[pinnahertz]

That was in your room, to your ears, with your crossover filter and with that particular song. 1. Professionals have seen many more examples and that's why they end up recommending something different as "good enough for most people". 2. 80 Hz is a bit high, for example; a better crossover for most contexts is 60 Hz if you're going to use a single sub. 3. Also the crossover slope can make a difference: 12 dB/octave is pretty bad, as it lets audible amounts of "wrong-frequency" material into both of the channels it's supposed to separate, and then the sub will give away its position by reproducing things it wasn't supposed to reproduce. 4. Also the sub should be high-quality, i.e. with very low THD, otherwise, again, it might give its position away. 5. So the choice seems to be roughly between an excellent sub + an excellent crossover on one hand, or whatever crossover you can get and whatever 2+ subs you can get, if the goal is to preserve correct soundstage down to the bottom of the spectrum.

1. As a Professional, I have not seen very many examples that didn't require or benefit from the 80Hz setting, largely because thats a frequency where most mains and are still working well. Cross over there before things start to get ugly.

2. The article you linked to deals with the specific case of mains with strong extended bass response and a bass management setting of "Large" that permits that response by not rolling them off. A single sub pretty much never really works well except for a (hopefully desired) single seat in the room. Any system requiring my services has more than one sub, I've never specified less than two.

3. 12dB/Octave is not necessarily bad if the splice (that's the frequency band where both mains and subs hand off to each other) is carefully managed. But that's true for any crossover slope. Steeper crossover slopes don't get you away from issues in the splice. This is where measurements come it, along with a means to respond to them in both frequency and time domain.

4. Past a sub producing horrific amounts of distortion (again, not a world I working in much) what gives a subs position away mostly is intensity cues. Using a single sub, often near field, has this issue.

5. No matter how excellent a sub is, and how "excellent" a crossover is, a single sub will hardly ever produce an even bass spectrum over a large listening area, or even a small one, unless the room is very, very large and sub position can be optimized. The benefits of multiple subs is not small in this regard.

edit: goofed on #1. should have been "didn't"

 

[pinnahertz]

Yet another reason to prefer the dual-sub setup: among the many constraints it relaxes for you - while still giving you reliably correct soundstage - is the crossover frequency.

The number of subs doesn't change the crossover frequency, the performance of the mains and sub does.

 

[pinnahertz]

I really don't know why I need a second sub when the one I have fills the room and is able to work with my mains crossing over at 80Hz without affecting the directionality. I think the only reason one would need a second sub is if their room layout isn't optimal or the sub isn't powerful enough to fill the room. I have a 12 inch Sunfire True Sub and I have the thing dialed way back to make it balanced. I'm sure it could fill a small nightclub all by itself. I know that it can make all the walls in my listening room vibrate like mad. It totally fooled the auto EQ in my Yamaha AVR. It pumped out so much sub audible bass that the auto EQ freaked out and tried to dial it all the way to zero. I ended up using the Sunfire setup and then adjusted the crossover to the mains manually. My mains have 15 inch JBL woofers that go low, but the Sunfire goes down well below 20Hz and it's clean and flat all the way up to 120Hz. 80Hz and one sub work perfectly for me.

If you did some response measurements you'd find out why you would benefit from a second sub. It's not about filling the room or really about volume at all. All rooms have modes, and you cannot EQ up the nulls, though you can do some good with a trap. One sub in a room guarantees a null or three. You may have just lucked out and not landed with any bad ones hovering over your LP. It doesn't usually happen that way.

 

[abm0]

5. No matter how excellent a sub is, and how "excellent" a crossover is, a single sub will hardly ever produce an even bass spectrum over a large listening area

The number of subs doesn't change the crossover frequency, the performance of the mains and sub does.

I was very clear and explicit that my statements concerned only the goal of reproducing a correct soundstage / correct stereo separation, nothing else. Both of these quoted replies from you are beside the point of soundstage reproduction - my concern was strictly with what frequencies come from where (or appear to be coming from where), and the chosen crossover point is one of the major determinants. With two subs positioned relatively close to your mains it becomes pretty much irrelevant where you set your crossover - your stereo image will remain stereo all the way down.

