Introduction

Our Quest for a Whole Home Audio System

When we moved into our current home almost a decade ago, we created a ‘whole home’ audio system using a combination of traditional A/V receivers and Ethernet-based HDMI transmitters. This included three AVRs, each of which supported two audio zones (for six total zones). We installed passive in-wall, in-ceiling, and outdoor speakers. Over the years, we upgraded our AVRs several times to the latest models. However, they never worked as a cohesive, whole home audio system.

Our issues included:

• the AVR mobile app’s focus was individual receivers, not the whole-home,
• the software (AVR firmware) for Internet streaming sources wasn’t regularly updated,
• there wasn’t an easy way to access our lossless CD-quality iTunes collection,
• the AVRs’ zone 2 inputs were limited to analog sources,
• as a result, audio across zones 1 and 2 were not synchronized,
• voice-control (e.g. Amazon’s Alexa, Apple’s Siri, or Google’s Assistant) was not an option, and
• the receivers, while feature-filled, ran very hot, which is a real issue in closed environments like a media cabinet.

To synchronize the audio, I tried a number of workarounds, including Apple Airport devices for Airplay v1 and, later, Chromecast Audio discs for Google Cast. All of these were cumbersome, even when Airplay and Google Cast functionality were supported natively (on zone 1) in later AVR models.

Our Introduction to Sonos

When the Sonos One speaker was introduced in 2017, we were so impressed that we ultimately purchased 16 Sonos Ones and 3 Sonos BOOSTs. We also bought a Sonos Connect:Amp for the speakers in my garage workshop. When Sonos introduced the Beam, we purchased five–along with SUBs–for each TV. In addition to its other features, the Sonos Beam enabled us to deploy a new, primarily 5Ghz SonosNet network, which permitted us to sunset our Sonos BOOSTs.

Having found an ideal whole home audio solution in Sonos, the missing link in our home was how to power our passive in-wall and ceiling speakers as well as our patio speakers. While it was possible to use the Sonos Connect:Amp for this, the Connect:Amp design was almost a decade-old (a rebranded ZP120), relatively low-powered, and not suited for a centralized, rack-mounted installation.

Sonos now brands itself as “the easy-to-use wireless home sound system.” But, clearly there is still a need to connect passive, wired speakers to that whole home system. Therefore, many Sonos users and custom installers were excited to see Sonos’ reinvention of their connected amplifier, the new Sonos Amp.

Design

Compared to the Connect:Amp, the new Amp is more streamlined: it is shorter, wider, and deeper. The exterior is plastic with a matte black finish. The dimensions of the new Amp are 21.7 (w) x 21.7 (d) x 6.4 cm (h) (8.54 x 8.54 x 2.52 in). It weighs 2.1 kg (4.6 lbs). On the front, there are three capacitive touch sensors: volume, play/pause, and previous/next track, similar to the top of the Sonos One and Beam. There is also a IR remote receiver so that you can control the Amp with your existing TV remote control. Like Henry Ford’s Model T, the Sonos Amp is available only in black.

The Amp includes custom banana plug pairs that accept 10-18 AWG speaker wire. Since our cable runs already had traditional gold banana plugs, I just plugged them directly into the Amp.

The Amp’s updated dimensions make it better suited to rack-mounted installations. And, it’s even possible to stack Sonos Amps as if they were Legos.

Features & Technology

Connectivity

On the back of the the Amp, there are connectors for four passive speakers, a self-powered subwoofer, two Ethernet cables, an AUX line-in for audio devices, and an HDMI port. The primary value of the second Ethernet port is to daisy-chain an adjacent Amp. With the HDMI, you can connect the AMP to your TV using HDMI-ARC, and create a 2, 2.1 or 4.1 home theater. If your TV lacks an HDMI-ARC output, then you can use an HDMI-to-optical audio adapter. The RCA AUX line-in is suitable for both line-level inputs and for turntables, though a RIAA preamp may be required. Inside, the Amp also has a WiFi chip for connection either to your wireless LAN or to SonosNet.

DDFA Amplifier

At the heart of the Sonos Amp is a Qualcomm direct digital feedback, class D amplifier (DDFA) amplifier.1 Class D amplifiers are more power efficient, with a smaller form factor, than traditional A/V receivers. Thus, they don’t radiate as much heat and do not require a fan.

Historically, Class D amplifiers suffered several drawbacks:2

• pulse-width-modulation (PWM) signals could be noisy and imperfect,
• some Class D amplifiers suffered voltage drops at high volume, and
• a digital-to-analog (DAC) convertor might be needed.

To address these, DDFA uses a digital PWM modulator, monitors amplifier voltage, and eliminates the DAC. The closed-loop architecture eliminates audio hiss and distortion at high volumes.3 Additional benefits include dynamic compression and soft clipping management.

