Bass Performance of Audyssey vs Dirac Live vs Dirac Live Bass Control vs MSO

I have previously compared the performance of Audyssey vs Dirac Live vs YPAO. However, I wanted to write about bass performance specifically in this article. Please note that I tackle the subject from a theoretical perspective in this article.

There is a lot to say about how these systems achieve or might achieve their individual goals across different setups, but those will be tacked in separate articles. In addition, we don’t know much about Dirac Live Active Room Treatment yet, only what we have been told by Dirac. So while we can discuss Dirac Live ART theoretically, actual performance will have to be seen in real-world setups including my own system.

Audyssey – XT32

Audyssey has had relatively good subwoofer equalisation ever since the introduction of Audyssey XT32. It was also when multi-sub capability was introduced with Audyssey MultEQ HT, which has been able to handle more than two subwoofers since its inception. However, AVR manufacturers only implemented two independent subwoofer outputs on Audyssey AVRs until recently.

On Denon’s and Marantz’s new receiver lineup, you are able to connect up to 4 independent subwoofers which Audyssey will time-aline and then EQ together – that is if you are using them in their normal configuration – as opposed to zone / directional bass configuration.

Audyssey XT32 has very detailed correction filters in the subwoofer channel with filters in around 3Hz increments. When it comes to MultEQ HT, it can handle 2 or more subwoofers. Each subwoofer will be independently time-aligned and volume adjusted, then the combined response is equalised together. While this is relatively good at equalising the subwoofer response across the listening space, the drawback of this approach is that it isn’t necessarily going to reduce the level of variance between seats. It will simply apply a filter that equalises the combined response and creates a middle-ground or compromise for all measured seats – not necessarily perfect in any of the seats.

This approach is really the only approach we can apply with only one subwoofer. However, with multiple subwoofers, there is a more sophisticated method, which we will talk about next!

Ratings:

• Single-subwoofer: 7 / 10
• Multiple subwoofers: 7 / 10

MSO – Multi-Sub Optimiser

As discussed in my review of MSO, it gets you to measure each of your subwoofers independently across all listening spaces, then configure it according to the trade-offs you would like and the type of DSP you have. It will then run through thousands of scenarios to find the optimal PEQ filters for each subwoofer to reduce the seat to seat variation in the response.

Additionally, you are able to say whether you care about the response being flat (such as when you won’t be applying additional DSP or room correction) or you are simply caring about seat to seat consistency, because you’ll be applying room correction.

In essence, MSO equalises and phase / time-aligns each subwoofer independently while modelling he combined response across all seats. This method is quite a few steps ahead of Audyssey in that the compromise will generally achieve a much tighter response and less seat to seat variation than Audyssey.

I like to combine the two approaches. I have set up my MiniDSP with MSO so I get as flat a response as possible across all my seats, then I overlap Audyssey with Audyssey only seeing the multi-sub setup as a single subwoofer with the combined response. This allows for taking advantage of Audyssey’s very fine filters, but also getting a much smoother response between seats.

Ratings:

• Single-subwoofer: N / A
• Multiple subwoofers: 8 / 10 (overlay Audyssey or Dirac Live)

Dirac Live – Without Bass Control

Dirac Live will calibrate a single subwoofer without its additional bass control add-on. In addition to what Audyssey does, which is a frequency-based correction, Dirac will also tackle the time-alignment (or phase) of different frequency bands. This allows for the impulse response to be corrected and cleaned up, which can result in a punchier bass and bass that sounds like it is coming out of the main speakers due to the frequencies being aligned so well.

This can also solve issues with cancellation issues – if the cancellation occurs due to time-alignment issues between the main speakers and the subwoofer. If they occur due to room modes, that is not really solvable at this DSP sophistication level. More on that in a moment.

The issue with Dirac Live is that it will not really handle more than one subwoofer without bass control. While it will calibrate them as one, it will not set individual filters. It is a little bit like Audyssey in this sense.

However, I have found that MSO + Dirac Live together work really well. In fact, better than MSO + Audyssey, because Dirac Live will actually correct group delay (phase / timing) so the bass performance sounds much more linear and tight across the lower frequency range, but especially in the crossover region.

Ratings:

• Single-subwoofer: 8 / 10
• Multiple subwoofers: 7 / 10 (without bass control)

Dirac Live – With Bass Control

Dirac Live Bass Control with Multi-Sub is trying to do what MSO + Dirac Live together are doing, except do it much faster using machine learning and AI. It aims to:

• Time align the subs
• Work out which filters would result in the most even frequency response across all measured seats
• Apply those filters and then EQ the summed response together

The main advantage of letting Dirac Live do this end to end is the system’s phase-response: all frequencies will be time-aligned to arrive at the listeners’ ears at the same time.

