Stereolith Loudspeakers Question

[Elias]

Hello Radugazon,

How's your tests going on?

The SL really needs the reflections, I will never tell something else.

I agree! As is my current understanding on the subject, in a room it totally relies on the reflections. Direct sound is an error!

The reason I have to use pillow.. maybe because my 3" drivers don't beam enough and there is a leakage of direct sound.

It may well be that there must be a definite relation of the levels of side wall reflected sound and direct sound for proper operation. Depending on the level of direct sound leakage and the distance to the side walls and diffusiness of the side wall reflections and absorptioness of the side walls and ... It can be an optimisation task!

- Elias

 

[Tubamark]

to put it shortly - what is the value of such defined fidelity? for a human person, music lover seeking enjoyment in music at home?

Value is subjective, just like 'realistic', etc. That's exactly why I prefer my understanding of fidelity--It brings some metric to the madness. To answer your question only for myself, the value of fidelity to me as a music lover in my home is that in my limited experience, speakers that disappoint me (whether initially, or after the honeymoon) can invariably be traced back to some form of measurable distortion - a midrange peak, harmonic distortion, lobing, mixed directivity, etc. While I haven't measured every speaker I've liked, I can say that I tend to prefer speakers that are objectively more faithful to the source material. For me, the correlation is strong enough for me to include this factor in my decisions. It is by no means the only consideraton, but is among essential means to an end.

I suspect that I've been misunderstood on the whole, based on a few posts addressing rather specific concerns. In reality we probably agree on more than we disagree.

Contrary to some assumptions out there, I love to experiment with things just to see what the subjective results are*. I just always keep in mind the fact that there's a reason why Ebay, Audiogon, etc are always full of nearly-new gear that music lovers are selling. It's not unusual to see a rave review with phrases like "the search is over". . . and a few months later find the same person selling their Holy Grail because they have since found the next real Holy Grail.

For me, Fidelity-as-accuracy provides some objective criteria, a compass for my quest to greater enjoyment of recordings and the DIY process. The compass doesn't dictate the steps I take, but it does let me see (if I value what it reveals) when I'm pointing in a direction that will never lead to my particular destination.

such abstract, technical concept of Hi-Fidelity I consider to be a very unfortunate deviation from the original concept

abstract technical? 'zat like confused certainty?

We've now both cleared-up our understandings of the term. Yours has some merit, as does mine. Neither of us are alone in our different understandings of "fidelity". Going forward I will say "accuracy" or some other descriptor to reduce confusion.

it was H.A. Hartley who "invented the phrase "high fidelity" in 1927 to denote a type of sound reproduction that might be taken rather seriously by a music lover"

We can all agree on that much.

-- Mark

* I did indeed do a stereolith mock-up a year ago. It had problems, and I worked-out the causes. That experience (not assumptions) was the basis for my explanations about the tradeoffs of the stereolith approach. The fact that the real invention does seem to operate just as some suspected is a testament to the fact that much of audio is not a mystery, just misunderstood.

 

[graaf]

Could it be that you don't necessarily need that stereolith construction, but only some decent polar response of your system, including a nice share of ipsilateral and contralateral reflections?

yes, of course, a flooder for example does it too
more tests are needed, and what will do for a particular is probably also a question of personal expectations, listening habits, taste and so on

best!
graaf

 

[graaf]

I agree! As is my current understanding on the subject, in a room it totally relies on the reflections.

yes, but NOT on any specific reflections pattern

my old analogy is that it is a kind of sound projector and the room is a screen
BUT no special screen is needed

here is why in my opinion:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-19.html#post2490830

Direct sound is an error!

in a sense, for me both back-to-back and Beveridge sidewall placement are method of "acoustically hiding speakers in the room"
this is what back-to-back with sufficient directivity and/or with direct sound additionally blocked does – because of its "bipolar" directivity our hearing is unable to locate the speakers themselves as a distinct sources of sound – they are hidden, they disappear, "the air is playing music"
this is the essential characteristics of this design

http://www.diyaudio.com/forums/multi-way/121385-loudspeakers-room-system.html#post1486048

