graaf said:
I have in fact overcome the drawbacks of conventional DML. But i used aspects of their behaviour as a starting point and maybe as a first model in designing decorrelation to larger off axis angles.
Especially too early - also lateral - reflections are detrimental IMO in many ways. Diffusivity among other advantages gives you (and this my is own impression as well as from most guest listeners)
- tonality staying more neutral even when changing listening position (slightly or even more widely spaced)*
- widens the dynamic range of enjoyful listening in a usual living room
- places a more realistic and balanced loudness impression between e.g. strings, vocals and percussive elements. As the percussive elements are typically exaggerated in loudness due to highly correlated reflections during reproduction in untreated small rooms **.
- the listening room's acoustics subjectively being not "perceivable" anymore in favour of the acoustics on the recording, being it "concert hall" or "virtually created" acoustics of the recording venue.
______________
* this contributes IMO to the listener simply "relaxing". A factor not to be underestimated:
I know some of those "butt and head clamped" to the sweetspot listeners ... maybe they got used to it because of their own deficient setups. But listening to a recording is also "engaging" to some illusion:
Listeners are simply more relaxed in their seat - it seems to me - if they feel tonality would be "still very good" and "mostly the same" even some decimeters to the left, right, front or back.
If you listen e.g. to strings and vocals with highly correlated early reflecions from the living room instead, this is - in my experience - not the case.
** Line sources especially may suffer from that in untreated small rooms,
but no reason to change my habitual nickname here
They can excite high level, high correlated side reflections at the listening seat ...
That may result in percussion sounding simply too loud and "bang" like (but lacking detail and color) while e.g. strings and vocals tend to sound "harsh".
Line sources in untretated small rooms thus are like demonstrators, what
- too high in level
- too early
- too correlated
side reflections can produce.
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You're right of course. There are two ways out of this situation - the first is to design the speakers so as to diminish the "room sound" contribution. IMHO this eventually leads to a kind of headphones-like sound. Because in the "ideal circumstances" for this approach - "the room effectively taken out of the picture" - ie. under anechoic conditions You eventually hear the music ...inside Your head. There were experiments done, Toole writes about it.
The other way out is to make the room itself play the music. Let the left sidewall play the left channel and the right wall play the right channel.
Again this goal can be achieved in two ways.
The first is so to speak to integrate the L and R channel loudspeakers into the respective side walls. This is the Beveridge approach, Bremen speakers as well etc. and also my side-wall FCUFS concept. The other is to "project" the channels onto the walls - this is the "stereolit with direct sound blocked" approach where the L and R channel signal reaches the listener effectively through the L and R wall reflection exclusively.
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graaf said:
I guess i know, what you mean.
And i can assure you this is not the kind of impression that i am looking for.
In fact it is the contrary, what i achieve in followig my current designs goals. I am far away e.g. from the "only highs in sweetspot" and "very dry" impression that many ESL produce.
It is a new kind of directivity using phase decorrelation as a new and additional "dimension of directivity".
Average DI is rather high (in order of dipoles and cardioids) but there is also reflected sound from midrange on upwards, that is sufficiently flat in energy response up to the highs.
BTW i am not just talking about matters or relying on "wishful thinking" but have also support by measurements.
I guess i already commented on advantages and drawbacks of edge or corner positioned sources.
The Beveridge approach using line sources causes high correlated reflections, i also commented on that.
Of course "possible ways to go" in loudspeaker/room intercation reduce to a small set of compromises unless one is willing to design a source that has appreciable directivity in bass and midrange.
This is IMO the "entrance card" for achieving something considerably different than the commonly accepted situation of music reproduction in small rooms with reflections being
- colored due to non CD multiway designs and "common" crossover frequencies
- bass and lower midrange dominated
- highly correlated to the direct sound
I felt tired and overexposed due to that, so i made something different. Luckily i am not the only one, who thinks this is a way of improving loudspeaker/room interaction.
Most attempts in improvement try to "muddle around" changing common (dynamic, rigid piston) loudspeaker behaviour in those aspects, that seem too expensive to change. Being that cost in development or "bill of materials" in a commercial loudspeaker.
Has the direction, delay or level of a reflection got any importance in Your opinion?
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Beveridge approach:
Both speakers placed hard "left and right", this would not be stereo, as i know and prefer it:
http://i11.photobucket.com/albums/a151/dickoman/647341090_l.gif
If you want a functional stereo triangle using the beveridge approach, with speakers directly at the side walls, then delay and angle of the contralateral reflections is acceptable IMO.
