Sub placement


Greetings all and thanks in advance regarding this question.

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

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.

Voila.

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.
unreceivedogma
Ddrave44:

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.
Andrs65:

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.
Mijostyn, 

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.