All posts by Mike Clements

Galaxy Note 4 Rooted Update

Tech
by Mike Clements

When your phone is rooted, the built-in system update won’t work. It will refuse to update itself. If you want system updates you must install them manually. This is how I do this on my Samsung Galaxy Note 4.

First, back up your phone. You should do a full binary backup with TWRP, and also back up individual apps (and their settings) with Titanium Backup. Do both because each serves a different purpose. A TWRP backup is useful if the update goes awry. It’s a full binary image that restores your phone and all its apps to its prior state. But you can’t restore individual apps. A Titanium backup captures your apps and their setups & data, which can be individually restored into a new system. But it includes apps and system data only, so it doesn’t help if the install goes awry.

In short, if your update is successful you’ll restore your apps from Titanium Backup. If your update fails you’ll restore your entire system from the TWRP backup.

Next, get the latest firmware. You can do that SamMobile. It’s typically a 1-2 GB download because it includes everything: boot loader, modem, Android, Google Apps, etc. After downloading the ZIP, unzip it to get an MD5 file that’s about twice as big.

Next, boot your phone to download mode: turn it off, then press and hold Power, Home and Volume Down. Connect it to a Windows PC (or VM) running Samsung’s Odin app. Make sure Odin recognizes the device when you plug it in. From Odin click the AP button, pick the MD5 file you downloaded from SamMobile and send it to your device. The phone will show a bar graph as the data is sent. When it’s done, Odin will show whether it was successful and the phone will reboot.

Give the phone a long time to reboot; don’t worry if it takes several minutes. When it comes up, all your apps should still be there because Odin doesn’t wipe the data partition. But your phone will no longer be rooted and the TWRP recovery will also be wiped.

To restore TWRP and root, follow a similar process. First download the TWRP tar file. Boot the phone to download mode and used Odin to push it to the device, as above. But this time, before pushing it, disable auto reboot in Odin (it’s on the Options tab). When the TWRP push is done, power off the phone, then boot it to recovery mode: hold Power, Home and Volume Up. It should boot into TWRP. Now you have restored TWRP recovery.

To root the phone, copy the SuperSU ZIP file to the phone. You can do this via a standard USB file transfer to your phone while it’s booted normally, or you can do this while the phone is  booted to TWRP, using adb file push from your PC command line. Then boot to TWRP and install the ZIP. The SuperSU install script will print stuff on the screen; follow the instructions, which is to reboot the phone when the install is done, and let it reboot itself a couple of times to complete the install.

When you’re done, you’ll have the latest OEM firmware update, with TWRP and root. And it should not wipe your data or apps.

Galaxy Note 4: Spurious Wakes and the Home Button

Tech
by Mike Clements

I love my GN4 phone but it has a problem: it wakes up (screen turns on) randomly while in my pocket. When this happens, the screen is on and contact with the inside of my pocket causes spurious random screen touches which is highly dangerous. Not just the risk of butt-dialing people, but it could also change settings, uninstall apps, etc.

The cause is simple. The home button wakes the phone, and it protrudes slightly, so it’s very easy to trigger while in a case or pocket. The best fix would be a system checkbox enabling users to prevent the home button from waking the phone. When disabled, the only way to wake the phone would be the power button, which is quite firm and never is accidentally pushed.

However, Samsung’s response to this is idiotic: “don’t put it in your pocket”. Because Samsung has their heads in the sand (to be polite) on this, users have come up with their own solutions,

One is to install Xposed. But this is a sledgehammer. It works but I didn’t want to deal with it.

Since my device is rooted, I figured there must be some system config text file I could edit to get what I wanted. I didn’t find exactly what I wanted–simply disable wake on the Home button. But I found something close enough that works: swap the Home and Menu buttons.

On my GN4 running T-Mobile Android 6.0.1, the file to edit was: /system/usr/keylayout/Generic.kl

Change two lines:

key 172 HOME
key 254 APP_SWITCH

So they read:

key 254 HOME
key 172 APP_SWITCH

Reboot.

The App Switch (Menu) button will now be Home button, and vice versa. And the Home button will not wake the phone. Nor will the Menu or any other button. The only way to wake the phone will be to press the power button.

