FabFilter Pro-Q has long been considered the gold standard of digital equalizers in the audio production world. However, Three Body Technology’s Kirchhoff EQ has emerged as a formidable challenger, promising expanded capabilities and seeking to dethrone the reigning champion. This comprehensive analysis explores both EQs in detail, examining their features, sound quality, workflow, and practical applications to help you determine which might best suit your production needs.
Table of Contents
The Evolution of Digital EQs
FabFilter Pro-Q: The Established Standard
FabFilter’s Pro-Q has evolved significantly since its initial release in 2009. The Pro-Q user interface quickly became influential across the industry after its 2011 debut, establishing a new paradigm for how digital EQs should look and function. Pro-Q 2 arrived in 2014, adding critical features like tilt shelf curves, match EQ capabilities, and an improved analysis section.
Pro-Q 3, released in late 2018, introduced dynamic equalization as its headline feature, allowing frequency-dependent dynamics processing without duplicating the functionality of FabFilter’s dedicated Pro-MB multiband processor. Instead, Pro-Q 3 implemented a streamlined approach to dynamic EQ with intelligent automatic settings. This version also improved inter-plugin communication, allowing instances to share spectral information and introduced the “Show Collisions” feature to identify potential frequency masking issues.
The latest iteration, Pro-Q 4, launched in 2024, further builds on this foundation with new features including curve sketching, improved instance management, and enhanced dynamic capabilities. Throughout its evolution, Pro-Q has maintained its reputation for pristine sound quality, intuitive user experience, and CPU efficiency.
Kirchhoff EQ: The Ambitious Challenger
Three Body Technology’s Kirchhoff EQ represents a newer entrant to the high-end digital EQ landscape. Released through Plugin Alliance, Kirchhoff EQ made immediate waves by openly positioning itself as a contender to Pro-Q’s crown. Rather than taking a completely different approach, Kirchhoff builds upon Pro-Q’s successful interface paradigm while expanding the feature set in several key directions.
Kirchhoff distinguishes itself with extensive customization options, a broader palette of filter types (15 in total), and 32 vintage EQ emulations modeled from classic hardware. It offers enhanced dynamic processing capabilities with greater user control than Pro-Q, while also providing multiple phase processing options and extensive user interface customization. Kirchhoff has quickly gained adherents who appreciate its extensive feature set and analog-inspired processing options.
User Interface and Experience
FabFilter Pro-Q Interface Design
Pro-Q’s interface has become iconic for its clarity and intuitive operation. The display centers around a large, responsive frequency analyzer with a clean, uncluttered layout. Creating and manipulating EQ bands is remarkably straightforward—users simply click anywhere on the spectrum to create a new band, then drag to adjust frequency and gain. The Q value (bandwidth) can be modified by dragging vertically or using the scroll wheel.
Each band receives a distinct color for easy identification, and the intelligent band selection mechanism makes it simple to select, adjust, or delete bands even in complex setups. The interface scales smoothly from simple to advanced use cases, making it approachable for beginners while offering depth for professionals. The window is fully resizable, adapting perfectly to various screen sizes and workflows.
Pro-Q 4 has maintained this core design philosophy while adding the new curve sketching feature, which allows users to draw EQ curves freehand using a paintbrush tool—a significant workflow enhancement for quickly roughing out EQ shapes that can then be refined with precise controls.
Kirchhoff EQ Interface Design
Kirchhoff EQ’s interface shares many fundamental similarities with Pro-Q, employing a similar paradigm of displaying the frequency spectrum with manipulable bands overlaid. However, Kirchhoff takes customization to another level with its extensive personalization options. Users can adjust virtually every aspect of the interface through dedicated menus for behavior, knobs, GUI, themes, and favorites.
The analyzer display is fluid and visually appealing, with options to change scale and customize how information is presented. Like Pro-Q, each band receives its own color coding, but Kirchhoff allows users to customize these colors as well. The interface includes handy features like a togglable piano roll that displays a keyboard at the bottom of the analyzer for reference.
While offering more customization options, some users find Kirchhoff’s interface slightly more complex and potentially slower to navigate than Pro-Q’s streamlined approach. The trade-off comes in the form of greater visual and operational flexibility for those who wish to tailor their EQ experience precisely to their preferences.
Workflow Comparison
In direct workflow comparisons, Pro-Q generally receives praise for its speed and efficiency. Actions like adding bands, making adjustments, and visualizing changes are implemented with minimal friction. Pro-Q 4’s enhanced instance communication makes it possible to manage EQ across an entire project from a single plugin window—a significant workflow advantage.
