Category Archives: Audio

Ubuntu VLC DAC Audio

I recently got a JDS Labs Element DAC + headphone amp. I drive it from my Ubuntu desktop using VLC as the audio player. It’s plug and play – no drivers needed. However, best results come after applying a few tips:

VLC Audio Device: The DAC has 17 output devices that appear in VLC. Which one to use? Use Pulse Audio if you want to hear a mix of all audio on the computer. Pulse Audio mixes all sources and resamples them if necessary to a common rate. Use JDS Labs Element DAC, USB audio direct hardware device without any conversions if you want to hear the audio track in its native sampling rate & bit depth, and nothing else. I prefer this for best sound quality.

VLC Output Module: use Pulseaudio audio output if you want to hear a mix of all audio on the computer. Use ALSA audio output if you want to bypass Pulseaudio to hear the audio track and nothing else.

VLC occasionally stopped playing and popped up an error saying “Device or resource busy”. If you’re using ALSA, only one app at a time can use the device. For example, if the browser tries to play a video it can steal the device from VLC. Also, VLC seems to have a bug in which it occasionally steals the device from itself when switching tracks. Adding a udev rule made this happen far less often. Add a file called 41-jdslabs-dac.rules to directory /etc/udev/rules.d. Make the contents like this:

# JDS Labs Element DAC
SUBSYSTEM=="usb", ATTR{idVendor}=="262a", MODE="0666", GROUP="plugdev"

This makes the JDS Labs DAC accessible to any Linux user.

Audio Glitches: Occasionally, once every hour or so, the audio will stop for a moment, then resume. I believe this is because the JDS Element uses USB adaptive mode, not async. This makes it compatible with more computers. Some people claim that adaptive move has more jitter and lower sound quality, but measurements belie this claim.

More audio glitches: Occasionally I would hear tics in the music, as if the computer CPU were too busy to deliver audio. Re-nicing the VLC process to -15 fixes this.

Review: Audeze LCD-2 (2016)

What? Another LCD-2 Review? Why? Here’s the background.

I got a second pair to use at work, again from the Headphone folks in Montana. I’ve owned this headphone since 2014 and already reviewed it twice: once when I first got them, again later when I EQed them. Audeze never rests and is constantly improving their products. But they don’t change the model numbers. The LCD-2 has gone through several variants with names the community invented because Audeze didn’t see fit to name them:

  • LCD-2.1: the original version – creamy sound, smooth linear mids with rolled off treble
  • LCD-2.2: same linear mids, improved treble response, yet still on the warm side of neutral
  • LCD-2F 2014: introduction of Fazor, improved detail and transient response, but some people report the treble sounds wonky
  • LCD-2F 2016: lighter re-tuned drivers, further improved transient response

The 2016 LCD-2 is similar to the 2014 overall, with excellent reference quality sound. Since I linked the prior reviews above, here I’ll describe only the differences. Compared to the 2014, the 2016 LCD-2 has:

  • Bass: cleaner, tighter, faster but neither attenuated nor amplified. This is hard to imagine because the 2014 bass was excellent to begin with. Somehow they improved it.
  • High Treble (9+ kHz): cleaner, faster and slightly amplified. A good recording of castanets shows the 2014 was already excellent, but the 2016 is even better. Treble is shelved up a touch and brighter compared to the 2014, but the 2016 is not bright sounding.
  • Mids: different – described below

Comparing the midrange is more complex and takes more than a few words. The 2014 midrange is incredibly smooth and natural and has a slight presence emphasis compared to the 2016. This presence is subtle and to put it in perspective, the Sennheiser HD-600 (a great headphone in its own right) has far more presence sounding boxy or nasal in comparison. I like the 2014 mid presence on small ensemble acoustic music; it brings out the natural timbres of acoustic instruments and voices. But with large ensemble works and big complex music, this presence becomes a slight glare that veils the music. The 2016 lacks this presence, yet it also lacks the glare that comes with it on big complex music. The 2016 still voices acoustic instruments in a natural, realistic way – it’s not midrange suck-out like some headphones have.

