Saturday, 9 January 2021

REVIEW / MEASUREMENTS: ELAC Debut 2.0 A4.2 Atmos Speakers

Well, with the pandemic of 2020/2021, one thing that has changed markedly in my family is that we're spending way more time watching movies and miniseries at home this past year. In fact the last movie I watched at the local "cineplex" was 1917 right before the Oscars on February 9, 2020. As such, 2020 has been a year of microwave popcorn, Netflix, Amazon Prime Video, Disney+ and the occasional UHD Blu-Ray played on my Oppo UDP-205 with the family on the sofa.

Wanting to use the Energy C100 bookshelf speakers elsewhere (see what I was doing here), I figured it was time to grab a pair of actual "Atmos elevation speakers". Not unexpectedly, the ELAC Debut 2.0 A4.2 Dolby Atmos Add-On Speakers were on sale before Christmas which you see in the image above.

This is the first time I've had any ELAC speakers in the home. The speakers are actually not large, but they shipped in a larger-than-expected box. Well nestled in foam protection.

The speakers themselves when looking towards the driver are about 7" x 9.25" and sloped with the rear higher up (speaker connectors located) about 5" versus the front at 2.4".  The speaker is enclosed (no ports). I did not try to pry the grille off to have a look at the drivers. It's one of those situations where you can have any color so long as it's black ash. ;-)

The little speakers feel quite solid, and there's a reassuring thud when the sides are tapped. They weigh just over 5lbs each. Aesthetically, they're plain looking with sharp edges. For me, considering I'll be placing them out-of-the-way I don't mind the appearance. However, if you're intending to stick them on top of some elegant looking speakers, these will not look pleasing.

You can see the driver behind the grille. It's a coaxial design with what is described as a 4" aramid fiber (a synthetic textile used in stuff like body armor) woofer with a small 1/2" soft "polymer" tweeter.

I. Measurements

Okay then, let's have a quick look at how these little speakers measure... Given that these are passive speakers, let's have a peek at the impedance graph first:

As a sealed-box design we can see two resonant frequencies correlating with the two drivers, coaxially arranged, at 170Hz and 2.16kHz. Note that the impedance is generally above 7Ω and taking into account the phase, the calculated EPDR (Equivalent Peak Dissipation Resistance) does drop to about 4.5Ω at around 5.5kHz. Compared to many speakers, this should not be particularly difficult to drive. ELAC rates these speakers as 6Ω.

Typical for my speaker measurements, I'll use the Emotiva XPA-1L monoblock as the amplifier. Here's an estimate of the speaker sensitivity with a 2.83V signal, measured at 1m:

In my measurements, I typically just get an average amplitude from 500Hz to 7kHz and am seeing 88.2dB/2.83V/m with these little Atmos speakers. ELAC rates the sensitivity as 85 over the broader frequency range of 180Hz-20kHz.

From the graph above, we can already appreciate that we're not looking at a flat response speaker! Here's the quasi-anechoic graph based on both nearfield and 1m measurements with baffle compensation applied averaging readings +/-30° (captured at 10° increments) around the coaxial driver:

Note that it wouldn't make sense to do a CTA-2034A-style graph since the speaker is not meant to be listened on-axis. Also for technical reasons, due to where the speaker connectors are located, the only stable way for me to measure off-axis is along what would typically be the "depth" axis of the speaker. Here's how it was arranged if you imagine the microphone pointing straight at it and rotated around the horizontal plane:

In this orientation, check out the directivity polar map:

I have to admit that this is a strange looking polar map :-). There's wide dispersion although it narrows quickly from 6-8kHz then widens again. There's some funky stuff happening above 10kHz, especially at 11kHz where on the frequency response, we see a bit of a dip. If you're wondering, ELAC identifies the crossover frequency at 5kHz.

So what's going on here?

