Secrets of Home Theater and High Fidelity - Best Of Awards 2015

Denon AVR-X4100 A/V Receiver Review Highlights

The X4100W is Denon’s most affordable AVR designed for Dolby Atmos immersive sound, which Chris Eberle discussed in depth for Secrets earlier this year. The X4100W is a few levels up Denon’s hierarchy in performance and price from the Denon X2100W Gabe Lowe reviewed for Secrets last fall. In addition to Atmos, the X4100W’s enhancements over the X2100W include more powerful amplifiers and better Audyssey room correction. The X4100W supports two fewer channels than the Marantz AV7702 pre-pro I reviewed last spring. But like Marantz’s AV7702, the X4100W features Audyssey’s “Platinum” signal processing package, a very intuitive setup routine, and an excellent iOS Remote Control app

Denon AVR-X4100 A/V Receiver Review

Denon AVR-X4100 A/V Receiver Highlights Summary

  • Dolby Atmos and Audyssey Platinum room correction at an attractive price
  • Upfiring height speakers increase listener immersion into movies and TV
  • Intuitive setup routine dramatically reduces scope for user error
  • Excellent free iOS Remote Control app
  • Very flexible and user-friendly amp assignment
  • Dolby Surround upmixing is great for movies and TV, but less so for 2-channel music

Introduction to the Denon AVR-X4100 A/V Receiver Review

Denon is always one of the first AVR makers to leap forward with new technologies. They were one of the first AVR makers to offer room correction, dynamic loudness compensation, and synthesized height channels. They were one of the first AVR makers to build in Wi-Fi and music streaming options. The X4100 is, in this respect, typical Denon. It adds Dolby’s new Atmos immersive sound technology, and a user can also add Auro 3D capabilities at extra cost if her system can accommodate high-mounted effects speakers. (I highly, highly recommend any Denon X4100W purchaser who can install “true” height speakers spring for the Auro upgrade.) Best of all, Denon didn’t skimp on sound quality despite all of these bells and whistles. The X4100W’s internal amps act much beefier than the AVR’s trim 28 lb. weight implies, and its preouts have a low noise floor.


Power and Processing

  • Design: 7-channel A/V Receiver
  • Power Amplifiers: 7 x 125 Watts RMS into 8 Ohms, Two Channels Driven
  • Dolby Atmos (7.1.2 or 5.1.4), Audyssey DSX, dts Neo:X, 6-channel DSD; Auro Decoding Optional, with Paid Upgrade
  • Dolby Surround (and Auro-3D, with Paid Upgrade) Immersive Sound Upmixers
  • Maximum Number of Output Channels: 11 (7.1.2 or 5.1.4, with Two Subwoofers)
  • Audyssey Platinum Suite (MultEQ XT32, Dynamic Volume, DynamicEQ, SubEQ HT, LFC) with Microphone and Microphone Stand; Audyssey Pro Compatible
  • DACs: TI PCM 1690 (24-bit/192kHz) with Denon AL24 Processing
  • Quad 4th-generation Analog Devices SHARC 32-bit DSPs
  • Analog Devices ADV8003 Video Processor


  • 8 HDMI 2.0 inputs (7 Rear, 1 Front), and 3 HDMI 2.0 Outputs (2 Main, 1 Zone)
  • Built-in Phono Preamp for Moving-Magnet Cartridges
  • AirPlay Streaming (Audio-only), Bluetooth and DLNA Streaming
  • AM/FM Tuner
  • 6 Analog Stereo Inputs (1 Front)
  • 5 Digital Stereo Inputs (2 Optical, 2 Coaxial, 1 Denon Link HD)
  • Stereo Headphone Output (1/4-inch)

General Features

  • Advanced ISF Video Calibration Controls
  • iOS and Android Control Apps
  • Built-in Wi-Fi and Bluetooth Receivers
  • Dual 12V Triggers, RS232, IR Input
  • Step-by-Step Setup GUI
  • IR Remote Control
  • Control for Two Additional Zones (Stereo)
  • Eco Mode to Reduce Power Consumption
  • Dimensions: 6.6” H x 17.1” W x 15.3” D
  • Weight: 27.1 Pounds
  • MSRP: $1,299 USD (Auro adds $200)
  • Denon
  • SECRETS Tags: Denon, Dolby, Atmos, Auro, Dolby Surround, Auro-3D, Surround Sound, A/V Receiver, Audyssey, AirPlay, Immersive Sound, Upmixing


Design and Setup

From the front, the X4100W maintains the form-follows-function styling of past Denon receivers. Most of the controls, and all of the front inputs and outputs, hide under a flip-down door.