While the old Connect:AMP generated only 55W per channel, the new Amp generates a maximum of 125W per channel at 8 Ohms. The Amp has a signal to noise ratio of 116dB, with less than 0.1 percent total harmonic distortion.4 Sonos reportedly built its own custom discrete output stage in order to balance efficiency and heat management inside the Amp’s chassis. Additionally, the Sonos reportedly uses a custom designed power supply for the Amp.5

Audio Codec Support

If you are using the Sonos Amp primarily for a home theater, you may be disappointed by the limited native support for audio codecs. For example, there is no support for Dolby Atmos including Dolby True HD or Dolby Digital Plus. Similarly, there is no support for DTS:X, DTS-HD Master Audio, DTS 96/24, Neural:X, DTS-ES, or DTS Express. Like the Beam, the Amp only supports PCM stereo and Dolby Digital 5.1 surround via HDMI ARC. None of this would be an issue if the Amp supported Dolby MAT 2.0–or at least Dolby Digital Plus–over HDMI-eARC (see below). If so, that would permit a settop box like the Apple TV 4K or apps running on that device to decode proprietary audio codecs to Dolby MAT 2.0.

Potential Deployment Topologies

2.0 & 2.1 Channels

In my opinion, the optimal use cases for the Sonos Amp are one or more two-channel deployments including: free-standing speakers, bookshelf speakers, wall-mounted speakers, or ceiling speakers, potentially complemented with a subwoofer. Sonos is deliberately targeting the Amp for the “installed solutions” (i.e. professional installer) market. For example, Sonos highlights its partnership with Sonance for “architectural sound” in-wall, ceiling, and outdoor speakers. The Sonos Amp can be wired to support up to three pairs of speakers.6 While you may need a professional installer to fish speaker or Ethernet cables through your walls, the Amp is certainly easy enough for a novice to connect and configure.

Below, I describe how we connected our Amps to our home’s legacy speakers. If you are an audiophile, you might wish to pair higher-end speakers to the Sonos Amp for a green-field installation. Here is a great overview of the best passive speakers for 2019. As you can see, it is easy to spend thousands of dollars of high quality speakers. Our family’s focus was ensuring that every room is connected to our Sonos system; we can upgrade our passive speakers over time.

Free Standing Speakers

In my bachelor days, I bought expensive Polk VM30 free standing speakers. These tower speakers have 1″ fluid-cooled aluminum tweeter, two 4″ mineral-filled polypropylene midrange drivers, four 4″ mineral-filled polypropylene woofers, and four 4″ planar bass radiators. I tested them with the Sonos Amp and they sounded fantastic, but I recommend pairing them with either a Sonos AMP or a self-powered subwoofer.

In-Wall Speakers

In our living room, we have Polk Audio RC85i 2-way premium in-wall speakers. These popular speakers have a 20 cm (8 in) woofer and a 2.5 cm (1 in) swivel-mount tweeter. They can handle up to 100 watts. Recessed in the wall, they are ideal for providing ambient sound while talking with guests.

In-ceiling Speakers

In our kitchen, we have Polk Audio RC80i 2-way premium in-ceiling round speakers. Like the RC85i, the RC80i speakers have a 20 cm (8 in) woofer and a 2.5 cm (1 in) swivel-mount tweeter. The ceiling mount works well in our kitchen because we have floor-to-ceiling cabinets.

Garage Speakers

Out in the garage, we have JBL Control 1 Pro speakers. Rated at 150 watts continuous power, they have a 13.5 cm (5.25 in) low frequency loudspeaker and a 1.9 cm (.75 in) polycarbonate dome tweeter. They are wall-mounted, above my workbench. With the garage doors open, we can turn up the volume and play them concurrently with the kitchen and patio speakers for seamless audio between the cooking/eating/outside areas.

Patio Speakers

For our backyard, we upgraded our old ‘rock’ speakers to TIC B03 premium outdoor omnidirectional in-ground speakers. They have a 20 cm (8 in) woofer and a 5 cm (2 in) tweeter. Their power handling is 100W RMS / 200W peak. We buried them both for greater stability and better bass handling. I was surprised by the TIC speaker’s bass response, particularly after adjusting the Sonos Amp’s EQ settings. If, like us, your outdoor speakers are located at opposite ends of your home, then I recommend enabling dual mono mode.

Subwoofer

For indoor deployments, you can pair the Sonos AMP with a Sonos SUB or a self-amplified subwoofer.

4.1 Home Theater Systems

Surround sound home theater configurations with the Sono AMP are supported but are considerably more complex. There is no way to create a 5.1 system because you cannot pair a center channel speaker. Sonos claims that this isn’t necessary due to signal processing, which creates a ‘phantom’ center channel from 5.1 surround sources. It is not clear to me how this differs from typical stereo speaker channel positioning.

If you are creating a home theater system, the Sonos Amp can power the front passive left and right speakers and provide an output to a powered subwoofer. Then, you can add two wireless Sonos Ones for rear surround speakers. But, an important consideration is that your front L+R speakers will not be sonically matched with your rear surrounds. It is possible to add a second Sonos Amp and to power rear passive speakers (like how I used to power four of my Polk VM30 speakers), but this is costly and doesn’t properly balance the sound for a 4.1, much less enable Dolby Atmos format.

