How does adding a second subwoofer improve your systems SQ?

@markj941,
good sum summary.  i just added two REL t9i to my system and am very happy with the sound.  they integrate very well with my large british monitors compared to two other sub brands i tried. 
an important considesrtion is distance from wall behind them.  closer than 8 inches created strong peaks in the response.

You are getting a just sample of what’s going on down there, you are drawing conclusions about the Roger Waters track with regards to hearing it with two L and R subs, it’s obvious. Because if you did you wouldn’t be saying what you just said.

It acts the same way on my main system, which has bandwidth to 20Hz out of the main speakers (Classic Audio Loudspeakers Project T3.3).

It appears that bass traps have their cultists too. The simple fact is they are not always practical. A local customer of mine has been using them for years; I finally got him to try a DBA and it solved his bass issues which he's been fighting for over 20 years. His room is arguably the most treated room I've seen anywhere. He was pretty adamant about how great they were until the DBA showed up.  At this point he's running only about 1/5th of what he had before. In my room I simply don't have the space to place them at all, but adding a pair of subs (thus creating a DBA) is easy since they can hide under a couple of tables in the space. No way could I get bass traps to do the same job in my room, and the GF won't stand for it anyway. Science works so much better than myth for solving these problems.

Hi markj941,
I added a set of  REL subs to my system with floor standing speakers and It was a great improvement .Most notable was that the overall soundstage was cleaner and there was a much greater sense of depth. The bass was more authoritive, the details were extended especially in the midrange. Drumskins, toetapping, broken guitar strings, etc. all clearly audible. My system is set up in my livingroom, and I do not have any real room treatments to speak of. I dream of having a dedicated room one day, but the addition of the subs definately elivated my system to the next level.  Mark Knopfler's Private Investigations is also a good comprarable. 

Good Luck

In my experience, bass traps do help, but they help mainly by controlling bass overhang at frequencies above 40 Hz -- and that’s the BIG traps. Trying to even bass response significantly with bass traps is a losing proposition. But in a room that retains bass, they can be useful for sure.

Still, rejecting DBAs because some people are tireless boosters is like rejecting vitamins because some think they cure everything. It is not logical to discard a proven approach because some adherents are obnoxious (not that we have any of them here).

I thought Erik’s linked essay was useful except for that tack. In particular, it pointed out that adding subs is not plug-and-play, if one wants to get good results. Good crossovers, some kind of EQ, and phase matching have been indispensable, when I’ve done it.

How is this even a discussion in the audiophile world any more?

- 2 subs is better than 1, due to evening out of peaks and valleys. 4 is better than 2. In a rectangular room, 3 may not be better than 2 (may not be intuitive but trust the math). This works because of inability to localize bass (see below).


- bass traps obviously can help. They also have to be very big to work really well, and the bigger the room, the bigger they need to be due to the frequency of the bass nodes. Small resonant traps also have small bandwidths.

- No matter how much some people will plead, we can't localize bass less than about 120Hz, hence using 80Hz with steep crossovers. There will always be lots of claims this is not true, and in every case this will be a factor of unequal room response between channels, poor sub/main positioning that causes unequal room responses and/or beamed cancellation effects, inadequate slope, or distortion. Don't believe me? You don't have to. There are a plethora of studies done on this (proper ones, not ad-hoc with improper setups). If you choose to ignore them, I can't help you.


- When Toole was talking about the potential for equalization, he was not talking only about frequency, but phase as well (between multiple bass units) for optimization

- If you think massive floor standers with deep bass response are the "ultimate" in reproduction, you either have an acoustically great room with a significant amount of acoustic treatment, and well shaped room at that, or you are misinformed. The position for optimum bass response in a room of two speakers is not going to be the same location for optimum in-room response, imaging, sound-stage, you name it. It sure sells some expensive speakers though, and since the average audio reviewer blathers over anything expensive, from pictures probably has a less than ideal listening room, and almost assuredly knows the bare minimum about acoustics and likely even less about the science of sound, should one be surprised? Most don't even attempt to measure in-room response, let alone direct/reflected energy at the listening position in order to optimize performance and/or provide consistent reviews.


- On the spouse factor, discreet subs are likely to be a better sell than large floor standers in less than optimum locations for bass, SQ, or spouse acceptance.


Whether you believe any of what I wrote or not, does not really matter, people will still pay me to design and implement acoustic spaces and the sound systems in them, and acoustic products that use these and more complex principles (and tools), that are based on science, not conjecture. Many aspects of the perception of sound are subjective. Many aspects are not. You will have an easier time achieving audiophile nirvana when you accept which are which. Reality is a harsh mistress. She's not your mom.