Sub placement

Greetings all and thanks in advance regarding this question.

Go to the “about” page to see my equipment and room:

I have had the same equipment more or less for 30+ years, excepting the sub, which was added 7 years ago. The only other major change has been the room. Three years ago, I moved from a lively, noisy lower Manhattan loft of 41 years to a room that has walls and ceiling insulated with 6” to 17” of rockwool covered by burlap, snd 7” of rockwool under the floorboards between the joists. This made a decided improvement.

In spite of all the insulation, the room, with its weird shape - two dormers and a gable - does present some challenges.

I have never been happy with the sub placement.

I had been following the advice of a friend who worked as the sound engineer at the UN. He said to put it where you sit, walk around the room until you find the spot where it sounds best, and then put it there.

There was never a spot where it sounded best. A few that sounded better, but did not stand out in any way. I would try one for a few months, then tire of it and try another.

Over the weekend, I spent a few hours cleaning out the dust in the amps, resetting the tubes, rotating the Altec drivers in the cabinets, etc.

For some reason, I thought that, hey, I never tried putting the sub behind the listening spot. So I put it under my desk, which is about 3 feet directly behind the armchair where I sit to listen.


Anyone have any experience with the sub behind the listening spot? Is this weird or actually not so uncommon?

Anyone venture a guess as to why that would work? A recording studio friend who I thought would make more than an educated guess said to just file it under “hey, it works, don’t think too hard about it, just sit back and enjoy!”

I suppose “home theatre systems” with their half dozen or more speakers around the room do this all the time, but I’m not getting why putting everything from 20 to 70 behind me and everything from 70 to 20,000 in front of me would not only help make the bass more textured and authoritative, but also help open up the rest of the soundstage: make it feel airier, clearer and more detailed.

The downside is that I now feel like I’m sitting on the stage instead of in front of it. I’m finding that dialing the phono-stage back and forth helps with that, as does dialing around the BME Sonic maximizer (don’t laugh: they are analog, and they work), so I think that will eventually resolve itself.
One sub is always difficult to place.At least two are needed to help balance out the peaks and nulls.My two are both behind the listening position in opposite corners.
"The downside is that I now feel like I’m sitting on the stage instead of in front of it."

Why do you think that it? Can you actually hear or localize the subwoofer's location?  It may be bleed over 80/90 Hz that allows that. I'd try low passing a bit lower (40-50Hz for my combo). All of my deep bass sounds like it comes from the front soundstage.

It is nice you are experiencing the 'air' that a subwoofer can give.  I'm with jtcf in that I currently use 3 asymmetrically placed subs and love it far better that my more expensive single sub (gone). I'd like a fourth too.

Thx jtcf.

I have a second Velodyne ULD 15, but these things are big enough (don’t forget the huge cabinets that the Altecs are in), and this one already can be easily felt on the ground floor (ground, 2nd, 3rd, attic), yet I wasn’t getting the sound quality that I was expecting.

I’m waiting for the SVS Soundpath Feet to arrive.

I don’t hear the sub’s location. When listening to Bill Evan’s “Waltz for Debby” the bass is in fact coming from the front of the stage off to the right for example. But the piano is now very nearly in my lap! 

The Velodyne crosses over at 70 and is fixed there, I can’t adjust it. It has a servo-processor/controller and it’s own amp.
I suspect you’re getting the bass delivered at two or three different times.

The floor still transfers the bass waves which are quite long, FASTER than the drivers do through the air. Wood or Stone are quit good sound transfer materials. Wood even more so for bass.

Your getting the bass from the mains, and the subs coupled to the floor. Then the bass from the actual drivers and reflection point via air.

You DECOUPLE the speakers, things will really start to make sense..
In stead of the whole floor being a huge bass driver all muddled up. Everything cleans up and for the first time LOWER distortion in the BASS region.. It can be really eye opening when you go from 20-30% distortion to 5%

The only waves from that point forward are air bound and reflection points. The decay rate speeds UP. The bass frequencies become much more coherent. The boom is gone the mud is gone.

I also suspect the rest of the house will quiet down a bit.. You’re not funneling the BASS through the wooden rafters and studs, they do a good job of moving harmonics through the house..

Speaker placement will probably change a little from the old, just a bit...Getting the depth and width of soundstage is going to be easier.
Get the piano out of your lap.:-)


Thx, I suspect that the feet that I’m waiting for will help. I had wooden floors in the loft but the mechanical transmission wasn’t as much of a problem as the reflections were. 

