Freeware - Ghost Note Audio Spectrum Thief VST Plugin

https://ghostnoteaudio.uk/products/spectrum-thief

Spectrum Thief is an EQ-matching plugin that can import and export impulse responses. Great for capturing the frequency response of speaker cabinets, or creating adjustment filters to tone-match your guitar tone (or even a full mix), to a reference sound. The plugin is FREE and requires no authentication or registration, so grab your copy!

Freeware - REEV-R VST Plugin

https://github.com/tiagolr/reevr

REEV-R is a cross-platform convolution reverb with modulation for pre/send and post/volume signals.

Freeware - Flo Audio Impulse Response Sets

https://floaudio.bandcamp.com/music

Assorted reverb IR sets

Make Your Own Reverb - Synthetic Impulse Response Tutorial in REAPER DAW

Freeware - IR Impulse Response Listing

https://www.kvraudio.com/forum/viewtopic.php?p=8553062#p8553062

Here’s a very long list of free reverb impulse response as well as other IR such as a guitar amp, speaker, amongst others.

UIUC Wearable Microphone Impulse Responses

https://databank.illinois.edu/datasets/IDB-1932389

A dataset of acoustic impulse responses for microphones worn on the body. Microphones were placed at 80 positions on the body of a human subject and a plastic mannequin. The impulse responses can be used to study the acoustic effects of the body and can be convolved with sound sources to simulate wearable audio devices and microphone arrays. The dataset also includes measurements with different articles of clothing covering some of the microphones and with microphones placed on different hats and accessories. The measurements were performed from 24 angles of arrival in an acoustically treated laboratory.

Freeware - Overloud Hybrid Free Reverb VST Plugin

https://overloud.com/products/hybrid-free#getfreelib

Hybrid is a Reverb Impulse library that synthesizes the fascinating life of the real spaces with the soundness of the digital reverb units. Up to ten multiple reverb sources have been spread in the stereo field and mixed together using Tube summing mixers in order to achieve unique textures. The library contains 10 IRs and 15 presets. The IRs are designed for the REmatrix multilayer convolver, whose Player version can be downloaded for free.

Freeware - Chowdhury DSP BYOD VST Plugin

https://chowdsp.com/products.html#byod

Build-Your-Own-Distortion (BYOD) is an audio plugin that allows the user to create custom guitar effects, with a focus on guitar distortion. The plugin contains emulations of guitar distortion and tone-shaping circuits from various, along with a handful of other useful effects. BYOD supports the following desktop plugin formats: VST3, AU, CLAP, AAX, Standalone, and LV2, as well as Standalone and AUv3 on iOS devices.

Freeware - Overloud Blackstar Studio IR Collection

https://overloud.com/products/blackstar-studio

The Blackstar Recording Studio is a studio equipped with lots of Vintage gear and located in Milan. The main recording room as well as all the studio rooms have been carefully sampled by Valerio Mina with several microphone setups, in order to capture all the nuances and sound perspectives, for a total of 40 IRs. The IRs are designed for the REmatrix multilayer convolver, whose Player version can be downloaded for free.

Freeware - Flos Audio IR Cabinet Plugins

https://www.kvraudio.com/developer/flos-audio-plugins

3 separate Guitar Cab IR sets in plugin form.

Freeware - Studio Nord Bremen SNB Impulse Responses

http://www.grgr.de/IR/

Various guitar cabinet impulse response files.

Freeware - Metallica Gold IR Pack

http://www.richardcookson.co.uk/Tattva/

Freeware - ZETA Guitar Cabinet IR

https://laptopguitarist.com/2019/03/28/free-zeta-guitar-cabinet-impulses/

Cabinets included: 

 Orange PPC 212 Closed Back 

Bogner 212 CB Closed Back Stack 

Diezel 412 FC (V30) 

Mesa 412 Recto Slant 

Bogner Uberkab 412 STU 

Cabs were profiled using a Peavey 5150 power amp, Shure SM57 on a Dynamount, CAPI VP28 preamp (a clone of a vintage API) and an Auralex pad under the cabs.

Freeware - Soundwoofer Top 20 Impulse Responses

https://www.soundwoofer.se/blog/about/top-20-list/

Freeware - Lancaster Audio PULSE IR Loader VST Plugin

https://lancasteraudio.com/shop/plugins/pulse/

PULSE was built to be the most powerful yet easy to use impulse response loader on the market. It was designed for both the aspiring engineer and seasoned pro to be able to utilize Impulse Responses to their fullest potential. PULSE has been optimized with real-time sample rate conversion, the achilles-heel of all other IR loaders, and introduces zero latency to your DAW environment.

Free Impulse Response Download – Cenzo Townshend IR Mix

https://www.celestionplus.com/free-download/

Get a genuine Celestion impulse response download to try out – for free!

Cenzo Townshend is one of the world’s leading mixing engineers, with multi-platinum recordings to his name for some of the biggest names in rock and pop including Kaiser Chiefs, U2, The Maccabees and Jake Bugg. He’s been awarded ‘Mix Engineer Of The Year’ in 2009 and 2010 and was nominated yet again in 2016 and 2017. Decoy Studios – where our IRs were recorded – is Cenzo’s base in the UK, so we asked him to put together a special IR mix, just for you, by blending several impulse responses together.

We wanted a classic guitar tone that would work from clean to higher gain rock. Cenzo selected the Vintage 30 in the closed back 1×12 cab and blended the balanced IRs of the Royer and 57 to get a fantastic core tone. Switching to an open back cab he mixed in the rear 57 to enhance the bass, then subtly included the Neumann room mics to add the spaciousness of an open back cab, and provide the glue to hold it all together. So, if you’re itching to give our impulse responses a try, this is your perfect opportunity.

Freeware - Wilkinson Audio Free Collection

https://wilkinsonaudio.com/collections/free

Wilkinson Audio Free Collection. Guitar Cab IR and Kontakt Bass Guitar Instruments.

Freeware - STL Tones Ignite Emissary Plug-in Bundle

https://www.stltones.com/products/stl-ignite-emissary-plug-in-bundle

Re-coded from the ground up. The Emissary is a no-compromise custom amp built for the kill. Featuring a versatile clean channel that ranges from pristine cleans to slightly overdriven tones. A brutal lead channel designed for serious bone-crushing distortions. This module offers a very wide tonal palette for not only the modern metal musician, but a wider variety of genres.

Freeware - Impulse Records Convology XT VST Plugin

https://impulserecord.com/project/convology-xt-plugin/

Free Factory Plugin – Includes 70 vintage Impulse Response Files! This FREE plugin download, comes in VST, AU and AAX and features a sampling of files contained in the Convology XT Library! There are no time limitations, iLok or frustrating unlocking hoops to jump through. Simply fill in the information on the licensing page and that’s all there is to it.

Freeware - Melda MConvolutionEZ Reverb VST Plugin

https://www.meldaproduction.com/MConvolutionEZ

MConvolutionEZ is an easy-to-use highly optimized convolution reverb. Comes with lots of impulse responses for rooms, halls, plates, guitar cabinets, effects...