I admit the flat freq response has iconic value thus far. But that will change in the future. And it will release other changes too.
- Elias
Well, at least you'll want the direct sound to be flat, right? Then the speaker should be CD up to at least the angle at which a listener will be positioned relative to the speaker while listening.
Let's recapitulate for a second - so far the only criterion we (most of us) seem to agree on, is:
- Flat direct sound.
With respect to directivity pattern, it seems to be whatever suits you, as long as it is somewhat smooth.
graaf, don't get all excited! 
I measured the room, but don't remember now. It was wider than shown in you squeezed pics, that's for sure! None of the speakers playing were close to the wall. 8 feet, 10 feet? I don't remember.
And that's why I mentioned it. I agree with Geddes that small rooms won't do this. That was part of my point. I've only heard omnis do well far from the walls. See also here:
Capitol Audiofest 2010 | Hifi Zine The MBL speakers near the top.
But when they are far from the walls (not typical for domestic use) they can image well, IMO. Maybe they have a very even polar response, at least in the vertical plain. Putting them close to the walls does not work well. Thus the need for a more narrow pattern.
I measured the room, but don't remember now. It was wider than shown in you squeezed pics, that's for sure! None of the speakers playing were close to the wall. 8 feet, 10 feet? I don't remember.And that's why I mentioned it. I agree with Geddes that small rooms won't do this. That was part of my point. I've only heard omnis do well far from the walls. See also here:
Capitol Audiofest 2010 | Hifi Zine The MBL speakers near the top.
But when they are far from the walls (not typical for domestic use) they can image well, IMO. Maybe they have a very even polar response, at least in the vertical plain. Putting them close to the walls does not work well. Thus the need for a more narrow pattern.
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yes, I can estimate it perfectly
BUT can You do the math?
because we are talking about pushing the delays of side wall reflections beyond 10 ms
how do You want to do that with room width of about 6-7 m?
graaf, don't get all excited!
well as our Dear Colleague erjee has rightly noted above "Anyone ... would be perfectly able to estimate the width of this room to be 6 to 7 meters" that is 23 feet maximum - so You are saying that the stereo base was just between 3 to 7 feet?
Not so fast ! You run from assumption to agreement
To begin, you need to define frequency response ! What time window, what bandwidth etc. for it to have any relevance.
I maintain that the importance of the freq response of the direct sound is not proved. All this from my stereolithic experiments.
- Elias
Excuse me for saying this, but there will always be people who have different opinions. Graaf and you hold believes that are very different from general consensus. You may or may not be right and maybe the future of loudspeaker design will prove the rest of us wrong, but for now I'm looking for the common denominator. As far as I can tell we've at least got flat direct sound.
er... psychoacoustics without facts? why?
no fights here, but aren't facts interesting?
but were they spaced farther enough to meet gedlee's requirements?
aren't You interested?
Not so fast ! You run from assumption to agreement
To begin, you need to define frequency response ! What time window, what bandwidth etc. for it to have any relevance.
I maintain that the importance of the freq response of the direct sound is not proved. All this from my stereolithic experiments.
- Elias
of course, Moulton says the same:
the so called direct response is a measurement artifact that is never perceived as such in reality, never
@Keyser
this is psychoacoustics
common denominator? er... You mean convictions...? excuse me, I thought You were looking for truth, for psychoacoustics
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Sorry to be repetitive, but I think sometimes a little repetition can be helpful.
The constant directivity cornerhorn concept blends the benefits of omnidirectional radiation with the benefits of a narrower pattern. Omnidirectional (if constant) provides a uniform 360° radiation. The corner confines this to a 90° slice. Used with 90° horns at higher frequency, one can achieve constant directivity without reflections.
As I see it, the only real problem happens when an omnidirectional (or wide pattern speaker) is placed closer than a few feet from a boundary. If you can get it further away, the self-interference from reflections happens low enough you can deal with it using multiple subs. But another solution presents itself, which is to put the speaker right on the boundary. That's what the constant directivity cornerhorn approach is all about. When in a small room - smaller than a ballroom - you really can't get the speakers far enough away from the walls to be optimal. So in rooms like that, I like the constant directivity cornerhorn approach, and where that's not possible, flanking subs help smooth the lower midrange ripple.
