With sound pressure level (SPL) at 123 dB and 126 dB respectively for the IE 400 PRO and IE 500 PRO respectively, both models are slightly louder than the IE 40 PRO which has a SPL of 115 dB, taking reference that all three models has an attenuation of external noise amounting up to 26 dB.
Sennheiser’s approach to its series of professional IEMs revolves around the single DD principle using a wideband DD, which the company deems to be superior to other IEMs in the same price range that is based on the Balanced Armature (BA) principle. The company believes that IEMs based on the BA principle would require multiple drivers to reproduce the required frequency range, which may lead to cross-over effects and phase differences between the individual drivers.
On the IE 400 PRO and IE 500 PRO, Sennheiser has implemented a new high-performance DD, which is the product of intensive development work, the 7mm transducer based on TrueResponse, features a system of magnets with three ventilation channels, which significantly reduces the distortion factor. Coupled with a two-chamber absorber in the direction of the ear canal minimises resonance peaks that would otherwise occur naturally.
IE 400 PRO
Like the IE 40 PRO, the IE 400 PRO has a warm sound signature with equally effective insulation from ambient sound, particularly when using the foam ear tips. Coupled with the presence of dynamism and transparency, brings the experience of Sennheiser’s new series of professional IEMs to another level.
The IE 400 PRO exhibits a punchy and natural low-end with a slight emphasis on the sub-bass. Dynamic, clean, and natural, there is depth in the sub-bass presentation with a balanced quality and quantity for almost any music genre. The mid-bass is rich and plays a supporting role in the sub-bass emphasised tuning, detailing a decent enough of presence which would satisfy most sans the bass-heads. It is observed that the IE 400 PRO details sub-bass and mid-bass very accurately, something that I have not heard from a pair of Pro series IEMs at this price point.
There is a lot of similarity between the IE 40 PRO and IE 400 PRO; among them is the delivery of a very succinct mid-range. Balanced, natural, and neutral, there is distinct clarity and transparency with instruments as well as male and female vocals. It also possesses sufficient airiness, which facilitates instrumental and vocal separation well. Although the mid-range delivers what is expected, I can’t help but feel that it somewhat lacks in sound quality when compared to the low-end and the high-end.
At the high-end, the IE 400 PRO is natural and neutral with a reasonable degree of dynamism, allowing the high-end to be pronounced without being overly aggressive. The high-end is enjoyable, especially when you listen to instruments like hi-hats or even cymbal on its own.
The IE 400 PRO has a relatively wide sound stage which is airy and spacious which suffices for accurate imaging of instruments and vocals. I personally would love more depth to the sound stage.
IE 500 PRO
Being the Flagship of Sennheiser’s new series of professional IEMs, the IE 500 PRO has a wider frequency response with 3 dB of SPL as well as a higher sensitivity of 3 dB.
In truth, the IE 500 PRO sounds very similar to the IE 400 PRO; it does, however, address the succinct mid-range found on both the IE 40 PRO and the IE 400 PRO. There is significantly more presence, which brings up the sound quality in entirety and, at the same time, provide a broader and deeper sound stage for a more immersive experience.