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Old 20th February 2011, 09:35 PM   #41
Elias is offline Elias  Finland
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Hello,

If image is locked to the tweeter, possible causes can be:
* too high direct to reflection ratio of the tweeter
* too high level of treble compared to midrange


I understand your center tweeter operates above 7kHz.

Try eliminating (reducing) the direct sound. Why there should be a direct sound above 7kHz at all? Too much of direct sound at this high freqs will not be a benefit in a stereo system because of pinna.

Maybe try ceiling firing tweeter to maintain overall tonal balance and get reduction of direct sound.

Or simply try shelving low pass filter for the tweeter to lower the level, but I think modifying direct to reflection ratio should give better results.

- Elias


Quote:
Originally Posted by CLS View Post
Have been listening more and more, I ran into a dilemma

Close positioned or now mono tweeter has a strong point of spaciousness, especially in the depth. Images seem always appear behind the speakers. The presentation is more of 'you are there', instead of 'they are here' -- a 'tradition' of high efficiency horn system (what I had before).

Images in the soundstage are well defined, individual instruments or vocals have their right positions or even shapes and sizes. And I got a feeling that sources seem to have 'haloes' or they're slightly glowing -- there's soft and tender 'atmasphere' around each of them and among them. In addition, such wonder can be maintained in a very large listening area. In extreme off center listening positions -- at the side of the speaker, imaging collapses (of course) while tonal balance stay very stable.

I'm not sure how the images can be projected and focused beyond the tweeters (no special signal process here, only ordinary 1st order filters). Those sounds coming with very high frequecy overtones (attacks of percussions, strings...) are indeed formed far outside of the tweeters when call for, but with a condition...

---- the sound must have its own 'body' in relatively lower frequencies (the fundamentals).

When the sound is purely HF, then comes the problem. Jazz piano trio is one of my favorite forms of music. The drum set is often arranged at one side of the stage (-- almost always on the right in one of my favorit trio, Keith Jarret Trio). I can 'see' the piano, bass, drums at thier correct positions, but when the cymbals are hit, almost always, they appear around the center -- detached from the whole drum set.

Sometimes, a large ride cymbal is softly hit (or hit by a stick with felt ball), there's larger proportion of lower fundamental. This note would come back to its correct position with the whole drum set. Such effect is annoying, be it CD or DVD.

Sigh~ What a pity !

By the way, I made the supertweeter in vertical face to face 'quasi-omni'. And I've tried arranging the midtweeter horns to side or up firing (like the ears of Shrek). Shrek type radiation makes a very spacious sound field, but is not helping the 'positioning' problem of the HF images. And it's too much 'atmosphere' with too less 'body'.

I've also tried "R-L" and "R-L" signal on the midtweeters by series connecting. The sound seems clearer, but could not solve that problem, either.

So, it's not perfect yet. The journey goes on.
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Old 21st February 2011, 02:15 AM   #42
CLS is offline CLS  Taiwan
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Quote:
Originally Posted by CLS View Post
...

I've also tried "R-L" and "R-L" signal on the midtweeters by series connecting.

....
Oh, I meant 'R-L' and 'L-R'. (Edit time is over... ) You guys must know it.

And thanks a lot for replies.

--------------------

Radugazon,

You've mentioned those test tracks to me earlier. I've downloaded them already, and am now finding a way to put them on to the player... (I'm old fashion my PC is not connected to the audio system .... )

And as mentioned, except for cymbals, (or triangle... ) etc., all other 'normal' instruments are all fine (or excellent) in imaging. Their fundamentals (tend to be ITD) indeed do the job brilliantly.

Those 'pure HF' instruments I brought up have relatively very less proportion of lower frequency fundamental. They give mostly the leading edge of attack. ( No? ) Hmmm.... so that leads to ....


Elias,

Thanks a lot for your suggestions. I've been reading a lot of your posts, very educational and informative. You must know a lot of things I don't know.

In this case, I would tend to agree more on the 1st point (too high direct to reflection ratio of the tweeter), but with uncertainty or confusion.