So when it comes to the midrange, both do extremely well, yet I prefer the 2014 for small ensemble acoustic music and the 2016 for bigger more complex music.

Overall, the 2016 is better than the 2014 in many ways, but not in every way. The 2016 is more open, faster and more resolving – all good. Yet the 2014 has a special intimacy and realism to the midrange voicing of small ensemble acoustic music.

Note: I contacted Audeze and for $400 they will upgrade any model of LCD-2 to the latest version, which includes new ear pads of your choice and return shipping. I’m leaning toward upgrading my 2014… but haven’t yet decided. If the 2016 was better in every way, I would. But the decision isn’t that easy.

Alternatives

In my experience, planar magnetics wipe the floor with conventional drivers in terms of overall sound quality – both in headphones and in speakers – so I limited my search to them.

I auditioned the HiFi Man HE-500 a few years ago. It was a great headphone but had a weird midrange response that didn’t voice acoustic instruments properly. I looked at other HiFi Man models but none of them have the truly linear frequency response I’m looking for.

I gave the Focal Elear serious thought. Sure, it’s a conventional driver. But it had such rave reviews I considered it. Yet it also had some decidedly non-rave reviews and the specifications showed non-linear frequency response, transient ringing and higher distortion. No thanks.

Finally I decided to keep it simple. I like my LCD-2 so much, why not first try the latest version? If I didn’t like it I could always return it and move on to something else. I found a pair from Headroom, the headphone folks in Montana, that was an open box, so I got a lower price, yet new with full warranty. I’ve been a customer of theirs since 1999 because they are knowledgeable, honest and have a generous 30-day try-return policy.

Review: JDS Labs Element

The Element

See here for background.

It’s a headphone DAC+amp – details here. Since I care about function over form, I saved $50 buying a b-stock version new from JDS. It’s small & light, simple to use and beautiful in appearance. The cosmetic glitches that made it b-stock are truly cosmetic and so slight you won’t even notice unless you’re a perfectionist. Inputs are USB and analog unbalanced RCA, so it can be DAC+Amp or just an amp.

The Element comes with an external wall-wart type power supply and a USB cable. The power supply is unusual: a wall-wart style AC-AC whose output is 16 VAC at 1 Amp. That’s 16 Watts for a 1 watt amp – so far so good!

My description of the sound is brief because there’s not much to describe. If you’ve ever heard a well designed and built top quality solid state amp, that’s what the Element sounds like. Spec-wise (curious readers will find specs at the above link) it’s as good or better as anything you will find at any price. And I mean any price – even into the multi-kilobuck range. I believe specs are useful but they don’t tell the full final story. Absolutely black quiet background: no audible noise at any gain or volume setting. Stark neutral frequency response, all measured distortion (THD, IMD, noise, etc.) at -100 dB or lower. The sound is smooth yet detailed with no edge or grain. It sounds exactly like whatever you’re playing. Some people call its high frequencies “dry” and I would agree if by “dry” they mean detailed yet smooth and neither boosted nor attenuated. What’s the opposite of dry – moist? Would anyone describe the high frequency reproduction of an amp as “moist”? The closest thing I can imagine to “moist” is the tubuliciuos sound of a top quality SET amp. That is a nice lush sound for people who like that sort of thing – I appreciate it but it’s not what floats my boat. And it’s not what you’ll hear from the Element. But another thing you won’t hear from the Element is grain, glare, edge or any other kind of distortion, unless it’s in the source recording. I particularly notice how well the Element handles big dynamics. For all practical purposes and somewhat beyond, the Element is sonically indistinguishable from my HA-1 and Corda Jazz. With hours of dedicated A/B testing I might be able to tell some kind of slight difference, but I can’t confidently say I could and even if I did it would be splitting hairs.

The volume knob is big, sits top center, moves easily and smoothly and has a wide range – over 270* of rotation. It’s nicely linear and extremely well balanced L-R.

