Originally Posted by driver 8
Have there been any really good dual-driver headphones yet? The only ones I've heard thus far sounded awful and I don't remember impressions of a shiny Japanese headphone someone posted somewhere being the most positive either.
... were the newer FAD headphones dual-driver? I can't remember now.
The new FAD Pandora Hope VI is a dual driver: it uses a balanced armature (the first in a full sized headphone) for mids and treble with a dynamic for the bass. It actually sounds very good IMO. The K280 actually sounds really good too considering it was a weird experiment many years ago. The K340 hybrids I've heard however are amazing. Really a special headphone. Then, of course, you've got a plethora of hybrids in the IEM world.
The reason for hybrids is almost always bass. Most drivers are actually, technically, tweeters and so you have to use a number of techniques to coax bass out of them involving acoustic chambers and pads. Some drivers are inherently more problematic when it comes to replicating bass like BAs, piezoelectrics, and some planars like e-stats and ribbon drivers. Another solution for these more extreme cases is to add a dynamic driver into the mix to act as a woofer. This has a number of possible complications, the most obvious of which (to my ears) is a sort of disconnected sound between the bass and the rest of the spectrum, what people are calling "incoherence" often times. A single driver will usually have the advantage of sounding more coherent, though it potentially is at a disadvantage when it comes to replicating the full sensation of bass.
At the request of a_recording, I'm sharing this from one of our recent conversations with some added bits about ribbons.
All About Drivers! Or: Drivers On My Mind by MF
We're going to see a lot of hybrids in full-sized headphones in the coming years, in part because ribbons are increasing in popularity. I think the surge in speaker company involvement has something to do with this, though interestingly most speaker companies are playing it safe and going with consumer-level products that use dynamic drivers, banking on their reputation to appeal to folks who perhaps don't have as much experience with headphones.
The Obravo headphones are interesting to me, because in one of their headphones they're using an AMT driver. AMT drivers, or Air Motion Transformer drivers, are sort of like accordions in that they push against themselves to move air, only on a much smaller scale than an accordion; they're not actually expanding and contracting like that. Usually they're used in speakers, primarily smaller desktop speakers, though Precide uses them in their flagship headphones. Precide is the company who helped manufacture the original electrostatic Jecklin Floats, FYI. The main problem with AMT drivers however is that they are extremely bass light. The solution to this that Obravo is using is, of course, to implement a dynamic driver as a woofer. The other Obravo headphone is using a ribbon, only it's not a "true" ribbon and is likely folded in a way that makes it very similar structurally to an AMT driver. Like the AMT driver it too is getting a dynamic driver to help out in the bass department.
While I'm talking about folding drivers, I should mention the TakeT H2+ headphones. These are actually piezoelectric. Those who are unfamiliar with the technology should look it up sometime because it's very interesting. What sets piezo drivers apart from every other driver is that it doesn't need a secondary structure to act as a motive generator. In other words, it doesn't need magnets or stators to move it; the driver itself changes directly due to an electrical signal. Several headphones in the 70s utilized this technology, but they were notoriously lacking in bass and kind of limp sounding. It didn't help matters that the drivers themselves were too slack, which compounded the problem that was already inherent in the technology. Ultimately it was abandoned, consigned to history as a curiosity more than anything else. At the time however an engineer working for Sony was cooking up some ideas to use piezoelectric panels in speakers. He saw the potential of them, but the higher-ups at HQ decided to concentrate on other endeavors. Cut to a few decades later: TakeT is born from the mind of that same engineer. He recognized that the problem of bass was due to size, and that the piezoelectric drivers needed to be bigger in oner to produce a more satisfying bottom-end. Unfortunately the size required for this was simply too large to be practical for headphone use. His solution was rather ingenious in its simplicity: fold the drivers similar to an AMT driver so that you could fit more of it in a smaller space. Even folded up like they are, the TakeT drivers are massive for a pair of headphones. The result is almost comically overcompensating: the bass on them is massive.
I'm most interested in what RAAL is doing right now though; they're working on a true ribbon driver. A true ribbon isn't folded, but rather a planar sheet of foil suspended in a magnetic field, usually between rows of magnets along its length. It's similar to an orthodynamic / isodynamic driver, but in comparison those consist of traces of wire laid out on a diaphragm in a circuit sandwiched between larger, circular magnetics. In simple terms, think of a ribbon like an electrostatic driver, only instead of the electrical charge it uses a magnetic field like an ortho or dynamic.
