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Room treatment for a wide, rectangular room. Where to start?

Barry_Sound

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Hello everyone, I´m trying to learn about room treatment. My listening room is rather wide and I´m listening in near field. My room isnt "echo-y" when doing clap tests. However it sounds awful when recording the speakers in room.

Here´s a draft of the setup, not super accurate, just to give you the idea.

room1.jpg


The walls are blank. What i marked "stuff" is also reflective surfaces (furniture).

Floor is wood, mostly no carpet.

So … where, how would you start to improve?
 
Don’t be to worried about the recording of the speakers in room sounds awful, microphones are not an ear/brain system .
When you sit in the same position your brain does a shedload of ”processing” ignoring some things prioritise others.

I would recommend Floyd Toole’s book ”sound reproduction 3rd edition ” . A good popularisation of a thorny subject.

I’m no acoustics expert.

I can say that if the room is going to be a living space you probably want to use EQ (DRC) for bass issues any room treatment that’s actually effective in the bass is very large and thick and intrusive .

I can also recommend REW and an UMIC with usb connection for measuring your room .
It helps tremendously just guessing and try stuff is a big time waster.

Consider subwoofers .

Consider for example an mini DSP or WiiM Ultra or other product that does some EQ etc or use your computer.

What are the distances and dimensions in your picture ? Hopefully the speakers are not wider apart than your distance to your listening position.

You done some good stuff already, speakers are not to close to sidewalls and your not sitting against the back wall ( I do for practical reasons in my small room ).
 
You need to speak to acoustic specialists imo. I also have a rectangular room and have requested a plan to Vicoustic. I’m currently in the process of buying room treatment based on their advice. So my suggestion is to choose a company like that, pay a little for their advice and get proper answers with a plan.
 
You need to speak to acoustic specialists imo. I also have a rectangular room and have requested a plan to Vicoustic. I’m currently in the process of buying room treatment based on their advice. So my suggestion is to choose a company like that, pay a little for their advice and get proper answers with a plan.
That would be ideal, but probably also expensive.
 
This is the thread that got me started back then. As a non-technical person, it took me some time to learn and understand it all, bit by bit. And it is worthwhile.
I hope it can provide you some guidance as well.
 
I would hang carpets on the walls and put one on the floor to reduce echoes.
 
As @Mnyb says, the first step is to get a mic and take some measurements - diagnosis!
Diagnosis foremost and the very first of all [sic!)]. Later, the saved results can be compared with the improvements achieved after installing the panels [or snake oiled panels].
 
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Floor is wood, mostly no carpet.

So … where, how would you start to improve?
Start with a carpet and pad that covers your listening area extending a few feet beyond the speakers and chair. Move your listening chair back as far as is convenient, but not up against the opposite wall; try to form an equilateral triangle with your speakers. Experiment with "toe-in" of the speakers: start with them aimed to cross just behind your head while in the listening chair. You may also find it beneficial to tilt them up a bit at the front edge.

Speakers are ideally a few feet from any reflecting surface including back wall. Tweeters are at/near ear level. What speakers are you using and what are they sitting on?
 
Hi, clapping hands echoy sound is flutter echo, and it's a mid range thing mostly and really bad distraction while listening to music. Easiest would be to put some acoustic panels on the wall behind speakers, between speakers basically, and a thick curtain on the window wall. If possible put some acoustic panels behind the listening spot further kill the flutter between front and back wall. This is the low hanging fruit since even quite modest acoustic treatment helps for flutter echo. Small room issues still remain which are simplified loud early reflections and lack of later reverberation, and bass modes, but getting rid of the flutter echo is already quite big improvement, makes it much more comfortable space to be in. You sit quite close and sidewalls are relatively far away so it's mostly bass issues left, which are quite bad middle of the room. You could try multiple bass sources, alias multi sub setup, to get smoother bass as well. As disclaimer, I'm no professional acoustician either, just a keen hobbyist :)
 
The most important surfaces to treat in your case is the area with reflections from the rear wall (wall behind listening position) and the ceiling area between the speakers and listening position. If your speakers are either quite narrow or dipoles, the front wall (wall behind speakers) might also be important to treat.
The side walls are of less important to anything about if the room is very wide. Plus it seems unpractical with doors and windows.

Carpet is very bandlimited plus it doesn't absorp the higher frequencies well, so that's not really a good type of treatment. Should only be used at the smaller portion of the floor. You want treatment as the mentioned areas that work effectively down to at least 250 Hz area. This outrules a lot of commercial products that are only effective at higher frequencies and leads to a very uneven result with messed up tonality. Depending on the distance to ears, a hybrid product with some diffusion could be considered at the rear wall. But ceiling area is best to absorb.

P.S. I work with acoustics FIY.

roomacoustics1a.gif
 
As @Mnyb says, the first step is to get a mic and take some measurements - diagnosis!

From there you can start to plan the treatment.
For bass treatment yes, but not necessary for treatment of specular energy. Knowing the speakers and seeing the listening position is enough for that.

