Although I found many articles on equalization in this forum, I was not able to find one that directly addresses this legitimate problem or issue that affects not only me but, I imagine, many car owners.
As is typically the case with most car audio systems except perhaps the very newest high end DSP units that offer calibrated microphones and adjust system frequency response based on overall system characteristics (speakers, car interior, etc.), my car stereo offers limited equalization that is totally subjective and based on what sounds “good.” I propose equalizing my system (and I define equalizing as making system response flat or as near to flat as possible so as to reproduce the original source material with minimal alteration) as follows. I will use a Behringer DSP-8024 31-band equalizer with calibrated microphone. This device generates a pink noise signal which it then uses to derive an optimal equalization curve to flatten out overall system frequency response. This technique works very successfully on home stereo systems.
Of course, once I store that “optimal equalization curve” in my Behringer unit (which I believe can be downloaded to a computer) I can either wire the unit into my car stereo system (which is both cumbersome and highly impractical) or use the derived curve to pre-process my MP3s with this curve so that when they are played back over my car stereo system, response is as close to flat as is practicable. It would be possible to “season to taste”, as it were, in accordance with personal taste, using additional equalization or other processing.
My question is, therefore, can anyone describe a procedure to import an equalization curve and then apply it to a library of mp3s?
Thanks,
Wayne
Removed by elf
I pulled your email address from the posting. We get regular scans from spam generators.
It’s just been in the last couple of versions we could save an equilizer curve and email it to somebody. Before that,you were on your own with emailing pictures of the tool layout.
I don’t know what the data format is, however.
Koz
“Import an equalization curve” – it would all depend on how the Behringer unit communicates with the computer and the format of the EQ curve file it generates. Easiest might be to write down the EQ settings the unit suggests and manually enter those into Audacity’s Equalization effect. Audacity EQ curves are stored in XML. These are stored in the same place at Audacity’s preferences http://manual.audacityteam.org/man/Preferences#stored
Equalization is one of the effects supported by Audacity’s Chains feature.
See http://manual.audacityteam.org/man/Edit_Chains and http://manual.audacityteam.org/man/Apply_Chain
– Bill
The options that members have posted to the car equalization problem sound promising but leave open a few unaddressed issues. I have hundreds of CDs which I’ve ripped to MP3 and stored on an SDHC card which I then play through my car stereo. Since there are hundreds of files and they are arranged in a folder hierarchy, it would be extremely cumbersome if not practically impossible to apply a “reverse equalization curve” or any other effects to all of the files manually while still maintaining the Artist > Album > Song hierarchy. Thus, there would have to be some automated means of applying any and all changes equally to all of the files that make up my or anyone else’s audio collection - one that preseves the folder hierarchy.
Notwithstanding that, although I am a hardcore software developer of several decades of experience, and I have experience with audio and video editing, my knowledge of Audacity is mainly limited to using it as a player as I only recently discovered its existence. Therefore, I would ask, if there is a solution to this problem, if there would be someone willing to talk me through the steps in implementing the solution at the most fundamental step by step level. I think that this could help many users.
Thanks,
Wayne Reses
Audacity’s Chains command will not do what you want - it saves the processed files to a new folder (for safety, I suppose) and that cannot be overridden.
What platform are you on (Mac, Windows, Linux)? There may be command-line tools that will do the job.
– Bill
A hardware solution would probably be the best solution. A programmable equalizer to go between the line level output of the player and the sound system amplifier. Perhaps such a thing could be constructed from the Raspberry Pi?
I see two problems right away.
Unless you have an extraordinarily quiet and well behaved car, you don’t want “flat.” You want the equalization, boost and dips that compensate for the road noise, so in that sense, yes, a curve that does that would help. In an effort to make things more convenient than is probably wise, modern car systems also get louder as you go faster. They should probably apply more and more compensation as you go faster.
I’ll let my self out now.
I have hundreds of CDs which I’ve ripped to MP3
That’s the first problem right there. MP3 is a delivery format. Each time you change an MP3 file, the compression damage goes up. Equalization and frequency management of a show will certainly require a re-compression and additional sound damage. We recommend strongly that your library be in a “perfect” format like WAV and you drop down to MP3 for your deliverables like the personal music player you use when you run and the player in the car.
You can get around this a little by making the new music compress at a much higher quality than the old, so the damage hides or only goes up a small percentage, but the small, efficient filesize of your existing library will never be achieved again.
Other than re-ripping the CDs. Never throw out original physical media.
I’m in the equalizer in the car group. Far more straightforward and effective.
