[Housteau]

When I did my room treatments I went ahead with broadband absorption instead of just targeting specific problem frequencies.  It worked well and I consider it a success story:  http://www.audiocircle.com/index.php?topic=31520.0

However, when I first posted that thread I had left something out that may be important for others to consider.  There was something involved in that treatment process that I had not read about previously, or had considered prior to finishing my project.  When taking the broadband approach the overall level of bass in my room, although much smoother, was less.  In thinking about it now this makes perfect sense, since so much bass is being absorbed in order to eliminate the reflected waves that would otherwise reflect back into the room and become either additive with each other, or cancel out frequencies due to phase.

For me this wasn't an issue since I bi-amp with an active crossover and was able to correct for that change in overall bass level immediately, using test tones as my guide.

I wanted to share the thought that before someone jumps into this, they should consider that they may need to do a similar correction, and to be sure their speakers and/or system can accommodate this adjustment.

[ZooDog]

I think that the subjective level of bass before and after treatment depends on what type of bass problem one is addressing.  If one has a 10db bump at 50hz at the listening position then when treatment is added it will surely seem like the bass level has decreased.  However, if one has a 10db null at 50hz at the listening position then it will seem like there is more bass after treatment. 

[Housteau]

I was not just being subjective in my comparison, but did the measurements as well.  The overall result of the proper treatments and the necessary realigning of the upper frequency spectrum to my newly corrected lower frequencies at the crossover point is both subjectively and measureably much improved.  I understand what you are trying to say in your example, but really your example works best if that specific frequency @ say 50 Hz was targeted for treatment.  In that respect I would totally agree. 

However, with broadband absorption you are not just aiming at 50 Hz.  You are absorbing (depending on thickness of material and other factors) possibly the upper 20s all the way up passed 250+ Hz.  So, with the broadband approach your problem @ 50 Hz would be smoothed out as well as many others you may not have been aware of, but also many of the other surrounding frequencies already in alignment would be absorbed as well.  The end result is an overall smoother graph of the low frequencies, but as in my case, also out of proportion to the upper range.  It is not a problem as long as you are able to make the corrections.  Many speakers have the ability for such adjustments built in already, since speaker builders often take different types of rooms into consideration when designing their products.

[klh]

One can put a parametric EQ between the sub out and the subwoofer to do much the same thing. If the mains cross over to the sub at 80Hz or so, one can add a house curve of his liking, and since it can also smooth out the peaks and troughs in the lower frequencies that remain, he ends up with a wonderful low end (provided he has a sub that can handle EQ... and that he desn't try to get the sub to do something  it wasn't designed to do).