Harold Beveridge proposed just a different solution – an alternative method of achieving the same result

The reason I have to use pillow.. maybe because my 3" drivers don't beam enough and there is a leakage of direct sound.

yes, that was also my hypothesis:

in fact my aim was to create an ambiopole that would require minimal physical barier according to the formulas given
(...)
I have no certainty as to the principle operating here
I supposed that it has to have something to do with directivity of box speaker, of a dynamic driver on a baffle

back-to-back is the ultimate fidelity of spatial sound reproduction from two channels, it reproduces exactly what is in the recording, soundstage spread is directly proportionate to the spatial cues contained in the recording

three years ago I wrote:

The reviewer writes:
"Profondeur et hauteur d’image musicale hors du commun" i.e. "extraordinary depth and height of soundstage" and at the same time:
"Image stéréo étroite" i.e. "width of the soundstage is shortened"

this conclusions are highly symptomatic of the main problem of this design

the problem with this "dummy head stereo" or „pseudo-ambiopole”, as I like to call it, is that it reproduces EXACTLy what is in the recording
It means that "it produces no artificial soundstage"

on the other hand many or even most of contemporary recordings are made with an assumption that they will be reproduced in a standard stereo triangle and thus they rely on the loudspeaker spread in such a triangle to produce the width of the soundstage
such a soundstage created by loudspeaker spread in a stereo triangle is of course completely artificial because it has nothing to do with natural spatial cues for distance perception

pseudo-ambiopole is reproducing as faithfully and as accurately as possible all the spatial cues encoded in the recording ("natural" or "artificial")
but many recordings give little or no spatial cues for soundstage width because the width "is to be created by" "spreading of the loudspeakers in a typical stereo triangle"

when there is little spatial cues for soundstage width in the recording pseudo-ambiopole produces "shortened soundstage width" as described by that French speaking reviewer: "Image stéréo étroite"
and when there is NO spatial cues for soundstage width in the recording pseudo-ambiopole produces literally NO SOUNDSTAGE WIDTH, the soundstage collapses completely
and this is quite catastrophic and a fatal flaw of this design from practical point of view

BUT precisely speaking the device is right, only recordings are crappy

these recordings are crappy because they give just position cues of virtual sound images and no real spatial cues
such recordings doesn't work with back-to-back

best!
graaf

 

[markus76]

You must get rid of the direct sound for the principle to work correctly.

I don't believe this is true. All you need to do is raise lateral reflections above a certain level. Blocking direct radiated sound is one way to achieve this but it also creates a hole in the middle with two distinct sound clouds to the left and the right.

 

[graaf]

I don't believe this is true. All you need to do is raise lateral reflections above a certain level. Blocking direct radiated sound is one way to achieve this but it also creates a hole in the middle with two distinct sound clouds to the left and the right.

perhaps in extreme case this can happen

although I never tried to block the direct sound myself

OTOH Brociner et al. seemed to claim specifically to the contrary:

Deflector baffles in the form of doors are used to reduce the sound reaching the listener directly from the speakers. The sound fields so created are continuous, and thus provide good -center fill- without additional speakers.

from:
AES E-Library A Compact, Single-Cabinet, Stereophonic Speaker System

Markus, please let me take this opportunity to draw Your attention to couple of my questions posted above that You haven't asnwered yet, in case You didn't notice them:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-40.html#post2525359

http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-40.html#post2525362

 

[Elias]

a hole in the middle with two distinct sound clouds to the left and the right.

That is the conventional stereo triangle ! We don't want that

My 3" elements are simple too small to have required directivity, which results too much of direct sound. However, my soffa pillow sounds quite nice ..


- Elias

 

[Rudolf]

I don't believe this is true. All you need to do is raise lateral reflections above a certain level. Blocking direct radiated sound is one way to achieve this but it also creates a hole in the middle with two distinct sound clouds to the left and the right.

I would add that it's not only a certain level. You need a reflection which resembles the original in frequency response too. Some faint and dull echo would not help much.

That is the conventional stereo triangle ! We don't want that Elias

You don't want to tell us that the conventional stereo triangle can't be filled with all sorts of individual phantom sources - at all positions between the left and right speaker!?