Well, remember that these Atmos speakers were not designed to be "high fidelity" transducers like your main speakers with the aim of achieving relatively flat frequency response on-axis or within a typical "listening window" like +/-30°. Check out the Dolby patent for their "Virtual Height Filter for Reflected Sound Rendering Using Upward Firing Drivers". In particular, we see this diagram for a theoretical Atmos speaker:

As you can see, the curve labeled as "908" is basically the theoretical EQ target that these small Atmos modules are aiming to reproduce. On the low end, we see the crossover around 200Hz (the ELAC starts dipping off below 200Hz). And in the high frequencies, Dolby implements a "virtual height filter":
"... derived from a directional hearing model based on a database of HRTF responses averaged across a large set of subjects. The black lines 303 represent the filter PT computed over a range of azimuth angles and a range of elevation angles corresponding to reasonable speaker distances and ceiling heights. Looking at these various instances of PT, one first notes that the majority of each filter's variation occurs at higher frequencies, above 4Hz. In addition, each filter exhibits a peak located at roughly 7kHz and a notch at roughly 12kHz..."
While not precisely as described, for the ELAC, above 4kHz we do in fact see a local peak at around 7kHz and a dip at 11kHz. The measurements for these speakers also show a dip around 2kHz which is not part of the Dolby specification.

There have been controversies around whether the HRTF is needed. I don't know if that question has been resolved with any satisfaction over the years.

In the time domain, here is the step response:

Looks like the drivers in the coaxial arrangement are both in positive acoustic polarity (that first dip down is ringing from the miniDSP UMIK-1 USB microphone rather than the tweeter).

And here's the Cumulative Spectral Decay (CSD) over 3ms with around 25dB dynamic range:

Not great, but fine for what it's suppose to do I think. There's a bit of extra energy around 5.9kHz (cursor) and 11-12kHz.

Here's the linearity graph from 70dB to 100dB SPL:

This looks good. With the 0dB error point at 85dB SPL, the amplitude stays linear up to 100dB SPL with <1dB error down to 70dB SPL.

To be honest, distortion isn't really all that important here. Remember, these are meant to be ceiling bounce speakers so direct on-axis sound with low distortion isn't the intent although distortion should not be horrific. Here's a peek at the THD with the frequency sweep:

Notice I put the cursor at the -40dB level to indicate 1% harmonic distortion. Remember that these speakers roll-off below 200Hz so the high distortion down there is a reflection of this. For the most part THD stays <1% except around 2kHz. Fine as "effects speakers", I think.

The ELAC Debut 2.0 A4.2 speakers came as a pair in a box, how well do the speakers match?

We can compare a few parameters:

Right and left speaker impedance looks alright. Not precise matching of the resonance peaks but this is not uncommon.

We can see the high frequency HRTF filter effect in both speakers. For the most part we're looking at around 1dB difference between the speakers although that 2kHz dip showed more variation.

Finally we can have a look at the CSD graphs for the two speakers:

Again, relatively equivalent with the resonance in the 5.5kHz region highlighted with the cursor for both speakers. Notice that it's not necessarily the loudest resonance peaks that take the longest time to settle.

Overall, as "budget" speakers the variation isn't unexpected and would not be a problem especially again given the fact that these speakers are pointing at the ceiling!

II. Subjective

Alright then, so the question is "How do these sound?"

Before I get to that, here's the before and after of where I put these Atmos speaker in my sound room (refer to the previous article with wide angle pictures of the room):

Before with Energy bookshelf monitors acting as rear Atmos channels:

After with the ELAC Debut 2.0 A4.2 in position:

As you can see, the ELACs are comparatively diminutive compared to the Energy C100 bookshelf monitors. I used the Yamaha RX-V781 (latest version 2.85 firmware) receiver's YPAO calibration for speaker amplitude and relative distances with a little volume fine-tuning. Due to their frequency response, I made sure the crossover is at 200Hz to reduce localization. I set the receiver to treat these as "Dolby Enabled SP" speakers.

