Let's Just Say This

These guys will offer fairly good advice based on room dimensions. They helped me...and the advice is free.
 
http://www.gikacoustics.com/
 
 
Regards,
Dan

Jesse Screed
should one mitigate the low frequencies at the bottom of the phase, or at the top, or meet the phase head on at the midsection, in the middle, or floor to joist, or at the shortstop between second and third?

If you are unfortunate to have a low frequency strike your trap at the zero-crossing, the absorber will have literally zero effect. At that point in the wave's cycle, there is no energy to absorb. That's why the depth of the absorber has to be a significant fraction of the wavelength of the lowest frequency you need to tame, so that it'll catch at least part of the upper and lower extremes of the waveform.
 
Because you've filled the space between the floor joists, that will give significant absorption down to 550 Hz or thereabouts, with at least some measurable attenuation down to ~100 Hz. Unfortunately, your ceiling-to-floor resonant frequency is 154 Hz. Not much you can do about that with your already-low ceiling. Best you can do is measure the room and find out where your resonances are; just knowing that actually helps a lot.
 
I have a 70 Hz resonance here, floor to ceiling. I have double-thickness pink fluffy in the attic, making it one big bass trap. But even that's not enough to quash that resonance completely, so I just keep it in mind when EQing a mix, knowing my kick drums aren't really quite as thumpy as I hear them in that room.
 
Do you maybe have room in the corners for bass traps?
 
BTW, in terms of room resonances it really doesn't matter what volume you mix at. It's a widely held myth that you can get around room acoustics by mixing quietly. Sadly, it ain't so. What matters is the ratio of the ears-to-monitors distance versus monitors-to-walls-to-ears distance. If the distance to the nearest wall is equal to the distance to your speakers, whatever bounces off the wall will only be 6 dB quieter than the direct signal from the speakers. That's one reason why where you sit and where you place your speakers is a big deal.
 

It's easy to become obsessive about it, but the reality is that unless you start with a BIG room and an equally big budget, all you can hope for is a frequency response that's flat to 6-10 dB rather than 30-40 dB, and a manageable RT60 of < 500 ms. Truth is, you can train your ears to make do in just about any room, given enough time and repetition. Your brain is an amazingly adaptable organ. Taming acoustics just makes it easier.
 
Here's an old post I made years ago about using any old microphone and SPAN to analyze your room response at the mix position. It's dated, but the principle still applies. For a more detailed picture, get the free REW, which takes it one step farther by showing how frequency response changes over time.