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Old 11th May 2008, 10:01 AM   #101
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Stig Carlsson point of view about early reflexions.

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There are two ways, conceptually opposite to try to avoid these colourations. One is to accept that conventional loudspeakers are designed with little attention to the influence of the listening room, and modify the listening room to make parts of it approximate an anechoic environment. This requires extensive arrangements of sound absorbing materials. The other is to accept the domestic listening environment that serves most live sounds to such good advantage and create loudspeakers capable of preventing the sound reflected off the boundary surfaces of the listening room from degrading the quality of the reproduction.
These two ways give very dissimilar perceptual results because human hearing is quite sensitive to its acoustic environment. Despite its small size, the domestic living room comes closer to the acoustic character of a music room or a concert hall than does an anechoic environment.
It comes from this page 8.
The 2 last sentences are interesting! Any comments, experiences you would like to share?

Regards,
Etienne
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Old 11th May 2008, 10:12 PM   #102
graaf is offline graaf  Poland
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Quote:
Originally posted by Etienne88

More seriously: your second assumption is not always true.
(...)
From that I can say that the assumption "angle of incidence = angle of reflection" is true from the highest frequencies down to F3, is less and less true from F3 to F2 and is unappropriated below F2.
thanks for the equation

it follows that the assumption is true in practice (that is for most listening rooms) for the frequencies most important for sound localization that is above ~500 Hz

Quote:
Originally posted by Etienne88

Stig Carlsson point of view about early reflexions.
(…)
Any comments, experiences you would like to share?

well, all I can say is that it is also my point of view

I'm glad to hear that You gave this Beveridge speaker positioning a try and that You liked it

best,
graaf
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Old 11th May 2008, 11:17 PM   #103
gedlee is offline gedlee  United States
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There doesn't have to be only the two extremes - modify the room to fit the loudspeaker OR modify the loudspeaker to fit the room. The ideal is to find what combination of both yields the best result. I don't think that the optimum can be reached with only doing the room OR the loudspeaker - you must consider both and work them together as a single system to be optimized.
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Old 12th May 2008, 06:02 PM   #104
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Quote:
Originally posted by graaf

it follows that the assumption is true in practice (that is for most listening rooms) for the frequencies most important for sound localization that is above ~500 Hz
Reading Stig Carlsson document made me realise that below F2, the "reflected" waves are in phase with the direct waves (since the wavelength are big). That's also why we get a bass boost at the lower frequencies due to the room.
So there is no problem with your assumptions...

Quote:
Originally posted by gedlee
There doesn't have to be only the two extremes - modify the room to fit the loudspeaker OR modify the loudspeaker to fit the room. The ideal is to find what combination of both yields the best result. I don't think that the optimum can be reached with only doing the room OR the loudspeaker - you must consider both and work them together as a single system to be optimized.
I fully agree on that!
I started doing some readings (that I didn't fully digest yet...!) about the perception of reflected sound. Depending on the level of the reflected sound (relative to the direct sound, of course) and the delay of the reflected sound, the reflection can be perceived as an echo, a broadening of the image, spaciousness or not perceived at all. Echo is clearly unwanted! Image broadening can be tolerated in very small rooms. Spaciousness would be what i would be aiming for (What is your opinion about it?). Inaudible reflexion sounds like anechoic chamber to me, which is not nice!
According to my readings, and if you want to be in the spaciousness zone, the reflexions have to be lowered by 5dB if the delay is between 5 and 15 ms and by 10 dB if the delay is below 5 ms.
With good positioning and some damping, -5dB can easily be achieved. It almost seems to easy... Am I wrong somewhere?

Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...

Regards,
Etienne
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Old 12th May 2008, 06:29 PM   #105
gedlee is offline gedlee  United States
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Quote:
Originally posted by Etienne88
!
I started doing some readings (that I didn't fully digest yet...!) about the perception of reflected sound. Depending on the level of the reflected sound (relative to the direct sound, of course) and the delay of the reflected sound, the reflection can be perceived as an echo, a broadening of the image, spaciousness or not perceived at all. Echo is clearly unwanted! Image broadening can be tolerated in very small rooms. Spaciousness would be what i would be aiming for (What is your opinion about it?). Inaudible reflexion sounds like anechoic chamber to me, which is not nice!
According to my readings, and if you want to be in the spaciousness zone, the reflexions have to be lowered by 5dB if the delay is between 5 and 15 ms and by 10 dB if the delay is below 5 ms.
With good positioning and some damping, -5dB can easily be achieved. It almost seems to easy... Am I wrong somewhere?

Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...

Regards,
Etienne
Reflections after 15 ms are highly desirable, especially if lateral, because they create spaciosness. Delays less than 10 ms do no good at any time. It is not easy to lower all reflections < 10 ms. by AT LEAST 5 dB (I'd say 10 dB) unless you make the room very dead, but then you kill the spaciousness. You must use high directivity speakers pointed so that they minimize the early reflections, but still excite the later reflections by using a lively room. Wide directivity speakers cannot achieve the low reflections < 10 ms without having a very dead room.

This is precisely where the speaker and room have to work together to achieve the right balance of direct to refections delay and spectral balance between the direct sound and the reverberant sound. Only a CD device of narrow directivity can do this. Nothing else works. And even with narrow directivity, you still almost always have a floor and ceiling reflection that you must do something about (because most rooms are shorter than they are wide). Vertical reflections are never a good thing, although if > 20 ms they are kind of benign especially if not from the forward direction.
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Old 12th May 2008, 06:51 PM   #106
el`Ol is offline el`Ol  Germany
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Quote:
Originally posted by gedlee

Only a CD device of narrow directivity can do this. Nothing else works.
What I don´t like about these devices is that the spacial image collapses as soon as I turn my head.


