Room correction systems: friend or foe?

Written by Published | Rapallo AV Team, Uncategorised

Shopping for an AV receiver is a little bit more complicated than setting a budget and sticking with it. In these day and age reading up on specs, streaming features and performance may only be the start of your journey.

An AV receiver may look excellent on paper, but it is what it does in your personal set-up that really counts. You may have the best of the best, but do a half job at setting-up and you have wasted a truckload of money on air. Enter the room correction system that come with your AV receiver to help you out.

Or does it?

We go as far as saying that in this day and age with Dolby Atmos and DTS:X, you almost can’t do without a good calibration system. A GOOD calibration system. Noticed the emphasis on that one word? We dare say room correction really deserves a bit more than a fleeting consideration when you make your next AV receiver purchase. It’s one of those, either you do it well and it can make a world of difference or don’t even bother at all.

Here’s how we argue our case:

On the surface, a room correction system is just that; a tool that uses a microphone to measure test tones sent through your speakers in order to get the most out of your set-up. But there is a wide variety in how these room correction systems work, what exactly they calibrate and ultimately, the result you end up with.

 

So, what can a room correction system do?

  • It will adjust the relative levels of all your speakers so that the center, mains, surrounds, overhead speakers, and (sometimes) subwoofer are all playing at the same loudness. The better the room correction system, the better this will be applied.
  • Most room correction systems will adjust the crossover point(s) between speakers and subwoofer Again, some are more sophisticated in that job than others. Some only handle very straight-forward set-ups adequately and get really confused about speakers that divert in the slightest from the standard set-up. Dual subwoofers anybody?
  • Some room correction systems will estimate how far your main listening position is from each of your speakers and adjust the delay settings in your receiver or processor accordingly, in such a manner such that the sound from each speaker is reaching your ears at the same time. The better the room correction system, the better it will make sure that all seats in the room are ‘good seats’.
  • The fanciest room correction systems will take it a step further. All the measurements we mentioned above, are used to work out the effect of your specific room acoustics on the performance of your speakers. The systems then apply equalization to the speakers to “correct” issues with magnitude response. We’ll explain this a bit further.

What does this ‘filter’ and ‘equalization’ business mean?

Equalizers are filters that adjust the loudness of specific frequencies.  No room and speaker set-up is ever the same and you will realise that the same note from the same instrument can sound completely different and may require tweaking. In other words, these filters are designed to compensate for the fact that sounds of different frequencies that are intended to reach your ears simultaneously don’t do so, for one reason or another.

To understand why this happens, we need to take you back to high and low sound frequencies and how they respond differently to their environment.

At low frequencies

(20 Hz to somewhere around 200 or 300 Hz), standing waves are your biggest enemy. Because we deal with small enclosed spaces, there is no avoiding standing waves. You can only work with them as best as you can.

At these low frequencies, sound waves  are easily reflected by the walls of your room and subsequently  start interfering with the sound waves coming directly from your speakers.  The result is an increase in volume (peaks) at some spots in the room and a decrease in volume at other spots (nulls).  Change the frequency and the location of your nulls and  peaks changes. Frustrating to say the least…

In other words,  you sit in the left seat of your room and the frequency may be twice as loud as it’s supposed to be, whereas when you change the frequency, it may only be half as loud. Switch to another seat in the room, and the opposite may be true (probably not exactly like that, but you get the point).

What’s even more frustrating is that bass traps and other physical acoustic treatment is not very effective in dealing with this problem. Enter Room correction systems.

The good news is that decent equalization deals well with the peaks. The nulls is a different kettle of fish. When you’re talking nulls, the best way to deal with them is to move your subwoofer around or even better, add a second one. We’ won’t go into the physics here, but we have written previous blogs on how dual subwoofers are a very effective way in dealing with nulls.

As for the peaks, a good digital room correction systems can perform magic.

At higher frequencies

(above 200 or 300 Hz or so), It’s more the quality of the surfaces in the room (as opposed to the shape of the room) that plays a role in how sound will perform in your room. We’re talking about reflection, absorption and diffusion.

This is where a fair amount of the adverse critique against room correction comes in. The reason for that is that the human ear is subjective: certain frequencies are louder than others to our ears, despite having the same or even more energy behind it. Our range is around 20-20,000 Hz, and the closer we approach or exceed these boundaries, the softer things sound.

It’s kind of hard to get a microphone to allow for that level of subjectivity and because of this problem, some will describe the result of room correction as ‘dull’ and ‘dead’.

And we would agree with that, if you only took the average room correction systems into account. The fancier room correction systems do a pretty decent job at it, thanks to a higher filter resolution and a smarter application of filters, often ignoring the higher frequencies to allow them to remain in their ‘natural state’.

Rapallo’s ‘audiophile’ Deano was in the ‘dull’ and ‘dead’ camp until very recently he discovered what you can do with a GOOD room correction system. Have a chat with him now…

So you’ve gathered by now that not all digital room correction systems are created the same. We’ve stated earlier that they should be a substantial consideration in your decision for your new AV-receiver. So here’s an overview (not complete by any means) of what’s on offer but these are the ones you are most likely to encounter.