The USB DAC can accept up to 96 KHz – 24 bit. When listening to this digital source the amp has considerably less gain. My LCD-2 headphones needed high gain setting. When listening to the analog unbalanced RCA inputs – bypassing the DAC and using it as a simple headphone amp – it has a lot more gain and I used the low gain setting.

I have one minor quibble with the Element – the build quality is good, but not quite excellent. The connectors aren’t the rock solid Neutrik et.al. you get on true audiophile amps, and doesn’t give the satisfying thunk those provide when you connect & disconnect. It has me plugging in the headphones & other connectors with care. The volume knob is very smooth and satisfying to use (and it’s a top quality Alps pot), but it has a bit of give when you push gently on it and the instructions say not to lift the amp by the volume knob – despite the amp being small & light. Overall, the Element is well built yet not the solid brick military build quality of top-tier professional and audiophile equipment. I suppose JDS had to find cost savings somewhere, and they seem to have made the right choices. It does have a solid warranty you can use if something breaks or flakes out on you.

Overall, two thumbs-up for the JDS Labs Element. It is a complete DAC+amp, semi-portable by turning any computer into an audio source, with enough clean power to drive just about any headphone on the planet. It’s incredible the level of engineering, sound quality, and output power you get for the price.

Background: JDS Labs Element & Audeze LCD-2 2016

Background

I spend a lot of time at work and wanted a reference quality headphone rig to match my home system. Technology is constantly improving, reducing the price of reference quality audio every year. I still love my LCD-2 headphones, so they were at the top of my list yet I was open to trying any new headphones released since then. I wasn’t going to get another Oppo HA-1, which I used in my home system. It’s too bulky and has way more features than I need, and at work I use the computer as an audio source. I have a great computer audio system at home too, using a Juli@ sound card and Corda Jazz amp. I’d consider getting another just like it, but first wanted to check out what alternatives might have recently appeared.

If you’re using a computer as the audio source, you need two things:

  • A high quality D-A converter to get a line level analog signal.
  • A high quality headphone amp to amplify that signal and drive headphones.

A sound card does the first – but it’s not portable and only works with desktops (not laptops). Now, all computers can stream audio files out a USB port to an external DAC. This is portable and works with any computer – desktop or laptop. With the right configuration (adaptive or async), the external DAC clocks the bits and jitter is not an issue.

Given my preference for no-nonsense engineering over audiophile mystique, I quickly found JDS Labs, aka some guys in Illinois building well-engineered and built headphone audio gear on a budget. They started by producing a little amp called the O2, an open source design released into the wild by NwAvGuy. Prior to JDS, this was only available as a kit, and lots of headphone audiophiles don’t have the skills to build it. Perhaps they should – no Jedi’s training is complete until he builds his own light sabre – but that’s a different subject.

A few years ago, JDS started building their own designs, which took the O2 to another level in performance and higher power output enabling them to be used with a wider variety of inefficient power hungry headphones like the HiFi Man HE-6. Yet even JDS’s new gear was built to solid engineering specifications without any audiophile nonsense and reasonably priced.

Long story short, I got a second pair of LCD-2 headphones and a JDS Element to drive them, which is a headphone amp combined with a USB DAC. I compared this amp to my HA-1 and Corda Jazz, which is stiff competition.

I posted my reviews of the Element and 2016 LCD-2 separately.

HRTF

HRTF is Head Related Transfer Function. It describes how you perceive sound. Every person perceives sound differently because the individual shape of your head, ears, nasal & mouth cavity, etc. all affect how the sound reaches your ears. In short: different people listening to the same thing, hear it differently.

What most HRTFs have in common is the range from 2 – 5 kHz is amplified by 15 dB or more. The ear’s resonance is typically +17 dB at 2.7 kHz. That is a huge non-linearity. Here is a typical HRTF curve from Tyll Herstens at Inner Fidelity.

Another way to think about this: Suppose you’re standing at the seashore listening to waves crashing on the beach. That sound is similar to white noise: it has roughly equal energy across a wide frequency range. The sound you actually perceive, however, is 10 – 20 dB louder in the 2 -5 kHz range because those frequencies were amplified (or frequencies outside that range attenuated) by your head, ears, ear canals before it hit your eardrums.

