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Old 19th March 2010, 12:18 AM   #801
jwmbro is offline jwmbro  United States
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Originally Posted by LineArray View Post
Lowest room mode was one octave too high (ehem ):

A: _20____31
B: _31___223
C: 223___892
D: 892___20000

sorry, couldn't go to sleep before correction.
I was just about to point this out. Error I'm assuming was you used the room dimension as wavelength instead of half-wave. That sounds more accurate, though in my experience there's not much modes left up at 223Hz.

What is the T and V in the equation for the Schroeder frequency?
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Old 19th March 2010, 12:25 AM   #802
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Originally Posted by klankymen View Post
Error I'm assuming was you used the room dimension as wavelength instead of half-wave.
Yep.

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Originally Posted by klankymen View Post
What is the T and V in the equation for the Schroeder frequency?
T is -60db reverberation time in seconds
V is volume of room in m^3
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Old 19th March 2010, 12:35 AM   #803
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Did we just arrive at a point Toole already made in his 2006 paper http://www.harman.com/EN-US/OurCompa...ions/13686.pdf? The concept of reverberation time is of no use in acoustically small rooms.
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Old 19th March 2010, 01:46 AM   #804
gedlee is offline gedlee  United States
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Originally Posted by klankymen View Post
though in my experience there's not much modes left up at 223Hz.
A pet pieve of mine BUT - there are lots and lots of modes at 223 Hz! What I think you are refering to is that "discrete modes" are no longer evident by 223 Hz.

FYI, my room has very heavy LF damping. Only the first mode or two are actually evident as discrete modes. After that its just a blur of random response, until about 120-150 Hz when it takes on the classic "Schroeder" appearance - peak and dip spacing are independent of frequency and completely unrelated to room size or dimensions.
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Old 19th March 2010, 02:50 AM   #805
jwmbro is offline jwmbro  United States
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Originally Posted by gedlee View Post
A pet pieve of mine BUT - there are lots and lots of modes at 223 Hz! What I think you are refering to is that "discrete modes" are no longer evident by 223 Hz.
Sorry, what I meant to say was "there is not much effect of the modes left". You are of course correct, technically modes continue up infinitely, so long as a room length is divisible by the wavelength.

I also notice the last significant effect of the modes around 150Hz, and I assumed that since my room is so small, in larger rooms it would become unnoticeable even deeper.
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Old 19th March 2010, 07:05 AM   #806
el`Ol is offline el`Ol  Germany
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Originally Posted by graaf View Post
tough choice, I had DEQ and I didn't like it
what about Audyssey 2EQ™ Room Acoustic Correction in Onkyo receivers?
The problem of built-in functions in consumer devices could be that they don't do the extreme bass boost you need.
What was bad about the DEQ?
I once tried the simple bass/treble adjustment in my digital receiver and it was shocking how it degraded the sound. Digital signal manipulation obviously has to be properly implemented, even if it's simple. Maybe you should take analog devices into account.
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Old 19th March 2010, 07:20 AM   #807
graaf is offline graaf  Poland
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Originally Posted by markus76 View Post
Yes, because below 100Hz you want to target single modes with 1Hz accuracy.
can I do this with DCX2496?
because the DEQ2496 I remember had stepped controls that didn't allow for such fine tuning. This was part of my disappointment with this unit.

Have Behringer upraged the software in the meantime?
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Old 19th March 2010, 07:51 AM   #808
graaf is offline graaf  Poland
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Originally Posted by el`Ol View Post
The problem of built-in functions in consumer devices could be that they don't do the extreme bass boost you need.
is + 6dB @50 and +12dB @30 beyond their capabilities?

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Originally Posted by el`Ol View Post
What was bad about the DEQ?
couple of things like limited frequency boost capability (quickly running into digital overload) and as You know that I really need to boost the flooder
then the stepped controls excluding really fine tuning, the AutoEQ that is going on forever and is not truly-Auto (You have to stop it manually) and so on and last but not least the general sound of digitalinezz

I was using it as a DAC because I didn't have separate CD transport-DAC. And I considered buying separate DAC just to put DEQ's DAC out to be an audiophiliac overkill. So I sold the DEQ and ...

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Originally Posted by el`Ol View Post
Maybe you should take analog devices into account.
yes indeed ... I turned my attention to analogue gear

It was then when I bought those two Technics SH-9010 5-bands stereo parametrics at a bargain price ca 50 USD each, encouraged inter alia by this opinion from a guy Paul Kemble:
Quote:
A compact solution that the author favoured for halls, studios and domiciles was the very excellent Technics SH-9010 equaliser
A Paul Kemble web page - equalisation.

