This is what I wrote to the good people of RHA because Valentin would do the review. My point of view was just for them, but why not post it here as well. Be aware that Valentin had a lot more time with the units than I did. This is just a little extra and a second view on these units but I do think that Valentin was extra harsh on the 600.
In short, I think the price quality ratio is correct (70€), it isn’t the best iem I’ve ever heard but in its price class it’s ok. It has a very dark background and sound stage isn’t the biggest, it’s a more compressed sound and that’s understandable. At the same time you get a more inside your head, centered sound but with good left/right separation. I’d say the detail retrieval is normal for this price. Big focus of the unit is on the bass. Bass isn’t always tight and can be boomy taking over part of the mids. To me the 600 is clearly made for the day to day popular music, R&B, etc where bass is important and detail and extension isn’t the biggest concern. However it does that pretty good. Overall pace and attack of the 600 isn’t the best making it a bit slow to listen to with fast rock and metal (but as I said, it’s more of a big crowd iem for popular music). It’s a fun iem to listen to while commuting with a big toe tapping factor and great isolation.
Clearly the 750 (at 106€) is a big step up from the 600. Sound stage is a lot bigger and more up to the level I’m used to (but I’m spoiled). Detail retrieval is good and the inside your head sound is gone, it has a lot of space between instruments and a more 3 dimensional sound. The750 is a lot more linear as well, the focus on bass is gone and treble is further extended. You get a very clear, pleasant and faster sound suitable for all musical genres. Bass here isn’t as punchy and doesn’t have as much body as in the 600, but it’s more detailed, faster and tighter: Way better. It’s still a darker sounding iem but with good clarity. It has a nice balance between musicality and technicality. A great price/quality ratio and my favorite unit by far.
Looks & comfort
They both look great, especially the 750 and for the price you get a lot of tips and accessories. The 750 pouch is hard to close but I’m nitpicking here. I’m a big fan of over the ear iems, so clearly the 750 wins in this category too. I like both cables, clearly the 750 cable is better but it’s also heavier and the control unit doesn’t help in that regard. The plug with the spring is an excellent idea and I can appreciate it although most people who use iems on the go prefer 90° or 45° angled plugs (less space needed). Personally I could do without the remote, bringing me to my next points: comfort/fit & weight. Both iems are on the heavier side, especially the 750 and the cable with control ads to the total weight. I personally had a lot of problems to get and keep a good fit, and without good fit the sound quality of course drops huge. My ears aren’t the easiest for using tips and I hardly find any that fit me, that’s why I’m a fan of custom monitors. Sitting down and listening to music is ok, but walking around didn’t work for me. I tried a lot of the tips (even the foam ones) but couldn’t get a good lasting seal. The 750 being over the ear is more comfortable as the over ear system keeps it from moving a bit. So maybe it’s just my weird ears (following Valentin’s comment, I should have ear surgery)
What to remember?
It’s clear the 750 is the more audiophile unit and it’s a great sounding iem for that matter, I like it, especially at this price. It’s one I can and will fully recommend.
Thank you RHA for sending us the samples. As Valentin sad you can buy them from their website, the Apple stores or their dealer network. We hope to see great even higher level products of RHA in the future.