I own the gl600 for around a month. I did remove the fabrictapes that covered the drivers behind, trough easy pull of the earpads, because the fabric tape is behind Them.
They sound very lineair. It is a true reference tuned headphone. Ive burn them in with long sessions of White noise. Let them rest a while. And take them to listen. They sound more open and much more clear. But I ve concluded that the stockcable is really slow. I ordered a fast 6n occ cable with 16 silver plated Coppercores. The result was breathtaken. They sound more great now than the 1000se of hifiman. That was the conclusion next a listening session with a small group of audiofeeling friends. They are amazing. I Will recommend this headphone and tweak to everyone that loves a great sound. You shall not be dissapoined!
They show the same or more acoustic information than my stax earspeakers.
De frequensrespons is much wider than usual for an planar headphone. You can hear clearly the noisefloor that a bad recording or mediaplayer had.
They are so wide and stage depht sounding that they give a true live experience.
Gold planar did a really good job by taking much stronger magnets for the drivers. The strong puls, detail en musicality and also the very great basresponse and limitless treble makes that I am moving from my electrostatic earspeakers to this tweaked gl600.
It is honesly a shame that they deliver a stockcable that the great planar drivers of de gl600, makes sounding cheap and relatively dissapointing by only a bad cable.
But by a fast quality cable they sound fantastic.
Build quality is very solid, they feel also nice on my head.
I suggest them!