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AudioSpectro FIRE- Frequency Balance Tool for Audio Mastering

AudioSpectro FIRE (Flat and Intelligent Response Equalization) is a tool that can be used to solve problems involving frequency balance in audio mastering process. This works by comparing the mix with a test specification data gathered from industry-standard/broadcast quality mixes/masters.

It provides an easy to understand rating system and recommends objective EQ tweaks based on the analysis. The objective is to attain a flat equalization response (“frequency balance”) that makes your mix comparable to the sound of today’s modern mixes.

This is an indispensable tool to any home studio producers/engineers in assessing the frequency response of their digital audio mix down. This uses FFT data analysis technique that prevents external factors (e.g. room acoustic response) to affect the EQ setting accuracy. The following are example applications:

a.) Improve and assess your stereo audio mix down using frequency analysis techniques
b.) Getting the right bass level in audio mastering. Not only bass but mid and high audio frequency as well.
c.) A powerful confirmation tool in your DIY audio mastering.

Of course, this is not designed to substitute poor listening skills but think of this as your “ears” training partner in sculpting your mix audio frequency response to perfection.

Mastering BEFORE and AFTER Examples: Illustration using AudioSpectro FIRE

In this illustration, you will learn how to attain frequency balance during audio mastering using AudioSpectro FIRE. To start with, download the latest version of the tool here:

(Latest version: 1.4, November 6, 2012)

After that, you could also download the audio demo and analysis files (Right click- then save as. Size: 237MB) used in this tutorial. Unzip it and use it as a guide. This is only used for practice and learning purposes on using this software. But don’t use the spreadsheet analysis provided by the demo files as it is not using the latest version. You need to use the latest version of this tool (version 1.4) in your own practice and evaluation.

Note: The WAV files in the demo are in 32-bit float/44.1KHz format because they are recorded in Adobe Audition 1.5 some years ago that uses 32-bit float as an equivalent bit depth of 24-bits. Read more about this equivalence in this tutorial.

This is how the original raw mix down would sound like before audio mastering process (normalized to -20dB RMS):

Step1.) Listen and define the problem objectively

First; I play the raw mix down audio file (Refer to High Resolution WAV Files– > CanIknowYourName-BEFORE EQ.wav in the demo files); a few rounds on my studio monitors to check for problematic frequencies while monitoring at average volume.

The audio mixing is reasonably well-done. This means the effects implementation, stereo imaging, recording quality and instrument levels sounds OK. So obviously I don’t think remixing or re-recording is required here. I noticed the following frequency balance issues after this listening test:

a.) The track lacks mid-frequency “presence” compared to the bass. Lack of presence is a common problem for tracks before mastering. However this aspect is particularly important for pop/ballad and country genre type.

b.) It also lacks brightness in the audio high-frequency range.

This makes the bass sounds more dominant in the overall mix while drowning the mid to high audio frequency response. In other words, the frequency balance is not good.

Before I start implementing some EQ settings; I need to confirm these problems using AudioSpectro Fire to get some objective view of the problem. AudioSpectro FIRE need some data input about the track. This data needs to be generated using Audacity and TT Dynamic range meter software, for procedure refers to the sheet named as “APPENDIX A. Generate RAW Data” in the tool.

After generating the RAW data of the mix down (Refer to Raw data generated — > raw data- BEFORE EQ.txt in demo files), the analysis can now be started. I paste the data on “STEP 1.) Raw Data” and the software automatically validate the input data.

There is no validation error so I can safely proceed to the analysis (Refer to AudioSpectro FIRE analysis workbooks — > Analysis on Original MixDown BEFORE EQ). I clicked “View the analysis summary of this analyzed audio” link and the summary is provided below:

analysis summary

It shows a frequency balance rating of 52% which is very far from the normal scores ideally starting at 80% above (For details about the rating system, please read “Frequency Balance Rating Guide” sheet in the tool). This implies some issues pertaining to the overall frequency balance.

Step2.) Digging Deeper using Frequency Band Analysis

Since the rating is unsatisfactory, I dig deeper into the problem and click the “Frequency Band Analysis Results” for details. I start with the bass frequency response. As I’ve expected it’s normal:

Bass response

It shows that the analyzed audio (track I’m working on) is within the bass specification limits of targeted response. Although there are points that exceed specifications, the overall response is still OK and normal. There is nothing to tweak on this frequency range.

Now I clicked “Mid (201Hz to 500Hz)” response plot and this is the result:

Mid frequency

It says 36% of mid-frequency response falls below specifications. I specifically highlighted the majority of the problematic sections in dotted orange box.

This is somewhere around 800Hz to 3200Hz.