Level and degree of correlation is not acceptable to me, because both being too high. I would like to use diffusers at the side walls with line sources then, but this would tend to reduce highs ... we were talking about this above.
In presence of dipole or cardioid woofers (at least upper bass to lower midrange) aligned in radiation with the longer axis of the room, this would be more easy. But without: Sorry, no entrance card IMO.
The side reflections in Beveridge's approach are still well within the delay which causes e.g. the unnatural "bang" effect typical to line source reproduction in small and untreated rooms, when listening to percussive sounds.
Also i would prefer a more continuously rising early reverb, which also includes mild ipsilateral reflections of sufficent delay.
I am with Toole here in some way ... as these reflections may act as "repair kit" for the interfering direct field. To achieve that you need not too high levels of the "ipsilaterals" (also indirect e.g. via ceiling ) but "smoothness in energy", sufficient energy in highs and "decorrelation".
Both speakers placed hard "left and right", this would not be stereo, as i know and prefer it:
http://i11.photobucket.com/albums/a151/dickoman/647341090_l.gif
If you want a functional stereo triangle using the beveridge approach, with speakers directly at the side walls, then delay and angle of the contralateral reflections is acceptable IMO.
Level and degree of correlation is not acceptable to me, because both being too high. I would like to use diffusers at the side walls with line sources then, but this would tend to reduce highs ... we were talking about this above.
In presence of dipole or cardioid woofers (at least upper bass to lower midrange) aligned in radiation with the longer axis of the room, this would be more easy. But without: Sorry, no entrance card IMO.
The side reflections in Beveridge's approach are still well within the delay which causes e.g. the unnatural "bang" effect typical to line source reproduction in small and untreated rooms, when listening to percussive sounds.
Also i would prefer a more continuously rising early reverb, which also includes mild ipsilateral reflections of sufficent delay.
I am with Toole here in some way ... as these reflections may act as "repair kit" for the interfering direct field. To achieve that you need not too high levels of the "ipsilaterals" (also indirect e.g. via ceiling ) but "smoothness in energy", sufficient energy in highs and "decorrelation".
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graaf said:
OK, reading through this
http://www.moultonlabs.com/more/real_world_of_project_control_room_monitoring/P3/
there are some differences between the control room design proposed there and usual living rooms.
First of all a proposed reverberation time - i know that we should also know the volume of the room - of 0,08s to 0,2s is very different from an average living room, which tends from 0.4s up to 0.6s reverberation time and even more is possible.
This is the main issue IMO calling for a Direcivity Index higher than commonly used in living rooms, especially from bass to midrange.
Moulton allows contralateral side reflections and ipsilateral side reflections as well (though not sketched explicitly). Absorbtion should according to Moulton be mainly at the front wall. Diffusion and possibly Absorption also under the ceiling. There is nothing new under the sun and also nothing that bothers me too much ...
But in a living room that kind of absorbtion and diffusion strategy is simply not viable.
The reflection patterns that i achieve seem on the other hand not too far from those proposed by moulton. Many of that aspects are also propose by different authors IMO.
Of course in my current listening room i have much less front wall absorbtion and thus try to direct the energy partly to the sides: By toeing in my "bass to mid dipoles" and having corner reflectors/diffusers which scatter reflections towards the opposite site a bit (this is concerning the rear radiation). Also i keep a distance to the front wall well above 1.5m (there are some "offset" structures at the front, like e.g. a doorframe).
But i have rather large and thick pillows with some distance to the lower left and right front corners, that provide some absorbtion at the front.
Furthermore i have only little area of porous absorbers at both side walls (though distributed from the main listening zone to the back wall) but allow for direct reflections - "ipsilateral" as well as "contralateral" - from the speaker's positions to the listeng area. And i have no diffusers(!), as my loudspeakers do that sufficiently.
I demonstrate all my speakers in a room that is pretty much "average" for somewhat larger german living rooms in reverberation time. Just the reverberation time in the bass is "lower than usual", this is something i allow myself and my guests for more enjouful listening.
The sidewall absorbers reduce reverb in mids and highs, which is quite constant down to the lowest bass due to dry walls (side, bottom ceiling), that absorb considerably.
What i seem to share with moulton at least is promoting side relfections without "dull" quality but flat energy level in the highs and having ipsilateral and contralateral side reflectons as well.
But that is what i share with Toole too ...
In my room the side reflections are also reduced in bass and midrange, as i have speakers with higher DI and i use as little toe in as possible (nevertheless aiming closely behind the main listening position).