Ideally these are supposed to be "Front Presence" speakers but since my Paradigm Signature S8 main speakers have a top curvature, these would not sit properly so I placed these above and behind instead (IMO, putting these on the front speakers would have looked very ugly!). Note that I have 8' drywall ceilings which work pretty well; this is one situation where higher ceilings will not help. In use, I've also angled the rear height up a bit so the angulation is closer to 25° which empirically improved the subjective sense of sounds emanating from above. Remember that sound cues that contribute to spatial perception are not simply measured by steady-state frequency responses so while these sounded good in my room after some tweaking, I would not claim that an atypical upper rear placement like this would work in all circumstances; you'll just have to listen for yourself.

Well folks, these sound pretty good in my set-up. Although I cannot instantaneously A/B the sound between these and the Energy C100 speakers, I believe that the HRTF filter actually "works" for me. Atmos demos like "Amaze" definitely showed off the extra height information with raindrops coming down from the ceiling. dts:X likewise used the extra height channel and can be experienced in their demos like "Object Emulator" and "Out Of The Box". The Dolby Atmos 2016 demo Blu-Ray also has clips like "747 Takeoff" and "Helicopter Demo" which are essentially pure overhead speaker show-off material - the "Helicopter Demo" particularly playing overhead moving side-to-side and you can hear the up-and-down as it virtually hovered.

For standard 5.1/7.1 material, Dolby Surround Decoder and DTS Neural:X do a pretty good job of "upmixing" the sound into the Atmos/height channels for an extra bit of 3D "volume". I found this useful for concert videos, for example, playing George Michael: Live in London (Blu-Ray, DTS-HDMA 5.1) had a good amount of the audience sounds spread into the height channels to improve the sense of being in the Earl's Court Arena (which has since been demolished). Likewise, A-B listening to the difference between the CD release of Leonard Cohen's Songs From the Road compared to the BluRay rip of the DTS-HDMA 5.1 tracks like "Hallelujah" and "Closing Time" reminded me of just how much can be achieved with multichannel when recorded and produced well. For my Yamaha receiver, "cross-upmixing" seems to work fine, I could play a Dolby TrueHD-Atmos track with height decoding while set to DTS Neural:X and it sounds impressive.

I watched portions of movies with Atmos soundtracks - stuff like Mad Max: Fury Road (enveloping sounds of general mayhem!), Avengers: Endgame (climactic final battle always enjoyable), Ford v Ferrari (realistic airplane flyover, car crashes), Ghost In The Shell (techno soundtrack, deep bass, plenty of immersive portions), and Spider-Man: Into The Spider-Verse (love the extra sense of spaciousness when Spidey swings around, also very intense bass).

Likewise, the aggressively remixed INXS Kick 30 Blu-Ray (check out "Guns In The Sky") certainly added more space to the music. Perhaps as expected, The Beatles' Abbey Road (50th Anniversary Super Deluxe Blu-Ray) didn't gain as much from a more subtle Atmos re-mix/master. Hmmm, Miles Davis' Kind Of Blue would be neat to hear if it's ever released as the Atmos remix.

III. Summary

I thought it would be fun to measure an example of these up-firing Atmos speakers. As you can see with this ELAC, we're looking at a transducer with limited frequency response (-3dB at 150Hz), with a high-frequency filter that is adjusted based on studied HRTF to enhance the psychoacoustic perception of height. Even though I'm placing them above and behind me in my soundroom (instead of at the front pointing up from the main speakers), the effect is still enjoyable with both a sense of sound coming from the ceiling and some side-to-side stereo separation. As usual, make sure the angulation makes sense and the reflected sound appears to be projecting down to the listening position. While up-firing speakers like these are a fine compromise for me (for now!), needless to say, the ideal setup in a small home theater would be 4 channels mounted directly on the ceiling.

These ELAC Debut 2.0 A4.2 Atmos speakers can be found for around US$200-$250 so are one of the least expensive but I think still respectable models out there. Remember, for the most part, the Atmos channels mainly carry ambiance audio so often the effect is subtle. In a typical movie, there will only be episodes when they'll be engaged with high level discreet content; typically during special effects or intense action scenes. At these times, the movie experience certainly will be enhanced by the perception of vertical space that these channels provide.