In really large rooms, the sound is much better, sort of like outdoors. It's much easier to get things right in a large room. But in a small room, it's hard to space the speakers far enough away from the walls to sound good. That's why I think it's so important to work on solutions for the lower midrange, because they're often the hardest part. Even in fairly large rooms in house, most times the ceiling isn't that high, so often times the lower midrange is adversely affected. That's where some blending from a couple vertical sources help, either from blending a low-running midrange and woofer, a helper woofer or flanking subs.
I've gotten confused by some of the comments regarding "you are there" vs. "they are here", so I'll say what I think is going on with it, and hope to learn something from someone's comments.
I feel "I am there" when I have minimal playback listening room reflections, the inter-aural cancellator is engaged, and there is reverb embedded in the recording. Best case is with Binaural recordings, but many non binaural are pretty "transporting" too. Synthetic image synthesis has gotten pretty impressive. The further you go away from that, the more it becomes more like "they are here" to my way of thinking, not that that is necessarily so bad. I suspect that only a full nerd like me would appreciate the elevated clarity of imaging at the sweet spot. Only a fool like me wants to completely escape this screwed up world, and step through the looking glass altogether. For most others I'd expect them to be happier with speakers that have 150 degrees horizontal consistent over most frequencies radiation; so there's a good frequency response out of both speakers at most places in the room. Although the DBX Soundfield speaker was exceedingly enjoyable to my ears (4 ft. away from any walls), it did scramble most of the real imaging info in the recording, and replace it with listening room effects. Controlled directivity on the vertical axis makes real good sense in either case, to avoid ceilling and floor bounce, which typically causes -12dB cancellation notches all across the spectrum starting around 500HZ (based on my 1st hand measurement experience).
My appreciation of vertical line arrays keeps growing. Up to 6-7kHZ that might work best with typical listening room acoustics. It inherently has limited vertical dispersion so minimal floor and ceiling bounce cancellations. It works well with room reflections in general because any cancellations are more likely to be filled in (in more locations in the room) by so many other physically displaced sound sources putting out the same thing at the same time. Especially in the lower mid and bass freqs., where the cancellations are typically further apart and only a few effective reflections exist with one or two drivers, so little or no fill-in down there. Above 6-7kHZ, I still think very wide dispersion will sound best, part because most speakers get real narrow in this range (so off axis and power response get bad), and because we don't use that freq range for imaging clarity in the same way as the ranges below it.
I feel "I am there" when I have minimal playback listening room reflections, the inter-aural cancellator is engaged, and there is reverb embedded in the recording. Best case is with Binaural recordings, but many non binaural are pretty "transporting" too. Synthetic image synthesis has gotten pretty impressive. The further you go away from that, the more it becomes more like "they are here" to my way of thinking, not that that is necessarily so bad. I suspect that only a full nerd like me would appreciate the elevated clarity of imaging at the sweet spot. Only a fool like me wants to completely escape this screwed up world, and step through the looking glass altogether. For most others I'd expect them to be happier with speakers that have 150 degrees horizontal consistent over most frequencies radiation; so there's a good frequency response out of both speakers at most places in the room. Although the DBX Soundfield speaker was exceedingly enjoyable to my ears (4 ft. away from any walls), it did scramble most of the real imaging info in the recording, and replace it with listening room effects. Controlled directivity on the vertical axis makes real good sense in either case, to avoid ceilling and floor bounce, which typically causes -12dB cancellation notches all across the spectrum starting around 500HZ (based on my 1st hand measurement experience).
My appreciation of vertical line arrays keeps growing. Up to 6-7kHZ that might work best with typical listening room acoustics. It inherently has limited vertical dispersion so minimal floor and ceiling bounce cancellations. It works well with room reflections in general because any cancellations are more likely to be filled in (in more locations in the room) by so many other physically displaced sound sources putting out the same thing at the same time. Especially in the lower mid and bass freqs., where the cancellations are typically further apart and only a few effective reflections exist with one or two drivers, so little or no fill-in down there. Above 6-7kHZ, I still think very wide dispersion will sound best, part because most speakers get real narrow in this range (so off axis and power response get bad), and because we don't use that freq range for imaging clarity in the same way as the ranges below it.