Kirchhoff offers similar core functionality but includes more menus and options, which can either enhance or slightly impede workflow depending on the user’s preferences and familiarity with the plugin. Some users report that Kirchhoff takes a bit longer to accomplish the same basic tasks as Pro-Q, though this difference diminishes with experience. However, Kirchhoff’s extensive customization options mean that users can potentially create a more tailored workflow once configured to their liking.
Core Features and Functionality
FabFilter Pro-Q Capabilities
Pro-Q offers up to 24 bands of equalization with a comprehensive set of filter types: bell, low/high shelf, low/high cut, notch, band pass, tilt shelf, and flat tilt (in newer versions). Each band can be configured with extreme precision, with adjustable filter slopes up to 96dB/octave and a “brick wall” mode for absolute frequency limiting.
One of Pro-Q’s standout features is its processing flexibility. Users can choose between zero latency mode (ideal for tracking), natural phase mode (for mixing), and linear phase mode (often preferred for mastering). These options allow the plugin to adapt to different workflow requirements without compromising sound quality.
The spectral analyzer provides real-time frequency visualization with adjustable resolution, helping users identify problematic frequencies. Pro-Q 3 and 4 can display the spectrum of other Pro-Q instances in the project, making it easier to spot and address frequency conflicts between tracks.
For stereo processing, Pro-Q offers comprehensive channel linking options. Each band can independently affect the left channel, right channel, mid channel, sides channel, or all channels. This flexibility is particularly valuable for stereo imaging and mid-side processing tasks.
Kirchhoff EQ Capabilities
Kirchhoff EQ matches and exceeds many of Pro-Q’s core specifications with 32 bands of equalization and 15 different filter types featuring continuously variable shapes. Beyond the standard digital EQ curves, Kirchhoff’s standout feature is its 32 vintage EQ types modeled from classic analog hardware units from manufacturers like Neve, Pultec, and SSL.
Kirchhoff offers similarly flexible processing options with its phase menu, allowing users to select from various processing modes including zero latency, linear phase, and mixed phase options. The mixed phase mode represents a unique offering that balances processing characteristics for specific applications.
The plugin’s analyzer functions similarly to Pro-Q’s, providing clear visualization of the frequency spectrum. Kirchhoff also includes a piano roll feature that can display a keyboard at the bottom of the analyzer for musical reference—helpful for those working with tonal material.
Kirchhoff’s stereo processing capabilities are extensive, matching Pro-Q’s ability to process left, right, mid, and sides channels independently. It also includes high-pass and low-pass filter options with a left/right slider for additional stereo manipulation.
Sound Quality and Character
FabFilter Pro-Q Sound Characteristics
Pro-Q has built its reputation on pristine, transparent sound quality. Its digital processing aims to shape the frequency content without adding coloration or artifacts, making it suitable for both subtle corrections and dramatic tonal shaping. The term “surgical” is often applied to Pro-Q’s sound, as it allows for precise adjustments without unwanted side effects.
The natural phase mode strikes an excellent balance between sound quality and CPU efficiency, while the linear phase mode prevents phase distortion at the cost of some latency—ideal for mastering applications or parallel processing. The zero latency mode prioritizes immediacy for tracking situations where timing is critical.
Pro-Q 4 includes new options for adding subtle harmonic distortion, providing users with the choice to introduce some character to the otherwise clean processing. However, even with these additions, Pro-Q remains fundamentally a “clean” EQ designed to execute the user’s intentions without imposing its own character on the source material.
Kirchhoff EQ Sound Characteristics
Kirchhoff EQ offers both transparent digital processing and more colorful analog-inspired options. Its standard digital modes rival Pro-Q in terms of transparency and precision, allowing for clean, artifact-free equalization. However, Kirchhoff distinguishes itself with its analog emulation capabilities.
The “117 bit mode” (sometimes referred to incorrectly as “114 bit mode”) introduces subtle harmonic characteristics that some users describe as providing enhanced depth and dimension. Many users report preferring Kirchhoff’s sound in the upper mid frequencies, describing it as more natural or pleasing than purely digital alternatives.
Kirchhoff’s analog-modeled curves provide approximations of the frequency responses from classic hardware units. While these don’t necessarily replicate the full harmonic complexity of analog gear, they do offer distinctive tonal shapes that can impart character to processed material. The continuously variable filter slopes allow for smooth transitions between different filter characteristics, offering additional sound shaping flexibility.
