# RRS HLF-3C — PASSIVE HIGH/LOW FILTER

> Audio plugin with low and high cut filters for tonal sculpting. (iPhone/iPad app by RRS, OOO.)

- Source: https://appshunter.io/ios/app/rrs-hlf-3c/id1641858127 (this page in markdown: same URL + `.md`)
- Developer: [RRS, OOO](https://appshunter.io/developer/1486125568)
- Category: Music, Utilities
- Price: Free
- Rating: 5.00/5 from 19 App Store ratings · 5 written reviews indexed
- Age rating: 4+
- Requires: iOS 9.0 · 22 MB
- Languages: American English
- Released: 2022-08-28
- Data updated: 2026-08-20
- Monetization: free
- User reviews in markdown: https://appshunter.io/ios/app/rrs-hlf-3c/id1641858127/reviews.md

## What is RRS HLF?

The HLF-3C completes the Passive EQ Collection. This plug-in has 12 dB per octave low and high cut filters, providing broad retro-tonal sculpting or bygone-era special effects, without the inconvenience of insertion loss found with the unamplified passive hardware.

You can easily subtract the unnecessary frequencies in any instrument and sub-group so they stay wonderfully musical in the mix.

The original HLF-3C hardware unit is a true passive design: there are no input/output amplifiers and it does not require any external power. As a result, there is an inherent loss of signal level when using the HLF-3C hardware. The RRS HLF-3C plug-in compensates for this inherent signal loss for simplified use in the modern era: it has unity gain upon insertion (there is no insertion loss until one or both of the cut filters is engaged).

The HLF-3C interface is very simple and includes only three controls:

• Enable — This toggle switch is the plug-in bypass control. When in the down position (bypassed), plug-in processing is disabled altogether. The plug-in is engaged with the switch is in the up position. This switch can be used to compare the processed settings to that of the original signal;
• Low Cut — This rotary switch specifies the cutoff frequency of the low cut filter. Ten frequencies are available: 50, 80, 100, 150, 250, 500, 750, 1000, 1500 and 2000 CPS;
• High Cut — This rotary switch specifies the cutoff frequency of the high cut filter. Ten frequencies are available: 1.5, 2, 3, 4, 5, 6, 8, 10, 12 and 15 KCS.

To use HLF-3C as a plug-in, you need an AUv3-compatible host app like GarageBand, Auria, AUM, Cubasis and more — HLF-3C will appear in the list of Audio Unit extensions for effect plug-ins in the host app.

## Key features

- 12 dB/octave low and high cut filters
- Retro-tonal sculpting
- Special effects
- Compensates for insertion loss
- Unity gain upon insertion
- Simple three-control interface

## Recent user reviews (5 of 5)

All indexed reviews: https://appshunter.io/ios/app/rrs-hlf-3c/id1641858127/reviews.md

### 5/5 — It works and you can’t beat it!

*2025-12-15*

It does what it’s intended to

### 4/5 — IMpressive

*2024-08-31*

That’s it: I”m impressed. I’ll revisit this with more insights after using it. It’s a little delphic (non-transparent) on first acquaintance

### 5/5 — Should be way more popular

*2023-01-06*

Don’t really know why this plugin company isn’t more popular than it is. The plugins sound excellent! I’m using them in GarageBand iOS. I bought several and do not regret it at all. They are true to the hardware they are emulating, and they have a very 3D/expensive quality to them in terms of sound. 5 stars!

### 5/5 — Great developer

*2022-10-15*

Engaged with the users, receptive to feedback, cool apps. Yep, 5 stars!!!

### 5/5 — Love their apps

*2022-10-14*

Sound great, easy to use, get them all!

## Frequently asked questions about RRS HLF

### What is RRS HLF-3C?

RRS HLF-3C is an audio plugin that provides 12 dB per octave low and high cut filters. It's designed for tonal sculpting and creating special effects without the signal loss found in some hardware units.

### How does RRS HLF-3C compensate for signal loss?

Unlike its passive hardware counterpart, the RRS HLF-3C plugin has unity gain upon insertion. This means there is no signal level loss until the cut filters are actively engaged, simplifying its use in modern workflows.

### What are the controls on RRS HLF-3C?

RRS HLF-3C features a simple interface with three controls: an 'Enable' toggle for bypassing the plugin, a 'Low Cut' rotary switch with ten frequency options, and a 'High Cut' rotary switch also offering ten frequency choices.

### What frequencies can be set with the Low Cut filter on RRS HLF-3C?

The Low Cut filter on RRS HLF-3C offers ten selectable cutoff frequencies: 50, 80, 100, 150, 250, 500, 750, 1000, 1500, and 2000 CPS.

### What frequencies can be set with the High Cut filter on RRS HLF-3C?

The High Cut filter on RRS HLF-3C provides ten selectable cutoff frequencies: 1.5, 2, 3, 4, 5, 6, 8, 10, 12, and 15 KCS.

### Does RRS HLF-3C require any external power?

No, RRS HLF-3C is a digital plugin and does not require external power. It operates within an AUv3-compatible host app.

### What host apps are compatible with RRS HLF-3C?

RRS HLF-3C is compatible with any AUv3-compatible host app. Popular examples include GarageBand, Auria, AUM, and Cubasis, where it will appear as an Audio Unit extension.

### Is RRS HLF-3C available on multiple devices?

Yes, RRS HLF-3C is supported on iPhone, iPad, and iPod, making it accessible across various Apple mobile devices.

## Version history (last 2 releases)

### 1.5.0 — 2022-11-14

- Implemented GUI Scale on Pinch feature;
- Implemented Presets Drop-down Menu;
- Fixed parameters tweaking crash bug in some DAWs.

### 1.0.0 — 2022-08-28

No release notes.

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## More apps by RRS, OOO

- [EQ560](https://appshunter.io/ios/app/eq560/id1486125569)
- [EQ-A](https://appshunter.io/ios/app/eq-a/id1492043981)
- [EQ550](https://appshunter.io/ios/app/eq550/id1507132030)
- [EQ550b](https://appshunter.io/ios/app/eq550b/id1507176549)
- [PolyIvoks Filter](https://appshunter.io/ios/app/polyivoks-filter/id1507649629)
- [RRS EQ3](https://appshunter.io/ios/app/rrs-eq3/id1507895144)

All apps by RRS, OOO: https://appshunter.io/developer/1486125568

## Related topics

[my harmonics](https://appshunter.io/ios/topics/my-harmonics)

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*Data collected daily from the US App Store and indexed by [AppsHunter](https://appshunter.io/). User reviews are verbatim App Store reviews. Ratings, prices and chart positions refresh continuously; this snapshot is from 2026-08-20.*