I checked them with DEQ RTA function from analogue input and they appeared indeed to work as advertised, reliable and precise.

yet Markus suggests that analogue gear lacks the ultimate precision that is really needed
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Old 19th March 2010, 09:20 AM   #809
graaf is offline graaf  Poland
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Originally Posted by markus76 View Post
Did we just arrive at a point Toole already made in his 2006 paper http://www.harman.com/EN-US/OurCompa...ions/13686.pdf? The concept of reverberation time is of no use in acoustically small rooms.
interesting, actually Toole made some points in this paper that seem to support my intuitions that I expressed in this thread and tried to put into operation with the flooder

some of them:

Quote:
The performance of a loudspeaker is much more complex than anything revealed in an on-axis anechoic measurement. The perceptual processes of two ears and a brain are vastly more complex than anything revealed in a room curve or a reverberation time.
(...)
Two ears and a brain have advantages over a microphone and an analyzer.
The fact that the perceived spectrum is the result of a central (brain) summation of the slightly different spectra at the two ears attenuates the potential coloration from lateral reflections significantly If there are many reflections, from many directions, the coloration may disappear altogether
(...)
Superimposed on all of this is a cognitive learning effect, a form of “spectral compensation” wherein listeners appear to be able to adapt to these situations, and to hear “through and around” reflections to perceive the true nature of the sound source. Put differently, it seems humans have some ability to separate a spectrum that is changing (the program) from one that is stationary (the transmission channel/propagation path).
(...)
Steady-state measurements in a room are not definitive because the physical interaction of sounds at a microphone is very different from the perceptions arising in two ears and a brain. Visually alarming irregularities in measurements are frequently not heard
(...)
The horrendously irregular steady-state “room curves” that we see simply do not correspond to what we hear.
(...)
In terms of image localization, the precedence effect appears to hold in the presence of many reflections, and our distance perception improves. Distortions of image size and position appear to be borderline issues. From the perspective of sound quality, multiple reflections reduce the effects of comb filtering (good) and enhance our perception of resonances (good for the music, and bad only if the resonances are in the loudspeakers). If managed properly, room reflectionscould contribute to our impressions of spaciousness.
The audibility of an individual early reflection in a recording is not greatly influenced by collections of early reflections in a room,
(...)
it is unlikely that the decaying sound field in a listening room would significantly impact the apparent decay of a concert-hall recording, or those made in larger recording studios.
(...)
Our ability to judge the distance of sounds is greatly improved when there are reflections, especially, it seems, Whether a change in image position or size is good or bad, then, is a subjective judgment. Because what was intended by the recording artists is normally not known, such judgments must be based on what appears to be plausible or personally preferable.
(...)
A room with abundant reflections is not likely to exhibit audible evidence of comb filtering from any single reflection.
Multiple reflections improve the audibility of timbral cues from resonances in the structure of musical and vocal sounds.
of course below the transition frequency "what we hear can substantially be predicted by steady-state frequency-response measurements."

this I find most interesting:
Quote:
In thinking about what may happen in the small rooms of interest to us, assuming no other differences, the critical distance will be larger because these rooms have proportionally more sound-absorptive material and the sound sources have significant directivity, and are aimed at the listener. As a result, we may find that we are not listening in the reverberant sound field.
(...)
At what point our ability to judge the location and distance of the loudspeakers inhibit our ability to be persuaded that we are in the environment incorporated into a recording?
can it be that it is NOT the case of the flooder in a typical living room with modern decor (not particularly sound-absorptive)?
it is not aimed at the listener, it is not directional with respect to any given lateral plane, the bulk of perceived acoustic energy is coming from the reflection off the ceiling which is quite uniformly covered by direct sound in spite of the directivity of the speaker driver itself (thanks to the reliatively large distance between the speaker and the ceiling) and generally there is a whole lot of early reflections <20 ms

perhaps the resulting sound field is significantly more diffuse than in a typical case of forward firing speakers in acoustically treated room?
in addition the flooder is effectively acoustically hidden - we are unable to judge its location

no, the sound is not perceived as "coming from the floor"
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Last edited by graaf; 19th March 2010 at 09:36 AM.
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Old 19th March 2010, 10:25 AM   #810
el`Ol is offline el`Ol  Germany
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Originally Posted by graaf View Post


yes indeed ... I turned my attention to analogue gear
Comments at Thomann say the analog graphic EQs around 300€ are not noise-free, so maybe a parametric is really the better choice.

A question to the experts: Isn't an ultra-fine resolution in the bass only necessary for steady state? E.g. with a 60 Hz pulse 100 ms long you have just six periods. Does that give an equally sharp localization in the frequency domain?
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