When my iPhone is connected to my car speakers when a loud bass part comes the volume drops i even turned off headphone safety but didn’t do anything. But my Brother’s iPhone doesn’t do this.
iPhone SE, iOS 15
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Restart your iPhone - Apple Support and Update iOS on iPhone - Apple Support.
If the issue persists, see the steps in this article: If you can't connect a Bluetooth accessory to your iPhone, iPad, or iPod touch - Apple Support. Even though the article is titled "If you can't connect a Bluetooth accessory to your iPhone, iPad, or iPod touch", the steps are still useful.
Jack
iPhone volume reducing / dropping and going back to normal
