As producers, we consider equalizers to be the most important dynamic control tool in music production. There are many different types of EQ like the Parametric EQ, Shelving EQ, Graphic EQ, and several more. However, one particular type of EQ that seems to be a “fan-favorite” is the Passive EQ. So what is Passive EQ?
What Is Passive EQ?
Passive EQ is used to create tonal changes without the need for components like tubes, transistors, or opamps. Instead, it uses passive electronic components like inductors, resistors, and capacitors. Passive EQ has no gain loss; thus, there’s no need for an amplifier to compensate for that.
Passive EQs are fairly simple since they are normally made of around 5 components only, which is a big advantage compared to active EQs, which are made up of a ton of transistors, resistors, capacitors, tubes, and sophisticated opamps.
One of the most popular Passive EQs is the Pultec EQP-1A which was released in 1951. It immediately became a must-have tool for studios due to its unique and pleasing sound characteristics.
Over the years, many developers have attempted to recreate the sound of the original EQP-1A hardware into plugins, and we discuss some of them in this article.
The 6 Best Passive EQ VST Plugins of 2021
1. Acustica Audio Azure2
Acoustica has always been one of the people’s favorites for delivering some of the finest hardware emulations, and this plugin is up to par with their standards.
Azure2 emulates a passive, tube-based mastering equalizer Knif Soma done with mastering engineer Zino Mikorey. It faithfully captures all of the nuances of the tubes and transformers in the signal chain of the original hardware using convolution technology.
One of the things that Azure2 does differently from the hardware is summing. Instead of the original parallel design, Azure2’s filters or bands work in series. It makes the EQ far more predictable and familiar.
- Stereo Processing
There are two sets of identical controls on the interface. Each controls the left and right channels by default. You can control both of them together by activating the “CL” or Control Link button. Further, you can also activate Mid/Side mode and control the mid and side signals individually.
- Multiple Variants
Azure2 comes in a Standard variant and a ZL variant. The latter is an acronym for “Zero Latency,” and it does exactly what it says, albeit with a higher CPU usage. You can use it for live performance or even during tracking.
- 4 Bands
There are four bands and two filters per channel. What makes the bands noteworthy is their filter shapes. Each of them at a different gain and Q-factor values makes peculiar shapes, giving your audio the original unit’s character.
Aure2 is available for Windows 7 or higher and macOS 10.8 or higher, both 32-bit and 64-bit. It comes in VST 2/3, AU, and AAX formats.
Azure2 sounds phenomenal and remains easy to use. The added quirks like mid/side mode and series summing of the bands make it ready for modern world mastering sessions. However, the plugin tends to be highly CPU and RAM-intensive, so before making the rather expensive purchase, give it a try.
2. Klevgrand Goto EQ
Goto EQ inspires itself on vintage tube-based equalizers by performing some classic techniques and getting results that acclaimed analog models did back in the day.
With many exciting acts on the sonic shape of any signal, Goto EQ can simultaneously cut and boost the low-end, creating a unique bassy texture and engage in dynamic functions with its Dynamic attenuation knobs that can de-ess or de-harsh the voice.
With the many shelves and bands featured in Klevgrand’s equalizer, you can add more air and clarity to their mixes by setting accurate attenuation values and applying light compression.
- Pultec Effect
By allowing you to boost and cut at the same frequency, GotoEQ provides a quick way to achieve the “Pultec effect.” technique. The producer can use the plugin’s designed high and low shelves to perform the Pultec effect, ideally effectively creating an EQ curve that will work wonders on bass.
GotoEQ features a straightforward interface with easy-to-use controls. Every parameter offers different settings with the knobs present at the plugin’s main panel. Apart from standard input/output, filter, and shelf knobs, the plugin also has handy VU metering. A dynamic process can also happen if the red knobs are operated, giving freedom to compress information in the frequency range.
This plugin is available for Windows 7 or higher and macOS 10.10 or higher, both 64-bit only. It comes in VST 2/3, AU, and AAX formats.
GotoEQ behaves as an efficient and quick-to-operate equalizer. Its highly detailed main panel features many knobs that you can operate to control the frequency spectrum’s dynamics, loudness, boosts, and attenuations. Its helpful shelving knob serves as a crucial tool for allowing producers to get an intense Pultec Effect.
3. SPL Passeq
The traditional hardware for this plugin came at a price of about $5499 and weighed around 12 kg which meant that only a few people could actually manage to have one.
