How does adding a second subwoofer improve your systems SQ?

And is it the same as the first one?

That would be the way to go, you wouldn’t have different left and right main speakers.

And don’t run them of the "sub output" if using a HT amp, set the programing to "no sub" and set your left and right mains to large and get the signal for your subs from left and right main pre-outputs

Or if using a normal stereo pre amp use these on it’s L & R outputs to supply both your poweramp and your subs
https://www.ebay.com/itm/Valab-Gold-Plated-RCA-Y-Splitter-Adapter-1-Male-to-2-Female-RCA-Adapter-1pcs/283760200309?hash=item42116d0a75:g:RXwAAOSwGBhaYNGt

Cheers George

Sunshine in Sydney, our water out of the tap is one of the best anywhere, very drinkable and better than nearly all bottled water, better than the stuff you have coming out your tap.  

geoff your are the original, that's why it's soooooo good giving it to you.

Not worth the angst.

25+ years of acoustics with personal contacts with many of the leading people in the field, a bunch of peer reviewed papers, a deep understanding of the science of sound, psychoacoustics, and enough interaction with the research community, often helping to design experiments, and well beyond the need to prove anything to anyone in my community.

Wow you really like throwing that one around don’t you, a shrink would be itching to get in on this one.
https://forum.audiogon.com/posts/1955883
https://forum.audiogon.com/posts/1955879

Half as many as I have, and I don’t really care what you have sunshine.
Fact is you benefit greatly from having two L & R subs instead of one mono’ed one. And many others hear the same.

So the left plays for 5 seconds and the right for 5. You still said it took 10 seconds, i.e. one complete cycle.

Yes one cycle, and you have a problem with that, "clean up aisle 4", can’t see the forest for the trees.

you have easily detected 100Hz bass frequencies in 10 seconds (why not instantly?)

Really??
Because the left plays for 5 sec then the right for 5 seconds, keep doubting and "you’ll be the looser" on this one.

If your eyes were closed, how did you know which was left and which was right, as opposed to just noticing a difference?

Same as you can tell left from right with eyes shut for anything heard.

What speakers/amplifier?

Just search for what I have as my main system
It’s the family TV room, HT setup, not my main audio room.
Elac FS-249
Marantz SR5014
2 x Yamaha linear amps, servo controlled, YST-SW305 classic subs xover at 60hz.

markj941 OP
Thanks ggc. I just ordered my second sub. Actually, thanks too all
that contributed to this discussion. It was informative and at times entertaining.

Good for you, getting the second sub.

I just did an experiment last night with myself my wife and son, where I played an alternating left to right 100hz sine wave for 5 seconds in each channel for a total of a 30sec run only through the L and R active subs, the main speakers amp amp turned off.

All of us with eyes shut could easily detect which side of the room the 100hz sine wave was emitting from within the first left to right change over in 10sec!!!.

This is proof that digital with it’s over 100db of channel separation will be stereo in the bass to your ears if produced by the recording engineer, and you’d be surprised just how many are.

Like I said before, I have many cd’s where you can hear the very low bass from just one side. Another good one is Brian Bromberg’s "Wood" double bass’ist

It’s better to have 2 subwoofers powered individually from left and right channels, "not from the single rca subwoofer output" if using a HT pre or amp.

Cheers George

markj941 OP

If members here that are pro one sub, and running it off a HT sub output.
Forget that single HT preamp sub output, get two subs run both subs from the main L & R preamp outputs 
You will find if you have two subs and in the HT programming "set the mains for large" with "no sub" picked, then cross the 2 subs in at where your mains fall off, get the phasing and level right ect.
Your in for a treat from what can come from active proper stereo setup bass bins.
Your mid sized floor standers or large book shelves will have the scale of sound that you only get from big floor standers like Wilson Alexia Max Alex ect.

Cheers George  

I get exactly that effect using only one sub in my bedroom system.

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.

I done the a/b with 1 mono vs 2 in stereo. And my subs are at 50hz 4th order, and the difference is huge.
Anyone who mono’s their bass below 100hz is ruining many albums that have been recorded in stereo down there.
  
It may not matter to the vinyl crew so much because they’re lucky to get 10db of channel separation down that low from their phono cartridges, so they are basically listening to mono anyway.

markj941 OP
How does adding a second subwoofer improve your systems SQ?

Amazingly so! because bass is done in stereo on more albums than you think.
People that use one subwoofer have no idea that they’re screwing up any stereo imaging that the bass has. You need two subs L & R close to the mains if you are to faithfully reproduce what the studio recording engineer wants you to hear.

I have many albums (CD’s) even from the 80’s 90’s that have <100hz bass notes that come out of either left or right channel. So to mon’ize these recordings into just one mono sub is not what the recording engineer wanted you to hear.

EG: Just listen to the second last track "It’s A Miracle" on Roger Waters "Amused to Death" at the end there is a kettle drum roll that rolls around the room on the ground from right to left and back again. If you had just one sub it would ruin that mesmerizing effect totally.
And the harmonic structure of bass notes like this above go right up into the midrange
Another that comes to mind is Ricky Lee Jones self titled album, it also has tracks where the bass only comes from one channel or alternates

Cheers George