Unconventional Techniques for Achieving Oustanding Stereo Imaging

[Elias]

neither I am interested in total direct sound,

How is your direct sound project progressing ?

and in Poland those drivers are available under original "Tesla" brandname as "ARN 100-60/8" for just pln 30 that is around EURO 8.5 each

perhaps I would give them a try myself
after all it is only around EURO 350 for 2x20 drivers
I ony have to find a good cabinet-maker

best,
graaf

 

[graaf]

How is your direct sound project progressing ?

You mean Tesla Sweet Sixteen?

the Tesla thing (here on Polish audiostereo forum we called it "a mattress") was just a proof of concept experiment and as such it was successful, just as Thornspawn's 10x10 here

but I had to abandon it - as I told You before - life circumstances changed

besides, anyway, I was really never interested in having this in my room, I was already into low directivity things by then

it was pure if not me who else kind of experiment

ps.
post #1404 please

 

[Pano]

Hey Graaf, you could take all those little drivers and build a Keele shaded array. It's a pretty cool speaker.

 

[a_tewinkel]

Second that

 

[graaf]

c'mon guys! Keele's array will have to wait

because as el`Ol has revealed I am

working on a three-way flooder.

however the word struggling would be much closer to the factual situation

 

[LineArray]

not agreed

not surprised ...


I do not feel very comfortable in saying that, because i guess many of us like solutions
which can be derived from knowledge directly, being that room acoustics or psychoacoustics
involved ... but the question
"What is the ideal directvity pattern for stereo speakers according to your setting?"
may be easier to answer.

And we have to admit that besides room acoustics the "preferred mode" of listening plays a
role ("critical" vs. "enjoyful").

(Despite the ceiling flooder of course, which fulfills all criteria concerning "critical" and "enjoyful"
listening as well in rooms of arbitrary size and a great variety of reverb characteristics.)

If we were to design a form, were some basic acoustical data of the room (RT vs. frequency) is
filled in and also the "preferred mode" or function of the speaker, then some proposals could be
derived. Unfortunately i feel that we could not even agree completely on that rules of thumb,
as we see a lot of diversity in opinions. OK, "reading Toole" yields some orientation, but i doubt
that alternative concepts having higher DI especially in upper bass and midrange really had the
same "weight and chances" in Toole's studies.

 

[graaf]

(Despite the ceiling flooder of course, which fulfills all criteria concerning "critical" and "enjoyful"
listening as well in rooms of arbitrary size and a great variety of reverb characteristics.)

oh Oliver, how can You!!

I think that we all know that this qualification was really offensive in it's total needlessness as it goes without saying and should be obvious to all

 

[Elias]

have You got any ideas for practical implementation of Your ideal setup - directional <1 kHz, stereolitic >1 kHz?

Yes I have got ideas !

Now this journey has got me to the crossroads: Stereolith vs. Beveridge on wall line array ?

They appear similar, in the essential part, that they generate field coming from the side without 'early reflections'. Let's make the beveridge as a sparse floor-ceiling line array and it mimics the side wall reflections of a stereolithic projection. Only that the beveridge don't have direct low freq sound from the center, but it may be ok since stereo works at least on the midrange so beveridge may be better at low midrange than stereolith because stereolith not capable of imaging at low midrange.


- Elias

 

[markus76]

Yes I have got ideas !

Now this journey has got me to the crossroads: Stereolith vs. Beveridge on wall line array ?

They appear similar, in the essential part, that they generate field coming from the side without 'early reflections'. Let's make the beveridge as a sparse floor-ceiling line array and it mimics the side wall reflections of a stereolithic projection. Only that the beveridge don't have direct low freq sound from the center, but it may be ok since stereo works at least on the midrange so beveridge may be better at low midrange than stereolith because stereolith not capable of imaging at low midrange.


- Elias

Those two approaches are essentially different. One is a center with ipsilateral reflections whereas the other is defined by a large stereo triangle with reflections coming from the front and contralateral wall. I'd consider only the former as desirable if the goal is increased spaciousness.

 

[el`Ol]

Elias,
could this be a tweeter for a stereolith?
http://www.expolinear.de/images/stories/expolinear rt-10 pro.pdf
Highly directional and enormous sensitivity.