Speakers in the front: I guess I’m old old old school. Not quite victrola in the corner old, but definitely showing my age. It just never occurred to me to put the sub behind the sweet spot.
Thats a coincidence!  I have a really a bad bass null right where my listening position is.  Couldn't fix it for the life of me.  Tried putting my single sub 3 feet directly behind my listening seat and voila!  Sounds great.  I then started playing with placement. Moved it an inch this way, an inch that way, adjusted the crossover…. Got her dialed pretty good now.  Putting 3 GIK monster bass traps and 1 244 bass trap on the walls by the sub further improved things.  I’m using a vdlodyne hgs 10 on an isoacoustic stand and magnepan lrs speakers.

But yeah, subs behind you work well I guess 😀
How have you set the phase delay on your subwoofer?. I have a feeling that the reason you like the placement (further back from the speakers) now is because you've got the phase delay matched at that distance so that the subwoofer signal is in phase with the fronts (albeit one or two cycles later)
Interesting. I just recently purchased a 2nd JL Audio E112 and had pre-wired for that sub to be behind the listening position. OMFG - the result is amazing. The soundstage is much much more 3-D like I am walking on stage as I approach the front speakers. Surprisingly, the improvement is throughout the frequency range and there is huge air between all  instruments now. I’ve been working on my system for about 5 years now and this is probably the biggest improvement I’ve had (upgrading my Node 2 to the Mytek Manhattan II is the other one that gives it a run). 
At least for the moment I feel like my system is “there” and I have no urge to upgrade further (did I say for the moment? 😎). 
I read an interview with Dr. Hsu of Hsu subs where he stated the best place for a sub was behind the listening chair. Works for me. You mentioned listening from your desk. I found that ccktail tables (flat surfaces) anywhere in the listening area mess with the imaging. I've moved a table about a foot left and right and the vocals would move accordingly. Said table is gone.
I share a similar experience. Tried the "crawling" method trying to find a good placement for the sub according to what I could hear. But I could never find a location for the sub that sounded good in the listening position. This method may work well in some cases, but not in my room at least. Maybe it works better with multiple subs?

Anyway, I took another approach. As my room suffers from room modes along the listening path and especially at one frequency around 31 Hz, I decided to try to cancel out a high pressure area caused by this room resonance. I used a sinus generator that is a part of the RAW audio measurement PC software to generate a 31 Hz sinus signal. Connected the Laptop to a USB DAC, amplifier and speakers. I found a high pressure area just few feet behind the listening position. I placed the sub there. Then I listened at this location of the sub and fine-tuned its position, level and phase so that the sound pressure in this position was similar to other non-resonant frequencies. The possibility to fine-tune the phase of the sub was an important feature to be able to cancel out the pressure. I should add that I use floor standing speakers that goes down to about 27Hz -3dB.

Finally, I got good base in my listening position without using any bass traps (tried that before with minor success). Later I verified the frequency response in the listening position using a measurement mic and again the RAW software. The frequency response in the lower end looked really good with the sub and the settings I have made by this method.

The only control on the 15” Velodyne ULD II is a volume control. That’s it. It is set 50% lower now.

I have a BBE282ii to adjust the phasing, one for each channel, but those are between the preamp and the sub’s servo/amp. The sub’s servo allegedly has a computer that makes 3,500 adjustments per second based on feedback coming directly from the driver.

I am not familiar with the technology that you are using. I’m just glad a light bulb finally went off in my head about putting it behind the “sweet chair”.

I thought: the sub sounds the best in its old spot between and slightly behind the mains when standing next to it, so why not move it next to the chair? Makes no sense to put it in front of or to either side, so it had to go behind. 

Not that the logic I employed here is in any way correct.

A distinguishing feature of the room shape is that it’s not rectangular. It’s two triangles cutting into each other, one larger (the overall roof), the other smaller (the gable). And then there’s the two dormers.
The best place for subwoofers is in corners. Ideally you would use two subs in corners flanking the main speakers. The subs are most efficient in corners and this location also reduces some room interaction. The only problem is that this will probably not match the main speakers in time. The bass from each speaker and subwoofer has to arrive at the listening position at exactly the same time for the best transient response and impact. The best crossovers time the sound coming from each unit then delay the early arrivers to match the late arrivers. You can also do this with a calibrated microphone and computer program by measuring group delays and moving the main speaker to get them as close as possible if you can.

