What to do when speakers can't be placed in ideal location?

[Epos7]

I have a room where the layout won't allow the speakers to fire down the length of the room. Instead, they need to be in the middle of the long wall, firing across the width of the room. I know this isn't ideal, but it's what I have to work with for the time being.

With that in mind, I'm wondering what acoustic treatments I might try to mitigate the less-than-ideal speaker placement. I'm not sure if diffusers or absorbers on the wall behind the listening position would be best. Additionally, I'm wondering if it may be beneficial to place the speakers fairly far apart.

As you can see the room has sloped ceilings. Currently I just have a few rigid fiberglass panels in two of the corners. I have a microphone on the way so I can start taking some measurements.

 

[Harmonie]

Some speakers like electrostatics's ML, don't like side walls, so that your set-up would be quite convenient.

 

[alex-z]

Your placement is actually pretty ideal. No strong side wall reflections, and there is a gap between the seating and rear wall for acoustic treatment. Maybe spread the speakers out a little and toe them in slightly for optimal stereo imaging.

I would start by placing absorption panels on your ceiling and rear wall first reflection points. 5.5" mineral wool panels are ideal, they can absorb far into the mid-bass region. I would also put panels between the speakers and front wall to reduce speaker boundary interference.

Diffusion is a niche tool for dealing with high intensity but narrow bandwidth reflections. If you have a specific problem frequency, you can build a quadratic diffuser specifically suited for it. Don't add diffusion without knowing if you need it.

 

[Blumlein 88]

What Alex z said. I've used Acoustat panels in just such a configuration which worked out nicely. Narrow sweet spot though.

 

[Vini darko]

What speakers are you using and do we have a spin for them?

 

[Epos7]

Diffusion is a niche tool for dealing with high intensity but narrow bandwidth reflections. If you have a specific problem frequency, you can build a quadratic diffuser specifically suited for it. Don't add diffusion without knowing if you need it.

Good to know, thanks! I'll focus on absorption.

I can make a 6" rigid fiberglass panel at 3 pounds/cubic foot for behind the listening position.

It's a hardwood floor and there is a large wool rug in front of the speakers, although it's not very thick. I may look to add a couple smaller rugs to cover some of the exposed floor.

 

[Epos7]

What speakers are you using and do we have a spin for them?

They're Epos M15.2 speakers. They have a 150mm woofer and 25mm aluminum dome tweeter. I doubt there are any spin graphs of them unfortunately.

I also have two Rythmik F12 subwoofers on the way.

 

[Marth]

Backwall reflections will hit you full force. I would try to acoustically deaden the backwall with very thick bass absorbers (20 - 30cm). You want the sound to pass by your ears as if it is a very long room with plenty of space behind your head. I also have such general dimensions and deadening the back wall made a major difference. This also has the advantage of muting the room modes in that direction. If you have dipol speakers (Linkwitz or Logans) the sidewalls are not involved at all anyway.

I have dipol speakers and bare sidewalls and not a single relfection is hitting my listening spot coming from the sidewalls. You might have to treat the opposite sidewalls so that your left speaker doesn't bounce of the right wall into your right ear. When you toe-in a dipol so that the null is pointing towards the 1st wall reflection there will be some energy present in the opposite wall reflection.

The tilted walls simply create more possible room mode frequencies in the upper part but in the lower part the parallel sidewalls will still cause the important standing waves.

The combination of good dipol speakers and broadband deadening the backwall can turn a small room into acoustically huge room when you close your eyes and detach your visial from your auditory sense.

 

[Marth]

You can seperate your speakers further from each other. Simply make a test and check if there is a hole created in the phantom scene between the speakers. Use "letters" by Yosi Horikawa and "Turn your lights down low" by Bob Marley for that. First allows to check if the transition is steady and second will reveal any hole. When I seperate my speakers beyond 2.55m it will rip a hole in the scene immediately.

 

[Marth]

Good to know, thanks! I'll focus on absorption.

I can make a 6" rigid fiberglass panel at 3 pounds/cubic foot for behind the listening position.

It's a hardwood floor and there is a large wool rug in front of the speakers, although it's not very thick. I may look to add a couple smaller rugs to cover some of the exposed floor.