Finally, like the Sonos Beam, the HDMI ARC input for the Sonos Amp assumes that your TV is switching between inputs and, frankly, that there are a limited number of inputs. In our home, we have already migrated to using the Apple TV 4K as the sole set-top box and TV input except in two rooms where we have Blu-ray players and in our son’s room where he has an Xbox One. If your household needs more inputs per TV, then you may be better served with a traditional A/V receiver.

Voice Control of the Amp

The Amp does not have any microphones inside. However, like other Sonos speakers, the Amp can be controlled by other microphone-enabled devices such as the Sonos One. Today, that means external Alexa and Siri-powered devices. In the near future, Sonos will also support Google Assistant natively.

For a 4.0 or 4.1 home theater system, you can use the microphones and voice services provided by the Sonos One surrounds.

For 2.0 and 2.1 configurations, I assume (but haven’t tested)  that the Sonos Amp can be controlled using Alexa and an Amazon Echo Dot. In our home, we have committed to Google Assistant and Apple Homekit. Therefore, I hope to control our Amps using Google Assistant and a Google Home Hub (inside) or Google Home Mini (outside) when Sonos supports Google Assistant in the near future.

Airplay

Like the Sonos One and Beam, the Amp supports Apple’s Airplay 2 protocol. This permits you to stream audio from any app (e.g. Amazon, Netflix or YouTube) on your iPhone or from iTunes on your Mac, independent of the Sonos mobile or desktop controller. If you prefer to view album art, you can use an Apple TV as an Airplay source.

Rack-mounting Your Sonos Amps

Sonos’ marketing photos showcase the Amp on top of media cabinets next to high-end turntables or on a bookshelves next to books about art and design. In our home, we are a bit more practical. All of our networking and storage gear is in a central data closet. So, it was logical to rack mount our four Sonos Amps there, too. We could then connect them via Ethernet to our aggregator switch. This keeps them in a secure location, away from kids and pets.

Two Sonos Amps fit side-by-side perfectly in a 48cm (19in) rack. For our rack, we installed the Monoprice Wall Mount Bracket and two Monoprice Single Sided Shelves. They are heavy duty and have a low price.

We then placed two Sonos Amps on each shelf. You have to be careful not to scratch the AMPs because they fit so snugly in the rack. Because our racks are wall-mounted, there is limited access to the back of the Sonos Amps. If you use a similar rack, then I recommend screwing in each shelf and installing Sonos Amps on that shelf, sequentially (i.e. from bottom to top). You should configure each shelf as you go, because the pairing button is located on the back of the Amp.

Cabling

All of the speaker cable runs in our home are either 2 or 4 conductor wires. Russ Christman, our A/V installer, used Honeywell Genesis cables.

Heat Dissipation

Coming from traditional AVRs, I was amazed by the lack of heat emanating from the Sonos Amps, even when densely packed with four Amps played at 80% of their volume. At standby, the Amps are cold to touch. When playing at 40-50%, they are modestly warm. At 80%, they are warm but not exceedingly hot like our old AVRs.

Other Options

If you prefer wall-mount over rackmount, there are several wall-mount options. Flexson sells a wall-mount for four Sonos Amps that looks incredible. Flexson also sells a dock for four Sonos Amps. And, Flexson sells wall-mounts for individual Sonos Amps.

Alternatively, Sanus sells a lower cost wall-mount for individual Sonos Amps.

Configuration Recommendations

Software Tweaks

• If you connect your Amp via WiFi, you must configure your router in 802.11 b/g/n mode. 802.11n only and 802.11ac network configurations are not supported.
• If you have connected your Amp via Ethernet–particularly if you are rack-mounting it–then you should disable WiFi in the mobile app. This is a feature that installers have requested for some time.
• You will definitely want to adjust EQ (currently limited to bass and treble) for each set of speakers. I found the default settings too ‘bright’ on some speakers and too ‘muddy’ on others.
• If you are not using a subwoofer, then you should disable this output. And, you should configure the crossover accordingly (50-110 Hz). Initially, I expected this to be an automatically detected setting (i.e. don’t enable crossover if there is no connected subwoofer), but I found that manually configuring this setting dramatically changed the sound of my speakers.
• If you are using the line-in, you should adjust for the level of your source audio (e.g. turntable, A/V component, Mac or PC).
• If you’re using Sonos Architectural by Sonance speakers, you should go to Settings > Room Settings > Trueplay and identify the Sonance speakers.

My Feature Wishlist

• Trueplay support is limited to Sonance speakers. Similar to Audyssey, I wish that Sonos’ Trueplay would work with any passive speaker. Based on my experience using Trueplay to tune my Sonos Ones, Beam and SUB, I would expect similar benefits to tuning passive speakers.
  • At the very least, it would be good to have more granular equalizer settings, such as a five or seven bands (frequency areas).
• Like the Sonos Beam, the Sonos AMP is limited to Dolby Digital 5.1 or PCM stereo sound over HDMI-ARC. Ideally, both Sonos products would support Dolby MAT 2.0 over HDMI-eARC.
  • In the interim, it would at least be valuable to support Dolby Digital Plus over HDMI-ARC for higher fidelity surround sound.

References

• “Setup, Install, and Getting the most from Sonos Amp.” Sonos.

 

Updated on April 27th, 2019