Of course the evenness of bass reproduction across the room is yet another problematic aspect of single-sub systems, but I wasn't getting into that as it's a bit off-topic (not about directionality).

 

[bfreedma]

I was very clear and explicit that my statements concerned only the goal of reproducing a correct soundstage / correct stereo separation, nothing else. Both of these quoted replies from you are beside the point of soundstage reproduction - my concern was strictly with what frequencies come from where (or appear to be coming from where), and the chosen crossover point is one of the major determinants. With two subs positioned relatively close to your mains it becomes pretty much irrelevant where you set your crossover - your stereo image will remain stereo all the way down.

Of course the evenness of bass reproduction across the room is yet another problematic aspect of single-sub systems, but I wasn't getting into that as it's a bit off-topic (not about directionality).

You might get lucky and find in your room, the best location for subs is beside the front L/R, but for most setups, that won't be the case. One of the primary reasons to use subwoofers is the ability to place them in the optimal locations in a given room. In the dozens of rooms I've measured, setup, and done EQ for, I've never had the best location for dual subs be next to the mains. Given that, a crossover at 80hz or lower avoids localization of the sub's output.

 

[bigshot]

1. As a Professional, I have not seen very many examples that require or benefit from the 80Hz setting

Well if you ever get to Los Angeles, I'd be happy to demo my system for you and show you some exceptions to your rules!

I have a few non standard theories on getting the most out of my room and system. I've arrived at them by trial and error. Theories are a great starting point, but you can follow all the rules and it won't end up sounding the best that way. Rooms are a wild card and you have to work with them, not against them.

By the way, I would never want to defeat bass management by setting my mains to large. That would eliminate the sub entirely from most music I listen to, since most of it doesn't have an LFE channel.

 

[abm0]

One of the primary reasons to use subwoofers is the ability to place them in the optimal locations in a given room.

Never heard such a thing before. I thought it was simply to reproduce lower frequencies correctly without paying through the nose for god-tier floor-standing multi-driver monsters that can do it all themselves. And I thought the "strange" positioning was just a necessary evil, not an end in itself.

In the dozens of rooms I've measured, setup, and done EQ for, I've never had the best location for dual subs be next to the mains.

Depends on what you mean by "next". I was thinking of "25% positioning" (see here) when I said "relatively close", and I don't think that audible bass frequencies up to whatever reasonable crossover you're going to set will ruin the soundstage width just because the sub on each side is 1 foot to the left or right of the corresponding main cabinet. Nobody hears bass directionality with that much precision, unless they're standing right next to or between the speakers, meaning: nowhere near the (critical) listening position. Once you have two subs at "25% positioning" in a dedicated listening or "cinema" room, the soundstage problem should be mostly solved.

 

[bigshot]

Boy! That article succeeds in making the subject overly complicated! I need a nap just looking at it!

 

[pinnahertz]

You might get lucky and find in your room, the best location for subs is beside the front L/R, but for most setups, that won't be the case. One of the primary reasons to use subwoofers is the ability to place them in the optimal locations in a given room. In the dozens of rooms I've measured, setup, and done EQ for, I've never had the best location for dual subs be next to the mains. Given that, a crossover at 80hz or lower avoids localization of the sub's output.

Never heard such a thing before. I thought it was simply to reproduce lower frequencies correctly without paying through the nose for god-tier floor-standing multi-driver monsters that can do it all themselves. And I thought the "strange" positioning was just a necessary evil, not an end in itself.

Nope. Bass in a room works by generating standing waves, modes. The more you have evenly spaced, the more even the bass spectrum is. However, small rooms have few modes, and rooms with similar dimensions tend to bunch different axial modes up at common frequencies. Between modes are nulls where there are huge dips in response. You can't EQ them out because the are modal nulls. Moving subs changes what modes are excited, and adding more subs stimulates even more modes. If you get enough of them, even a smallish room that would normally have mode clusters (peaks) and huge dips can be filled in and smoothed out by placing multiple subs in the right locations.

