What I said, in support of Dan's suggestion of the potential significance of off-axis response anomalies derivative of woofer breakup.
Dipole creates early ipsilateral reflections off the FRONT wall but not the side. Linkwitz says it's important to have these to generate spaciousness, provided the speaker is far enough from that wall to delay them at least 6 ms, 6.78 feet additional path length, by my calc. I believe we'd say "Not long enough," kill them, and rely upon the further-delayed low-IACC contralateral reflection to generate the requisite cues.... 🙂
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There have been much research on how to trick the mind into perceiving spaciousness, so there are many ways of doing it. All these are ignorant of using recording techniques to recreate the spaciousness in the original recording because the majority of recordings probably were not recorded in places that give sense spaciousness. So people just have to tune their rooms to whatever speakers they purchase or purchase the best speakers for their room.
In the real world, you will never get the same spectrum of reflections as indicated by Mr. Linkwitz, although, I must confess I originally beleived such to be a reasonable assumption initially. However, if there is such dispersion of reflection, it may help improve stage image stability when the room mode strength is kept below the levels of first reflection. So now we have the issue of room modes stength and first reflection strength.
In the real world, you will never get the same spectrum of reflections as indicated by Mr. Linkwitz, although, I must confess I originally beleived such to be a reasonable assumption initially. However, if there is such dispersion of reflection, it may help improve stage image stability when the room mode strength is kept below the levels of first reflection. So now we have the issue of room modes stength and first reflection strength.
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Did markus76 even read post #289? These standards have been around longer than any of us have been alive concerning the measurement of beamwidth and directivity. Frequencies are arbitrary but there are a lot of different frequencies showing the constant power curves with this waveguide speaker. This is the gist of directivity measurement. Many frequencies shown and many polar plots. Yes I agree with doug20 about the link to the speaker, this waveguide thing seems......
27TBCD/GB-DXT Novel driver(plot below)...maybe. Was not available 10 years ago. Please notice how the on axis and 30 degrees off axis curves are very close together and the frequency responses is -10dB at 20kHz from its 3kHz value? This roll off is always the case with CD transducer because it must be so. One can have flat frequency response or constant directivity but not both without EQ in a wide band driver. Will check out this tweeter. wonder if SEAS ever got the voice coil falling off the dome problem fixed...humm.
My tweeter was custom made and is not unlike the SEAS in response. I do not get doug20 complaint. Forget my tweeter (developed with Forgings) and look at the CONSTANT DIRECTIVITY SEAS and then look at these post #262 of response of the waveguide. No way is that even relevant to constant directivity at the 40 degree response. What these curves are does not have a name as far as I know. To call them "constant directivity" is just wrong. Call it something else. Give it a name you like the sound of like "axial flatness" or just anything that is not already used and well defined, please.
Whatever "Earl" wrote appears more to be a different method of plotting the same old data than anything new. Combining data from many separate graphs into one color plot makes not one bit of difference in the raw data so, what is your point? Waveguides as shown in post #262 do not show constant directivity at the 40 degree line because that line is below the -3dB constant power boundary as defined for beamwidth calculations. If your desire is to redefine standards that have been around for a very long time well, then why bother with any standard and just make up (invent) whatever suits your fancy to prove whatever you dream up? My complaint is calling this constant directivity out to 80 degrees because it simply is not no matter how the data is plotted. If you toss away the standard then yes, it can be anything you wish. Of course with no standards and no defined differences communication is terminated. Is that the goal?
As for the sound experience of post #262 I have no comment of any kind.
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It's easily seen that the first contralateral reflection is coming from more on axis, ~45°, and is thus higher in amplitude despite the increased distance to the listener, and delayed by ~12ms per Toole Fig.8.5.
While reality may deviate from this idealized model, it offers an insightful (and measurable) conceptualization thereof.
DXT w/HF comp:
And as measured by others with and without comp:
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My complaint is that you right essays about nothing really. Domes are not CD unless they are mounted in waveguides.
