Is it normal for earbud sound to change with new iPhone?

Of course, this is not normal.

How to Contact the Manufacturer of the Earbuds:

1. Product Manual: As mentioned, the product manual can be an excellent resource for finding contact information. Look for the "Support" or "Contact Us" section in the manual.
2. Product Packaging: Check the product's packaging for any contact details, customer support numbers, or websites provided by the manufacturer.
3. Manufacturer's Website: Visit the official website of the manufacturer. Most reputable companies have a support section where you can find contact information or submit support requests.
4. Customer Support: Look for a customer support phone number or email address on the manufacturer's website. Some companies even offer live chat support for immediate assistance.
5. Social Media: Many manufacturers maintain a presence on social media platforms. Consider sending them a message or mentioning them in a post to seek help.
6. Retailer: If you purchased the product from a retailer, they might also be able to assist you or direct you to the manufacturer's support channels.

When contacting either the app developer or the manufacturer, be sure to provide specific details about the problem you're facing, including any error messages, screenshots, or steps to reproduce the issue. This information will help them better understand and resolve the difficulty you're experiencing.

Remember to remain polite and patient while seeking support, as it may take some time for the developers or manufacturers to respond to your inquiries.