I don't know the definition of "controlled" directivity but I would debate that constant directivity is what's most important. CBTs have a constant directivity to large degree horizontally and vertically.
I'm not sure I would say that about a speaker that is beaming.
Can't be because it does not say anything about dispersion width, which is finally responsible for the degree of room/speaker interaction.
I am not sure but, maybe revisit terminology.
All reflections are "out of phase", so why would one regard front wall reflections any differently in that regard? And "comb filtering" is really not an issue if spacing from the wall is sufficient and the wall is even modestly diffusive.
What I find more interesting, though, is that the "RFZ" (as indicated in your charts) produces a gap in the sound field at much the same delay that close miking does . . . in effect it exacerbates the same perspective-distorting effect. It can produce a more "on-stage" like sound (although the "direction" cues are all wrong) since direct sound predominates, and this may be tempting in the control room, but it does not reproduce the sound as heard in the hall.
It's not so much that "RFZ" rooms sound "bad" (they actually sound quite good for some kinds of critical listening) as it is that they do not sound "natural", or even "real", with most recordings. And you can always, of course, get that same distorted perspective with dipoles (if you want it) simply by sitting too close . . . then the "direct sound" dominates just as it does in a "RFZ" room from further back, and you hear all the perceptual artifacts of microphone placement.
All of which is OK if that's what you want.
Controlled directivity seems to indicate limited dispersion.
But like mentioned earlier, we cannot only look at that. We need to see if the total response is uniform as well.
A speaker that is broad in some areas and narrow at others will lead to coloration. So though you may end up will less reflections and room interaction at some frequencies, it will also give a distorted and altered response. Is that really better?
Many speakers that are promoted as "controlled" directivity are anything but "constant" over their full bandwidth . . . typically going from omni at low frequencies to some sort of "controlled" beaming higher up. Since it's called "controlled" we just have to accept that the designer's intent was not "constant".
Designers of omni and dipole speakers tend to design for "constant" directivity over the speaker's full range . . . and accomplishing that is what "controlled" means to them. I tend to regard any loudspeaker that exhibits "baffle step" as being "uncontrolled", but that just says what my perspective is
.Debating about terminlogoy, again, is just a sideshow.
The important questions - which are still unanswered - are, "How do direct sound, first reflections and late reflections contribute to perceived timbre?" and "How does the structure of first reflection patterns influence spatial properties?". Currently there's just a "yes, it's important" to both questions and a lot of handwaving. Nothing substantial.
The important questions - which are still unanswered - are, "How do direct sound, first reflections and late reflections contribute to perceived timbre?" and "How does the structure of first reflection patterns influence spatial properties?". Currently there's just a "yes, it's important" to both questions and a lot of handwaving. Nothing substantial.
High gain reflections, whether they arrive early or late, have a negative effect on timbre. Clarity, intelligibility, tonality and localization suffer. This is well known stuff.
Dipoles have polar lobing and comb filtering from the front wall. It's not a speaker one would choose if accuracy is the goal IMO.
A side show for you. But how can anyone discuss speakers and what they do or should do at all, if the terminology is used in a nearly scary way...?
Yes , that is why distance from front wall and baffle wings are very important , done correctly space and ambiance in the recording is reproduced with more accuracy than monopole and with far less dynamic compression ...
It's diffucult to discuss against any who are saying they prefer the backwave from the frontwall from dipoles. The idea that it get's you closer to the recording by doing it is however wrong IMO.
You can never get closer to the real by adding comb filter and reflections from the room.
I don understand that thought though. You feel you miss speaciousness and natural ambience from the mix, and want to add this. The problem is that you also end up partially wrecking areas lik clarity, intelligibility, loacalization and tonality.
Personally I prefer a combination of correct and sharp image with a diffusive backwall with it's enlargement and envelopment. Best of two worlds IMO. And it's not intruding on the recorded signal if the diffusion arrives late enough.
It's also well know that reflections have a beneficial effect on speech
Sorry but we don't have a good understanding of spatial reproduction.
Its because we hear sound naturally from all directions , reflected and direct. Monopoles reproduce sound unnaturally and work at their best when used in the nearfield ..
Monopoles also produce reflected and direct sound. That's really not the point. The problem is our understanding of sound reproduction which is highly limited.
I thought we're talking about music.It's also well know that reflections have a beneficial effect on speech
Sorry but we don't have a good understanding of spatial reproduction.
Sure we have a good understanding of spatial reproduction. That's for instance what Toole advocates. But he also understands what the drawbacks are. See below.
3D sound have by the way been done a long time ago with in ear recording mics. Never experienced it myself, but those who did said you could pin point where someone sneezed in the audience. With playback it required surround speakers, but no processing. Diffcult to see however why we would need it for music playback since the sound live is in front of you anyway. But it can be done and was conducted way before ambiophonics.
AES E-Library In-the-Ear Recording and Pinna Acoustic Response Playback
Monopoles reproduce unnaturally, most of their reflected sound is from side walls and a well delayed back wall reflection. This is not how we hear or percieve sound naturally.
Dipoles/bipoles are closer to how we hear direct and reflected sound , this is why its not unusual to see ambiance drivers mounted on rear of good monopole designs ..
Dipoles/bipoles are closer to how we hear direct and reflected sound , this is why its not unusual to see ambiance drivers mounted on rear of good monopole designs ..
How it workson a physical level has been studied up into small detail. It's importance for the spatial impression depends on "from what direction does it come", "how loud it is", "how late is it" and "what is it's spectral content". Hasn't this been researched by people from Blauert to Zwinger? And if you've got all that right, your brain stubbornly insists that the next note from the flute has to come from the same direction in space as the previous one.
There is nothing more than that. It doesn't get more substantial.
And of course there is simply no single answer and no "best" recipe that could suite all locations and all tastes.
here you go.. the dark, dark, dipole legend is back!
Have you ever calculate the time and level of reflections in a room, and compared them to this?
An externally hosted image should be here but it was not working when we last tested it.
Those are indeed interesting questions . . . but they are far short of "The important questions" . . . addressing as they do (at least in the loudspeaker context) only a small portion of the reproduction chain. How and where the sound is captured (microphones and microphone placement) still dominates and determines what we have to work with in the re-creation of a plausable soundscape for the listener.
A great deal of information is lost in the recording and delivery process, and substantial "gaps" have to be filled in at the reproduction end to produce a coherent and convincing, albeit somewhat inaccurate, representation of the original. Listening room reflections will unavoidably be a part of the final synthesis, so our choices are to learn to ignore them, or to successfully integrate them into the presented sound image in a way that preserves believability and produces a convincing "auditory scene" that at least somewhat resembles the original. And it all has to work with existing recordings and in a "practical" sort of way (unobtrusively and at multiple listening positions in the room).