Diffusion won't work for you in that small room. QRDs need distance. Otherwise they will create crazy effects which you don't want... In order to diffuse 450Hz and above you would need 1.2m distance at a minimum!

Just deaden the backwall completely so that no sound is coming back from there. Best and cheapest solution would really be to raise a artifical "wall" via a wooden frame and fill it with rockwool>layer to keep the particals contained>fabric which also absorbs the highest frequencies.
How do you expect to hear any room information in the recording when your own room masks them via a myriad of early reflections?

 

[Marth]

If you have a solid budget you can deaden the wall completely even with just 20cm thick broadband velocity basstraps + 2 AVAA C20 units on that wall.

In your case given that you have box speakers you should just try to absorb the first reflection points on the walls for sure. Remove the early reflections but allow secondary reflections and high order to develop naturally in your room. Try to break up the auditory scenery with bok shelfs standing lamps and so on. But do kill that first reflection. By killing I mean to get rid off it completely. Don't use 3cm thick absorbers as this would absorbe some parts of the spectrum but allow other deeper frequencies to pass. Your brain is powerful but it won't be tricked by that into thinking that the room is bigger. You need to get rid of the whole frequency spectrum from your 1st wall reflections. 20cm thick rockwool panels will do!

On the ceiling you could actually use qudratic diffusion! Make sure it is 2D so that you sent part of that sound energy back into the horizontal plane where you need it. Most energy in the first relfections is from 700hz and above so QRD will be fine here.

What works very well on first reflection points is the following arrangement! One 50x50cm absorbing panel sourrounded by 1D QRD for the sidewalls. It allows to kill the direct reflection but helps ins spreading the reflections of higher order...

Your room is small but it is possible to turn it into a nice sounding space for sure.

 

[Trdat]

If you have a solid budget you can deaden the wall completely even with just 20cm thick broadband velocity basstraps + 2 AVAA C20 units on that wall.

In your case given that you have box speakers you should just try to absorb the first reflection points on the walls for sure. Remove the early reflections but allow secondary reflections and high order to develop naturally in your room. Try to break up the auditory scenery with bok shelfs standing lamps and so on. But do kill that first reflection. By killing I mean to get rid off it completely. Don't use 3cm thick absorbers as this would absorbe some parts of the spectrum but allow other deeper frequencies to pass. Your brain is powerful but it won't be tricked by that into thinking that the room is bigger. You need to get rid of the whole frequency spectrum from your 1st wall reflections. 20cm thick rockwool panels will do!

On the ceiling you could actually use qudratic diffusion! Make sure it is 2D so that you sent part of that sound energy back into the horizontal plane where you need it. Most energy in the first relfections is from 700hz and above so QRD will be fine here.

What works very well on first reflection points is the following arrangement! One 50x50cm absorbing panel sourrounded by 1D QRD for the sidewalls. It allows to kill the direct reflection but helps ins spreading the reflections of higher order...

Your room is small but it is possible to turn it into a nice sounding space for sure.

I got a similar room, but its larger about 5 by 4 metres same orientation. I have left the side wall reflection points untreated(I dont have sidewall first reflections anyway), treated the back wall with 10cm rockwool from about ear height to the ceiling and a large absorbtive couch infront. The room has random panels throughout(decent RT60) with foil infront of the rockwool to keep the room alive and I have toed in my horn speakers to bring back secondary reflections to the listening spot.

I also have a large ceiling panel about 3 by 2 metres with a 30cm gap. You mention QRD diffusor on the ceiling refection point and curious how I can keep the absorbtion and add some type of diffusion. Of course practically speaking adding a diffusion panel might be difficult as the panel above is already made but technically speaking is there a way to add diffusion while keeping the absorbtion? Say, would you recommend a bad panel on top of the current panel or a QRD boxes with a certain pattern leaving some space across the panel to absorb?

Hopefully this will help the OP as well trying not to vear to much off the topic.