Depends on what you mean by "next". I was thinking of "25% positioning" (see here)

Yes, great link. It should be read and studied. Kind of what I just said, but he says it this way, "In most circumstances two subwoofers will perform better than one. While you might assume this is for added SPL, the greatest benefit will actually be smoother bass response. Two subwoofers are easier to place and result in a flatter frequency response and creation of a much larger “sweet spot” for everyone in the room to hear smoother and more consistent bass."
I have no idea where you came up with 25%. It's a much bigger deal than that.

when I said "relatively close", and I don't think that audible bass frequencies up to whatever reasonable crossover you're going to set will ruin the soundstage width just because the sub on each side is 1 foot to the left or right of the corresponding main cabinet. Nobody hears bass directionality with that much precision, unless they're standing right next to or between the speakers, meaning: nowhere near the (critical) listening position. Once you have two subs at "25% positioning" in a dedicated listening or "cinema" room, the soundstage problem should be mostly solved.

Again, no idea what 25% refers to. No, you can't localize bass that way. People claim they can, but mostly that happens when they are very close to subs and there is an intensity differential between ears. Otherwise, at a distance, the intensity based localization is compromised by the lack of much differential, and you can't hear any pinna-based directional response cues, certainly no timing difference because of the huge wavelengths. Bass localization is a function of frequency and proximity to the driver. That's one reason multiple subs work well.

You might get lucky and find in your room, the best location for subs is beside the front L/R, but for most setups, that won't be the case. One of the primary reasons to use subwoofers is the ability to place them in the optimal locations in a given room. In the dozens of rooms I've measured, setup, and done EQ for, I've never had the best location for dual subs be next to the mains. Given that, a crossover at 80hz or lower avoids localization of the sub's output.

Bingo!

 

[pinnahertz]

Boy! That article succeeds in making the subject overly complicated! I need a nap just looking at it!

Well, it is complicated. The article is detailed, but accurate.

 

[bigshot]

I'm glad I hired a home theater tech who knew everything he needed to know, but didn't see the need to do an info dump like that on me. He just placed my sub, showed me the places that might be alternatives, and told me to experiment and find out what worked best.

 

[abm0]

I have no idea where you came up with 25%. It's a much bigger deal than that.

It's almost halfway down the page, at the end of the first post and then in the next one where he gives you diagrams of 2-sub and 4-sub placements - it's a recommendation quoted from Harman Audio's Todd Welti. It's basically 2 subs along the front wall (behind the mains), each at 25% of the room's width away from the side wall. (Technically, it's "at least 25%" according to the theory up the page, but it's a good starting point for getting things into non-catastrophic territory , and then you can fine-tune from there.)

 

[pinnahertz]

I'm glad I hired a home theater tech who knew everything he needed to know, but didn't see the need to do an info dump like that on me. He just placed my sub, showed me the places that might be alternatives, and told me to experiment and find out what worked best.

Last I looked this forum was "Sound Science", though I do get the impression that sometimes it's...well...not.

 

[bigshot]

You can use science for practical purposes and not be more interested in science than the music itself. The science rabbit hole runs just as deep with absolutism and irrelevancy as the snake oil one does.

 

[pinnahertz]

You can use science for practical purposes and not be more interested in science than the music itself. The science rabbit hole runs just as deep with absolutism and irrelevancy as the snake oil one does.

Wow. I'm not too sure how to take that. Except to say I doubt you'd be enjoying your music as much if someone weren't jumping down the science rabbit hole for you first. I'm not sure why you'd think it's irrelevant. Perhaps all the science necessary to enjoy music is that of a wax disc and a horn. Well, not for me, but some.

I try hard to avoid being so presumptuous as to assume anyone is more interested in one thing than another without actually asking them.