Hey,

I just came across your forum (post : "Regular CDs with lossy compression, Example: Alan Silvestri - G.I. Joe (Score)") while searching for info about a problem I have.

I have a 4000$ soundsystem in my car but I'm finding that the bass is kinda bad in some mp3s. I listen exclusively to mp3s, and I find that SOME (well, mostly) mp3s have very inequal bass frequencies in them. I was told that it was different with original CDs, but I don't have some to test right now.

Does that makes sense? And what solution there is to that? Can I restore/flatten the bass response? Can I try to at least filter out mp3's following the encoder used (if it's SOME encoders that cause the problem) or something else? It doesn't seem to be the bitrate as I was 128kbps files that were making problems, and some 128kbps that didn't.

Or is there a hardware device that can help?

I tried listening to a web radio we have in Montreal that broadcasts the music that plays in nightclubs directly on the web so my assumption is that the *original* signal would be good, and maybe the compression they use (96kbps) is making the problem...

Thanks!!

Alex

No that doesn't really make sense.

@tb87

This part of the message is the most confusing. How did you notice that ?

Because he doesn't have the original sources for comparison, I fear that this discussion will be nothing more than pointless speculation.

In general, unless the mp3 codec was configured with a high-pass or is broken, bass frequencies will not suffer.

What you are really saying is that you have uneven bass in your car. This is normal for a car. Car's have resonances that will enhance only certain frequencies (in fact, any enclose spaces will have this problem, but cars are much worse because they are so small). It probably sounds different for different tracks because the bass notes in one track will hit the resonances, but on another track, in a different key, they won't.

Try playing the original CD's then for shits and giggles?

What kind of music are you listening to? Some recordings/productions have more bass than others. Some modern rap & pop CDs have too much one-note "boomy" bass for my taste.

What do you mean by "unequal" bass?

Is that system designed for "accurate hi-fidelity" sound reproduction, or for "impressive blow out the windows" bass? I assume you have a subwoofer? Some subs are designed for smooth accurate bass, and some are designed for maximum thump. Some vehicles can accommodate a good sub, and with some vehicles you have to compromise.

The bass is the last thing that should be affected by MP3 compression. If these are not purchased MP3s (probably not at 128kpps), it's possible that whoever ripped the CDs to MP3 also made some EQ adjustments to boost the bass, or something... You don't have at least one of the CDs to compare? You spent a lot of money on your sound system, maybe you could buy a CD!

Some sounds/recordings do need higher bitrates than others. Again, I don't think this is causing your bass problem, but 128kpbs CBR (constant bit rate) is on the low-side for high-end audio. Take a look at the recommended settings here. And when you get some time (and some CDs), you might consider performing some ABX tests to find out what bitrate works best for you.

Maybe an equalizer.... maybe your bass control? But, you can't make a bad recording into a great recording... You could also try using an audio editor to adjust the bass in the MP3 file. (Audacity is a free audio editor.) But this may not give you "perfect" results either, and you should generally try to avoid editing MP3s, because it requires de-coding & re-encoding, which means a 2nd lossy compression step.

Are you saying these have the same problem? It could be "anything"... Again, it could be the original recording, they could be using some compression and/or boosting the bass. (Clubs often use various sound processors. Broadcast radio stations use compression and maybe some other processing too.)

@extrabigmehdi
What I mean is that in the middle of the song, sometimes the bass is really low (taking about the level) and then a second later, on the same bass note, it becomes really loud. It can't be EQ, etc. because we're not changing frequency here...

@Iain
Well I know that too much... But I'm not talking about that... See above.

@DVDdoug
It's not the type of music I listen to, it just *really* seems that it's the recordings that are causing the problem. As I said above, the bass suddenly goes up (the level) on the same note. For the soundsystem, my amplifier is an Alpine MRP-M850 and I have 2x Boston Acoustics G5 subwoofers that are supposedly one of the best "sound quality" subwoofers around. The headunit is a Pioneer P980-BT which is a 500$ CD player. Bass is messed up on *certain* recordings only, and from various sources (various websites, different type of sources - whether it be DJ sets, podcasts, singles, ...). Every "enhancement" is turned off on the soundsystem (bass boost on both amp & deck, EQ, ...).

Well I'm more and more considering I should spend money on recordings but I frequently change the music I listen to so it would cost quite a lot But I mean, it's still an option... That's why I wanted to make sure it *was* the recording (made by anyone on the web) that made the problem.

Then I also tried Adobe Audition's "multi-band compressor" to try to compress only the bass frequencies, but it doesn't yield significant results (most of the time it messes up the bass more than anything...) and it's difficult to find some "generic" setting that will make the bass even for every track.

Oh well, I'm still wondering how to solve that one

By the way, I assume that it's specific to my system because a change of X dBs in the bass level on a "regular" soundsystem makes less difference (in term of power) than a change of X dBs over 1000w of bass...

Thanks for your replies so far!

I really think you need to compare your MP3's to the original CDs. You never know what was done to the recordings before it was compressed so while there is a problem, it may not have been the compression that did it.

Alternatively, it may be your system, or some odd effect due to the placement of your subs where they cancel or reinforce certain notes.

Please get an orginal CD of what you are having trouble with and let us know if it persists.

Right... That's not EQ or a badly tuned woofer. That sounds like it's the music. I assume it's the same note(s) every time you play the song. In that case it's the music, not your system. (If it's different every time you play the song, it's your system.)

To some extent that can be normal... Some notes are meant to be accented, or sometimes the bass player just plucks the string harder or softer, etc.

You won't get much sympathy on this forum for downloading poor-quality pirated music. If it's free music that's not pirated, it's probably produced by amateurs.

Of course, you can't tell much without a "known good" reference. The original CD might be just as bad... Who knows??? Half of the battle is putting together a good system, and the other half of the battle is finding good recordings to play on it!

That sounds like the right approach if anything is going to help. But whenever you're trying to fix-up audio, sometimes there's just nothing you can do, or the cure is worse than the disease.

Maybe... For example, a 3dB change results from a doubling of power and we perceive the same 3dB change when we go from 5W to 10W or from 500W to 1000W. However, you may be able to "feel" bass notes that I can't even hear in from my factory car stereo.

Unless you go out of your way to apply a high-pass filter, there should only be one way for the encoder to not pass the bass intact - if it determines that the bass is below the ATH.

This could happen if the bass notes are, in fact, very soft and would not be audible under ordinary circumstances, but you turn up the bass so loud on playback that you make otherwise-inaudible bass audible.

Additionally, if this happened it would be sporadic, as the bass notes rose above and below the ATH.

If this is indeed resulting from low-frequency information being tossed away as a result of lossy encoding, it would suggest that the listening environment has a major imbalance.

As was said earlier, very little is gained by reducing the precision of bass frequencies since they require so few bits relative to other bands to begin with. I'm simply not buying it.

Perhaps we need to change the title of this topic?