ALPHA&DELTA KS1 Review: Incredible construction, decent warm sound



SOUND: 7/10
VALUE: 7.5/10

THE PLUS: Excellent construction, Generous accessories, well balanced U shape sound, smooth tonality, Ultra-comfortable, Great noise isolation
THE SO-SO: Average Resolution-Definition, poor imaging, poor bass control-separation, recessed mids, boring treble

ALPHA&DELTA isn’t an audio company that launches new IEM model very often, so when they do it’s always a big event and that even if this company is rather unknow by most westerners. On the other hand, a lot of audiophiles do know this company for its excellent D6 earphones, which is their best achievement yet, followed by the flagship KS3 launch one year ago.

Today I will review the little brother of KS3, the ultra-budget universal custom KS1. Priced at only 45$, the KS1 uses an 8mm dual magnetic graphene driver and has an incredible construction made of resin plastic like the flagship KS3.

To have this type of high-end construction for such a little price is quite impressive to say the least, now let’s see in this review if the sound it delivers worth your attention.

The KS1 can be bought directly from official ALPHA&DELTA WEBSITE or from Lend me ur ears STORE. (use code ”ad20” to get extra 20% off KS1 on Lend me Ur ears)


  • Driver Unit: 8mm graphene micro driver
  • Impedance: 16 ohm
  • Rated power: 1mW
  • Frequency response: 10 Hz- 20 Khz
  • Speaker sensitity : 105 +/- db/mW
  • Cord Length: 1.2m silver plated copper cable
  • Plug: 3.5mm


The product is nicely presented and has a good amount of accessories, which is very impressive for a 40$ IEM and always appreciates. The 4 cores SPC cable is of good enough quality, and do not justify to be fastly upgraded. We have a good amount of silicone ear tips (6 pairs) and a pair of nice memory foams ear tips. As well, a cute carrying pouch is included.  Nice!


The construction is incredible for the price, I’m a big fan of full resin body because of the smoothness of material and the KS1 has this type of housing in an even smaller factor. The housing is about 2 times smaller than average universal customs, resin plastic is thick and super slippy, the 2pin connector is embedded in plastic and promise long durability. The nozzle is made of aluminum and solidly stuck into the housing. Universal custom shape is organically angular without any hard edge.

These offer supreme COMFORT, and due to small size, the KS1 will fit any type of ears. They are among the most comfortable IEM I own, and I can even sleep with them without any discomfort. This housing is the exact same one used for DUNU DM-480 but with different color and backplate (and lower price).

ISOLATION is excellent, the KS1 do not have venting hole, so you have total passive noise canceling, if you use foam tips, this will act like earplugs. Sound leakage is mostly nonexistent.

DRIVEABILITY is easy, at 16ohm, these will not benefit from a portable amp, still, due to the warm sound nature of KS1, I suggest using a very clear audio source, even a cold analytical one like the Xduoo X20 help for sharper sound articulation.



The KS1 is a warm U shape sounding earphones with smooth, slightly liquid timbre and boosted mid-bass. Mid-range is relaxed, but clear enough, and treble is detailed but never aggressive, with softened upper highs. This type of signature is versatile without excelling at anything. It’s a cozy sound, tuned for fun laid back listening were more of energy came from the bass thump. You cannot really dislike the KS1, you feel in familiar territory, and it’s a well rounded one, in the sense you neither have upper mids sibilance or unbalanced treble spike with the KS1, it’s a sound that is muscular in bass but delicate in tonality.

SOUNDSTAGE is just above average, especially in term of wideness and tallness, for deepness, bass stole the much-needed silence.

IMAGING is not very precise, even if you got some transparency, the layering feel compressed and instrument separation lack space. Spatiality lack left and right visibility, which makes instrumentation feel all stuck in the middle of the scene in front of you.

BASS is very warm, timbre is near texture less, as well, it’s notably boosted from sub to mids bass, which gives weighty slam, but the impact isn’t neither fast or hard thumping, as if the bass lack a bit of edge. The extension is a little muffled, with perhaps a little roll-off beginning in 40hz section, because acoustic bass does not extend naturally and lacks transparency. More quantity than quality here, which is no problem for POP music, but if you want well separated, clean bass, the KS1 act here as a typical entry-level dynamic driver that offers a mixed up bass response warming whole sound.

MIDS are slightly recessed, smooth in timbre, soft in edge and attack, warm in tonality. They are presented in a centered intimate way and do not offer a high level of separation. The transition from low to mids is contrasted by slow bass response that affects macro resolution. Vocal has natural timbre enough, but lacks texture and clarity, making them a little thin sounding and emotionally boring due to a lack of immediacy. Piano notes are vaguely resolved as well as most instruments, saxophone sound better due to liquid timbre, violin begins to sound edgier in the upper mids-lower treble, but still not very rich in texture. The tonal balance of mid-range isn’t very accurate and affected by bass and treble boost.

TREBLE is where most of vivid energy happens, but it’s not particularly snappy either. In fact, treble is mostly relaxed with some extra mid-treble spike that add air and sparkle. This gives more grip to snare and percussion, but cymbals feel quite distant and hollow. On a positive side, we can say the highs are well balanced and not too aggressive, but this means you do not have a high level of clarity or detail in sound. Smooth and laid back sound from low to highs with the KS1.


VS BQEYZ KB100 (50$)

The KB100 are my personally sub-100$ benchmark IEM, it’s a dual dynamic driver plus 1 balanced armature that delivers a clear and neutral sound. SOUNDSTAGE is more holographic and out of your head with the KB100, it’s notably deeper and offers a precise and transparent IMAGING that KS1 just can’t compete with, making it sound overly intimate and congested. BASS is more sloppy with the KS1, warmer and less controlled than thigh punchy bass of the KB100, sub-bass of KB100 is heavier and has better separation with mid-bass, the extension is more natural and do not bleed on mid-range as much as KS1. MIDS are more recessed and darker with the KS1, it lacks clarity and accuracy of KS1, vocal lack definition with KS1. TREBLE of both is rather relaxed but better balanced and fuller with the KB100, the KS1 have a hint more sparkle due to boosted highs as we often encounter with V shape sound signature.
All in all, the KB100 are technically superior and can satisfy demanding audiophile with their refined neutral sound while the KS1 offer a very average V shape sound.


These 2 are both similar in look and in sound and use as well similar dual dynamic drivers. No surprise that the sound is quite similar in timbre and in tonality. SOUNDSTAGE is slightly deeper and clearer with the DM-480, which offers more space for instrument separation. BASS is more sloppy in sub and less controlled with the KS1, both are very boosted in this lower region but the DM-480 is faster and tighter in the attack. MIDS are both recessed, but the DM-480 has more upper mids push and is clearer in definition and faster in the attack, still, both have warm mids, though the DM-480 feel slightly more transparent and less intimate. TREBLE is sharper and digs more micro-details with the DM-480, highs are more snappy and well define which gives a higher sense of clarity than darker KS1.
All in all, the DM-480 feel like an upgraded KS1, especially in term of bass control and imaging sharpness.


While the KS1 excel and fail at nothing, I would not consider them as a ”jack of all trades, master of none” because of the very average sound technicalities they offer.

It’s what we can call decent sounding IEM, and even if the construction quality surpasses easily any of other IEM in its price range, the sound doesn’t feel neither competitive or worthy of audiophile interest.

For the audio enthusiast that searches a very practical IEM that sounds okay with any genre and offer plenty of bass presence, the warm sounding KS1 still is well balanced and enjoyable for laid back listen and it’s quality of material sure offer great construction value.

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