I take a strong exception to your position. If the DI doesn't matter (i.e. the power response) then that's like saying that the room doesn't add anything and that a speakers anechoic response is all that we hear. That's simply not the case.
For me DI is second only to direct sound FR and I suspect that the experts who created CEA-2034 would agree.
The room adds in the same sense as an enclosure or horn adds to the loudspeaker driver's output. The room becomes a part of the system when the loudspeaker is placed within it, but, in a purely argumentative sense you may consider yourself right.
When I read similar thoughts concerning "the room" I always think; but the room is also a somewhat random variable regardless of off axis character of the speaker. The largest part of it, "the room" is exaggerated GD and Decay. When we discuss decay character of sealed vs vented designs, it was said that one could only possibly tell the difference in a very quiet room and that in the average living room, the room itself, would swamp out the differences via its own exaggerated decay....
Is it possible that still, the room makes such a mess of the off axis that the benefits of a smooth(er) DI gets lost into the mess? Outside of having a wider sweet spot that is. I would think to consider where the listener is relation to the critical distance.
Which really throws me into a whole new thought train; how do I measure this critical distance?
Are you guys keeping track of where your critical distance is?!
At the extreme "bad" room it might. But with any care in room design, the DI should be noticeable in any room. Right next to direct sound FR. Very early reflections matter and this is harder to quantify in the two metrics that I mentioned.
Me neither
Perhaps it's subtle but 'promoting' isn't really the domain of the standard, I don't remember seeing anything written in it that explains what is considered good or bad.
Like all measurements the 2034 graphs can be used by those with a belief or agenda, but it is useful data to have.
I think if the speakers you were testing with were smaller or the curve itself began at the throat rather than being an add-on you might hear slightly more difference on the bigger ones (but probably still not worth the effort on the large ones).
It also comes back to the room and environment too with enough distance to reflective surfaces or absorption some effects of poor directivity can be mitigated.
By listening
I think its quite easy to hear. Quick story, there was very clear difference with my system, when listening at sofa the phantom center had kind of veil to it and image was kind of flat, sound only in front. Moving closer and closer to the speakers there was this point when all snapped into place, phantom center became clear, some envelopment happened, everything became more life like. I could step in and out of good sound.
Perhaps sum of many things that came together on that particular listening spot, but what I noticed was that by moving the speakers around some the "critical distance" didn't change that much, was always about 2 meters out from each speaker so I could extend it bit further out into room by having speakers closer together but never to practical sofa position ~2.5-3meters out. Now I got another set of waveguides in the system and there is not as distinct effect anymore, sound is good up to sofa and while it gets bit better by getting closer in the difference is not as great.
Based on the single experience I suggest following experiment if you want to hear it: Setup your speakers to equilateral triangle, walk on the center normal closer to line between speakers to find out where this happens. If speakers beam very highs try change toe in as well. I think when you get toe in to have nice treble where the "critical distance" is then the step in/out effect happens. Concentrate on "clarity" of phantom center and that sort of things. Move speakers closer together if it didn't happen. Start having them closer than room height, or something.
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i guess it's a perceptual construct flaw borne from how we use language to describe things, similar to the term "room gain" which is another misnomer term that drives to fits....so sorry to have interceded the flow of the thread with my thinking...carry on gentlemen.
(for the purpose of clarifying my own thinking i can not see how a passive device like a room can "add" anything, the term "add" to me implies gain,which is not possible when it comes to reverberation, after all how we perceive things with clarity is important otherwise we run the risk of falling into other rabbit holes....like distortion perception!)
(for the purpose of clarifying my own thinking i can not see how a passive device like a room can "add" anything, the term "add" to me implies gain,which is not possible when it comes to reverberation, after all how we perceive things with clarity is important otherwise we run the risk of falling into other rabbit holes....like distortion perception!)
