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Denon AVR-4520CI Receiver Review

By Sonnie Parker

About a year ago I decided to give up my Denon 4311 receiver so that I could give the Onkyo 5508 preamp/processor a spin in my system. The 5508 has performed very well, yet for some reason I have this perception that it is noticeably forward, particularly in the dialog/midrange area. When using it I find myself backing down the center channel output from time to time, depending on the source material. On the other hand, the 4311 gave me the impression it was a bit softer… perhaps more laid back with its sound, most noticeably in that same dialog/midrange area. Ironically I remember having to increase the center channel level on it occasionally so that I could hear the dialog better in movies. With music and video concerts I believe I would have to lean towards the sound of the Denon over the Onkyo. Although I will admit that I have been more satisfied with the 5508 after using Audyssey Pro, which I never used with the 4311. Regardless, both units sound really good in my system and I think most people would be satisfied with either as a processor. Of course neither of these units will be the main focus of this review.

It has been my plan to continue with the 5508 until something else came along that would grab my interest. When the 4520 was first announced it appeared interesting, but I knew I really did not need the amp power and it did not seem to offer all that much more than what the 4311 would do for the price difference. So the plan was to simply be satisfied with the 5508, until it recently caught a bug... the type where it no longer responds to the remote and has to be unplugged over night to reset it. That is a relatively easy fix, and Onkyo even sent me a UPS label to cover the shipping. I had it back within a couple of weeks. In the mean time I got to thinking (always costly)… why not grab a 4520 and give it a turn in my system while the Onkyo is on repair vacation? I can review it and let it serve not only as the processor for my home theater, but also as a two-channel amp for a separate two-channel setup that I have been pondering over. For my dedicated home theater setup I am using external amps for every channel, so the 4520 amps should be ample power for just about any pair of speakers I might want to give a listen. Plus it does have a few extra features that could be fun to tinker with for a few weeks… or months. I attempted to acquire a review unit for HTS, but was told that these are currently on short supply and that review units may be difficult to come by for a few months. We will not let such a minor thing stop us from reviewing one though.

Major Features
  • Nine discrete 150-watt channels (symmetrical monolithic construction).
  • 3D and 4K pass-through technology.
  • Advanced circuitry converts all video signals to 4K.
  • Audyssey MultEQ XT32 with SubEQ HT.
  • Play separate audio and video in two areas at once with multi-room capability.
  • Seven HDMI inputs and three HDMI outputs to connect a variety of devices.