For the high audio frequency response (refer to “High (5001Hz to 13500Hz)” sheet), it even reveals more issues such as shown below:

High-audio response

There is wide and weak high-audio frequency response just what I’ve suspected before doing the analysis (during the listening session). The problem is wide; starting at 5000Hz all the way to 13000Hz.

Following the workflow (see “Appendix D. Workflow” sheet in the tool); it does not need re-recording or remixing because I think these EQ issues can be resolve in audio mastering. The analyzed audio frequency response does not deviate very far from the specification limits so some EQ adjustment can fix this.

Let’s start.

Step3.) Formulate EQ adjustment settings

In “Appendix F. EQ examples” sheet; you can find lots of information on doing EQ adjustment examples based on the frequency response plot.

Let’s follow the solution steps:

1.) Identification of problem frequency range.

a.) Weak mid-frequency from 800Hz to 3200Hz
b.) Wide and weak high-audio frequency response from 5000Hz to 13000Hz

2.) Estimating the amount of cut and boost

Since all the issues are weak frequency response, I would only be doing boosting here and no cut. Based on the plot, I would like to implement the following boost settings:

For weak 800Hz- 3200Hz mid frequency range= +2.0 dB boost
For weak 5000Hz to 13000Hz high-audio frequency range= +3.0 boost

I encourage you to read “APPENDIX E. Best EQ practices” sheet, for more details on doing EQ settings.

3.) Computing the center frequency, Q, and output compensation gain.

I then proceed to “My_EQ_ADJUSTMENTS” sheet to input the above values. This is how it looks like:

EQ settings

EQ settings#1 (correcting weak mid-frequency response):

Center frequency= 2000Hz
Q= 2.5
Estimated Boost= +2.0dB
EQ output gain compensation= -1.3dB

EQ settings#2 (correcting weak high-audio frequency response):

Center frequency= 9000Hz
Q=3.4
Estimated Boost= +3.0dB
EQ output gain compensation= -2.0dB

Output gain compensation is used to prevent your track from gaining undesirable loudness from EQ boost. This can result to distortion. Most parametric EQ tools are equipped with this feature such as Waves Paragraphic.

For more details, read the “EQ_Output_Compensation” sheet in the tool.

At this end of this step, I finally obtain the EQ settings necessary to balance the frequency response of the track.

Step4.) Implementing the EQ settings

I then open the high resolution WAV mix down (In the demo files: High Resolution WAV Files– > CanIknowYourName-BEFORE EQ.wav) file in my audio mastering software (Adobe Audition 1.5).

I use Waves Q1-Paragraphic to implement each of the EQ settings one by one. These are the Q1 EQ screenshots:

For EQ settings #1:

EQ#1

For EQ settings #2:

EQ#2

There is some small drop in loudness of the adjusted track after EQ settings. This is OK. After implementing the above EQ settings, I immediately save it with a different file name (Refer to High Resolution WAV Files — > CanIknowYourName-AFTER 1st EQ.wav). When saving the file, I use the same bit depth and sample rate as the original mix down.

I played the track a few rounds to examine the changes in the frequency response and I noticed some improvements this time:

a.) The mid-frequency response is now cutting clearly.

b.) The high-audio frequency response is brighter than the original mix down.

But for me, it still lacks that “little” presence on the mid and high to get that perfect sound. This is how it sounds like after EQ adjustment at the same -20dB RMS volume with the original track for clear A-B comparison:

How about doing a confirmation with the AudioSpectro FIRE tool?

Step5.) Measuring the Frequency Balance Improvement after EQ

I repeat the entire raw data generation process using the WAV output (CanIknowYourName-AFTER 1st EQ.wav) of the EQ adjustment process. You view this data in the demo files: Raw data generated — > raw data- AFTER 1ST EQ.txt.

The frequency balance score increases from a low 52% to 78%, an improvement of 26%.

frequency summary

Specifically:

1.) The mid-frequency range improves from 36% to 23% below specifications. The remaining problem frequency range is highlighted in dotted box.

problem range

2.) The high-audio frequency range improves from 67% down to 21% below specifications.

problematic high-freq

Can this be further improved? Yes of course.

Step6.) Implementing Further Improvements on Frequency Balance

Using the “My_EQ_ADJUSTMENTS” sheet on the tool, I inputted the remaining problematic frequency range with the desired gain and the recommended settings are shown below:

recommended values

Then I open again the EQ-adjusted WAV file (CanIknowYourName-AFTER 1st EQ.wav) in my audio mastering software and implement the above EQ settings using Waves Q1 paragraphic.

I give it some time to listen to the track after EQ tweaks and indeed it now sounds great to my ears the first time. I then save the WAV output of this 2nd EQ adjustment with a different file name (refer to High Resolution WAV Files — > CanIknowYourName-AFTER 2nd EQ.wav) but retaining the same bit depth and sample rate.

