WaveForming - perfect bass



Why is this important?

WaveForming is a brand-new technology by Trinnov, designed to improve the bass performance in domestic size listening rooms and home cinemas.

It uses multiple subwoofers at the front and back of the room, to create extremely even low bass levels at all the seats, and is proving vastly more effective than existing methods.

WaveForming is the product of six years' advanced research & development.

Who is Trinnov?

Trinnov Audio are a company in Paris, France, who make products for home hi-fi, home cinema, recording studios and commercial cinemas.

They focus on R&D, psychoacoustics, and digital processing, with an aim to improve the sense of reality from recordings and improve results for all listeners in a room. Trinnov's research has had a strong influence on our industry, and a major contributor to the new CEDIA Recommended Practice for Immersive Audio (RP22).

For home cinema, Trinnov makes the Altitude surround processors and Amplitude amplifiers.

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Trinnov Altitude 32 Processor

And why should I care?

The processors use their own bespoke decoding algorithms, running on a high-spec PC platform, which allows constant development and improvements to the products. For example, only Trinnov processors can 'remap' speaker locations - giving great performance across a variety of audio formats with different placement requirements, and have time alignment substantially more accurate than many.

The products also have extremely long design life - Altitude 32 processors from the launch in 2014 are kept fully up-to-date with all the latest improvements.

Writing in November 2023, an Amplitude 16 unit costs £16,345 at the latest spec (HDMI 2.1), with the Altitude 32 variations up from there.

So while the equipment is expensive, it also stays current for much longer.

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What is WaveForming?

Let's start at the beginning.

Bass playback in small rooms - that's all domestic rooms, even very large ones around 12m long - is a 'hard' engineering problem.

What happens is, bass notes bounce back and forth against opposing walls (a standing wave), and that creates areas with too much bass, and cancelled zero bass, at some of the frequencies. That's called room modes.

Room EQ Wizard software showing large cancellation at 45Hz

This room has a large cancellation at 45Hz

Room mode prediction using Room EQ Wizard software

This is much more even, which means better bass

A good cinema designer has to even the bass out as much as possible - and the main weapons are:

Multiple subwoofers - two is good, but four or more could be better.

Where we put subwoofers - often using room modelling software to predict the response

Where we put seats - to keep people out of dead or too-lively positions.

With a lot of care we can achieve good, even bass at the seats.

Many people talk about Digital Room EQ - and that definitely helps - but it only tames peaks, it can't fill the cancellations back in - and you shouldn't try, because at the very low frequencies you could destroy your equipment.

Double Bass Array (DBA) - catch the wave

This is a recent attempt to cure the problems - you don't see it much in the UK, but it's popular in Germany, where the idea came from.

To do this, you put four identical subs in the screen wall, and four more in the back wall. The front subs all move together, and send a bass wave - called a 'planar wave' - along the room.

Then, the back subs are time delayed by the speed of sound x the length of the room, and are firing backwards compared to the fronts - and so they 'catch' that wave - absorbing it so there's no reflections, and you don't get the lumpy uneven bass caused by the room modes.

But there's a problem:

That bass wave will have changed quite a bit by the time it gets to the back wall. Seats, risers and people will all affect the bass as it passes through the room.

So the calibrator has to manually 'tune' the response of the DBA system, which adds extra processing into the chain and is never quite perfect.

Enter WaveForming

WaveForming takes the excellent - but practically flawed - idea of the double bass array and perfects it.

By taking 20-30 measurements in the room, the system builds a picture of what happens to the bass wave at various frequencies when it gets to the back wall, so that the right amount of bass gets absorbed - not too much, or too little, but just right.

It's built into the surround decoder, so you don't have to re-digitise, process, and convert back to analogue signal again.

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Front subs emit a planar bass wave

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Rear subs collect the wave, curing the usual reflections and standing waves

In recent outings, Trinnov have achieved 1-2dB variations across 11 seats, which is technically incredible - so close to perfect that you really can't tell a difference, and a lot better than you get from placement techniques. That exceeds the CEDIA RP22 Level 4 requirement for bass consistency, so it really is 'state of the art'.

Flexible and scalable

Depending on the size of the room, the number of seats, how far up the frequency band you go, and how even you want the performance, a WaveForming setup could have as many as 16 subs in total (8 front, 8 back), to as few as 4 (2 front 2 back) - so it's pretty scalable. For example, a reduced sub count could give consistent bass within say 3dB - still very good indeed and well within RP22 Level 3.

In addition, because each subwoofer is actively driven by a channel in the Altitude processor, in future they will be able to absorb and emit at the same time, opening the door for 'steerable' bass.

Trinnov WaveForming 3 front 2 back

Simplified WaveForming configuration with 3 front and 2 rear subs

What next?

Firstly, Trinnov have their WaveForming overview and subwoofer placement guidelines,

If you'd like to discuss WaveForming further, whether it's an existing cinema upgrade, or a brand-new project, we'd love to help.

Let's talk about it.

Trinnov Authorised Reseller

CEDIA Certified Designer

Thanks so much to David Meyerowitz from Trinnov Audio for his help - this article is based around an interview we did for the Home Cinema Design Podcast.

The podcast is mostly for industry colleagues, because it's quite technical, but the WaveForming episode is helpful for end customers too.

Thanks also to Trinnov for letting us use their wonderful explainer images.