Hi Rudolf
I would think that our brains can detect the "mirror", but being the reverse of the direct sound and with a different timbre, one could argue that it might be more confusing than supporting.
We haven't done our homework with dipoles until we have considered their special directivity pattern wrt first wall reflections. In this picture I show the 'loud' part of a dipole in red and the 'silent' part in green. 'Silent' means at least 10 dB down at the source. Blue lines are the first reflections from the front and side walls.
View attachment 346334
We notice how the first side wall reflection is very much attenuated, and it is very silent behind the center phantom image too. We need to do something about the first reflection from the front wall - but only in that area.
There will be strong reflections from the room corners (no lines shown in the picture), but they have to travel over two walls. That makes them a bit more diffuse than the front wall reflection. We will get a marvellous 'cinemascope' sound, if we leave the corners untreated, but it is not natural/realistic of course. So it is advisable to put something diffusive/absorptive into those corners.
You will have noticed that the speakers are toed-in 45°. Listening angle is ~30°. What will happen, if we align the dipoles parallel to the side walls:
View attachment 346335
We see how this alignment doesn't make any good use of the dipole 'nulls' and how it puts the front wall reflection into the hottest part of the radiation pattern.
The pictures don't include the first contralateral reflections. But you can imagine them easily. With toe-in they will be quite strong and contain the full frequency spectrum. They nicely support the feeling of spaciousness.
Rudolf
Thank you Rudolf. As I read the posts i am beginning to understand the terms and I realize that my speakers are only slightly toed in so I guess maybe I should toe them in more. I will post pics later.
Sorry jimbones, but to me it looks like the right speaker has a very reflective wall very near and the left one a well damped "wall" further away. Asymmetry.
Also the distance to front wall (behind the speakers) should be at least 5 feet (depending on low the dipole function begins. Obviously you can easily pyll speakers way more off the front wall.
Your ceiling looks to be not very reflective, but a little low. I think that dipoles dont need a diffuser just above them in the ceiling.
Happy testing!
Also the distance to front wall (behind the speakers) should be at least 5 feet (depending on low the dipole function begins. Obviously you can easily pyll speakers way more off the front wall.
Your ceiling looks to be not very reflective, but a little low. I think that dipoles dont need a diffuser just above them in the ceiling.
Happy testing!
OK so this is a basement, with almost a 7' ceiling and the speakers are 4' from rear wall and 2 ' from side wall (this is a older pic). The ceiling (before adding diffusors) was actually dead. It is the armstrong acoustical tile so it has tiny holes in it and the surface has small depressions. The dipoles kick in about 275 to 300hz.
Ok Jim, seems like you have already done the most obvious corrections!
I think that now you just have to find the settings that please you the most! If you have measuring gear, try to find out how room modes could be minimized. Try first what moving your head (mic) some 30-60cm (1-2 feet) here and there, up and down, means.
I think that dipoles need some reflections from the room, too much damping is not good, unless you want the "headphones on" effect.
I think that now you just have to find the settings that please you the most! If you have measuring gear, try to find out how room modes could be minimized. Try first what moving your head (mic) some 30-60cm (1-2 feet) here and there, up and down, means.
I think that dipoles need some reflections from the room, too much damping is not good, unless you want the "headphones on" effect.
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No I don't want the headphone effect. I feel I m not getting enough room reflection. But I do know I have to put absorbers at the first reflection point.
I have the OmniMic but not sure what features to use to test the room.
My suggestion is that your room has a far better chance of sounding good than about 80% of rooms I see posted here. You have carpet on the floor, a good mix of reflection, absorption and diffusion and a nice mix of materials. You could do much worse!
In 2-speaker stereo you don't want any room reflections other than the ones that add spaciousness. Any room reflection will affect tonality, localization and clarity. It's hard to improve on all 3 and in the end stereo itself puts you in an interference field that has detrimental effects*. Nevertheless I think it's worth trying.
My recipe:
- Acoustic symmetry
- Smooth and complete (!) frequency response
- Long reflection free time
- Very low modal ringing <500Hz
- Strong but delayed lateral or contralateral reflection
* This can be improved by using a physical barrier blocking crosstalk. See Keele, "THE EFFECTS OF INTERAURAL CROSSTALK ON STEREO REPRODUCTION AND MINIMIZING INTERAURAL CROSSTALK IN NEARFIELD MONITORING BY THE USE OF A PHYSICAL BARRIER"
It won't sound like headphones, since you will get the soundstage in front of you, and not inside the head. Depth perspective is also lost with headphones.
I have a pretty dead room and dipoles. I like it dead, as it increases clarity and definition.
I XO at 200 Hz, which is not all that high really...
ETC in listening position looks like this: (one speaker)
ETC in listening position looks like this: (one speaker)
An externally hosted image should be here but it was not working when we last tested it.
Markus,
the room is asymmetrical so I put up a wall on the left side but it does not extend to far in front of the left speaker. I will try to make it more symmetric through acoustic treatment.
Jim
A friend and a member here pieskapov has a very well damped room with highly directive dipoles. Imaging is super but you can't move your head even 10cm or you loose it! That's why I dont like it, it is too much for me!
Here is an article of his system A high-end story from Vantaa
Here is an article of his system A high-end story from Vantaa
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