've been in without treatments....not perfect, but what is?

Sweetwater for new (free shipping); used might be 'out where, somewhere'...hard to mess up an eq.

Steep learning curve, but you'll learn a lot in the effort....:)

Cheers and good luck, J

OP:

For the record, room treatments and room correction are not equivalent.

Using a frequency response curve to determine if you need room treatments is only useful in the bass.  Above that the microphones won't integrate frequency response measurements over time the way we do.  You need time based plots for that.

Having said that, REW includes a room mode simulator but I find the AM Acoustics version free and easier to understand.

Now, as for EQ / Room Correction... the best you can usually do without bass traps is to clip peaks.  After that you raise the overall level of the bass to taste.

With bass traps that are effective at your problem frequencies you can mitigate both much better.

Point is, for your bass, use the simulator to make sure your speakers and listening location are away from the room modes you are finding.  Consider placing bass traps near the areas activated by those modes. 

As for the rest of your speakers, leave them alone, but in the mid to treble regions having appropriate mid/treble absorption and diffusion helps greatly with imaging and comfort levels.  Also taming reflections (which won't show up in a frequency graph) will make the room sound like you have much more bass.

@erik_squires 

Thank you, I’ll try the AM Acoustics version.

If I wanted to take time based plots, is that doable using reasonably priced tools, or is that a pro assessment job?

I did move my speakers to the 1/5 position from front and side walls, and LP to 1/3 position from back wall.  Seems to have helped some.  I’ll post the resulting curves soon.

I do have acoustic panels that I think could work for the mid/high frequencies.  Had no idea the FR curve and REW program was incapable of picking those up.

Do you have to spend big $ on something like GIK bass traps, or is there a more cost effective option vs spending $500 per bass trap - that can add up quickly!

Also, off topic, I had tried to send you a private message to ask about speakers as you had commented a fair amount on a particular brand and I wanted to ask your opinion on some things.  But I got a weird message about a moderator having to approve my message - not sure it was ever received by you.  Just sent another message now to try again.

Here's the freq response curve with my listening position about 5ft/60" into the room, which is at the 1/3 point.  Speaker baffles are at 37" from front wall (1/5) and 28" from side wall (1/5).

No toe-in currently.

1/3 smoothing, normalized to 75dB at 1kHz.

If I use +/-3dB as a criterial, there are those two peaks at 35Hz and 95Hz, big dip at 58Hz.  Not sure how badly these big peaks are potentially degrading the sound.  Besides that, a 4dB peak around 650-900Hz, but the rest of the FR curve is within +/-3dB.

This is sitting further toward the back wall at 51" instead of 60".

The 55-60Hz dip is reduced some, but overall it seems a little less smooth than the 60" FR esp from 200-600Hz.  Subjectively, it seemed to me that 51" was a little clearer, but the vocals a little less warm.  Not sure if that's consistent with what you'd expect from the FR curves.

Here are the two superimposed on each other. . .

On another forum, some members thought it this was workable and I could just go with this based on where the peaks/dips were, with 60" being optimal.

Finally, here's even further back at 45" (compared against 60" as a benchmark):

Here, the 35Hz peak is increased, the 58Hz dip is pretty dramatically flattened out, but the tradeoff is a dip created at 180Hz.

 Not  bad.  I always apply 2) DSP to flatten things out further after 1) room correction. .  Then finally a third layer of DSP 3) to adjust to my personal preferences, and roll off any wasteful low end to help out the amp and steer clear of clipping, if needed. That pretty much covers everything.   Older ears may be well served by ramping up the high end a bit.  A hearing test can help determine. I use Roon for this and may end up with anywhere from 1 or 2 to as many as 7-8 distinct filters per Room, including a single convolution filter for the room correction part.  Works great. Sound is fine tuned in the end exactly to my personal liking which is what it’s all about. 

Always do what you can to set up the room well to start.  Then DSP away towards your own personal sonic bliss.  Make good buying decisions to set up and  integrate everything well up front then anything is possible with DSP from there.