Denon AVR-X4100 A/V Receiver Review

The X4100W’s back panel is no more or less complex than AVRs past. Just different complex.

Denon AVR-X4100 A/V Receiver Review

While the 7.1-channel analog input and switched AC power outlet have disappeared, the X4100W has dual antennae for Wi-Fi and Bluetooth. The back panel has seven of the X4100W’s eight HDMI inputs, and all three of its HDMI outputs. It also has a serial port for control apps and dual 12V triggers for downstream components. The speaker connection options are necessarily more complex than current 7.1-channel AVRs such as the Anthem MRX 510. The X4100W has more pairs of speaker terminals than internal amp channels or possible outputs, to allow for different configurations.

Setup for Denon X4100W was substantially the same as on the Marantz AV7702 I reviewed earlier, albeit with a different color scheme. So the X4100W offers the same intuitive, user-friendly setup experience I enjoyed with the AV7702. See Secrets’ Denon X2100W review and Marantz AV7702 review for extensive screenshots that walk you through setup.

The X4100W adds a very flexible and well thought-out amp assignment menu to the initial setup menu. The X4100W can process 9 channels (plus subs) but only has a 7-channel amp inside. That leaves two channels unpowered in a 7.1.2- or 5.1.4- channel system. Amp assignment allows the user to determine which seven channels use the internal amplifier, and which ones require a separate amplifier. (Amp assignment affects the speaker outputs only: line level preouts for all channels used in a given sound mode are always live.)

Amp assignment sounds confusing, but Denon’s on-screen directions show you exactly what to connect where. The photo below shows Denon’s hook-up instructions for what I think is the ideal setup with the X4100W: front speakers assigned to preouts only for use with an external amp (ideally a three-channel amp that also powers the center channel), and the internal amps powering the less critical surround and height channels. Note that the on-screen display greys out the Front binding posts and all of the preouts to the right of Subwoofer, and illuminates the Front preouts.

Denon AVR-X4100 A/V Receiver Review

The X4100W includes the same “origami rocket tower” Audyssey microphone stand as the Marantz AV7702. While calibrating Audyssey on the X4100W you’ll hear a few relays click between Audyssey chirps.

As on the Marantz AV7702, I found one unfortunate omission in the Denon X4100W’s feature set: no user-accessible acoustic measurement app. Other room correction systems allow users to access the measurement engine for system set-up. A quick measurement app leveraging the included microphone and measurement engine would add immense value to the X4100W, and greatly help X4100W owners optimize their systems before calibrating with Audyssey. Hopefully Denon and/or Audyssey will develop such an app in the future.

I could not test the included remote control. It is IR-based, and our equipment cabinet stays out of the line of sight. But our Logitech Harmony Ultimate remote operated the X4100W perfectly, and a universal remote with macros always beats a table full of component remotes. However, I found Denon’s iOS Remote App easier to use than the Harmony when diving into the X4100W’s setup and adjustment menus. One tip to get the most out of the Remote App: a long press on one of the eight buttons lets you replace that button with something possibly more useful to you. At the very least, I recommend changing one button to the cursor icon.

Denon AVR-X4100 A/V Receiver Review

For this review I wanted to pair the X4100W with upfiring front height speakers, because my review of the Marantz AV7702 explored the new immersive technologies (Atmos, Auro) and upmixers (Dolby Surround, Auro-3D) with a full 7.1.4 setup and high mounted effects speakers for the “dot 4.” Here, I chose 7.1.2 over 5.1.4 because our side speakers are in-walls. While, based on my experience with Marantz’s AV7702, I unreservedly recommend Auro for anyone who can install “true” height speakers, but Auro does not support upfiring speakers. So I did not use Auro in this review.

