iPhone getting hot playing downloaded music [Improvements Released Starting with ARC 242+]

I recently downloaded my entire library (30k tracks) compressed to my phone.

The phone (and my ROCK) both got warm during the encoding / downloading process - which didn’t worry me.

But what is odd is that the phone now gets very hot while playing.

I had a case today where my phone stopped charging in the car while playing ARC via Bluetooth because it got too hot.

I had no DSP active at the time.

I saw some posts from mid last year - but is this still a problem for other people?

My 15 Pro Max gets a bit warm during playback but not hot or very hot, and I do use Muse on the phone. (And an external DAC which gets warmer than the phone - FiiO KA5)

In this combination, battery run time is not great but manageable for the trips that I do (it does run comfortably for about 8 hours with lots of screen on as well)

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I am having this exact same issue. iPhone 15 pro Max here. It used to get hot only when downloading. Now it happens over playback (with smart downloads off). Battery degrades fast too.

I am moving this whole thread to Support because this doesn’t seem right

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Hi @GregD, @Bruno_Mello,

Thank you for the report. We’d like to pin down a few variables at your convenience:

Does this occur when connected to the same local network as your RoonServer machine at home?

Are either of you using a VPN or any managed enterprise networks in this setup?

If you activate Offline Mode in settings or switch your phone to airplane mode, does the phone still heat up unusually during playback in ARC?

We’ll activate diagnostics in the meantime. Please provide a timestamp or the name of a track that is playing when you next encounter this behavior - we’ll pursue the report from there.

Hi Connor,

I’ve recently taken advantage of the new ARC code to download my entire library to my iPhone in Opus format (260G / 30k tracks).

I didn’t notice the heat before I did this.

I’ve tried running both with and without an internet connect while playing - and it doesn’t seem to make any difference.

It can get hot enough for the phone to turn off charging and display a warning message.

Let me know if I can give you any more data.

Hi @GregD,

Just a few more questions to pin this one down:

Does this issue happen with every Zone, including the phone speakers, or is it specific to one endpoint? You mentioned playback via Bluetooth in your initial post, but we want to verify if the playback endpoint is a constant or a variable here.

Does this happen under identical connectivity conditions (ie the same spot on the road every day, or on your local network)?

@Bruno_Mello, if you’re willing to assist as well, the same information would be particularly useful. Does this occur regardless of Zone? What about file type?

Thank you again for your help.

I’ve had the ‘hot phone’ issue using wired headphones via the Apple lightning dongle, and via Bluetooth in a car.

Using a wired car connection (a different car) at the weekend I didn’t notice the issue.

I also use a Chord Mojo via an Apple camera usb adapter, I can’t recall if I’ve had the problem via that setup. I will test.

I usually use ARC outside my local network, either in the car (where it generally has a 4G connection) or when travelling in London (partly on the underground with no connection).

I really just use the car for longer journeys rather than commuting - so there isn’t a regular pattern.

Very happy to set ARC playing when I’m at home if that would be helpful, via Mojo / lightning dongle or speakers. Just let me know.

Using current release build not ea just playing via ARC makes iPhone 13 hot when on cellular. Fine on WiFi but with cellular spotty reception it seems to work harder. I don’t use downloads just streaming via core and opus.

Hi there Connor, sorry for not getting back to you sooner, it has been a busy week here. I do use a VPN - Tailscale - as officially recommended in this forum. Currently it is the only way I am able to access my server while not at home, I’ve tried other options including bridge mode to no success. That said, this overheat also does happen in home, while connected to wi-fi (and my local network). But as I use ARC mostly out of home, it is a major issue there. Many times while driving with wired Carplay, I get the message that the iPhone has paused charging because it is too hot. I was also able to test it with the arc offline and didn’t seem to change much. All my downloads now are of the -balanced- type since the last ARC update. Maybe that is something that is causing that? I didn’t have that problem before, when the downloads were the untouched files. The phone did get hot while downloading, but not during playback of downloaded files.

Hey @connor, I’m also experiencing this same overheating/battery drain issue when playing my downloaded music over bluetooth. I’m happy to answer any questions you have. It’s actually making ARC semi-unusable for me right now, so anything I can do to help speed up a fix I will.

I’m on an iPhone 15 Pro, and didn’t have any issues until this week. I’m using ARC the same as I always have been, so it may be an issue that came along with a recent ARC app update.

@connor A couple of hour drive today with ARC playing all the way - attached to the car stereo via a lightning cable.

My entire library is downloaded to the iPhone in Balanced formnat.

I think there was decent 4G coverage - although obviously not needed to download the music since what I was playing was all previously downloaded.

The phone got quite hot - but wasn’t giving messages about not charging.

FWIW my hypothesis is that is connected to playing OPUS format downloads. Previously with ‘original format’ downloads I didn’t see this.

It may be that sending over bluetooth makes it worse (the phone wasn’t as hot today as I recall it being in my other car where I play using Bluetooth).


I have tried this both plugged in and over bluetooth on my home wifi network. I’m playing downloaded content in both scenarios and not playing the music loud. When playing over bluetooth (iPhone 15 Pro > Apple Airpods Pro 2), my battery drained 9% in 10 minutes, and when playing through aux (iPhone 15 Pro > Apple USB-C to 3.5mm dongle > KEF LSX through aux) my battery drained 8% in 10 min. The phone got noticeably warm in both scenarios, and music was playing fairly low in volume.

I have finally been able to properly set up ARC (changed home ISP) and no need to use Tailscale VPN anymore. However, this issue still persists. I’ve also got the latest update and it still happens. Battery drain is fast, and the iphone gets way too hot, often interrupting the charge.

A post was split to a new topic: ARC/Android: Hot Phone During Downloading/Playback of Downloaded Tracks

Hi everyone,

Thank you for your patience as we look into this further. For clarity, this post addresses thermal regulation and battery drain issues on iOS phones in ARC while downloading or playing music.

Bluetooth and wired (dongle) endpoints, as well as Bluetooth and wired CarPlay connections, are a commonality here. Has anyone encountered this playing to the phone speakers? It’s possible endpoint is a red herring, but we want to be exhaustive in our deduction.

Most users are reporting variable connectivity when this occurs, although the symptom reproduces sporadically on WiFi while actively downloading tracks or playing downloaded tracks.

We’ll be back with a more elaborate and detailed update as soon as possible.

@mackid1993, I’ll split your post into a dedicated thread until we’ve deduced there’s a common mechanism on both operating systems, for ease of tracking.

Hi everyone,

With the last few releases, ARC has increased awareness of the OS’s reporting on the phone’s thermal status. This should have the dual effect of preventing overheating and better equipping QA and development to avoid future issues.

If you’ve experienced a “hot phone” situation like those described above with ARC, please report here and we’ll investigate.

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Hi everyone,

We’re going to allow this thread to close out. Please create a new topic thread if you encounter thermal regulation issues with ARC moving forward.