HTM (Home Theater Maestro) : room-acoustics modelling tool

[patoulol]

Hi everyone,


I would like to share a project we have been developing called Home Theater Maestro (HTM).




HTM is a free acoustic room modelling and design tool intended primarily for home audio, hi-fi, home cinema and immersive audio users.


The goal is not to replace acoustic measurements or professional simulation software, but to provide an accessible way to study how room geometry, loudspeaker placement and acoustic treatment interact before making physical changes to a room.


Website: https://hometheatermaestro.fr/en/
Download: available for free for Windows, macOS, Linux and Android.


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◆ What does HTM actually calculate?


The current version focuses on several relatively well-established acoustic relationships:

• Room dimensions and geometry
• Room volume
• Room modes (3D modal map)
• Speaker/listener positioning
• First reflections and basic SBIR interactions
• Estimated reverberation time (RT60)
• Acoustic treatment modelling
• Speaker-to-listener geometry
• Import of measurement data from REW
• Comparison between theoretical predictions and measured behaviour

The philosophy is deliberately simple:


Model → predict → measure → compare → adjust.


HTM is therefore not intended to tell you that "your room will sound like this". It is intended to help identify potential acoustic problems and test different design choices before implementing them physically.

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◆ Methodology note


RT60 estimation uses a hybrid Sabine/Eyring approach depending on room absorption characteristics. This is a statistical diffuse-field estimate, most valid above the Schroeder frequency; below it, the discrete modal analysis is the relevant view. HTM reports the Schroeder frequency for that reason.


Room modes are calculated using the standard rigid-wall rectangular-room modal equation, and a 3D modal map is provided. Axial, tangential and oblique modes are all computed and shown. For non-rectangular rooms (L-shapes, sloped/attic ceilings), the modal calculation uses a bounding-box approximation, which is flagged in the interface.


More advanced per-seat metrics (banded RT60, C50, C80, ITDG, STI, IACC), detailed echogram/ETC and full SBIR analysis are part of the Pro version.


I'm happy to detail the exact formulas and assumptions in this thread if people want to check the math.

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◆ Why did we develop it?


A lot of acoustic software is either designed for professionals, requires significant acoustic knowledge, or focuses on a specific part of the problem.


We wanted to create something that could make some of the underlying acoustic concepts more accessible to enthusiasts without pretending that a simplified model is equivalent to a full numerical simulation.


The project is built around a small founding team with complementary backgrounds:

• a software development / research engineer, responsible for the core software development: @DTSman
• myself, working primarily in audio and immersive/Atmos mixing, contributing to the functional design and audio-related aspects.

It has also been shaped by a group of founder beta testers (two acousticians and two software/audio enthusiasts) and a wider volunteer beta-testing team of technically minded users, who tested the software in real-world situations, identified problems, challenged assumptions and helped improve the implementation.


So although HTM is intended for the general public and is free, the underlying objective is to keep the calculations grounded in established acoustic principles rather than relying on subjective "audio" assumptions.

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◆ An important limitation


I want to be very clear about this because this is an ASR audience:


HTM is not a full-wave acoustic solver, FEM/BEM simulation package, ray-tracing engine, or replacement for professional acoustic measurement.


A room is obviously much more complicated than the simplified models implemented in HTM.


The results depend on assumptions and idealisations, and real rooms contain many variables that cannot be completely represented by a simple geometrical model.


For that reason, I would actually be very interested in having technically minded people here challenge the calculations, methodology and assumptions.


If something is wrong, I would rather have it pointed out than have people blindly trust the software.


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◆ Measurement integration


One aspect we particularly wanted to include is the ability to work from real measurements.


HTM can import measurement data exported from Room EQ Wizard (REW), allowing the user to compare measured room behaviour with the theoretical model.


This is important to us because the software should ultimately encourage people to measure their rooms rather than relying exclusively on prediction.


The model is a starting point; the measurement is the reality.

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◆ Who is it for?


HTM is mainly aimed at:

• Hi-Fi enthusiasts
• Home-cinema enthusiasts
• DIY acoustic treatment
• Studio owners
• Immersive audio users
• Anyone trying to understand why changing speaker or listening positions can affect a room

It can also be useful educationally, because you can change room dimensions, speaker positions or treatment and immediately see how the theoretical parameters change.

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◆ Why make it free?


There is no subscription for the core acoustic modelling features; they are free for everyone.


The project started primarily because we wanted to make some of the basic tools we use ourselves more accessible to enthusiasts.