You can easily test how the size & shape of your head & ears affects sound. While listening to music on speakers, gently push your ears forward or open your mouth really wide. The sound changes. And that only gives a small taste of what the real differences are – imagine how much more different it might be if you could change the size & shape of your head, ears, etc.! That different sound you hear would be what another person hears normally.

The astute reader will wonder – if this variation is due to individual variance in body size & shape, how can it be measured? The answer is simple. Take 2 tiny microphones small enough to fit inside your ear canal. Position them in the open air and use them to record sound. Now build a fake life-size human head using materials that approximate the density & reflectivity of human tissue and skin, and insert these same mics deep into the ear canals, facing outward. Now measure the same sound again. The difference between the two recordings is the HRTF of your dummy head.

Every person has an individual HRTF and the variance from person to person is significant. Since headphones bypass the HRTF, in order to sound natural they must have a frequency response that matches the HRTF. Put differently, a headphone with flat frequency response would sound quite dull, down 15+ db in the 2 – 5 kHz range.

This doesn’t apply to loudspeakers. If a speaker has objectively flat FR, every person will perceive that however they perceive natural sounds. Speakers don’t have to reproduce the HRTF because the sound comes from a distant source and your HRTF transforms it when it hits your body. Headphones play sounds directly into your ears, bypassing your body, head and HRTF.

This means there is an absolute reference FR for speakers: perfectly flat. But there is no absolute reference FR for headphones. A headphone has to mimic the HRTF which is different for every person. The best a well-engineered headphone can do is mimic the most common or average HRTF across the population. Each individual will be a little different.

Thus, different people will disagree on what headphone has the most natural FR reproducing sounds most realistically. For example, the Sennheiser HD-800 has a big response rise around 5 – 7 kHz. For me personally, it’s artificially bright, almost skull-jarring. But for others it may sound natural. At the opposite end of the spectrum, the Audeze LCD-2 has a dip from 2 – 9 kHz (its raw response has a rise, but it rises a bit less than the typical HRTF does). For me personally, it sounds natural and realistic. My HRTF probably lifts this frequency range less than average. But for others this headphone sounds dull.

Good IEMs (In-Ear Monitors) aka Earbuds

Most phones have very good audio output quality via their analog headphone jack <note to self: resist urge to crack iPhone 7 joke…> if you can find earbuds that sound good. Yet that’s a big if. Most earbuds sound like crap. Of the few that sound good, some have impedance or efficiency that don’t match well to a phone. Also, while phone audio output is often very good, that does not mean excellent or reference quality, so don’t go overboard and waste money on really expensive IEMs.

I listen to mostly natural acoustic music and I’m picky about sound. The best really good IEM I’ve found is the Vsonic GR07. They cost about $100 and sound really good. To my ears, they’re comparable to a pair of full-size HD-600. They have flat, neutral response that is neither warm nor bright, but just right. The treble is smooth with good detail. Due to a phone’s audio output limitations, even with uncompressed FLAC files the extreme high frequencies are rolled off and there’s less “air”, slightly less crisp transient response.  It sounds very good, even great, but not excellent or reference quality. The GR07 is about the best quality it’s worth paying for given the limitations of the source.

The best cheap IEM I’ve found is the Vsonic VSD1S. They cost about $35, have the same high quality construction and 90% as good sound as the GR07. Comparatively, the VSD1S has a slight midrange recess, not quite as smooth or extended treble. Overall, they still have a nice neutral sound despite have a touch more “V” shaped response curve. They’re good enough to listen to for hours enjoyably without fatigue, better than most other good IEMs, but just not quite as refined as the GR-07.

A Cheap Audiophile Headphone System

Here’s a cheap audiophile quality sound system:

That’s it. Connect the Juli@ unbalanced analog outputs to the amp’s inputs. Play your CDs, DVDs, whatever on the computer. Use whatever headphones you want.

