Small room....treating 1st reflection points

Tom6897, Look at the link I posted. Table shows sound absorption vs frequency. I was mostly interested in taming slap echo and mid-bass frequencies. These panels are glass rigid foam. I've read that organic foam has non-linear characteristic (of absorption vs. frequency, I assume).

36.75Hz is pretty good. As long as room doesn't amplify around 60-80Hz, where many speakers have "hump" it is OK and might even help to reinforce extension.

IME, absorptive and/or diffusing treatments at the first reflection points can help with high frequency problems. As you go lower in frequency, these devices become less effective. Below 100hz or so, Hemholtz resonators are the only reliable treatments that I've found (other than room correcting EQ schemes).

It's hard to say whether 1" foam will work for high frequency issues until you try that foam in that room. OTOH, it's easy to say that you'd be very unlikely to get any benefits from 1" foam at low frequencies.

1" foam/treatment will work to some degree, in particular with higher frequencies as noted, just not as much as equivalent 2" foam product.

No way to know what will "sound best" without trying.

I like the "lego" approach with wall treatments. Start with smaller measured amounts of treatment, like 2'X2'X1". Add more or less as needed until best results achieved at primary listening location(s).

So what's a good place to buy prefab treatment products without breaking the bank?

Rebbi, GIK makes nice and affordable ones. I use Vicoustic personally.