mp3 query: spectral rehab?

nomos

Administrator
A while back a posted a question about the sonic qualities/faults of mp3s as digital "DJ" fodder, whether in a club space or a mix. I'm still trying to sort these things out.

My question, for any DJs/engineers/bass materialism theorists out there, is: what sonic features are really lost in the mp3 encoding process and is it possible/necessary to resuscitate files encoded at moderate (160kbps) to high bitrates (192-320kbps)?

I know vinyl is always better < / mantra >, but it's not always available or affordable. Furthermore with labels like Hotflush offering tracks on a pay-per-download basis through DJDownload and Karma, it's becoming increasingly feasible/ethical to move to purely digital mixing if you're so inclined.

I've heard varying reports about the damage done to sound through encoding. (Tekno) Plastikman says it's not a big deal to play mp3s on a large soundsystem. Others say its crap. Grime and Dubstep people seem to say that too much bass is lost. I'm not certain that bass levels actually decline unless the encoder is set to cut frequencies below 20 Hz (as in iTunes). Bass density does suffer, however, since the compression is based largely on filtering out "redundant" frequencies (a purely subjective take on psychoacoustics that's built into the codec). High end deterioration is a different story as it often gets mucky below 192 kbps.

So I'm interested in hearing from people who've used higher-quality mp3s in settings where loss of bass or clarity might have been easily recognized.

I'm semi-considering trying out an Aphex Aural Exciter 104 or 204. The marketing material says that it infers harmonics in the high and low ends and synthesizes the lost sonic density. Supposedly, good results are to be had even with low bitrate audio. Anyone know about this?
 

lush

Member
I'm no audiophile, but I do play exclusively from mp3 tracks downloaded from the likes of DJdownload and Beatport.

I play a mixture of house, electro and breaks and I can't say I have ever had an issue. I do try and improve the quality of the music by only using music that is encoded directly from the DAT, running everything through a neat little tool called MP3Gain and then applying a compressor to the tracks when I'm playing live.

I know of others who also tweak like heck with other plug-ins (paramEQ etc.) but I have not tried that myself yet.

I can't say anyone has ever commented on the quality of the music, but then again the soundsystems I have played on were not really of good enough quality to notice. CD and mp3 recordings of my mixes through some pretty good home stereos and ICEs offer no loss of quality to my ears, or those of my friends (but again none of us are properly into sound quality).

If you think it might help I can send you a CD of the type of output I'm getting?

Edit - I never play less than 192k and most sites offer 320k so I have a good cross section of those.
 
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nomos

Administrator
Sorry, lush. I was in another dimension for a bit.

This Mp3Gain tool looks handy. I wish they had as many gizmos for Mac. I do tend to do a lot of EQing but then I often hit a point of overkill, or highs that are just too noisy.

I suppose you're right, that it largely comes down to the system you're playing on. Any place where I might play out locally wouldn't really put these spectral issues to the test. I've listened to the vinyl and mp3 portions of the last mix I did, comaparing the original AIFF to the mp3 copy in my monitor headphones. I really can't say I notice a difference. But I'm interested in running the same drill through a decent subwoofer.

If I can find any more info about the Aphex unit I'll post it.
 

lush

Member
The gain software is vital, the variation in volume between tracks can be anything up to 10db. It really makes a difference to the ears.

Dave Clarke is on record as saying MP3s limitations can be heard on a 'proper system' and I suppose he would know more than anyone.
 
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