  • Superior Surround Sound and 3D Pass-Through Technology
  • The AVR-4520CI receiver is a 9.2-channel A/V receiver that offers nine discrete 150-watt channels for dynamic surround sound along with dual subwoofer outputs for optimal bass performance throughout your room. You can view 3D movies through your home theater system using the receiver's pass-through technology.
  • 4K Upscaling for Pristine Picture Quality
  • This Denon receiver upscales all video signals to 4K (3,840 by 2,160 pixels), which provides four times the picture quality of 1080p. This enables you to use it with 4K monitors and video projectors.
  • Advanced Functions to Play Streaming Media
  • The AVR-4520CI IN-Command A/V Receiver allows you to enjoy a variety of advanced network content, such as listening to Internet radio and playing media stored on your computer. The AVR-4520CI supports services like Sirius XM, vTuner Internet Radio, Pandora, Spotify, and Flickr as well as Apple's AirPlay technology, which allows you to listen to media from the iTunes library on your iPad, iPhone, iPod touch, PC, or Mac.
  • The receiver is DLNA 1.5 certified and compatible with PCs running Microsoft Windows 7.
  • Optimum Sound with Audyssey MultEQ XT32
  • The AVR-4520CI comes equipped with Audyssey MultEQ XT32 to create an immersive, balanced acoustic profile for your home theater system. Audyssey MultEQ XT32 automatically customizes your home theater to overcome acoustical problems specific to your room, resulting in exceptionally clear sound. MultEQ XT32 uses high-resolution equalization filters, making it ideal for large or odd-shaped rooms. The receiver also incorporates Audyssey Dynamic EQ and Dynamic Volume for comfortable and optimal listening of any source at any volume.
  • Immersive Surround Sound with Audyssey DSX Technology
  • The AVR-4520CI comes equipped with Audyssey DSX. Audyssey DSX expands surround sound beyond 5.1 with more speakers for an immersive and lifelike home theater experience.
  • Assign Power Amps for Different Audio Setups
  • The AVR-4520CI supports up to 9.2 channels for surround playback. You can reassign the amplifiers from the two surround back channels to power a pair of front height speakers, or, to achieve higher-quality sound for two-channel stereo playback, you can configure the AVR-4520CI for front bi-amp operation.
  • Four-Source, Four-Zone Capability
  • The AVR-4520CI can be the centerpiece of a whole home system, including the main room plus three additional playback areas, with independent sources available for each zone. It supports up to three different video sources and three different audio sources.
  • Enjoy Two Different HDMI Sources Simultaneously
  • The AVR-4520CI incorporates true multi-zone HDMI audio/video distribution with the inclusion of its HDMI matrix switching functionality. Equipped with three HDMI outputs (two parallel and one discrete), the AVR-4520CI allows for the connection of up to three different HDMI-equipped displays. The receiver can send two different HDMI feeds to two displays at the same time directly from the receiver, eliminating the need for costly external switches or remote control complexity.
  • Connect Your HDMI-Equipped Devices
  • The receiver is outfitted with seven HDMI inputs and three HDMI outputs (two parallel and one discrete) so you can enjoy high-definition audio and video from a variety of HDMI-compatible devices, such as set-top boxes, Blu-ray players, game systems, and media players like Roku and Apple TV. An HDMI input on the front of the receiver offers a quick, convenient connection for portable devices such as camcorders and HDMI-equipped smartphones and tablets. The front panel also has a USB port to directly connect your iPod, iPhone, or USB drive to the receiver. A flip-down door on the aluminum front panel neatly hides controls and connections when you're not using them.
  • Intuitive Graphical User Interface and Remote App
  • The AVR-4520CI features a Setup Assistant along with a graphical user interface that simplifies the initial setup and daily operation of the receiver. In addition, the receiver supports the free Denon Remote App, which lets you operate the receiver's main controls from your iPad, iPhone, iPod touch, or Android smartphone.
  • Denon Link HD Jitter-Free Audio Transmission Technology
  • The AVR-4520CI also incorporates Denon Link HD, Denon's proprietary jitter-free audio transmission technology, which is designed to work with Denon's DBT-3313CI Universal Blu-ray Player.
  • Built-In IP Control Allows for Custom Integration
  • The receiver also features versatile custom integration-friendly features, such as RS-232 and IP Control for third-party controllers for seamless integration with home automation systems.
  • Product and Warranty Information
  • Sporting a sleek black finish, the receiver measures 7.66 by 17.09 by 16.64 inches (H x W x D) and weighs 36.38 pounds.
  • The Denon AVR-4520CI IN-Command A/V Receiver is backed by a three-year warranty.
  • What's in the Box: AVR-4520CI IN-Command A/V Receiver, remote control with batteries, HD Radio antenna, power cable, Audyssey setup microphone quick setup guide, and owner's manual on CD.

Power Amplifier Section

  • Front L/R
    • 150 W + 150 W (8 ohms, 20 Hz - 20 kHz, THD 0.05 %)
    • 190 W + 190 W (6 ohms, 1 kHz, THD 0.7%)
  • Center
    • 150 W (8 ohms, 20 Hz - 20 kHz, THD 0.05 %)
    • 190 W (6 ohms, 1 kHz, THD 0.7%)
  • Surround
    • 150 W + 150 W (8 ohms, 20 Hz - 20 kHz, THD 0.05 %)
    • 190 W + 190 W (6 ohms, 1 kHz, THD 0.7%)
  • Surround back / Front height / Front wide
    • 150 W + 150 W (8 ohms, 20 Hz - 20 kHz, THD 0.05 %)
    • 190 W + 190 W (6 ohms, 1 kHz, THD 0.7%)
  • Dynamic Power
    • 170 W by 2ch (8 ohms)
    • 280 W by 2ch (4 ohms)
  • Speaker compatibility: 4 - 16 ohms
Pre-Amplifier Section

