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frequency response for mp3 files??


classybum
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just wondering if anyone knew of frequency cutoffs for mp3's.

one day i was searching for the 1812 overture cause someone recommended it for its bass heavy cannons, and i downloaded it from a few different sources, and it sounded horribly weak. i've heard those bass peaks are at 30hz.. and am afraid that perhaps the encoding process cutoff some of the low frequency?? any clues?

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my guess is yes it's cutting off the dynamic range. i have that telarc disk & those cannons go low & deep - thought I read they go down as low as 5 hz. the disk as a whole lacks some on the dynamic range, but those cannons sure don't. thought i read that mp-3

does limit the range. maybe someone else can provide the techs on that. never used it myself. which sub are you using?

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live long & prosper

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classybum,

asking "what's the frequency response of MP3?" is kind of like asking "how spicey is chili?" - it depends on the cook.

If done with care, under the proper circumstances, by someone who understands how to apply perceptual encoding with the least degredation to the original signal, MP3 files can sound awfully close to the CD or other source from which they're mastered, most of the time, which would imply a full 20Hz to 20kHz frequency response range.

However, most of the stuff you're going to find at alt.binaries.mp3 or mp3.com or wherever has been ripped under less than ideal circumstances, and you may be listening to a multi-generation copy of a series of lossy encodings. No way to tell. I've heard some MP3 files of Nirvana and Aerosmith that sounded so bad (ie, so far away from the original source wence they came) that people were claiming they were alternative tracks or bootlegs. Not so, just really, really bad copies of standard tracks. As far as your 1812 goes, I am guessing that the cannon shots would be one of the more challenging signals to capture in a lossy encoding without messing up the sound. Buy the CD.

Ray

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cyber- i'm using a sub that i built myself.. 12" ported design.. plays everything else wonderful, music and HT.

ray- I'm not entirely certain how one would acquire or make a multi-generation copy of a classical piece off of a lousy recording, as most of them are released on compact disk these days, and then ripped by home users equipped some some commercially available software such as musicmatch or whatever they got with their spiffy new CD-RW, but, upon listening to the pieces i have again, it sounds like cannons were not even used in the versions i found. perhaps rifles or something. there is no boom, more of a crack to their sound, in each of the three different versions i found. i even had my roommate, a music major, listen to them, and he had no idea what was going on in the pieces.

In the end, i guess i'll just have to take your advice and find the cd myself, hoping that i'm not stuck with those dumb rifles or whatever they were.

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Technics SA-DX940

Sony DVP-S360

Klipsch KSC-C1

Klipsch KSB 3.1

DIY 12" ported sub

crappy surrounds

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cb, yea those cannon are more like a crack at first, but they're followed immediately by a low powerful rumble-percussion. that mix must really be missing the lower range considering your sub.

you can get it direct from telarc:

www.telarc.com/gscripts/search.asp?mscssid=M4AS0VNW28SR2KNP000CMP0LRU8N03X9&usrSearchBy=3&s=1812&q=cbk&submit.x=12&submit.y=7

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Velodyne HGS-18 sub

Monsterbass 400 sub cables & Monster Z-12 wire

Sony de935 a/v receiver

Sony DVP-C650D dvdp

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Technics dual cassette deck

Technics direct drive turntable

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rock on!

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classybum,

just to be sure we're on the same page here, I wasn't saying the MP3 was ripped from a "lousy recording" - that is, a badly recorded CD or something. I said it was a multi=generation copy of a "lossy encoding" - MP3 uses perceputal encoding to "throw out" significant portions of the sound of a recording which, according to theory, you can't hear anyway because they're masked by other things going on a the same time within the recording, thus dramatically reducing the amount of data storage required. This is why they're called "lossy encoding" - they throw out significant portions of the signal and encode the rest.

Multi generation copies are easy to come by. I have a CD. I use a piece of software, and encode the maximum amount of bandwidth I can get at a 384kHz data transfer rate and create an MP3 that's, oh, 50 megabytes. Someone else downloads it, and re-encodes it at 256kHz to shrink the file a bit so they can fit more of it on a CD-RW. They have a bud who wants a copy, but has a slow modem, so they re-sample the 256kHz version at 128kHz (we are now on the third version of a lossy encoding) and upload it to their friend, who has Napster istalled. Anyone else who downloads this is gonna get a (probably) awful sounding third generation copy of a lossy MP3 file that's been wrung out to dry.

Ray

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FYI, there are a lot of recordings of the 1812 overture on napster or wherever else you're looking. I have 3 versions, all with different intros and different sound. Anyway, I have an mp3 of Terlacs version and the bass registars to well below 20 hz. Keep looking and you'll find a copy with full dynamics.

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