The JVC FD01 with DIY-filters have earned a reputation for being some of the best IEMs for dynamic driver fans. This tutorial is for those who can't (or don't want to) afford the real thing. But it's also for those who love the FD01 and want a cheap beater IEM that sounds very similar to their JVCs. The HSE A2000 are budget IEMs that can be ordered from Amazon Japan and shipped via Amazon Global to more than 65 countries. They typically cost around $30-40 shipped, depending on destination country (which is roughly 1/10th of the JVC FD01). Gunmetal color: https://www.amazon.co.jp/gp/product/B07DHXJ5WF/ Various other colors: https://www.amazon.co.jp/gp/product/B07DHXT9RR/ These are well-made with aluminum housings, flexible cable and proper strain reliefs, but otherwise very basic IEMs. No in-line remote or mic, no case, just the IEMs and three pairs of smallish silicone tips. Large ears may need third party tips in order to get a secure seal. I haven't found much more info on these, other than the fact that they're Hi-Res certified, feature an 8mm graphene coated driver and are supposed to restore true sound. Well, let's take a look at what "true sound" means in this context... hmmm, not all that impressive imho: And sure enough, these sounded decidedly v-shaped and aggressive / sibilant out of the box. As far as I'm concerned, I don't care much for this kind of tuning, so it was either mod or trash, from my pov. Modding instructions: You'll need a 0.5" roll of micropore tape for this mod. If you can't get it locally, you can order it via ebay for little money: https://www.ebay.com/sch/i.html?_fr...acat=0&_odkw=3m+micropore+tape&LH_TitleDesc=0 The other thing you'll need is the twist tie that comes with the IEMs (don't throw it away!). Strip off about one third of its insulation, than cut the bare wire off: With the remaining two thirds of the twist tie, you can make yourself a nice little chin slider: Then use the bare wire to remove the stock mesh. (This mesh has been bugging me for hours on end while trying to find a mod, cause it made micropore damping on top of it very unpredictable): Close up the nozzle with micropore tape, then use the wire to poke a single hole near the edge: Here are the frequency responses for different variants of front damping: stock, full micropore, one hole and two holes. For our purpose of emulating the FD01, I found a single hole to be the best choice. Now it gets a little tricky, because we have to bring down the bass. Unfortunately the A2000 don't have a front vent, so we need to create an air duct underneath the tips as a substitute. Wrap micropore tape tightly around the wire. For a proper duct underneath the stock tips, you'll need 10 windings of tape: Make sure that the result looks like this: Gently pull the micropore roll off the wire, cut it in half and press very firmly to flatten the parts to strips: Then place a strip alongside the nozzle, so that it protrudes at the front. Hold it carefully in place as you mount the silicone tip: Check the result - it should look like this from the front side: Measurement time! Blue is the FR without air duct, green is the new response. You can see that the duct not only brings down the bass, but also has a further smoothing effect on treble: Finally, let's compare the result to the modded JVCs (orange). Lo and behold, a Poor Man's FD01 is born! Disclaimer: A properly modded HSE A2000 is able to closely emulate the FD01 and sound stunningly detailed without treble sharpness (a feat you won't easily find on budget IEMs). Its timbre is on par with the JVC's. However, the FD01 are still a bit better to my ears in overall refinement and transparency, which is hardly surprising given the difference in price. But most importantly, the "air duct mod" is very much dependant on tips, so if you prefer third party tips, you'll have to figure out the number of tape windings (for a neutral bass response) by yourself. Moreover, "burn in" can be real with this mod, particularly if you didn't press hard enough to flatten the micropore strips. So, if you notice the bass becoming stronger after several hours of use, it just means that the strips become flattened and less air can escape through the duct. Eventually they'll settle though, and bass levels will remain constant. On the plus side, you can achieve pretty much any bass level you like with this technique. Want a little more oomph, just use 8 or 9 windings instead of 10. Too much bass? Try 11 or 12 windings for a slight increase in leakage and decrease in bass. Just trust your ears to find out which mod signature suits you best.