Serious question ‘bout headunits.

[paul p (chi-town)]

So i’m shopping and trying to figure out what’s important.
I listen to CDs alot and am not quite on board w/ iPodish stuff, but the NX & Turbo have mp3 CD capability and i do like that.
How important is 24bit A/D conversion. I can afford 100db s/n ratio, but that 24 bit means a big step up in price.
What else should i be looking for to maximize CDaud/MP3 sound q?


”Hang up & Drive!”
94 BMW 530iT&A 125K, ‘Helga’ (for sale yet? no *grrrrrrr* but getting warmer)
92 BMW 325i 120K, ‘Rolf’ (he’s baaaaack *woohoo* time for tunes)
91 Volvo 745T 194K, ‘Thor’ (13 psi *smirk* no power steering *grunt* )
93 Datsun NX2000 165K ‘Carla’ (alive, thumpin MP3s *grin* Hers *sigh* )
"Those who would give up essential liberty to purchase a little temporary safety deserve neither liberty nor safety." -- Benjamin Franklin.
Kinda makes the ‘Patriot Act’ an oxymoron, eh.......

[SRR2]

24bit converters and "100db s/n" are a waste of money in a automotive environment. Cars are so noisy that even the cheapest audio crap has a noise floor low enough that you're not going to hear it. With the exception of classical music, none of the program material you will listen to has a dynamic range greater than about 12dB, and a lot of it has a range of 0dB. With material like that, you won't hear a noise floor of even 40dB. Save your money.

I put a Pioneer 4700 in the 325iX. Works perfectly, easy mate-up to the stock amp, fantastic AM and FM reception with the stock antenna, and plays homemade mp3 disks flawlessly. <$100. The only downside is that the aesthetics aren't a perfect match to the stock appearance. To get that stock look you are into a very expensive Nak.

[pundit]

[color=indigo]So i’m shopping and trying to figure out what’s important.
I listen to CDs alot and am not quite on board w/ iPodish stuff, but the NX & Turbo have mp3 CD capability and i do like that.
How important is 24bit A/D conversion. I can afford 100db s/n ratio, but that 24 bit means a big step up in price.
What else should i be looking for to maximize CDaud/MP3 sound q?

As SSR2 has said if you listen to mainly current music ie. pop, rock doof whatever, & especially MP3's, then 24bit is a waste of time. Dynamic range is a major no-no as far as the major record labels are concerned and any hint of amplitude variation must be squashed into submission.

In fact 24bit and MP3's are almost a contradiction. 24bit extracts the most dynamic range and low level detail out of the signal whilst MP3's throw most of the data away. If you listened to uncompressed real music whilst parked in a quiet pine forest with your motor switched off, after having exterminated all the local wildlife (birds & chipmonks make noise & will reduce your signal to noise ratio and effective dynamic range), then provding you have several thousand watts of true RMS power and a speaker system that can cope with the dynamic range, then 24bit might just be worth considering!

[SRR2]

At the risk of hijacking the thread, you might be surprised about the Conventional Wisdom concerning resolution, noise, and mp3 compression. Short story: the better mp3 compressors (Lame) do short-term autocorrelation as part of the FFT. This has the effect of reducing random noise and quantization noise provided the output bitrate is high enough to carry the bits needed for it. IOW, you can (and do) hear the difference between 16 and 24 bits in playback as long as the material was 1) good enough to begin with, and 2) conveyed at a high enough bitrate, APS or better. In my home audio system I use a M-Audio Delta 24 bit card. The difference between this and any 16 bit card is readily apparent on the equipment I use.

It is not true that "mp3s throw most of the data away".

[paul p (chi-town)]

As SSR2 has said if you listen to mainly current music ie. pop, rock doof whatever, & especially MP3's, then 24bit is a waste of time. Dynamic range is a major no-no as far as the major record labels are concerned and any hint of amplitude variation must be squashed into submission.

With my eclectic taste in music, Bach is just as likely as Beastie Boys, or Coltrane for that matter. Though I do understand most modern music is produced w/ tons of compression.
So, to appreciate that 24bit will require well north of $1K in amps, speakers, cables and sound deadening?

”Hang up & Drive!”

[SRR2]

Or really good headphones. All that AND a discerning ear. I suspect the latter is sorely lacking in the current crop of 20-somethings who, by and large, are already deafened from movies, concerts, and Ipod-like devices. No getting around it, listening to hip-hop at the sound pressure level of a 747 taking off is going to do bad things to one's hearing.

The residual quantification noise in 16-bit audio is VERY small, approximately 1 part in 65000. That amount of distortion is already well below what any but the finest electronics will achieve. And ORDERS OF MAGNITUDE lower than the harmonic distortion of virtually all speakers. Odd-order harmonic distortion is speakers driven to anything over the level of quiet conversation is horrific, measured anywhere from several percent to tens of percent.

If you want to know more about the art and science of compression, visit Hydrogen Audio at http://www.hydrogenaudio.org/forums/index.php?act=idx