I'm tinkering with the idea of setting up a near-field sub-woofer behind the (single seat) listening position. The context is that in-room measurements that I've done with the microphone being 10 to 30 cm from driver has all shown near flat results - so I'm reasoning that this would be a simple method to getting near flat response and, at same time, reducing distortion as a result of running the sub at a lower volume. It seems as if the downsides are the odd looking arrangement of sub right behind the seat and potential for localisation - although the latter would seem manageable given that I'll be using a digital X/O at 60 to 80 Hz. Has anyone got any real-world experience with such a set-up? Or, accepting that this set-up won't work for a lot of scenarios, am I missing anything about it's application for a single set set-up?
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(Very) near field sub-woofer
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No personal experience, but it has been discussed at DIYAudio.
digitalfrost
Major Contributor
I'm listening in the near field and experimented with subwoofers. I was never happy until the subs were on the desk, next to the satellites. Even under the desk was locatable for me, and I doubt you'll be happy with a setup that puts the sub behind you.
Crossover topology makes a big difference, you want at least 24db/oct LR or possibly more. And you probably want a crossover frequency below 80hz...
Crossover topology makes a big difference, you want at least 24db/oct LR or possibly more. And you probably want a crossover frequency below 80hz...
Dr. Toole did it 50 years ago.
https://www.avsforum.com/forum/89-s...aker-what-science-shows-176.html#post58636456
https://www.avsforum.com/forum/89-s...aker-what-science-shows-176.html#post58636456
carlosmante
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Many folk do it to get more tactile feel from their sub. I have not expect briefly and it does do that. The rule of thumb in general is to keep anything in front half the diameter of the cone away but many pix I have seen violate that...
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What does this mean? Is it that, if one has a 15"driver, then there should be 7.5"free space in front of the driver? If so - and presumably the reason that you mentioned it - is that this means that a smaller sub might be better for this purpose?
This is outside my area of expertise (as if I had one
). But, based upon some exchanges with folk who do know what they are talking about, and a foggy memory of a grad acoustics class or two decades ago, the rule primarily relates to waveform coalescence and reduction of (very) near-field compression from the boundary. Reading between the technical babbling my guess is that it does not matter for a sub used for tactile response, and I suspect how much it matters even for normal propagation is questionable for a subwoofer. I think you'd want enough to give the cone to move without fear of striking anything plus a local air buffer region, maybe a few inches, but probably do not need more than that.But we really need someone who actually knows to chime in; I'm too tired to dig up my old text and try to figure out the impact on the driver (cone) from a boundary so close.
I would not use a smaller sub, especially for tactical response, though they do make physical shakers (e.g. ButtKickers) for that.
I'm playing with this idea, my goal is to have enjoyable bass at the listening point without pressurizing the room to not annoy the neighbours
I tried with a single hanging driver but I had noticeable SPL everywhere in the room, not good
However placing two drivers cone-to-cone works really great, it haven't made proper measurements yet but with on my phone (Spectroid app) I saw 20 dB less SPL in the room than in front of the assembly
I have to optimize the spacing and the angle, but I liked what I had on the picture (maybe 20°), good tactile sensationswhile keeping low amount of bass in the room
I will also try to close the space between the drivers to only leave an aperture pointing to the listening position. It should give more tactility but I don't know what the impact will be on the room pressure
I tried with a single hanging driver but I had noticeable SPL everywhere in the room, not good
However placing two drivers cone-to-cone works really great, it haven't made proper measurements yet but with on my phone (Spectroid app) I saw 20 dB less SPL in the room than in front of the assembly
I have to optimize the spacing and the angle, but I liked what I had on the picture (maybe 20°), good tactile sensationswhile keeping low amount of bass in the room
I will also try to close the space between the drivers to only leave an aperture pointing to the listening position. It should give more tactility but I don't know what the impact will be on the room pressure
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Looks like you did some homework and nearfield position is optimal from FQ response POV, so that is a great start. The only thing that could work bad in that setup is if you are pushing your sub to a point of tactile response - which would obviously come from behind. While you can't (at least IMO) localize 60 or 80hz soundwave, you can definitely feel the pressure the sub produces when it turns tactile at MLP. You can probably work around this, if issue at all, by making it less nearfield if that is possible in your setup.
I do have real life experience with this type of setup and worked in the past with one sub, albeit my setup is a bit different nowadays and subs managed to multiply. Don't think you need to be worried about setup looking odd. At least I don't
.
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Woofersnoofer
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Love nearfield subs, one suggestion though is to use MSO and use multiple measurements for the mlp. I use 4 with a lower weighting for the 3 beside and in front of the mlp. Also i suggest putting a high pass filter on there to reduce localization through structure born noise. I use a LR4 at 15hz.
Also decouple the subs and make sure your couch isn't rattling. If you don't do this you might get the sensation of the sound coming from the front but a delayed resonance from the back, i found it distracting personally.
But with these steps i am very happy. There is basically a "bass bubble" around the couch and walking around the room you just hear some room modes which won't bother the neighbours. Going upstairs or to different rooms i don't hear any bass. I reckon your neighbours will be happy with this arrangement as well as you since it is excellent bass.
