Dynamic Drivers are still very competitive because the technology is mature. It is easier to manufacture and the advantages/disadvantages are known. My favourite headphone & IEM are both dynamic drivers: the Sennheiser HD800S & Ocharaku-Donguri Kaede.
Anyway here's my summary of the pros & cons of each technology from my listening experience and through browsing forums:
---Dynamic Driver Diaphragm Variations--- -----------------------
Metallic (Al/Be/W) Diaphragm Dynamic Driver: <Elear/Elex/Clear/Utopia/ADX5000>
+ Very fast impulse response, sounds punchy and fast, but still not at the level of planars or electrostatics
+ Materials all react quite similar allowing good channel matching at higher frequencies
- There are resonances specific to each metal. This can be reduced by mixing different materials or combining a softer material to dampen it.
- Quite hard to shape treble frequency response to be smooth on headphones, but easily done on speakers
- Decay is edgy as the diaphragm tends to continue vibrating even when music is stopped. This can by combining a softer material to dampen it.
Hard (LCP/DLC) Diaphragm Dynamic Driver: <Z1R/Z7M2/EX800/EX1000/MSR7/Kanas/KXXS/>
+ Very fast impulse response, sounds punchy and fast, but still not at the level of planars or electrostatics
+ Very rigid allowing for good control of treble
+ Allows for bigger diaphragm sizes, giving it more power handling for bass
+ Low distortion
- Decay is edgy and negatively impacts mids. This can by combining a softer material to dampen it.
Soft (Plastic/Rubber) Diaphragm Dynamic Driver: <HD600/HD650/HD660/Aeolus)
+ Very natural smooth mids
+ Very good damping, making it easier to sculpt the frequency response
+ Cheap to produce
- High bass distortion. Could be fixed by making it closed back but then that would introduce reflections and reduce soundstage.
- High distortion when played at loud volumes. Bass in particular doesn't have realistic texture as the diaphragm wobbles too much
- Sub bass & high treble frequencies are usually rolled off
- Will need to produce a high amount of drivers to get nicely matched drivers, if not imaging will be impacted
Biocellulose/Fabric Diaphragm Dynamic Driver: <NightHawk/NightOwl/Auteur>
+ Very natural sound, especially the mids
+ Good impulse response, and punch
+ Low resonance since fibers are all of a different length
+ Typically have excellent bass, think of those ScanSpeak Woofers
- Needs damping to control the slow decay
- Variance in production of material, hence hard to channel match and impacting imaging
- Damaged by moisture, doesn't last forever
Ring Radiator: <HD800/HD800S>
+ Lighter than normal Dynamic Drivers, allowing for better treble
+ With the right placement, sound reaches your ear canal at the same moment, improving imaging. However our ear canal counteracts this.
- Although soundstage is huge, voices sound unnaturally big
- Diaphragm area size is wasted as the central part is not moving any air
Coaxial/Concentric Driver: <KEF/Phantom>
+ Point source, giving better imaging for speakers especially when listening to speakers near field or when filling a room with a mono config
+ Allows the tweeters to focus on the higher frequencies, improving clarity. The bigger mid drivers (on the ouside) can focus on mids and lows
- More expensive to produce
- Does not play very loud comparative to it's size and weight as overall size of outside diaphragm is reduced
---Flat Diaphragm Variations--- -----------------------
Planar Magnetic (Line Trace, Dual sided magnet array): <LCD2/Verum1/HE5/HE500/M1060>
+ Excellent full bass, the only driver that gives realistic drums
+ Can play really loud and distortion % relatively goes down
+ Large and thin diaphragm allows for wide sounding soundstage. Though live recorded instruments can sound unnaturally big.
- Big diaphragms and big magnets would make it very hard to make it closed back without introducing reflections. Also you lose the soundstage.
- Harder to find matching drivers with the same treble frequency response. Harder and more expensive to get the same imaging as dynamic driver.
- Magnet reflections, negatively impacting imaging making it fuzzy, though Fazor/Fuzzor mods have tried to fix this
- Rectangular shape of diaphragm and the use of magnets on both sides in between traces end up making the headphones heavy
- Mids are usually not as smooth as it's harder to sculpt the frequency response without the variable resistance
Planar Magnetic (Line Trace, Outside magnet array): <HE4XX/HE400>
+ Great soundstage for open back headphones since you can hear the outside sound
+ Big sound, though live recording instruments can sound unnaturally big and give impression of blobs of sound
+ Sound is cleaner than double sided magnet array as there are no magnets in the way
- Harder to find matching drivers with the same treble frequency response. Harder and more expensive to get the same imaging as dynamic driver.