Why bother with upfiring speakers? My blunt take on Atmos and other immersive formats is: either they can render a compellingly immersive bubble of sound in 5.1.2- and 7.1.2- channel systems with upfiring front height speakers, or they become analogous to 3-D TV to date: enjoyed by some but ignored by most. Most of us enjoy our music and video in multipurpose living rooms, not dedicated spaces. Few enthusiasts will install ceiling or “true” height speakers in their living rooms. But upfiring height speakers are an easier sell than ceiling speakers or high mounted effects speakers. For the majority who keep their equipment up front, the costs of upfiring front speakers are just the upfiring modules themselves and a few feet of speaker wire.

Dolby seems to agree with that reasoning. They’ve dedicated lots of brainpower into making upfiring height effects speakers work, and have several patents to show for it. Also, renowned speaker designer Andrew Jones has now designed upfiring height speakers for two different companies: Pioneer and Elac. Jones’ endorsement of upfiring height speakers strongly piqued my curiosity to try them.

That brings me to a quirk in my setup. I was unable to acquire a pair of certified Atmos Enabled upfiring speakers of similar quality to the rest of my system in time for this review. So just as I set up temporary front height speakers to review 7.1.4-channel, I used “Atmos Enabled-ish” upfiring speakers for this review.

Denon AVR-X4100 A/V Receiver Review

While Dolby understandably reserves the full spec for “Atmos Enabled” upfiring speakers to paying licensees, we can infer from Dolby’s Atmos Enabled literature and other statements by Dolby and licensees that any licensed “Atmos Enabled” speaker must meet three specifications: a patented treble curve, certain directivity standards, and bass down to at least 180Hz. Dolby discloses the required frequency response curve in their patent filings, which I emulated using a miniDSP 10x10HD.

Denon AVR-X4100 A/V Receiver Review

While Dolby publishes the required frequency response, they only release the directivity spec to licensees. But directivity is largely a function of cone diameter, driver placement, and any waveguides used. So I investigated the Atmos Enabled speakers on the market to infer the required directivity. Here’s what’s inside the current-production Atmos Enabled speakers:

-5” coax with post-mounted 1” tweeter (Atlantic Technology)

-3” full-range driver (Definitive Technology, Onkyo)

-3” x 4” coax with 0.75” tweeter (Elac TS3000)

-4” coax with 1” tweeter (Elac Debut by Andrew Jones)

-5” concentric driver with 1” tweeter (KEF)

-4.5” concentric driver 1” tweeter (Pioneer Elite)

-Square array of four 2” full-range drivers (Triad)

Those configurations have one thing in common: symmetry. So small speakers with symmetrical drivers or arrays (i.e. full range, coax, or concentric) should work fine with the right EQ. However, standard 2-way mini-monitors with asymmetric driver arrays i.e. separate woofer and tweeter, may fall outside Dolby’s specification. I used the same KEF 3005SE eggs I used as front height speakers for the Marantz AV7702 review. The eggs’ concentric drivers are similar in size and cone depth to the Pioneer Elite concentrics, and I know their sound well. I set the eggs atop my left and right speakers, with their feet/wall-mounts configured to point the baffle up, and angled them so their on axis sound bounced off our ceiling as shown in one of the Dolby Atmos patents.

In Use

For my listening tests, unless indicated below I used the X4100W’s internal amps to drive my seven main speakers (Pioneer EX and KEF R-Series) and a Pro-Ject Amp Box SE to drive the upfiring speakers (KEF eggs). I used two of my four custom subwoofers, because Audyssey SubEQ HT has two subwoofer outputs. I played digital disks on an Oppo BDP-83, streamed video and lossless 2-channel audio from my MacBook over an AppleTV, and watched broadcast content through a standard Comcast HDTV cable box. As mentioned above, I used a miniDSP 10x10HD (normally my subwoofer processor) to emulate the Dolby upfiring speaker curve. The X4100W’s HDMI output fed our Sony LCD over network cable and WyreStorm HDbaseT baluns.

