Review Denon AH-D7000 Headphones and Headroom Ultra Desktop Headphone Amplifier - April 2009

of and Home Theater High Fidelity review Denon AH-D7000 Headphones and Headroom Ultra Desktop Headphone Amplifier - April 2009

“... this complete system (...) will absolutely KILL any normal hifi system”

Introduction phone ring when the music is on. People can sneak up on me. On the other hand, my My first “high end” system consisted of Sennheiser HD-595s I use at home for late Sennheiser HD-580 headphones, an original night listening have no isolation, allowing HeadRoom headphone amplifier, an Audio office noise to intrude on the music. The Alchemy DAC in the Box, and a Sony Denon D7000s are the perfect compromise. by chris groppi Discman with an optical digital out. I was They are sealed headphones with some a college student at the time, and there was isolation, which knocks down my computer no way of having a real, properly set up hifi fan and other background noise, but I can system in my dorm room. It was clear to me still hear my phone ring and people can get “... frequency response, at the time, listening to both my system and my attention. uber high end Hifi in shops, that my little tonal accuracy, speed and headphone setup blew away many high dollar I first heard the AH-D7000’s in HeadRoom’s agility and even imaging loudspeaker based systems. A headphone- room at the Rocky Mountain Audio Festival and soundstaging (...) are based system is by far the least expensive in 2008, and decided that I just HAD way to experience truly great sound. Many to review a pair. They were, by no small truly spectacular.” of us can’t afford a hifi system costing tens of margin, the best sounding headphones in the thousands of dollars. While the Denon AH- HeadRoom display. There, they were paired D7000 and the HeadRoom Ultra Desktop with the Ultra Desktop Amp, which has amp are not cheap ($2600 total MSRP), HeadRoom’s premium amplifier modules, this complete system (just add disc player or and their premium DAC. I was able to set up computer) will absolutely KILL any normal hifi system I’ve heard costing less than $30,000. Sure, you give up the physical slam of bass, and the large soundstage, but the frequency response, tonal accuracy, speed and agility and even imaging and soundstaging (in their own way) are truly spectacular.

I’ve been looking to upgrade my office listening environment. I have a HeadRoom Total Bithead amp with Etymotic ER-4S headphones that I use mainly for travel on the airplane. At my desk, the isolation of the Etymotics is so good I can’t hear my

