Sub placement behind listening position (not nearfield) - AVS Forum | Home Theater Discussions And Reviews
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post #1 of 4 Old 05-23-2018, 12:39 PM - Thread Starter
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Sub placement behind listening position (not nearfield)

Hey all,

I've been playing with REW, and while it obviously isn't the same as measuring actual in-room, the room sim is showing me that I have a nasty null around 55Hz if my subs are placed on the front wall, due to the length of my room and my seating position (neither of which can be changed). Back when I had the room up and running (we've been overseas for a while), I measured the null at about 60Hz at the listening position, and backing up to the back row made it go away.

The back row isn't a bad option, but it is right against the back wall so there is no separation from the rear surrounds, nor would there be any room for the 4 atmos overhead speakers, so I'd really like to avoid moving to the back row.

However, if I place the subs on the back wall in the corners, the response is much better (see attached).

Has anyone ever run their main subs behind the listening position (5-6' away)? I would imagine it just wouldn't sound right because the action would be coming from behind you, but maybe I'm just crazy. I will say that I can easily hear the location of the subs in the room, well below 80Hz.
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post #2 of 4 Old 05-23-2018, 01:31 PM
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I used to have two subs up front, and two in the back (all identical). Now I have all 4 of those along the back wall along with another sub up front. No issues I have seen, or heard? In theory the bass isn't localizeable from a sub, so it shouldn't matter where it is in the room. I have never really cared where it ends up, as long as the measured response is good. Cue people WAY smarter than me explaining things much better

Sean
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post #3 of 4 Old 05-25-2018, 02:23 AM
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Hi there, I'm a complete novice so take all this with a grain of salt, but for what its worth I have 4 subs arranged as follows...



Meausured they performs as follows:

Just sub 1 (SWR-1540):



Just sub 2 (SWR-1522D):



Just subs 3 & 4 (HiSAF):




This graph shows the combined result of all four subs playing (gold line) compared to side wall Subs 1 & 2 (blue line) and back wall Subs 3 & 4 (green line):



The gold line shows, in my room, that I get a flatter response overall from the side and back wall subs combined. To me, going to four subs made an audible improvement, bass seemed smoother subjectively, and I think from the sweep this is measurable.

It's also worth mentioning that despite the various distances of each sub to the MLP (center seat of back wall sofa) I have applied no delay. I have tried to add delay appropriately based on the subs relative positions but this just seems to add in big notches to the measured response in my room. I tried varying the delay up and down but coming back to zero delay seemed to get me the best result.

The big peak between 35hz and 70hz is not great however, but with a capable EQ like the DCX2496 this big peak can be pulled down somewhat to achieve something like this:



The response now varies by about 10db over the 13hz to 100hz range, where before it was more like 25db with the big 37hz peak. I made no EQ boost to achieve this.

Pulling this peak down made a really startling difference. I get heaps more tactile impact now - when wonder woman brings down the church tower you can feel it in your pants (not just cos of WW!). It also seems to reduce the very localising affect of sub 2's placement. Now the bass is kind of holographic, it just seems to come from everywhere, making the soundscape of my system seem much more spacious, a bit like being in a much larger room, like a full size cinema.

Overall then, for me, in my room/system, the back wall subs have been a success.

A final note I'd make is that being able to measure can really help. I have described how I learned how to measure in this very useful measurement microphone shoot out thread here on AVS.

Hope this is of some help.
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Last edited by Mazza; 05-28-2018 at 01:14 AM.
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post #4 of 4 Old 05-25-2018, 03:16 AM - Thread Starter
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Mazza,

That is a great help! I will have all the gear to measure once I get in the room. The big thing for me is that if I want to put the subs on the back wall, I'll need to build 2 subs in 1 box for space constraints, but if I want to split them, obviously I'd need different boxes.

What I think I may do is to use my existing sunfire to take room measurements at different locations and see where the peaks and dips are. That should help me figure out the best location for the 4 subs.

My biggest concern was localization. Maybe it's because I only have 1 sub now, but when I tried moving it around the room previously, I could easily hear where the sound was coming from and it wasn't pleasant.

Maybe with multiple subs that will become more holographic as you said. Worst case, I'll build some smaller boxes and just place them around the room to get a feel for the response and then make the final boxes once I'm sure
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