Under ideal circumstances most kinds of speakers are placed well into the room, free from reflecting objects. The same applies to the listening position. However, in the real world couches are often placed right against the wall. If the listening position is so close to the rear-wall, you'll get a very strong and very early reflection. For low frequencies being seated so close to a wall actually has some advantages (fewer and less pronounced nulls, boundary gain), but for mid and high frequencies I only see problems.
How bad is this reflection? Might it in some way be of advantage?
If you wanted to get rid of it, how would you do it? Because of the almost perpendicular incidence, a damping panel would have to be very thick to damp reflections to below the Schroeder-frequency.
How bad is this reflection? Might it in some way be of advantage?
If you wanted to get rid of it, how would you do it? Because of the almost perpendicular incidence, a damping panel would have to be very thick to damp reflections to below the Schroeder-frequency.
Recently I moved and in the new living room a setup with the listening seat against the wall is the only logical option. First I tried my old 10 cm thick damping panels behind the sofa, but although things improved, I wasn't totally happy with it. Since a couple of weeks I've got a big damping panel behind me, measuring 2m40 by 1m20 and 20 cm thick. I wish I could've made it even thicker, but this is as far as the girlfriend allowed me to go 
.
Measurements indicate that above about 500 hz it works almost as a black hole. Below that, its effectiveness diminishes. All in all I think it's a big improvement. Imaging is now much sharper and I experience less listening fatigue. However I do experience an effect in the low midrange I don't know how other to describe than 'phasyness'. It increases the perception of envelopment (which I think is generally good), but on some material it sounds a bit peculiar. It is not audible all the time and to be honest it's just a minor quibble, but still.
The bass might be the best I've ever had. As before (in my dedicated audio room) I'm using multiple subwoofers and EQ, but it was now a lot less difficult to get the bass very flat. Even without EQ I managed to get the bass within +/- 5 dB between 20 hz and 100 hz - so no significant dips and just one peak worth a mention.
So I actually think my 'problem' is pretty much solved. My solution however doesn't seem to be one for everyone. The positioning of speakers is discussed a lot on these forums and also in user manuals of speakers and such, but it seems a lot less discussion is dedicated to the listening position. Many (especially lay-) people have a couch against the wall. What might be a more room friendly solution to fit their needs?
.Measurements indicate that above about 500 hz it works almost as a black hole. Below that, its effectiveness diminishes. All in all I think it's a big improvement. Imaging is now much sharper and I experience less listening fatigue. However I do experience an effect in the low midrange I don't know how other to describe than 'phasyness'. It increases the perception of envelopment (which I think is generally good), but on some material it sounds a bit peculiar. It is not audible all the time and to be honest it's just a minor quibble, but still.
The bass might be the best I've ever had. As before (in my dedicated audio room) I'm using multiple subwoofers and EQ, but it was now a lot less difficult to get the bass very flat. Even without EQ I managed to get the bass within +/- 5 dB between 20 hz and 100 hz - so no significant dips and just one peak worth a mention.
So I actually think my 'problem' is pretty much solved. My solution however doesn't seem to be one for everyone. The positioning of speakers is discussed a lot on these forums and also in user manuals of speakers and such, but it seems a lot less discussion is dedicated to the listening position. Many (especially lay-) people have a couch against the wall. What might be a more room friendly solution to fit their needs?
i just tried my memory foam mattress out! I get the phasey comment, which is probably an artifact in stereo mic seperation being large in the recording room, and large crossover between channels at the recording stage.
With rock pop band type recordings i didnt notice the same, except on some vocal FX.
I would say that its there, but this rear reflection masks it. Removing the reflection reveals the phasey-ness.
Id guess you could be hearing lateral modes and relections, and their interèrance to direct radiation.
I would like to try what i used to hear recommended for inside vented boxes. An absorber on one wall of each plane. Got carpet? Thats one down. Rear absorber? Yep! I just need a lateral panel at the far end of the room and then to listen. Perhaps using another panel laterally would help?
With rock pop band type recordings i didnt notice the same, except on some vocal FX.
