It also means that the voice coil diameter may be less than the suspension diameter.
It would emulate bending modes of larger drivers, particularly if it's a more rigid material.
Dunno how much I would be willing to spend on something that operates beyond my hearing threshold (13 kHz and falling)...
Sent from my Nexus 6 using Tapatalk
It would emulate bending modes of larger drivers, particularly if it's a more rigid material.
Dunno how much I would be willing to spend on something that operates beyond my hearing threshold (13 kHz and falling)...
Sent from my Nexus 6 using Tapatalk
In typical convex domes the voice coil diameter is the same as the edge diameter. When breakup starts, the tip goes in antiphase with the rim. In a concave dome the coil can be smaller, but I wouldn't claim that it always is. If it is smaller, you could potentially get slightly better off axis once breakup starts, but measurements I have seen don't seem to lend much credence to that theory. Making the domes metal moves the resonance ultrasonic anyway....
Yes, Anji has it right. It's a sperically contoured "cone". A "dome" has its voice coil at the perimeter of the hemisphere. A "wide-surround" dome is still classed as a dome because the doughnut is outside the voice coil, otherwise we'd have to come up with another term- maybe pond-ripple shaped tweeter?
If you see waveguide-like dispersion it's because at a distance they are geometrically similar(like when we are close we must cluster multiple drivers to obtain a point-source, but at a distance the geometry makes it easier). Unlike light, sound does not have any dual ray/wave behavior, so if you see rays and arrows in an explanation it's like giving local directions- we are (hopefully consciously) using a bad but really convenient model, as it's so much easier when it works. Hence all the difficulty in understanding what the mareketers call wave launch.
If you see waveguide-like dispersion it's because at a distance they are geometrically similar(like when we are close we must cluster multiple drivers to obtain a point-source, but at a distance the geometry makes it easier). Unlike light, sound does not have any dual ray/wave behavior, so if you see rays and arrows in an explanation it's like giving local directions- we are (hopefully consciously) using a bad but really convenient model, as it's so much easier when it works. Hence all the difficulty in understanding what the mareketers call wave launch.
Last edited:
This is the one of the few infos I could find about inverted/concave tweeters by focal.
Inverted Dome
The most striking aspect of Focal’s tweeters is that they are concave instead of convex. By inverting the dome, Focal is able to achieve two goals, greater efficiency and greater accuracy. In a traditional convex dome, the voice coil is placed on the outside edge of the driver, where almost 50% of the electrical impulse is lost to the damping action of the rubber surround. By inverting the dome, Focal is able to place a smaller voice coil right on the driver itself for excellent electrical efficiency and reduced moving mass. The result is an astonishing amount of retrieved detail which was once previously obscured and greater composure at any volume setting.
Inverted Dome
The most striking aspect of Focal’s tweeters is that they are concave instead of convex. By inverting the dome, Focal is able to achieve two goals, greater efficiency and greater accuracy. In a traditional convex dome, the voice coil is placed on the outside edge of the driver, where almost 50% of the electrical impulse is lost to the damping action of the rubber surround. By inverting the dome, Focal is able to place a smaller voice coil right on the driver itself for excellent electrical efficiency and reduced moving mass. The result is an astonishing amount of retrieved detail which was once previously obscured and greater composure at any volume setting.
Yes, this is why they are not domes, but hemispheric 'cones'. This is marketing. I happen to really like them, the old Epicures, the Focals, and the TBs. But increase the size to 1.5", 2", etc and they call them one-piece cones. So we have to separate physical descriptions from marketing hype. When we see the voice coil pushing through the cone on an overdriven 3 or 4 inch fullrange we can visualise the breakup modes of our similar tweeters which move on a much smaller scale.
The claim of less loss due to the surround/coil relationship is cow-patties, I love my Focals, but that surround is pretty stiff.
The claim of less loss due to the surround/coil relationship is cow-patties, I love my Focals, but that surround is pretty stiff.
Last edited:
Hi Casull,
Not sure why it is called "oil-can" but in metal tweeters you'll see this as a severe peak, typically 10kHz or higher.
Often this peak vanishes off axis, so careful planning or turning of the speaker will resolve it. Here is a typical example from the Monitor Audio RS6. This speaker sounds much better than that peak would lea you to believe, note the 12 dB above average peak at 20kHz:
Not sure why it is called "oil-can" but in metal tweeters you'll see this as a severe peak, typically 10kHz or higher.
Often this peak vanishes off axis, so careful planning or turning of the speaker will resolve it. Here is a typical example from the Monitor Audio RS6. This speaker sounds much better than that peak would lea you to believe, note the 12 dB above average peak at 20kHz:
Don't mistake marketing for a scientific explanation. Both the greater efficiency and greater accuracy claims are spurious, the comment about rubber surround is silly...
It's not superior, it is just different. It is a way to stand out from the crowd, for the most part. It may have to do with the manufacturing method they chose or were capable of at one point, and it became a "trademark" of sorts. As I recall, the 25mm Focal tweeters back in the ARIA 5 days had a ~20mm coil.
The fact that they place the coil on the cone means a joint of some sort, and that means more process variability.
"Why is it called oil-can?" Oh, my child. In the olden days mechanical devices needed(or were able) to be periodically lubricated. We had these things like a half-dome shaped can with a long snoot tapered to a tiny tip. We would hold the can with our thumbs on the bottom, and when we wanted a drop of oil to leave the tip, press in the bottom. It would deform the otherwise mostly flat bottom and make a click or tink sound. We are not referring to the change from buying oil in cans to buying oil in plastic containers.
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.