I did not find that unlocking the bootloader, root, and s-off to affect the speaker volume in any way; and would be surprised if it did. Not clear if the OP had a custom ROM installed. But I would suspect that as the culprit before the root, s-off process in itself.
Flash another ROM and see what happens.
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Phone: AT&T HTC One (M8)
Tablet: Samsung Galaxy Tab Pro 8.4 (WiFi only)