There's a very sharp misconception surrounding the sp3k that unfortunately has become a bit of a...repeated because enough people said it type scenario. The sp3ks amp puts out 6.3vrms which is about 9volts. The m9+ puts out 6volts only, 3volts less on its balanced output, I believe it's turbo or headphone mode whatever it's called ups this by 1 to 2 volts, either way still less than the sp3ks output.
The sp3k is not going for a bombastic type approach to sound, it is neutral with an emphasis on clarity and detail. The common misconception also is that something like the 475 is powering or "scaling" an iem better, the majority of iems are far below 32 ohm impedance and require only a few watts to run, if even 1 watt in some cases which at 32ohms is going to be requiring a lot less than 9 volts. The 475 is simply causing better "dynamics" because it doesn't care about the same things the sp3k amp is designed to care about.
I'm sure I'll get flak but guess what, no iem needs a desktop amp to be powered properly, you just like loudness (or excessive bass focused quantity), it's the human ear problem.
Edit to add, the sp3k also goes up to freaking 150 volume. It has power, in spades, it just scales it slowly.
You really seem to have a clue and I want to believe you. But why does Chang recommend the M9+ for Storm and not the SP3000? According to him, the SP3000 is not strong enough, but the M9+ is.
Chang wrote this to me personally by e-mail: "As for DAPs, we have found SP3000 to not be very ideal for the STORM due to a combination of tonal character and a lack of power."
No idea what's going on here, but as I wrote earlier: the SP3000 is able to drive my HD800S better (-> dynamics and soundstage) than the CA1000T and ADI 2 Pro SE; both have much, much more power. So I am satisfied.
As mentioned in other comments, the Vrms specs provided by A&K are under no load conditions, so very little can actually be extrapolated from those specifications. Regardless, we believe the quality of power matters more than raw quantity. This is apparent in the HiFI world as well, like with "Naim watts", referring to the driving power of Naim amps despite their lower power output ratings relative to other amps. In the desktop space as well, a Topping A90 is more than powerful enough to drive even the Tungsten, but you won't see many people sticking with an A90 if they're running flagship headphones. Getting a IEM or headphone loud is not the same as driving it well.
This trend is starting to worrying me. My use case for the dap was mostly iem but if the tendency will go this direction there will be only few of them to drive them correctly. The iems nowadays are getting very hard to drive. And I am not talking about planar ones.
I think it's the exact opposite, this year has seen multiple extremely proficient and objectively top of their price bracket while beating out iems, both tonally and technically, well above their cost. Hard to drive = lazy/bad crossover, we are seeing an uptick of manufacturers properly creating impedance match/low impedance, within .1ohm, from 20hz-20khz regularly now and many iems releasing within the next 2 months tout the same tech. It is a must to adopt said technology and create proper crossovers that are efficient. Just like all of our technology, things should be requiring less power given our technological prowess and design capability, not more.
I’m not sure where the notion of a well-designed crossover equaling high sensitivity comes from, but having done the development alongside exchanging notes with many other industry members, the opposite tends to be more true, where extremely easy-to-drive IEMs can be indicative of overly rudimentary crossovers, reduced optimisation as a result of driver stacking for sensitivity, or, in the case of IEMs with ESTs, the ESTs basically having a negligible level of output and being included to add to the spec sheet.
Nice in-betweens can be found, like with the Trailli, for example, but it still sacrifices some sensitivity for optimal EST output and some impedance linearity for sensitivity. Due to size and power constraints, IEM design is a balancing act of optimising trade-offs. With improvements in technology, fewer trade-offs have to be made, but one of the reasons we started on STORM was realising that not much of the industry was really pushing towards that fine balance at the cutting edge.
In terms of design, for STORM in particular, two of our more important priorities were, one, making sure we pushed to the extreme limits of what is currently possible with IEMs, and two, building in a considerable level of future proofing.
To have an IEM really push the limit of what’s currently possible, it means being able to take advantage of any and every source that’s currently available on the market. Be it portable or summit-fi desktop gear, all of our designs thus far have an immense capacity to scale, with several of our clients plugging STORM into desktop stacks optimised for the most challenging headphones, like Susvara, and being quite blown away by the fact that they didn’t hit any scaling ceiling. STORM, with its emphasis on speaker-like staging and staging depth, is also one of the few IEMs well positioned to take full advantage of improvements in DAC upgrades, as one of the key benefits of higher-end DACs is improvement in stage depth and layering, an aspect that many IEMs fail to render properly. As with most devices designed for extreme performance, being at the bleeding edge often means putting up with some inconveniences. A Koenigsegg hypercar doesn't make for a great grocery shopping companion, in most cases a Prius would serve you better, maybe a BMW if you'd like something fancier. But I don't think anyone would expect a Prius or a luxury sedan to outperform the Koenigsegg on a track.
With that being said, we still believe that IEMs are primarily for portable use, so despite designing STORM to have minimal limits to scaling, we also did a lot of testing to ensure that even out of a simple dongle, STORM can be driven to a level that we feel surpasses, or is at least on par, with the very best IEMs out there on the same device. Of course, pairings still come into play, which is why we don’t recommend certain devices, especially those with limited current output. Regardless, there are many options at every tier that we recommend with STORM, even something as simple as the Hiby FC4 for a hundred bucks or so, or more portable devices like the R6Pro2 or Fiio Q15, still drive the STORM to a level of performance that we believe is comfortably ultra-flagship tier. And of course, as you feed it with a better chain, it only keeps getting better.
STORM was also designed to have a certain level of inbuilt future proofing. We believe that if you are spending this much on an ultra-flagship, it makes no sense that it will be made obsolete by the next latest and greatest six months down the line. Designing for this means creating something that is not just extremely technically proficient in the current market but also something that will be able to take advantage of improvements to chain components in the future, be it source, portable amps, cables, or tips. In our case, this means designing a crossover that is an order of magnitude more complex than most designs on the market, implementing a flat impedance design to ensure long-term compatibility with any future amps or amp designs, ensuring no driver is overstressed, and that there is a sufficient level of headroom.
I think just comparing the current crop of DAPs like the DX320max, N30, and even the R6Pro2, just to name a few, to older DAPs from a few years ago, it is evident that we haven’t even gotten close to the limit of what DAPs are capable of, not to mention the improvements in portable amplification as seen in the Tsuranagi and MK 475. Especially since we expect significant improvements in battery technology driven by electrification and the fast-growing wearable technology and portable computing (Steam Deck etc.) markets. Likewise, we expect more compact devices to continue to improve, with recent standouts for size to performance like the R6Pro2 and the M9+ coming to mind, both of which strike a nice balance of sound quality, usability and portability that would be pretty unimaginable form the perspective of someone in the SP1000/DX100/Terra Player era.
With this in mind, we find not pushing the limits to sell a design compromised around the limitations of today, just to sell you an upgrade in a year’s time when the next crop of more efficient and powerful devices appears, to be a disservice to the user. We simply don’t think improvements should be so marginal that flagships can be surpassed by the next crop of releases less than a year later, if peak performance is truly the main priority as many a marketing copy claim. This does not negate the relevance or importance of designs focused on portability, efficiency, and convenience, but I think it would also be sensible to recognise that progress made at the cutting edge also pushes forward the possibilities for designs optimised towards other use cases.