Although there are dedicated products for noise reduction from brands like Cedar, iZotope and Accusonus, for some they prefer the price and performance of using a multiband dynamics plugin set up as a downward expander. In this article, we explore the techniques and find that there are some very cost-effective solutions available.

There are a number of multiband-dynamics plugins that are not only compressors but can be re-configured as downward expanders, making them suitable as background noise reduction tools.

What Is Downward Expansion

When using Expand mode in combination with a negative range, the signal will be attenuated as soon as it drops below the threshold, increasing the perceived dynamics of the signal around the threshold. This is the most common type of expansion and with higher ratio and range values, it moves closer and closer to being a gate.

Waves C4 Multiband Compressor

For this article, we are going to show you how this technique works using the Waves C4 multiband compressor, which can be configured as a multiband expander.

The key with the Waves C4 is the principle of low-level gain and high-level gain. In the Waves C4 plugin, gain is applied to the low-level signals, and Range is added to it on high-level signals.

To set up the C4 as a 4-band noise reduction processor:

1. Find a section of audio where only noise is present, and loop it for preview.

2. Listen to each band of noise separately (using Solo) and determine the amount of noise reduction you want to apply to this band. Set Gain equal to the amount of noise reduction wanted in each band (a negative value).

3. Set Range to exactly compensate for the gain reduction in low levels — that is the Range should be exactly the inverse of Gain (if Gain=-12dB, Range=+12dB).

4. While previewing the noise segment, set Threshold in each band such that it is just enough above the noise energy in this band, so that you hear enough noise reduction in that band.

5. It will be useful here to use a hard Knee setting (set the Knee control in the Master control section to its maximum).

Now preview an audio segment where the wanted signal is present, and make sure it is indeed enough above the Threshold(s) so that no gain reduction takes place (the yellow line is at 0dB gain).

Pay special attention to the problematic passages, where the signal fades out or other soft sections where the audio comes closer to the noise level; careful adjustment of Threshold is required there to avoid too much degradation of the signal itself.

To help you we have come across this excellent video from YouTuber Thomas Boykin in which he shows how to use Waves C4 plugin for dialog broadband noise reduction as an alternative to CEDAR or iZotope RX…

You can even download a preset created by Thomas to get you started.

Get The Waves C4 Plugin For Just $29.99

Right now you can get the Waves C4 or its bigger brother the C6 with six bands instead of 4 very cost-effectively, with Waves C4 currently priced at $29.99 instead of the normal price of $149 or the Waves C6 currently priced at $35.99 instead of the normal price of $299.

The Waves C4 is also included in a lot of the Waves bundles, so some of you may already have this plugin in your plugins folder. If not then the C4 is included in the Gold Bundle, which is $179 at the moment instead of $799, as well as all the bundles above, like the Diamond, Horizon and Mercury bundles as well as the Sound Design Suite, priced at $229 at the moment.

It Works With Other Multiband Processing Plugins

The principles we have shown do apply to other multiband dynamics plugins as long as they can be reconfigured as multiband downward expander plugins. These include, but not limited to, FabFilter Pro-MB, McDSP ML4000 Mastering Limiter and the Metric Halo MH Multiband Expander.

FabFilter Pro-MB

FabFilter Pro-MB can apply any kind of dynamics processing per band, using the Dynamics Mode buttons in combination with the Range knob. When the Dynamics Mode is set to Compress, use either a negative or positive range to apply downward (normal) or upward compression. The same applies to Expand mode giving us the downward expansion mode we need for this application.

FabFilter Pro-MB Tips

• If multiple bands are selected, the band controls will adjust all selected bands simultaneously.

• The Pro-MB offers MS processing which gives you more options when processing background noise.

  • If you hold down the Alt key while dragging a band's Output Level knob, the Output Pan ring will simultaneously be adjusted in such a way, that make-up gain is applied according to the current Stereo Link Mid-only or Side-Only processing amount.

  • For example, when using 100% mid-only processing, holding the Alt key while dragging the band's Output Level to +6 dB, will also set the panning to "-6 dB Side". This ensures the side signal stays unchanged, only adding make-up gain to the mid signal.

• You can choose to use Lookahead or not. If lookahead is disabled, oversampling is turned off, and the processing mode is set to Dynamic Phase or Minimum Phase, FabFilter Pro-MB works without any latency. When lookahead is enabled, the latency will be 20 ms, plus possible additional latency for Linear Phase processing and oversampling.

Price

The FabFilter Pro-MB is priced at $199. You can also get in some of the FabFilter bundles starting at the Mastering Bundle, priced at $499, the Pro Bundle priced at $739 as well as the FX Bundle and Total Bundle.

McDSP ML4000 Mastering Limiter

The McDSP ML4000 Mastering Limiter is actually a bundle of 2 plugins, with the ML4 being the multiband variant. The inclusion of the Limiter in the plugin title is misleading as the ML4 is a multi-band dynamics processor that includes a 4-band Gate, Expander (upwards or downwards), and Compressor.

Each band’s Gate, Expander, and Compressor can be configured separately or linked together. Steep 24 dB/Oct crossover filters minimize signal leakage into adjacent bands.

Price

The native version of the McDSP ML4000 is $149 and the HD version for DSP plugin processing is $199. You can also get the plugin as part of the Emerald Pack, which is priced at $599 for the Native version and $849 for the HD version.

Metric Halo MH Multiband Expander

Multiband Expander is a dedicated plug-in, designed to enable you to manage, suppress and control noise in your tracks in a frequency-sensitive way. It’s a 3 band processor, which may not be enough on some more problematic audio but it does Multiband Expander features SpectraFoo™ spectral analysis to allow you to zero-in on crossover points and thresholds quickly and with confidence.

The Multiband feature of the expander is extremely useful for controlling noise and hum in guitar tracks, as you can attack the noise more aggressively than the desired signal. When Grammy Nominated Engineer Ariel Borujow used the Production Bundle to mix Charlie Red, he found that the tracks were noisy at times and he was able to use the Multiband Expander to carve out the noise.

Price

The Metric Halo MH Multiband Expander is $179. You can also get this plugin as part of the Metric Halo Production Bundle priced at $699.

Conclusion

There you have it. You don’t need to have dedicated noise reduction tools to undertake broadband noise reduction, you can use a multiband dynamics plugin in downward expander mode and get some great results without having to spend too much money.