Different Room correction systems on the market:

Audyssey

It doesn’t appear on nearly as many products as it used to, but Audyssey is still probably the first name you think of when you think “room correction.”

Audyssey covers a wide range of ‘steps’ from basic (useless in our book and luckily, it’s not used very often any more), to standard MultEQ (still pretty rudimentary, with  added equalisation for bass included), to MultEQ XT (more precise equalization), all the way to MultEQ XT32 (now we’re talking). There is also a MultiEQ Pro version for professional installation.

The difference between the versions boils down to the number of frequency filters (more precise equalization), the sound frequencies the filters handle and the amount of measuring positions (giving you better sound in a wider variety of seating positions). That said, apart from the Pro-version, Audyssey still doesn’t allow for adjustment for different environments (your AV room vs. my AV room), which as we explained earlier, is pretty important. Audyssey is a one size fits all solution.

You will find Audyssey mainly on Denon and Marantz products.

Dirac Live

Now, now times have changed.  Not that long ago, Dirac was a minor blip on the room correction radar. Fast-forward to 2017, and it’s not only one of the best-regarded room correction systems, it’s also appearing on new gear at an ever-increasing rate. And it makes the other room correction systems scramble to keep up.

Dirac Live can be found on Emotiva as well as Arcam amplifiers.  It’s different from the rest in the fact that it requires a Windows or OS X computer to run.  At this stage, it’s also a bit more complicated than most basic room correction systems. But at CES 2018, Dirac Live introduced an updated version with improved interface and simplified set-up. With what we’ve seen, we can’t wait for it to find the consumer.

As with Audyssey, Dirac Live applies filters that adequately compensate for time distortion (time delay and phase shift).  But it’s really the type of filters used that makes Dirac Live superior over Audyssey. No such thing as a ‘dull’ or ‘dead’ result, instead it’s labelled ‘astonishing realistic’.

At Rapallo, it’s our favourite room correction system and it is one (there certainly are more!) of the reasons why we added Arcam to our offerings. Bart and Deano have been doing extensive testing on Arcam products in the last few days and weeks and it’s fair to say that they have been surprised in all the good ways (And I would like to add that have experience with all of the here mentioned room correction systems, apart from Sony’s).

Anthem Room Correction (ARC)

In the past, we’ve always liked Anthem’s ARC, the downside being that it’s limited to use with rather expensive Anthem preamps and receivers. As we mentioned earlier, unlike Dirac Live, ARC doesn’t work in the time domain, but it does a good job with standing waves. It’s the crossovers that are its weakest point.

The good thing about ARC, is that it allows for a lot of flexibility, unlike Audeyssey.

MCACC

MCACC (or Advanced MCACC) is Pioneer’s proprietary room correction system and it comes in three varieties : basic (no equalization to the sub), Advanced  (adds phase control for each speaker and more advanced equalization), and Pro (dual-sub measurement and correction, advanced bass management for object-based surround systems, and a Precision Distance tool that allows you to adjust speaker distances (and hence delays))

Rumer goes that Pioneer will abandon MCACC in the future and instead will jump on the Dirac bus.

YPAO (Yamaha Parametric Room Acoustic Optimizer)


YPAO, as you may have guessed from its name, is Yamaha‘s proprietary room setup system. YPAO comes in two varieties: one is simply called YPAO, and the other is called YPAO R.S.C. The former measures speaker levels and delays, whereas YPAO R.S.C. also applies impulse response filters to combat reflected sound.

You’ll likely only find YPAO on the lowest-priced AVRs from Yamaha these days, with YPAO R.S.C more commonly found at mid-levels and high-end Yamaha AV receivers. If you’re in the market for a Yamaha receiver, there is one more crucial thing to consider: YPAO R.S.C comes in two varieties–one with multipoint measurements and one that measures from only one seating position. It’s worth it to step up to a model with multipoint measurements.

Digital Cinema Automatic Calibration (DCAC)

Another proprietary room correction system found is Sony’s DCAC which comes again in several varieties. Sony doesn’t publish much in the way of clear information about what it does or how it works. The results have a reputation (we haven’t used a lot of Sony AV receivers to be honest) to be average at best. It sounds to us that Sony is more interested about the tick in the box on the specs than in actually getting it right. Harsh, but hey….

Room EQ Wizard


And finally, a popular solution for DIYers is Room EQ Wizard (or REW). It’s free, it does a good job but it can be pretty daunting, since the software doesn’t hold your hand in the slightest. That said, there are tons of great video tutorials out there, as well as extensive help files on the REW website. We regularly use the Room EQ Wizard with the  mini-DSP UMIK-1 calibrated microphone.

I know, this blog turned out on the long side. But we didn’t want to be overly superficial on the subject. We stick with the ‘do it well or don’t do it at all’ motto.

 

Source: Home Theater Reviews, Parallel Home Audio, Dirac Live, Yamaha, Pioneer, Sony, Anthem