I would say that its there, but this rear reflection masks it. Removing the reflection reveals the phasey-ness.
Id guess you could be hearing lateral modes and relections, and their interèrance to direct radiation.
I would like to try what i used to hear recommended for inside vented boxes. An absorber on one wall of each plane. Got carpet? Thats one down. Rear absorber? Yep! I just need a lateral panel at the far end of the room and then to listen. Perhaps using another panel laterally would help?
Last edited:
it is easy to treat higher frequencies with 2"-4" of owens corning 703 type insulation placed, preferably a couple of inches away from your back wall. this will not help with your lower frequencies though. dealing with low frequencies needs space, money and expertise.
my suggestion is, 'get lucky'. i sit against the back wall in my tv room, and it sounds just fine, no special treatments
my suggestion is, 'get lucky'. i sit against the back wall in my tv room, and it sounds just fine, no special treatments
Last edited:
Absorber works, just make it thick enough and choose the right material. I recently moved to a new place and had to place sofa close to the rear wall. I constructed a ~100 mm thick absorber using rockwool (mineral fibers) and modeling shows it is effective down to low hundreds. There is an excel sheet available somewhere online and also this online calculator at Porous Absorber Calculator
Here's a some modeled results for 100 mm thick absorber placed at a wall using different flow resistivities. My panels use material with 12650 rayls. Around 10000 seems to work well for a broadband absorber of this thickness.
Porous Absorber Calculator - Results
Here's a some modeled results for 100 mm thick absorber placed at a wall using different flow resistivities. My panels use material with 12650 rayls. Around 10000 seems to work well for a broadband absorber of this thickness.
Porous Absorber Calculator - Results
That's probably a low(er) frequency room effect. Run a slow sweep. Do you get a lot of fluctuating directional sensations?
Since a couple of weeks I've got a big damping panel behind me, measuring 2m40 by 1m20 and 20 cm thick. I wish I could've made it even thicker, but this is as far as the girlfriend allowed me to go
Measurements indicate that above about 500 hz it works almost as a black hole
What panel did you use?
How you perform the measurements?
Yes! How did you measure that? I'd like to try it.
FWIW, my sofa is about 2 feet (60 cm) from the rear wall. I have panels on the wall that are 6" (15 cm) thick on that wall. They seem to work well, tho I do need some more coverage.
Great topic.
This is also my current listening situation.
Treating the room isn't an option (uni dorm room), so I tend to sit on my bed, leaning back on a pillow to listen to music. More comfortable than leaning on the wall, and the sound's better.
I do still have a strong resonance in the ~120Hz range - I suspect it's a standing wave as the wavelength seems to coincide with the room width.
I can lean forward and the resonance dies down somewhat, but the room is also very lossy in the bass - crank it up so you can feel it in one place, and in other places you'll think you're listening to 3" satellite speakers with no sub.
Hopefully a dedicated subwoofer will sort this out, and provide some more <40Hz oomph for parties too.
Chris
Treating the room isn't an option (uni dorm room), so I tend to sit on my bed, leaning back on a pillow to listen to music. More comfortable than leaning on the wall, and the sound's better.
I do still have a strong resonance in the ~120Hz range - I suspect it's a standing wave as the wavelength seems to coincide with the room width.
I can lean forward and the resonance dies down somewhat, but the room is also very lossy in the bass - crank it up so you can feel it in one place, and in other places you'll think you're listening to 3" satellite speakers with no sub.
Hopefully a dedicated subwoofer will sort this out, and provide some more <40Hz oomph for parties too.
Chris
I'll try that and let you know.
I used the fiber glass batts that were available at the local hardware store. The measurements were not directly on the panel itself. I just compared several measurements at and around the listening position before and after installing the panel. There are very obvious differences above 500 hz. At lower frequencies the effects are simply less significant.
Perhaps not, but in our room this is really the most convenient way to set up the listening triangle. I know many others with the same kind of setup.
Sorry about not getting back to you sooner - but you were right! There was some interference going on in the 100 to 150 hz range. That's fixed now. I'm running a pair of Keele CBT-like speakers and I've dropped the crossover to the subs to about 90 hz.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.