Direct Sonic Comparison
In null tests (where one EQ attempts to match another’s curve exactly for comparison), Kirchhoff and Pro-Q can be made to sound nearly identical when using their standard digital modes with matched curves and settings. This suggests that both are achieving their fundamental equalization tasks with similar levels of accuracy.
The perceptible differences emerge when engaging Kirchhoff’s analog emulation features or when using their respective dynamic processing capabilities. Some users report preferring Kirchhoff for certain applications due to what they describe as a more pleasing sound in the upper mid range, while others value Pro-Q’s absolute transparency and predictability.
The distinction between “better” and “different” becomes important here—both EQs deliver exceptional sound quality, but with different options for coloration and character that may suit different material or aesthetic preferences.
Dynamic EQ Capabilities
FabFilter Pro-Q Dynamic EQ Approach
Pro-Q 3 introduced dynamic equalization, allowing bands to respond to the input signal’s level. This feature enables frequency-dependent compression or expansion, useful for taming harsh frequencies only when they become problematic or enhancing certain frequencies only when they fall below a threshold.
Pro-Q’s implementation takes a streamlined approach with limited user control over the dynamics parameters. Attack, release, and ratio settings are automatic, adapting intelligently to the input signal. The threshold can be set to automatic or manual control, and users can specify the maximum amount of dynamic gain change along with the “direction” of the effect (whether a boost attenuates dynamically or vice versa).
This simplified approach prioritizes ease of use and musical results over comprehensive control. Pro-Q’s dynamic bands excel at straightforward applications like taming proximity effect on vocals or controlling resonances. The ability to create very narrow dynamic bands makes it particularly effective for targeting specific problem frequencies.
Pro-Q 4 enhances these capabilities with “Spectral Dynamics,” a new feature that further expands the dynamic processing options, though specific details on this feature are limited in the search results.
Kirchhoff EQ Dynamic EQ Approach
Kirchhoff’s dynamic EQ implementation offers considerably more control than Pro-Q’s. Where Pro-Q automates most dynamics parameters, Kirchhoff provides access to settings like ratio, attack, release, and threshold, making it more similar to a traditional compressor in its level of control.
This expanded control allows for more precise tailoring of dynamic responses, making Kirchhoff more suitable for complex dynamic processing tasks. Users can shape exactly how the EQ responds to level changes, creating more customized dynamic behaviors than possible with Pro-Q’s more automated approach.
The enhanced control makes Kirchhoff particularly well-suited for specialized applications like de-essing or de-harsh processing, where fine-tuning the dynamic response characteristics can produce more natural results. Some users report that Kirchhoff’s dynamic section is substantially more capable than Pro-Q’s, describing Pro-Q’s implementation as somewhat limited by comparison.
Which Approach Works Better?
The “better” dynamic EQ implementation depends largely on the user’s priorities and workflow preferences. Pro-Q’s approach emphasizes simplicity and speed, automatically handling parameters that could otherwise require time-consuming adjustment. For many common applications, this streamlined approach produces excellent results with minimal effort.
Kirchhoff’s more comprehensive control suits users who want to fine-tune every aspect of the dynamic response, particularly for specialized applications where the interaction between dynamics and frequency needs precise adjustment. The trade-off comes in the form of a slightly more complex interface and workflow.
For users requiring only occasional dynamic EQ, Pro-Q’s approach may be preferable for its simplicity. For those who regularly employ dynamic EQ as a primary tool for complex processing tasks, Kirchhoff’s expanded control set may justify the additional complexity.
Specialized Features and Unique Capabilities
FabFilter Pro-Q’s Distinctive Features
Pro-Q offers several unique features that set it apart, even as competitors have adopted many of its innovations:
1. Inter-plugin Communication: Pro-Q instances can communicate directly without requiring side-chain routing. This enables features like spectrum overlay and collision detection, which helps identify and address frequency conflicts between tracks.
2. Curve Sketching: New in Pro-Q 4, this feature allows users to draw EQ curves freehand, quickly establishing a starting point that can be refined using the precise controls.
3. Interactive Instance List: Pro-Q 4 introduces the ability to manage all instances in a project from a single plugin window, significantly enhancing workflow for complex mixes.
4. Flat Tilt Filter: This specialized filter rotates the entire frequency spectrum around a fixed point, allowing for natural-sounding tonal balance adjustments.
5. Customizable Analyzer Settings: Pro-Q offers detailed control over the spectrum analyzer’s resolution, display mode, and behavior, helping users visualize exactly what they need.
