How flat should my room response be?

I am in the midst of treating my listening room. I also purchased an spl meter and a test tones cd. In a perfect world, we would all strive for a perfectly flat room response. However, given budget constraints and the reality of my room configuration, I know this is not possible. Given this, how flat should I try to make the room response? Is +- 2db ok? Or is +- 6db ok? I am looking for a realistic goal that I can set that will yield the best possible results.

Thank you,
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Bass frequencies radiate in all directions and interact heavily with the room....making it very hard to achieve a flat response in the bass without equalization and extensive room design and treatments.

Furthermore a lot will depend on the system and how precise it is; if a test tone of exactly 63Hz is played then what other harmonics/distortion does the system put out?

For example, an average system with say 20% harmonic distortion in the low frequencies (seriously this is very common) will produce your 63 Hz pure fundamental along with other harmonics at 20% of the level of the pure 63 Hz tone. In this case, this primary fundamental and the added harmonics will interact with the room to produce an average level of sound that might be significantly different from just a perfect 63 Hz single frequency. Given a specific measurement position, if the room produces a 30 db null at 63 Hz but is roughly flat for the other harmonics then the SPL meter would show only 14 db down when playing the 63 Hz test signal. If some of the other harmonics are boosted by 10db or more by the room then the SPL meter may even measure higher ...say only 6 db down! (I may have got the math slightly wrong but I hope you get the idea)

This suggests that it may actually be easier to generate a flat room response when playing pure frequencies on an average quality system!! Not that the average system will necessarily sound good because bass sounds have added harmonics or distortion.

It also suggests that a very high quality reproduction system with full range may be expected to place much higher demands on the room setup, treatment etc. A pefect amp and speaker would show you the full null by producing exactly and only the pure 63 HZ a hard car suspension as opposed to a soft forgiving suspension... in one you really feel the bumps and road the other you can't really feel the road even if it feels generally more comfortable on a variety of surfaces.

Given the above huge caveats, if you can achieve +/- 3 db in the bass then I think you have an absolutely phenominal setup. I would expect +/- 10 db to be more typical in the bass (and quite acceptable sonically to many)...

Outside of the omnidirectional bass frequencies (say above 400 Hz ) then +/- 3 db should be readily achieveable in most systems (the speakers controlled dispersion already helps a lot to reduce room effects)
This is what one guy did that was where you're at (me too for that matter). This was a home theater room, but you'll get the idea.


You don't have to do the entire project at once, I'd start with bass traps and work your way up as time & money permit.

Great Article.
Agreed..fishboat...that as a great article. I am actually using the REW software mentioned in that article.