  • Input sensitivity: 200 mV/47 kohms
  • Frequency response: 10 Hz - 100 kHz — +1, –3 dB (DIRECT mode)
  • S/N: 102 dB (IHF-A weighted, DIRECT mode)
  • Distortion: 0.005% (20 Hz - 20 kHz) (DIRECT mode)
  • FM section
    • Tuning frequency range: 87.5 - 107.9 MHz
  • AM section
    • Tuning frequency range: 530 - 1710 kHz
  • General
    • Power supply: AC 120 V, 60 Hz
    • Power consumption: 780 W
    • Power consumption in standby mode: 0.1 W
    • Power consumption in CEC standby mode: 0.5 W
    • Power consumption in network standby mode: 5.1 W

  • In
    • HDMI (Front: 1): 7
    • Component (Video): 3
    • Composite (Video) (Front: 1): 4
    • Analog Audio (Front: 1): 7 (Phono: 1)
    • Digital Audio (Optical): 2
    • Digital Audio (Coaxial): 2
    • External Analog Audio (7.1 ch): 1 set
  • Out
    • HDMI Monitor: 3 (Zone4:1)
    • Component (Video) Monitor: 2 (Zone2:1)
    • Composite (Video) Monitor: 3 (Zone2:1)
    • Audio Lineout (Media player): 1
    • Audio Preout (Zone2, 3): 2
    • Audio Preout (SW): 2
    • Audio Preout (11 ch): 1 set
    • Phones: 1
  • Other
    • Denon Link HD: 1
    • iPod / USB (Front/Rear): 2 (selectable)
    • Network (Ethernet): 4
    • Setup Mic jack: 1
    • FM Tuner Antenna: 1
    • AM Tuner Antenna: 1
    • Remote Control (In/Out): 1/1
    • Trigger out (DC12 V 150 mA MAX): 2
    • RC-232C: 1
Approximate Dimensions:

  • Height: 7-21/32"
  • Width: 17-3/32"
  • Depth: 16-41/64"
Approximate Weight:

  • Unit: 36 lbs 6 oz
  • Shipping: 44 lbs

MSRP $2,499
Accessories4less $1,699
ebay $1,699

Link to 4520 Downloads (Manuals, Guides, IR Codes)

The 4520 will be processing the following equipment for this review:

Emotiva XPA-1 Monoblocks powering MartinLogan Prodigy Loudspeakers (Mains)
Emotiva XPA-3 Multi-Channel Amp powering MartinLogan Theater (Center) and MartinLogan Ascents (Surrounds)
Custom Built Subwoofers (Dual front and rear)
Behringer DSP1124p (Parametric EQ on Subs)
DirecTV C31 Mini-Client (Networked to our DirecTV Genie)
Denon DP-300F
Panasonic PT-AE4000U Projector
128" Elite 2.35:1 Screen
Universal MX-890 Remote Control

Test equipment used is the IBF Akustik microphone/mic amp, a miniDSP UMIK-1 Mic (calibrated by Cross Spectrum Labs) and a Galaxy CM-140 SPL meter. Software is of course Room EQ Wizard, available free here at Home Theater Shack.

It was unfortunate that the first unit I received had an issue where it would drop the Dolby Digital signal and center channel, requiring a restart of the unit. Fortunately there was another unit sitting at my office the next day after reporting the issue, so it was not too much of an inconvenience. The second unit has worked flawlessly.


