Have you used a frequency/tone CD w/SPL meter ...

Yes,
I own two Hsu Research TN1220 HO subwoofers with their Model 500A amp with 24db per octave high and low pass x-overs at 51hz. I sit midway, [in the center of my listening room], between the subs, in which one is near the middle of my front wall between my speakers and the other is in the rear of my room near the middle of the rear wall.
My listening room, including the dining room and kitchen due to large open spaces is roughly 23 x 23 x 8.
Using a Rat Shack digital sound level meter, with corrections, and the Hsu Research CD-R with 1/3 octave warble tones and a 100 hz reference:
I have a broad peak of about + 7 db at 16hz! and 20hz,
a -4db dip at 25hz, a -3db dip at 31.5hz, same as the 100hz level at 40hz and 63hz, a -2 db dip at 80hz, and a big + 8 db peak at 50hz.
With both subs along the rear wall I have a broad +7 to +9 db peak at 16 to 25hz, a -3db dip at 31.5hz, same as 100hz at 40hz, a -2db dip at 63hz, a -4 db dip at 80 hz, and still have the +8db peak at 50 hz.
The 50 hz peak surprised me because running the speakers full range without the subs or high pass filter resulted in the same +8 db peak as when using the subs, mains, low pass, and high pass filters all together!
I expected the 50 hz peak to be reduced in level by about 6db by using the latter due to the natural -6db dip at the x-over point using 24 db per octave filters, but it was not reduced at all!
Very strange indeed.

I use a Radio shack analog spl meter with the Rives test response disc. The good thing about that disc is that there are a set of tracks that compensate for any false readings that the Radio shack device may give.

Rob

Kenyonbm...Your results are not unusual. And what a lot of work!!! (Get yourself a Behringer DEQ2496). By the way, did you try repeating the meter measurement several times at the same spot? I bet that some of the veriation is simply the measurement. Low frequency should not vary much over a short distance. High frequency will vary.

Eldartford,

Would you please tell us some more about using the spectrum analyser? What other equipment is required, microphones, sources etc.

Any suggested reading?

Thanks, Ken

Nice to read everyone's responses so far.

Tbooe, the Rat Shack meter, IMO, is fine for this task. I have an analog one, as well as a calibrated digital unit from Monarch Instruments (Model 321 @ $259). Both read quite similarly head to head.

Obviously, I'm a proponent of this sort of objective assessment of one's system. Loudspeaker/listener position changes to mitigate room modes on the bass end, as well as effects of room treatments and subwoofer integration all benefit, in my experience. It is revelatory simply to measure, albeit somewhat imprecisely, the in-room performance of one's painstakingly-assembled components. My, what our ears/brains must accept simply in the frequncy domain as "faithful" reproduction!

Panacea - hell no, but anyone integrating a subwoofer/pair will likely be very surprised at the imprecision of plate amp crossover/phase/parametric EQ adjustments, for one. I recently spent a number of hours dialing in stereo "sub"woofers (10 inch Focal woofers with Adire ADA300 Class D plate amps - DIY))to even out terribly uneven 30-160 Hz in-room response with fairly inflexible loudspeaker/listener positioning constraints. The Adire plate amps are among the elite of their ilk, with dual crossovers, continuous phase adjust and 2 band parametric EQs (16-80Hz freq range and continuous Q adjust). Nonetheless, the physics of my listening room proved more complex and unforgiving even for this array of "tools". I did achieve +/- 6.5 Hz from 30-12,000Hz compared with +/- 12Hz before adding/dialing in the powered woofers. Subjectively, vastly more enjoyable.