KZ introduced the new ES4 in-ear headphones a few days ago: they are an evolution of the ES3 which seems to combine the ZS10’s design with the ES3’s simpler components. They are built around one dynamic driver and one balanced armature in a classic hybrid approach.
In terms of design, the ES4 seems to be directly related to the ZS10: a transparent plastic shell covers a PCB and the drivers, that are therefore exposed to sight. The shape is also similar, which leads me to think it could be derived from the ZS10 project, with simpler components to drive down the price.
The dynamic driver has a 10 mm diameter and KZ says there is a layer of graphene over it – I highly doubt it, since graphene is still not suitable for industrial applications and is confined to research labs around the world. It seems KZ is using the same balanced armature as that on the ES3: the Knowles 30095. They say it is a custom unit and I hope so, as the entry for the 30095 on DigiKey reports a frequency response of 120 – 7,400 Hz, which appears quite disappointing.
As it is customary for KZ’s latest earphones, the cable is detachable and uses two 0.75 mm pins – so it is compatible with cables such as the AK Audio 4-core 7N copper cable or the Yinyoo 8-core SPC cable. The company claims that the receptacle can last up to 10,000 plug-unplug actions, which would imply a long life for the earphones.
I will receive a unit in the coming weeks and will publish a review soon after.
AK Audio sells the ES4 and agreed to discount them for Soundphile Review’s readers: you can use the code “SoundphileReview” to bring the price down to $15 for a unit with microphone and $14 for a unit without microphone. You can find the item here. In order to use the code, you have to select the “use another payment method” in the checkout process and write the code in the message field, then complete the order but don’t pay just yet. The people at AK Audio will then manually adjust the price.