I generate another set of raw data using the adjusted file: CanIknowYourName-AFTER 2nd EQ.wav. You can view this data in the demo files: Raw data generated — > rawdata-AFTER 2nd EQ.txt. And finally, the frequency balance rating increases to 86% and everything else (the bass, the mid and high) appears normal. For details on of this result, please refer to “Analysis on Original MixDown AFTER 2nd EQ.xls” in the demo files.

Final response

This is how the final mastered track would sound like after the 2nd EQ adjustment (with Waves L1 limiter plug-in applied):

This is how it sounds like without the limiter and normalized to -20dB RMS (for A-B comparison with the previous examples).

You can practice with the audio files provided with the demo to see if you come up with the similar results using your own tools.

Once you get to know the process very well, you can then start improving the frequency balance of your own mix down. Using AudioSpectro FIRE removes a lot of guesswork in the frequency balance adjustment process.

DIY Audio Mastering Process with AudioSpectro FIRE

Using this tool, you can easily implement a simple audio mastering process such as:

Raw mix down (e.g. 24-bit/44100Hz WAV) — > EQ (Frequency Balance Adjustment with AudioSpectro FIRE) — > Limiting process

Assuming you have a well-crafted mix, all you need to do is to implement frequency balance first then apply a conservative amount of limiting using your favorite limiter plug-in (e.g. using Waves L1) to attain the final desired loudness and you are done with your mastering.

I recommend targeting DR11 or DR12 dynamic range (after limiting) for best results as discussed in this tutorial on creating radio-friendly mixes. You can of course make your masters even louder (e.g. DR 10 and above) but you risk losing the original dynamics.

With this recommended process; you have implemented minimal digital audio processing in mastering that preserves much of the quality of the original mix. For distributing the final masters based from high-resolution WAV master (e.g. 24-bit/44100Hz), this is my preferred flow:

Distributing as high quality MP3 masters (320kbps)

MP3 masters

The above is the optimal process based on this research.

Distributing as 16-bit/44.1KHz audio CD master:

CD master

Another Frequency Balance Illustration

This is not included in the demo files, but let’s illustrate another example. Listen to the raw mix down below before mastering:

Basically, the frequency balance rating before EQ is already around 85%. The only problem after listening the track seems to be a lacked of mid-frequency presence. This has been confirmed by AudioSpectro FIRE with 37% of mid-frequency response falling below specifications (inside the orange box):

spectrum response before adjustment

The affected frequency range is around 1200Hz to 4600Hz; approximately this needs a boost of around +2.5dB. The following are the final EQ settings formulated with the help of the tool:

Center frequency: 2900Hz
Q= 2.6
EQ Gain: +2.5dB
Output gain compensation: -1.7dB

After implementation, there is a significant improvement in the track frequency balance. The final rating is at 91%. You can listen to the two samples below after the EQ adjustment:

Normalized to -20dB RMS:

With limiter applied:

Benefits and User Feedback

The following summarizes the most important benefits on using AudioSpectro FIRE with your project:

1.) Identify frequency balance issues objectively in your mix.
2.) Accurately identify problematic frequency range in your mix that would be difficult to confirm with listening or in a limited monitoring environment.
3.) Assist in formulating EQ tweaks to get a professionally sounding finished master.
4.) Objectively compare your mix to broadcast quality/reference tracks.
5.) This is a perfect confirmation tool (used along with your ears) in monitoring problematic frequencies during the mix down and mastering.
6.) It provides lots of easy-to-understand information about the frequency response of your mix.
7.) It minimizes the guesswork when doing EQ adjustments during mastering.
8.) This tool uses FFT data analysis techniques that prevent external factors (room acoustic response, external noise, etc.) from affecting the accuracy of EQ adjustments.
9.) It will help in documenting your work progress by saving analysis results in the form of spreadsheet data and text files.

User feedback: Since this tool is new, here’s some of the initial user feedback on using AudioSpectro FIRE:

“I have been using this tool, somewhat different than the outline, but very much inline with the objective. It really is a good starting point on understanding the mastering process. I am seeing a lot of issues with my mixes and the corrections make a huge difference!

Thank you for providing this tool…”

“…Now, all of my cuts are consistent, no more worrying about of the loudness, too much bass, etc. It really is a GREAT tool for all of us beginners to produce clean professional sounds. Now I just have to focus on mixing :).