With fullrange dipoles toeing in is a compromise mostly:
Too much "toe in" eats up the advantages in LF impulse response introduced by the dipole, because you will be more exciting the lateral modes in bass.
A dipole subwoofer aligned with the longer axis of the room gives more freedom for toeing in the satellites (even ESL dipoles btw.) without influencing bass response.
My next "decorrelating" loudspeakers will rely on (dipole-) subwooofers and be satellites as "LF combi units" switchable from cardioid to dipole radiation pattern in the range from 80Hz to 400Hz.
The role of the current fullrange bending wave loudspeaker from midrange on upwards will be taken over by an array of mid- tweeters in a special enclosure and arrangement that morphs radiation pattern continuously from "cardioid" to "decorrelated side radiation" from about 800Hz on.
There is also a difference between the vertical and the horizontal pattern, as side reflections are preferred over ceiling and/or bottom reflections.
BTW the radiation pattern doesn't look too different from patterns of some Waveguides ... but the radiation to the sides is much wider than WG, even if reduced in level and more decorrelated from the direct sound.
But again: Not too different from the Moulton proposal either. But it is applicable in a living room without extensive absorbtion.
Kind Regards
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Thanks! It looks very interesting and it looks like a genuine invention, a real something.
Please do not be so secretive
Thanks! It looks very interesting and it looks like a genuine invention, a real something.
Please do not be so secretive
Thanks graaf
,besides the "main concept" there are many many solutions implemented "to make it work smoothly".
E.g. i won't be showing the motor units (i call them "driver boxes") which are placed at the rear of the segmented panel.
Each panel segment is operating fullrange, moving together "as a whole" for low frequencies.
The "modal overlap factor" is higher than in any musical instrument's soundboard built so far, that includes also grand pianos from the worlds-famous manufacturers. Im not kidding here ...
My initial motivation in making it work fullrange was forcing me to achieve a high modal overlap enabling a smooth bass response.
This results - as a bonus - in a modal overlap in critical midrange which is about 3 orders of magnitude higher than e.g. in a manger type bending wave transducer, where you can count the main resonances up to say 1 Khz easily in the impedance curve.
Thus my transducer is based on modal behaviour but nevertheless does not "show" resonant behaviour.
Material composites, suspensions, dampers all that stuff took years to develop: Starting from ideas and then going into a practical implementation.
That speaker is similar to a musical instrument - although behaving like the contrary - in the making process and uses grown and selected wood as a core material for the panels.
Selection needs a second set of panels at minimum, although i have meanwhile written a software predicting and controling each panel's parameters during manufacturing.
That is the price to pay, when working with naturally grown materials ...
you will be a kind of instrument maker in the end. If someone would have said i will be designing and making such a loudspaker some years ago, i would have loughed out loud and send him away ...
Nevertheless i can achieve a pair matching equally well or even better, than with using "conventional drivers". But don't ask for the effort, it is insane.
The immense effort made me think, how similar behaviour may be achieved with less effort in manufacturing.
Now i am at the start with said new multiway design comprising a new kind of array, which i refer to as "virtual bending wave transducer".
When thinking about this enough, one can get to the conclusion, that bending wave loudspeakers are not needed to mimick their own behaviour and do it - possibly - even better than "the physical original":
What we want is a radiation pattern in the end, not more not less.
And now what happens ?
After years of "non interest" for my fullrange bending wave design and me finding an alternative, which is easier to manufacture - i am planning also a finished version of the mid-tweeter panels for the DIY community - there are people now asking for the "music instrument" fullrange one ...
It has been said:
"Be carefull regarding your wishes, as they could be fulfilled"
(Which is possibly a bad "literal" translation from german ...)
Kind Regards
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OK, back to the "loose ends".
I "believe" - kind of - the contrary here:
There ought to be sufficient phase coherence in the direct sound first, however the room reflection's properties may be in a given loudspeaker/room setup.
And i feel backed by "common listening experience" and also the studies concerning "listener preference" conducted by Toole:
We need an on axis response that is considerably flat and smooth. Group delay should prefereably stay within sane limits, which depend on the frequency range.
Having "all early reflections" - as you say it - closely resembling the direct sound, this means they have also nearly the same spectral content.
To me it would be sufficient to say "the spectrum averaged over the first N reflecions should approximately resemble the spectrum of the direct sound"
This sems far more realistic to me and may be achieved with loudpeakers having balanced energy response and rooms that have reverberation not too dependent from frequency, e.g. not "overdamped" in highs.
