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Overloud TH-U Premium

What do Overloud’s Fluid IRs add to their flagship amp‑modelling software?

Overloud’s amp and effects modelling package has evolved considerably since its launch in 2008 (we reviewed TH‑1 back in SOS March 2009:, with developments such as amp capturing included alongside a generous raft of amps, speakers, effects and routing options.

Component Modelling

We’re on the fourth generation of Overloud’s amp modelling technology, which has been designed to capture the crucial non‑linearities of overdriven amplifiers under real‑world playing conditions. Currently there are 89 guitar amp models with a choice of 50 cabinets, and four bass amp models with two related cabinets. The amp capture system is based on component modelling, which is refined by taking multiple measurements of the real thing at different control settings to build up a more accurate picture of how a particular amp behaves. On top of that you get 84 pedal and rack effects, 18 different mic models, and the option of putting up to four mics on the selected cabinet.

An Amp Tweak facility lets the user modify the amp models by switching out valve types and/or emulating the effects of a Variac, which lowers the operating voltage. Users can also load their own speaker IRs, but the really big news — it’s the main focus of this review — is that the speaker emulation now includes what Overloud call Fluid Convolution and ReSPiRe 2 technology. The software includes 20 emulations created by capturing complete rigs, and in all cases ReSPiRe 2 enables the user to shape the sound by changing and moving virtual microphones. In case you were wondering, ReSPiRe stands for Real Sound Pressure Response. This latest version (v1.4.26) sees all cabinets and IRs updated to Fluid IRs, while previous updates in version 1.4 have added pedal models including the Centuria (Klon Centaur) pedal, Tri‑Chorus, Phase Stone, Reverse Delay and ModulaVerb. All these updates are free for owners of v1.4.

Various aspects of the model can be tweaked at the component level, including things like the mains voltage.Various aspects of the model can be tweaked at the component level, including things like the mains voltage.

MIDI compatibility makes it possible to set up a MIDI floorboard using a simple click‑and‑learn system. Learned MIDI connections are then available in any preset, and as there’s also a mobile iOS version of TH‑U available, using it for live gigs as well as in the studio is a very practical proposition.


While conventional speaker IRs can capture both the frequency and time‑domain responses of a speaker, they don’t take into account the way that the speaker performs at different power levels and in different dynamic situations. A real speaker introduces harmonic distortion, something a conventional IR can’t replicate, and this distortion changes under different drive conditions adding an important component to the sound. The harmonics generated by a guitar speaker are frequency dependent, with more harmonics are added to the lower frequencies than to the higher frequencies. Some systems use multiple IRs to try to capture changes that occur at different levels but again, as conventional IRs can’t capture non‑linearities, the important harmonic distortion information is lost.

While Overloud don’t want to give away too much about their methodology, they do tell us that they use a proprietary format that embeds the additional data and that the process is related to Volterra Kernels, which some readers will know as a technique that’s long been used by Acustica Audio in their Nebula and Acqua plug‑ins to measure and replicate non‑linear systems — it includes a lot of scary maths, but there are many published papers on the subject if you fancy some late‑night reading! Overloud have developed their own slant on that technique, specifically optimised for speaker cabinet emulation. A SuperCabinet feature allows the blending of up to four separate IRs, each IR being focused on a specific frequency range using crossover‑type filters. The result can then be exported as a new IR in the form of a WAV file. While each cabinet model, including SuperCabinet, now uses Fluid IR, the original IRs are still available too, and user IRs can be converted into Fluid IRs using SuperCabinet. When you load a standard IR, TH‑U analyses its response, then reconstructs its harmonic generation, dynamic response and its Z‑curve.

Sound & Feel

The operational paradigm of TH‑U holds few surprises and the fairly brief manual bears testament to the fact that most operations are intuitive. Items from a gear list, which is viewed by category, are placed in the centre of the screen to form your processing chain, which might typically be something like an overdrive pedal followed by an amp head followed by a cabinet, perhaps with some reverb or delay after the amp. There’s also a comprehensive library of presets, again sorted into helpful categories, that show off the range of sounds available.

By default, the Flow IR versions of the cabinets are operational but you can go into the master settings menu and switch back to the old‑school IRs if you want to hear the difference. A splitter can be dragged into the chain at any point so that you can, for example, run two amps and cabs in parallel, and when you open the details for the selected speaker cabinet, you can choose which mics to use, where to place them and how much to pan them.

For my tests, I used both a Strat and a Les Paul. Overloud’s amp emulations have always been good and this latest generation behaves very much like the real thing, with an impressive dynamic response and a sense of ‘springiness’ that translates to a comfortable playing feel. The new Fluid‑enabled cabinets really enhance that sense of touch responsiveness, and they also seem to emulate speaker compression, which feels very natural. Switching back to the older IRs for comparison revealed a significant difference in terms of dynamic response. The low end of the Fluid IRs also behaves in a more natural way when playing chords. For fans of the Klon Centaur, the Centuria overdrive is very detailed and responds much like the real thing, while the ability to tinker with the valves inside the amps can also yield worthwhile results.

I’ve tried more amp modellers than I’d care to count, and I have to say that very few of them react in such an organic way to playing dynamics as TH-U does...

I’ve tried more amp modellers than I’d care to count, and I have to say that very few of them react in such an organic way to playing dynamics. The clean sounds are warm and springy but the highs never become glassy. The gentle break‑up blues tones work perfectly, and when you get to heavier rock, the sense of high‑end aggression is balanced by a hefty punch and good note definition, again without the highs becoming irritatingly edgy.


If you already own one of the TH‑series packages, it’s definitely worth upgrading to this latest version — and if you already have an earlier 1.4 version, an update won’t cost you anything. There might not be many visual differences between this version and earlier ones, but with the new Fluid IRs, your ears will definitely discern a difference!


  • Fluid IRs deliver a more ‘real’ sound and playing response.
  • A huge choice of amps, speaker cabs and effects.


  • Presets that include pitch‑shifting sound less smooth when playing chords.


An already excellent amp emulation just got even better.


€299 (discounted to €269 when going to press). Upgrades from previous versions from €79. Prices include VAT.

$299 (discounted to $269 when going to press). Upgrades from previous versions from $79.