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You can't buy these in-ear monitors in shops, as each pair is custom-made — but if you need outstanding comfort and noise rejection, the extra time and money might just be worth it!

Buying a set of ACS in-ear monitors is a two-step process, which could potentially be seen as discouraging to the modern shopper accustomed to high-street availability or Internet click and credit. First, you make an appointment to have a mould taken of your ear canals, and then you wait for the earpieces to be custom manufactured for your ears.

Initially, an audiologist will check you have no problems such as excessive wax build-up or infection. Then a small piece of foam is placed inside the canal. The rest of the ear canal is then filled by syringe with something not dissimilar to bathroom sealant. This fills the ear, effectively sealing you from the world of sound — a feeling I have never been entirely pleased by! The compound then hardens and is carefully removed, leaving a detailed impression of your ear canal, from which the custom moulds are created. Everyone's ears are different, and only by taking these impressions can comfortable, close-fitting moulds be made.

The blank moulds are then sent off to ACS in Banbury, where the impressions are reproduced in medical-grade silicon, and then hand-fitted with three balanced-armature transducers. Finally, they are boxed up and sent on to the customer, in this case me! But was it worth the wait — and the price?

I took delivery of mine while engineering at a show in London. It was a hectic day, so I had no time to do anything but open the box, admire the leatherette container and extra-soft carrying pouch, and check out the pristine mouldings. It wasn't until next day's train journey home that I actually got a chance to put them in my ears!

The Train Test

Trains may not seem an ideal environment, but I do an increasing amount of my critical listening on them. The T1s' ability to cut out ambient noise would be tested well here, but first I had to get used to the custom moulds (I have been using in-ear monitors for over 15 years now, and they all take a bit of getting used to).

So how do they sound? Well, on plugging them into my iPhone and choosing the first track at random (Stevie Wonder's 'Sir Duke'), I was smiling within seconds. The sound was crisp but not overly bright, with plenty of detail as well as good low-end extension — in fact, probably the best low end I have ever had from a device such as this. The bass does seem to be very dependent on getting a close fit, however, and it helps to practise putting the T1s in in front of a mirror, as the first couple of times it can be a bit tricky. Fortunately, they are labelled left and right using coloured dots, which helps!

I then decided to push the low end a bit harder with a bit of Deadmau5 (this time a CD-quality file), and they didn't disappoint. The low end was very full — a fair representation of what I expected to hear, as I have been using Deadmau5 to test numerous sound systems recently.

Another track I've been using for systems testing for many years is 'The Horses' by Rickie Lee Jones: it is well recorded and mastered, and I find it very useful for highlighting any inherent flaws in a system. The T1s held up, and though I found them a little bright, the mid-range was excellent and revealing in the crucial vocal area.

A big question for me, though, is 'Can I mix with them?' I spend a lot of time travelling, and though I wouldn't try to mix only on headphones or earbuds, I do a lot of the grind work of mixing (cleaning up tracks, editing, checking takes, and so on) on the move. I had previously always used my Sennheiser HD25 headphones for this, but started experimenting with the ACS T1s, and the detail they are able to provide is excellent for pinpointing problems. The are very accurate to work with and surprisingly unflattering — I found them in some (good!) ways to be similar to working with NS10s. I always check mixes on my main monitors, but those I did while using the T1s needed little in the way of re-jigging to transfer well.

However, most purchasers will be buying the T1s for in-ear monitoring use on stage, of course, and for this I believe they are exceptional. In particular, I found that their rejection of stage noise (once I had them seated correctly) was excellent, and they are also very detailed and surprisingly full-sounding.


Similar devices available from Ultimate Ears, and many manufacturers offer generic ear buds at a lot lower cost, but without the custom fit.


  • Great isolation.
  • Comfortable to wear.
  • Consistent sound.


  • Require a custom mould so only suitable for one user.
  • Expensive.


The T1s offer excellent rejection of external noise, and provide a highly accurate, detailed and analytical sound.


£649 including VAT.

ACS +44 (0)1295 266665.


ACS USA +1 516 233 2813.