There is also a paid Pro version with additional advanced/professional functions, but the core modelling workflow is available in the free version.


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◆ I'd genuinely like technical feedback


I'm posting this here specifically because I know ASR has a technically demanding audience.


I am not presenting HTM as an authoritative acoustic simulation package.


Instead, I would like to invite people who have experience in acoustics, room modelling, REW, measurement or numerical methods to try it and tell us:

• where the model is useful,
• where it is too simplistic,
• whether the assumptions are reasonable,
• and, most importantly, where the mathematics or implementation could be improved.

Constructive criticism is very welcome.


The software is available here:
Home Theater Maestro: https://hometheatermaestro.fr/en/


The application is currently free of charge for Windows, macOS, Linux and Android, and runs offline.


If there is enough interest, I can also explain the equations and assumptions used for each calculation in this thread.


Please note that we are not yet available in the US.

 

[janbth]

…
Room modes are calculated using the standard rigid-wall rectangular-room modal equation, and a 3D modal map is provided. Axial, tangential and oblique modes are all computed and shown. For non-rectangular rooms (L-shapes, sloped/attic ceilings), the modal calculation uses a bounding-box approximation, which is flagged in the interface.

…

For that reason, I would actually be very interested in having technically minded people here challenge the calculations, methodology and assumptions.

Very interesting project! I’d like to know some more details about the «bounding-box approximation». How does it work for L-shaped rooms?

 

[patoulol]

Very interesting project! I’d like to know some more details about the «bounding-box approximation». How does it work for L-shaped rooms?

Thanks janbth

For an L shaped room, HTM mostly works with the real shape. Speakers and seats stay inside the actual footprint, first reflections bounce off the real walls, and both the volume and RT60 are calculated from the true rooom (with the mising corner removed)


The only exception is the room mode map. Getting the modes perfectly accurate in a non rectangular room is honestly pretty hard, it usually needs heavy simulation
So for that view HTM just uses a simple rectangle that fits around the L as an estimate, and it clearly marks it as an approximation in the app


In short: layout, reflections and reverberation follow your real L shape. The modal map is a solid starting point rather than an exact answer. Thats exactly why measuring with REW is useful. HTM is built to import those measurements and let you compare
The model gets you close, the measurement is the truth

 

[Paffi]

Thank you!

I just tried it. Maybe it´s on me, but I´m unable to enter:

• different distance from mlp to screen and mlp to loudspeakers. It seems, that the programm assumes loudspeaker and screen have always the same distance to the mlp?
• I´m unable to insert a distance of the front mains to the back wall, as I´m only able to enter the distance between the mains and mlp, so the mains are always at the front wall.

 

[patoulol]

Thank you!

I just tried it. Maybe it´s on me, but I´m unable to enter:

• different distance from mlp to screen and mlp to loudspeakers. It seems, that the programm assumes loudspeaker and screen have always the same distance to the mlp?
• I´m unable to insert a distance of the front mains to the back wall, as I´m only able to enter the distance between the mains and mlp, so the mains are always at the front wall.

Thanks for trying it Paffi !
and fair questions

It's not locked : that's just the starting point.

By default HTM drops the front LCR in the screen plane (against the front wall) because that's the most common case, but you're not stuck there.

To move them, switch the 3D room from View to Edit mode, then drag the speakers wherever you want, including forward on stands away from the front wall. A speaker you've moved by hand show in a different colour so you can tell it apart, and the distances update from the real geometry

The screen is its own object, separate from the speakers. It has it own distance from the front wall, so the screen and the mains don't have to sit at the same distance from the listening spot. You place the screen where you want it and the mains where you want them

So both things are possible, they re just done by moving them around in the 3D room rather than typing one single distance to MLP figure

 

[Paffi]

Thank you, will try it! i would prefer that option directly at the step where you enter the mlp distance to the screen. Otherwise the warning because of possible nulls is always wrong, if you can't adjust that.

 

[DTSman]

Hi Paffi. I work with Pat on this project.

Thanks for your feedback. It that makes sense. You're right that the null warning only helps if you can actually change the distance at that step.

I'll add a front-wall distance for the main speakers right where you set the listening distance, so you can pull them off the wall there and have the warning update with it.

It'll be in the next update I am actually working on it (1.1.0).

 

[Paffi]

Sounds good!

 

[patoulol]

Home Theater Maestro 1.1.0 is now available​

Home Theater Maestro 1.1.0 is out.

A dedicated-room design tool covering:

• Speaker placement for up to 32 channels
• Predictive acoustics
• Measurement import
• Video calibration

Offline. No account required. Free in Standard mode.

