Subwoofers and Seating Position for Klipsch Forte iv's

You might look into Distributed Bass Array or Swarm setups.

What about reconfiguring the room to have the speakers on the long wall instead?

From your options I’d go with two Rhythmik F12Gs.  For placement and to excite room modes the least put one of the subs close to the walls at the midpoint of each of the front and back walls or the two side walls.  If that’s not practical, put them 20% of the way into the room from the front wall (7 feet in your room) and 25% into the room from the side walls (3.75 feet).  These are basic/general placement guidelines for a rectangular room from Todd Welti who’s a foremost expert on subwoofer placement.  The other option is to do “the crawl method” to find two places where the subs sound best from the listening chair and then set the volume, crossover, and phase as per these links…

https://www.audioholics.com/home-theater-connection/crawling-for-bass-subwoofer-placement

https://lifehacker.com/how-to-properly-set-your-subwoofers-volume-without-sh-1506136549

Just some thoughts and a couple ways to attack it.  Hope this helps, and best of luck.

My listening space - at approximately 18 x 15 x 8 - is markedly smaller (and less rectangular) than yours, but I faced the same problem. I, too, use Quicksilver tube amplification with a pair of Klipsch Belles - and struggled to find the best placement for a pair of badly-needed Rhythmik F12SE subs. (I realize this is all too big for the available space, but it’s what I have to work with. Plus, it makes for a nicely intimate "nearfield" listening experience). With the Belles placed along the "long" wall, I have each sub facing inward (across from one another) at the midpoint of each side wall (as suggested, I think, by @soix above). I experimented with them in the corners and, vice versa, on the long wall just inside the Belles . . . . neither of which sounded optimal. Since my "room" is a squarish formal living area that connects to the formal dining room and to the front foyer, my placement options were necessarily limited. Frankly, your Forte IV’s would be a much better fit in my space. Good luck!

I replaced a pair of excellent subwoofers (I will not mention the name/model) with a single RSL 12S (placed in between my Lascalas) and am thrilled with the coherence and dynamics of the combination. With your room, maybe a pair. Good luck. Always, MrD.

All your comments are great stuff, thanks!

@noromance - placing the main speakers on there long wall is not an option. Trust me, I have thought about it, including my wife's reaction! 

@souix - a lot to think about. I think the crawl method might be best. I have an opening to a stairs at one end and another adjacent space at the other end...It seems that is should be easier to find good placement for a listening chair rather than a listening area?

@tds3371 - I just can't get my head around the mid wall location. Probably need to better understand the physical properties of the sound waves and nulls?.

@mrdeci - Interesting that the one sub woofer is doing you good. Can you share why the new single sub is better than the two? Just too complicated with multiple subs for your space? Or the new one is just better fit to room? I was wondering if I should just start with one. I suspect that it would be am improvement, but would/could I be missing with two? Although most of what I am reading on forums is telling me two or more.

Do any of you have opinions regarding musicality of different brands of subs?

Do you think mating subs with horn speakers is more complicated than with non horn speakers? Read about that on forums and seem to be equal camps based on what I have read on this one.

Thanks!

a lot to think about. I think the crawl method might be best.

I completely agree and was hoping you’d be up for that.  The other placements are just general guidelines and may or may not work well/best in your particular room because every room is different, so the crawl method at least ensures you’re getting the bass tuned specifically for your particular room — it just takes a little more effort upfront, but it’s one and done and well worth it IMHO.
 

@ noromance  +1

1. I will second using a distributed bass array if you really want to improve low frequency quality.

2. I would also try moving everything further out from the front wall. Perhaps 8 feet.

3. If you do stick with two subs. Put them where they sound best, as opposed to where they look nice.

After reading OPs response, I think I disagree with Tony on every one of his points-  

1. Clearly there is a budget in mind as well as certain esthetic requirements that adding pile of bass speakers would be prohibited for multiple reasons. 

2.  Having speakers far out from the walls is seldom the best location, usually results in weak bass when applied to full range speakers, and ruins the feng shui of nearly any living space. The only types of speakers that I've heard that really benefit from being way out from the walls are dipoles. I have the Forte IV, 6-24in enough room for it's passive radiator.

3.  Subs, or more specifically bass, is omni directional.  They are also adjustable in output and phase so they can sound good in a location where they also look the best. 

The best audio systems that I've experienced are typically among the most visually appealing as well.  There is nothing worse then a carefully pieced together system that looks like a showroom in an audio store (the exception being showrooms that take the extra step to stage like a living room etc). If its in your home, make the system work around your space, not the other way around.    

Having speakers far out from the walls is seldom the best location, usually results in weak bass when applied to full range speakers, and ruins the feng shui of nearly any living space.

@perkadin  It depends what you mean by “far,” but go to any audio show or high-end dealer and the speakers are always well away from the walls unless they’re designed specifically to be near the walls, but those speakers are few and far between.  But point taken that going too far can result in negative results as well so it’s all about finding what works for someone’s specific tastes, speakers, and room.
 

Subs, or more specifically bass, is omni directional.  They are also adjustable in output and phase so they can sound good in a location where they also look the best. 

This is just factually incorrect.  To get subs to work best within a room they need to be placed carefully so as not to excite room modes and provide even bass response, and output and phase can’t fully correct for that.  Even if you use room correction that can’t do much if anything to improve room nulls — only proper placement can do that.  Just because bass is omnidirectional below a certain point does not mean you can just plop them anywhere — the room dictates where subs sound best and that just takes some work to get right unless you do something like a Swarm as mentioned earlier.

are you planning to match 2.5K subwoofers to 5K speakers that already have a lot of bass? 

