x HBB

The 7Hz Legato has the *most* bass, but most people EQ it because out of the box it sounds pretty muddy. I returned mine for that reason. If you want to EQ then the Aoshida E20 is a cheaper option, although the build quality is quite cheap compared to the Legato. Still, could be a killer combination with a Qudelix 5K if that fits in budget (or the Legato as well but that's getting even more expensive). In that price range the Aful Explorer probably has the best quality bass out of the box. Also, one of my favourite IEMs is the QKZ HBB, which is only $15. It's not as resolving as the Explorer, but I prefer it because it has more natural-sounding tonality. Vocals on the explorer can sound a bit muffled and sibilant at the same time, although it's an excellent IEM in every way other than that. Also the Ikko OH300 which is like a more vocal-forward version of the HBB, with exceptional imaging/layering - and it's only $50 (maybe 40 if you can find it on sale, but they all sold out for several months and I'm not sure if it's back on Aliexpress yet, just the Ikko site at RRP). In terms of ergonomics the Aful is miles ahead of the rest. The Aoshida is probably the 2nd most comfortable. The Legato is nicely built but it's quite large. The HBB and the OH300 are both a bit chonky and cheap feeling, but still fairly comfortable in the ear - they just stick out a bit (don't feel as large as the Legato but all are quite wide).

The main difficulty is finding one you like. I also have a $15 favourite, which is the QKZ HBB (IDK about as an only IEM, but it's one of my favourites out of a collection of about 60 now). But I don't much like the Zero 2. So YMMV. Same thing applies regardless of price - what sounds natural to one person might sound odd to someone else, because everyone has a different HRTF. Spending more isn't automatically better, although you do usually get better drivers (up to a point).

The biggest problem with these is that the nozzles are absolutely massive. One of the most over-recommended IEMs (along with the Red) given that most people will find them somewhat uncomfortable and potential painful in many cases. The tuning and technicalities are just OK in the current market. Send them back and get something else. The question then is what to get. You're used to a very bassy signature so you could go for something similar. The QKZ HBB is really good and has a warm/bassy signature, so that might be a bit closer to what you're used to and should be an upgrade in terms of sound quality (they're one of my favourite IEMs at any price and they're only $15). Or you can go with a different tuning, but bear in mind that you'll want to give it maybe a week of not listening to anything else to let your brain adjust. If you want something more "clean" sounding but still with a decent amount of bass (won't be as much as the Sonys) then maybe try the Kefine Klean, or if you want to spend more there's the Aful Explorer (although I personally find vocals don't sound great on that one, despite everything else about it being really good). I wouldn't spend time trying to adjust to the Zeroes though, because they'll just continue to hurt your ears and could potentially cause an ear infection. Don't try to struggle through if they are hurting your ear canals. I've done that and it takes weeks of not listening to IEMs at all to recover from the ear canal damage.

You could just add a 10dB bass shelf with EQ to any of the IEMs you already have. Most of the cheap basshead IEMs sound pretty crap without EQ anyway (including the Legato, it sounds pretty muddy without EQ). The QKZ HBB (not the Hades) sounds good without EQ, but it's not *that* much bassier than the Explorer.

Ikko OH10 if you can find one for sale anywhere. They're still making them, but only in smallish batches, so there's often no stock. There's also the OH10S which is apparently tuned almost identically (I haven't heard it because there didn't seem to be much point in buying nearly identical IEM) with the main difference being the faceplate design. There are a few newer hybrids that are apparently quite good as well such as the Ziigaat Doscinco, but I haven't heard it myself. Audio Amigo has a good roundup of all the Ziigaats which is worth watching, as there's a ridiculous number of them, all with fairly similar tunings. Might be slightly outside your budget unless there's a sale though (which there very often is). On the cheaper side the Aful Explorer isn't bad either, although it's mostly a softer, very warm tuning and doesn't have the same sort of weighty bass punch as the OH10. Also I find vocals on the Explorer very sibilant, but not everyone seems to get that problem. Personally with the exception of build quality & comfort, I actually prefer the QKZ HBB over the Explorer and it's warmer & bassier too. And it's only $15. Out of the 3, the HBB is the best for volume scaling before the treble gets too intense (without EQ). The Explorer is a bit more resolving though.