I engaged Audyssey MultEQ XT, SubEQ HT, and DynamicEQ for all my listening. I know what my room sounds like with just two subwoofers and no room correction or loudness compensation, and I prefer not to listen that way. So a few minutes after I opened the X4100W’s box the Audyssey chirps played over nine speakers and two subs.

Overall, the sound of the calibrated X4100W reminded me very much of the Marantz AV7702 that had recently left my system, especially in the midrange and highs, though the bass seemed more prominent than on the AV7702. I would still appreciate a lighter touch in the treble than Audyssey’s Reference curve, though the Audyssey curve likely benefits movies mixed using a similar curve.

Dialog intelligibility in movies and TV was maybe a little better at low levels compared to my reference Anthem AVR when using the Audyssey Reference curve, perhaps due to the treble boost. However, on music image depth was a little flatter and less layered. Even my preferred Audyssey curve for 2-channel music, Bypass LR, removed a smidge of lushness and palpability compared to Anthem ARC. Still, the X4100W is a solid-sounding AVR generally, and on stereo music in Bypass LR the X4100 sounds a lot like my reference AVR. As for Audyssey Flat, forget it. In my room at least, it sounds horrible.

The X4100W’s amplifier section also impressed me. Our speakers are easy to drive, though the rears are fairly low in impedance. Still, the X4100W had no trouble cleanly driving my speakers to levels requiring a shout to talk to the person one seat over, even when I set the front three speakers to large and cued up Bruckner or Massive Attack on my iTunes server.

Despite the amps’ prowess, in a 7.1.2 or 5.1.4 Atmos/Auro setup I recommend adding a stout three-channel amp to drive the left, center, and right speakers, and using the internal amplification to drive surround and height speakers. If you have to add an amp anyway, why not upgrade your amplification for the most important speakers? The X4100W had no issue driving our mighty ATI AT2007 from its preouts, without any drama or extraneous noise.

You may recognize the movie and music selections I discuss below from my Marantz AV7702 review. I used the same demo material for my critical listening in order to compare/contrast the similarities and difference between a 7.1.4-channel setup with “true” height speakers and a 7.1.2-channel setup with upfiring speakers.

As was the case when I reviewed the AV7702, native Atmos program material is scarce right now. There are, as of this writing, twelve native Atmos Blu-Rays available. My native content comes from the Dolby Atmos demo disk.

Denon AVR-X4100 A/V Receiver Review

I expected more drop off than I actually heard after downsizing from 7.1.4-channel with “true” height speakers front and rear to 7.1.2-channel with upfiring heights. “Leaf” and “Amaze,” trailers often shown before Atmos movies, both offered more precise placement in my home than in the local Atmos cinema. The effects also reached higher up with the upfiring speakers than “true” height speakers. Positional rendering in the “Unfold” trailer was not quite as precise as in 7.1.4 channels with “true” heights, but I only noticed the difference when specifically looking for it. Taken simply as entertainment, both setups offered an immersive bubble of sound. The “Napa Valley Dreams” time-lapse video still sounded great, and its birdcalls hung in the air beautifully. The upfiring speakers may suit such “music plus ambient sounds” tracks better than high-mounted effects speakers, when the recording is mixed natively in Atmos.

Given the paucity of native Atmos content, in the short-term Dolby’s immersive upmixer, Dolby Surround is arguably more important than Atmos itself. I still found Dolby Surround very impressive with movie content, but still have reservations about it for 2-channel music.

Denon AVR-X4100 A/V Receiver Review

As it happens, Comedy Central showed this movie several times while I had the Denon X4100W. So I watched the same forest scene I referenced in the AV7702 review several times. Even in 7.1.2 with upfiring height speakers, Dolby Surround convincingly placed me under the tree canopy. I heard sounds swirling everywhere: front-to-back, side-to-side, and up-and-down. There was no discernable hole in the soundfield, though the scene did not have any flyovers or other such front-rear that may benefit more from rear height speakers. Dolby Surround vividly rendered the sounds of life in and around the forest. While I felt there was little discernable drop off compared to the full 7.1.4-channel experience, when I turned Dolby Surround off and listened to the 5.1 channel soundtrack, the immersive bubble of sound conjured by Dolby Surround collapsed into a donut. I was really surprised how much immersion the two little eggs atop my front towers added.