Thank you very much for this tool!”

by: David M in Google+

Download and Purchase a License

You can download the latest version of AudioSpectro FIRE (right click and save as):

(Latest version: 1.4, November 6, 2012)

Tested/Recommended Compatible Software:

1.) Windows operating system with MS Excel (At least Version 2002 or 2003)
2.) Windows OS with Calc Open Office version 3.4.1
3.) Linux operating system with Libre Office Calc (version 3.5.4.2)
4.) Audacity (Linux and Windows version) version 2.0.2 (as of November 2012)
5.) TT Dynamic range meter – in Windows and Linux. Use Wine to run this software.
6.) Plugins – Waves EQ plugins (fully tested and working).
7.) Other EQ plugins – refer to user notes under “My EQ adjustment sheet” in the tool.
8.) Audio mastering software – compatible any mastering software

The software package for evaluation is complete with all the required documentation (generating raw data, etc.), EULA (End-user license agreement) and helpful-guide/tips. It is a fully working version.

After downloading, unzip the package. You will see four folders inside the main folder. These are as follows:

a.) Documentation– complete reference and manual of the software.
b.) Libre Office Calc for Linux – use this version if you are in Linux.
c.) MS Excel Windows – if you are using MS Excel as your spreadsheet solution.
d.) Open Office Calc – if you are using Open Office as your spreadsheet solution in Windows OS.

Before purchasing a license, I recommend you fully evaluate AudioSpectro FIRE in your projects for 30 days. I also encouraged you to read the EULA for the terms covered by the license. And if you finally decide to use this software for more than 30 days, you should purchase a license.

There is only one type of license offered:

$39.95Single-user for both personal and commercial use.


You can also purchase license directly from the tool, go to EULA sheet and you can find the PayPal link.

Support for non-profit software: The developer will be donating 5% of sales to Audacity and The Pleasurize Music Foundation. AudioSpectro FIRE uses these tools to generate raw data for the analysis.

TIP: Organizing your Files

It is essential to organize analysis files and raw data to avoid getting lost in your audio mastering process. I recommend that you create a dedicated folder for each song with analysis folders inside like this:

structure

Where:

a.) 16-bit masters– folder containing the finished product: 16-bit/44.1KHz WAV master.
b.) 16-bit raw data -this is the folder where you will be placing your raw 16-bit files for volume analysis (the one exported by Audacity). To organize file names, I recommend the following:

songtitle_beforeEQ.wav – this is not yet applied with EQ
songtitle_afterEQ.wav – applied with first EQ
songtitle_after2ndEQ.wav – applied with second EQ

c.) 24-bit mixdown -this the folder where you will place your 24-bit files. You can use the above naming conventions also to this folder like:

songtitle_beforeEQ.wav – this is the original 24-bit file not yet implemented with EQ or mastering effects

d.) 320kbps MP3 masters -your high quality MP3 master will be placed on this folder.
e.) after limiter 24-bit masters – once you have completed the EQ adjustment you can implement limiter. The limiter applied 24-bit master will be placed on this folder.

f.) audioSpectro FIRE analysis -folder where you will be placing your analysis Excel files from the tool. For example:

songtitle_after2ndEQ.xls – this is the audiospectro FIRE analysis file after second EQ.

g.) mp3 raw data – folder containing your 128kbps mp3 files for raw data generation.
h.) raw data text files – you will place all generated raw data text files in this folder.

A big advantage of this workflow is that your entire work will be documented. You have all the necessary data and files you have created during the mastering.

Project Credits

Developer/Creator: Emerson R. Maningo
Website: https://www.audiorecording.me/

This project would not be possible without the following important software:

TT Dynamic Range Meter by The Pleasurize Music Foundation
Website: http://www.dynamicrange.de

Audacity by the Audacity Team:
Website: http://audacity.sourceforge.net/

Voxengo R8brain by Aleksey Vaneev
Website: http://www.voxengo.com

LAME MP3 by Lame Developers
Website: http://lame.sourceforge.net/

Changelog

November 6, 2012 – Version 1.4 – This is a major upgrade of the software with the following important changes:

a.) Improve the output gain calculation algorithm by providing two sets of values (max and min) to compensate increase of loudness due to EQ adjustment. You only need to select a value between this range.

b.) Provide a complete documentation of each specific task in PDF files.

c.) Improve compatibility of the software to Open Office and Libre Office spreadsheet solutions.

d.) Improve calculation accuracy of desired EQ settings.

October 16, 2012 – Version 1.3 – Update tool source code for compatibility with Linux operating system. Add user notes on “My EQ adjustment” sheet pertaining to Q setting accuracy. Add some notes on “EQ Output compensation” sheet pertaining to gain adjustment of quiet mixes.

October 9, 2012 – Version 1.2 – Change raw data generation process to use TT Dynamic range meter instead of REAPER. This is an easier and more flexible method.

October 8, 2012 – Version 1.1 – Original version.

Content last updated on November 6, 2012

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