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Old 14th May 2008, 04:52 PM   #151
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Quote:
Originally posted by graaf
why not trying some frequency equalization instead of elevating the speakers?
The equalisation I have on my amplifier do not correct the right frequency.

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can You hear any difference with or without those absorbers?
I will make a try and I tell you what I feel. (measuring would be better)

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move the stereo triangle back a little and it will shift beyond 8 ms
I cannot, I have a big shelve along the wall right behind the right sofa...

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which of them are below 5 ms?
Take the right wall as a mirror, it will give you an image of the right speaker. Then mirror this speaker up and down with the floor and ceiling, these 2 images are below 5ms.

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I don't know - diffusing cone means a lot of frequency dependent VER
It feels to me like a slot aperture in a line source...

And, yes the waveguides feels like a mistake.

Regards,
Etienne
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Old 14th May 2008, 05:46 PM   #152
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Quote:
Originally posted by gedlee
This is an incorrect conclusion from what Toole said. You NEVER get a spaciousness perception from reflections below 20 ms. So you must either get rid of them below about 20 dB or they will have a negative effect.
I don't have the papers at hands, I just have a book with a nice graph... The book is Master Handbook of acoustics (4th edition, page 77, if you have it...). It gives references to:
- Olive and Toole, The Detection of Reflections in Typical Rooms JAES 37 1989 539-553
- Toole, Loudspeakers and rooms for stereophonic sound reproduction AES Int. Conf. 3-6 May 1990

At the end, you say something, the book says something else. You are obviously much more experienced than I am, so does the book writer... I see myself as a student her, I'm trying to learn! Could you give some scientific facts about your sayings, please?

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I highly doubt that!
No offense, but why? The absorption coefficients of a sofa are around 0,3 between 125Hz and 4kHz...

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And cushions will not decrease this reflection very much at all. You need to do actual measurements and not just guess at the effects.
Cushions will certainly be better than the window, even if they don't do that much. I more than agree about the measurement part. I actually purchased a microphone and hope that I will get it running in a near future...

Quote:
Originally posted by Etienne88
But I think that it is a mistake since you don't get any direct reflections from the back wall and less from the side walls, floor and roof.
My mistake here! I wrote back wall meaning front wall... The front wall (the one you look at when listening to music) is well at the back of the speakers!

Regards,
Etienne
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Old 14th May 2008, 06:31 PM   #153
graaf is offline graaf  Poland
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Quote:
Originally posted by Etienne88

Take the right wall as a mirror, it will give you an image of the right speaker. Then mirror this speaker up and down with the floor and ceiling, these 2 images are below 5ms.
I see - this is because You lifted the speakers
I think that what is needed in Your situation is dedicated equalization - passive RLC or active
but unfortunately it means soldering or buying a professional parametric equalizer which is either very expensive or not of very "audiophile" quality (Behringer)
but I seriously believe that this is better option then lifting the speakers
You can correct the frequency domain but time domain cannot be corrected (at least practically)

Quote:
Originally posted by Etienne88

And, yes the waveguides feels like a mistake.
well, I respectfully disagree
for me gedlee's approach is a reasonable alternative, especially when one needs full frequency spectrum 20-20k Hz and higher SPL

with our fullrangers we cannot have that I suppose
of course this opens separate discussion on "who needs it?", the SPL targets and how much bass and highs is in our music and so on

anyway, when one needs good "room-speaker interface" and high SPLs and 20-20k Hz then I cannot see, frankly speaking, any alternative to Dr Geddes' designs

too bad that their availability (and market impact) is so limited

best,
graaf
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Old 14th May 2008, 06:32 PM   #154
TNT is offline TNT  Sweden
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Quote:
Originally posted by thinkbad
IKEA bowl in stainless for high WAF-factor
More blanda blank
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Old 14th May 2008, 07:44 PM   #155
gedlee is offline gedlee  United States
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Quote:
Originally posted by graaf

well, I respectfully disagree
for me gedlee's approach is a reasonable alternative, especially when one needs full frequency spectrum 20-20k Hz and higher SPL
anyway, when one needs good "room-speaker interface" and high SPLs and 20-20k Hz then I cannot see, frankly speaking, any alternative to Dr Geddes' designs

But you see, the high SPL capability is simply a convenient collateral benefit. If you want a loudspeaker system that is "room compatible" then a waveguide is required no matter what SPL you use. Nothing is less "room compatible" than an omni loudspeaker which sees all of the rooms flaws. The high SPL is just a nice added benefit of getting the directivity right.
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Old 14th May 2008, 08:01 PM   #156
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About Omni vs controlled directivity, I read that on the web:
When listening to extremely focussing loudspeakers which therefore produces few indirect sound, the listener hears the direct- and indirect sound of the recording in a spot beam from one direction. This is, however, a completely unnatural sound situation
It comes from a paper found on Duevel website. The guy makes argument to sell his product, which is natural! But he makes an interesting point.
I guess that in Earl's case, reflections come from the back making it more "natural" sounding. But still, it is only indirect sounds from the front (from the recording) and the back (from the room) only...