I also played the scene “Hundert Tausend in Zwanzig Minuten” from the now-classic German action movie “Lola Rennt” (“Run Lola Run”) in Dolby Surround.

Denon AVR-X4100 A/V Receiver Review

This scene features a glass-shattering scream by main character Lola (Franka Potente, probably best known in the US as Matt Damon’s first love interest in the Bourne movies), a ticking clock high on a building, and a telephone card ejecting from a payphone with a beep. Denon’s X4100W and Dolby Surround brought this scene to life. As with the 7.1.4-channel setup, I felt Lola’s scream travel through the air, and the wavefront of breaking glass clearly started above the center channel. The clock’s ticks emanated from a distinct point in space floating between the center, right, and right front height speakers, perhaps a little less focused not enough to affect immersion in the soundfield. I did notice the telephone placement was less precise than in 7.1.4-channel; instead of sounding slightly forward of the right front speaker, it came more-or-less from the right-side speaker.

I also played Radiohead’s “The King of Limbs: Live from the Basement” Blu-Ray concert disk through the X4100W, upmixing the native DTS-HD 5.1-channel track with Dolby Surround.

Denon AVR-X4100 A/V Receiver Review

I chose this disk specifically to evaluate Dolby Surround with upfiring speakers on a multichannel recording in a dead acoustic space. On “Good Morning Mr. Magpie” the soundstage lost some definition and clarity in Dolby Surround compared to 5.1-channel, and I noticed cymbal hi-hats occasionally coming from my ceiling. Phil Selway is an amazing drummer, but he doesn’t have 8-foot long arms! Dolby Surround also tilted the spectral balance a little brighter, just as it did with “true” heights and 7.1.4 channels.

I noticed the greatest contrast between 7.1.2-channel with upfiring speakers on the X4100W and 7.1.4-channel with “true” heights on the AV7702 on Fritz Reiner’s 1957 romp through Dvorak’s New World Symphony with the Chicago Symphony Orchestra on Mercury Living Presence 3.0-channel SACD. The upfiring speakers simply seemed less subtle than “true” heights. The orchestra just sounded fuzzy with Dolby Surround on, compared to Dolby Surround off.

Denon AVR-X4100 A/V Receiver Review

Because of the unevenness of Dolby Surround with music, I listened to 2-channel music without upmixing more often than I usually do. For 2-channel playback I also quickly honed in on Audyssey’s Bypass LR target curve as by far the X4100W’s best-sounding option for music. Bypass LR did what I think a room correction system should do: address the room (i.e. the frequency response at the listening from the upper bass down) without trampling the speakers’ voicing underfoot. Bypass LR works much better in 2-channel than in multichannel, perhaps because Audyssey still equalizes the centers and surrounds up to 24kHz. The benefits of this Bypass LR shone through on “Whole Lotta Love,” from the Led Zeppelin II Super Deluxe Edition, which sounded simultaneously expansive and crisp. And alive!

Denon AVR-X4100 A/V Receiver Review

After some listening to 2-channel and multichannel music, I reached out to Brett Crockett, Dolby’s Vice President, Sound Technology, Research and Development, and relayed my reservations about Dolby Surround’s performance on 2-channel music. He told me that “[Dolby] did extensive listening tests with…music when developing the Dolby Surround Upmixer,” and that “[Dolby has] heard from many who happen to be big 2 channel (upmixed by PLII) fans praise the Dolby Surround Upmixer and now make it their preference for listening to music.”

So your experience with Dolby Surround, either with “true” height or upfiring height speakers, may differ from mine. Listen to recordings you know well in Dolby Surround on an otherwise-familiar system to find out for yourself. But I sorely missed Pro Logic IIx for 2-channel music during my time with Dolby Surround. Fortunately, Pro Logic IIx and Atmos can coexist. Dolby’s Brett Crockett told me, “A manufacturer may choose to license (and integrate) the Dolby Pro Logic Suite in addition to Dolby Atmos/Dolby Surround.” I hope Denon and others do so in future products.

