The appropriate word somehow seems to be ‘Beast’ as the initial description for this, the Denon AVC-X8500H AV amplifier. Let us explain why.

Equipment
So, imagine a home theatre amplifier — not strictly a receiver, as there are no radio tuners in this unit — with each amplifier channel rated at 150W of output. That’s into eight ohms, across the full audio bandwidth, and with just 0.05% THD (measured with two channels running at a time). Now imagine this amplifier had not five of these channels, not seven, not nine... not even 11, as does the almost-equally leviathoneesque Marantz in a few pages time. Just 11? No, the Denon AVC-X8500H AV amplifier has 13 amplifier channels. Thirteen!

Does that not make it a beast? We reckon it does. The unit, says Denon, incorporates its ‘custom-made DHCT (Denon High Current Transistors) discrete monolithic amplifiers’, and all amplifier channels support four or six-ohm speaker loads, in addition to eight ohms, via an advanced menu setting.

So why 13 channels? In fact the maximum it supports in any one mode is 11, in a 7.2.4 Dolby Atmos or DTS:X configuration. But you can use the spare channels for front wide speakers for a 9.1.2 channel configuration. Or you can use one of them to drive a centre ceiling speaker, used when the unit is switched to the Auro 3D sound processor, which requires a ‘Voice of God’ speaker of this nature. Auro 3D is an added cost extra for some of Denon’s lower-priced receivers. It’s included as standard with this one.

For that matter, you can use the extras to drive a second zone, even while going the full 7.2.4 hog in the main zone.

As a top-of-the-line AV amplifier, it has all the other goodies you’d expect. There’s support for three zones. Facilites for automation. Plenty of HDMI (4K, HDCP2.2) and analogue audo and coaxial and optical digital audio inputs. There are two main zone HDMI outputs, plus an extra one for another zone.

And there’s some protection for the future. Denon even says that it will be offering a ‘hardware and software’ upgrade to HDMI 2.1 at some point (the earliest HDMI 2.1 hardware is expected in September), though this won’t be free. Why HDMI 2.1? This will permit the amplifier to pass through 8K video. Yes, 8K. TVs with this higher resolution have already launched in Japan and Europe, though of course there are plentyb of questions over what content will come out in that format, and how. Still, when it happens, your Denon AVR-8500H will be ready.

And there’s plenty of network stuff with all the usuals like Apple AirPlay, DLNA, Spotify Connect and internet radio. The amplifier comes with the HEOS multiroom system inside, and it’s worth downloading and installing that app on a smartphone because it adds additional streaming services, such as TIDAL, and the ability to operate as part of a HEOS multiroom set-up.

The Wi-Fi is dual-band. There is Bluetooth, though this only has only the basic SBC codec.

And here’s something genuinely new. Later this year the amplifier will receive a firmware upgrade so that it supports Amazon’s Alexa Smart Home Skill for Entertainment Devices. So if you have an Alexa-compatible smart speaker you’ll be able to control the amplifier’s basic functions by voice. Apparently it will work to control volume, power, muting, playing and pausing music, switching inputs and playing streaming music. (Of course even with smart speakers voice control ceases to be useful once music or movies are playing, because it can’t hear you over the noise. But we didn’t get to test this, as the firmware required is not yet out.)

Performance
As usual with Denon, the amplifier has a comprehensive wizard to guide you through setting it up. One section of this was speaker calibration, and the unit did an excellent job of setting the correct sizes. The Audyssey MultEQ XT32 requires a minimum of three microphone positions, and you can use up to nine. A cardboard microphone stand is included in the box.

At the last stage of calibration, the amplifier asked if we wanted Audyssey Dynamic EQ switched on, and had ‘Yes’ as the default setting. We chose ‘No’, and recommend that you do the same. We guess we’re getting tedious on the subject, but while technically very clever, this is effectively just a very fancy ‘Loudness’ control, adjusting the frequency response according to volume level. But the organic signal processor in your brain automatically does that. If you have this additional adjustment on, subjectively the sound is being massaged twice; it sounds artificial.

Note, this is not the same as the Audyssey MultEQ XT32, which corrects for room and speaker inaccuracies in tonal balance. In most cases that should be used. And you get a choice there of the outcome you want. By default it adjusts the output to a ‘Reference’ setting, which includes ‘a slight roll off at high frequencies ... optimized for movies’. But you can switch the whole thing off, or have it produce a flat frequency response, or leave the front left and right speakers alone, while adjusting the rest to match.

We only use one subwoofer, but if you have two the Audyssey calibration will separately adjust their level and timing, and then apply EQ to them as well so that the bass is balanced across their range as well.