Given room variations and the fact that these upward-firing Atmos speakers are not heard directly, I honestly don't think there's a need to be obsessive about speaker brand matching. I suspect your receiver's calibration system will be able to set levels, crossover points, and relative speaker time delay just fine.


Relatively few new major movie releases this past year, I guess studios are waiting to release the "good stuff" when ticket sales comes back at some point in 2021. Hopefully the last Daniel Craig Bond flick will be good currently scheduled for April release for example.

In 2020, Tenet was enjoyable I suppose if you don't mind the time turnstile/inversion and "reverse entropy" sci-fi premise. As usual, the sound editing in these Nolan movies including very loud background soundtrack can be a little maddening! The good thing about watching this in a home theater on BluRay is that you can turn on the subtitles and catch more of the dialogue, providing a better chance of figuring out what the heck is going on in the movie. :-) If you've seen the movie and still trying to figure it out, here's a good "beat-by-beat" explanation.

I loved Disney/Pixar's Soul recently as a highlight for an otherwise very quiet year for movies.

Recently a friend suggested that I check out Charley Crockett's Welcome to Hard Times (2020) CD. Pretty good album with some memorable lyrics and melodies if you're into more traditional country music; not the pop-country crossover stuff. I see that TAS had a review. I wish this album were recorded with better technique instead of just DR8 and sounding so "flat" with little dynamics, little 3D depth, and average perceived resolution. More like a boringly average 2.5/5 for "Sonics" for a new recording, not the 4/5 awarded by TAS which is beyond generous IMO.

You would think that after all these years with improvements in audio technology in recording hardware including hi-res ADC, high quality playback DAC, "ReplayGain" type normalization with streaming services implemented (so Loudness War mastering is moot), artists and audio production folks could achieve something good especially for a mostly-acoustic album like this. Wouldn't it be nice to simply make something one could take pride in with excellent sound quality for posterity beyond just immediate record sales?! But no. That's not what we have with most new recordings.

Enjoy the music... And movies... Stay real instead of regressing into fantasy when life demands. Stay safe out there, for all kinds of reasons.


  1. Happy New Year Arch!

    As usual another excellent article! Cool that the HRTF works for you. It does seem a bit odd to have that "built-in" to the speaker. With a proper setup stereo system, one can also get a sense of height by checking out AudioCheck's LEDR sound test: AudioCheck's LEDR sound test

    Meaning of proper stereo set up, both left and right channels direct sound are arriving at one's ears at exactly the same time, with the same frequency and timing response (over time). The LEDR effect is impressive for a 2 channel setup and how old it is. Too bad it is not multichannel.

    Would love to hear Atmos on your system Arch! I wonder what the odds are for a reunion dinner this summer? And oh yah, still owe you that Keg Steak on that bet I am happy to have lost ;-)

    All the best in 2021 Arch!

    Kind regards,

    1. Hey Mitch!
      Yes, happy new year man... I'd say a summer reunion is probably a high chance event. :-) Though slow starting up, hopefully they'll roll out the vaccine at a good clip and by summer, the better weather should provide a little bit of tailwind to get things in the right direction. We shall see.

      Thanks for the links to the LEDR sound test. Yeah, it's nice having a listen to that; the "UP..." and "OVER" tracks certainly can sound excellent with a good stereo system with excellent frequency & time-domain performance!

      The nice thing about multichannel and discrete speakers of course is that one can still appreciate the positioning of those sounds outside of the sweet spot. Important for the home theater setting with the family stretched across the couch.

      Oh yeah my friend, looking forward to the steak, best enjoyed over a warm summer eve with a cold one and in the presence of great company ;-).

      Take care and happy 2021; been quite the first full week!

  2. Hi Archimago. Firstly I wonder if you could say how you wire in your two subwoofers (front and rear from memory)? Presumably the pre-out from the receiver goes to your pre-amp. Where do the two subs hook in, and where is the cross-over controlled from? Presumably not the receiver otherwise this would not work for your two channel setup! Does this have negative impact in terms of setting up the receiver and balancing the two subs? Sorry if this is something you have answered elsewhere or has a really obvious answer!