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CEA-2034 has gained lots of popularity recently because of Klippel NFS of Amir and Erin. It is a good way to summarize spl responses at various angles. But a designer or a deeply informed reader (like we here at diyaudio) want to know more - raw measurements and spinoramas. What is happening more than 30deg off-axis, even on the backside give important information of how a speaker behaves in a room.
Waveguides, horns and coaxial drivers practically always look bad on-axis, but typically 10deg off represents Listening Window of CEA well. Vertical interferences of stacked multiway speakers have wide variance (depending on C-C distance and xo freq and type) and can be the source of bad sound - it doesn't show up in CEA directly.
Distortion and compression at various spl are also very important, but are not a part of CEA.
Waveguides, horns and coaxial drivers practically always look bad on-axis, but typically 10deg off represents Listening Window of CEA well. Vertical interferences of stacked multiway speakers have wide variance (depending on C-C distance and xo freq and type) and can be the source of bad sound - it doesn't show up in CEA directly.
Distortion and compression at various spl are also very important, but are not a part of CEA.
Well how would you do that if you don't have constant directivity??? If you think about it when Direct= Reverberant so it should change as the directivity does. The higher the DI the further away/longer distance in the same space. So where frequency wise and how would you measure it?? For a piston the DI goes up same as an exponential. A constant directivity matches DI at crossover.
So "measure" the CD after crossover and a design using an exponential when?????
Rob
You made it all complicated and stuff... The bass is going to be omnidirectional, highest treble will lead to beaming...
I think you'd pick a point, towards the bottom of something, like possibly the bottom of the critical range ~700hz...
I thought that the modes of the room are so prevalent that the critical distance is very near to the speaker... as you point out above, the critical distance is dependent on directivity.... as long as there is a consistent pattern in the off axis performance, you could definitely choose a wise place to judge critical distance... for example my polar only gets skinnier towards HF so choosing a low point makes sense. 700hz might be a good place to start, once getting low enough into the room modes and omnidirectional bass, it's probably not worth it to judge critical distance....
...you could map out critical distance vs frequency, with a "the more you know" attitude.
To even begin, youd have to know how to measure for it, which, no one seems to know how
I think you'd pick a point, towards the bottom of something, like possibly the bottom of the critical range ~700hz...
I thought that the modes of the room are so prevalent that the critical distance is very near to the speaker... as you point out above, the critical distance is dependent on directivity.... as long as there is a consistent pattern in the off axis performance, you could definitely choose a wise place to judge critical distance... for example my polar only gets skinnier towards HF so choosing a low point makes sense. 700hz might be a good place to start, once getting low enough into the room modes and omnidirectional bass, it's probably not worth it to judge critical distance....
...you could map out critical distance vs frequency, with a "the more you know" attitude.
To even begin, youd have to know how to measure for it, which, no one seems to know how
Sounds like its not for the faint of heart...I was hoping there was a software solution. I thought the critical distance was important to everyone. Maybe its just one of those things that is talked about but never really delved into. For studio application, I would like to stay within the critical distance for critical listening. I plan to listen a lot from about 54" so maybe I am well within the critical distance and it is not a concern anyway? Its important to me because I thought it was apart of the basic understanding of design. Sounds like it is not as easy, I wouldn't want to waste your time on it. If it isn't a common/popular thing to analyze, then maybe its not really that important?
I'm sorry you find objection with my my comments. I do not mean to give offense.
I do want to be able to openly discuss in friendly manner, our personal preferences and assessments of the relative importance of factors in DIY speaker building.
I like to think and hear for myself, and frankly am not very concerned when my preferences and assessments either agree or disagree with statistical preferences of rather standard consumer speakers in a standard consumer environment.
Feel the same way about preferences and assessments from those deemed as experts.
However, I do like to share and understand various perspectives .....and the causes of agreement/disagreement.
Ok, maybe noboby cares, but here my list of what matters most for MY best DIY SQ. : 'My-fi' works
1. Direct sound FR that has both flat mag and flat phase, as smooth as possible within a +/- 30 deg listening window.
2. FR that stays linear with maximum design SPL, that maintains linear headroom for transients, throughout the spectrum...particularly difficult at spectrum ends.