As mentioned in my review, possible time and phase-alignment issues are one of the drawbacks of MSO, as it is inherent of using PEQ. While the frequency-domain might be corrected, the phase / time-alignment of frequencies can be made worse, which will “smear” the impulse response.

So letting Dirac Live Bass Control (DLBC) handle this end to end will definitely result in better time-domain response for the system, not just corrected frequency-domain performance.

Ratings:

• Single-subwoofer: 8.5 / 10 (Dirac says that some DLBC functionality is now included with Dirac Live by default for single subs – so the question is how much of a benefit is DLBC for a single subwoofer / what is the gap?)
• Multiple subwoofers: 9 / 10

Dirac Live ART – Active Room Treatment

This is where things might take an exponential leap in performance. Dirac wants to use multiple speakers – or in our case subwoofers – to control the time decay of different frequencies. Since an uneven decay time can colour the sound as much – or even more – then a non-linear frequency response – this will be a game-changer.

In fact, some people listening to the Trinnov demo said they had gotten it all wrong: our listening – and likely our thinking – up to now has been compromised by focusing so much on an flat (or tilted for house curves) frequency response.

Ratings:

• Single-subwoofer: 8 / 10 (no or minimal improvement expected dependent on main speaker capabilities)
• Multiple subwoofers: 9.5 / 10 (expected improvement – with Trinnov likely performing better still due to very specific subwoofer installation requirements).

Summary

Ok, let’s sum up the capability of the different solutions then.

Product	Frequency Domain	Time Domain
Audyssey (XT)	– Correct for one subwoofer – Does NOT reduce seat to seat variation	– Overall phase response only of the subs (no group delay correction)
Audyssey MultEQ HT (XT32)	– Correct for multiple subwoofers – Does NOT reduce seat to seat variation	– Overall phase response only of the subs (no group delay correction) – Phase alignment between main speakers and subwoofers
Dirac Live	– Correct for one subwoofer (Though will sum two or more on some systems)	– Time-aligns individual frequency groups (group delay)
Dirac Live Bass Control	– Correct for one subwoofer (Though will sum two or more on some systems)	– Time-aligns individual frequency groups (group delay) – Phase-alignment between main speakers and subwoofer with particular attention to crossover area
Dirac Live Bass Control Multi Sub	– Correct for multiple subwoofers – Individually EQing all subs – Then EQing the sum – Frequency correction for all seats – Reduce seat to seat variation	– Group delay / time-alignment is also taken care of. – Excellent time-domain performance (Except for residual ringing of frequencies)
MSO (the addition of MSO to Audyssey or Dirac brings the following benefits and drawbacks)	– Frequency Correction for all Seats – Reduce seat to seat variation	– Group delay / time-alignment could get worse due to use of PEQ – This is difficult to correct on a summed response so there will be some time-smearing. See MSO review for more.
Dirac Live ART	– N/A	– Controls frequency decay times actively using multiple source – multiple control techniques. Purely time-domain based correction on top of the other Dirac Live algorithms.

Product	Frequency Correction	Subwoofer Phase & Time (One sub)	Subwoofer Phase & Time (Multi sub)	Freq. Band Time- Alignment (Imp. Resp.)	Reduction of Seat to Seat Variation	Reduction of Ringing / Decay Times
Audyssey (XT)	Limited	Yes	No	No	No	No
Audyssey MultEQ HT (XT32)	Yes	Yes	Yes	No	Limited	Limited*
Dirac Live	Yes	Yes	No	Yes	No	Limited*
Dirac Live Bass Control	Yes	Yes	No	Yes	No	Limited*
Dirac Live Bass Control Multi Sub	Yes	Yes	Yes	Yes	Yes	Limited*
MSO (the addition of MSO to Audyssey or Dirac brings the following benefits and drawbacks)	Optional	N/A	Yes	Negative Impact **	Yes	Limited*
Dirac Live ART	N/A	Yes	N/A	N/A	Yes	Yes

* Limited: there is a reduction of ringing when room modes are targeted by the algorithm. However, this is very limited and not actively controlled.

** Negative Impact: the use of PEQ smears impulse response in the time-domain. This isn’t noticeable if the system already has time-domain issues.