Total cost: $510 = $170 for the card, $340 for the amp. Plus the headphones. You can get some vintage Sennheiser HD-580 or HD-600 on eBay for a couple hundred bucks. Or you can go all-in with a really nice set of headphones like the Audeze LCD. The Corda Jazz has a smooth sound, detailed and sweet yet neutral, with enough power to  drive almost any headphone on the planet.

I use this as a secondary system to drive my Audeze LCD-2F when my reference system is unavailable. It is amazing – 95% as good as the reference system. Extreme treble and large ensemble complex music is not quite as refined, but that’s just picking nits because it sounds damn good.

Years ago when I was in college I would have climbed a mountain of broken glass for sound like this, especially at this price.

Note: you can get an audio system like this even cheaper from JDS Labs. Get a single DAC+Amp for $300, so you don’t need the sound card. Just stream the bits from the USB port of any computer into the DAC. JDS Labs is the American version of Jan Meier’s Corda in Germany: a few guys in Illinois who are good electrical engineers and take a non-nonsense approach to building audiophile quality gear without audiophile prices or bullshit.

The Fantastic Audeze LCD-X

A few years ago I found the best headphones I’ve ever heard, the Audeze LCD-2. These are the 2014 Fazor version. A while later I made them even better with a subtle parametric EQ. That may sound like sacrilege to some audiophiles, but it works for me. The LCD-2 has  enhanced my late-night music listening and I still enjoy and use them regularly.

Since then, Audeze came out with another headphone: the LCD-X. It is designed to have a more neutral (flatter) frequency response and faster/cleaner transient response. Both of these claims are substantiated by measurements. But how do they sound? I wanted to find out. Audeze had a sale so I ordered a pair to get a listen.

Dimensionally, the X are exactly the same as my 2, or so close I couldn’t tell the difference. They’re black and made of metal, where the 2 are wood. The X are a bit heavier, but I didn’t feel the difference. Clamping force, fit, they felt exactly the same on my head.

I ran the comparison through my Behringer DEQ2496. More precisely, CDs played on my Oppo BDP-83, toslink to DEQ2496, toslink to Oppo HA-1, balanced headphone out. The DEQ2496 enabled me to level match within 0.5 dB, keeping the signal otherwise unchanged, or apply EQ as mentioned below. This doesn’t use the DEQ2496’s DA or AD converters; it operates in pure digital mode. Subjectively, I found the X to be 8.5 dB louder than the 2, so used this to equalize the levels.

Tech note: According to specs the X is about 11 dB louder than the 2 at the same volume setting. According to Audeze specs, the X makes 103 dB with 1 mW of power and has a 20 ohm impedance. Since it’s planar magnetic, the impedance is flat vs. frequency. That means 0.1414 V (141 mV) will make 103 dB, so 0.0317 V (32 mV) will make 90 dB. The voltage sensitivity of the LCD-2 is 0.114 V @ 1 kHz @ 90 dB. So we have 20*log(0.141/0.032) = 12.9 dB. My subjective impression was slightly different. Attenuated by 13 dB, the X was quieter than the 2; I used 8.5 dB.

First I did the fair comparison: head to head, no EQ. Here it was no contest: the X was easy to differentiate, and overall better sound:

  • X has more upper mid – no dip like the 2
  • X bass is slightly (about 2dB) quieter, but just as flat and deep
  • X has slightly better bass clarity
  • X has more linear and extended treble
  • X sounds “cool”, not “warm” like the LCD-2
  • Detail: X is on stage with the musicians, 2 is in the 5th row back
  • The X has more detail than reality; the 2 has less than reality; neither is perfect but the X is closer

However, I don’t listen to my 2s straight. I apply a parametric EQ: +3 dB @ 4600 Hz, Q=0.67 (3 dB / octave, 2 octaves wide). This counteracts the 2’s softness in the upper mids and lower treble, giving it a more neutral response curve and a bit more detail as if you’re sitting a few rows closer to the stage.

