Acrylic Vs Soft Silicone: The Big Debate! Which is the Right Custom In Ear Monitor Material for you?
- Miles Dakin
- Mar 4, 2024
- 6 min read
Updated: 6 days ago
Investing in a new set of Custom in Ear Monitors is a big thing for 99% of people.
It can feel daunting and expensive — especially when transitioning from cheaper Universal models. But there is one massive, misunderstood choice many musicians face, and it's surrounded by misconceptions (with strong opinions on both sides!)
It's one of the most common questions I get — usually the first thing people ask when they see my own custom IEMs.
People often say something like:
"So you've got both... which is better —a soft shell or hard shell Custom In Ear Monitor?
Surely a softer one is more comfortable?
How am I meant to know the difference, because they’re custom?
What are the actual real-world differences for you as a gigging musician or engineer?"
Luckily, if those are the kind of questions you've been asking yourself... the answer is actually pretty easy. I’ll stick my neck out and say that with these 5 simple considerations, this is going to help definitively answer which is best for you: Hard Acrylic or Soft Silicone In Ear Monitors.
Lets dive in...
Firstly, let's understand the materials... and your ear!
Before delving into the comparison, it's essential to understand the characteristics of each material. Your ear is flexible, and that flexibility extends into the ear canal. Whenever you move your jaw, your ear canal warps and changes shape slightly. This matters for fit — especially if you’re a vocalist or play woodwind or brass, where your jaw is often in motion or not in a relaxed position.
Acrylic IEMs are rigid and designed to provide a snug fit in the ear canal — typically shaped as a ‘best fit’ based on your ear impression. For 64 Audio or FiR Audio, we'll always use a 1inch bite block to grab an open jaw impression, ensuring a consistent seal and isolation whether your mouth is open or closed.
On the other hand, soft silicone IEMs are flexible, and the canal tip (the bit going into your ear) flexes slightly to adapt with your ear canal, providing a more natural feel and enhanced comfort. With these, an open jaw impression is usually only needed if you're a vocalist — mine are closed jaw, and they still seal even when I hit those face-melting falsettos!
So with that bit of context, which is best for you?
Consideration 1: Comfort & Time
Comfort plays a crucial role with Custom In Ears, especially during extended wear — and this is where one of the first misconceptions shows up! Acrylic IEMs, while rigid, are meticulously crafted for comfort — smooth and well-fitted enough to wear for hours without issue. I regularly perform for several hours and still wear my 64 Audio A18t's during pack down (around 4 hours) and they're really comfortable!
However, silicone IEMs being flexible and softer, make them ideal for prolonged use. They also warm slightly to your body temperature during a set, becoming even more pliable —which adds to the comfort! So if you're wearing IEMs up to 4–5 hours at a time, either is fine. If you're using them for a particularly extended period —like stage managing or running communication lines (comms) for 5+ hours, soft silicone is probably the best way to go.
Consideration 2: Build Quality & Durability
In terms of build quality, both acrylic and silicone In Ear Monitors are excellent — both designed with durability in mind, especially for musicians on the road. Reliability is key after all!
One main difference, however, is how the shells are reinforced. Soft silicone customs are actually solid, with drivers set inside them. This makes them impact-absorbent, highly durable, and able to withstand accidental drops (or bounces off guitars) quite nicely.
Acrylic IEMs are the opposite. Being a hard 3D-printed material, they're hollow. So, while inherently more rigid, but use thick reinforced walls to enhance durability — making them equally suitable for rigorous use. FIR Audio actually has the thickest acrylic shells on the market, meaning they are pretty bombproof!
Consideration 3: Technology & Customisation
Acrylic and silicone IEMs offer distinct advantages in terms of technology and customisation, but in this case, we think there's a clear winner!
Soft silicone custom In Ear Monitors, being solid, tend to be a bit more limited in customisation options. However, ACS have learnt over the years how the material reacts, and uses the interaction between the speaker drivers inside and their silicone housing to deliver excellent frequency extension and resonance — all thanks to their unique material properties.
Acrylic IEMs, however, have a simpler internal structure, which allows for more flexibility in advanced customisation (you’ve probably seen the weird and wonderful designs people use to express themselves on stage!)
But if it's tech you love, then acrylic wins here too. Due to the hollow internals and separate faceplate, manufacturers like FiR Audio have capitalised on the material's strength to integrate features like bespoke-tuned internal sound chambers and reinforced pressure relief modules — as well as intricate faceplate designs.
(Shoutout to FiR Audio for including all customisation in the price of the Custom In Ear Monitors - we love that!)
Consideration 4: Any possible negatives?
Each material has its drawbacks. Silicone IEMs may experience weaker points around cable sockets due to their flexibility, potentially leading to stress on internal wiring if you ever needed to replace the cable. That said, I’ve never had that issue with my Evolves — and I rarely need to take the cable off anyway.
On the other hand, acrylic IEMs are sturdy — but because they’re hollow, they can crack or shatter under extreme pressure. I once watched as my TM's Ultimate Ears fell off their cable backstage and scuttled into the darkness — only to hear a small 'crack' followed by an annoyed shout as it disappeared under his shoe...
Still, with proper care, both types of IEMs can provide years of reliable performance!
Consideration 5: Sound Quality of the Custom In Ear Monitor?
Ultimately, sound quality is paramount — it’s why we’re all here. Both acrylic and silicone IEMs offer exceptional audio performance, — but each brand brings its own ‘house sound’ to the table. As I always tell clients: personal preference plays a significant role — and honestly, there is no right or wrong.
I always recommend you experience and Demo both types of IEMs and get them in your hands — that's the best way to know what feels and sounds right.
We run demos all the time and aim to stay transparent, challenge preconceptions, and help find what's best for you.
Book in for a demo to trial the different types here.
So there you have it...
The choice between acrylic and silicone custom in-ear monitors is yours, and and ultimately comes down to personal preference and specific needs. By considering factors such as comfort, durability, customisation options, and sound quality, you can make an informed decision that aligns with your needs and preferences.
Whether you opt for the flexibility of silicone or the creative freedom of acrylic, investing in custom IEMs guarantees a tailored listening experience that will absolutely enhance your performance on stage. (If you can, try and get both types in your hands before deciding.)
At DCA, we understand how important it is to find the perfect pair of customs — and we’d love to help. With our extensive range of demo units and firsthand experience using them live, we're here to help you navigate the decision-making process and find the ideal solution for your setup.
If you’re considering customs or need advice, feel free to reach out — we’d be happy to help.
Thanks for reading - Miles (Founder DCA)