RAAL claim that true ribbons have several advantages over hybrid ribbons. For starters, a folded ribbon is going to sound more distorted, more like the metal foil from which it's made. RAAL refers to the sound as "kitchen foil" LOL. Now, in speakers this isn't such a big deal---O'bravo's folded ribbon is probably fine in that application---but as RAAL points out (not referring to anyone in particular), a folded ribbon that sits so close to your ears is another story. Tom reported that the O'bravos didn't sound very good to him; perhaps this is why? RAAL have gone to great lengths according to their reports to minimize any unwanted noise, going so far as to add an embossed pattern to their ribbons to break up any standing waves that might form on their surfaces.
Perhaps the most interesting claim (to me, at least) is that they don't need to use anything to supplement the bass response. No acoustic chambers, no dynamic driver hybrids or crossovers. They say that a natural ribbon driver is technically a woofer and not a tweeter like most other drivers, so it's able to reproduce those low frequencies without any "tricks" to wring them out of it.
Why don't more companies use true ribbons? Well, the biggest obstacle is their ridiculously low impedance. We're talking well below 1 ohm. Thus you need some kind of specialized amp to handle it, and RAAL is working on just such an amp. Talking to one of their reps about it, supposedly the cost for the set (headphones and amp) will be around $2500 USD, with a price of $1400 USD for extra headphones.
Since I'm talking about different drivers and new headphones, I wanted to add something about the new HiFiMan models. It's nice that Dr. Fang is concentrating on ergonomics and making his headphones more comfortable. Included in that is, of course, the weight of them. The new LCD-X and XC from Audez'e are just way too heavy for their own good. Combined with the billowy padding, it's not unlike being smothered to death in your sleep by a pillow. Now as far as Dr. Fang is concerned, smaller drivers are out of the question (more on this later), so the main solution lies in the magnets which constitute much of an ortho's weight. The upcoming HE-400i and HE-560 will be one sided, meaning they have only one magnetic instead of that two-magnetic sandwich I mentioned above.
Some feel this configuration is inherently at a disadvantage compared to double sided drivers. There might be some truth to that, however if engineered properly I don't think it's actually audible personally. Speakers having been using single sided ortho drivers for a while, and recently the Abyss has demonstrated that single sided ortho drivers in headphones can sound phenomenal. Sorry, I can't help myself and need to talk about the Abyss for a spell. Everything about the Abyss' construction was actually very well thought out and tested. In fact the single magnet was something of a necessity, because the Abyss' custom made magnets are the most powerful ever to be implemented in a headphone so far; having a sandwich of two magnets resulted in the driver tearing itself apart! Really it's almost scary how powerful they are: when taking the Abyss out of its tote bag, the metal rings of the bag stick to the sides of the headphone! Maybe they should put a warning about using it if you've got a metal plate in your head. Or metal fillings.
Anyway, I don't foresee the single sided drivers being a problem for HiFiman. Headphone magnets are much nicer these days. By comparison, back when orthos were first invented, some of the Soviet models used glorified refrigerator magnets.
I will say, it's a shame Dr. Fang isn't on board with regard to smaller ortho drivers. A friend of mine who knows quite a lot about engineering headphones had a discussion with him about their utility, and they seemed to have a fundamental disagreement. My friend's wish is to see a small, portable orthodynamic headphone that could be driven effectively out of an iPod and doesn't cost, say, over $400. He---and I---think this could most certainly be done, and that it would sound quite good if done right. Really, as far back as the late 70s Yamaha was able to produce truly portable ortho drivers. There was this strange beauty:
Not to mention there are also smaller drivers used in the other Yamaha and Fostex models; the truly excellent-sounding T10 can be used as a portable, for instance. It's kind of funny, but in many ways we're still "catching up" to these drivers. When orthos were rediscovered, it was almost like it was the rediscovery of some lost art. By comparison the drivers made by HiFiMan are actually a little crude when you compare them side-by-side. Of course, there have been some really impressive advancements like the LCD-3 drivers (despite their instability) and those of the Abyss which are completely air-damped. However the true test I think will be just how much we can improve on smaller orthos.
I'm actually very eager to hear the new Oppo headphones. More than any other planar magnetic thus far, they appear to be a true consumer-grade product in terms of their design and ergonomics. Really, the stuff Audez'e, HiFiMan, and especially JPS are putting out could only fly in the world of audiophiles.