So next I did the realistic comparison: how I would actually listen to them: X raw, versus 2 with the above EQ:

  • They sound almost the same
  • X emphasizes the overtones, but still has the core sound
  • 2 favors the core sound, but still has the overtones
  • X is slightly more clear, yet less realistic voicing on some recordings
  • 2 has more realistic voicing on most recordings, yet slightly less clear
  • 2 is on the warm side of reality, X is on the cool side
  • Overall, which sounds better depends on the recording

Here it was a much harder decision. I also compared them to my speakers. They were about equally close to that sound, yet approaching it from opposite sides. These are both excellent headphones and I could be happy with either. They wipe the floor with any conventional dynamic headphone I have ever heard. If I didn’t already own the 2, or if I didn’t have a digital parametric EQ, I would pick the X. But I do already own the 2, and with the parametric EQ they are just as good as the X. I listen mostly to acoustic music and the 2’s realistic voicing is more important to me than the X’s extra 1% of detail. So why change anything?

I kept my LCD-2F and returned the LCD-X thanks to Audeze’s excellent service which includes a 30 day trial period. It was a fun experiment and satisfied my curiosity. While I kept my LCD-2F, I can heartily recommend the LCD-X to anyone who wants a fantastic set of headphones with dynamic and detailed yet realistic sound.

The Amazing Audeze LCD-2 (rev 2 Fazor)

A couple years ago I bought a pair of Audeze LCD-2 headphones. I’ve listened to many headphones over the years and they are the best headphones I’ve ever heard. This is what I had to say about them.

But, like all things created by mankind, they’re not perfect. Their near-perfect frequency response has a small dip between 2 kHz and 9 kHz. It’s linear and smooth, so subjectively is barely noticeable. Yet it slightly subdues the sound, as if you’re sitting a few rows back from the 1st row.

Since I recently got a digital signal processor, I figured I’d try it out on the headphones. I put a single parametric EQ, +3 dB, centered at 4,600 Hz, 2 octaves wide (slope 3 dB / octave, or Q=0.67), so it has effect between 2,300 and 9,200 Hz. To my ears, this made the LCD-2 absolutely perfect. It’s subtle yet definitely noticeable (I blind tested it on a variety of recordings), and shifts you back to the 1st row of the audience.

I tried +4 dB and it was good, though a bit more than needed. +2 was not quite enough; +3 was perfect. And I tried shifting the frequency up and down a bit, but 4,600 Hz sounded perfect.

From what I can see in specs, this makes the LCD-2 sound closer to the LCD-X, taking it from slightly warm or rounded, to neutral. The LCD-2 still sounds yummy, yet realistic – yet now it’s a touch more detailed. This EQ doesn’t change the character of the sound, it just makes that dip shallower giving a bit more upper midrange and treble detail. It’s about as close to perfect sound as human engineering can achieve in a headphone.

I’ve considered getting the LCD-X but this change nixed that entirely, making the LCD-2F near enough perfection to keep for a long time.

The Power of the Dark Side

First let’s cut to the chase: in-room far-field frequency response measured at the listening position using 1/3 octave warble tones, measured with a Rode NT1-A mic, corrected for mic response

InRoomFreqResp

  • The red line is what you hear – near perfection!
  • The solid blue line is with room treatments, but without EQ
  • The dotted blue line is without room treatment

In short, you can see that room treatment (huge tube traps and copious use of thick RPG acoustic foam) made a huge difference. Then EQ finessed that to something near perfection.

Now, for the details:

I’ve been an audiophile since my late teen years, long before my income could support the habit. As an engineer and amateur musician I always approached this hobby from a unique perspective. The musician knows what the absolute reference really sounds like – live musicians playing acoustic instruments in the room. The engineer believes objectivity – measurements, blind listening tests, etc. – is the best way to get as close as possible to that sound.

Part of this perspective is being a purist, and one aspect of being a purist is hating equalizers. In most cases, EQ falls into one of 2 categories:

  1. There are flaws in the sound caused by the speakers or room interactions, and instead of fixing them you use EQ as a band-aid. This flattens the response but leaves you with distortions in the phase or time domain, like ringing.
  2. You don’t want to hear what live acoustic music really sounds like, you prefer a euphonically distorted sound and use an EQ to get it.