3.. Utilizing drivers only within the frequency range where it takes moderate minimum phase EQ to flatten their mag and phase, such that they can made to operate as fully acoustically complementary devices with neighboring drivers.
Try to achieve acoustically, how textbook complementary electrical xovers sum.
Target matched summation down to at least -20dB, -30 dB preferable. Shallow xovers are tough to achieve that , steep are easy but require linear phase xovers.
4. Minimizing driver sections center-to-center distances. 1/4 WL spacing or better.
5. I put this one last, but I don't know where it fits...maybe right below almighty direct FR.
It's keeping drivers span to a decade or less.
The increase in clarity from increasing the multi-way count on my synergy builds still blows my mind.
It wouldn't surprise me if some form of multi-tone testing, some form of modulation testing, becomes a real SQ explainer.
I am definitely not in the group anymore, that want's a CD to reach down as far as possible.
Heck, I'd change the thread title to: Is it possible to cover the whole spectrum, high spl, low distortion with a THREE-way? Lol
All the above currently outweigh any desire to try improve DI outside the listening window. It could be the electrical and acoustic design in 3. and 4. are making for an overall good enough DI, that marginal gains from mouth terminations, diffraction reduction, etc are hard to hear. I dunno.
Anyway, my preferences, my list, and just my 2c.
Can we simplify this into decreased excursion or no?
Ok I guess I need to include the whole segment....I like the way you think, not that I'm on the same page.
For me to try and break down your position I'd have to know the details of listening distance and expected spl and accumulated sd per passband. I want to blame excursion. I theorize that excursion should not go past 1-2mm, based on the discussions we've had about what happens, increasingly, beyond that point for woofers and suspension. Maybe that concept needs to be analyzed in specificity to tweeters with much lower xmax than most woofers. The ports that cover the woofers in synergy type designs, take away from efficiency and increase excursions needed to reach a spl.
Simply said, If you keep track of your radiation area, you are likely to find a connection.
Thus, I would think that for this type of experimentation one would need to "Excursion match" before drawing conclusions. That is, before comparing the "compression driver being played as low as possible" vs "multi way supporting the same passband" they should be excursion matched. Of course SPL will differ now but in essence, nulling excursion will rule it out. Also, excursion is likely a less perceivable at lower frequency.
I am trying to set an example of the experiment, it might be off a little;
System A = A single large woofer with X amount of Sd
System B= A multi way with 4 drivers covering the same passband
Set a spl/distance and passband. From there, take the excursion of the highest playing driver in the multi way, and then increase woofer size in System A until its highest excursion matches the the excursion of the highest driver of the multiway. This is an abstract way of nulling excursion but to my point. Does System B provide more clarity now? I don't think so.
Likely the hook line and sinker for evidence that your experience is excursion based is headphones. So you still want the Driver, whether Compression or not, that covers a wideband, you just don't want the problems that come with it, based on the products you've used to achieve it. Possibly the product does not exist even. Or possibly you didn't take the "reach down as far as possible." seriously enough, as in, you reached down lower than possible lol instead of reaching for low as possible. You are arguing; how low, is possible... not the idea of trying to make possible, lower.
You always have really good things to say and add so keep the change coming please lol
Interesting, I've wondered about this before. Have you ever had a play with trying to test it?
If anyone has played with FM synthesis they will probably appreciate this - if I'm understanding what I' hearing correctly IMD can sound far worse than broadband noise or harmonics very easily.
I would have expected the pressure created by e.g. the LF drivers to impact the compression driver in a synergy to some extent, but it sounds like you reckon that potential issue is disappearing into the background in comparison.
More from Crowe here - I've broken the URL as I didn't want to clog the discussion with video links: https:// youtu.be/tVUIwpo-hs0
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