You list your electronics, but I didn't see a mention of the speakers you are using. Since it is your speaker/room interaction that is likely the issue, it might be helpful to know what speakers.
Are you using single frequency tones or warbled test tones? Single frequency tones can give some deep spikes/nulls which I would tend to ignore if they are very sharp....30 db swing from peak to trough in your size room is not surprising. Check out what Ethan Winer's or Realtraps website says about typical room response...it is a real eye opener....don't worry you are not alone in having discovered a far from flat room response.
The dip between 100 Hz and 400 Hz is very worrying if it is a continuous and deep trough as is the decline above 6300 Hz - unless you are talking only a few db average drop (say less than 6 db from average). Although you will always have peaks and troughs due to the room modal response, which in your case will be quite obtrusive (small and close to a cube in shape), you should aim for a broadly even response when taking an average....a little bass heavy and a little roll off in the treble seems to be what most people enjoy most.
Room treatments can help and so can a PEQ like the one made by Behringer... but your room may pose a challenge which you can only expect to mitigate.
Thanks, I forgot to put that in. The speakers are Boston Acoustic VRM 80's. http://www.bostonacoustics.com/home_product.aspx?product_id=189
Recommended Amplifier Power
Frequency Response (3dB)
Dual 5¼ (135mm) DCD copolymer
Sensitivity (1 watt (2.83v) at 1m)
1" (25mm) black anodized aluminum dome with AMD
58 lbs (26.0kg)
The test tones are single frequency tones. While trying to figure out what was happening I looked at the Rives audio instructions and realized that I have the SPL meter on an 'a' weighted and it is supposed to be 'c' weighted. This made a huge difference as the differences in that the frequencies are only 13 db difference from the highest peak to lowest trough across 40 - 12.5k hz. I now show a small bass boost as I thought should be in my room. I am able to correct this. Now can I make the highs a little less fatiguing? I will try some absorptive panes at the first reflection points and behind my head instead of the combo diffusion/absorptive ones I made.
Thanks Shadorne, your response indirectly sent me to the info I needed and the RealTraps web page is also helpful.
Bad quick math the difference is now 23 db in audible range. I see my bass node now and I can correct that, but I have a narrow +10 db spike at 630 hz that I am not sure how to mitigate. Any ideas? Also, are absorptive panels at the first reflection point likely to smooth out the frequency response above 200 hz?
it is your perception of the sound of your stereo system which is important.
i reviewed audioquest cables and it is possible that replacing them with other cables may partially solve your problem. what cable you ask ?? try dcaa interconnects--all copper. you might consider trying another amp and preamp and also some ac cords, to see what affect such changes have on the sound and whether you prefer the sound with other components. the room may need treatment.
a further test is to use a high quality spectral analyzer at the listening position, using white or pink noise.
Thank you for your response, I may consider going back to all copper interconnects to help tame some of the high frequencies as they can be fatiguing. The question around smoothing out the response is mostly a curiosity; I am not too worried about it, but I would like to hear what audible difference a flatter feq. response would have. You also mentioned an interconnect, but I cannot identify or find info on it, dcaa?
With such a small space, it is very easy to overload the room at too high SPLs. I would consider setting your meter at 0 at 80db and 1Khz. Also, the distance from your driver to the surrounding boundaries will have the most significant sonic effects. For example, if your drivers are 30" from the floor, placing them 30" from the front and side walls will reenforce the upper bass...the listening position being near the rear wall will only add to the upper bass as well.
If you are able to place your speakers along the wide wall, about 6 ft. apart and 2 feet from the front wall to the front of the speaker, you should help your upper bass response become more flat.
The upper frequencies will be very difficult to tame in such a near-field listening situation. I would attempt to fire my drivers as near straight ahead as possible without losing the center image.
When dealing with small listening rooms and near-field conditions, the first reflections are much less of an issue as the time delay in reaching your ears is insignificant. The brain simply can't process reflections that are so close to the arrival time of the original sound. However, high spls will really muddy up the sound as the room quickly becomes a standing wave nightmare.
A narrow spike at 630 Hz may be room related....try moving the SPL meter by 1 foot and see if the spike disappears. If it does then you may want to try acoustic treatments as an EQ will not solve that problem except at that exact listening position....and moving speakers or listening position around may simply move the null or spike to a slightly different frequency. (bear in mind your ears are about 6 inches apart and the wavelength of 630 Hz is a couple of feet)