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#714 - 23/10/1999 01:50 What freq can empeg reproduce?
BasicGuy
stranger

Registered: 27/09/1999
Posts: 29
Can Empeg reproduce the full 20-20,000 freq?
I think I remember someone posting and saying it can only go up to
16,000 and then it just stops. Can you tell that its cutting out the highs?
Or is not that big of a difference? Thanks for any help the reason I'm asking
Is I'm building my car for comp and I'm wondering if I should keep my cd player
in the car even after adding the empeg. Mainly for comp

Thanks,
Brad


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#715 - 23/10/1999 17:12 Re: What freq can empeg reproduce? [Re: BasicGuy]
dmoore
journeyman

Registered: 08/06/1999
Posts: 58
Loc: Houston, Tx, Usa
If you would like to find out - I have a full array of Offical test tracks that you can put though your Empeg. Just contact me - [email protected]


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#716 - 23/10/1999 21:07 Re: What freq can empeg reproduce? [Re: BasicGuy]
Clarke
journeyman

Registered: 18/08/1999
Posts: 90
Loc: Scottsdale, AZ USA
I don't think it's a matter of what the empeg DSP can reproduce. My recollection is that they used a top-of-the-line DSP of better quality than what you would find in an expensive sound card for your PC. The issue is the encoding method. My understanding of the MP3 codecs is that freq's above 16Khz suffer significantly depending on the data rate and coded used.

I can't tell the difference between a CD player in the car and the empeg playing the same song when recorded at VBR high quality. I'm sure others can, but I can't. I haven't noticed missing those freqs, but then I'm not an audiophile (the car's the wrong place for an audiophile anyway). If you really needed that kind of frequency response you could record your music in MP2 or pure WAV format - which the empeg can play back without loss. Probably what you would want to do in competition.

Cheers,

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#717 - 23/10/1999 23:30 Re: What freq can empeg reproduce? [Re: Clarke]
BasicGuy
stranger

Registered: 27/09/1999
Posts: 29
You say you record in VBR high mode. Do you mean you set it to 100% on the
encoder?
One other thing you said above 16k the decrease is noticeable what about
low freqs like 20-100 do notice less bass or about the same?

Thanks,
Brad



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#718 - 24/10/1999 00:56 Re: What freq can empeg reproduce? [Re: Clarke]
tanstaafl.
carpal tunnel

Registered: 08/07/1999
Posts: 5549
Loc: Ajijic, Mexico
>> you could record your music in MP2 or pure WAV format - which the empeg can play back without loss.

Ummm... I don't think the empeg can play back in pure WAV format, at least that was my understanding. Have I misunderstood something somewhere along the line?

>>(the car's the wrong place for an audiophile anyway).

Well, unless you're interested in audio competition. In that circumstance, silly as it seems, quite a lot of time is spent listening with engine off, windows up, and very educated ears (judges) listening for any flaws in the sound quality.

Clarke -- do you have any experience with MP2 vs MP3, particularly with reference to sound quality, or more specifically the loss thereof?

tanstaafl.

"There Ain't No Such Thing As A Free Lunch"
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#719 - 24/10/1999 03:24 Re: What freq can empeg reproduce? [Re: Clarke]
mac
addict

Registered: 20/05/1999
Posts: 411
Loc: Cambridge, UK
pure WAV format - which the empeg can play back without loss.

Actually there's a bug in the player software which means that it can't play wav files at the moment. We hope to address this soon.

--
Mike Crowe
I may not be speaking on behalf of empeg above :-)
_________________________
--
Mike Crowe

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#720 - 24/10/1999 05:49 Re: What freq can empeg reproduce? [Re: BasicGuy]
altman
carpal tunnel

Registered: 19/05/1999
Posts: 3457
Loc: Palo Alto, CA
John did some frequency range testing on the empeg, and the 3db down point was well over 20kHz as I remember - better than the SBlive! card he was using for testing.

Different MP3 compressors, however, do exhibit different cutoff characteristics.

Hugo



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#721 - 24/10/1999 11:51 Re: What freq can empeg reproduce? [Re: tanstaafl.]
Verement
journeyman

Registered: 02/09/1999
Posts: 97
Loc: Boston, MA, US
MPEG audio sound quality is highly dependent on two things: the bitrate, and the encoder. The particular compression layer (I, II, or III) in use will primarily only affect the lowest bitrate you can achieve while maintaining comparable audio quality.

All three layers make use of a 32-band synthesis filter when decoding to produce actual audio samples. The three layers differ in how the subband samples are computed from the bitstream.

Layer I is the simplest; each subband sample is read directly from the bitstream. In Layer II, a more efficient coding scheme is used to represent the samples, but not all subbands can be represented: a limit on the highest possible subband containing samples is imposed depending on the sampling frequency and bitrate. For example, at 44.1kHz, 64kbps/channel (128kbps stereo), Layer II can only encode subband samples for subbands 0-26. The highest subbands (27-31) can never have bits allocated to them at this frequency and bitrate.

Layer III uses the most complex coding scheme and includes additional tricks to maximize use of the bitstream, but the output is the same as it is for Layers I and II: samples for each of the 32 subbands.

All of your audio quality, then, is not necessarily dependent on the particular compression layer in use, but rather on the bitrate and on the quality of the encoder's psychoacoustic model, which determines how that bitrate is utilized. A possible exception here is Layer II because it can never reproduce frequencies corresponding to subbands 30 or 31 at any sampling frequency or bitrate. (I doubt most people would be able to notice, though.)

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