I also found the drop-off from four “true” height speakers to two upfiring speakers more pronounced on music than on movies. To be clear, Dolby Surround greatly impressed me on TV shows and movies with upfiring front height speakers. Often, it created an astonishingly lifelike bubble of sound. I am just less convinced of Dolby Surround’s merit for music.

On The Bench


As I wrote in the Marantz AV7702 review, my AVR and pre-pro measurements focus on the acoustic performance of their signal processing features, such as room correction and loudness compensation. I focus on signal processing because learned audio experts differ starkly about the audibility of harmonic distortion, jitter, and other nonlinear distortions, at least at the levels found in mainstream audio equipment today. However, everyone agrees that large differences in linear distortion, i.e. frequency response, are both audible and significant. Room correction systems differ tremendously in their target curves, resolution, and repeatability. Despite that, third-party measurements of these systems are rare. The X4100W offers Audyssey’s MultEQ XT32 with SubEQ HT and three user-selectable Audyssey target curves: Reference, Flat, and Bypass LR.

For all measurements below, I used FuzzMeasure measurement software (versions 3.3.3 and 4.0) running on a MacBook in Mac OSX Mavericks 10.10.3; a Focusrite 2i2 24/96 USB audio interface and microphone preamp with loopback correction; and a Dayton Audio EMM-6 measurement microphone calibrated by Cross Spectrum Labs for grazing incidence, mounted on a boom stand.

Unless otherwise indicated, all graphs below show spatial averages of six points located within a roughly 5-foot diameter “bubble” centered on the primary listening position. See Earl Geddes and Henry Blind, “The Localized Sound Power Method,” 34 JAES 3, pg. 167-173 (March, 1986), for more on this measurement technique. All six points were identical for each different target curve: I placed the microphone, took a measurement of each target curve, and then moved the microphone to the next position. I made no attempt whatsoever to mimic the Audyssey microphone positions.

As I wrote when this review originally went online, the anomalous bass performance I measured with Audyssey SubEQ HT on the Denon X4100W required further investigation. The good news is that the problem went away after a fresh calibration, as shown below. I cannot explain what happened with certainty, but my best guess is that the most recent firmware update inadvertently corrupted the SubEQ HT filters. Anyone who owns a computer or smartphone knows that software or firmware updates often have unintended effects on seemingly unrelated functions. All graphs below state which Audyssey run the data comes from.

The first set of graphs clusters four frequency response curves together: the baseline (Audyssey Off) and the three Audyssey target curves (Reference, Flat, Bypass LR) offered on the Denon X4100W. All of these measurements come from the original calibration.

Denon AVR-X4100 A/V Receiver Review

Sharp-eyed readers will note that the Audyssey Off measurements differ slightly from those in my Marantz AV7702 review. The speakers and room configuration are the same, but due to external factors both the speakers and listening position were slightly different for the two setups. The Audyssey target curve measurements show that each curve closely mirrors my measurements of the AV7702 from 300Hz up, which shows Audyssey’s technology to be stable and mature. The Reference curve adds Audyssey’s signature upper midrange dip, and boosts the treble from 5kHz – 10kHz on my speakers at my approximately 12-foot listening distance. Bypass LR mimics the Audyssey Off curve above about 200Hz. Audyssey Flat omits the “Audyssey dip” but massively boosts the treble on my speakers at my listening distance. The figure below compares my baseline and Audyssey Reference measurements for the X4100W and the Marantz AV7702.

Denon AVR-X4100 A/V Receiver Review

While the results above the bass were substantially the same, Audyssey SubEQ HT was simply ineffective on the X4100W in my first measurement run. SubEQ HT left the peak at 80Hz basically untouched, and only slightly reduced the larger peak at about 60Hz. It also killed an octave of bass, moving the system -3dB point up an octave, to the low 40s, compared to the “no Audyssey” curve. However, MultEQ XT32 performed exactly as expected above 300Hz.