Thankfully, SPL has managed to release a plugin version that offers similar qualities for a small fraction of that price.
The interface of this plugin may come across as very confusing at first, but the workflow is clear, and you’ll get used to it in no time. Frequency bands are situated whereby the cut knob is on the left, and the boost knob is on the right for every band. You have control over 3 cut ranges, i.e., 1. LF-LMF, 2. MF-MHF, 3. MHF-HF and 3 boost ranges, i.e., 1. LF, 2. LMF-MHF, 3. and HF.
Much like the hardware version, the plugin uses an attenuator to gain control. The reasoning behind it is to maintain a low noise floor, linearity, and have enough headroom space. The main difference between the plugin and the hardware version is in the additional recall buttons, M/S operation, and stereo channel linking. In addition to that, the plugin version has a space-saving Passeq Single, which shows only one set of controls for you working in stereo only.
- The plugin has 2 modes of operation, i.e., the standard stereo and a mono version
- Mid/side (M/S) processing is available
- Manages to successfully reproduce the workflow of the original hardware passive eq, which translates into similar sound signatures
- Made up of 72 filters spread over 6 bands per channel
The SPL Passeq is compatible with Windows 7 or higher for PC and macOS 10.9 or higher for Mac. It comes in VST/VST3/AU/AAX formats and supports 64-bit systems.
The Passeq by SPL is one of the most powerful passive EQs in the market. This is due to the detailed design of the plugin to perfectly replicate the sound signature of the original Passeq hardware, which was already considered the industry-standard passive equalizer. It comes at a reasonable price for its capabilities, and we definitely recommend that you try it out.
4. NI Passive EQ
Native Instruments has collaborated with Softube to develop a plugin that models three pieces of some highly rated and revered valve outboard gear.
As mentioned, the Native Instruments Premium Tube series plugin comprises 3 plugins: a Passive EQ, an Enhanced EQ, and a Vari Comp. Although the developers do not mention exactly which hardware units are modeled in these plugins, we notice a great similarity in terms of the layout and control parameters with some of the popular units by Manley.
It consists of 4 bands, all with sweepable bandwidth and also notched frequencies. Each band is switchable between a bell or a shelf. Finally, Passive EQ includes high and low pass filters.
The Enhanced EQ is a simple 3-band passive EQ with a low shelf, high bell, and high cut parameters with all frequencies notched. Assessing its design, we can say that it is probably modeled after the Manley Enhanced Pultec EQP-1A.
The Vari Comp features 5 recovery/release settings, sidechain gain, and individual dry level/parallel compression. In addition to that, it has controls for input level, threshold, and output level, which enables you to easily add saturation to the process.
- This plugin is open and organic, making it perfect for both mixing and mastering
- 2-channel, 4-band EQ that is fully parametric
- A/B mode, M/S processing, and per-band stereo link
This plugin requires Windows 7 or higher for PC and macOS 10.12 or higher for Mac. It comes in VST/AU/AAX formats and only supports 64-bit systems.
Overall, Native Instruments Passive EQ is a very straightforward passive equalizer plugin that offers high-quality filters. We can say that it is reasonably priced because it comes with 2 other important plugins in one pack.
5. Manley Massive Passive EQ
Manley Labs is a well-known name in the field of equalizer plugins, and the Massive Passive EQ is another incredible addition to their arsenal as it utilizes a Pultec-style passive EQ as its primary technology.
Massive Passive EQ consists mainly of 4-bands. All the bands are set up in parallel, with each having both lowpass and high pass filters, as well as an all-valve gain make-up stage and transformer emulated balanced output. Bands can be set to have a bell shape or a shelf shape and can be set to either cut or boost frequencies. Frequencies are notched, and there’s a good amount of frequency overlap across bands. The gain is dependant on the bandwidth, so when the bandwidth is at its narrowest, the maximum gain is at 20dB, whereas when the bandwidth is at its widest, the maximum gain is 6dB.
In addition to the Massive Passive EQ, the developers at Manley Labs decided to release the Massive Passive Mastering Version as a separate “extra” plugin based on the original hardware that added both notched bandwidth and gain controls due to users demanding more stereo friendly units. There is a reduction in a maximum gain in the plugin version, which is now set at 11dB for much better accuracy. Finally, master gain trims were added to reduce the overall gain.
