In Alcohol 120%, when you choose 4x, is the time taken to write the disc consistent with 4x writing?
There's two possibilities. One is that Nero is somehow not returning all the available speeds your writer is offering. Alternatively, Alcohol 120% is returning speeds that the writer isn't offering.
Personally, I use Feurio for audio work; I've had a paid-for copy for several years, as I sometimes am called upon to remaster recordings of amateur concerts for small scale CD duplication. That said, there's nothing wrong with using Nero (or, indeed, any other software) for audio work if it works for you.
How about an arbitration? If you install DVDINFOPro from http://www.dvdinfopro.com/, select your writer at the bottom of the window, insert a CD blank (of the same type as you were trying to write in Nero) and press the Media button at the top, what are the available write descriptors? I find this utility so useful that I'm about to register it - I feel that the author deserves a contribution for his work, though it will also be nice to be free of the adverts.
Both the media and the drive determine the available write speeds. The only writer I have room for in my main machine is my NEC ND-2500A; there's only three 5.25 inch bays in the case of my Dell Precision 650 workstation, and one is used by my DDS-4 tape drive. The machine came with a DVD-ROM (Lite-On LTD163) and a CD-RW drive (what I felt was a rather nasty LG GCE-8481B). I wasn't prepared to pay what Dell wanted a few months back when I had this dual Xeon box built for what would have been a NEC ND-1100A - the CD-RW was meant to be a stopgap. When I bought the ND-2500A recently, I felt the DVD-ROM was more use to me than the CD-RW, not least so I have a drive that I can use for a second opinion on recorded DVDs.
There's one disappointment with the ND-2500A. I still have some unused Kodak Silver and Gold Ultima CD-Rs on a spindle. These blanks, which were arguably right up alongside the Taiyo Yuden products of their day, are coming to the point where I intend to record or discard them very soon; most seem to believe that optical media has a finite life before it is recorded. I'm currently doing a lot of archiving, though increasingly I'm finding that 650MB is not enough to hold the chunks of data I want to store!
Most regard the Kodak media as 24x; certainly the GCE-8481B would write it at 24x. The ND-2500A only offers 4x CLV and 8x CLV - I guess it was never that well optimised for this long out-of-production media. That said, when the disc has been written at 8x CLV, it verifies OK using DVDINFOPro, and objectively the discs work without problems so I really can't complain that much.
On the other hand, the latest batch of jewel cased media I have is some TDK 52x media - the ND-2500A will write that at 32x CAV maximum - because the drive has a 32x limit for CD-R!
Finally - note that the latest drives often don't offer the very slowest writing speeds, and this may be what you're seeing with your Pioneer. It's been common for some time for writers not to offer a 1x CLV strategy for recordable CD media - increasingly the slowest speed offered is 2x CLV. However, the slowest speed offered by the NEC on CD-R media seems to be 4x CLV. I don't have a Pioneer 106 to check - but it's possible that the slowest speeds on CD-R media for that drive are even faster than my NEC, and it may not be able to write CD-R media at 4x.
Indeed, I've got one really nasty CD-RW here (a Memorex branded 80 minute CMC disk I was given that's a 4x maximum blank) - the only write speed available for that in the ND-2500A is 4x CLV, and I suspect that's the slowest CD speed supported on this writer. I personally wouldn't trust any data to such a horrid blank; what little use I make of CD-RW is with a box of Ricoh 10x blanks that I bought a long time ago when HS CD-RW was new, and I'd just bought a 12x10x32x Plextor SCSI CD-RW. Many of the Ricohs are still in their cellophane wrappers, but my audio CD player will read them so they're useful for audio testing.
(who doesn't always write such long posts in forums as those he's written here so far - but hopes that this is both illustrative and regarded by those who've been here for some time as correct)