I hope everybody doesn't attack me for this, but here it goes.
I too was unhappy with the boomy response of my Def Tech PF15. I suspected room modes were responsible. Using my Avia test DVD and Rat Shack SPL meter, I plotted a response curve for everything under 200Hz. It was horrendous, with two huge peaks and very little bottom octave response. Yet, I know the PF15 is a powerful sub and capable of better. I then purchased a pro-audio piece by Behringer called the DSP-1124P, the Feedback Destroyer Pro. Although designed as a feedback killer, it incorporates a digital, 12 band parametric EQ. I put it in line with my subwoofer output jack and subwoofer. I am still fine tuning it, and it requires a lot of patience, but already the results are very promising. The boominess is gone, and my main speakers have opened up considerably. Unlike similar products from Tact Audio that are more automated, but cost around $10K, the behringer piece has a street price of about $130.00. You can find it at places like Guitar Center and other pro-music stores. Other than a very, very slight increase in hum, I am very pleased with the performance and build quality of this piece. So far, it's probably the best $130 improvement I've ever made to my system. I am not an advocate of EQ in general, but in the bass frequencies, it seems to be just the ticket. Email me if you have questions about this.
I too was unhappy with the boomy response of my Def Tech PF15. I suspected room modes were responsible. Using my Avia test DVD and Rat Shack SPL meter, I plotted a response curve for everything under 200Hz. It was horrendous, with two huge peaks and very little bottom octave response. Yet, I know the PF15 is a powerful sub and capable of better. I then purchased a pro-audio piece by Behringer called the DSP-1124P, the Feedback Destroyer Pro. Although designed as a feedback killer, it incorporates a digital, 12 band parametric EQ. I put it in line with my subwoofer output jack and subwoofer. I am still fine tuning it, and it requires a lot of patience, but already the results are very promising. The boominess is gone, and my main speakers have opened up considerably. Unlike similar products from Tact Audio that are more automated, but cost around $10K, the behringer piece has a street price of about $130.00. You can find it at places like Guitar Center and other pro-music stores. Other than a very, very slight increase in hum, I am very pleased with the performance and build quality of this piece. So far, it's probably the best $130 improvement I've ever made to my system. I am not an advocate of EQ in general, but in the bass frequencies, it seems to be just the ticket. Email me if you have questions about this.