Quattro is not an IEM built for everyone. I spent a few hours with these iems and I can understand why they can be hit or miss.
It has a very warm signature. The bass is very, very thick, and it's all over the frequency spectrum, dominating the way the mids and treble sound on these. This is not a hard-hitting bass with full subbass rumbles but a thick, enveloping bass where bass is spread everywhere. It's like everything sounds within a layer of bass. Mids are sweet, and since the bass is all over the mids, vocals are quite thick too because of the bass (bleed). I do not find the treble to be airy or carry a lot of energy, but I never had any issues with the treble. I can live with this amount. The timbre and tonality of these iems are something that few can very easily connect to and find very musical.
If you want an iem to throw a lot of precise technicalities and details, this is not the iem for sure. I have seen a lot of people say it is technically very good for an all-DD IEM, but I tend to disagree (just a little). It surely does a lot of good things, but somehow I feel it falls behind many others because of the way it's tuned. There are a lot of details getting eclisped under the bass. I think it's totally fine if it is not technically very sound. I like my iems to be either very technical or to a level where I am not bothered about these technicalities at all. If you love this signature, you may surely enjoy it and call it a winner.
Source:
With a warm source, the Quattro can be a disaster. It pairs well with a bright source. Also, it is a sucker and needs a lot of power. With the Earmen Angel, it sounds better than with the LPGT. Angel has an ESS Sabre ES9038Q2M dac chip and is quite powerful too. With a good, powerful source, the sound is more open too.
Mini Trifecta??
As soon as I put these on, they reminded me of the
Campfire Audio Trifecta. For me, Quattro is a mini-trifecta. I am not sure if Penon took some inspiration from the Trifecta's signature, but these two iems are quite similar in how they sound. And no wonder they both have a very different audience and fan following. Take everything a few levels up—soundstage, detailing, openness—you have the Trifecta with you. Trifecta has a similar bass all over, but it's more open and more spherical, if you know what I mean. Trifecta has troublesome upper mids, which will kind of disturb or annoy you very often if you are sensitive to the frequency. Quattro, however, has just a little hint of a similar thing but does not annoy at all. I remember I liked the Trifecta when I tried them on three different occasions but could never gain the courage to buy them, thinking, What if someday I wake up and find that it's totally disastrous? But I can surely own a Quattro and get some of the Trifecta's feel.
Lastly, I can only say it is really good of Penon to release something like Quattro. I think this is quite a positive release. This only means they can tune their iems very differently, unlike a few brands who would just stick with a similar tuning and change a thing or two here and there.
One more thing: Please demo these iems before you buy. There is a high chance that you will fall in love or totally regret your purchase.