- Includes Parallel EQ design which means that if you EQ the same frequency over 2 bands, the gain doesn’t double
- Makes use of a fully passive circuitry (discussed in the introduction to this article)
- Bandwidth control allows you to achieve distinctive shelf curves
- You can choose between interleaved and overlapping frequency
- In this plugin, you can set each band to have either a bell or shelf shape
- Vacuum tubes are used in line and gain drivers, which adds a smooth harmonic distortion, thus giving you a more pleasant-sounding finish
Massive Passive EQ is compatible with Windows 7 or higher for PC and macOS 10.9 or higher for Mac. It comes in VST/AU/AAX/RTAX formats and only supports 64-bit systems.
The Massive Passive EQ is one of the most popular equalizer plugins that you can find. It perfectly models the original Massive Passive hardware that many developers have attempted to emulate over the years. However, this plugin by Manley Labs and Universal Audio is the most comprehensive and the closest in terms of sound quality and features to the original hardware unit. It is a relatively more expensive plugin, but many producers and engineers believe that it’s worth it.
6. Waves RS56 Passive EQ Review
Waves have always been flawless when emulating classic hardware units, and this plugin is not different.
The RS56 Passive EQ by Waves is modeled after a hardware unit named EMI RS56 UTC and was introduced in 1951. This was the company’s first attempt at a Pultec-style passive equalizer.
The hardware unit offered you control over 3 bands: the Bass, treble, and top bands. Each band had four stepped frequency settings ranging from 32 to 8092Hz and a few more at 5600Hz and 11200Hz. In addition to that, you can set the gain to a maximum of +/-10dB in 2dB steps. Furthermore, you could choose between 4 peak shapes for each band which are: 1. Blunt, 2. Med Blunt, 3. Med Sharp, 4. Sharp) as well as High End and Low-End shelves.
With the Rs56, the developers at Waves have chosen to stick closely to the original hardware unit design and add a few extra features for more versatility and better flexibility. These features are discussed below.
- The maximum gain is set at +/- 20dB with a 0.1 dB increment
- EQ graph for users to view the affected frequency range
- VU meter is now included in the plugin version of the RS56
- Waves RS56 comes in mono and stereo versions. The stereo version has 3 modes: M/S, Stereo, and Duo
- The RS56 plugin by Waves has a very smooth workflow and a simple design
Waves RS56 passive EQ is compatible with Windows 10 for PC and macOS 10.13.6 or higher for Mac. It comes in VST/VST3/AU/AAX formats and supports 64-bit systems only.
At this point, any plugin developed by Waves is guaranteed to be of superb quality, high versatility, and simple design. When it comes to emulating classic hardware, Waves are the best, and the RS56 is no exception. On top of that, it comes at a relatively lower price which makes it very attractive for many users.
Best Free Passive EQ Plugin
Ignite Labs PTEq-X (FREE) Review
It is really surprising to find a FREE plugin in this market field that offers solid quality, but Ignite Labs has managed to miraculously pull that off with their PTEq-X plugin.
What’s more surprising, however, is the fact that the PTEq-X plugin emulates 3 classic, popular vintage passive equalizer hardware, and it does an excellent job of that too. Every component on the original hardware circuit has been carefully studied and modeled in the best possible way into the plugin version. In addition to that, the developers of this plugin have managed to optimize this plugin for better CPU performance and real-time playability.
- It consists of 3 different modules for equalization with a smooth curve response that produces analog sound even at very high frequencies
- It offers you more frequencies to choose from in the PEQ1A model in comparison to the original hardware
- The filters in the MQ5 and H3C models are more refined for better frequency precision when compared to the original hardware
- The PTEq-X is optimized for maximum CPU efficiency through tube stage modeling and switchable equalizers
- Aliasing reduction is made using linear-phase oversampling
- All control parameters in this plugin are fully automatable
- The PTEq-X plugin makes use of the preset management system designed Ignite Amps to provide you with functions like import or export presets
This plugin requires Windows 7 or higher for PC and macOS 10.7 or higher for Mac. It comes in VST/VST3/AU formats and is compatible with 64-bits only.
To find a good plugin that perfectly emulates original passive EQ hardware at a reasonable price is pretty difficult, and for Ignite Labs to do that and for FREE is just mindblowing. The PTEq-X plugin by Ignite Labs is so incredible that it almost feels too good to be true, and we highly recommend it, especially if you have not decided on which passive EQ plugin to buy yet.
1. IK Multimedia EQP-1A Review
We have previously discussed several plugins by IK Multimedia and especially their T-Racks series, which aims to provide you with industry-standard plugins at a reasonable price.