@soix how exactly does one carefully place their subwoofer?  Do you move it all around the room, tweaking phase and output settings to eliminate bad choices?  Is it inch by inch or foot by foot?  Are you using music or sound tones?  What if you have two subs?  There are limitless permutations. 

Or do you simply find a spot that you think will work that also looks good and dial it in?  There's no need to be neurotic about it, you are talking about 20-80hz which makes up a very tiny slice of recorded music. And as I said earlier, for the most part it's omnidirectional. Tuning a sub is basically eliminating unwanted vibrations while getting sufficient output. If you have a big room like OP's you'll probably need a second sub.  

how exactly does one carefully place their subwoofer?

@perkadin There are programs designed to help like RPG, etc., but the crawl method I mentioned earlier is very effective and doesn’t require additional software, microphones, etc.

https://www.audioholics.com/home-theater-connection/crawling-for-bass-subwoofer-placement

If you wanna understand more of the theory of sub placement there’s a good intro in this video, but you can google Todd Welti on whose work a lot of this info is based.

https://www.youtube.com/watch?v=InwRYDzgEQk

So it’s not as easy as just plop them wherever they look good and change some settings to get really good bass in a given room — there’s just a lot more to it than that.

@grislybutter are you planning to match 2.5K subwoofers to 5K speakers that already have a lot of bass? 

Yeah, I guess I am. The Forte iv's are specified at 38Hz. The last speakers I had for any length of time were Thiel CS5i's that went down to 23Hz. I like the dynamics and sensitivity of the Forte iv's but I also think that, well, they are a bit thin and a bit off in tone. I am considering subs as a way to possibly correct for some of this without pumping bucks into more expensive speakers. If this does not work then it is on to Volti, Tannoy or who knows.

All,

I have purchased a SVS SB3000 subwoofer that arrived yesterday. With just the one sub, I can tell a difference; the sound is ...just more heavy, fuller, I guess. Initially it also sounded a bit boomy. I have it crossed over at 38Hz and am fussing with volume, phase, crossover slope, etc. All sorts of fun. The SVS app is nice as you can make adjustments while in the sweet spot. 

Have not done the crawl yet.

From what I think I can hear, I suspect that two subs would be better than one. Yes, bass is not supposed to be directional, but my impression is that, with the sub placed just inside of my right speaker, the bass is emanating from that side. Might just sound that way because of the visual...I have longer interconnects arriving tomorrow so I can move the sub around.

Stay tuned...

38Hz seem low, as you are using it between 18Hz and 38Hz? I went through a lot of pain for weeks with setting up 2 subs and I am curious about what I can learn from you.

@grislybutter 38Hz seem low...

Based on what I've read, I am trying it at 38Hz to 48Hz. The subwoofer is supposed to be able to go to like 18HZ. I realize that there is not a lot of recorded music that produces 18Hz, but after two days of messing with it; I can definitely say that the sound is a bit fuller. With some music, I believe I am hearing a bit more slam.

My presumption is setting the sub at a little bit higher than the Forte woofers, allows for reinforcement of the bass in the 38-48HZ./z region. I suppose this is where the extra slam and fullness originates. 

Of course, I could be completely wrong on this as I am no expert. I also suppose that the sub needs to break in? So then I get to adjust everything all over again?

I am still waiting on new longer interconnects to show up so that I can experiment  with the sub's position in the room, which will probably force me to start over again.?

The SVS instruction steps start with sub volume, then crossover point, then slope, then phase and polarity, etc.

I suspect that the trick is going to be frogging with it so that it blends with the Forte woofers. It is a fine line because it sure can go boomy and sound slow...  if I am  not careful. 

I went with a sealed woofer because I read a lot of comments that indicated a sealed sub does better than a ported sub with music. Having said that, I kept reading that Hsu subs are supposed to be "musical", but I believe that they are all ported!?

If I can get the one sub to blend, it will be an improvement. I can rationalize why two subs would sound better than one.

What I have read is that you should get the first sub to sound like you want and then work on the second one. Part of the process is getting the loudness right so that it does not overpower your speakers. Apparently, you have to reduce the first sub's volume when you add the second sub so that the overall loudness is correct with the speakers?

Now you know what I think I know! Please share your experiences with two subs to help me learn. Thanks! 

@dsper

here is my diary of my very simple and not at all sophisticated journey.

https://forum.audiogon.com/discussions/speakers-and-cables

There are obvious differences, such you have a big room and true full range speakers. The end of my story is that I just set it up as if I had speakers with an active sub at the floor level and I crossing over at 100Hz. 

That’s a good room dimension .

Set up on the long 35 ft dimension so there is a copious amount of space between you and the back wall.

Do you have a measurement mic? REW? If not, you may crawling for a long while and still probably mess something up.

If you don’t have measurement tools, try the following...Put the 2 subs along each side wall, 1 sub in front of listening position and 1 behind. Move each sub forward and backward from respective positions in small increments until a find the sweet paired spots along the side walls. Such paired placement will cancel out all the problem big nulls (for example, the widthwise ~37 hz, lengthwise nulls that might plague your spot). Perceptually, such relatively nearfield sub positions should also feel like you are floating in a uniform womb of bass...and provide just the right amount of tactile bass without it being distracting.

After you determine the right toe angle for speakers.... and with all that space behind you, you should be able to get some respectable envelopment and immersion from just stereo.

P.S. Also ensure that the subs you get have a variable phase knob, not some 0/180 flip switch (it is 2024).

@deep_333   Do you have a measurement mic? REW? If not, you may crawling for a long while and still probably mess something up.

I found the opposite far more practical. With the sub located at the listening position (as per Velodyne DD Optimization instructions) using the included measurement mic simply confirmed the location that sound best from the later version Velodyne DD Plus instructions crawl (or walk) test, avoiding any trial and error of sub position handling.