best MP3 bit rate

While you can rip files at almost any bit rate, and higher bit rates equate to better sound quality, the limiting factor is going to be the ultimate device reproducing the sound. Auto stereo equipment ranges from very good to somewhat adequate and all of it is tailored for the particular vehicle.

If you can get the specs for the unit in your car, then you know the frequency range of the amplifier. I would assume the speakers are not 'audiophile' quality, so their ability to be faithful to the input signal is questionable as well.

I happen to have a lot of classical music on MP3 and even at a high bit rate, the upgraded in-vehicle system isn't nearly as good as my home system. For most purposes a 15k bit rate is overkill, but it is a good balance between fidelity and file size.

Did you mistype by chance or am I missing something.

I've had the very odd mp3 at about 48 kbps and they are barely listenable. 128 - 256 seems to be more the norm and sound fine on computer and car speakers.

There are two variables you can set when ripping or converting to mp3. Both are important and both effect sound quality.

The one you referred to is the bit rate and that is the size of the pipe through which the music is sent. The larger the pipe the more you can send through at once. Most people won't be able to hear much improvement with bit rates over about 128 Kbs.

The other variable is called the sample rate. In order to get good reproduction, you need at least 2 digital samples of each cycle. Humans generally don't hear much above 20,000 Hz so a sample rate of 48 Khz will give good reproduction up to about 24,000 Hz.

You also need to balance the sample rate with the bit rate. A sample rate of 128 Kbs will generate more data than can be sent through a pipe only 22.5 Khz wide. That will result in distortion that is really objectionable.

To sum up, 128 Kbs at 48 Khz would be about the minimum for music. I rip my audio books at either 32 or 48 Kbs at 22.5 Khz. If your software supports it, you might try using the Variable Bit Rate mp3. It should give you smaller files with no loss in fidelity.

As a rule of thumb, I record at the highest level the device supports. I find that 128kbs is the bare minumium to use for my purpose.

The big thing to remember is that quality = space. The higher quality you record at, the more space it takes, thus reducing the amount of music you can take with you.

This gets even more important, if you use the same device in your auto, your home, as a stand alone with headphones.

If space is no problem, as you stated, and your device supports it, I would use a lossless format.

I have pretty poor hearing and even I can tell the difference between things done at 192k and anything less. It is important to understand that this isn't just a high frequency issue; mp3 is a lossy format, meaning that errors are introduced into the audio to achieve the compression rates. The lower the bit rate the worse the mp3 will sound, even on very low end equipment.

Low bit rates are generally done to reduce file size, and sometimes to speed transfers across the Internet. But the trade off is sound quality.

So if space really isn't an issue, I suggest that you will want the highest bit rate that your nuvi will play back. Even 320k isn't out of the question and the same file will sound pretty good on better audio systems, but I don't know if the hardware in your GPS will keep up with it (not all hardware, particularly some low end portable mp3 players, can process 320k).

If you want to do the extra work and do different mp3 encodings for different hardware, then make a 320k for some uses and try 192k and 256k for youer nuvi and see if the 256k sounds any better to you. Of course, make each from an original uncompressed source, don't recompress a higher bit rate mp3 to a lower of you will introduce needless extra error.

And absolutely never try to convert a lower bit rate mp3 to a higher bit rate. It will sound slightly worse than the lower bit rate mp3 and be bigger at the same time (and yes I have found people who think they were improving things by making a bad mp3 bigger).

Better yet, use a FLAC file as your master and downsample to mp3 in your selected bit rate that way. After all, FLAC is lossless but is also a compressed file format.

http://en.wikipedia.org/wiki/Flac

Not sure how much of a concern it is but higher bit rates (and losslees formats) require more CPU (sound chip) power to process. Since you can plug in your device this probably isnt a big deal, but if going portable it can significantly reduce operating time.

I archive / rip all of my music on my PC in FLAC format and then convert to MP3 (128-192K) for my ipods, phones, etc

Quality .... always rip in 320 bit rate if you enjoy listening to good music
Space ..... rip in 192

I find that re-ripping is a hassle and usually default to 320 just to future-proof my music . . .

OK. thanks to everyone. Appreciate the advice. Does anyone know whether there is any signal/sound loss using my Nuvi 360 for the MP3 player? My car audio is the top of the line Alpine and the speakers have been replaced so the quality should be there.

At 320, there shouldn't be much. But if you have TOTL stuff, why use the nuvi?

Yes, you'll lose some sound quality over any analog transfer ... wouldn't worry about it in a car though. Also I'd recommend ripping at 44.1 / 192 kbit as above that you be real hard pressed to notice any sound quality difference.

In my test, with my Nuvi 770 and through less than audiophile equipment, the (very slight) winner for the Beatles was a 256 kbits/sec with a constant bit rate. I tried 3 lower and 1 higher rate and constant and variable bit rates. (And yes, I need a life...)

But this is a n=1 situation and your mileage may vary.

Happy burning!

I rip everything at 192

MP3 320Kbps CBR if I have the source file, 192Kbps minimal. I prefer AAC over MP3 if I have a choice. If I don't, I will take anything useful and available.  

These are great comments and I'm betting there are others out there who are interested in the comments as well! Again, many thanks. So here is what I've done:

First, I found out that my iTunes will convert to MP3 as long as the file is not copy protected.

Second, While I'm still not clear on the best combo, clearly the one I was using was incorrect so I found the best rates/size the old fashioned way. I had my wife listen to the various combinations with our favourite song - "I believe" (the one used at the Olympics). And the winner was.......48kHZ rate and 320k bits.

Third, I'm transferring the information (Including some audio files) to an 8GB SD in my Nuvi360. The reason is simple, the cell phone bluetooth in the radio doesn't allow hands-free dialing of POI numbers and if I use the cell-phone through the GPS bluetooth, the music doesn't automatically cut-out when a call or a new direction comes in if the music is loaded to the radio or I use an iPod. Ergo use the Nuvi for the music storage, hands-free dialing and as a GPS. Works for me!

So there you have it. I now have 18.5 hours of great music,, some 40 hrs of talking books, hands-free dialing and my Garmin - altogether at last!

Seasons Greetings to everyone and play safe!