What’s new in 1.1.0​

Layered acoustic treatment​

Treatments can now be built layer by layer instead of assigning a single material to each surface.

For example:

Wool → air gap → facing

Absorption is calculated for each layer.

Also supported:

• Corners
• Sized panels
• Suspended ceilings

First reflections​

Treatments now affect early reflections, with the reduction displayed band by band.

A new diffuser designer is also included, with a complete manufacturing plan.

Critical distance per speaker​

See the critical distance for each speaker, with a visual indicator when the listening position moves outside the direct sound field.

Energy-Time Curves​

Octave-band Energy-Time Curves calculated from the actual speaker placement and the real directivity of the speakers.

More accurate SBIR​

Enter cabinet dimensions in centimetres and the acoustic centre height.

A live preview shows the expected dip as you adjust the speaker's distance from the front wall.

Better-labelled imported measurements​

Measurements can now be identified as:

Before treatment
After treatment

You can also specify named sources, with early decay clearly distinguished from RT60.

Available on​

Windows · macOS · Linux · Android

Home Theater Maestro
https://www.hometheatermaestro.fr/en/index.html

Also available on the Microsoft Store, signed and with automatic updates.

Online Demo​

No installation required:

https://www.hometheatermaestro.fr/demo/?lang=en#/salle

Feedback is welcome, even the unpleasant kind.

Almost all of the fixes and improvements in the latest versions came from discussions like these.

If something doesn't make sense, doesn't work as expected, or could simply be better, let us know.

 

[patoulol]

Find Steven’s testimonial, where he used HTM to study and technically validate the upgrade of his 7.1 private cinema to Dolby Atmos before starting the work:

Steven HTM user · upgrading an existing room to Dolby Atmos

 

[Imakeller]

The Microsoft Store indicates that Home Theater Maestro is not available in the USA. So, I thought I would go to the website and purchase the Pro version. Unfortunately, it appears the Pro version is not available to the USA either. This is very disappointing. The software looks terrific!

 

[DTSman]

Hello,
HTM just isn't open in the US yet. it's a deliberate, cautious choice on our side while we get a few things in order for that market. Nothing technical, and we
hope to open it up later. It's fully available everywhere else

 

[Imakeller]

Hello,
HTM just isn't open in the US yet. it's a deliberate, cautious choice on our side while we get a few things in order for that market. Nothing technical, and we
hope to open it up later. It's fully available everywhere else

Thank you. I will be looking forward to US availability!

 

[DTSman]

Thank you. I will be looking forward to US availability!

HTM will be available on the Microsoft Store in the US in some hours (about 24 to 48h).

The Pro licence isn't on sale in the US just yet, but that's not set in stone. For now you've got the full free version to dig into.

Good test, and as always, feedback is very welcome

 

[DTSman]

Hello,

Quick note to let you know that HTM 1.2.0 is now out

A fair amount of new stuff (more detailed release notes inside the app):
- the acoustic wall and the whole front stage can now be declared,
- you can now edit everything straight from the 3D view (click a speaker, a seat, the screen, the projector…),
- the projector, the framed screen, bipole and dipole speakers,
- and new acoustic predictions (reflections, per-seat response, interactive SBIR) …

Available at https://hometheatermaestro.fr

New video also available

Thanks in advance for your feedback, always welcome

 

[JohnPM]

@DTSman Importing measurements with long notes causes the import window to exceed the width of the other panels and the cancel/import buttons to disappear off the right hand side of the window.

 

[patoulol]

@DTSman Importing measurements with long notes causes the import window to exceed the width of the other panels and the cancel/import buttons to disappear off the right hand side of the window.

Hello @JohnPM

Thanks a lot for the detailed report, really appreciated.

We reproduced it right away: when an imported measurement carries a long
note, the import dialog stretches sideways and pushes the Cancel/Import buttons off the right edge.

The fix is done and tested, on desktop and on
the narrow mobile layout, and it will ship in the next release, 1.3.0, within a few days.

Small bonus while we were at it: the note is now truncated cleanly on one line, but the full text stays readable on hover, so nothing you put in REW's notes field gets lost.

Thanks again for taking the time. This kind of precise feedback is exactly what helps.

 

[DTSman]

Hello,

Thanks for this feedback

Here a fix illustration. It will be embedded in the next release (v1.3.0)

 

[DTSman]

HTM next release 1.3.0 will also improve navigation with distinct panel. Here some screenshots result.