Geddes is an expert on Constant Directivity, Harman (Toole, Olive, etc) are experts on Constant Direcitivity, Danley is an expert on Constant Directivity. You are none of those guys...
Its easy to hear the difference between domes and anything horn loaded. Once you hear speakers with real constant directivity then you will understand what Im talking about.
Are you not the guy that talked about dampening the back of the compression driver and sticking some wool in the throat of a horn? How can you not notice the meaurements of a horn (Ie constant directivity) if you did actually build a horn. Very confusing.
Anyways, this is all OT. IF you really want to figure this out start a new thread and complain about it. This really isnt a "What is Constant Directivity" thread. Its about measurements.
Remember no one else is complaining about it.
I am talking about live events when I refer to real world. Probably you have to listen to the lecture Mr. Linkwitz gave at AES to know what I'm talking about.It's easily seen that the first contralateral reflection is coming from more on axis, ~45°, and is thus higher in amplitude despite the increased distance to the listener, and delayed by ~12ms per Toole Fig.8.5.
While reality may deviate from this idealized model, it offers an insightful (and measurable) conceptualization thereof.
The UK one? I have heard it, and also the one he presented here locally a couple of weeks ago.
If you're saying that recordings delivered over speakers in a listening room cannot replicate the wavefield of a live performance in real space, well.... 🙄
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My point is that to have a well distributed response that corresponds with the power response has nothing to do with the way reflections occur in reality, but can contribute to sound image stability throughout the audio range. It is quite often that we can hear a specific instrument shift in location depending on which notes are played. With CD, and proper control of room resonances, this can be better controlled.
Guess it depends solely on how dipoles are placed. It's pretty easy to find the first reflection points with the help of a piece of paper and a protractor.
These "special" reflections caused by dipoles will certainly add spaciousness but the question is: Does the listening room need to provide single strong first reflections or should we allow the recording to "decide"?
How the reflection pattern should ideally look like is unfortunately open for discussion.
Best, Markus
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Linkwitz illustrates that the directivity of dipoles does not generate the primary ipsilateral from the sidewall when toed-in as shown.
The objective is to generate artificial spaciousness without being at the mercy of the listening room. If we rely upon the recording alone, it would be spare, as may be heard via headphones. Indeed, some seek this alternative with very narrow dispersion and room treatments in order to maximize pinpoint imaging at the expense of soundstage. By the CD thesis, however, the two don't have to be mutually exclusive, and a more satisfying balance may be achieved.
I believe it's clear that high-IACC early reflections (<10ms) are detrimental to both spectral and spatial quality, and that would be my argument for Linkwitz to either damp the front wall or abandon dipoles.
[Not gonna happen, I wouldn't guess, but he's just a mere 4ms away from that conclusion presently.... 😉 ]
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doug20, I never said anything about open domes having constant directivity, exactly the opposite as a matter of fact.
Been listening to constant directivity for a very long time because it has been around for a very long time.
http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/horns/HF Horns Multicellular Horns.pdf
Constant directivity is nothing new at all and no one here invented it. It is helpful to know some history and standards to more clearly understand directivity.
As for experts- let history decide that.
Thanks for the good graphs Zilchlab!
Been listening to constant directivity for a very long time because it has been around for a very long time.
http://www.altecpro.com/pdfs/vintage/SpeakerAndMics/horns/HF Horns Multicellular Horns.pdf
Constant directivity is nothing new at all and no one here invented it. It is helpful to know some history and standards to more clearly understand directivity.
As for experts- let history decide that.
Thanks for the good graphs Zilchlab!
You are welcome, of course.
I have DXTs, and have heard them in MarkK's build using them. All I can say is if diffraction is the source of all sonic evil, it is pleasurably bad, indeed, in this implementation:
The Seas ER18DXT ported two way
That's why I can't wait to build some low diffraction enclosures. I've had that same suspicion and mentioned it in another thread, but got no replies. We'll have to wait and see. It may well be partly a baffle issue.