    Seconly a wider shout out, does any one know a receiver with a digital pre out. I can't find one but have some old Merdian DSP5000 as my front speakers and some point want to integrate a modern Atmos receiver into my setup. I can't think of anyway of keeping a purely digital chain through fromt he HDMI cable, to the receiver and then onto the DSP5000's for my front L and R channels. Thanks in advance everyone for any thoughts.

    Archimago as ever your blog is awesome... thank you! Best wishes, Nich

    1. Hi Nich,
      Thanks for the question! With regards to the 2 subs, I wrote about that here:

      My 2ndary lower power sub is basically used to help "fill in" some of the nulls I was experiencing in the room at low bass/upper sub-bass from around 30-90Hz at the main listening position; leaving my primary Paradigm SUB1 as the beast that took the sound down <30Hz.

      My Emotive XSP-1 preamp handles whatever is being sent to the 2 front channels whether directly from the stereo inputs or in the "Home Theater Bypass" mode, mirrors the input it receives from my multichannel receiver's preouts (L+R+LFE channels).

      The Emotiva has 2 sub outputs - both an RCA out which is how I'm sending the signal to the secondary Polk PSW111 while the XLR balanced sub output feeds the Paradigm SUB1. As such they're carrying the same signal to both subs.

      Specific settings like output volume, phase, and crossovers are set on the subs themselves using trial and error plus "educated guesses" along with lots of REW measurements (doing this "by ear" would be exhausting and not as accurate). And as you can see in the post, the last part I do after getting the placement and physical adjustments done is the DSP for final frequency and time-domain optimization when I'm using the dual subs in stereo "music mode".

      For multichannel, I'm using the Yamaha's YPAO auto set-up with a little bit of fine tuning like for the Atmos speaker crossover frequency. I'll let the receiver determine summed amplitude of the 2 subs averaged over the multiple listening positions it takes a reading from across my sofa. For the subs, I think I've left crossover at 80Hz.

      Good question about the receiver with digital pre-out. Alas don't know myself from any first-hand experience. However, you might want to look at surround processors. For example, since I mentioned my Emotiva preamp, I had a quick look at their Emotiva XMC-2 which has both TosLink and coaxial S/PDIF digital outputs as well as an insane number of analogue outs! I see the older XMC-1 also has the digital outs...

      Not sure if this would serve your purpose but worth a look to make sure the output suits your needs (presumably what you're looking for is stereo PCM 2-channel 24/96 or so).

      Good luck and wishing you great sound!

    2. Nich,

      I am/was in your situation not too long ago. I also have front speakers with digital (and analog) inputs that are used in surround as well. Obviously it's nice if the signal can be digital all the way, but it's a little difficult to combine that with a typical surround setup. Incidentally, I ended up buying the Emotiva XMC-2 that Archimago mentioned. It does have some digital outputs, although the manual states that they "should not be considered to be bit-perfect copies of the digital input signal" (I guess it's related to copy protection etc).

      Currently I'm using a cheap old Behringer studio device to convert the standard analog out from the Emotiva to digital for the front speakers and that works okay. But the digital-to-digital of the Behringer hasn't been reliable for me so I haven't actually used the digital outputs of the Emotiva. I could give it a try though if you're interested. I'm thinking of either skipping that conversion altogether and use plain analog, or buying a better converter, something like Archimago's RME for example.

      Perhaps I should note that I haven't been very pleased with the Emotiva so far, considering that it's the most expensive part of my surround setup. It took a long time with many firmware updates to make it work decently, but it still has various issues, for example not working reliably with my Chromecast Ultra. Also, it's super-slow and the remote is awful, and the objective measurements seem underwhelming according to Amir/ASR. What I do like though is Dirac (of course, that's why I bought it!) and all the configuration and input/output options. It was simply the cheapest Dirac pre-amp that was available where I live.

  3. Thanks for that TENET article. That movie was even more ridiculous than I realized!!