Rudolf

 

[markus76]

Spaciousness or imaging, that is the question.

 

[graaf]

Spaciousness or imaging, that is the question.

quite philosophical question BUT perhaps something is simply wrong with the TIE fighter setup or with Your speaker-room interface?

because I got both - spaciousness AND imaging, Elias too:

When there is a phantom image, and I turn my head to face the perceived phantom the image is even more convincing and realistic. I've been turning my head everywhere for three days now looking at the empty air and the sound is coming from there!

again please Markus - let me take this opportunity to draw Your attention to couple of my questions posted above that You haven't asnwered yet, in case You didn't notice them:

are they working in one volume or is there any kind of partition inside? from:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-33.html#post2523007

what is exactly pretty amazing about it?
and
Do You mean AVR + an upmixing algorithm?
from:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-40.html#post2525359

and
Could You be a little bit more specific? Which conlusions exactly?
and
What is more to it?
and
which book?
from:
http://www.diyaudio.com/forums/multi-way/10962-stereolith-loudspeakers-question-40.html#post2525362

best!
graaf

 

[Rudolf]

Spaciousness or imaging, that is the question.

Would 180° imaging pass off as "spaciousness"?
Otherwise I could just rotate the dipoles 90°.
Or place them perpendicular to the side walls. That would be a sort of "inverse" Beveridge placement imho.

But getting serious again: What sort of imaging is a stereolith loudspeaker expected to deliver? Is it about widening the stereo base or about filling the room with sound?

Rudolf

 

[graaf]

for all those experimenting with back-to-back - an important information perhaps:

in fact (perhaps I have already told the story somewhere above) I tested three versions of back-to-back boxes, the first was just just 13 cm wide
(...)
the first one was a complete failure

it seems that around 20 cm or more width is really needed, too narrow back-to-back basically doesn't work

 

[graaf]

Would 180° imaging pass off as "spaciousness"?

can You define the concept of spaciousness that You subscribe to?

Otherwise I could just rotate the dipoles 90°.
Or place them perpendicular to the side walls. That would be a sort of "inverse" Beveridge placement imho.

but what's so funny?
perhaps it will surprise You but it was indeed done before and similarity to Beveridge was noticed:
Stereo Unlimited tweak

But getting serious again: What sort of imaging is a stereolith loudspeaker expected to deliver? Is it about widening the stereo base or about filling the room with sound?

well, perhaps the adjective complete imaging would be the most appropriate - an alternative sound space opens before the listener, it's width, depth and also height is not restricted by room boundaries and it is filled with stable, palpable sound images, and there is continuity of ambient sound, those images are not floating in a void

so especially for You Rudolf I quote again:

When there is a phantom image, and I turn my head to face the perceived phantom the image is even more convincing and realistic. I've been turning my head everywhere for three days now looking at the empty air and the sound is coming from there!

It is just as Elias wrote - I have heard it too, I know - this is crazy but this is how it sounds

best,
graaf

 

[Rudolf]

can You define the concept of spaciousness that You subscribe to?

I was asking for YOUR definition/concept - not mine. And please no longer than four sentencies.

but what's so funny?
perhaps it will surprise You but it was indeed done before and similarity to Beveridge was noticed

No surprise in that. I believe EVERY serious dipole user has tried that at some time. And the outcome WAS funny - at least to me.

well, perhaps the adjective complete imaging would be the most appropriate - an alternative sound space opens before the listener, it's width, depth and also height is not restricted by room boundaries and it is filled with stable, palpable sound images.

"Holographic" comes to mind. Does it mean that the sound images (I believe you mean a sort of "locateable phantom sound source") stay in their original place, regardless whether I am in a "sweet spot" or walking from the left to the right wall of the room?
In most other respects that you describe, there is nothing that I find lacking in my actual system.

so especially for You Rudolf I quote again: ...
It is just as Elias wrote - I have heard it too, I know - this is crazy but this is how it sounds.

