Controlled vs wide dispersion in a normal living room environment..

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Simon,
15ms is not this difficult to achieve if you use 90° pattern radiation speakers in corner placement and if your room is 3 meter wide.
With speakers like the one from E. Geddes or PI speakers it is achievable in a not this big room.

Corner placement is a bad idea unless the speakers were designed to fit well back into the corner. Otherwise you will have problems. I find bringing the speakers out well away from a highly damped back wall works best. In a 3 meter wide room I would space them .8 m, speaker, 1.4 m, speaker, .8 m. Or something close to that. My speakers are about 1.2 m off the back wall.
 
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Hi Earl,
Obviously about your speaker you are right.
It was a shortcut from my side as your approach and W. Payrham one's share some things in my view ( constant directivity amongst other as well as recommendation about toe in iirc). My bad.

So a Pi 7 is designed to be placed on corners and in a 3,5m wide room 15ms/-15db is achievable ( min pathlength of reflected wave is 5,25m (so approximately 15ms), and with minimal amount of absorbtion on side wall -15db should be achievable.
Ceiling would be limiting factor though. Either the loudspeaker does have high vertical directivity, either diffusion must be used ( or both).

For LEDE target (20ms/-20db) i agree this need a large room ( minimum 3,5m behind the listening position lead to big room dimension).
Thank you for pointing the position layout for your loudspeakers.
 
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Neither of which is possible in a small room. In a small room you just have to do the best you can. Reaching ideals is just not going to happen.

Corner placement is a bad idea unless the speakers were designed to fit well back into the corner. Otherwise you will have problems. I find bringing the speakers out well away from a highly damped back wall works best. In a 3 meter wide room I would space them .8 m, speaker, 1.4 m, speaker, .8 m. Or something close to that. My speakers are about 1.2 m off the back wall.
My room is too small to achieve even that.

Thanks Simon for your speaker toe-in story. How far off axis do you think you are in one vs the other?
Also it would be nice if you could do rough diagram. It surprising that the change in sofas made such a difference.

I started to try to do a bit of basic measurement and trigonometry to try to figure out how far off the speaker axis I am and ended up deciding to build a sketchup model of my floor plan instead as it was easier... :D

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Surprisingly I am less off the speaker axis than I thought. I guessed about 10-15 degrees but according to Sketchup it is only 7 degrees! When I changed from toeing behind the listener to toeing in front I was careful to toe so that I was the same amount off axis from the speakers as before - just on the other side. As the speakers are symmetrical on the vertical axis the direct signal to the listener should be the same as before, only the reflections will differ.

This is quite easy to do visually as the speakers are just shoeboxes so when toed I can see one of the sides, and by comparing how wide the visible piece of side is I could make them off the listener axis by the same amount in the other direction.

So the total amount they have been turned in compared to before is 14 degrees on each side or from -7 to +7 degrees. Doesn't sound like a lot but it has quite an effect on the sound. Probably because the sidewall reflection is at a very acute angle now. I could have probably gone a bit further. I was right about the new crossing point though - about 1 metre in front of the listener. The problematic specular reflection is the right hand sofa. While both drivers are above the level of the base and arm rests of the sofa (so not quite as bad as a flat diagram suggests) the backrest of the sofa is a big flat near vertical reflective surface compared to the old fabric sofa. The left hand side has a bay window with blinds so not nearly as bad, especially as the distance is much further.

The speaker separation in degrees is only 32.2 degrees which is disappointing. I knew they were too close but this is far from optimal.

Unfortunately in a small room with two sofas, an arm chair, (in the bay window area, forgot to put it in the drawing!) a TV cabinet and two huge toy boxes (also not shown) I think the layout I have now is probably the best possible!
 

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Earl i've got a question about small room: in which range of volume (m3 or cubic feet) do you define them?
Something like 45m3 and lower?

Just guesssing (but its probably a good guess) I'd say that any room less than 200 m^3 will have modes in the range of hearing. This makes them small. But there are a lot of variables, like damping and aspect ratios. As I said, my room, which is about 3 x 5 x 7 m is modal below about 120 Hz and geometric above about 180 Hz.
 
@DBMandrake: The new leather sofas may act as bass and lowest midrange absorbers, while giving specular reflections at higher frequencies. To me who also have a leather sofa it is no surprise that the side sofa can be troublesome at LP.

As the rom is small it’s not feasable (or, I guess, appreciated) bringing in typical absorbers or diffusers. Have you experimented with lifting out the endpart of the sidewall sofa a bit, so the specular refections are deflected away from LP?

If you have a laserpointer and put a mirror on the sidewall sofa, you can see and get an idea of how much of an angle that would be suitable if your laserpointer is beaming from the speaker. The width of the beam is very small and if it was a soundray, maybe a bat would hear the frequency of that wavelength, not you. But specular soundrays in treble and higher midrange would be deflected about the same way. And, as the sidewall sofa is quite wide it may cover those wavelengths even with 2 people in the backwall sofa. Perhaps worth a try as it doesn’t cost much or anything?

