Originally Posted by chucks0
One other important thing to consider when deciding between 1 large vs 2 small subs.
While a flat frequency response is a nice goal, the reality is that in normal listening, you are unlikely to hear dips and nulls unless they are severe (in width, not height). In my setup, the frequency response at the primary listening position is completely flat with no dips or nulls. All of the secondary listening positions have several peaks and valleys. I know this because I have checked it with REW, but I have never had a single person watch a movie and comment that certain frequencies were missing or louder than others. Instead, they are blown away by the system. Bass in most content is a complex combination of frequencies and narrow nulls really aren't audible, even if you know the nulls exist.
This is why many people recommend getting the single largest sub you can afford now. While you can seldom hear the occasional null in frequency response, you can absolutely hear the difference between a sub that is more powerful than another.
Of course nulls are not audible. They're the absence of sound. You can't "hear" a null. You only know about nulls when you hear the same content being played without the nulls and you hear the missing information. It's not surprising that no one has ever complained about missing notes in your system. The old expression: You don't know what you don't know... (is missing)... applies quite well here.
I have a few discs I use to audition systems... content I know extremely well. If I notice bass notes are missing, (notes I know should be there because I know the content so well), I know the system has some nulls that are making those notes inaudible.
Elimination of nulls actually makes the bass seem louder and more powerful. That's because you get to hear ALL the bass, including the sounds that would have been cancelled by the nulls. In addition, dual, smaller subs will experience 3 to 6 dB of increased headroom, so the max SPL output could be very similar to the larger sub. The only thing the smaller subs give up is some deep LF extension, which is a worthwhile trade-off to get flat FR.
Flat, full bandwidth frequency response is the ultimate goal. The only way to achieve that in the bass is to use multiple displaced subs optimized for flat response.
Dr. Floyd Toole writes:
The real problem is standing waves, which cause bass to boom at certain frequencies, to be absent at others, and to be different in different locations in the room. Equalizing a single subwoofer can improve the sound at the microphone location, but nowhere else. A single subwoofer has no ability to reduce seat-to-seat variations or remove peaks and nulls. Multiple subwoofers can do both, presenting an opportunity to attenuate resonances, alleviating the associated pesky peaks and nulls in the standing waves. Chapter 8, p. 215 describes the options for reducing the detrimental effects of room resonances on bass. Some solutions work only in rectangular rooms, reducing the number of active resonances, and creating areas of rooms within which seat-to-seat variations are reduced. In the most advanced solutions, the resonances and seat-to-seat variations are essentially absent. All of the most effective solutions involve multiple subwoofers and these are well explained in Chapter 8.
Part 2, Subwoofer Options His book has a lot more information.
Bottom line, if the budget is fixed and no more will ever be spent on subs, then dual, smaller subs will generally sound better than a single, larger sub. OTOH, if the ability exists to buy a second sub down the road, then getting the single larger sub first is a good option with goal being to buy a second, (third and fourth+) down the road.
Here's another paper that explains the benefits of multiple subs:
If that's not enough, here's another:
Here's an example of what I' describing. The first 2 graphs are the subs in different locations. The first sub is located on the front wall between the CC and RF speakers. It has a wide deep null from about 40 to about 63 Hz.
The second sub is in the rear, right side wall at about 2/3 of the side wall dimension. It has a big null from 25 to 35 Hz.
If you look closely you'll see that were one sub has a null, the other does not. Therefore, they fill in for each other. The following graph is the combined response of the two subs:
The combined response has NO nulls and only a couple of smaller peaks, (Ignore the response above 80 Hz. That is the response of the CC. It is consistent in all 3 graphs and is immaterial to my point.)
The next graph is the subwoofer alone, but with Audyssey Room correction applied.
When a room correction system doesn't have to deal with nulls, and it only has to pull down a few peaks, it can do a great job of providing flat, smooth bass. The sound of flat, smooth bass is full, articulate and powerful.