Dan
I (and Toole as well) would contest this claim. Spaciousness requires lateral reflections. The frontal reflection will interfere with the imaging, especially at 6 ms. I find, and Floyd says this in his book as well, that killing the wall reflection behind the speakers is a major advantage to sound stage.
First, I would completely agree with this statement - HOWEVER, Floyd Toole would not. This is precisely where I disagree with Floyd and think that he is jumping to some conclusions that his data only weakly reinforce. And thats only if you use "preference" and not "accuracy" (as in "imaging") as the criteria. Floyd does not sort this out, his work all uses "preference" and "imaging" is not a real consideration. It's not big on his "importance" scale - its all about "spaciousness" and the feeling of "being there".
Re: spaciousness, Toole relies on studies indicating that, given the opportunity to do so, listeners will dial up the cues to generate spaciousness well in excess of anything that would occur in reality, even to the detriment of sonic quality, i.e., inaccurate in both respects. He seems to waffle on this one considerably, asserting that there is, however, clearly an optimum balance to be sought, and agreeing that constant directivity is the best means to achieve that purpose.
Indeed I DO sound better singing in the shower, but the sameness of Bose 901's artificial "enhancement," while initially pleasurable, wears mighty thin over time. 😉
Footnote: I think of 90° more as "moderate" dispersion than "narrow," as you characterize it, which for me is 60° and under, with "wide" beginning at 120°, and "very wide" anything 180° or above, 30° and below being "very narrow." From this perspective, Toole's position is less in conflict; he only recommends such wide dispersion for use in surrounds, is my reading....
Indeed I DO sound better singing in the shower, but the sameness of Bose 901's artificial "enhancement," while initially pleasurable, wears mighty thin over time. 😉
Footnote: I think of 90° more as "moderate" dispersion than "narrow," as you characterize it, which for me is 60° and under, with "wide" beginning at 120°, and "very wide" anything 180° or above, 30° and below being "very narrow." From this perspective, Toole's position is less in conflict; he only recommends such wide dispersion for use in surrounds, is my reading....
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The amplitude of the issue changes dramatically well beyond 45 degrees. Solving for 45 degrees won't solve for 78 degrees. Further off axis issues are clearly evident still. The one w/o the notch definitely sounds harsh and simultaneously nasally (ha ha) compared to the notched. I wouldn't have a good idea why if I didn't measure out so far. This may help you on your design. Time will tell. 😉
I'm looking for cheaper than the DE250 even though that driver is probably in my future. I'm totally happy with my current CD--no immediate need for anything. In fact, no set limit, just as cheap as possible, but no cheaper. The cheapest Eminence is too cheap--the wavefront doesn't load a WG well. After I get better at designing and building, I'll buy better drivers. The fact that I've finally built a speaker that I enjoy more than anything else I've heard tells me I'm getting somewhere, but my training is incomplete. It's possible to make a silk purse out of a sow's ear. To start with better stuff is just gravy. Oh, I can't find the QSC HPR15i. I get a subwoofer from Google. Any links?
Thanks,
Dan
The too strongly just means that you should have better support for your strong beliefs. At least that's how I see it, but I may require more proof than many. I get told that a lot at work.
I have no explanation for why an "expert" does not understand what is obvious. At least it is now.
I actually do buy drivers and measure them to 90 degrees. Thus the measurements posted.
I showed how 90 degree measurements lead to a better speaker more than once. I think you're just being argumentative. They'll matter less the lower you cross, but you'll end up with a tonal imbalance if you go too far.
I agree the money is often worth it and the data available from that driver looks promising. I wanted to buy it actually but didn't know if I'd had the mustard to make it work as this is my first CD design. Don't want to get divorced over my hobby. 😀 I would prefer better drivers, but no one learns to drive in a stock car--at least not where I'm from.
Dan
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Thanks Methman! I'm afraid of what the HPR152i may sound like d/t all the sharp angles. I've never heard though so it may well just be paranoia. For the price it wouldn't be too much to find out. Too bad I'd have to buy another CD for that. That equals much too much outlay for me as happy as I am now.
Thanks,
Dan
Thanks,
Dan
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