That's not how that works at all. The burn speed is determined by what material the disk is made of (not the plastic, the material that the data is written to).
But back when I burned CDs and DVDs, I had disks that would only read at low speeds, or not at all in some drives, etc., but it had nothing at all to do with the rated burn speeds; there was simply a surprising variability in the quality of the disks. I can assure you, I had some old 12x and 24X CD-Rs that'd gleefully play back at 52x, and 1X DVD-Rs that'd read back at 4x no problem.
Maybe you misread my explanation
I AGREE that the playback speed has nothing to do with the rated burn speed
But that's not how playback speed is determined on any of my computers
The pre-burn test determines the maximum burn and playback speed (without errors) of any recordable disk
If the test determines that your 16X disk can safely burn and read at 12.4X, then it burns and plays your 16X disk at 12.4X
If the pre-burn test determines that your 16X disk can safely burn and read at 9.2X, and yet you decide to burn it at 2X (to be safe), you have already seen that you can read it faster than 2X, and I have seen that it can never read as fast as 16X
Mark the actual safe burn speed that the recorder selects for 3 separate disks (with 3 different burn speeds), then record the playback speed of each
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Do not rely on the recording software to give you the actual speeds
Record a fixed amount of data in one big file
Try 100MB for CD, or 1GB for DVD
Record the burn rate (as it burns)
Record the actual playback rate by copying the test file on disk and pasting it on a hard drive or SSD using a stopwatch
Recording software often lies to you!
It will test the just burned disk and tell you it was recorded correctly, but when you copy it back to a hard drive, you can often get cyclic redundancy read errors
Always test the burn accuracy by copying the entire contents of the optical disk back to your internal drive to verify the write
Otherwise, you WILL lose data by blindly trusting the burning software to verify a write