Maybe the Truthear Pure, but if you didn't find the Explorer comfortable, you'll probably find the Pure quite uncomfortable. If you can still find one (it's discontinued), you also might like the Tangzu FuDu Verse 1, which is really small & comfortable. The tuning is actually quite similar to the Pure in a lot of ways. If you want to try something cheap-but-good, give the QKZ HBB a try and don't be too put off by the $15 price. It does have slightly pushed back vocals, but I find it sounds more natural than the Explorer, which comes across as both veiled and sibilant at the same time to me. They're slightly bulky, but I find them surprisingly comfortable anyway, as long as I'm not trying to wear them while lying on my side or something. These are my "wear all day" IEMs, especially for background listening, as they are very non-fatiguing at lower volume (or they can be bass monsters if you crank it up, but don't damage your hearing).

Stick to 1DDs (single dynamic driver) to run off old hardware, because they won't change frequency response if the headphone amp isn't great, and while Apple stuff is usually better, older stuff isn't always that great. For around $5 on sale you can get the KZ EDC Pro, although recently I have been preferring the KZ Gale (the EDC Pro is bassier, the Gale sounds more resolving). Both come with crappy cables so you'd probably want to upgrade that. The QKZ T1 is good and cheap. Fits the Gale but not the EDC Pro. For the EDC Pro, basically any KBear cable (8-core or 16-core, the cheapy 4-core ones are passable, but nowhere near as good) with a standard 2-pin connector. There's also the incredibly over-hyped GK Kunten (also made by KZ) but while people were getting those on sale for around $2 (and that's why there's so much hype) the price has gone back up to normal now, so whether or not you can find one under $10 will depend what regional offers are running. I'd say they're perform about the same level as the Gale, so look for whichever one is cheaper or you prefer in terms of looks. The tuning is slightly different, but they're nearly identical. Both are QDC so both will work with the QKZ T1 cable. There's also the KZ ZVX Pro which I haven't heard myself, but apparently is the exactly same IEM as the Kunten (same driver, same tuning), just in a slightly higher quality all-metal shell, and now that the initial sales have passed, it's usually cheaper. So that's another potentially good option. QKZ T1 cable again. Unfortunately under $10 pretty much all your options are made by KZ, who are a slightly dodgy company, but their QC has improved a lot in the past couple of years. If you prefer a bassier sound and can stretch to around $15 or so, the QKZ HBB is excellent (QKZ are not related to KZ). Unfortunately it also comes with a pretty crappy cable, and once again the QKZ T1 is the solution.

QKZ HBB. Nothing else is tuned quite like it. To give a more expensive set with similar-ish tuning that they sound better than: the Aful Explorer. Although the Explorer is better in a lot of ways (fit is better, resolution is better), vocals sound better on the HBB. Sibilance on the Explorer bothers me, so out of the two, the HBB is the one I'll normally listen to. Next to better, but quite differently tuned IEMs like the Simgot EA1000, they still hold their own as something completely different. They make a good complementary set as part of a collection. Whereas I have a bunch of other cheap IEMs that I rarely actually listen to, because they don't do anything unique. Another cheap pair that I do listen to a lot is the Ikko OH300, which has largely replaced the Letshuoer S08 for if I'm in the mood to listen to something like that. The S08 is pretty unique and I wouldn't say the OH300 is flat out better, but it does have better bass. The OH300 sits in a similar category to the HBB and they have quite similar-sounding bass. But whereas the HBB is quite relaxed, with pushed back vocals, the OH300 is quite vocal-forward. The OH300 also has exceptional imaging/layering, which is the other reason why it competes with the S08. The S08 is also exceptional in that regard, but incredibly tip-sensitive, and the S08 has a really tiny soundstage (which is a good thing, in the sense that it's very unique).

The QKZ HBB (the one *just* called that, not the Hades) is an excellent IEM with a ton of bass. The bass peaks around 30Hz and slightly starts to roll off towards 20Hz, but it has so much bass already that a tiny bit of rolloff isn't really noticeable & helps it not sound muddy. If you want something with even more sub-bass then there's the KBear Rosefinch, but it's not as well-tuned as the HBB overall. I'm not sure how much of a difference there would be between the two for bass monitoring, but the Rosefinch does have a steeper bass rise & is extremely v-shaped (the HBB is more warm-tilted than v-shaped). I suspect it would mess with the tone a bit because there's such a huge dip at 1kHz followed by a steep eargain & a lot of treble. I don't like it for music, because it has a huge treble peak (somewhere around 8-10kHz) that gets quite stabby when you turn the volume up, but if you're only monitoring the bass, it probably doesn't produce much around that frequency. If you're listening to a mix with other stuff, it could be quite distracting.