IK Multimedia’s EQP-1A is a superb attempt at emulating the classic EQP-1A hardware. It models 2 classic hardware units, although the developers do not specify them.
The EQP-1A first came into the scene in 1951 and was the first EQ to implement passive circuits technology. Since the passive circuitry was fairly new at that time, the original EQP-1A had some issues that caused the inherent gain loss. A makeup gain control knob at the output was used to compensate for this loss in volume. The output gain control was based on the 12AU7, 12AX7, and 6X4 tubes, which added a more vibrant character to the signal.
The plugin version of the EQP-1A manages to perfectly replicate the sound characteristics and design of the original hardware while being highly functional in the digital world.
- EQP-1A has one of the most simplistic user interfaces among Passive EQs
- Offers high-quality oversampling to ensure maximum quality
- EQP-1A by IK Multimedia is one of the few plugins that manage to accurately model vintage hardware
- Has latency compensation which makes it usable in real-time
- Up to 192 kHz of sampling rate is supported
- This plugin makes use of proprietary IK technologies like the SCC and the DSM to model analog hardware incredibly accurate
IK Multimedia’s EQP-1A is compatible with Windows 7 or higher for PC and macOS 10.9 or higher for Mac. It comes in VST/VST3/AU/AAX versions and only supports 64-bit systems.
It is not really a hard choice to highly recommend a plugin by IK Multimedia due to its consistency, attention to detail, and reasonable price. The EQP-1A is among the best passive EQs that you can find and is among very few that offer analog characteristics while maintaining quality and low price.
2. PULTEC Passive EQ Collection Review
UAD are considered giants in the compressors market with their LA-2A and 1176 plugins, and now this is their attempt at emulating the classic Pultec EQP-1A EQ.
As discussed before, the original EQP-1A was an instant hit at the time of its release back in 1951. Users described its sound characteristics as ‘smooth,’ ‘warm,’ ‘airy,’ and ‘musical.’ Another thing that helped popularize the EQP-1A was its unusual design elements, making it suitable for a wide range of applications.
In this collection by UAD, the first plugin is a direct replication of the EQP-1A and features three-stage tone control. It features separate Boost and Attenuate control parameters to allow you to boost and cut frequencies at the same time, which was a huge deal when Pultec first released the EQP-1A. Additionally, the plugin developers have spent time designing the tube amplification for output gain, which resulted in a similar, ‘warm’ sound signature.
The second plugin is called Pultec Mid – Range Equalizer, and it models the MEQ-5 by Pultec. The MEQ-5 is a single-channel, midrange equalizer that offers control over 3 bands: 2 midrange boost bands and 1 midrange dip band. This made the MEQ-5 perfect for use on instruments like guitars and so on.
The last plugin is the Pultec Filter which emulates the HLF-3C. This is for use on higher frequencies. It has 12dB high and low cut filters to allow you to tame annoying frequencies.
- This plugin has features from well-known engineers like John Paterno, Neal Capellino, and Jacknife Lee
- Accurate reproduction of the sound characteristics for all the 3 plugins involved
- The most comprehensive all-around Pultec-style passive EQ collection
This plugin is compatible with Windows 7 or higher for PC and macOS 10.9 or higher for Mac. It comes in VST/AU/AAX/RTAS formats and supports 64-bit systems only.
If you are an experienced producer or engineer and would like a passive equalizer that would offer you more control over your track’s dynamic range and sound characteristics, then look no further. The Passive EQ collection offers you exactly what you need in terms of passive EQs, and it does that in 3 plugins to allow for more control.
Passive EQs have over the years become the go-to equalizers for engineers and producers looking for an alternative to the “lossy” active EQs. Passive EQs require no gain compensation because of the minimum to none gain lost when cutting frequencies. It provided tracks with a smooth, silky, and warm feel instead of the choppy and somewhat “lifeless” feel that other types of EQs seem to bring.
When it comes to the plugin market, we have seen that quite a several developers have attempted to emulate the EQP-1A like the Pultec Passive EQ collection, Ignite Labs PTEq-X, IK Multimedia EQP-1A, and many others. Other developers like Waves and Native Instruments have decided to model a different hardware unit. All in all, the plugins differ in looks, price, and sound characteristics. So if you are familiar with traditional Passive EQs, then your choice won’t be very hard. However, if you are a beginner, we highly recommend that you give the Ignite Labs PTEq-X a try since it is a high-quality free plugin.
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