However, a common mistake many do is either using products that don't go low enough in frequency or place the panels either wrongly or cover too much area.
 
The biggest upgrade in a room with a lot of high gain reflections is treatment of the mirror images. It's not EQ or subwoofer(s). We need to start with the basic and most crucial. EQ and subwoofer comes after this.

What do you mostly hear in a room with a lot of reflections? It's the comb filtering, flutter-echo or echo if it's a large venue. This is what the brain focus first on. It's not the frequency response. Have you reacted when being in a large and lively church that the frequency response was bad? No, you hear the poor reverberation first.
 
Here is illustration of flutter echo using Amacoustics raytracing tool. Simple sketch of the room with left loudspeaker and listener, but leave corners out to be able to really showcase the flutter. Basically it's just 1st, 2nd ... order specular reflections between you the listener and the sound source, and two opposing boundaries. If you had acoustic treatment on the walls between speaker and listener, on the areas the blue traces cover, most of these would die out. Perhaps target just for the first specular reflection point to take out as much as possible of the first one, affecting most successive reflections as well. Avoid treating the whole wall to leave as much later reflections that arrive from random directions as possible to maintain some spaciousness and comfort.

Attached image what I mean but this is best tested by everyone on their own to get some insight, individual reflections highlight on hovering mouse on the timeline, for example.
1736320421258.png
 
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... What do you mostly hear in a room with a lot of reflections? It's the comb filtering, flutter-echo or echo if it's a large venue. ...
Flutter echo is really bad on small apartment rooms with bare walls, really bad, it seems to be the dominant source of "noise" basically. Really long sustaining robot sound if you clap hands, really the most easiest to perceive so most dominant distraction. It makes conversation difficult for example, the whole room could seem very noisy due to flutter echo. This is fun and easy practical test in your livingroom everyone, try standing up clap your hands loud and it's quite easy to trigger the flutter echo in a typical apartment room with bare parallel walls, you must be between at least two bare walls to have it.

Now, clap your hands near floor level while having your ears below furnishing level. The flutter echo isn't nearly as bad due to furniture breaking sound between the parallel walls! Flutter echo is very local effect in a way, very easy to take out by bookshelf with stuff, or almost anything really, that reflects / absorbs mid range wavelengths, and it's easy to test, just clap your hands in various locations in your room, between bare/ obstructed walls.

ps. anyone trying to imagine the reflections, here is some handy tips to have a perspective to it:
Blink of an eye lasts about 100ms and sound travels 343m/s so in a blink of an eye sound travels about 34m. So, in a small room whose walls are 5m apart sound reflects roughly seven times within blink of an eye. I can easily blink my eyes multiple times before hand clap flutter dies away, but on a spot where there is no flutter I hear hardly any "reverb", so there is basically no "late reverberation" in my apartment living room, or at least it's very low in level compared to the clap and flutter.

To my understanding late reverberation would be roughly at the same SPL through out the room, measured at any position, as per definition. Assuming late reverberation makes good acoustic environment, I would have to enhance it somehow, while simultaneously try and kill the early reflections somehow to shift relative balance of sounds in the room from early to late reflections, right, based on the hand clap sound test. This is why one should not absorb too much as it would also kill the late reverberation there is hardly any to begin with ( in a domestic room ). Hence it makes sense to try and only kill worst offenders, earliest loudest early specular reflections, and try and scatter rest of the sound to shift sound energy from early to later arriving (to ear).

Big enough surface area of acoustic treatment is required to cover necessary bandwidth (flutter for example), which I do not know but would assume vocal harmonic range so below 1kHz and up to get some clarity to sound. This means important sound wavelengths from say 34cm and shorter so the acoustic treatment needs to be at least this big in size to have any effect, as well as with effective thickness. More like from Schroeder frequency up which is about 1m in wavelenght or a small room but this big acoustic treatment starts to kill the "late reverberation" so some compromise somewhere. I'm sure professional acousticians have a lot to say to this and formalize / correct me, but this is kinda an example of a simplified process for audio hobbyist to tackle things in practical level.
 
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The most important surfaces to treat in your case is the area with reflections from the rear wall (wall behind listening position) and the ceiling area between the speakers and listening position. If your speakers are either quite narrow or dipoles, the front wall (wall behind speakers) might also be important to treat.
Hi Bjorn, thanks for the insight. When you say "treat" you refer to absorption or diffusion?
 
Hi Bjorn, thanks for the insight. When you say "treat" you refer to absorption or diffusion?
Depends on the distance to the surface, speaker directivity, budget, aesthetic requirements and the design goal. Pure diffusion cost more and builds much more out from the wall.
In your case, without knowing specific details of speakers and distance, I would say you need absorption in an area between speakers and listening position in the ceiling and either some absorption panels or BAD Arcs on the rear wall. You don't need to cover much area for one listening position, but treatment should ideally be very effective down to at least 250-300 Hz area.

Most measuement data from companies are not trustworthy but based on NRC and reverberation time, which are not really applicable to music in a small room. Yup, it's a mess.
 
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