(Too high level of treble is never an issue on my system, I hate overly bright balance. I just don't let that happen.)

My place is very reflective to start with - concret walls, tile floor, calcium silicate board (and low) ceiling. Absorbing material is almost non-existent.

I've tried 3 types of (super)tweeter setups up to now:

1) Ordinary type, direct pointing at me - the highest D/R ratio, indeed the worst. I took them apart in a short time.

2) 2 tweeters face to face vertically, a fiddled radial type 'quasi-omni'. It gives very uniform HF at the horizontal plane.

3) 45-degree uptilted mono tweeter, Stereolith type. It's more or less off-axis all the time (for almost all possible listening positions), and projecting the most ceiling reflection.


The second type has very little vertical dispersion, its horizontal refections arrive quite long after the direct sound - the difference in path length is > 5m (>14~15ms).

In addition, although the boudaries are all very reflective, the HF sound (especially > 7~8kHz) is intrinsically very 'lossy' along its propogating process. Let alone the multiple reflections. Long delay and high loss, I feel those reflections don't contribute much to the overall 'sound'. It's the 'atmosphere' instead.

Nevertheless, it's the most natural sounding setup. I like it the most, except one drawback - it's oh so quiet, needs too much EQ boost (thus other issues...) Again, I don't like bright sounding. It's the face to face configuration kills the efficiency. I boost it conservatively, and it's measured > 8dB down compared to the mid band. I don't feel comfortable boosting it more....

The 3rd (Stereolith) type gives strong ceiling (early) reflections. By roughly calculation, the path length difference is about 1m or slightly more, which leads to a (critical) 2~3mS of delay. In such HF, TBH, I can't detect any 'smear' or something like that by ears.

The effect of spaciousness is the most obvious in the group. Somehow, sometimes, I feel it's trying too hard. Fascinating, yes, but not always realistic.

-----------

Well, OK, all above are only for supertweeter only (>7~8kHz). I'm more than happy to make this portion mono as I like very much how it sounds to me.

But under that, down to about 1~2kHz, under the principle of OSD, I found the image positioning problem can't be overlooked in my system. Up or side firing setup for this range doesn't solve the problem, even the direct/reflect ratio is lower. I can't get that wonder in supertweeter in this range. Hmmm... isn't this range still in ILD 'territory'? (Maybe this portion of sound is bound up with the 'body' of the instrument much more than the higher range? hehe...)

Or maybe it's because the dispersion patterns are far from ideal (I can't make them omni for the time being.)

I've tried moving the midtweeter (2~8kHz) back to their normal stereo positions. This solved the positioning problem of those HF instruments, but lost a lot of OSD magic. (sure, it's not OSD anymore).

Tradeoffs and dilemmas, as always.
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Old 23rd February 2011, 12:46 AM   #43
CLS is offline CLS  Taiwan
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Default A Compromise

I tried relocating the midtweeters to the (inner) sides of big mid horns. See attached picture. (the boxed mini monitors beside TV are not in the main system, they are for TV only)

And the supertweeters are now 2 units (in stereo connection), spaced by 35cm or so, firing almost vertically up with a little angle toward the front. Large proportion of indirect sound in this range is indeed very good. I like it a lot and can't go back. (Thank you, Elias.)

I spent some time trying the toe-in angles and found a compromise among image focucing/positioning, spaciousness, listening area, overall in room response... etc. Now it's kind of an all-rounder, or I should say a compromise.

You may see in the pic that the midtweeters are toed in a lot. I suppose the objects nearby might probably cause some problems. I'll try some absorbing materials later. Or bringing the midtweeter higher. Or both...

It's alright for now. To be continued for sure....
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Old 24th March 2011, 06:23 AM   #44
ScottG is offline ScottG  United States
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Quote:
Originally Posted by CLS View Post
I tried relocating the midtweeters to the (inner) sides of big mid horns. See attached picture. (the boxed mini monitors beside TV are not in the main system, they are for TV only)

And the supertweeters are now 2 units (in stereo connection), spaced by 35cm or so, firing almost vertically up with a little angle toward the front. Large proportion of indirect sound in this range is indeed very good. I like it a lot and can't go back. (Thank you, Elias.)