I suspect that the DBX Soundfield may have failed because of the requirement of being at least 3 ft. from any walls. Like the corner horns, not a lot of real world living rooms are able to accommodate these requirements. Wife acceptance factor too. The DBX I heard back in the 1980's sounded very good to me.
I agree with the first part completely, but narrowing dispersion at lower freqs may not be optimal. Unless you have no listening room reflections at all in the lower mid and bass region, you will have substantial cancellations. A typical living room will only have a few significant reflections in this frequency region because of the size of the wavelength involved. The more reflections (or flankers or other additional sound sources), the more any given cancellation will be filled in, at the listeners ear, due to the physical displacement putting additional cancellations at different frequencies.High directivity at which frequency range ?
For me, high directivity tweeter do not (phantom) image at all, since all I hear is the two tweeters at the exact speaker locations. This is not imaging.
By making the tweeter very wide directivity, maybe even close to omni, it will not introduce contradicting cues but will faint away in the backround to allow lower frequencies to enable the imaging.
And because of this, the speaker at lower frequency ranges than treble must have high directivity to allow less room influence.
As a conclusion:
Ideal directivity pattern for stereo speaker is: high directivity at bass and midrange, and low directivity at the treble.
It should be obvious, is it not?
- Elias
Flat direct sound is a good thing to design for as a starting point, but is typically too bright and squeaky in the real world IMO (Another diyaudio forum beat this to death about two months ago). You then want to adjust tone controls (preferebly 4 section baxadall variable slope IMO) to accommodate the acoustics of the room, the idiosyncracies of the recording process, and possibly a little reverse fletcher-munson if the preferred level is lower than real life. And the directivity pattern should take into account any room acoustics problems that can't be fixed any other way. I would agree that any abrupt changes in directivity pattern would likely be bad at most frequencies, the one possible exception being above 6-7kHZ where I think wider is likely to always be better, regardless of what's happening just below that.
Wayne, your corner horn approach does work and my impression was also that it was more like outdoors (few close reflections), the lack of reflections does I think (all things equal) make the system more able to convey the feel of being outside or in a small bathroom depending on the recording.
When the listening room is playing a strong part, you have lost some of that ability by adding room sound which isn’t part of the original space, an effect you can’t turn off..
Some of the Synergy horns we make are used on boundaries, the same properties that allow two to array without an audible seam or comb filtering, allow one to work on a boundary which acts like an acoustic mirror image without comb filtering etc.
If the horn wall angle and wall angle are equal and the step less than about ¼ wavelength where you loose pattern control, the floor / wall / ceiling boundary becomes a near perfect mirror as the horn losses pattern control as the frequency falls..
With the full range radiating from one horn body and with the size of the aperture, there amount of energy radiated even 90 degrees off axis is very small (-20dB or more over a broad band) so one doesn’t need to be very concerned with the rear wall.
I had a very narrow listening room about 7 years ago which was always a problem even with electrostats, worse with the point sources I had made. Speakers that imaged beautifully outdoors were destroyed by my room. I suggested a couple times here people try listening outside to do a reality check on how important the wall reflections are, that becomes clear when you take them away.
I had the set of Synergy prototypes I had worked on and moved the stuff needed to have them at ear height at the side walls. These speakers were only 50 X 50 degrees and were about 4 feet from the back wall.
That spot being set by where they were aimed when against the walls vs the kitty corner positions on the listening couch.
The effect was literally that the image was at or past the wall and not where the speaker was some inches away. It did a great job with the “sense of space of the recording” and if my current room would allow it, I would set it up that way now.
Our hearing is optimized to help us hunt and protect us from harm.
If you examine the “equal loudness curves”, it is clear where the engineering department felt was most important for us to hear.
When the bear charges you in the dark, your ability to point the spear or .600 H&H in the right direction before you can see him, does not include significant reflected sound from your listening room, nor should the recording your listening to .