Kirchhoff EQ’s Distinctive Features
Kirchhoff counters with its own set of unique capabilities:
1. Analog-Modeled Curves: Kirchhoff’s 32 vintage EQ types provide authentic frequency response curves modeled from classic hardware units, offering distinctive tonal shapes beyond standard digital filters.
2. 117-bit Mode: This processing mode introduces subtle harmonic characteristics that many users find enhances the perceived depth and dimension of processed material.
3. Mixed-Phase Mode: Kirchhoff offers a mixed-phase processing option that balances the characteristics of different phase relationships for specialized applications.
4. Extensive UI Customization: Kirchhoff allows comprehensive customization of the interface, including themes, knob styles, colors, and menu layouts.
5. Comprehensive Dynamic Controls: Kirchhoff’s dynamic EQ section offers detailed control over all dynamics parameters, enabling complex processing configurations.
Feature Gap Analysis
The feature gap between these two powerful EQs largely depends on specific use cases and workflows:
For mastering engineers and others who prioritize precise, transparent processing with minimal phase issues, both plugins offer excellent options, though Pro-Q’s established workflow and inter-plugin communication may give it an edge.
For mix engineers working with multiple genres who value having analog-inspired options alongside digital precision, Kirchhoff’s expanded palette of filter shapes and vintage emulations provides greater versatility within a single plugin.
For sound designers and creative producers, Kirchhoff’s extensive customization and unique processing modes offer more possibilities for distinctive sound shaping, while Pro-Q’s precision and efficiency excel for surgical corrections.
Performance and Technical Considerations
CPU Efficiency
Pro-Q has established a reputation for remarkable CPU efficiency relative to its capabilities. Even in projects with numerous instances, Pro-Q typically maintains excellent performance, making it suitable for large sessions with limited processing power. This efficiency has been a key factor in its widespread adoption as a go-to EQ across multiple industries.
Kirchhoff is generally reported to be somewhat more CPU-intensive than Pro-Q, particularly when using its more advanced features like the analog emulations or complex dynamic processing. Some users report that in large projects with multiple instances, this difference becomes noticeable, with Kirchhoff potentially requiring more system resources.
This difference in efficiency might be inconsequential on powerful modern systems but could become a consideration for those working on older or less powerful computers, especially in larger projects with dozens of EQ instances.
Stability and Reliability
Both EQs enjoy solid reputations for stability, though as the more established product, Pro-Q has had more time to address edge cases and compatibility issues across different systems and DAWs.
Some users report that Kirchhoff has experienced occasional bugs or issues, particularly in its earlier versions—a common situation for newer software products. However, Three Body Technology has been responsive with updates addressing these concerns.
For mission-critical professional applications where absolute reliability is essential, Pro-Q’s longer track record provides additional confidence, though Kirchhoff has proven itself sufficiently stable for professional use in most contexts.
Compatibility and Integration
Pro-Q supports all major plugin formats and works in all contemporary DAWs. It offers extensive surround sound support for post-production work and integrates smoothly with other FabFilter products. The plugin’s presets are backward-compatible, with Pro-Q 3 and 4 able to open presets from earlier versions.
Kirchhoff similarly supports standard plugin formats and DAWs, though its integration features are naturally less developed than Pro-Q’s due to its shorter time on the market. It does not appear to offer the same level of surround sound support as Pro-Q, which could be a consideration for post-production professionals.
Pricing and Value Proposition
FabFilter Pro-Q Cost Analysis
Pro-Q has traditionally been positioned as a premium product with pricing to match. The standalone plugin typically costs around $134, though FabFilter often offers upgrade discounts for existing customers and occasional sales. FabFilter also offers bundles that can reduce the effective cost when purchasing multiple plugins.
The value proposition centers on Pro-Q’s reputation as an industry standard, exceptional sound quality, workflow efficiency, and regular updates that add substantial new features. For many professionals, the time saved through Pro-Q’s intuitive interface justifies the premium price point.
Kirchhoff EQ Cost Analysis
Kirchhoff EQ is typically priced more competitively than Pro-Q, with some users reporting being able to purchase it for around $50-100 on the second-hand market or during deep sales through Plugin Alliance. This pricing strategy positions Kirchhoff as a potentially more accessible alternative to Pro-Q with a comparable or expanded feature set.
The value case for Kirchhoff rests on its extensive feature set, analog emulations, and customization options at a generally lower price point than Pro-Q. For users who value these additional capabilities, Kirchhoff may represent better value despite any workflow or efficiency trade-offs.
Long-term Investment Perspective
From a long-term investment perspective, both EQs have their merits. Pro-Q’s status as an industry standard means skills developed with it will transfer easily across studios and projects. FabFilter’s track record of substantial free updates adds value over time, with existing users receiving significant new features without additional cost.
