Equalization less capable under Mac OSX?

I have an equalization curve for 24/192 files which I use to very good effect in a chain in Audacity 2.0.2 under Windows 7, but I cannot create the same, or even a fairly similar, curve in Audacity 2.0.3 (installed from the dmg file under the latest Mac OSX Mountain Lion) on a MacBook Pro. The combination of about 8dB of bass cut at 90Hz with a very steep recovery in both directions (back to zero at about 60Hz and 130Hz respectively, as shown by the fine green line) just seems to be impossible to achieve on my Mac. As I do all my recording on the Mac (so that I can use an Apogee Duet 2 USB audio interface) this means that I have to transfer all my flac files to the Windows computer in order to equalize them to suit my loudspeakers (Quad ESL 57s) before finally transferring them to the NAS drive connected to my audio system. Is there any way around this? For example, is it possible to save some sort of data file representing the curve on the Windows machine and use it to create the same curve on the Mac? Or is there perhaps an Eq add-in that provides much finer control than the one provided by default? Although the present workaround is effective, it is rather slow and clumsy…

I don’t think that the Equalization effect has changed since Audacity 2.0 came out. Perhaps you have moved the “Length of Filter” slider.
To make the green line follow the blue line more closely, move the “Length of Filter” slider to the right (longer filter). Moving the slider too far to the right may adversely affect “pulse response” (a slight ringing on transients if there is a sudden jump in the filter) but it does not sound like that is relevant to your specific case.

Did you try to export your known, good, working filter (as I think an XML file) and import it into the new Audacity? That’s not particularly straightforward, but it does work and you will not have to juggle settings.


Many thanks, steve. However, I always move the slider all the way to the right for the LF cut curves, otherwise I can’t get anywhere near the ball park at all. A good thought, though…

Many thanks, Koz. I haven’t tried that - do you know where I can find the method? It would be great if the filter I use under Windows could be imported into the Mac installation - though the Eq curves do seem to work quite a bit differently under the Mac, so perhaps it might still not put that elusive green line quite where I want it…

That could be a bug. As far as I’m aware they should be the same, but I don’t have a Mac to compare.
Could you post a screen shot to illustrate what is happening on your Mac.

Note that there is a known bug in the current version in which curves are not converted accurately when switching between “Graphic” and “Draw” modes.

Instructions for importing /exporting Eq curves are here: http://manual.audacityteam.org/o/man/equalization.html#manage

For most purposes (for example, if you want to reuse the curve you just applied, or import a curve) don’t use “Draw Curves” in 2.0.3.

Correction: The bugs are with

  • switching between Graphic EQ and Draw Curves Mode
  • applying an EQ starting in Graphic EQ Mode and then reopening EQ and reapplying the effect (the slider values have changed)

A fix for these problems has been committed at r12290 ( http://code.google.com/p/audacity/source/detail?r=12290 ) .


Many thanks steve and Gale. I have imaged and exported the curve from the Windows machine - I’ll see what happens when I import it under Mac, and I’ll post screenshots as soon as I find the image editor (or maybe install one?) on the MacBook…

Hey Gordon,
If you press command+shift+4 the screen grab cross-hairs dialog will appear in place of your mouse cursor. Now hit the space bar and a camera icon will replace the cross-hairs. Move the camera cursor over the eq dialog window you want to grab (it will appear sort of greyed out when you do) and tap the track pad or click your mouse and a screen shot of that window will be saved on your desktop.

Many thanks, Mr. Pickles. I’ve actually just been doing that, and I found I could re-save the screenshots (which don’t seem to have a file extension) as .jpg files by opening them with ColorSync Utility → Save As. I’ll upload the results in my next post…

Very interesting… importing the curve exported from the Windows machine into Audacity on the Mac worked perfectly (many thanks again!) as can be seen from two of the attached screenshots.