Best,
Tom Danley
When the listening room is playing a strong part, you have lost some of that ability by adding room sound which isn’t part of the original space, an effect you can’t turn off..
Some of the Synergy horns we make are used on boundaries, the same properties that allow two to array without an audible seam or comb filtering, allow one to work on a boundary which acts like an acoustic mirror image without comb filtering etc.
If the horn wall angle and wall angle are equal and the step less than about ¼ wavelength where you loose pattern control, the floor / wall / ceiling boundary becomes a near perfect mirror as the horn losses pattern control as the frequency falls..
With the full range radiating from one horn body and with the size of the aperture, there amount of energy radiated even 90 degrees off axis is very small (-20dB or more over a broad band) so one doesn’t need to be very concerned with the rear wall.
I had a very narrow listening room about 7 years ago which was always a problem even with electrostats, worse with the point sources I had made. Speakers that imaged beautifully outdoors were destroyed by my room. I suggested a couple times here people try listening outside to do a reality check on how important the wall reflections are, that becomes clear when you take them away.
I had the set of Synergy prototypes I had worked on and moved the stuff needed to have them at ear height at the side walls. These speakers were only 50 X 50 degrees and were about 4 feet from the back wall.
That spot being set by where they were aimed when against the walls vs the kitty corner positions on the listening couch.
The effect was literally that the image was at or past the wall and not where the speaker was some inches away. It did a great job with the “sense of space of the recording” and if my current room would allow it, I would set it up that way now.
Our hearing is optimized to help us hunt and protect us from harm.
If you examine the “equal loudness curves”, it is clear where the engineering department felt was most important for us to hear.
When the bear charges you in the dark, your ability to point the spear or .600 H&H in the right direction before you can see him, does not include significant reflected sound from your listening room, nor should the recording your listening to .
Best,
Tom Danley
This quote is not exactly correct (nor is your interpretation of it). For slow moving symphonic music it is generally considered that sound within the first 50ms increases perceived level without degrading musical clarity. For speech the window must be dropped to 30 ms otherwise inteligibility suffers. That is, increasing the direct sound and early reflections before 30 ms will increase speech level without degrading inteligibility. If we are talking about precedence effect and masking (whereby later sounds will be hidden by preceeding sounds but can add to their level) most studies show integration times of about 20msec with gradually falling levels after that.
Now if we are talking about perceived frequency responses of loudspeakers, Salmi, Kates, Queen, Bech and others show that the ear effectively uses a variable time window, short at high frequencies and long at low frequencies. The time window is so short at high frequencies to only let in the direct sound and some nearby cabinet reflections. By the midrange the nearest boundary bounces, such as the floor bounce, will be perceived wile later bounces are excluded. At low frequencies the window is fairly long and most of the room response is perceived.
At least for upper frequencies, the direct sound is very much a reality.
David S.
A gammatone wavelet plot is a good starting point on this ! Recommended
Direct sound is an option ! It can be enabled if desired.
Interesting perception occurs if direct sound is blocked (absorbed) in stereolithic projection. It maybe safe to assume that direct sound is not necessary but also that it's presense may not totally destroy the sound other than at high freqs (yes, those perceived tweeters again).
- Elias
Listen in an anechoic chamber.Just a philosophy: How to record a singer in an anechoic chamber to achieve "you are there" ??
It must be possible, since by now we know that stereo is capable of anything
- Elias
Dan
But I'm not here for "business" but to build something for myself, a DIY you see. Am I in the right forum ?
Are you here for "business" ?
- Elias
Most of us have use a readily available format--IOW we can't avoid it if we want the music we love. Some of us also have friend and family that we care about. Don't want to exclude them.
Dan
I think that a toed-in controlled-pattern dipolar or bipolar speaker can, given sufficient distance to the nearby walls, achieve a < 10 ms reflection density very similar to that of a corresponding monopole, but with nearly double the > 10 ms reflection density once that rear-radiated energy begins to arrive. Not all of it will show up as lateral reflections, but much of it will. (Of course this sort of geometry takes up a lot of real estate in the listening room so it is not always practical, but in some rooms it is).
Does this sound plausible to you?
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