In recent years, the humble earbud has fallen out of fashion in favour of the headphone—and with good reason. Headphones offer a sizeable upgrade over their compact counterparts, which often come bundled with smartphones and music players and offer miserable, if at least listenable, sound quality. Good headphones have more bass (a typical inadequacy of cheap earbuds), are more comfortable, block out more exterior noise thanks to heavily padded ear cups, and in some cases they're even more of a fashion statement than Apple's ubiquitous EarPods. Some might even be wireless.

The tradeoff, though, is that headphones are big. For those that value discretion, headphones, even compact ones, are too bulky to be manageable on the go. That's not to mention their impracticality for fitness enthusiasts, for whom earbuds tend to be the preferred option. Traditionally, the upgrade path for earbuds has been towards sets like Sennheiser's CX300 II. These offer decent sound quality and the addition of silicone sleeves, which sit inside the ear rather than outside of it, helping to isolate outside noise, provide better bass, and ensure a more stable fit.

Noise Reduction Rating Decibullz quotes a Noise Reduction Rating (NRR) for its Decibullz headphones. Decibullz quotes a Noise Reduction Rating (NRR) for its Decibullz headphones. This is a unit of measurement typically used for commercial earplugs and ear defenders in North America. To determine the actual amount of decibel deduction applied when measured in dBA, you take the NRR number, subtract seven, and then divide by two. For example, if you're at a concert with a noise level of 100dB and you're wearing a earplugs protector with an NRR of 33, your new level of noise exposure would be 87dB. For reference, anything from 60db to 80db is considered "very loud," while 90db to 110db is "extremely loud." Anything above that can cause hearing damage with prolonged exposure.

But even the silicone sleeve has its limits. Until recently, the best fit for consumers has been via foam tips, which are squished before being inserted into the ear where they expand to form a surprisingly solid seal. As someone that's been using Comply-branded foam tips for years with a set of Ultimate Ears' excellent UE900 earphones—which boast four balanced armature drivers, two for bass, and one each for middle and treble—I can confirm they make a huge difference to comfort and noise isolation, provided they're used with a good set of headphones to begin with.

Now, there's another option. Custom fit earphones, where the some or all of the earphone is moulded to fit your ear exactly, have undergone something of a resurgence. Traditionally worn by musicians, new materials and technologies have given custom fit earphones a new lease of life as a viable option for consumers that demand the most comfortable fit possible. Custom fit earphones have historically demanded a visit to an audiologist to create moulds (which is an interesting experience to say the least), but the arrival of 3D scanners, 3D printing, and new materials mean moulds can be made quicker and cheaper, even at home.

The question is, do custom fit earphones offer a tangible advantage over foam tips, which cost a mere £12 for a set of three? And can the cheaper options compete with a traditional audiologist mould?

To find out I tried three different types of custom fit earphones: a mould-at-home set by Decibullz; a 3D scanner-based soft silicone tip by UK startup Snugs; and a classic hard-plastic fully-custom in-ear monitor by Ultimate Ears. These are by no means the only options out there—both UK-based Earcandi and Kickstarter darling Revols offer their own takes on the mould-at-home concept—but are representative of the main types of mould (bar sticking some Sugru in your ears, but that's definitely not recommended).

Decibullz

The Decibullz (buy here) are the cheapest option of the three, retailing for just shy of $60/£50. Like its competitor Earcandi, the Decibullz aren't a fully custom solution, but rather a hybrid solution that uses a standard silicone tip for the inner ear coupled with a mouldable hard plastic for the outer ear. They're the least intrusive of all the options, and feel just like a set of standard silicone-tipped earbuds when used—with the added benefit of a more secure seal (in theory at least).

Moulding the Decibullz is an odd process best done one ear at a time. There are two plastic inserts vaguely shaped like the outer ear, which sit between the earphones and the silicone tip. Placed in hot water, the inserts become pliable, after which you attach them to the earphones, put on a silicone tip (several sizes are included), and slip the whole lot into your ear for moulding. There's no real trick to moulding other than to just sort of mush everything around until it fills your outer ear, before smoothing everything over with a finger. Using a mirror definitely helps.

Mark Walton

Mark Walton

Mark Walton

Mark Walton

After five minutes or so the inserts begin to harden. You can then take them out and leave them to cure fully, which takes around another 10 minutes. What you're left with is a strange looking lump of plastic that does a surprisingly good job of isolating outside noise (Decibullz claims a Noise Reduction Rating of 31). Versus standard silicone tips there's a tangible reduction of outside noise, but how well they work depends on the quality of your moulding. It took two attempts before I was satisfied with the isolation offered (the inserts can be remoulded several times), and even then it's a close call between the far simpler foam tips and the Decibullz.

Perhaps the biggest problem with the Decibullz is the sound quality. It's not awful, but $60/£40 can buy you earphones with richer mids and highs, instead of the overwrought bass of the Decibullz. Unfortunately, you can't buy the inserts to use on your own headphones either, which is an odd omission. The best use for the Decibullz' remouldable inserts are for making cheap custom earplugs, which it sells for around $26/£20 online.

Decibullz verdict: OK, but foam tips remain the better (and cheaper) option.

Listing image by Mark Walton