CDSpeed claims to be measuring C2 errors. These are read errors, and will be completely different from one drive to another. A poorly written CDR will show some degree of read errors on most every drive you read it in. Depends on the drives read-capability. Some CDRW drives are poor readers, some will slow the read speed to 4x or less to read those difficult sectors with no errors. The main thing is to always check for read errors on the same machine. CDSpeed is best used as a tool to compare the results of different write speeds, different media, etc. In most cases, the result you are looking for is “0” errors, and a full-speed read session.