kenjit:"in other words we dont really know how all these things work so just do a bit of each and see what happens. "
Hello kenjit,
That's not what Duke stated and I think you're aware of that. Most members already understand that he knows how all these things work and that he stated that utilizing bass trapping room treatments, EQ and multiple distributed subs in a room and system will all contribute to better in-room bass performance in most any given room.
Bass trapping absorbs in-room bass energy which shortens the decay times and thereby reduces the magnitude of both the peaks and the dips everywhere in the room. (The in-room frequency response tracks the time domain response, and vice-versa, in the bass region.)
EQ is very good at reducing peaks but not so good at filling in dips, which are caused by modal cancellation, and driving that cancellation harder can eat up a lot of power and excursion (a 6 dB boost to fill in a dip would call for a doubling of excursion and a quadrupling of power). EQ of a single subwoofer is most effective at a single location, because the room-interaction peaks-and-dips will be at different frequencies for different locations within the room. So EQ can be great in the sweet spot, but it usually make things worse elsewhere in the room. In general the larger the listening area we try to fix with EQ, the less improvement we are able to make at any specific location within that area.
A distributed multisub system results in a significantly improved peak-and-dip pattern. Each sub contributes its own unique peak-and-dip pattern, but each sub is only contributing maybe 1/4 of the total bass energy, so the net result is many small peaks and dips instead of a few large ones. This can have a non-obvious psychoacoustic benefit: When a peak and a dip are fairly close to one another (within about 1/3 octave), the ear/brain system averages them out. So the perceptual improvement tends to be greater than what we would infer from eyeballing before-and-after curves. And this improvement is not limited to a given location, but extends throughout the room.
Duke is not recommending individuals do a little bit of bass trapping, a little bit of equalizing and a little bit of utilizing multiple subs and just see what happens. He's stating that it's best to utilize all 3 approaches, bass trapping, EQ and multiple distributed subs, in a thorough and complete manner in order to realize the optimum bass response performance attainable in a given room.
I know my intention, and I believe Duke's intention, of contributing our knowledge and experience on this thread is to save some time and effort for those interested in attaining exceptionally good bass performance in their rooms no matter their room details or the specific main speakers they utilize.
Of course, I realize that Duke has superior knowledge and experience on this stuff than I possess. But I believe I also have relevant information to contribute based on my experiences using his AK 4-sub Debra DBA system for over 4 years thus far.
You're more than welcome to take the long path I took in researching the distributed bass array concept via reading scientific White Papers on the subject written by Dr. Earl Geddes and Dr. Floyd Toole as well as other writings on the subject from Harman International's Todd Welti and Audio Kinesis's Duke Lejeune and James Romeyn before finally deciding to take a bit of a leap of faith and buying the $3K Debra and giving it a try in my medium sized room with Magnepan main speakers. I just thought readers might appreciate the time saving gains resulting from summarizing the main dynamics involved in the DBA concept and my 4+ years of experience enjoying it.
The reality is that I'm currently only using one of Duke's recommended three methods of attaining very good in-room bass performance, the use of the 4-sub DBA concept system, but I'm still achieving what I consider near state of the art bass performance throughout my entire room without the use of any EQ or bass trapping.
However, I respect and trust Duke's advice about bass trapping, EQ and using multiple distributed subs. I also had a free room analysis done by GIK Acoustics that recommended bass trapping so I just ordered about $3,500 worth of room treatments that includes stacked bass traps in all four corners, two 5.25" thick 244 bass trap panels on the front and rear short walls and a 50/50 ratio of absorbing and diffusing treatments throughout my room for midrange and treble frequency control. Once these are all installed, my plan is to listen to the results before deciding if EQ and any further room treatments would be worth trying.
Tim