The Shinn-Cunningham paper shows to me, that "identity" in spectral content is not needed - in a leading and a following binaural pulse - for the precedence effect to occur.
I mean precedence here, different from the common anglo saxon reading, as applying to larger delays than those for summing localization:
Precedence that supresses the direction of arrival of "later" binaural incidents.
As the effect is also an "interband" effect, postulating reflected impulses to be "identical" or "very closely related" to the direct sound, seems overdone and also impractical for the underlying perceptive mechanism to be of use for orientation in real acoustic environments.
Furthermore a limit in delay about e.g. 1ms for summing localization, does not imply the earbrain taking only this delay as a processing time for
- estimatition of DOA (direction of arrival)
- summing localization
- suppression of DOA of "lagging" reflections by precedence effect (here: "german" kind of reading, meaning precedence effect as being different from summing localization)
Stereo is actually based on summing localization, nevertheless we want room reflections not to contribute to (virtual) DOA estimation of phantom sources.
Postulating "close match" for "every" single reflection from the listening room is not in line with the goal, DOA of reflections being "suppressed" instead of "contributing" to DOA estimation of phantom sources.
Thus "directional information" from the - early - reveberant field itself should IMO be "smeared" by breaking up the interband envelope correlations between direct and reflected sound in a controled manner in the way i desrcribed in the beginning of this post.
By doing so, the stereo reproduction gets more tolerant due to reflections "too early" which may arise from loudspeakers placed to close to the walls.
Also it seems reasonable that delay boundary from "summing localization" to "precedence" is not sharply defined and may depend on spectral content and also envelope of presented stimuli - via stereo setup or binaural presentation - themselves.
There remain nevertheless some conditions due to "shapeliness" of room reflections, as the spectrum of early reflections should in sum match the spectrum of the direct sound approximately (no audible coloration of the reverb, whenever possible).
Kind Regards
Kind Regards
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LineArray said:
@graaf:
That using diffusers to achieve this - in connecton with most conventional loudspeakers - may lead to a "dull" quality of the early reflections may indeed be a technical problem (as the "diffuser" figure cited from Toole illustrates) with many common loudspeaker designs, which radiate considearably less energy in highs than from bass to midrange.
But a technical issue occuring with some common equipment, does not imply that basic strategy proposed above being wrong: It just points towards issues to be solved, when going that way IMO.
Summing Localization, Precedence Effect
http://en.wikipedia.org/wiki/Precedence_effect
http://de.wikipedia.org/wiki/Präzedenz-Effekt
Kind Regards
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graaf said:
Is there really such thing like "colored off-axis behaviour" ?
I mean from perceptual point of view ...
As the off axis performance at larger angles is literally "reflected" by the room solely.
If
- the sum of early relections is "fairly neutral" in spectrum and
- extremes are avoided from certain important directions of reflection and
- you have also "kind of" symmetry between left and right channel
... then our earbrain most probably has "nothing to complain about".
We also have to take into account that "wide radiation" should mean here:
"Wide radiaton in upper midrange and highs".
Because that is the range where the majority of the speakers tested by Toole are most likely to differ, "wide radiation" from bass to midrange is the cost saving "de facto industry standard" anyhow.
To think about:
Mirror sources of the room would also sound different - less dull - when there is higher DI from bass to midrange.
Kind Regards
graaf said:
Hi graaf,
if we take 0.4m as an approx. wavelength around 800Hz, then objects in front of a wall having depth of a decimeter will have considerable effect already.
In a more heavily furnitured room - e.g. having bookshelves at the side walls - those structures may work rather well as diffusers even down to the lower mid / upper bass range.
The problem pointed out by Toole was, that a diffuser has a lower cutoff frequency depending on the depth of the structure, where the incident wavefront is not diffused sufficiently anymore, which leads to a highpass filter effect under the emergent angle then.
diyAudio
Lacking diffusivity up to lower midrange may be compensated partly by "higher than usual DI in the bass and lower midrange" range as i pointed out, to have e.g. the early reflections from the sides more neutral:
As deep and large area diffusers cannot be postulated in a usual living room, IMO at least mid bass to lower midrange should be radiated with say DI > 5dB.
A loudspeaker additionally having decorrelating (diffuse) radiation at larger off axis angles - say from 800Hz ... 2000Hz on upwards - while keeping the DI from midrange approximately in the highs too, will have a considerably flat energy response and tend to produce a loudspeaker/room interaction "as if the room was more heavily furnitured" even with e.g. the side walls being smooth.
