I have far more LPs than I do 45s. And I only have a few full length albums pressed on 45RPM, though I've often seen 45RPM special issues of some jazz albums, along with the latest Metallica re-issues. There are two questions I have concerning this : Is there any audible sound difference on middle end equipment ? and A question of the downside of using 45RPM. From my experience with 45RPM singles, they don't sound as good. From my experience with 45RPM albums, they sound just about the same. Possibly better in terms of the higher frequencies. High end rolloff on slower turning discs could be due to lower "resolution" of the data on the disc. If it spins faster, it has the potential to read more of the data stored. But, you also must ask at what speed was the disc recorded? If it was recorded at the same speed, 45RPM, or faster, the quality may not be any different. If it was half-speed mastered, it could be potentially better sound quality, as the writing needle has more time to accurately engrave the groove. The other side of this is that if the disc is spinning faster, it has more potential to pick up imperfections in the vinyl. If you have a scratch on the disc, it is more likely that you will hear the pop or the crack more frequently than a 45 RPM disc. This could be one major pitfall. So, keep those discs in tip top shape. Imagine, then, the sound of a 78RPM shellack record with all of that extra dust and grime within the grooves during playback. It is bound to have a ton of cracks and pops. And then we have the convenience factor. A CD holds approximately 80 minutes of sound, without having to flip it over ever. This is extremely convenient. Think of an LP, which generally holds 20 minutes per side, with some exceptions, ie Bob Dylan's Desire (1976), a single LP with a whopping 56 minutes of audio. A feat in re-mastering if there ever was one. But, you still have to flip the disc to hear the second side. Most people do not find this to be problematic. But, then you have 12" 45RPM album releases that contain one or two, sometimes three short songs on a side before you have to flip, and these are generally spanned across two or three discs. Increasing the amount of time changing discs and flipping. Decreasing the amount of continuous listening time. Take, for example recent reissues of Metallica's albums, spanned across four to six 12" 45RPM discs. What a nightmare this must be to listen to. Sure the quality may be slightly increased, but the functionality of the format begins to wear thin at this point. Does anybody have any thoughts on this? I think it's a good discussion. I'm sure some audiophiles will disagree with my thoughts.