- Bass will roll off badly as there is not enough force to push the diaphragm, without magnets on other side pulling the diaphragm
- Resonances are harder to control and also distortion will be bad at higher volumes, making it closed back fixes it but reduces soundstage
- Rectangular shape of diaphragm and the use of magnets still make the headphones relatively heavy
- Mids are usually not as smooth as it's harder to sculpt the frequency response without the variable resistance
Planar Magnetic (Circle Trace, Outside magnet array): <PM-1/PM-2/PM-3/Panda>
+ Good soundstage for open back headphones since you can hear the outside sound
+ Makes the sound more natural compared to line trace as the sound waves reach your ear at a more similar time, sounds more like DD
+ Lighter than dual magnet arrays and rectangular line traces, though soundstage is not as big
+ Innovative ideas such as combining circular and line trace such as in Meze Empyrian gives best of both worlds
- Harder to find matching drivers with the same treble frequency response. Harder and more expensive to get the same imaging as dynamic driver.
- Hard to tighten diaphragm, leading to resonances in unnatural frequencies
- Resonances are harder to control and also distortion will be bad at higher volumes, making it closed back fixes it but reduces soundstage
- Mids are usually not as smooth as it's harder to sculpt the frequency response without the variable resistance
V-Planar Diaphragm (Line Trace, Inside magnet array): <Aeon/Ether>
+ More diaphragm area can be fitted in a smaller amount of space
+ Good soundstage for open back headphones since you can hear the outside sound
+ Lighter than dual magnet arrays and rectangular line traces, though soundstage is not as big
- Since magnets are on ear side, sound is reflected and diffracted. The Flow system aims to mitigate this.
- Harder to find matching drivers with the same treble frequency response. Harder and more expensive to get the same imaging as dynamic driver.
- Soft presentation, probably from a slower impulse response. Also negatively affects imaging
- Sub bass rolls off as there is not enough force to push the diaphragm without magnets on other side pulling the diapraghm
- Since diaphragms are untightened, it leads to resonances in unnatural frequencies. Making it closed back fixes it but reduces soundstage
- Resonances are harder to control and also distortion will be bad at higher volumes
- Mids are usually not as smooth as it's harder to sculpt the frequency response without the variable resistance
Electrostatic (Dual Sided Stators): <RR1/Stax>
+ Light diaphragm that has no metal traces (lighter than air) leads to amazingly fast impulse response and especially decay
+ Amazingly fast, clean and natural vocals
+ Good soundstage for open back headphones since you can hear the outside sound
+ The use of stators rather than magnets means there are no less reflections on the sound. Plus, they make the headphones really light.
+ Can play really loud (limited by your amplifier) and distortion % relatively goes down
- Need a separate amplifier/energizer which can be quite an investment. They have a specific bias making them only work on specific headphones.
- Although the headphones are light, the need for a separate amplifier/energizer really piles up the weight. It's not very mobile or convenient.
- Even the Sonion EST tweeters need a separate transformer, bringing up the cost and weight
- Harder to find matching drivers with the same treble frequency response. Harder and more expensive to get the same imaging as dynamic driver.
- Need to be careful handling them since high voltages used are higher than the resistance of our skin
- To avoid the Stax Fart, you shouldn't wear, move, or take off the headphones when it is energized
- Fragile. Really hard for to produce, keep and maintain. Cannot be used when humidity is high since arcing can occur.
Electrostatic (Outside Sided Stator): <Can't comment, I hope to eventually listen to the Sonoma Acoustics M1>
Ribbon: <Sierra-2EX/RAAL Requisite>
+ Light diaphragm leads to amazingly fast impulse response and decay
+ Amazing extension on treble
+ Since diaphragm is held on one axis, dispersion is great on one axis but terrible on the other
- Doesn't have as much physical excursion as planar magnetic as the diaphragms are held in place on the side
- Doesn't play low frequencies very well, and especially can't play them very loud. The power at which bass is played are likely to break the ribbon
- Impedance is low requiring a matching transformer to be used which brings up the cost and weight
- Very fragile
--- Other Driver Variations --- -----------------------
Balanced Armature: <ER4SR/Andromeda/Zeus>
+ Really fast impulse response and decay due to small size of the punching arm. However the short decay does make the bass unnaturally clean
+ Small (so you can fit many into IEMs to get desired FR)
+ Deep insertion IEMs like the Etymotic shift unnatural closed resonances to a less annoying frequency
+ Mids are very clean and clear, very electrostatic like
- Balanced Armatures only play well on a specific frequency range. You have to fit many Balanced Armatures to get the perfect sound. This causes crossover distortion and also bringing up the cost
- Due to it's small size, it does not play very loud. To increase the power handling of the IEM, more drivers need to be utilized, bringing up cost.
- Due to how it works, there is no point making an open back (or headphone sized) Balanced Armature since you're not getting much soundstage
Electret: <JP1>
+ Fast impulse response like an electrostatic
+ Works well in a limited frequency range for the treble
- Because there is no stator giving the bias and it relies on it's own charge, it just doesn't play very loud
- Limitations in controlling FR
- Channel imbalances due to loss of charge bias over time
Piezoelectric: <A6mini>
+ Works well in a limited frequency range for the treble
+ As it can be placed in front of any other driver, it could be useful to fill the high treble frequencies in IEM applications
- Tizzy vibrating sound
- Doesn't play very loud
- Limitations in controlling FR
AMT: <Can't comment, I hope to eventually listen to the Heddphone>