Your comment is consistent with the rational behind the coaxial mains: the tweeter and woofer signal comes from the same point source. 
No “corners” to put the sub in at the moment. 
So much to discuss regarding subs…
technically (if your crossover is set correctly), the ear has no real ability to determine where the bass is coming from. However, that is over-simplistic. Best to allow the longer, low frequency wave have the longest part of the room to develop and pressurize the room. I have mine slightly out of a corner, off to the left from listening position, and aimed into the longest dimension in the room - works great, and deep and present bass is there. 
I have two of my subs as Mijostyn suggested but put 1/3 to a half behind each of the front speakers. Another friend who has the JL Audio F212 did the same thing. I have two F110 subs. I know it is expensive but the JL Audio CR1 crossover is amazing. Think about it you get to crossover the front speakers and the subs to work together as one system. It is $3k and you need it to go between your preamp and amp. If you have separates then try this CR1 out. If you don’t JL Audio recommend setting the Sub crossover at 60 hz. This is a great blending point to get a more flat response. With the CR1 crossover I have the crossover set to 70 hz even though my main speakers go down to 25hz. My friends Revel Salon 2s go down even further and he has the same setting. You cannot believe how good your speakers sound when you remove the heavy lifting. If you are in the Chicagoland area this store lets you try before you buy.
Luckily JL Audio had the CR1s in stock so it only took a week or so to get one. This crossover works with RCA and XLR and has a HT bypass. Buy once cry once. They also carry the new KEF subs that play down to 11hz but I also have 2 RELs to round out the room. 
The JL Audio CR1 crossover consistently gets raving reviews. Perhaps one of the best components to get a seamless speaker, sub, room integration.
I have posted about the CR1 before. It really can help with several of these problems that occur when blending a sub. I haven’t even used the JL Audio room correction because the CR1 works so well. Maybe I didn’t need the F series. I could have gone with the E112s and saved serious money. I do have to say the F series is so good it keeps up with my main speakers so easily. The other cool thing is the XLR and RCA are separate systems so the next thing is hooking up the RELs with the RCA connections. 
if you have Maggie’s and running separates. The CR1 is a must even if you are running a crossover on them. They should be crossed over at 80hz at -24 db. You can then crank them without distortion or damage. I really want a pair of LCR to play with. Waiting a year for speakers is a long time. 
Keillor: the Velodyne ULD 25 is floor firing. I can’t “aim” it in any direction in the way you suggest.
Nothing wrong with a downward firing subwoofer. You can't really aim a subwoofer. They are in essence omnidirectional. You want to get the driver as close to a room boundary as you can either a corner or a wall/floor intersection.
unreceiveddogma, I not sure the analogy of a coaxial driver works well. Just because drivers are coaxial does not mean they are time aligned. The subs and mains are in entirely different locations. Although the vast majority of systems are point source, some are line source including the subwoofers. As an aside, many have never been exposed to a line source system. They are quite different in several regards. The next time you at a show see if you can find one to listen to.  
My two REL subs are down firing as well. I had initially put them behind the two front speakers tucked in just behind the speaker. This created a really great bloom or sound stage. The reason I upgraded was because I wanted front firing and a little deeper range. The REL T9s are so good I kept them. Plus the RELs have three different ways to input so it has a separate LFE for HT. The new REL T9is are front firing with a passive down firing. REL probably thought the front firing was a better approach for music. Either way I will be testing putting a sub right behind the listening area. 
It is usually always best to have a sub or subs two feet from the plane of the main speakers to keep the sound attached to the front stage and in time with the notes and beats of the music for the most natural sound possible, but if it sounds better behind you, so be it, but the most natural will be close to the main speakers for sure
speakermaster: I had it close to the mains, in a corner behind a main, in a corner behind the other main, between the mains, between the mains forward a bit, between the mains backward a bit, against one wall about half way between me and the mains (couldn’t do against the other wall, the stairway is there).

Three feet behind the listening chair is blowing them all away. There is a slight loss in some detail in the midrange vocal area, more than made up for in detail in other areas and an overall naturalness.

The rubber feet arrived, they are making a difference also (the piano is nearly back where it belongs).