op amps available. We use these same op- card also is compatible with ASIO (Audio amps in a preamplifier circuit for milivolt Stream Input/Output) drivers. Typically, all level signals in the radio astronomy audio on Windows machines is processed instrumentation I build for my day job. They by kmixer, the underlying audio engine in cost over $20 a piece in small quantities. the Windows OS. While it is possible to get These op amps are in HeadRoom’s “Max” good performance with kmixer, it is almost amplifier modules, which drive both stereo impossible to tell what kmixer is doing. channels. In addition to the Max amplifier It may or may not perform all manner of modules, the Ultra Desktop also includes the sample rate and bit depth conversion on an Max DAC module, based on the AD1896 audio stream without your knowledge. ASIO a review of this same system, and have lived asynchronous sample rate converter and bypasses kmixer and sends the digital audio with it on my office desk for a few months. the Cirrus Logic CS4398 DAC. The SRC data directly to the audio device without To make a long story short, it is not going upsamples and pads all incoming digital any intervention. Use of ASIO requires a to leave. data to 24-bit 196 kHz. Toslink optical soundcard with an ASIO driver, which was and coaxial digital inputs accept signals at provided with the M-Audio Audiophile Design sample rates up to 24-bit, 192 kHz. The 2496. For some other common soundcards, USB input accepts only 16 bit inputs up to including the USB sound CODEC, a free The Denon AH-D7000 is the latest in 48 kHz. A super high quality ALPS volume ASIO driver called ASIO4ALL is available Denon’s new sealed headphone lineup, pot controls the level, with switchable rear on the web for free download (but only and is meant to be the flagship model. At panel RCA outputs available for use as a supports 16 bit word size and maximum 48 $1000 MSRP, it is a very expensive pair of preamp. Two pairs of RCA analog inputs kHz sample rate for USB). The audio player headphones. Your $1000 does get you a are also available. The power supply for the also needs to support ASIO output. The very impressive amount of craftsmanship. Ultra Desktop amp is external. Included “industry standard” player iTunes, does not The headphones are delivered in a very nice is the third-party Astrodyne switch-mode support ASIO output. I used another free presentation box with a calfskin leather power supply, which can supply up to 42 player, Foobar2000, configured with several front and silk lining (or at least they seem W of DC power, and autoswitches for 110- plugins to approximate iTunes functionality. like calfskin and silk; they may be synthetic). 220V and 50 or 60 Hz. As a $499 upgrade, While it is not as easy to use or as pleasant The sealed backs of the headphones are made HeadRoom offers their own bespoke, linear to the eye, it does offer ASIO output and of beautifully finished certified-sustainable power supply. My test unit included the offers the user complete control over audio rosewood, with Denon logos under the Astrodyne power supply. output. gloss lacquer. The adjustment mechanisms are made from machined magnesium for “... stupendously fast, agile and When used on a Macintosh computer light weight, and have been engineered tonally accurate.” running OS X, iTunes does not have to deal with the precision of a camera mechanism. with kmixer, and does output a file’s native The feel of simply adjusting the headband Setup (or an aside into computer bit depth and sample rate in a “bit perfect” screams “high end.” The Earpads and head audio) manner, as long as the digital interface can band are made from the same calfskin or handle the data. Unfortunately, I am forced calfskin like material used on the box cover. I deployed the HeadRoom/Denon pair to use a Windows box at work to be able to A Y-shaped headphone cord with fabric on my desk at work, fed by my computer run Windows specific software without the cladding is employed, and is made of 7N workstation, a AMD Athlon X2 based performance penalty of a virtual machine oxygen free copper wire with a ¼” stereo machine running Windows XP SP3. Little environment like Parallels of VMware. plug termination. 2” diameter microfiber did I know the effort I would need to go drivers are used, with frequency response through to supply a high quality digital feed With the M-Audio soundcard and from below 20 Hz to 45 kHz. to the Ultra Desktop. I would have preferred Foobar2000 configured to feed the Ultra to use the USB input and iTunes as the player, Desktop native bit depth and sample rate The HeadRoom Ultra Desktop amplifier is a but both these methods offered some serious data through the coaxial digital input, I was perfect match to these headphones. Any high limitations. The Ultra Desktop’s USB input able to get the performance I wanted and performance headphone requires proper can only accept a 16 bit 44.1 kHz input. As I was confident that the system was doing amplification. Just as you would not drive a do have some high resolution digital audio in what I expected. pair of $180,000 Focal Grand Utopias with FLAC and Apple Lossless format, I wanted a $500 receiver, you wouldn’t want to drive to be able to feed the Ultra Desktop with a 24 a pair of D7000s with an iPod. The large bit 96 kHz signal. Most low cost soundcards driver requires power and control to achieve do horrifying things to the digital signal, maximum performance. While the flat 25 not limited to internal processing at 16 bit Ohm performance may seem an easy load 48 kHz regardless of the input signal or to drive, you will not get your $1000 worth desired output signal. I installed a M-Audio without a proper amplifier. The 6”x6”x3” Audiophile 2496 soundcard in the PC. This unit contains a stereo headphone power is one of the least expensive soundcards that amplifier based on the Burr Brown OPA627 offer a fully controllable 24 bit 96 kHz digital Op amp, one of the highest performance output. It is available for less than $100. This