If the new sofas are hollow and have open wooden frames towards the floor, you could fill the empty space with insulation and nail a plywood sheet to the frame. You would then get 2 hidden panel absorbers for lower freuqencies.
 
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Simon, could it be possible to drag your sofa 1061mm closet to speakers, or put a listening chair there? Actually the major issue now is that you are sitting too close to back-wall! And this seems to be the most common "mistake" when I look at pictures - applies even for me!

So close to wall and far away from speakers you have high amplitude of longitudinal modes and also short-timed first reflections from the backwall.

My setup, speakers on the long wall, separation 2.2-2.4 meters, distance 2.2-2.4m.
 

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A note about furniture:

What we sit in when we listen can have a big effect on what we hear. I have seen this many times. Make sure that what you are sitting on is solid and has no resonances. I once fixed a big problem at a clients by opening up the sofa and using glue to dampen out the weak structure underneath. In cars, seat resonances can become quite offensive (been there!)

My sofa has a solid oak external frame with leather seating. The frame is super solid.
 
My room is too small to achieve even that.

I started to try to do a bit of basic measurement and trigonometry to try to figure out how far off the speaker axis I am and ended up deciding to build a sketchup model of my floor plan instead as it was easier... :D

That's almost like what I'm dealing with except a big screen tv where the cabinet is. Lots of early reflections.

I think one solution is to put the speakers on the floor below and in front of the tv and angle them up to make the first reflection points the corners.

You really can't do the toe in technique with big flat object like a cabinet between them, unless the object itself diffuses sound.
 
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Hi,
Earl thanks for your answer. Ok it follow more or less the 'theorical' i've been teached 20 years ago.
I asked because it seems that in the last ten years there have been a lot of redefinition in acoustics limit of application from what i understand.

I know this is off topic as we are talking about domestic environnement but for example Ebu (iirc) specify 45m3 as lower limit for control room duties. It is way lower than what i learned 20 years ago ( about 100m3 was considered lower limit at that time - and by my teacher's view).
It astonish me as laws of physics can't really be broken but it seems pro (commercial) acousticians have managed to apply tricks to lower limits.
 
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I know about economical constraints in the industry Juhazi ( i was actually part of the industry some years ago ;) ).
Yes it's a bummer this budget constraints makes technical things the first to be touched ( even the BBC doesn't have R&D anymore...).
The fact is this 'standards' are there and works is produced thru them. And all i can say is that the results of this works is not nescessarely worst than it was years ago in large venue ( if we let things like loudness war at our side, because it is an other matter in my view...).

Earl's point of view is interesting about that for me as he is an acoustician and may have a sharp point about that.

Anyway, at the moment some very good results seems to be achievable in 'small' rooms with 'modern' approach as T. Jouanjouan's designed room or WSDG's one seems to be recognised environnement worldwide in the industry ( a bit off topic from domestic environnement but interesting nevertheless- at least for me!).
 
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What I noticed from the drawings and descriptions shown above is that many of you are dealing with highly constrained conditions that will seriously limit the end result. My room was custom designed and built from scratch to be a listening room and home theater and was done with as few compromises as possible. This means that what I do and have done may be vastly different that what one would do in a highly constrained situation.
 
I started using a big screen TV as a computer monitor some years ago. Great idea, but I was listening to music less and less for some reason. I figured its time for better speakers. The problem was the early reflections though. Of course there are worse problems in life than early reflections.

My next attempt will be directional speakers that sit on the floor below and in front of the TV, that are angled up a bit.
 
Can we make a virtue of necessity?

In tiny rooms every few meters the sound finds a wall,

the listening point will always be leaning against a wall,

alterations of the tone of the reverberated field, for an excessive absorption of medium-high frequencies,

mess up the sounds in the wide modal region.

Incidentally, IMO, even in large domestic rooms, the frequencies reproduced in the modal region are unpleasant, compared to what we can hear in a concert hall.
 
Can we make a virtue of necessity?

In tiny rooms every few meters the sound finds a wall,

the listening point will always be leaning against a wall,

alterations of the tone of the reverberated field, for an excessive absorption of medium-high frequencies,

mess up the sounds in the wide modal region.

Incidentally, IMO, even in large domestic rooms, the frequencies reproduced in the modal region are unpleasant, compared to what we can hear in a concert hall.

Yes. I noticed my car doesn't sound fatiguing and its a small space (obviouisly). I think it highly absorptive and there are mostly round surfaces. So I think its the large flat surfaces in rooms that really mess up a frequency response.
I have a storage area with boxes all over the place, and almost no bare wall space. I think I will try setting up some speakers in there and see how it sounds. Of course I've learned it really takes time to assess whether a room sounds good or not.
 
David Griesinger has published a lot of studies of acoustics, also of small rooms and of headphone listening. He states that many classical recordings carry information of reverberations in the hall where the recording was done.

I screenshot from a video - he recommends placing stereo (sub)woofers on the long wall, at 1/3 and 2/3 of width. I have had just that for 12 years and it works, but also my rather open, soft and large room helps too.
 

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