irb
pfm Member
The recent threat started by davidismynaim about digital crossovers raised an issue I've often thought about: whether panels can be mated successfully with dynamic woofers.
I own, or have owned in the past, several speakers of this type: the Innersound Isis, the Martin Logan Vista (both electrostatic hybrids), and the Apogee Centaur (a ribbon hybrid). All were/are capable of superb results, but in all three cases there was, to my ears, a discontinuity between the woofer and the panel/ribbon. The Centaur, which I still own, is by far the worst. But the ribbon is superb!
I've read many comments about this issue over the years. Usually these have focused on the 'speed' and lightness of the ribbon/electrostatic panel, as opposed to the slowness and weight of the woofer.
Surely this is the wrong way to look at the problem, though.
Conventional moving coil drivers can move their cones plenty fast enough to cover the required range. If they couldn't, it would show as limited frequency response. There is, I accept, an issue about the differing resonant signatures of the woofer cone material and the panel/ribbon. However there's another issue, which I suspect is much more important, but which often gets neglected: dispersion.
If you combine a large electrostatic panel (or a long ribbon) with a moving coil woofer in a box, there are two reasons why they radiate sound into space differently. First, the ribbon/panel is a dipole radiator, generating a figure of eight pattern, where the woofer is monopolar, and therefore essentially omni-directional. Second, the dipole is operating as a line source, while the woofer is a point source: a line source limits dispersion in the vertical axis, as well as altering the way sound falls off with distance.
There's been wide recognition, in recent years, of the importance of loudspeaker dispersion/directivity. Large, sudden shifts in dispersion are generally agreed to be a bad thing. The implication for hybrid speakers is obvious: if you really want to combine moving coil woofers with long ribbons or panels, you should use your woofers in a dipolar, line source configuration, to match the ribbon/panel dispersion pattern.
I have owned one speaker which combined a long ribbon with a dipole mid and woofer: the Dali Skyline 2000. They were probably the best speakers I've owned, all round. But they still didn't address the line source/point source problem.The only speakers range I'm aware of that have gone the whole way and combined a long dipole ribbon-type driver with a line of dipole woofers, was the old Carver Amazing range. I've never heard them, though. (Hardly any made it to the UK, I guess.)
I'm tempted to try a diy project: Apogee ribbon (from the Centaurs), combined with a line of dipole woofers. Maybe even line of dipole mid-woofers, and a line of dipole subs.
It makes perfect sense. Or does it? What do people think?
I own, or have owned in the past, several speakers of this type: the Innersound Isis, the Martin Logan Vista (both electrostatic hybrids), and the Apogee Centaur (a ribbon hybrid). All were/are capable of superb results, but in all three cases there was, to my ears, a discontinuity between the woofer and the panel/ribbon. The Centaur, which I still own, is by far the worst. But the ribbon is superb!
I've read many comments about this issue over the years. Usually these have focused on the 'speed' and lightness of the ribbon/electrostatic panel, as opposed to the slowness and weight of the woofer.
Surely this is the wrong way to look at the problem, though.
Conventional moving coil drivers can move their cones plenty fast enough to cover the required range. If they couldn't, it would show as limited frequency response. There is, I accept, an issue about the differing resonant signatures of the woofer cone material and the panel/ribbon. However there's another issue, which I suspect is much more important, but which often gets neglected: dispersion.
If you combine a large electrostatic panel (or a long ribbon) with a moving coil woofer in a box, there are two reasons why they radiate sound into space differently. First, the ribbon/panel is a dipole radiator, generating a figure of eight pattern, where the woofer is monopolar, and therefore essentially omni-directional. Second, the dipole is operating as a line source, while the woofer is a point source: a line source limits dispersion in the vertical axis, as well as altering the way sound falls off with distance.
There's been wide recognition, in recent years, of the importance of loudspeaker dispersion/directivity. Large, sudden shifts in dispersion are generally agreed to be a bad thing. The implication for hybrid speakers is obvious: if you really want to combine moving coil woofers with long ribbons or panels, you should use your woofers in a dipolar, line source configuration, to match the ribbon/panel dispersion pattern.
I have owned one speaker which combined a long ribbon with a dipole mid and woofer: the Dali Skyline 2000. They were probably the best speakers I've owned, all round. But they still didn't address the line source/point source problem.The only speakers range I'm aware of that have gone the whole way and combined a long dipole ribbon-type driver with a line of dipole woofers, was the old Carver Amazing range. I've never heard them, though. (Hardly any made it to the UK, I guess.)
I'm tempted to try a diy project: Apogee ribbon (from the Centaurs), combined with a line of dipole woofers. Maybe even line of dipole mid-woofers, and a line of dipole subs.
It makes perfect sense. Or does it? What do people think?