Kirchhoff, while newer, demonstrates ambition and commitment to challenging the established players, suggesting it will continue to evolve and improve. Its more comprehensive feature set may provide longer-lasting utility for users whose needs grow more specialized over time.
Use Cases and Recommendations
Ideal Scenarios for FabFilter Pro-Q
Pro-Q excels in scenarios requiring:
1. Maximum Workflow Efficiency: For professionals working under tight deadlines or on large projects, Pro-Q’s streamlined interface and efficient CPU usage can save valuable time.
2. Transparent, Surgical Processing: When absolute transparency is required with precise control, Pro-Q’s clean processing and detailed control make it ideal.
3. Cross-project Collaboration: As an industry standard, Pro-Q is likely to be familiar to collaborators, making project sharing and communication smoother.
4. Post-production and Surround Work: Pro-Q’s surround support and precise control make it well-suited for audio post-production.
5. Integration with Other FabFilter Products: Users of multiple FabFilter plugins benefit from consistent interface design and inter-plugin communication.
Ideal Scenarios for Kirchhoff EQ
Kirchhoff finds its sweet spot in contexts requiring:
1. Hybrid Analog/Digital Approach: When projects benefit from both clean digital precision and analog-inspired tonal shaping, Kirchhoff offers both in a single plugin.
2. Advanced Dynamic Processing: For complex dynamic EQ tasks requiring detailed control over all parameters, Kirchhoff’s comprehensive dynamics section provides greater flexibility.
3. Highly Personalized Workflow: Users who value extensive customization of their tools will appreciate Kirchhoff’s theming and interface options.
4. Specialized Mid-side Processing: Kirchhoff’s expanded stereo processing options can be advantageous for detailed stereo field manipulation.
5. Budget-conscious Professional Setup: Kirchhoff offers professional-grade capabilities often at a lower price point than Pro-Q, making it attractive for those building a high-quality toolkit on a limited budget.
Recommendations for Different User Types
For Beginners: While both EQs are sophisticated tools, Pro-Q may offer a slightly gentler learning curve with its streamlined interface and extensive educational resources. However, Kirchhoff’s lower price during sales may make it more accessible for those just starting out.
For Mix Engineers: Both EQs excel for mixing, with the choice largely dependent on personal workflow preferences and whether analog emulation options are valued. Pro-Q’s efficiency shines in large sessions, while Kirchhoff offers more tonal variety.
For Mastering Engineers: Both are capable mastering tools. Pro-Q’s precision, linear phase options, and track record make it a safe choice, while Kirchhoff’s expanded dynamic controls and analog characteristics offer creative alternatives.
For Sound Designers: Kirchhoff’s broader palette of filter shapes and analog emulations may provide more creative possibilities, though Pro-Q’s precise control and efficiency remain valuable for detailed sound sculpting.
Conclusion: Making the Choice
The Case for FabFilter Pro-Q
Pro-Q has earned its reputation through a combination of exceptional sound quality, intuitive interface design, workflow efficiency, and thoughtful feature development. Its status as an industry standard brings practical benefits for professionals who collaborate with others or work across different studios. Pro-Q 4 continues this tradition with meaningful enhancements that address real workflow needs.
For many users, Pro-Q represents the safe choice—a proven tool that consistently delivers excellent results with minimal friction. Its clean sound, CPU efficiency, and streamlined workflow make it particularly well-suited for professionals who need to work quickly without compromising quality.
The Case for Kirchhoff EQ
Kirchhoff makes a compelling case as an alternative with its expanded feature set, analog emulation capabilities, and typically lower price point. For users who value having access to both clinical digital precision and analog-inspired character within a single plugin, Kirchhoff offers greater versatility.
Its comprehensive dynamic EQ implementation provides advantages for specialized applications requiring detailed control over dynamic processing parameters. The extensive customization options allow users to tailor the experience precisely to their preferences and workflow needs.
The Complementary Perspective
Rather than viewing these as mutually exclusive options, many professionals find value in having both tools available. Pro-Q might serve as the go-to for everyday equalization tasks where efficiency and transparency are paramount, while Kirchhoff could be reserved for situations benefiting from its unique capabilities or analog characteristics.
The decision ultimately depends on individual priorities—workflow efficiency, sound character, feature depth, customization options, or budget constraints will weigh differently for each user. Both represent exceptional tools that raise the bar for what digital equalization can achieve, offering professional-grade capabilities that can elevate the quality of audio production across countless applications.