I recently ripped all my CDs and DVD- Sound Audio discs to Apple Lossless format and/or FLAC (Free Lossless Audio Codec). Both are If there is one phrase to describe the sound capable of encoding high-resolution audio quality of the Denon/HeadRoom combo, (up to 24 bit 192 kHz) in a lossless manner, it is “jaw-dropping.” One of the main i.e. the decoded data is bit identical to the drawbacks of headphone-based audio is source data from the disc. Lossy formats a lack of low bass. Most headphones are like MP3 and Ogg do not encode the data simply not capable of producing large such that the decoded data is identical to amounts of low bass due to the small size the source therefore information is lost. The of their drivers and the small volume of air Apple Lossless decoder in Foobar2000 does moving. Any serious bass below 40 Hz is not decode high-resolution files, only 16 bit hard to achieve, and any sense of power and 44.1 kHz. I therefore converted all my high- weight in the bass region as a whole normally Headphone soundstaging is somewhat res files to FLAC. At home, I use a Mac for comes with excessive bloat and boom. Most different than normal loudspeaker audio so I retained the ALC files for that use. good headphones end up sounding light in soundstaging. Typically the soundfield seems iTunes currently does not support FLAC. the bass, although still quick and agile. The to be inside and around the head. For me, the AH-D7000s, with proper amplification, turn center of the soundstage is between my ears, All this is proof that computer audio is not this paradigm on its head. I knew the bass inside the head. As sounds move “farther as transparent as it should be for audiophiles. was good, so one of the first tracks I listened back” in the soundstage, they seem to sound This stuff should Just Work, even across to was Daft Punk’s “Human After All.” At to come from above my head. Similarly, the platforms. It does not. It takes a bit of moderately high volume level, I though the left and right of the soundstage seem to be investment in time to learn the details to bass was going to implode my skull. Not inside my head near the left and right ears, get your computer working as a high quality that there was more bass than there should and extend out beyond my head to the left digital transport for your situation. When be, by the way. This particular track has a and right. This results in a soundstage plane this is done, however, the results can be very huge amount of very powerful low bass. The that is vertical, not horizontal. With the good. At home I feed my main system with an subterranean frequency extension and sheer AH-D7000, the soundstage ranged from Apple Airport Express wirelessly connected power delivered by the AH-D7000s put my inside my head to 1 to 1.5 feet outside my to my Mac. It feeds a Bel Canto DAC-1.1 home system to shame, 500W monoblocks, head. This is the largest perceived soundstage with a Toslink connection. The Bel Canto subwoofer amplifier and dual voice coil I have heard with headphones. This was does a good job of rejecting jitter from the woofers and all. Any loudspeaker that could facilitated by the HeadRoom amplifier’s Airport, resulting in sound that is actually deliver bass like this would cost many tens crossfeed circuit, which mixes some of the superior to my Oppo DV-983H when used of thousands of dollars. The bass was also right channel into the left (and vice versa), as a CD transport for 16 bit 44.1 kHz files. stupendously fast, agile and tonally accurate. through a time delay and amplitude filter. The Airport Express does not support high Since there are no room effects between the This simulates the effect of sound waves from resolution digital files (Grrr!). driver and your ear, none of the normal the left and right stereo channels in free space acoustic effects that plague loudspeakers in a (i.e. from a loudspeaker), which eventually For break-in, I played my playlist from the normal listening room are present. Over the get to both ears but at different times and beginning at moderate volume over a weekend course of a couple of months as the drivers at different volumes. The crossfeed can be while I was not in the office. These 48 hours broke in, the bass became even more tonally defeated, but this results in the soundstage or so of constant music did a reasonable job accurate and tight than when I first listened collapsing to three “blobs” of sound, left at breaking in the drivers. The HeadRoom to them. center and right. amplifier was an already used show demo unit, so it required no burn in. “... world beating performance ...” When compared to my pair of Sennheiser HD-595s, the Denons were superior in Links for computer audio software and Midrange and treble tonal accuracy and every way. The soundstage was larger and information: presentation of timbre were also first rate, more airy, transient response and speed were a trick for a sealed headphone. Most high superior, treble extension and smoothness * Foobar 2000 audio player for windows performance headphones are open baffle were better. Midrange smoothness and tonal 2000/XP/Vista designs. Sealed loading of the driver usually accuracy was also greatly improved with the http://www.foobar2000.org/ results in a closed in and tonally muffled Denons. The bass was no contest, although * ASIO4ALL free ASIO driver for USB audio midrange, but the Denons have been carefully there is no headphone I have ever heard and many common soundcards engineered to avoid this fate. Tonal accuracy that can compete with the Denon’s bass, http://www.asio4all.com/ is at least as good or better as the Sennheiser period. The sealed design of the Denons was * Make Foobar2000 Look Like iTunes offerings I have had the pleasure to listen also preferred to the Sennheisers when any http://www.teqnilogik.com/tutorials/ to (HD 580, HD 595 and HD 600). High background noise was present. Compared to foobar2000_itunes.shtml frequency smoothness and extension were my pair of Etymotic ER-4S, the Denons were * FLAC: The Free Lossless Audio Codec also essentially perfect. Transient response and also superior in every way. The Etymotics http://flac.sourceforge.net/ speed matched or exceeded any headphones I have a bass shy balance anyway, and since * Apple Lossless Codec have ever heard. they are in the ear headphones there is no http://en.wikipedia.org/wiki/Apple_Lossless air movement around the ear to reinforce the