 

[graaf]

When I started this thread, I hoped we would get several conclusions, i.e. different directivity patterns and room lay-outs for different well-defined tastes in sound quality.

It's of course difficult to have these online discussions in a structured way. There are many different people with just as many different views and anybody can say whatever they want whenever they want. There is no chairman to keep the discussion on track - which would moreover be an impossible task because this thread runs 24/7. There have been many very good contributions, though. However, they tend to increasingly get snowed under in off-topic chatter. In my opinion all the stuff about flooders, stereolith and all those other controversial topologies don't belong in this thread. I am getting a bit annoyed by having to read several pages each time I check this topic and seeing the same few posters repeating themselves. And I know I'm not the only one who feels this way!

I was hoping to get to some kind of consensus here. Then putting forward controversial ideas and ideologies all the time isn't helping. I'm not saying those issues aren't worth discussing, but please do that in a different thread.

I respect Your point of view, however don't You agree that Your qualification of the topic is a bit... er... late?
now when we are beyond post #1500 You would like to ask some users to leave the thread??

now it just is ideal directivity pattern for stereo speakers thread
it's too late to change it - I am sorry

please start a new thread - this time more explicitly titled for example: "ideal directivity pattern and room lay-outs for conventional forward firing stereo speakers" - and for my part I promise I will not interfere as I am not interested in this kind of stuff anymore

 

[graaf]

the beveridge taking the exact place of the virtual speaker created by a side firing, without considering immediately their own reflection paths.

nice scheme, nice colours, quite a pleasure to look at! thank You!

OTOH - too many colours for Markus I am afraid...

 

[graaf]

I understand and respect your point of view too. However, I have before hinted to please not push your controversial views too much, because I would like to try and come to some kind of general consensus. You have a strong way of expressing yourself and it sometimes seems as if you discard anything but your own point of view. Also you are the prime contributor of this thread with respect to the number of posts, so the thread drifts more and more off the original topic. Some other contributors now seem to to have left this thread and I regret that.

again I am sorry - I have misunderstood the original topic
as an excuse I can say that flooder is mentioned in just 82 for 1524 total post, this included, and stereolit which was brought here not by me but by Elias in just 90 (with other related terms like "side-firing" etc.)
it makes about 11% total of the thread posts so it can hardly be said that the thread has been hijacked

perhaps contributors that now seem to have left this thread (and I regret it too) simply had nothing more to contribute with (another thing which I regret)

take a look at some conclusions offered:

there seems to be no answer to the question (also of this thread)

So the answer to the original question might be "It depends on what you want to achieve."

Thats the answer to every question actually.

such was their consensus, no wonder they have left

 

[graaf]

I often see figures tossed around like Linkwitz's 6ms to first reflection, or Earl's 10ms to first reflection, but they frustrate me no end because they seem completely unrealistic.
...
Just looking at my current room, 3.45m wide x 4.8m long. Listening distance is dictated to a fixed 2.5 metres
...
Lets work out some numbers.

The right speaker is 0.7m from side-wall to centre axis of the speaker - yes, much closer than I would like but I have no choice. At the listening position this gives me a reflection arriving at 2.74ms, far short of 6-10ms.

The left speaker is 0.9m from side-wall to centre axis, giving 3.69ms. Better but still well short of the target.

...
To achieve 6ms delay for side-wall reflections, the speakers would need to be ~1.4 metres from the side-wall, so to maintain a 2.5 metre speaker separation (for 60 degree separation at a 2.5 metre listening distance) I would need a room that is 5.3 metres wide. My room isn't even 5.3 metres long, let alone 5.3 metres wide.

6-10ms is a fantasy for most people, so basing speaker design assumptions around being able to achieve this seems ludicrous.
...
a large percentage of people will only ever see side-wall reflections with a maximum of say 3-4ms, then other means are necessary to achieve satisfactory results
...
If you can't increase the delay of side-wall reflections enough, your only other recourse is to reduce their amplitude. You can do that either with side-wall treatment, or speaker directivity.

seems to be hopeless situation... but wait! yes, You can... well, yes, it sounds a bit like Obama ...but it is not bulshit!

have You ever heard of Beveridge placement?