I will compare the Denon 4520 to the Denon 4311 and the Onkyo 5508 throughout this review simply because the 5508 was the last processor in my system and the 4311 preceded it. In my opinion the 4520 is cosmetically more appealing than the 5508 and the 4311. I think it looks better without all the buttons, although I do like the blue backlit volume dial on the 5508. My favorite looking unit right now is the Marantz 7005, but because it lacks several features it is not up for consideration... and as the ole saying goes, beauty is only skin deep. The 4520 does not have XLR balanced preouts like the 5508, nor does it have THX processing, which both are insignificant to me, yet important to others. It was nice to see that the front panel display can be set to Off, 25%, 50% or Full brightness. The 4520 is about the same height as the 5508 and one inch taller than the 4311. Thankfully Denon chose not to include all of the logos, writing and indicator lights on the front, cleaning it up considerably over the 4311. I have never been fond of all the buttons on the front of the 5508, and rarely have I ever used any of them, so I am all in favor of the cleaner look the 4520 offers. Below is a side by side shot of the 4520, the 5508 and the 4311, respectively.

So what do you get in the 4520 that will cost you from $400 to $900 more than the 4311 (depending on where you buy)? As mentioned above, cosmetically an inch taller unit and a cleaned up front face. It also weighs 1.6lbs less. On the rear you will get an extra Zone 4 HDMI output (3 outputs total) and a 4 port Ethernet hub. You will get 10 more watts per channel in power and what Denon says is a better designed layout of the power amp blocks (see the Internal Amps section in this review). Feature wise you get an Interactive Owners Manual, an improved GUI, three 32-bit 400 MIPS DSP Processors, customizable/assignable amplifier circuitry, 4K Video Upconversion (3840 x 2160), Multi-Zone Video including an additional zone, Network Streaming, Denon Link HD, DTS Neo:X, LFC (Low Frequency Containment), InstaPrevue, Spotify, and Apple Airplay is built-in and does not require the $50 upgrade. Although I would choose the 4520 over the 4311, I am not sure I can fully justify the increased cost for these additional features, but you can obviously decide for yourself if the extras are worth it to you. Personally it is not a mandate that I justify the cost of everything I buy.

Connections, Setup and Features

I suppose Denon is of the opinion that anyone purchasing this receiver will have a computer since the manual only comes on a CD in PDF format. If you are one of the rare individuals that does not have a computer and need a manual, you will have to find a place to print it. Then again, if you do not have a computer, there is a possibility that you will not be reading this review. I copied the PDF manual to my desktop and actually like having it on my computer because it is easier to navigate and find sections I am looking for… and there are interactive reference links on nearly every page that are easy to access with a simple click. While it may come in handy to help you better understand features and operation, you probably will not need it for the initial connection and setup.

Connecting a receiver to speakers and sources... and setting it up, is a fairly simple task for most people that are familiar with the process, but for the novice, Denon has truly made the on-screen setup extremely simple with step by step instructions and pictures. Setup will ask you a few questions along the way, instruct you to make appropriate connections, request a press of a few buttons on the remote… and will guide you screen by screen, step by step. It will also guide you in setting up each source one by one and verifying its proper operation, including easy setup of your Internet connection. Below are a few of the setup screen shots.

The Internet connection is obviously a big plus for those using a media server and perhaps wanting to get that media to different zones. The Internet connection also allows firmware update/upgrade notifications to be displayed on-screen if you choose to turn on that feature. There is also a Web Controller feature that allows controlling the settings of the 4520 by accessing the IP address of the unit, which is found in the Network/Information menu. Using Setup via the Web Controller shows all the options of each setting, whereas using the on-screen menu requires selecting the setting and cycling through the options with the remote control arrow buttons. Each zone can be controlled from your laptop, which you could take from room to room (zone to zone) for convenience in changing sources, et cetera. The Web Controller feature also offers the ability to save various settings and configurations so that you can compare them later if you change out other equipment or want to test different setups.