© Copyright 2009 Secrets of Home Theater and High Fidelity www.hometheaterhifi.com Denon AH-D7000 Headphones and Headroom Ultra Desktop Headphone Amplifier - Page weight of the bass. The Etymotics do offer the whole body of the listener. Also, note vastly superior sound isolation (23 dB vs 8 the y-axis scale. Most loudspeakers, when dB for the D7000s), allowing for fantastic measured in-room, have response variations detail retrieval in the face of background of over 10 dB from flat due to room effects. noise. Of course, you won’t be able to hear Good headphones rarely deviate by more your phone ring either. than a few dB from flat since there are no room effects for them. I also used my battery powered HeadRoom Total Bithead to power the AH-D7000s. This These measurements, plus measurements portable amp is also a headphone amp with a for all headphones HeadRoom sells, can be built in DAC. The DAC is USB input only, found on their “Build a Graph” page: and does not offer sample rate conversion or as high a quality DAC. The headroom http://www.headphone.com/technical/ amplifier module is of a similar design and product-measurements/build-a-graph/ Isolation begins to kick in at about 800 Hz, uses upgraded parts as compared to the and is an impressive 15 dB or so from about 1 standard module. It does not use the super kHz up. Low frequency isolation is basically high quality OPA627 op amps, and is powered non-existant. Only in the ear headphones by 3 AAA batteries rather than a beefy power like the Etymotic ER-4S can provide good supply. Every area of performance, while low frequency isolation. Compared to open still listenable and WAY better than an iPod, back headphones, the Denons have isolation was significantly degraded. The AH-D7000s from 800 Hz up, as compared to 5 kHz and want a lot of power to deliver their bass up as with my Sennheiser HD-595s. punch, and midrange and treble agility and speed. The total bithead made an effort, but Conclusions could not keep up. The DAC was also a bit grainy and dynamically flat by comparison. Listening to headphones is a different While a full-up Ultra Desktop is not strictly Frequency response of the AH-D7000s experience that listening to loudspeakers, for speaking necessary to enjoy the AH-D7000s, extends all the way to below 20 Hz. The -3 sure. If you are looking for the best possible the headphones will benefit from every bit of dB point is about 17 Hz. There is a broad sound quality (i.e. frequency response, clarity, improvement you can provide in the source response bump in the bass peaking at about tonal accuracy, retrieval of detail, imaging, and amplification electronics. +5 dB at 40 Hz, typical, although lower in soundstaging, etc), at the lowest possible cost, frequency compared to most headphones. headphones are unbeatable. The Denon AH- Measurements High frequency response is rather flat until D7000s, when powered by the HeadRoom a suckout comes in at about 15 kHz. This Ultra Desktop amplifier and DAC, offer The data provided below were measured suckout is likely due to cancellation in the world beating performance at something by HeadRoom using an artificial head folds of the simulated ear on the HeadRoom like 1/10 or 1/20 the price of admission for microphone system. This model head has measurement system, as discussed before. It an equivalent loudspeaker based system. I microphones imbedded in replica human is paradoxically different in the left and right covet the AH-D7000s and the HeadRoom ears, so it listens just as we do. This does channels, which could have been caused Ultra Desktop amp. They make working at make for frequency response plots that are by the drivers sitting on the artifical head my desk a much more pleasant and relaxing different than we’re used to looking at for differently on the left and right. experience. I will not be letting them leave. loudspeakers. The folds and ridges of the ear cause the high frequency response of a Specifications: microphone imbedded in a model ear canal to have various peaks and dips caused by in and Denon AH-D7000 Headphones out of phase interference of sound travelling • Design: Over-the-Ears Headset; Sealed Enclosure • Driver: Dynamic around the ear. The human brain equalizes • Isolation: -8 dB this response. We never see these peaks and • Impedance @ 1 kHz: 25 Ohms dips with loudspeaker measurements because • Connector Type: 1/4” they are measured with bare microphones. All • Cord Length: 9.5 Feet • MSRP: $999 USA headphones will show these high frequency peaks and dips. At lower frequencies, where HeadRoom Ultra Desktop Headphone Amplifier the wavelength of sound is significantly • MFR: 10 Hz - 50 kHz ± 3 dB longer than the size of the ear, there is no Distortion of a 500 Hz sine wave is • THD+N: 0.002% at 1 Volt Output • Input Impedance: 70 kPhms effect. spectacularly low, with the highest harmonic • Dimensions: 3.3” H x 6” W x 6” D product just over – 80 dB. This would be • Weight: 1.8 Pounds Most headphone manufacturers aim for good for a preamp, much less a loudspeaker! • MSRP: $1599 USA with Astrodyne Switching a couple of dB more bass than flat to add Power Supply a bit of bass weight and impact that is lost due to the fact that sound waves do not hit