Equalizers are the dark side of audio. Powerful and seductive, yet in the end they take you away from your goal: experiencing music as close as possible to the real thing. Recently I traveled to the dark side and found it’s not such a bad place. Share my journey, if you dare.

I had my audio room here in Seattle dialed in nicely after building big tube traps, thick acoustic foam and careful room arrangement based on repeated measurements. However, it still had two minor issues:

  1. A slight edge to the midrange. From personal experience I describe it as the sound I hear rehearsing on stage with the musicians, rather than being in the 2nd row of the audience.
  2. The deepest bass was a bit thin, with 30 Hz about -6 dB. I have a harp recording where Heidi Krutzen plays the longest strings, which have a fundamental around 25 Hz. I could hear this in my room, but it was a subtle whisper. It would be nice to hear that closer to a natural level.

My room treatments made a huge improvement in sound (and I have the measurements to prove it). But I don’t know of any room treatment that can fix either of these issues. The sound was very good both objectively (+/- 4 dB from 35 Hz to 20 kHz at listener position) and subjectively, and I enjoyed it for years. Then I got the LCD-2 headphones and Oppo HA-1 DAC. As I listened to my music collection over the next year (a couple thousand discs, takes a while), I discovered a subtle new dimension of natural realism in the music and wanted to experience that in the room.

Since my upstream system was entirely digital, equalization might not be as terrible as any right-thinking purist audiophile would fear. I could equalize entirely in the digital domain, no DA or AD conversion, before the signal reaches the DAC. And since the anomalies I wanted to correct were small, I could use parametric EQ with gradual slope, virtually eliminating any audible side effects.

That was the idea … now I had to come up with an action plan.

After a bit of Googling I found a candidate device: the Behringer DEQ2496. Price was the same on B&H, Adorama and Amazon, and all have a 30 day trial, so I bought one. The DEQ2496 does a lot of things and is complex to use and easy to accidentally “break”. For example, when I first ran the RTA function, it didn’t work. First, the pink noise it generates never played on my speakers. After I fixed that, the microphone I plugged in didn’t work. After I fixed that, the GEQ (graphic equalizer) settings it made were all maxed out (+ / – 15 dB). Finally I fixed that and it worked. All of these problems were caused by config settings in other menu areas. There are many config settings and they affect the various functions in ways that make sense once you understand it, but are not obvious.

NOTE: one easy way around this is before using any function for the first time, restore the system default settings, saved as the first preset. This won’t fix all of the config settings; you’ll still have to tweak them to get functions to work. But it will reduce the amount of settings you’ll have to chase down.

In RTA (room tune acoustic?) mode, the DEQ2496 is fully automatic. It generates a pink noise signal, listens to it on a microphone you set up in the room, analyzes the response and creates an EQ curve to make the measured response “flat”. You can then save this GEQ curve in memory. You have two options for flat: Truly flat measured in absolute terms, or the 1 dB / octave reduction from bass to treble that Toole & Olive recommend (-9 dB overall across the  band). This feature is really cool but has 2 key limitations:

  1. It has no built-in way to compensate for mic response. You can do this manually by entering the mic’s response curve as your custom target response curve, but that is tedious.
  2. It provides only 15 V phantom power to your mic. Most studio condenser mics (including my Rode NT1-A) want 48 V, but aren’t that sensitive to how much voltage they get and work OK with only 15 V. But you always wonder how much of the mic’s frequency response and sensitivity you lose when you give it only 15 V. Perhaps not much, but who knows?

The GEQ settings the DEQ2496 auto-generated were too sharp for my taste, so I looked at the FR curve it measured from the pink noise signal. This roughly matched the FR curve I created by recording 1/3 octave warble tones from Stereophile Test Disc #2. Since both gave similar measurements, I prefer doing it manually because I can correct for the mic’s response, and my digital recorder (Zoom H4) gives the mic full 48 V phantom power.

So the curves match: that’s a nice sanity check – now we’re rolling.

