Originally Posted by AVS For
Thanks for the detailed answer.
This is my scenario:
I had a 5.1 set of speakers and the sub just wasn't providing enough bass. So after a while, I purchased a nice big sub that accomplished the task. Now, about a year later, I just purchased a very, very good set of fronts and a matching center speaker. After experimenting with each sub, I find that with the new speakers, the system "blends" better with the smaller sub than with the newer large sub for "audiophile-type" listening. But when I listen to movies, or hard rock music, I want the bass to shake the walls and rattle the windows! Therefore, I want to add the large sub and have it do the heavy lifting below approximately 60hz when listening at eardrum-bursting levels, but still have the better balanced output from the small sub when the audio from the movie or hard rock is not outputting heavy bass requiring the large sub. Whew!
You are welcome, but unfortunately, I don't believe my answer was quite correct with respect to automated room EQ. But then, you may not even have any form of room EQ. What you are proposing is extremely unusual, even by AVS forum standards, where people try unusual setups all the time. It can be very difficult to make subwoofers with inherently different capabilities play well together. The combined sound of two very dissimilar subwoofers may randomly peak at some frequencies and cancel at others.
As Ray suggested, the problem you are experiencing with the larger subwoofer, which doesn't blend very well for music, may be one of positioning. Or, perhaps it is related to something else entirely. You might, for instance, be using different crossovers now. I think if you wanted really serious assistance from people on the forum, you would need to describe your situation in detail, including the two subwoofers in question, how they are positioned in your room, what kind (if any) of automated room EQ you have, and what settings, including crossovers, you are using.
Making even a single subwoofer do what we want it to, in a room, is not always easy. Making two different subwoofers do what we want them to is even harder. Personally, if I really liked the larger sub, I would try to work with it to make it sound better for all my listening content. And, if I really liked the smaller sub that much better, I would get rid of the larger one and just have two of the smaller ones. Getting two identical subs to sound good together still isn't always dead easy, but you would have a much better chance than you will with two very different ones.
If after all of this, though, you are absolutely determined to proceed with your plan, I wouldn't try to use any sort of room EQ that affects the bass frequencies, because it will potentially make things worse. I would probably still do the sub crawl that Ray suggested. And, once I found the best spot for a sub, I would put the small sub on top of the large sub, with something in between to protect the finish.
Then, I would have only the small sub playing for "audiophile" music, and I would only have the large sub playing for room-rattling material. But, both subs would play full-range (120Hz) when it was their turn to play. Personally, I would recommend investing the time and effort to get the large sub to play better, or I would get rid of it. Having two completely different subwoofers is sort of a waste, and it's probably never going to work very well for you.
But, if you are determined to have one subwoofer playing most of your music, and the other subwoofer for movies and hard rock, then I would let them take turns playing, from the best spot in the room. And, I wouldn't try to use any sort of bass EQ in the process. That is likely to make things worse, instead of better, if you try to EQ them together, or EQ one and then change to another. I would just turn one off, and the other one on whenever I wanted to listen to each one, if I were really determined to do this.