The on-screen GUI is semi-transparently overlaid on the source image, which is nice, especially for the Picture Mode feature. Pressing the Option button on the remote control will bring up the Picture Mode option, which will allow you to see the results of the various preset picture settings in real time (Off, Standard, Movie, Vivid, Streaming, Custom). There is also an InstaPrevue option where you can display sub screens (think picture in picture) on the main screen to preview playback video of the HDMI inputs connected to this unit. You can display various video inputs in a single screen to switch input sources such as Blu-ray, DVD, and GAME... all while viewing them on sub screens. Below are a few of the menu screen shots.

Overall, the GUI for the 4520 is much easier to navigate than the 5508 and the 4311, which I always thought was rather aggravating on both. I miss the 'Home' button on the 5508 remote that brought up a small window where I could make adjustments without having to go deep into the menu, which somewhat made up for my dislike of the navigation of the full menu. One particular example is that I use both subwoofer preouts, so the 'Home' button gave me the ability to adjust both subs simultaneously for various sources. With the 4520 I have to adjust each sub independently from within the Menu/Audio/Subwoofer Level section. However, since I have the Universal MX-890 learning remote control, and Denon furnishes a full complement of discrete codes via their IR Codes List, available from the 4520 downloads page, there are options to make things easier. This allows me to create all kinds of short cuts, including a convenient subwoofer level control macro. If you plan to do the same you will need the Denon Pronto Hex Generator ( View attachment DenonHexGen.zip ) and a good understanding of how to use these tools, although I found them relative easy to figure out.

For the Video/Output Settings I set everything to Auto where available and use the Video Conversion to convert the DirecTV signals that need converting. It is turned off for the BDP-93, which does its own conversion on lower resolution material. This unit will upconvert to 4K if you happen to be one of the lucky ones owning a 4K display. The Custom selection within the Picture Mode option allows the ability to customize video settings if a particular source were to need some help. This may be helpful on standard definition satellite TV, cable or streaming movies. You never know what kind of signal is delivered from those sources and nearly every instance is different from channel to channel and movie to movie. I do not personally worry about it too much, but the ability to make adjustments is there if needed. The HDMI handshake during changing of channels on DirecTV is painfully slow… not that I do a lot of surfing. I can probably blame that more on the DirecTV setup than the 4520, but it was better than this on the 5508.

Audyssey XT32 is included along with SubEQ HT, allowing easy setup of two subs in different locations. Before running Audyssey, it is good to setup your Amp Assign first, since the default is not always the right choice for everyone, and changing it after completing Audyssey will require you run Audyssey again. I also selected the channels to measure so that it would not be taking time attempting to measure speakers that are not present. The auto setup had me set the level of my two subs to about 75db and then it proceeded to set the size, levels and distance of all speakers… next it measured the response of each speaker and did its work. After it was all done I checked the settings and as usual it set my fronts to Large, which I changed to Small in the settings. It also had the crossover points set lower than I desired. Dynamic Volume and Dynamic EQ were automatically turned on after calibration; however I turned off Dynamic Volume because I do not see the need for it in a dedicated and well insulated home theater room. Later on I will note that a firmware upgrade changed the Audyssey defaults, so if you get a unit that already has the latest update, it may be slightly different than what you read here.

The 4520 also includes an additional Audyssey feature, LFC (Low Frequency Containment), which dynamically monitors the low frequencies and prevents those lower frequencies from traveling through walls. Unfortunately it is hard for me to test this in my room with the thickness of my walls (about 9 inches)... it is sound proofed fairly well. Occasionally my wife tells me she hears what sounds like distant thunder, and then it is only when I get a little hot with the volume control, or watch Cloverfield. However, there is no doubt it works because it basically cuts out all of the bass. How well it works will depend on the level of bass you choose to remove. I can see this coming in handy especially if you do not have a dedicated and well insulated room, and/or you do not want to risk disturbing the family at a particular time of the day or night. The graph below shows three different settings and the measured response. The blue response you see is the default LFC level 4.

The 4520 has an option for Audio/Dialog Enhancer that will adjust the amount of emphasis on the center channel to make dialog easier to hear. The options are Off, Low, Medium and High. This feature would have come in handy with the 4311. I tested the Enhancer on the 4520 during a couple of movies and while I did not need it, it does seem to work as expected.

