Tuning speaker / room response?

I'm also impressed with the graph. I don't have a web server at my disposal--so I doubt I'll try this at home. As to the problem. A couple of things, the meter should be on slow response. I've done it both ways, it doesn't seem to make much of a difference so I believe your graph is close to accurate, with the exceptions of Sean's post (which I'm very interested in the website). Mikec's post points out some very good areas for info. However, I'll bet you have a little over an 11 foot span between walls, or that's your ceiling height (or close 10.5 feet). Room tuning works very well about 125Hz. It does work at lower frequencies, but not nearly as effective. That bump at 50 Hz will be difficult to correct without electical correction. Most people, including myself, consider equalizers a measure of last resort--but if there is no other way--it will make a big improvement. Infinity has a single notch filter on their new speakers to accomplish exactly this. Tact has been making digital correction systems for sometime. Perpetual technologies also has a digital domain correction engine (but this only works if you ONLY listen to digital sources throught the Perpetual technologies P-1A). It seems to me there is a market for a very low noise low frequency addustable notch filter. This is such a common problem. McIntosh made room correction equalizers. They are very good--but something simplier with less noise would be prefered. Looks like an opportunity for someone or some company.

To really understand your graph you should describe the dimensions of your room, the position of the speakers and the position of your measuring SPM. If the graph is the speaker response at your normal listening position, then your have a fairly flat system response. IT IS NORMAL TO HAVE IN ROOM RESPONSE MEASUREMENTS SIMILAR TO YOUR GRAPH. The dip at 200Hz is probably a floor reflection phase problem. Try experimenting with speaker toe-in to address the peak at 4KHz. As a reference, perform the same measurement 1 meter directly in front each speaker. They should measure much flatter.

As a professional Acoustic consultant, I would give few suggestion about measurement tecnique (even if it is quite hard, with my poor English). First of all, the way you took measurements cannot give reliable results. In my opinion, the best signal to be used is pink noise. If you have a SLM with freq. analysis you can use a full band pink noise. Otherwise, there are CD with pink noise filtered in 1/3 of 1/1 octave bands. If you use a pure tone, the measure will be too much affected by the mic position (standing waves). If you repeat the measure 5 inches away, you could obtain totally different curve. In any case, the measure should be always taken averaging the value on a zone close to listening position, and not in a fixed point. If you have an integrating sound level meter, it will make the average by itself, otherwise you can average by yourself, but always using SLOW time response.
Regarding your curve, the response in low freq. is normal for a typical listening room. But, the high freq. response is usually much more flat, and your curve is probably affected my measurement errors.
As Abstract7 says, it is quite hard to get room correction with passive device at low freq. due to the long wavelength. Any absorbing device is effective if its thikness is at least 1/4 of the wavelength. At low freq. only resonant devices are effective, as Helmoltz resonators, or "vibrating board" resonator (I don't think this is the correct english transation). But, both of them, to have a good effect, requires a lot of surfaces and volume, (and have a very low W.A.F. :-).
For high freq. absorbtion, I suggest to avoid any exotic and expensive devices. Normal carpets and curtains are more than enough.

Paolo not bad for a fellow Italian from Italy. Now do you want to rewrite that in Italian. Good Advice

As a professional Acoustic consultant, I would give few suggestion about measurement tecnique (even if it is quite hard, with my poor English). First of all, the way you took measurements cannot give reliable results. In my opinion, the best signal to be used is pink noise. If you have a SLM with freq. analysis you can use a full band pink noise. Otherwise, there are CD with pink noise filtered in 1/3 of 1/1 octave bands. If you use a pure tone, the measure will be too much affected by the mic position (standing waves). If you repeat the measure 5 inches away, you could obtain totally different curve. In any case, the measure should be always taken averaging the value on a zone close to listening position, and not in a fixed point. If you have an integrating sound level meter, it will make the average by itself, otherwise you can average by yourself, but always using SLOW time response.
Regarding your curve, the response in low freq. is normal for a typical listening room. But, the high freq. response is usually much more flat, and your curve is probably affected my measurement errors.
As Abstract7 says, it is quite hard to get room correction with passive device at low freq. due to the long wavelength. Any absorbing device is effective if its thikness is at least 1/4 of the wavelength. At low freq. only resonant devices are effective, as Helmoltz resonators, or "vibrating board" resonator (I don't think this is the correct english transation). But, both of them, to have a good effect, requires a lot of surfaces and volume, (and have a very low W.A.F. :-).
For high freq. absorbtion, I suggest to avoid any exotic and expensive devices. Normal carpets and curtains are more than enough.