IEM ear tips: the free upgrade that beats most cable swaps

I had a listener email me last month convinced her new IEMs were "missing bass" compared to the demo pair she'd tried at a shop on Chapel Street. Same model, same source, same file. Turned out she'd swapped the stock silicone tips for a set of foam tips two sizes too small, because the box they came in looked nicer than the little baggie of spares. That's the whole article, really. Ear tips are the single biggest variable in how an in-ear monitor sounds, and almost nobody treats them like a variable at all.

I've spent a fair chunk of the last few years testing IEMs for this masthead, and the pattern holds every time: change the tip, change the sound, sometimes more dramatically than swapping the whole cable or even the source amp. Yet most buyers treat tips as an afterthought, something you pick based on whatever falls out of the box first, or whatever colour matches the shell. That's backwards. Tip selection deserves the same attention as amp matching, and it costs a fraction as much to get right.

Why the seal is doing more work than the driver

An IEM is not a miniature open-back headphone. It's closer to a tiny loudspeaker in a sealed enclosure, where your ear canal is part of that enclosure. The seal formed between the tip and your canal wall is what allows the driver to develop bass pressure at all. Break that seal, even slightly, and you don't get "less bass" in some vague sense, you get almost none, because low frequencies rely entirely on that acoustic coupling to build up in the small volume of air between the tip and your eardrum.

This is why a tip that's a half-size too small feels comfortable but sounds thin and hollow. It's also why a tip that's slightly too large, forcing an incomplete or strained seal, does the same thing for a different reason. There's a real analogy here to something I wrote about turntables: it's the last half-millimetre that matters more than the cartridge, and with IEMs it's genuinely true in a physical sense, not just a metaphorical one. A half-millimetre of tip diameter is the difference between a seal and a leak.

Most manufacturers ship three to five silicone tip sizes for exactly this reason, and most buyers use whichever one goes in without discomfort rather than testing all of them against a familiar track. I'd encourage doing the boring thing: sit down with a bass-heavy reference track you know well, cycle through every size in the box, and listen for the point where bass suddenly locks in and background hiss (if there is any) drops slightly. That drop in perceived noise floor is often the tell that you've found the real seal, not just a comfortable fit.

Foam versus silicone: not just a comfort choice

Foam tips, the compressible memory-foam type popularised by Comply, seal differently to silicone. You compress them, insert, and they expand slowly to match your canal shape. Because they conform rather than relying on a fixed geometry, they tend to give a more consistent seal across a wider range of canal shapes, which is partly why they're popular with musicians using stage monitors for hours at a time.

Acoustically, foam tends to soften the treble slightly and can smooth over some sibilance, which is genuinely useful on IEMs that run bright, but it also slightly dulls the leading edge of transients compared with a well-fitted silicone tip. I hear this most clearly on brushed cymbals and vocal sibilants; silicone lets more of the initial attack through, foam rounds it. Neither is "correct". It's a genuine tonal choice, not just a comfort one, and I'd argue reviewers who only ever test with stock silicone are missing part of the picture on any given IEM's real character.

The tradeoff with foam is durability and hygiene. They compress permanently over weeks of use, absorb ear wax more readily, and need replacing more often than silicone, which just needs a wipe. If you're commuting on the Frankston line every day with the same pair, budget for replacement foam tips every couple of months if you're using them daily.

Bore diameter and the treble tilt nobody mentions

This is the part that even fairly serious enthusiasts miss. The internal bore diameter of a tip, the width of the tube the sound actually travels through, changes the frequency response independent of the seal quality. A narrower bore tends to lift the mid-bass and lower treble slightly while damping the very top end. A wider bore opens up perceived treble extension and can make an IEM sound more "open" and airy, at the cost of sometimes exaggerating any existing peaks in the driver's natural response.