I did not expect the bass measurements to come out like that, based on my listening experience with the X4100W and my earlier measurements of Audyssey SubEQ HT on the Marantz AV7702. (The AV7702 has the same Audyssey room correction package, and I did all of my critical listening to the X4100W long before I took measurements.)

To figure out what went wrong, I asked Dr. Chris Kyriakakis, Audyssey’s CTO, if the microphones were graded to different tolerances for different products. He replied “Audyssey only makes one consumer microphone so there are no tolerance issues for different price points.” I also asked him if the resolution of SubEQ HT’s correction differed on different components. He assured me there was no difference in resolution, and showed me an example. Dr. Kyriakakis suggested I reset the AVR and re-run Audyssey to see if the problem persisted, so I did.

This fresh calibration restored the smooth and extended bass I expected from Audyssey SubEQ and that I heard during my audition. The graphs below compare the bass frequency response in my room using the X4100W after the original calibration and after the fresh calibration.

Denon AVR-X4100 A/V Receiver Review

The next set of graphs compares the bass frequency response after fresh Audyssey calibration on the X4100W to my previous measurements in this room of Audyssey SubEQ HT on Marantz’s AV7702.

Denon AVR-X4100 A/V Receiver Review

The new calibration and AV7702 measurements show that Audyssey SubEQ HT does a superb job of providing smooth, flat bass down to a 16Hz organ pedal at my primary listening position on both devices. The differences between the X4100W new calibration and the AV7702 come from slight changes in the positioning of the sofa and the speakers, as well as the error inherent in acoustic measurements. SubEQ HT is one of the biggest benefits Audyssey provides music lovers and cinephiles.

The next set of graphs shows the “inverse curve,” or equalization applied to the left speaker and sub during the original calibration, for each Audyssey target curve.

Denon AVR-X4100 A/V Receiver Review

The Reference curve adds a treble boost to my speakers at my approximately 12-foot listening distance from 2.5kHz to 7kHz that peaks at about 4dB, before falling to 2dB boost at 22kHz. The Reference curve also imposes Audyssey’s upper midrange dip. I wish Audyssey would provide an option to turn off this dip without buying Pro calibration. This dip may help speakers with midrange directivity issues, but in my view it does more harm than good on speakers designed for smooth power response. If you use the Reference curve, you’re stuck with the dip.

Denon AVR-X4100 A/V Receiver Review

The Bypass LR curve preserves the speakers’ voicing above 300Hz, a pretty good stopping point for room correction. That is likely why I vastly preferred Bypass LR to Reference (let alone Flat) on 2-channel music.

Denon AVR-X4100 A/V Receiver Review

The Flat curve adds excessive treble boost that not only sounds unpleasant but also can fry tweeters. As you see above, Flat’s treble boost peaked at about 8dB at 22kHz on my speakers in my room. To put that staggering amount of boost in perspective, 8dB is the difference between a 100W amp and a 630W amp! While recorded music and movies rarely have content above 20kHz, due to the dangers of such excessive boost I cannot recommend ever using the Flat target curve.

Interestingly, the X4100W displays the equalization Audyssey applies to every channel except the subwoofer. (Go through the following menus: Speakers > Audyssey Setup > Check Results > Equalizers.) The next figure compares the X4100W’s displayed inverse curve for the left speaker on the Reference target curve to my actual measurement of the inverse curve for that speaker.

Denon AVR-X4100 A/V Receiver Review

The two curves basically agree, though the X4100W’s displayed inverse curve understandably has lower resolution than my 1/12-octave smoothed measurement. The bass is only different because my sweep includes the subwoofers and the Denon curve shows the left speaker only. This agreement, in my view, validates both the on-screen display and power of the localized sound power measurement technique. Good for Audyssey and Denon for giving users an accurate picture of what their software is doing!

Tests of DynamicEQ, not shown, mirrored the results I measured for the AV7702.

Lastly, in fine-tuning the X4100W at the beginning of my audition I found a bug in the Subwoofer Level Adjust control. This bug persisted through all firmware updates and the reset.