There’s one other Audyssey feature you may consider using. It’s called Audyssey LFC, for ‘Low Frequency Containment’. Bass frequencies penetrate barriers more easily than mids and highs, and seem to travel further. The better your subwoofer, the more likely you are to disturb neighbours with it. Audyssey LFC ‘dynamically monitors’ the audio and removes the very deep frequencies which most penetrate walls. So as not to leave a hole in the listening experience, it ‘applies psychacoustic processing to restore the perception of low bass’. We were thinking this probably means doing things like filtering out, say, 16Hz tones and boosting 32Hz tones by an equivalent amount. Details on precisely which frequencies are eliminated aren’t given.

This fascinated us. We dug into that setting, and plugged the amplifier’s LFE output into an analogue to digital converter so that we could record the output. Then we fed the amplifier with copious amounts of pink noise and recorded what the amplifier delivered out of the LFE channel with the different settings.

First, with Audyssey LFC off, the output was at maximum in the 10 to 15Hz range, and fell away quickly above 30Hz, in part because pink noise diminishes at six decibels per octave, in part because we were using a stereo signal, so the bass was that redirected to the subwoofer from the left and right channels, and the crossover for that was set to 40Hz. Then we switched on Audyssey LFC, and found that this then allowed us to choose a ‘Containment Amount’ from seven different levels. The default was 4. For each of those levels, there was a brief burst of deep bass, albeit at a very much reduced level, but that only lasted for about a third of a second, and then it fell away to an even lower level. The highest output setting — Containment Amount 1 — reduced overall output by 20 decibels. Amount 4 reduced it by 26 decibels. That seemed to us to be overdoing it.

Still, pink noise and bass redirection are complications. So we figured we’d try some program material. So into our Blu-ray player went our go-to disc for abusively high LFE levels: Titan A.E. We actually clipped the recording significantly on one peak with LFC off. The peak level with LFC 4 was -17dB. The average level with it off was -15dB, with it on was -31dB. In other words, there didn’t seem to be much bass left when we switched on Audyssey LFC.

But the proof is in the listening. Maybe there was some magical subjective reconstruction of the filtered content? Sadly, no. The sound of Titan A.E., compared A/B, was as though the subwoofer had been pulled out of the system.

Occasionally, when viewing something late at night, we switch off our subwoofer to avoid annoying our neighbours. We’re not sure that Audyssey LFC offers much over that. Especially, we note, since to switch it on requires 16 keystrokes on the remote to navigate through the Audio menu to it. More if you want to change the containment level. This is the kind of thing that belongs in the Options pop-up menu.

So, again, you’ll probably want to just leave this off. And, really, if you can avoid it you don’t want to interfere in any way with the utterly magnificent performance delivered by this unit. We won’t go into too much detail for reasons of space. We’ll simply note that we’ve never heard our movies, or our music, sounding better. We tended to use the Pure Direct mode for stereo music, especially when listing to vinyl via the amplifier’s phono input. This cuts out all processing.

We did discover something about this amplifier right at a critical moment in the movie Dunkirk (is there any moment in this movie which isn’t critical?) on Ultra-HD. You see, the amplifier switched off. We were alarmed, but then we remembered that ten minutes earlier a message had flashed up on the screen saying that something would be going to sleep in ten minutes. But what? Everything has an on-screen display. We didn’t know if it was the amplifier, the projector or the Ultra-HD Blu-ray player which was giving the message. Turned out it was the amplifier. And it turns out that there’s a key on the amplifier’s remote control labelled ‘Sleep’. We must have somehow tapped it twice to invoke the function.

The network music handling was sure and comprehensive. Our Direct Stream Digital — DSD 64 and DSD128 — and our FLAC tracks up to 24 bits and 192kHz sampling, were handled perfectly. The amplifier showed up as an available speaker in the Spotify app on our phone. An iPhone sent music to the amp via AirPlay. And it all sounded wonderful.

Conclusion
The Denon AVC-X8500H is a premium home theatre amplifier for those who really don’t want to compromise on their experience. If you’ve got that kind of money, we highly recommend it.

Denon AVC-X8500H 13-channel AV amplifier
Price: $5999

+ First-class performance
+ All the amplifiers you’re ever likely to need
+ HEOS inside
+ Future-proof

- Choose some functions e.g. LFC with care

Tested firmware: 7740-4061-7151-2044
Power: 13 x 150W into 8 ohms (20Hz-20,000kHz, 0.05% THD, two channels driven)
Inputs: 8 x HDMI, 3 x component video, 5 x composite video, 6 x analogue stereo, 1 x phono, 1 x 7.1 analogue, 2 x optical digital, 2 x coaxial digital, 1 x USB, 1 x Ethernet, Wi-Fi, Bluetooth; IR in, RS-232C
Outputs: 2 x HDMI, 1 x component video (assignable), 1 x composite video, 1 x 15.2 pre-out, 15 pairs speaker binding posts, 1 x 6.5mm headphone, IR out, 2 x 12V out.
Zone: 1 x HDMI, 1 x component video (assignable), 1 x composite video, 2 x analogue stereo, assignable amplifiers
Other: 1 x set-up mic,

Dimensions (whd): 434 x 195 x 482mm
Weight: 23.3kg
Warranty: Three years