The 4520 has several HDMI options including Auto Lip Sync, Dual HDMI Output and HDMI Pass Through (even when the unit is in standby power mode)… and more options depending on the source and other settings.

Speaker configuration does include the impedance options of 4, 6, or 8 ohm speakers. As previously mentioned, I have been tossing around the idea of setting up a two channel system for the fun of it. The extra channels in this unit can be used for that setup so that I no longer have to buy another amp. The unit can be setup to automatically use the two channel system when Direct or Stereo mode is selected. However, it never fails that in my home theater system the subwoofer levels have to be increased with music material, at least for my taste. This is where that subwoofer level macro that I mentioned previously comes in handy.

Overall, it really does not get much easier to setup a fully featured receiver than what Denon has done with the 4520.

After turning off the unit one time and turning it back on there was an update available, which took several minutes to complete… about 45 minutes on my slow DSL. In less than an hour I was back fiddling with the features after the upgrade, which downloaded, updated and restarted power on the 4520… and went back to playing my David Gilmour In Concert DVD. I decided to go ahead and rerun Audyssey and noticed a few changes while running it. This time it asked me if I wanted to enable Dynamic Volume, while on the first setup it automatically turned it on. The menus may have changed slightly, but I did not note any major changes. All my other preferences that I had previously set remained as they were prior to the update.

I downloaded the free Denon Remote App to my iPhone 5. It can be customized to your liking and might be useful more so for remotely controlling the unit in other zones. I did not get into testing it, but like the Web Controller feature, it might come in handy for operating the receiver while in other zones. At least there are a couple of options for how you may want to control the unit. Below are a few screen shots of the app.

Audyssey XT32

Generally I will only measure the main listening position when I run Audyssey setup, although I may take 3-4 measurements. For the most part I am the one who uses the home theater more than anyone else, and I am usually 'all by myself', so what you will see in most of these measurement graphs are the results from the main listening position. Audyssey did a fairly good job of equalizing the sound in my room, particularly the bass. I believe I ultimately preferred the Audyssey Bypass L/R setting where it does not equalize the main front speakers, although I am not absolutely sure I was hearing a very noticeable difference from the other Audyssey settings. This unit is Audyssey Pro ready, but I did not use it (I may later). Below are several measurement graphs showing the various results of Audyssey and comparisons of a few of the settings offered.

Something I have been wanting to do for a long time is a measurement test from the main listening position based on two different Audyssey setups. The first setup I measured only the main listening position as I normally do. The second setup I measured eight different listening positions. Then I compared the response of several listening positions to see which seating position benefits the most from each setup. The big question is, did the main listening position sacrifice response because of the other measured seating positions being included? After I ran Audyssey setup as normal and took four measurements at the main listening position, I then used REW to measure the main listening position response, the response of the seat to the side of the main listening position, one of the back row center seats, and one of the back row outside seats. Next I ran Audyssey setup again starting with seat one at the main listening position, and moving to each of the other six seats (two more on the front row and four on the back row) then one last measurement at the main listening position to complete all eight measurements. Below are the measured response graph comparisons. Note that the legend will show a "1" or "8" at the end of each description, indicating which setup measurements were used for that response. For example, the first response graph is comparing the main listening position responses based on the "1" measured position versus the "8" measured positions.

As we can see, the main listening position does sacrifice a fairly significant 10db hole from about 17Hz to 40Hz when measuring eight different listening positions during Audyssey setup. While I did not do any listening to the responses of this particular test, I would suggest that the bass would have suffered significantly and it would have been very noticeable. Looking at the other measurements, I also do not believe that it would have improved the sound enough (if any) in the other seating positions to warrant the sacrifice of the main listening position response. Personally, and particularly with my situation, I will stick with measuring only the main listening position during Audyssey setup. This is something you may want to test for your room, as it is definitely not a given that it is better to measure more seating positions.