I am not trying to convince anybody with all these arguments, I just want to learn something and opposing ideas seems to be a good way of getting the truth out of it all.

Earl design seems to be a well developed LS with promising possibilities, I don't doubt about it. I just never add the chance to listen to it. Then I would like to believe that it is not the only way to achieve good sounding LS. The future might prove me wrong. Or not...

Regards,
Etienne
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Old 14th May 2008, 08:02 PM   #157
graaf is offline graaf  Poland
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Quote:
Originally posted by gedlee

If you want a loudspeaker system that is "room compatible" then a waveguide is required no matter what SPL you use. Nothing is less "room compatible" than an omni loudspeaker
well, once again let me
Quote:
ask about this specific omni setup that I have proposed
I am quite certain that no measuments of impulse response of such a setup were ever made, because I sort of just invented this setup myself
And I believe that this setup is very different from a typical "omni speaker in a small room"
You told me to "consider ALL rays in ALL directions impinging on ALL surfaces" because it seemed to You that I was "ignoring a few key ones"

I think that I explained above that I have not ignored them.
In a room slightly bigger than mine all early reflections from every direction can be delayed by 10 ms or even more.
Or am I wrong?
I just did simple calculations

Of course there are those VER <1 ms off the adjacent wall. They can easily be absorbed, they are already low pass filtered in case of directional speaker like my Fostex

But let me say and ask again:
Quote:
these reflections are very specific
(...)
are You sure that they are audible and detrimental to the sound?
I understand that in the light of Your research we can say that they probably can be detrimental to the sound but the real question is - are they?
best,
graaf
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Old 14th May 2008, 08:35 PM   #158
gedlee is offline gedlee  United States
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Quote:
Originally posted by graaf
I think that I explained above that I have not ignored them.
In a room slightly bigger than mine all early reflections from every direction can be delayed by 10 ms or even more.
Or am I wrong?
The burdon of proof is on you, not me, you have not shown me where what you say is true.

Quote:

Of course there are those VER <1 ms off the adjacent wall. They can easily be absorbed, they are already low pass filtered in case of directional speaker like my Fostex
These are still a problem!! and you can't absorb all of it no matter what you try and do.

I'm just trying to tell you what I have found. You can accept it or not.
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Old 14th May 2008, 09:03 PM   #159
graaf is offline graaf  Poland
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Quote:
Originally posted by gedlee

The burdon of proof is on you, not me, you have not shown me where what you say is true.
burden of proof?
but these are simple calculations. Anyone can do them.
Shall I really do them for You?
they are simply obvious, I can't imagine how can anyone put those simple calculations into question?
it is beyond me
they are like "2+2=4"
shall I also prove that?

Quote:
Originally posted by gedlee
These are still a problem!! and you can't absorb all of it no matter what you try and do.
but do I have to have it all absorbed? reducing their level by 10 dB wouldn't suffice?
after all in case of Your CD speaker there still are reflections, they are only reduced in level
I can do the same in case of those VER's in my case
There are very effective acoustic materials with 90% absorption >500 Hz
why not?

Quote:
Originally posted by gedlee
I'm just trying to tell you what I have found. You can accept it or not.
well, but what exactly have You found?

in another thread I asked:
Quote:
Can it be that in my particular case VER are effetively masked?
Taking into account:
- unusual loudspeakers with no diffraction and crossover-related group delay problems (although the driver itself certainly has group delay problems on frequency extremes)
- verticality of the VER
- the beaming of the driver affecting spectral content of the VER (which are obviously "low passed")
- very short time of delay <1 ms
You answered then:
Quote:
(...)
The basic answer is that we just don't know. The experiments that have been down were very simplistic and tend to lead to areas of further research rather than complete answers.

What is know is this. The group delay effect is dominate above about 1 kHz and tails off above about 6 kHz. At low frequencies there is virtually no effect. It is very dependent on the delay time and the level of the effect as well as the level of the playback. So in all likelyhood it is dependent on all those aspects that you asked about.

So what I must conclude from this is that above 1 kHz it would be wise to minimize these VER as much as possible - simply because I don't have enough information to determine tradeoffs.
ok!
in the set up I have proposed those VERs above 1 kHz can be minimized quite effectively
first of all they are minimized because of the directivity of the loudspeakers themselves - my loudspeakers are about -8<10 dB at 1 kHz at 75-90 degrees (the angle of reflection)
most of it can be easily absorbed, no problem with effective absorption of fequencies above 1 kHz

so why are You telling me "it is a disaster" "it cannot work" and so on?
I don't understand

best,
graaf
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Old 14th May 2008, 09:32 PM   #160
graaf is offline graaf  Poland
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then You answered:

Quote:
but this is subjective without strong objective support except for the simple experiments that have been done.
(...)
From what you described there would likely be very few VERs above 1 kHz. in that setup. Thats about all I can say.
in fact the above statement encouraged me to start this thread

and now You are saying "a disaster" about the same setup?
because this is the same setup

best,
graaf
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