 

[Marth]

I want to keep my speaker side lively so I won't use absorption there. I don't want to remove only specific frequencies... Diffusion and absorption on the ceiling is easy. You place a absorber panel at the 1st reflection point and diffusing elements around it. So you 1st reflection is muted but secondary reflection are diffused and ideally pushed towards the sidewalls.

 

[Epos7]

Lot's of good info, thanks!

If you have a solid budget you can deaden the wall completely even with just 20cm thick broadband velocity basstraps + 2 AVAA C20 units on that wall.

Wow, I didn't know active bass traps were even an option; that's amazing! Those are going to be out of my budget for a while, so I think I'll focus on passive treatments. Do you think I should treat the entire back wall, or just the space behind the listeners? I likely can't go all the way to the ceilings due to the slope, but I could build some traps about 4 feet tall and space them 3-4 inches from the wall.

When you say rockwool what density are you referring to? I have on hand quite a few 48" x 24" x 2" panels that are 3 lb/cf. I could stack three of these to produce 6" (15cm) thick absorbers, or by stacking 4 I could make 8" (20cm) absorbers.

Hopefully with two subwoofers I can adjust the placement and use something like a miniDSP 2x4 HD to get nice bass response throughout the room.

You want the sound to pass by your ears as if it is a very long room with plenty of space behind your head.

I will make treating the rear wall the first priority. Following that, reflection points on side walls and ceilings. I wonder if I should apply any treatments to the front wall?

 

[Frgirard]

I have a room where the layout won't allow the speakers to fire down the length of the room. Instead, they need to be in the middle of the long wall, firing across the width of the room. I know this isn't ideal, but it's what I have to work with for the time being.

With that in mind, I'm wondering what acoustic treatments I might try to mitigate the less-than-ideal speaker placement. I'm not sure if diffusers or absorbers on the wall behind the listening position would be best. Additionally, I'm wondering if it may be beneficial to place the speakers fairly far apart.

View attachment 155038View attachment 155039

As you can see the room has sloped ceilings. Currently I just have a few rigid fiberglass panels in two of the corners. I have a microphone on the way so I can start taking some measurements.

Finding the sweet spot in the room - Gearspace.com

Something is not set up right. You have some kind of noise in the readings.

gearspace.com

 

[Marth]

Treatment will be needed in your room but I agree with Frigirard that you should first find the ideal positions in the current state. Knowing that the ideal positions are subject to small changes once the treatment is in place. This is due to the nature of combfilters. When you add absorbers to a wall you could remove create a null or peak as you remove the anti-phase portion of a potential hidden combfilter. Once you remove that part the canncellation doesn't work anymore. Optimizing the combfilter behaviour can be tricky and frustrating in a normal living space.

 

[abdo123]

You get a good pair of headphones.

 

[Marth]

Headphones are not well suited to truly create the auditory illusion needed to trick you into feeling as if you are there imo. Little natural head movements and all that. Your brain isn't stupid. Maybe if you sit extremely still and have headphones resting on your ears without any pressure. So far no headphones have been able to do that for me. Theory also explains that earphones have a high degree of spartial distortions and in-head localization is different.

When I close my eyes only loudspeakers have so far been able to create that illusion for me. For tonality they could be better but good speakers and a room where the reflected sound still has all frequency components also works well. You don't need to remove all reflected energy or diffuse it. In a living environment it is enough to make sure that the spectrum of direct and reflected sound is similar...

https://d-nb.info/970186762/34

 

[Trdat]

Treatment will be needed in your room but I agree with Frigirard that you should first find the ideal positions in the current state. Knowing that the ideal positions are subject to small changes once the treatment is in place. This is due to the nature of combfilters. When you add absorbers to a wall you could remove create a null or peak as you remove the anti-phase portion of a potential hidden combfilter. Once you remove that part the canncellation doesn't work anymore. Optimizing the combfilter behaviour can be tricky and frustrating in a normal living space.

When you say optimizing combfilter behaviour what do you exactly mean?

And can you also let us know where else would diffusors be suitable for such a small room with most of the walls close to the listening position? Is the ceiling pretty much the only place?

 

[Jim Matthews]

Most of these simple two-way designs sound best in a room with comfortable furniture. Before concentrating on wall treatments, get a nice couch.