Is Audyssey all you need in your system for equalization? Maybe and maybe not. I have read some comments in the past, even a couple of reviews on some other Audyssey equipped receivers and processors, where users or reviewers have complained that after they ran Audyssey setup, the sub-bass levels were set too low. This will be the case if you have an extreme peak in your raw low frequency response. Before Audyssey equalizes the response, it sets the levels based on pink noise, and those levels are going to be influenced by peaks that may already exist in your response. If you have a 10-15db peak in your low frequency response, Audyssey reads it in the pink noise level setting and reduces the overall subwoofer level. Then it equalizes the peak, removing it and leaving your sub levels low. Audyssey also does not make the best use of its filtering when you have a large peak in your response, as we will see in the comparison graphs below. This is a good reason to invest in an inexpensive measurement microphone and download Room EQ Wizard for free, so that you can measure the response in your room to determine if you may have any major response peaks that can be fixed before running Audyssey setup. Peaks can be dealt with in a few different ways. If you have the freedom to do so, you can move your sub enclosures around and see if that helps, although you may sacrifice in some other areas. It is also much easier to deal with peaks than it is nulls. Acoustical treatments (bass traps) are an option, although it can be difficult to find any that will deal with large peaks below 80Hz, such as the 50Hz peak you see in graph #1 below. GIK Acoustics has recently added Scopus Tuned Membrane Bass Traps to their arsenal, which could very well be a viable option for situations like this. In many cases the easiest solution is to use a parametric EQ. Quite a few of your manufactured subs, plate amps and even some pro amps will include one or more bands of PEQ, which is perfect for fixing problems like you will see below. Otherwise you will need to look at other options such as the Behringer 1124p or something similar. Another inexpensive solution is the miniDSP, which will give you more features and options than the Behringer units. The idea is to cure those peaks prior to running Audyssey so that Audyssey is not using all of its resources trying to fix issues that it is not that good at fixing. Below are graphs showing examples of how fixing the issue prior to running Audyssey will improve the response. In graph #1 we have a very large peak at 50Hz and another not so large peak at 100Hz. Graph #2 shows the results after running Audyssey prior to dealing with the peaks. Notice how the low frequency response drops off tremendously below 50Hz. Sure, you can increase the subwoofer levels (+6dB in graph #3), and you will end up with even more boomy bass around 50-60Hz... and you are not fixing the real issue. This is simply not a good result and would be most undesirable for me. If we add a couple of filters in a parametric EQ (BFD 1124p in this case) to cure those peaks (see graph #4), we end up with a response that Audyssey can work with a lot better. After running Audyssey again we can see the very different response we get in graph #5... a much improved response.

I do not know exactly how Denon, or other receiver manufacturers could accomplish it, but it would be nice to have a few bands of parametric equalization to use prior to running Audyssey. I suppose that could also be an option that Audyssey could implement in their next version of Audyssey (XT64?).

Internal Amps

I mentioned at the beginning of the review that I did not necessarily need the internal amps of the 4520 because I have external amps. However, I decided to connect my MartinLogan speakers to the internal amps and see how they would sound. I think my main concern was if the amp section could handle the Prodigy mains without any issues, particular at louder volumes. The Prodigy’s are rated at 4 ohms with 91db sensitivity and drop to 1 ohm at 20kHz. The Theater center speaker might be a concern as well with 90db sensitivity and reaching 3.1 ohms at 140Hz. The next few weeks would tell the story. Denon says their amp design has symmetrical monolithic construction placing the power transformer in the center of the unit and the power amp blocks at each side to better achieve separation for all channels… all amps are discrete and can produce the same power output. In the Amp Assign settings I was able to assign the Front Height speaker output to the Front channel and use the bi-amp feature of the 4520 to power the Prodigy’s.

