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Quote:
Jazz, thank you for posting here, you know quite a lot, it's instructive! I haven't followed up with the ring designs for tweeters in years (is it ScanSpeak (Revelator or something) that starting to make it for tweeters as opposed to conventional use in compression drivers?). So, I do not know what flaws started to be found (for all I know, it was the best thing since sliced bread when I read about it 10 years ago or so).
But I would also suspect there is little more in common than the name between ring tweeters and this ring headphone driver.
Target frequency range / SPL / electrical impedance are drastically different. Tweeter is listened to in the acoustic far field while headphone membrane is in the very near field. That results probably in quite different requirements / potential issues.
Quote:
Indeed, one requirement for speakers is to prevent acoustic cancellation of front and back waves at low frequencies because you can't get bass sounds to efficiently radiate away. In the case of headphone, you're in the near field so you can actually work with open design (e.g. Senn's headphones). Having said that, there are still issues as you said as, for instance, it's commonly agreed that closed headphones tend (not a generalization but it is a trend) to have more bass (at least more impactful). But the perfect headphone is more likely the open type with as little sound reflections as possible (that is until people also want isolation from outside world, can't have it all!!)
Quote:
In regards to dynamic drivers sounding more impactful than electrostatic designs I also feel the same and would guess is because there's actually really no stiff piston motion with thin electrostat membranes. They're as fast as can be but the motion is probably nowhere near that of a plane moving in phase from end to end. So somehow maybe this makes us feel like the bass is lacking foundation. I also agree with you that dynamic drivers have come a long way and don't pale much against electrostat "paper" membranes in the speed department.
For speakers, as has been said, ideal dynamic type driver (as far as distortion from input signial is concerned) is a massless perfectly ridid surface (moving like a piston). For speakers, directivity is also a big concern so unfortunately, law of physics will have you want to use a large piston for low frequencies and small one for higher frequencies.
But in the case of headphones, there is no such requirement on directivity because we're in the near field of the driver. The ideal headphone transducer thus "only" needs to throw a plane wave at some angle of the head to mimic that of a speaker pair at 30 degrees or so (for listening to standard stereo recording). There is no such thing as a plane wave within 1 inch from a vibrating membrane but maybe just orientating the driver at some angle does a sufficient trick as Sennheiser (and many others before) have found.
In terms of actual driver "distortion", there is probably no difference in requirement between speaker and headphone. You need a fast and rigid membrane ideally with as least damping as needed to control imperfections (such as break up modes in the diaphragm). If you look at the HD800 vs. HD650 design, the HD650 employed probably quite a bit of damping to control the diaphragm resonances and it does not sound very lively. Oppositely, the HD800 appears very fast from the few who heard it. It also does not appear to have nasty resonances which would imply the ring surface actually does not present much resonances in the passband region (or at least the mode shape is such these resonances don't completely mess up the acoustic response, not sure how this can be but...).
BTW John Willett, is there ring type microphone capsule? Maybe soon to come from Sennheiser then?
arnaud.
| Originally Posted by JaZZ /img/forum/go_quote.gif It depends. Personally a have a lot of experience with speakers, but none with ring radiators. All I can tell is that they have a decisive downside when used in tweeters: a more inhomogeneous, frequency-dependent radiation than conventional dome tweeters. At the same time they seem to be -- measurably and reportedly -- «faster» than the latter. With headphones, the mentioned downside doesn't have much importance, so it's the advantage which counts. . |
Jazz, thank you for posting here, you know quite a lot, it's instructive! I haven't followed up with the ring designs for tweeters in years (is it ScanSpeak (Revelator or something) that starting to make it for tweeters as opposed to conventional use in compression drivers?). So, I do not know what flaws started to be found (for all I know, it was the best thing since sliced bread when I read about it 10 years ago or so).
But I would also suspect there is little more in common than the name between ring tweeters and this ring headphone driver.
Target frequency range / SPL / electrical impedance are drastically different. Tweeter is listened to in the acoustic far field while headphone membrane is in the very near field. That results probably in quite different requirements / potential issues.
Quote:
| Originally Posted by JaZZ /img/forum/go_quote.gif In conventional closed speakers a dynamic bass driver has a stiff membrane and thus contributes to the seal of the air-tight system. That's necessary to enable calculation of system parameters (TSP), i.e. low-frequency response. Now a «woofer» with a soft foil membrane behaves completely different. Actually it doesn't guarantee an airtight system at all, moreover the produced rear sound waves can mix with the front waves as parasitic sound. Additionally the membrane is a plaything of the sprung back air molecules, out of control, so to speak. Although most headphones aren't closed systems, the same mechanism could be detrimental to a clean, accurate transient control. |
Indeed, one requirement for speakers is to prevent acoustic cancellation of front and back waves at low frequencies because you can't get bass sounds to efficiently radiate away. In the case of headphone, you're in the near field so you can actually work with open design (e.g. Senn's headphones). Having said that, there are still issues as you said as, for instance, it's commonly agreed that closed headphones tend (not a generalization but it is a trend) to have more bass (at least more impactful). But the perfect headphone is more likely the open type with as little sound reflections as possible (that is until people also want isolation from outside world, can't have it all!!)
Quote:
| Originally Posted by JaZZ /img/forum/go_quote.gif Theoretically electrostatic and orthodynamic drivers still are faster and able to produce a more precise and cleaner sound. But here's where diverging philosophies show up. To many ears theory doesn't entirely bear up with reality. After all, before the HD 800 era it was clear to most that electrostats have much higher treble resolution. But the farther down in the frequency range, the more dynamic headphones sound more palpable, more substantial, more controlled. Why is this so? I don't really know. I just guess that it has to do with the thin and soft foil membrane as sound generator. |
In regards to dynamic drivers sounding more impactful than electrostatic designs I also feel the same and would guess is because there's actually really no stiff piston motion with thin electrostat membranes. They're as fast as can be but the motion is probably nowhere near that of a plane moving in phase from end to end. So somehow maybe this makes us feel like the bass is lacking foundation. I also agree with you that dynamic drivers have come a long way and don't pale much against electrostat "paper" membranes in the speed department.
For speakers, as has been said, ideal dynamic type driver (as far as distortion from input signial is concerned) is a massless perfectly ridid surface (moving like a piston). For speakers, directivity is also a big concern so unfortunately, law of physics will have you want to use a large piston for low frequencies and small one for higher frequencies.
But in the case of headphones, there is no such requirement on directivity because we're in the near field of the driver. The ideal headphone transducer thus "only" needs to throw a plane wave at some angle of the head to mimic that of a speaker pair at 30 degrees or so (for listening to standard stereo recording). There is no such thing as a plane wave within 1 inch from a vibrating membrane but maybe just orientating the driver at some angle does a sufficient trick as Sennheiser (and many others before) have found.
In terms of actual driver "distortion", there is probably no difference in requirement between speaker and headphone. You need a fast and rigid membrane ideally with as least damping as needed to control imperfections (such as break up modes in the diaphragm). If you look at the HD800 vs. HD650 design, the HD650 employed probably quite a bit of damping to control the diaphragm resonances and it does not sound very lively. Oppositely, the HD800 appears very fast from the few who heard it. It also does not appear to have nasty resonances which would imply the ring surface actually does not present much resonances in the passband region (or at least the mode shape is such these resonances don't completely mess up the acoustic response, not sure how this can be but...).
BTW John Willett, is there ring type microphone capsule? Maybe soon to come from Sennheiser then?
arnaud.