This is exactly why swapping a stock tip for a third-party tip with a wider or narrower bore, even in the same silicone material and the same size, can change an IEM's entire tonal balance. Brands selling aftermarket tips aren't always transparent about bore diameter, which makes this a bit of trial and error, but it explains a phenomenon I see reported constantly online: someone claims a specific aftermarket tip "fixed" the treble on a particular IEM. They're usually not imagining it. They've changed the acoustic waveguide, not just the fit.

If an IEM sounds a touch hot or peaky in the treble to you but you otherwise like it, trying a narrower-bore tip before assuming the driver itself is the problem is worth the ten minutes it takes. Conversely, if something sounds closed-in and congested, a wider bore is the cheap experiment before you start blaming the source.

Depth of insertion changes more than you'd think

Shallow-fit tips sit near the entrance of the canal; deep-fit tips push further in, closer to the eardrum. Manufacturers design around a target insertion depth, and departing from it changes both the tonal balance and the effective seal. Push a shallow-fit IEM in too far and the bass response can actually shift because the acoustic cavity volume between driver and eardrum has changed. Insertion depth also affects perceived soundstage: shallower fits generally produce a slightly wider, more diffuse image, deeper fits collapse the stage a little but often tighten bass and improve isolation.

I'll admit I got this wrong for years, assuming a "good seal" was a single fixed target rather than something with a correct depth range specific to each shell design. Custom-moulded IEMs solve this by locking in one depth permanently via an impression of your ear, which is part of why serious stage performers use them, but for universal-fit IEMs bought off the shelf, it's worth actually reading the manufacturer's guidance on intended insertion depth rather than assuming deeper is always better isolation and therefore always better.

What this means if you're building a desktop or portable rig

If you're pairing IEMs with a desktop DAC/amp or a portable dongle, tip fit matters more than most of the amping decisions people obsess over. A well-driven IEM with a poor seal will sound worse than a poorly-driven IEM with a perfect one, because you're fighting bass roll-off no amplifier can fix; it's not a power or distortion problem, it's an acoustic sealing problem upstream of the electronics entirely. This is one of the few places in personal audio where the free or near-free fix genuinely outperforms the expensive one.

That said, once the seal is sorted, source quality does matter, and if you're running IEMs off a laptop or phone headphone jack, a proper external DAC/amp is still worth it for headroom and noise floor, particularly with lower-impedance in-ears that are more sensitive to hiss from noisy onboard audio. Our rundown of the best desktop DAC/amps covers a few options that pair well with sensitive IEMs without adding audible noise. For anyone building a full setup from scratch, I'd still say tips first, source second; it's the same spending logic Dave applies to speaker systems, sort the fundamentals before you chase the marginal gains, and our piece on building a headphone system in order makes a similar case for over-ears.

A practical way to actually test this

Skip the golden-ear mysticism and do this properly: pick one track you know intimately, ideally something with sustained low bass and a bit of cymbal work, Steely Dan's "Aja" or similar is fine. Insert the stock tip at the manufacturer's suggested size, seat it, wiggle your jaw once (chewing motion breaks a bad seal immediately, which is diagnostic in itself), and listen for thirty seconds. Then try one size up, one size down, and if you own them, a foam alternative. Note not just "more bass" or "less bass" but where the transition happens, does the seal snap in cleanly or gradually. A good seal has an obvious threshold; you'll hear the bass "arrive" rather than slowly increase.

The Bluetooth SIG's own guidance on wireless earbud design touches on acoustic sealing as a factor in both sound quality and background noise attenuation, and it's a useful reminder that this isn't audiophile mythology, it's basic acoustics that applies whether your IEMs cost forty dollars or four thousand. The AES has published research on ear canal acoustics that goes considerably deeper than I have room for here, for anyone who wants the full physics.

None of this requires spending money you don't have to spend. Most IEMs already ship with enough tip variety to get most of the way there, and a multi-pack of aftermarket silicone or foam tips costs less than a single decent cable. It's the cheapest, fastest, most reliably audible upgrade in this hobby, and I still reckon it's the most skipped step in every unboxing video I watch.

— Eleanor Shaw, Headphones & Personal Audio Editor