Denon AVR-X4100 A/V Receiver Review

It appears that when you turn on Subwoofer Level Adjust, before any level adjustment, the X4100W “forgets” the subwoofer level Audyssey set and changes it to 0dB. So you will get more bass just by turning on Subwoofer Level Adjust if Audyssey attenuates your subs, and less bass if Audyssey boosts your subs. The former is far more likely than the latter with dual subs. During the Audyssey setup menu I set both subwoofer to about 73dB according to the on-screen display, or a little under the recommended 75dB but in the “green zone.” In the final calibration, Audyssey attenuated one sub to -6.5dB and the other to -7.5dB. (These numbers were the same for both calibrations.) The next graph shows the bass level difference between Subwoofer Level Adjust On, with 0dB for both subs as shown above, and Off.

Denon AVR-X4100 A/V Receiver Review

As you can see, the overall subwoofer level rises by about 5dB at “0dB” adjustment just by turning Subwoofer Level Adjust on. There are additional ripples above the nominal crossover frequency, because raising the subwoofer level also changes the complex modal interaction between the subwoofers and mains in the region where both still contribute.

This bug, all told, is minor. Just ignore this optional control. The X4100W gives you other ways to adjust subwoofer level that don’t start by throwing everything out of balance. If you want more bass, use the standard channel level menu rather than the Subwoofer Level Adjust menu to increase the subs’ output, or increase the level at your subs’ amps after running Audyssey.


I reached three epiphanies during my time with the Denon X4100W.

First, any modern AVR is more computer than audio component. While that means capabilities one could only imagine a short time ago, it also means that updates can have unintended consequences. I don’t ding Denon too badly for the Audyssey SubEQ HT issue I measured. There were several firmware updates while I had the X4100W. How often has an update from Apple, Google, or Microsoft inadvertently messed up something unrelated? I see no ground to hold Denon to a higher standard than those companies. Also, a fresh Audyssey calibration resolved the issue. Moral of the story is that if you have an X4100W that’s been in service through several firmware updates, re-run Audyssey to get the bass refinement you paid for. And if you have any AVR or pre-pro, listen carefully before and after any firmware update. If you hear anything untoward after the update, re-run the room correction software as soon as you can.

Second, the gap between 7.1.2-channel with upfiring front height speakers and a full 7.1.4-channel setup with high-mounted effects speakers is, in most cases, very small. Put another way, I found a large difference on movie and TV content when going from 7.1-channel to 7.1.2-channel with upfiring speakers, but relatively less difference between 7.1.2-channel with upfiring heights and 7.1.4-channel with “true” heights. The difference between the two immersive setups comes down to preference rather than a clear-cut “better” or “worse.” At least in my living room, with the program material I tried. I consider that an unqualified victory for upfiring speakers. The effort Dolby put into making upfiring speakers believably project sound from the ceiling paid off. For movie content, at least.

Third, I am still not sold on Dolby Surround to upmix 2-channel music. Compared to the mush older Dolby Pro Logic IIx, Dolby Surround brightens the spectral balance and does not extract hall ambience as well. That was true for a 7.1.4-channel configuration with “true” heights on 2-channel music recordings, and it applies even more with upfiring front height speakers. PL2x had “movie” and “music” modes. Dolby may want to pursue a similar path for Dolby Surround. Alternately, Denon and other Atmos licensees should add PL2x back onto their future products for weirdoes like me who like our 2-channel music upmixed to surround.

Overall, the X4100W stands out to me as a great option for someone who wants immersive sound for TV/movies but takes a purist no-upmixing-allowed approach to 2-channel music. I do think a music-first listener, especially one with an open-plan home who needs ambience extraction to add the spaciousness that early sidewall reflections add in a traditional room, should look hard at an AVR with Dolby Pro Logic II. But the Denon X4100W immerses you in an audiovisual scene in Atmos or Dolby Surround, sounds excellent playing 2-channel music with the Audyssey Bypass LR curve, and is commendably easy to set up and use. I call that a win.