more dumb, not rhetorical, questions:
what is the definition of "acoustic center" ?
how do we know when they are aligned? A tone burst?
what is the definition of a point source?
I am completely confused.
Is there a book on this stuff?
herb
Coaxials - Reality vs. Experience?
Should say "hype vs. reality" in the headline.
Coaxial speaker design has been around in one way or another for a long time. I often think I’ll be absolutely blown away by them, but in practice traditional vertical layout speakers often have sound as good, or have other features that make them sound better.
Thiel, KEF, Monitor Audio, Tekton, Seas are among the many players attempting such designs, but none has, by the coaxial drivers alone, dominated a segment of the market.
What are your listening experiences? Is it 1 coaxial speaker that won you over, or have you always preferred them?
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@mulveling I have no problem with the assist. I respect your thoughtful/experience based opinions. I am referencing the majority of coaxials on the market (home hifi not the old Jensen co/tri-axials of yore). Examples, as have been mentioned by others/myself, Tannoy, Kef, TAD, MOFI's new two way (Sourcepoint 10), diy drivers (Eminence, Seas, SB acoucoustcs, B&C, BMS.........). Of course, some of these models are not exclusively concentric (mid/hi, low-mid/hi), but are aumented with low frequency drivers. @herbreichert You communicate/resonate fabulously with the inner artist in all of us that think we have an inner artist! Appreciate your style. As Mulveling mentioned, looking directly at the driver in question (as JA would perform an on axis measurement of MOFI's Sourcepoint 10); the attempt by most of these (passive) designs is to time align the acoustic centers (dual concentric) of these coaxials to best approximate a point source How accurate each designer is at this is up to measurements. If the sound/presentation is "good" is up to personal preference. Of course, the drivers don't have to be concentric, but still coaxial and the time alignment adjusted via dsp (fully active in speaker solution or external with a DEQX, for example........each with its own pros and cons). Be happy to try and clear any waters I may have muddied. Herb, you're the pro, I am just a guy with some electronics and a room full of drivers.
@erik_squires You speak in generalities or specifics when each suits you, not when it suits the details of the discussion. Tell me about the real world D'Appolito arrays you have deigned/built/tested and formed opinions on through listening to at your home. Or for that matter, listened to out in the wild. Your experiential observations of point source style speakers vs any two way D'Appolito array speaker? Crickets? You LITERALY can't have a point source! A point source is an abstraction, it doesn't exist in reality. We use the idea of a point source to model and make calculations that can help guide a particular design. The theoretical pros and cons (and the relative importance of each) of any particular design will play out once you select drivers, select crossover type (active/passive), create a pile of sawdust, twist a screwdriver, skin some knuckles, measure, listen, adjust, rinse and repeat. The devil is in the details (apology for the hackneyed phrase). Erik, thank you for the reading suggestions, but the design literature I read pre internet has served me and my ears quite well. There are as many opinions as keyboards out there, each telling you which benefit they champion on whatever design. There is no inherently "good" thing about narrow vertical dispersion unless your use case for some reason necessitates it. (Also, I believe you interchanged vertical/horizontal in your two previous posts). One doesn't go into a store and the audio clerk says " this speaker has narrow vertical dispersion, so it's the BEST you can buy!" For gigs....If you had a two-way MT bookshelf (with its unique dispersion pattern) and create a quick and dirty D'Appolito array lengthening the baffle and symmetrically placing a matching M above the T creating a MTM (appropriately altering the crossover) your main gains you put your benjamins down for are: Mimicking point source for that perceived presentation, Higher power handling (louder, but at the expense of lower impedance), Lower midrange/woofer distortion due to less cone movement, lesser impact of ceiling/floor interaction (in my experience....meh) Erik, disagree as vociferously as you like..........now go make some sawdust and enjoy some righteous tunes! Well wait.......... you still haven't explained "off-plane axis listening". (Tasty geometry salad)😋. I listen only in the "sweet" spot.....where all the magic happens! (There are probably numerous errors above, not having typed this much since my last term paper. Retractions, denials, apologies to follow. Good night gentlemen/gentlewomen/gentlefluids, my wife is yelling at me to get my fingers the frick away from the keyboard. |
@herbreichert The point in space from which sound appears to originate in terms of time. Think of a woofer and tweeter mounted on a flat baffle. Look at it from the side. The tweeter's acoustic center is practically at the baffle, but the woofer's may be 1" or more behind the baffle. Speaker designers have to take this into consideration for either phase or time alignment.
Kind of depends how you mean "alignment." Phase aligned you can tell by an smooth transition from one driver to the other. Time aligned you can see using a step response. See figure 9 in these measurements for time aligned speaker step response.
A theoretical "ideal" (one of many ideals) in which the full range of sound appears to come from a single point in space. A single, full-range driver is by definition a point source. Some multi-way speakers may attempt to mimic this behavior in time and space. The Duntech Sovereign is a famous, early-ish example. Contrast to a line-source, like the famous Infinity RS.
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@herbreichert PS - Your typical 2 or 3 way speaker is neither a point nor a line source. Vandersteen may be time and phase aligned but it’s not a point source. That perfect step response in the Stereophile measurements goes out the window when you stand up. :) A true point source maintains it's time alignment no matter where you measure it from. |
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