Using the DEQ 2496, I created parametric EQ settings to offset the peaks and dips. This enabled me to use gentle corrections – both in magnitude and in slope. I then replayed the Stereophile warble tones and re-measured the room’s FR curve. The first pass was 2 filters that got me 90% of the way there:

  • +4 dB @ 31 Hz, 1.5 octaves wide (slope 5.3 dB / octave)
  • -3 dB @ 1000 Hz, 2 octaves wide (slope 3 dB / octave)

These changes affected other areas of the sound, so I ran a couple more iterations to fine tune things. During this process I resisted the urge to hit perfection. Doing so would require many more filters, each steeper than I would like. It’s a simple engineering tradeoff: allowing small imperfections in the response curve allows fewer filters with gentler slope. Ultimately I ended up with near-perfect frequency response measured in-room at the listening position:

  • Absolute linearity: from 30 Hz to 20 kHz, within 4 dB of flat
  • Relative linearity: curve never steeper than 4 dB / octave
  • Psychoacoustic linearity: about -0.8 dB / octave downslope (+3.9 dB @ 100 Hz, -3 dB @ 20 kHz)

The in-room treble response was excellent to begin with, thanks to the Magnepan 3.6/R ribbon tweeters. Some of the first EQs impacted that slightly, reducing the response from 2k to 6k, so I put in a mild corrective boost.

Subjectively, the overall before-after differences are (most evident first):

  • Midrange edge eliminated; mids are completely smooth and natural, yet all the detail is still there.
  • Transition from midrange to treble is now seamless, where before there was a subtle  change in voicing.
  • Smoother, more natural bass: ultra-low bass around 30 Hz is part of the music rather than a hint
  • Transition from bass to lower midrange is smoother and more natural.

In other words, audiophile heaven. This is the sound I’ve dreamed of having for decades, since I was a pimpled teenager with sharper ears but less money and experience than I have now. It’s been a long road taken one step at a time over decades to get here and it’s still not perfect. Yet this is another step toward the ideal and now about as close as human engineering can devise. The sound is now so smooth and natural, the stereo stops reminding me it’s there and enables me to get closer to the music, which now has greater emotional impact. And it’s more forgiving of imperfect recordings so I can get more out some old classics, like Jacqueline DuPre playing Beethoven Trios with Benjamin Britten and Arthur Rubinstein playing the Brahms F minor quintet with the Guarneri.

Throughout this process, I could detect no veil or distortion from the DEQ2496. The music comes through completely transparently. I measured test tones through the DEQ2496 in both pass-through and with EQ enabled; it introduced no harmonic or intermodulation distortion at all. That is, anything it might have introduced was below -100 dB and didn’t appear on my test. This is as expected, given that I’m using it entirely in the digital domain – no DA or AD conversions – and my EQ filters are parametric, small with shallow slope.

While I was at this, I created a small tweak for my LCD-2 headphones. Their otherwise near perfect response has a small dip from 2 to 8 kHz. A little +3 dB centered at 4.5 kHz, 2 octaves wide (3 dB / octave, Q=0.67) made them as close to perfect as possible.

Overall, I can recommend the DEQ2496. Most importantly, it enabled me to get as close to humanly possible to perfect sound. That in itself deserves a glowing recommendation. But it’s not a magic box. I put a lot of old fashioned work into getting my audio system in great shape and used the DEQ2496 only to span that last %. Like any powerful tool, the DEQ2496 can be used for evil or for good. So to be fair and complete I’ll list my reservations:

  • The DEQ2496 is not a magic band-aid. You still need to acoustically treat and arrange your room first to fix the biggest problems. After you do that, you might be satisfied and not need the DEQ2496.
  • The DEQ2496 is complex to use, creating the risk that you won’t get it to work right or you’ll get poor results.
  • To use the RTA feature you’ll need an XLR mic with wide, flat frequency response.
  • I cannot assess its long term durability, having it in my system for only a few days. Many of the reviews say it dies after a year or two,  but they also say it runs hot. Mine does not run hot, so maybe Behringer changed something? Or perhaps mine runs cooler because I’m not using the D-A or A-D converters. It does have a 3 year manufacturer warranty, longer than most electronics.