Hi @Teun_Romme,
Thanks for taking the time to run those tests properly; the split you measured between local and Qobuz turned out to be exactly the right thing to look at. I’ve gone through your Roon Server logs from the past couple of weeks, and I can rule a few things out with confidence.
Your network and port forwarding are healthy. Across 82 connectivity checks in the logs, the port test passed in under a second every single time. The logs also show a single NAT with a normal public IP, no double-NAT, no carrier-grade NAT.
The 8–10 second connection test is expected in your setup, and it isn’t a symptom. Nearly all of that time is Roon searching your LAN for a UPnP-capable router and timing out after about 7 seconds, before it runs the actual test. Since you’ve forwarded the port manually on the ER7212PC and UPnP is off there, that search will always time out. You can enable UPnP if you’d like the test to feel snappier, but nothing functional changes, that number is safe to ignore.
On Qobuz, the logs confirm what your test results suggested. Your server really isn’t involved in Qobuz playback in ARC: across 109 Qobuz track starts, it made zero requests to Qobuz. It hands ARC the track and your phone downloads from Qobuz directly. Your server answered every one of those requests in under a second, and its own connection to Qobuz averages around 150ms. So the delay is happening between your phone and Qobuz, after your server is out of the picture.
What I can see is your phone giving up and restarting tracks, 28 of 89 Qobuz tracks were re-requested up to several minutes later. Local files show nothing like that.
There’s one asymmetry that likely explains it. For local files your server transcodes to a compact stream before sending, which is why they start in 2–3 seconds. For Qobuz it can’t do that, your phone pulls the original file at whatever quality Qobuz serves. On a cellular connection, a hi-res Qobuz album can be 10–20x the data of the same track played from your library.
Three things would confirm or kill that:
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In ARC’s settings, what’s your streaming quality set to for cellular? If it’s on Original, could you drop it a notch and retry the same Qobuz albums?
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Which Qobuz albums are the slow ones, and what sample rate / bit depth are they? Are the fast ones 16/44 and the slow ones 24/96 or higher?
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Could you try the same album in the Qobuz app itself, same phone, same cellular connection? If that also stalls, we’re looking at the link to Qobuz. If it’s instant, it’s something in how ARC handles that download.
We’ll be monitoring for your reply, thank you!