Why doesn't Logic preview audio WAV loops in sync to your project as your cycling through them in the library?

I know it does with Apple Loops, but that doesn't help much because all of my samples are WAV and Mp3

Please guide me as I'm new to Logic X

Wav and mp3 file format dont included tempo information embeded.

I guess you need to convert your files in apple loops.

Thanks, Stratquebec for your reply

But now my question is, 

I have no idea about the tempo of the wave loop file and also there are thousands of loops which it will take time to adjust tempo in the AU. 

Could you please please guide me how to convert a huge amount wave file of unknown tempo or any other alternative way.

I recommend to think three times about converting them. Then think four times to decide which ones you want to convert. Especially because you write you don't know the tempo. It's going to be a huge PITA. Just don't do it for all the others. Stop thinking about it, when you High Sierra and cannot install Apple Loops Utility. 

The converting is the easy step. There are tons of batch connverters. 

Then the second step, that I do myself within the first step using Myriad (batch converter with a LOT of features, not free though). Most of those batch converters don't support tags for Apple Loops. Actually you don't need that, you can use Apple Loops Utility to batch-edit your Apple Loops (except you have High Sierra, then you're screwed). 

So... then the last and hardest part: Tagging correctly the Apple Loops. This highly depends on your information about the sample/loop libraries. If you're lucky the file name contains all the information you need: Key, BPM, beats. These are the crucial information when adding the loops into Logic. Key is not needed for drums only though. 

I converted some very good labelled and well structured libraries, e.g. they were like this:

- Within one folder the key and/or BPM was given

- The files were labelled properly with key and BPM

- In rare case even the number of beats was given

In this case I just had to multi select the converted files and edit their tags (Apple Loops Utility)

The less information you have, the more manual work you have to do, FILE BY FILE. So thousands of unlabelled wav-files, will take you weeks to properly convert and tag. I actually just deleted a lot of those "bad" sample libraries. Since I didn't use them often, they became somehow useless for me. Pitty for the money, but that's life. Expectations change over time. 

In other cases it was worth the hassle, the pain, the nerves and time it cost me

For a few of those "bad" libraries, I imported all those wav-files into a project. Found the tempo, grouped and arranged them by amount of bars/beats. Renamed the regions, exported them from the arrangement window as new audio files, while converting them to aif. I did this group by group into a unique folder like /loops ABC/drums/1bar/, the next group into /loops ABC/drums/2bar and so on. After that I batch edited the tags in Apple Loops Utility folder by folder. 

Luckily for me, I hardly have instrument loops, so rarely had to deal with different keys. But the process I described above will just have a step more.