If the room you place this loudspeaker in will really be more heavily furnitured and also have some broadband absorption, the acoustic result will even improve: But the loudspeaker's proposed builtin behaviour will present no drawback at all, when improving the room's acoustics.
Regarding considerably flat and smooth energy response i am well with Toole. Additionally i go for
- higer DI in bass to midrange
- introducing diffusivity in highs just for larger off axis angles
to meet the requirements of typical living room's acoustics, which are in brief
- higher reverberation time than control rooms
- potential lack of diffusivity that comes due to modern style in furniture
in a more realistic way, than common loudspeaker design does.
Kind Regards
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very interesting!
which is also a means to an end which is a specific set of reflections
Can Your Flächenstrahler be integrated into room walls or just on-wall mounted?
I ask because I am interested in a visually unobtrusive loudspeaker design, it's Hartley's ideal of "audio as a room service like central heating".
graaf said:
When using a flat cavity behind the bending wave "Flächenstrahler" type to mount it "inwall" you loose 2 options:
- fullrange operation, as you will need a separate subwoofer then
- toe in is not possible anymore, or will be fixed
also
- DI in bass and lower midrange will rise ... as the system is designed as a free standing dipole radiator in bass and midrange
As the effort in manufacturing the fullrange bending wave type is very high, i would not recommend it for wall-mounting, as you loose some interesting properties IMO. It was more aimed in being a replacement for more conventional High End ESL or magnetostatic designs, as it needs just smaller area to operate fullrange and at appropriate levels.
The new "virtual bending wave transducers" will be flat panel arrays - around 6cm in depth - which could be more easily mounted in front of a wall or even "inwall". But the flat panel arrays are not fullrange, current prototypes operate from 400Hz upwards having dynamic headroom comparable even to waveguided designs.
But with wall mounting you loose the builtin cardioid operation from crossover region at 400Hz on upwards. Of course the rear sound source needed for that cardioid operation can be "closed" without problem.
The flat panel array for mid and high frequencies can optionally be integrated to a floor standing cardioid satellite system.
Of course it can be integrated with other bass and midrange concepts as well. But the panels should be toed in to the listening seat, even pointing slightly behind the main listening seat or directly at the farthest seat is possible.
Thus wall mounting without toe in will restrict the listening position (for real stereo and "critical listening"), as my systems are "higher DI than usual" designs, even if there is a wide and decorrelated radiation in highs (but of reduced level), which gives you the notion of "sparkle" and "non dullness" even in the "easy listening" zones beside the main listening area.
Kind Regards
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@graaf:
Neverhtheless i can imagine the mid- to hirange panel arrays integrating to your preferred "FCUFS" aproach a lot better, than most conventional tweeters will do.
But such a panel should be directed at the listener and not be radically "upfiring".
Directivity and diffusivity will make it more immune due to "very early reflecions" than using e.g. a usual dome tweeters close to a room's sidewall or close to the edge of floor and sidewall, as can be seen in many examples for loudpeakers in this thread.
Attached pictures show some "fictional" options ...
First picture was already "outdated", but variant "A" could be a "blueprint" for integrating that panel into an "FCUFS". The panel shown in sideview here.
Second and third picture shows possible modular variants in integrating the panel with compact cardioid woofers, to make up cardioid satellites from 80Hz on upwards.
The cardioid woofers will cover the range from 80Hz to 400Hz. For sufficient dynamic headroom in a larger living room, 2 cardioid modules will be needed, due to listening habits regarding level.
Kind Regards
Neverhtheless i can imagine the mid- to hirange panel arrays integrating to your preferred "FCUFS" aproach a lot better, than most conventional tweeters will do.
But such a panel should be directed at the listener and not be radically "upfiring".
Directivity and diffusivity will make it more immune due to "very early reflecions" than using e.g. a usual dome tweeters close to a room's sidewall or close to the edge of floor and sidewall, as can be seen in many examples for loudpeakers in this thread.
Attached pictures show some "fictional" options ...
First picture was already "outdated", but variant "A" could be a "blueprint" for integrating that panel into an "FCUFS". The panel shown in sideview here.
Second and third picture shows possible modular variants in integrating the panel with compact cardioid woofers, to make up cardioid satellites from 80Hz on upwards.
The cardioid woofers will cover the range from 80Hz to 400Hz. For sufficient dynamic headroom in a larger living room, 2 cardioid modules will be needed, due to listening habits regarding level.
Kind Regards
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