However, attempting to CREATE the same curve by using the same points to draw a curve in Audacity under Mac in fact creates a completely different curve, as can be seen in the other attached screenshot.
Eq Curve created with same points under Mac OSX.jpg
Eq Curve imported under Mac OSX.jpg
Eq Curve exported under Windows 7.jpg

Incidentally, the curve I created under Windows and imported to my MacBook was created in Audacity 2.0.2, whereas the version of Audacity on my MacBook is 2.0.3. Perhaps this means that the problem with “Draw Curves” in version 2.0.3 could routinely be worked around by keeping version 2.0.2 handy on another computer, as in the case just posted above, at least for the time being…

Thanks. That appears to illustrate a bug.
Interestingly, on Linux I’m getting a green line that follows the blue line much more closely than either your Windows or Mac screenshots.

Could you post the XML files for both machines.
test.xml (637 Bytes)

When I commented on the current known bugs in EQ in 2.0.3, I said “Draw Curves” when I meant “Graphic EQ”, which I’ve corrected now. Sorry about that. A potential fix for those bugs has now been committed, which seems to restore behaviour to 2.0.2 accuracy as far as I can tell so far.

Using a filter length of 8191 and importing Steve’s test XML file, the green line curve has the same good fit for me on Windows 7 (Audacity 2.0.3 release and "fixed " 2.0.4 alpha) and Mac OS X 10.8.3 (Audacity 2.0.3 release).

If you (Gordon) can post the XML file you created using 2.0.2 on Windows I will try creating that curve on Mac and Windows.


Steve, are you working with a 192KHz file open? I find that the green line matches drawn curves very closely with 44.1KHz files, reasonably closely with 96KHz files, and not closely at all with 192KHz files. By the same token, I find that, if a curve made for 44.1KHz files is applied to 96 0r 192KHz files, it doesn’t work as expected at all - so I always name my Eq curves with a name that includes the sampling frequency they were made under, because that seems to be the only sampling frequency they will work properly with.


Many thanks again, Gale. Here is the XML file I exported from 2.0.2 under Windows and imported into 2.0.3 under Mac OSX. (It only creates the equalization I need to flatten out the room interaction with my speakers when applied to 192KHz files - I use very different curves to create approximately the same equalization with 44.1 or 96Khz files).

Quads(24-192)2.xml (751 Bytes)

On Windows, there is no difference between 2.0.2, 2.0.3 and 2.0.4 alpha that I can see - whether importing that XML file or drawing its EQ points, the green line needs the maximum filter length to fit closely at 44100 Hz project rate, at 8000 Hz it fits closely with as short as 2500, and at 19200 Hz or higher the fit cannot be made tight (by tight, I mean that the line appears green or blue/green).

I’m out of time to test on Mac until later, but even if there are Mac differences between 2.0.2 and 2.0.3 as seen in your images they are slight in comparison to the sample rate differences. I did not know that relationship existed, so I’d be interested to read Steve’s comments.


Ah ha! That explains it :smiley:

The “Size” of the filter is the “FFT window size”. That is the number of samples that are used in each (overlapping) analysis window.
The larger the window is, the greater the accuracy of the filter at low frequencies.
The low frequency accuracy is limited by the FFT window size.

If a high sample rate is used, then the length of each window in seconds becomes much smaller (1024 samples at 44100 Hz sample rate is about 0.023 seconds, but at a sample rate of 192000 Hz it is only about 0.005 seconds.

Unfortunately you can’t just keep increasing the window size, because some of the calculations become increasingly less accurate unless the calculations are performed in much higher precision. Currently I think Audacity uses 64 bit precision for these calculations, so the maximum window size could perhaps be increased to a bit more than the current “8191” maximum, but there is another down side, which is that as the window size increases, so the pulse response becomes worse, which can cause “ringing”. For FFT filters there is a trade-off between sample rate, frequency precision, and time precision. If any two of these are increased, the third must be reduced. FFT is a remarkable piece of mathematics, but it has its limits.

As it looks a bit like a “bug”, I added a sentence about this to the Manual .

No doubt you’ll correct/improve it if needed.