Poor Graaf. Most people will rather invest an hour to tell you it can´t work than five minutes to test it themselves.
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Old 12th May 2008, 07:04 PM   #107
graaf is offline graaf  Poland
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Quote:
Originally posted by gedlee
There doesn't have to be only the two extremes - modify the room to fit the loudspeaker OR modify the loudspeaker to fit the room. The ideal is to find what combination of both yields the best result. I don't think that the optimum can be reached with only doing the room OR the loudspeaker - you must consider both and work them together as a single system to be optimized.
of course! I agree absolutely – loudspeakers and room as a single system!

well, but there is a fatal problem with this design approach of speakers with "modifying the room to fit the loudspeaker" in mind

because in practice a room is something given because apartments and houses are nor designed for "audio purposes", their design takes into account other factors and priorities and this cannot be changed

therefore IMO this design approach (that assumes "using" a room that fits the loudspeskers) leads to decline of HiFi into it's current market and social niche

the only way out of this niche is a loudspeaker that fits a normal living room while being visually unobtrusive
a loudspeaker that doesn’t need a "modified room"

"the problem with HiFi" (to borrow the name from other thread) is EXACTLY the problem of loudspeakers that need "modified rooms", "dedicated audiophile listening rooms" and such thing s like positioning 1.5 m away from room walls (that is in the middle of the room) to fulfill their promise of good sound at least to some degree
otherwise they are big disappointment especially for their price and visual obtrusion, the décor ruin they cause
no surprise that a non-audiophile does not know "what is the point of all this?"
especially as non-audiophile is naturally comparing the sound of this thing to the "real thing" as she/he doesn’t have that "audiophile brain-ear reference" (that is "comparing the sound of a HiFi gear to the sound of other HiFi gear"), only the "real thing" reference of live music and she/he has no idea that according to an audiophile "HiFi is not about" mimicking the "real thing", that "this hobby is about something entirely different" and so on

truth is that most people LOVE music and would LOVE to have at home something resembling the "real thing"
typical audiophile HiFi gear in a suboptimal setup simply fails to meet their expectations

and for most part it is the problem of loudspeaker that is like another family member that needs his/her own room and to make things worse in fact it needs a much bigger room than a "human" family member, than a second or third bedroom in a typical apartment or house
quite "a separate living room for loudspeakers"
this is absurd for most people
a second living room where You have to go to listen to the music, and to appreciate it best You have to listen alone of course because the "sweet spot" is so small with conventional loudspeakers
another absurd

but without "dedicated room" nor "head-in-the-vice" the result is nowhere near anything even resembling the "real thing"

simply "much ado about nothing" for most people
and add to this things like "audiophile cables" that are on top of all that as final proof of mental instability of "an audiophile"

no surprise that most people who are keen on music, real music lovers, record collectors and so on are typically not keen on HiFi and listen to a micro or mini systems (and I know a lot of them)
and no surprise that the term "audiophile" sounds like meaning a person with a psychological problem (like "necrophile" for example), somebody weird at best and simply disturbing at worst
I am rather reluctant to admit to newly met people that "I am an audiophile" it is like saying "hello! I have a silly compulsive obsession!"

I look at CD speakers like Yours as an attempt to overcome this room problem, an attempt to design speakers that are "room-proof" to some degree.

I think that their commercial failure can be partly attributed to their wrong market positioning that was fatally combined with their low WAF looks. I think that AI-Audio missed its target market and that their non-audiophile sound ("dull, lifeless... blah blah blah") could be more appreciated by non-audiophile music lovers
...if only women could accept their look

best,
graaf
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Old 12th May 2008, 07:16 PM   #108
graaf is offline graaf  Poland
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Quote:
Originally posted by Etienne88

Graaf, I have a question for you: can you see the drivers of your LS?
I ask this because a get a better tonal balance (meaning more treble) when I see the drivers, but this means that I am standing which is not very practical...
yes I can see them
can You post a schematic drawing of Your current setup - how exactly the loudspeakers are positioned?

best,
graaf
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Old 12th May 2008, 07:20 PM   #109
graaf is offline graaf  Poland
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Quote:
Originally posted by el`Ol

Poor Graaf. Most people will rather invest an hour to tell you it can´t work than five minutes to test it themselves.
nah I am not that poor

from time to time there happens an exception - like in case of Etienne88 who found that 5 minutes

and I tell You it is so deeply satisfying!

best,
graaf
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Old 12th May 2008, 07:40 PM   #110
graaf is offline graaf  Poland
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Quote:
Originally posted by gedlee

Only a CD device of narrow directivity can do this. Nothing else works. And even with narrow directivity, you still almost always have a floor and ceiling reflection that you must do something about (because most rooms are shorter than they are wide). Vertical reflections are never a good thing, although if > 20 ms they are kind of benign especially if not from the forward direction.
Only a CD device of narrow directivity can do this?
well, I don’t know
please take a look at Beveridge brochure
it seems that Beveridge line source positioned on the opposite walls can do this, in a bigger room (but not overly big) all lateral reflections can be delayed by 15 ms
moreover - in case of Beveridge line source also the floor and ceiling reflections would be no problem

of course it is only a brochure not a peer-review paper but the reasoning is convincing

any comment?

best,
graaf
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