Koz
With all due respect, can’t you guys just address my question directly? For example:
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I know that a car interior is an imperfect listening environment - one that is permeated with lots of unwanted noise. If you develop your pink-noise derived “anti-equalization” curve at a typical road speed, you overcome some of this problem. Obviously I’m not proposing a perfect solution but only contemplating one that would get me closer to an ideal environment with the goal of increasing my listening pleasure.
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I know that MP3 is a delivery format. And yes I can hear noise, distortion, and artifacts when MP3s are ripped from a CD or other source at too low a bit rate (like 128K, for example.) That’s why I do my ripping at a sufficiently high bit rate that satisfies my non-superhuman hearing. Without arguing the merits of editing a waveform in WAV format versus MP3, it would be great if you guys could stop arguing and just provide an answerto my questions - if you have an answer.
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I agree that an in-car hardware audio DSP processor would be ideal (and I didn’t miss your changing volume level point) but as I said in my original post, this type of audio processing in 2012 is currently reserved for the most expensive OEM or aftermarket equipment. So at the moment, and the reason why I took the time to post on this forum, I am trying to devise an economical (and perahps clever) practical alternative.
Wayne
P.S. I do not throw my original source material (CDs, DVDs, etc.) away.?. Thanks for pointing that out.
With all due respect, your original question was answered by Bill within 24 hours of your original post.
You then added additional requirements regarding maintaining a large collection of audio files within a complex file hierarchy.
Bill again responded by informing you that this is beyond the batch processing capabilities of Audacity.
In the light of the above, I responded that a hardware solution would probably suit your needs better, which to avoid the expense of a “top end” commercial system could perhaps be an inexpensive DIY unit.
waynewta wrote:With all due respect, can’t you guys just address my question directly?
With all due respect, your original question was answered by Bill within 24 hours of your original post.
You then added additional requirements regarding maintaining a large collection of audio files within a complex file hierarchy.
Bill again responded by informing you that this is beyond the batch processing capabilities of Audacity.
In the light of the above, I responded that a hardware solution would probably suit your needs better, which to avoid the expense of a “top end” commercial system could perhaps be an inexpensive DIY unit.
From Wayne:
I kinda get the impression that you guys are a tight knit group and that you are mocking me. I had a legitimate question. I understand than the solution can be implemented in hardware but that’s not the point. Such hardware could be of a custom DIY design or an OEM calibrated microphone setup with time and equalization correction. This is an Audacity forum so naturally I wanted to know if there might be a solution that could be implemented in Audacity. As for the notion that I “added additional requirements…complex file hierarchy” (that’s why I included your quote above,) I didn’t add any requirements. I don’t want this conversation to break down into one involving irrelevant semantic issues but, for whatever it’s worth, I mentioned maintaining a large MP3 library in my very first post. I’m sorry that I didn’t use the word “hierarchy” but most music is organized this way on a computer. You guys know that.
Wayne
I believe he did.
Easiest might be to write down the EQ settings the unit suggests and manually enter those into Audacity’s Equalization effect. Audacity EQ curves are stored in XML. These are stored in the same place at Audacity’s preferences > http://manual.audacityteam.org/man/Preferences#stored
You only have to do that once, save the curve and then use the Audacity Chains system to apply it to as many songs as you want.
The problem is nobody knows the format of your equalizer, so making that one step painless is problematic. It’s easiest to go from the graphic of your equalizer tool.
Koz
Not at all. The people that post regularly on this forum are just Audacity enthusiasts that give some of their spare time to try and help other Audacity users. Koz lives on the other side of the Atlantic from me - I’m not sure where Bill is located, I just know that both of them have given a great deal of their time and experience to try and assist their fellow Audacity users.
The requirement to maintaining the directory hierarchy is crucial, and a deal breaker for Audacity. Audacity has some ability for batch processing, but the processed files of any one batch are always written to one output folder.
Sadly I don’t know of any program that is able to fulfil your requirements.
The best that I can think of is to use SoX to pipe a series of filters (SoX does not have a graphic Eq effect) and write a custom script yourself to recursively step through the folder hierarchy from the top level down.
Another alternative would be to build Audacity from the source code and include the experimental mod-script-pipe module. Then write a script in your preferred language to pipe the files through Audacity.
Neither of these suggestions are easy options and personally I’d go for the hardware route.
How about considering an iPod with an in-car dock as a solution?
My iPod has a full set of pre-set EQ “curves” - ok so you can’t set your own one and there are only a limited number of “sliders” - but there are plenty to choose from.
And what’s more iTunes on your computer will manage the storage hierarchy for you.
WC