I spent some time trying the toe-in angles and found a compromise among image focucing/positioning, spaciousness, listening area, overall in room response... etc. Now it's kind of an all-rounder, or I should say a compromise.

You may see in the pic that the midtweeters are toed in a lot. I suppose the objects nearby might probably cause some problems. I'll try some absorbing materials later. Or bringing the midtweeter higher. Or both...

It's alright for now. To be continued for sure....


Have you tried it with the mid-tweeters very close together but "toed-out"?
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Old 24th March 2011, 06:52 AM   #45
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Toe out : do you think of something like this ?
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Old 24th March 2011, 05:46 PM   #46
ScottG is offline ScottG  United States
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Quote:
Originally Posted by Radugazon View Post
Toe out : do you think of something like this ?
YES.. though for his waveguides that is too much toe-out. (..and his won't have directionality due to dipole cancellation.)

BTW, very nice work Radugazon! It's far closer to a perfect radiation loudspeaker system then just about any I've seen (..and I've never said that before).

Have you been convolving your media to binaural?
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Old 24th March 2011, 07:04 PM   #47
graaf is offline graaf  Poland
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Quote:
Originally Posted by ScottG View Post
Have you been convolving your media to binaural?
uhm uhm... tricky question
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Last edited by graaf; 24th March 2011 at 07:10 PM.
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Old 24th March 2011, 08:46 PM   #48
ScottG is offline ScottG  United States
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Quote:
Originally Posted by graaf View Post
uhm uhm... tricky question
..it is after all the final ingredient to unlocking a correct stereo perspective with this setup.
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Old 25th March 2011, 12:03 AM   #49
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Good questions are always tricky...

Before answering, I have to say that here the system is set up in a side firing configuration, but of course, except this, it's not a stereolith. It's composed of linear quadrupoles with their usual positive and negative properties. The subs remain dipoles and are very excentered.

more details if needed :

Quote:
This has the potentiality of creating a huge spaciousness, but at the price of a serious imaging. As I am a pragmatic guy, I use some diffusers to correct this (see the picture...).
OMG, they are not quadratic...It's randomly sized bamboos. Following the diameter, I suppose they must work over 6000 Hz and reflect a part of the spectrum on 180°.
They finally narrow the image too a realistic size on a little formation, but keep it wide on a big forte. In any case it preserves the repartition of the sources. But you know, all this is subjective stuff.

Then, their orientation on the floor horizontal plane has little effect, but the vertical orientation is the key:

oblique inside, it widens, oblique outside it narrows...

An other way of controlling the "center channel" is precisely to toe out the HF group....

I have diffusers like this close to the ceiling too, all weird, but it works.
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Old 25th March 2011, 01:15 AM   #50
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Now, pre-convolving all my records for satisfying an always temporary setup is not a good plan. I have some samples I did months ago, they are now unlistenable, all like with added reverb and echoes.

I would like better a generalist system that "transforms" (bye bye the concept that you know ) an ordinary multi tracks record in something convolved-like, without inducing trouble in the naturally or artificially binauralized ones.

It's not a joke but don't take my rhetoric at 100%, the subject can't be contained in two lines.

Here the subjective approach has a good helper : the phase analysis, I mean the stereo phase between each channel, not the phase between the drivers of an isolated speaker.

On the joined pic, a binaural record of a 1000 Hz signal with 180° rotation of the field taken from the listening spot (5 meters).

Normally, when it's like this, the system images rather more accurately than ultra wide. Work are still in progress, I try to conciliate both aesthetics. Many factors have some importance, as the foam phase plugs that change a lot of things (thx Mr Geddes).

Last word: on a rotating phase test, a classical basic system produces a Right/Left alternance, but in a system like this one, or like the stereolith, it's easy to perceive (or imagine...image/imagination) a rotating source around the system.

3D ? Definitively yes.
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