What about the floor bounce ? The mid-bass driver is currently 75cm above the floor, that means the floor bounce is delayed by 1.5ms. Even if the mid-bass driver was 90cm above the floor, floor bounce would only increase to 1.77ms.
...
Ok, I'll give you that some fortunate people have much larger living rooms
...
however I don't see how that gets around the floor bounce.

No matter how big your living room is the elephant in the room is the floor bounce arriving somewhere in the 1.5-2ms range, so how is a true 6ms to first reflection even possible, let alone 10ms ? Nobody seems to pick up on this point.
If the floor bounce is ever present,
...

have You ever heard of a flooder? [please excuse me keyser! ]

Have You put me on Your ignore list?

Good point.

and You too?
...well I can I understand ignoring me but why ignore good old Harold Beveridge R.I.P. a respected engineer after all??!

 

[DBMandrake]

seems to be hopeless situation...

Achieving 6-10ms is a hopeless situation, achieving good results is not hopeless. A reasonable amount of directivity and a bit of natural (high WAF) diffusion along the side-walls to break up the specular reflection can lead to good results even in a small room.

have You ever heard of Beveridge placement?

have You ever heard of a flooder? [please excuse me keyser! ]

Have You put me on Your ignore list?

No you're not on my ignore list, but any system which relies on the reflections from room boundaries as a primary source of sound for the listener is not on my list of satisfactory solutions, and this also applies to Markus's suggestion in the previous post. (I'm not sure how it solves the problem anyway...)

There are a lot of things wrong with using a wall or large reflector as a primary source of sound as if it were a video projection screen, two of the top problems are that no two rooms are alike, (no consistency in performance from room to room) the second is that a wall introduces its own colouration.

A wall is not an idealised reflector, depending on the surface finish the reflectivity/diffusivity varies with frequency, but worst of all it is a resonant device at lower midrange/upper bass frequencies. Quite a bit of what sounds like "woody" cabinet resonance on some speakers can turn out to be resonances in the panels of the walls behind and to the sides of the speakers - something which goes away when the speakers are sufficiently spaced away from the boundaries.

No, I want to hear the direct sound from the speakers, with a moderate amount of diffuse and unobtrusive ambience from the room. I don't want the room boundaries to be the apparent source of the sound.

 

[graaf]

any system which relies on the reflections from room boundaries as a primary source of sound for the listener is not on my list of satisfactory solutions

I want to clear up a misunderstanding - Beveridge placement does not rely on the reflections from room boundaries as a primary source of sound for the listener

here goes the scheme of it (reposting picture already posted few posts before by Markus):

An externally hosted image should be here but it was not working when we last tested it.

the contralateral side wall reflections, front wall and back wall - all can be quite easily delayed by as much as 6 ms in a moderately sized room, and even beyond 10 ms in a bit bigger

use line source or a flooder and You get rid also of the floor and ceiling reflections (in case of a flooder the ceiling reflection can be delayed as much as 9-10 ms, depending on room and ear height)

 

[graaf]

Graaf, maybe you could do the honours of opening one?

actually, there is one:
http://www.diyaudio.com/forums/multi-way/121385-loudspeakers-room-system.html

What do You think? Any suggestions? Ideas? Your own unusual setups?

best,
graaf

 

[a_tewinkel]

actually, there is one:
http://www.diyaudio.com/forums/multi-way/121385-loudspeakers-room-system.html

Thanks! Seems a lengthy one

 

[graaf]

Hello Graaf

Looking at that diagram I couldn't help but look at those speakers as rears in an HT set-up. A spacious and diffuse soundfield with poor localization.

Rob

well, then it seems that You clearly can't read/understand that diagram

try to google for Beveridge "best imaging" and so on to find out about "spacious and diffuse soundfield with poor localization"

 

[graaf]

Anyway, the topic was conventional stereo, so let's stick to that. These other set-ups do sound interesting enough for their own thread, I think. Graaf, maybe you could do the honours of opening one?

You asked "What is the ideal directivity pattern for stereo speakers?". This bipol is a stereo speaker. One of the biggest challanges with it is its directivity pattern.

I am happy to see that I am not the only one who have misunderstood the original topic of this thread