I have just started throwing songs onto a CD to try in the car. 
For demo sake, is there a lot of diff between the top mp3s and a wav?

I assume I can get a lot more on with mp3s.

(I was surprised and dismayed at how road noise affected the mix.)

Once you get up to 320 bit rate there isn't that much.  You should be able to burn 100 mp3s on a cd - that used to be the limit.  But why mp3?  You can put 70 minutes on a wav CD.  If you are listening to your work, I'd suggest plain ole CD format.

One caveat - some older players won't play mp3s on CD.  Be sure and check before you put your 100 songs on that you can listen to it.

@

I'd burn a Red Book standard CD, so that it will be compatible everywhere. Just as listening in the car was a surprise, you'll have a different surprise everwhere you play it. You'll want to take it around to as many playback systems as you can to see how your mix translates.

Yeah, a CD should be Wave files, not MP3. 

I listen to my work during the day from an MP3 player with 320kbs files. But if I was able to listen in my truck, it would be waves. 

Listening in a truck, with road and traffic noise is certainly going to affect the quality of what you hear. There is also the aspect of the inherent quality of the mix itself. This varies depending on the acoustics of the listening room you mixed the songs in. 

This gets into the old familiar discussion of just how accurate your monitoring and mixing environment is. If you are not hearing the "real mix" for one reason or another, monitors not reproducing the frequencies, room acoustics, etc..... the mix, which you "dialed in" to sound good in the studio, can sound absolutely horrid in any other environment it was not specifically mixed for.  The classic ..."It sounded good in the studio but sux in the car" scenario. 

But if you have the option, on a CD burn waves.  

Don't forget to have a reference CD or two in the car to test against your own music. A lot of commercial CD's sound pretty bad in my van, an example being Mark Knopfler's latest, which I have to turn up really loud to hear anything but his voice and lead guitar.

Are there any general frequency ranges to pay attention to when thinking about how a mix translates to a car stereo? Some of us don't have a car...

Sharke, no car?  I was the only one I knew in NYC fool enough to keep a car.  It was a primered (old style) Chevy Nova w/ the back seat taken out and shark teeth stencils and barb wire on the front.  Bought it off the Butthole Surfers back in '84.  I'd drive around the East Villiage and the kids would all yell "I tagged you..." 

When I lived on bond st. I'd park it on first around the corner from CBGBs - unlocked.  I understand the 'Selka is there now but back then there were a lot of derlict cars there.  Any morning I used it I always had to chase a bum out, after thanking him for the security.  The radio was long gone and the barb wire kept the battery in.  

I hear NYC changed in the last 20 years. ;-)

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An interesting experiment is to burn a CD of white or pink noise, take it out to the car and record it, then take a look at the result with SPAN. It's an eye-opener.

I always ask myself before going out if it (As a Demo) is what Im trying to get across to the business Im delivering it to to actually portray what the band will deliver for what they are paying for.

Around this area Ive heard MANY copies of other bands demos and it ranges from terrible to beginner level recordings (meaning it sounds like their first attempt at a demo recording).

I like to think on the "First Impression" makes a world of difference but then try to keep it realistic.  Most places you go to will just have similar playback devices that we already have sitting around the house so I like to set it up to that.  Ive been to many places that they know the bands but still want to hear a demo (I think they like collecting cd demos   ) and not have nothing available,  Ill break out my iPhone or actually take them out to my vehicle so they can hear the demo.

As long as you are happy with what your trying to sell as far as what the band will deliver to a paying customer-I wouldnt get to critical but make sure your happy with it on all your available playback setups-Auto, small cd player and computer I think you will sell it  


For my stuff I use Wav files and have got paying gigs on every delivery with on going placements throughout the year

sharke

Are there any general frequency ranges to pay attention to when thinking about how a mix translates to a car stereo? Some of us don't have a car...

Sharke, I don't know NYC well at all, but FWIW the New Yorkers I've met were great folks. I wonder if you were to meet a cabbie that was game for a CD road test? Maybe it could develop into a regular gig for you both!