Once I switched to the internal amps I had to run Audyssey again. When I run Audyssey setup I use my boom mic stand with a clip to hold the Audyssey mic at ear level in the main listening position. Once finished I can simply release the Audyssey mic from the clip and swing the clip down to hold the measurement mic... which coincidentally and conveniently places both mic tips very close to the same location. To make sure I was getting fairly equal response measurement comparisons between the external and internal amps, I ran Audyssey again on the external amps. I then made my normal adjustments that I always make (switching main speakers from Large to Small and changing the crossover settings) and measured the response with the default Audyssey equalization settings (Audyssey and Dynamic EQ On). I then connected my speakers to the internal amps and preceded to take the same steps as above. The level on the processor never changed. Below is a response comparison between the external amps and internal amps.

Interestingly the internal amps seem to have created a slight midrange nudge, although I could not tell you that I noticed any difference. If I could have done a direct comparison by switching between the two, I suspect I would have noticed the level changes. However, I think small response variances like this are very difficult to hear unless you have those so-called "golden ears"... and there is no doubt I do not possess them.

Listening and Watching

At the time of my writing this review I have been using the internal amps for several weeks now. I am not finding any reason to reconnect the external amps. I have pushed the system ridiculously hard (intentionally – not that I ever listen at those levels) with music and movies, and there do not seem to be any issues whatsoever that I can hear. I am completely sold on the amps in this unit being able to handle my MartinLogan speakers with ease. Whether the unit can handle nine speakers that are difficult to drive all at one time, I do not know, but for my 5.2 bi-amped system (7 amp channels used) it is doing a fine job.

If you are looking for a bunch of fancy words to describe what I have experienced with the sound and video on the 4520, you are going to be disappointed because I have never bought into such descriptive attributes. My brother and I watched several movies on this system with both the external and internal amps. Taken 2, Total Recall, Ghost Protocol, Battleship… and I watched several on my own. Both of us thought everything sounded excellent and as it should. I also watched one of my favorite concerts, David Gilmour in Concert, and it sounded great, as it usually does. For listening I grabbed one of my favorite music CDs, Yello – One Second (remastered) and I ended up listening to it twice … a few of the songs three times. I also listened to Flim & the BB’s – Vintage BB’s, Jonny Lang – Lie To Me, Spyro Gyra – Dreams Beyond Control, Adele – 21, Led Zeppelin – Mothership… and on 180 gram vinyl, Steely Dan – Aja. I listened to a few songs via Internet Radio just for kicks. Once again everything I listened to sounded excellent… and every bit as good as it has sounded since I have owned this MartinLogan speaker setup. The wide sound stage and excellent imaging has not been removed in the least bit. I can not definitively conclude without AB testing, but I do not perceive that the 4520 is quite as laid back as the 4311, yet it still does not seem to be quite as forward as the 5508. It is indeed just right for my taste. One issue I was experiencing with the 5508 was a very low-level hum when listening to the turntable. I assumed I was going to have to eventually ground the turntable to the unit, but with the 4520, as soon as I placed the needle down on Aja I noticed there was no hum, to my pleasure. Overall, the 4520 does not in any way hinder the video or audio from presenting itself as it should in my system, if anything it only improves it.

Summing It Up

In conclusion, I am thoroughly impressed with this unit. It has about all the features you could ask for in a receiver/processor and ample power to accommodate most any speaker system. I initially intended on reviewing it and then selling it, but instead I have already sold my Onkyo 5508, XPA-3 amp and XPA-1 monoblocks. I keep thinking to myself that the 4520 seems to be a little on the pricey side, but if you consider what any other processor with the same features would cost you and then add the expense of amplification, the 4520 price actually sounds like a bargain. I think the most surprising part of my experience with the 4520 has been its ability to drive my MartinLogan speakers effortlessly. I had almost given up on ever trying receiver power because I have always read and heard that the Prodigy’s pretty much needed at least 300 watts of good clean power to perform their best. I will have to disagree with the naysayers, as I find it hard to get any better than what it is right now with the 4520 the only power amp source in my system. Excellent job Denon!

For discussion of this review, please use the Denon AVR-4520CI Review Discussion Thread
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