Thanks for that extra special service.
But I am not sure, what exactly Elias is referring to. I don't believe he is talking about a phantom image following his head movement (like with headphones). He probably is talking about phantom images being not destroyed by turning his head. I feel happy with him that he now has this great experience too - I carelessly had regarded that as a matter of course in a really good system.

Rudolf

 

[ScottG]

I agree! As is my current understanding on the subject, in a room it totally relies on the reflections. Direct sound is an error!

The reason I have to use pillow.. maybe because my 3" drivers don't beam enough and there is a leakage of direct sound.


- Elias

Again, try it outside - it still works there. It may however be *enhanced* by reflections.


Please do not make the mistake of perceiving direct sound as some highly limited frontal axis.



Note that a barrier device in front does NOT attenuate the entire direct sound field, nor does it attenuate at all freq.s (..just primarily those higher in freq.).


The reason *why* a frontal barrier works is "wrapped-up" in why the stereolith works - lower effective levels of "cross-talk" (and combing) in the pressure level range of hearing. i.e. your left ear hears less of the right channel and your right ear hears less of the left channel (..at higher freq.s).

 

[graaf]

I was asking for YOUR definition/concept - not mine. And please no longer than four sentencies.

Actually You were asking for Markus' definition/concept. And I am interested in Yours.
two sentencies

No surprise in that. I believe EVERY serious dipole user has tried that at some time. And the outcome WAS funny - at least to me.

it could be a matter of small details not taken care of, of specific room-speaker interface, of dipoles being not all the same, of unfortunately unsuitable recording, of subjective expectations etc.

anyway this tweak worked well for many Magnepan users - what's the point of -ing at them?

"Holographic" comes to mind. Does it mean that the sound images (I believe you mean a sort of "locateable phantom sound source") stay in their original place, regardless whether I am in a "sweet spot" or walking from the left to the right wall of the room?

yes, that is correct

In most other respects that you describe, there is nothing that I find lacking in my actual system.

could be a matter of subjective expectations determined by Your specific point of reference, but certainly nobody is criticising Your system specifically

But I am not sure, what exactly Elias is referring to. I don't believe he is talking about a phantom image following his head movement (like with headphones).

wow! that would be something! imagine effects of turning 180°!

I feel happy with him that he now has this great experience too - I carelessly had regarded that as a matter of course in a really good system.

great! I am impressed, Your system is really good!

best,
graaf

 

[graaf]

The reason *why* a frontal barrier works is "wrapped-up" in why the stereolith works - lower effective levels of "cross-talk" (and combing) in the pressure level range of hearing. i.e. your left ear hears less of the right channel and your right ear hears less of the left channel (..at higher freq.s).

I believe that You are right! In fact it was my old theory of pseudo-ambiopole.
Perhaps exactly therefore using less directional speakers or making the box too narrow can create problems.

best,
graaf

 

[markus76]

Again, try it outside - it still works there.

Did you test that yourself? What did the setup look like?

 

[Rudolf]

Actually You were asking for Markus' definition/concept. And I am interested in Yours.
two sentencies

OK, now that you point to it ... Yes, my question had to be understood to be explicitely to Markus. But it was intended to be directed to all participant.
To me "spaciousness" would be the immersion into a space of sound surrounding me like in a church or a concert hall. What I get at home is only (or at least) a wide (front wall dissappears) "window" into a room of spaciousness.

it could be a matter of small details not taken care of, of specific room-speaker interface, of dipoles being not all the same, of unfortunately unsuitable recording, of subjective expectations etc.

Yeah, personal bias or local deficits always have to be considered as an individual factor.

anyway this tweak worked well for many Magnepan users - what's the point of -ing at them?

Last time I heard big american planars they presented "images" that reached half across the front wall. By turning them around even the last piece of "imaging" would have been sacrificed for "spaciousness". I agree that those planars might have improved in the last five years.

yes, that is correct

Astonishing! Markus, is that what you experience with the stereoliths to?

could be a matter of subjective expectations determined by Your specific point of reference, but certainly nobody is criticising Your system specifically

Oh, I did not expect anybody having critizised my system.

Rudolf

 

[Radugazon]

Hello Radugazon, How's your tests going on?

Hi guys,

Actually I am on this thing and I am facing some difficulties.