Also if you lean back you get super bass mode, but lean forward and you lose it. Obviously hehe.
Edit: Also take care of self noise from the sub and adjust the gain accordingly, maybe lower a bit on the plate amp and boost a bit in the minidsp if you have to.
Also decouple the subs and make sure your couch isn't rattling. If you don't do this you might get the sensation of the sound coming from the front but a delayed resonance from the back, i found it distracting personally.
But with these steps i am very happy. There is basically a "bass bubble" around the couch and walking around the room you just hear some room modes which won't bother the neighbours. Going upstairs or to different rooms i don't hear any bass. I reckon your neighbours will be happy with this arrangement as well as you since it is excellent bass.
Also if you lean back you get super bass mode, but lean forward and you lose it. Obviously hehe.
Edit: Also take care of self noise from the sub and adjust the gain accordingly, maybe lower a bit on the plate amp and boost a bit in the minidsp if you have to.
There should probably be a link like this(?) https://www.avsforum.com/threads/ho...38828/page-264?post_id=58636456#post-58636456
On topic - I use the exact opposite (as far as possible in a normal room) solution.
In the indefinite future, when I'll add subwoofers, I'll probably try listening in a very near field.
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olds1959special
Major Contributor
In my bedroom near-field setup, my LCR subs are 2 feet in front of me facing towards me, along with the monitors on stands above the LR.
My sub is not behind me but I am basically sitting next to my sub here.
After setting it up so the sub and speakers sum up nicely crossed over at 80Hz I have to use in room EQ.
Before and after EQ in nearfield using MMM and all channels playing pink noise, purple is after correction:
Looking at measured vs predicted shows that everything is as expected:
Surprisingly good results, the dip between 200Hz and 300Hz is due to my room/speaker placement.
Zero problems with localization as expected with a crossover at 80Hz.
Edit: some trouble with uploading the measurements.
After setting it up so the sub and speakers sum up nicely crossed over at 80Hz I have to use in room EQ.
Before and after EQ in nearfield using MMM and all channels playing pink noise, purple is after correction:
Looking at measured vs predicted shows that everything is as expected:
Surprisingly good results, the dip between 200Hz and 300Hz is due to my room/speaker placement.
Zero problems with localization as expected with a crossover at 80Hz.
Edit: some trouble with uploading the measurements.
Having a sub right behind your listening position is a purely valid method to get the most bang for your buck, but it does have a few drawbacks:
• You can’t set it up for stereo so you can’t use it alleviate the main speakers from having to produce low frequencies below 200Hz and get the dynamic headroom improvement and distortion reduction that offers
• It will only work optimally in that one spot
• The high-pass filter needs to be below set below the room modes so, maybe, 80Hz, tops, is your highest possible crossover frequency and needs to be at least 24dB/octave
• It’s only ideal in that one listening position… literally, don’t move even a few feet
• Your main speakers need to be time-aligned and probably concentric to guarantee a good sound stage
The upside if properly used:
• Less early reflection artifacts in your listening experience
• If the sub is a sealed design, you can EQ it to give you lower frequency response from your sub (within its excursion limits)
• Can be made optimal for a cubby-hole setup where square footage is small… if that’s the key issue, it can work
It really, though, is a bit like having your head in a vice to get the best results. Literally, don’t move a foot in any direction from the mains. Using a center speaker can help alleviate that problem, but that’s another topic.
If you’re trying to use a single close-field sub with a standard room topology, it will work OK, but, again, it’s only good for that one spot.
Stereo subs offer better in-room sound as well as improvements in distortion, dynamic range and room response optimization that a single sub can’t offer.
Designing a system is always an exercise in trade-offs. For this topic, you have to think more about the system of the speakers/room interface and much less about just the subs.
Just so you know, you can hear low bass in stereo. It’s your room that screws that up.
• You can’t set it up for stereo so you can’t use it alleviate the main speakers from having to produce low frequencies below 200Hz and get the dynamic headroom improvement and distortion reduction that offers
• It will only work optimally in that one spot
• The high-pass filter needs to be below set below the room modes so, maybe, 80Hz, tops, is your highest possible crossover frequency and needs to be at least 24dB/octave
• It’s only ideal in that one listening position… literally, don’t move even a few feet
• Your main speakers need to be time-aligned and probably concentric to guarantee a good sound stage
The upside if properly used:
• Less early reflection artifacts in your listening experience
• If the sub is a sealed design, you can EQ it to give you lower frequency response from your sub (within its excursion limits)
• Can be made optimal for a cubby-hole setup where square footage is small… if that’s the key issue, it can work
It really, though, is a bit like having your head in a vice to get the best results. Literally, don’t move a foot in any direction from the mains. Using a center speaker can help alleviate that problem, but that’s another topic.
If you’re trying to use a single close-field sub with a standard room topology, it will work OK, but, again, it’s only good for that one spot.
Stereo subs offer better in-room sound as well as improvements in distortion, dynamic range and room response optimization that a single sub can’t offer.
Designing a system is always an exercise in trade-offs. For this topic, you have to think more about the system of the speakers/room interface and much less about just the subs.
Just so you know, you can hear low bass in stereo. It’s your room that screws that up.
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