My phone no longer randomly wakes up in my pocket. No more butt-dialing, accidentally rearranged home screens, uninstalled apps, or hot phone. No more wasted battery consumption. It’s a bit strange to get used to swapped Menu & Home buttons, but the benefits are worth it.

Note: I tried editing /system/usr/keylayout/gpio-keys.kl and removing the WAKE_DROPPED indicator. Disabling the home button’s WAKE feature without remapping buttons would be ideal. But this didn’t work; it had no effect. Apparently it worked in prior versions of Android, but Samsung changed the way keys are mapped in 6.0.1.

Ubuntu VLC DAC Audio

Audio, Tech
by Mike Clements

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.

Net Neutrality is Misguided

Economics, Politics, Tech
by Mike Clements

This article in Tech Crunch sums the argument in favor of Net Neutrality:
https://techcrunch.com/2017/05/17/defend-net-neutrality/

Everyone agrees on the end: we want an open internet. But there’s more than one means to that end. We disagree on the means, not the end. The Senate Democrat perspective assumes that ISP companies will infringe the speech of their customers or restrict their traffic flow, unless government regulators prevent this. So they conclude we must grant government this new power.

This perspective is misguided in two ways. First, it assumes new government powers are the only way to prevent ISP companies from restricting content or traffic flow in ways that harm consumers. Second, it ignores the risk and cost of these new government powers.

These assumptions are based on an idealistic perspective of government. This can be seen in some of the comments from proponents of Net Neutrality, like “its [the FTC] effectiveness may be a matter of opinion, but count on it: we’re better off with the FTC than without it”, or “that meant more paperwork to be sure, but consumers were safer”. This idealistic perspective ignores that fact that government agencies are just another type of large corporation, having their own self-perpetuating motives and are often used by entrenched companies to create barriers to competition & service that harm consumers in the name of “protection” and “safety”.

This highlights two nearly opposite alternatives to achieve the common goal of an open internet: regulation versus competition.

Net Neutrality regulation means rules controlling how to handle data content and movement. These rules must go through multiple approvals and public comment. They are necessarily reactionary and lag technology and innovation. They are also detailed and complex by nature. This attracts rent seeking and lobbying for loopholes by big entrenched companies, which makes the rules even more complex and inefficient, weaponizing the rules against competitors and hiding this fact under layers of complexity. This increases the complexity and cost of doing business, which reduces innovation, rewards established companies and deters new providers from entering the market. That means higher prices and less consumer choice.

For one example, consider T-Mobile’s zero-rating video data. Most of their customers loved this service, and the ones who didn’t could opt out at no charge. Yet providing this service got T-Mobile hauled in front of the FCC to explain themselves to regulators. They were exonerated, but this positive outcome was not preordained. It cost them thousands to defend themselves and they could have been subjected to service prohibitions and massive fines. When ISPs get hauled in front of the FCC to testify every time they do something regulators (or their competitors!) didn’t anticipate, say goodbye to innovation.

An example the Senate Democrats use is “fast lanes” vs. “slow lanes”. This is a red herring. Some kinds of traffic, like video, consume far more bandwidth than others. For the internet to function properly, these different kinds of traffic must be handled and routed differently. In short, there already are “fast lanes” and “slow lanes” —  it’s a technical necessity. The question is how we pay for them. Blanket rules like Net Neutrality risk creating a tragedy of the commons, where everyone uses bandwidth but nobody invests in developing it, or forces everyone else to pay the costs of heavy bandwidth users, which encourages over-consumption, reducing quality of service for everyone.

Yet the Senate Democrats do have a certain logic. With only a handful of monolithic ISP companies, there is no real competition thus in its absence some form of regulation like Net Neutrality becomes necessary. However, as citizens and consumers, we should not accept the inevitability of having only a handful of monolithic ISP companies. And we surely should not pass new regulations like Net Neutrality that will promote and lock in this dystopian future. Net Neturality is self-actuating and self-perpetuating. It creates and exacerbates the very problems it intends to prevent, as it purports to solve them.

In short, it is naive to believe:

  • That Net Neutrality regulations will stay ahead of fast-changing technology and creative interpretation by ISP companies.
  • That a big federal bureaucracy will make better decisions about how to allocate bandwidth and handle traffic, than ISPs directly negotiating with each other and seeking customers.
  • That Net Neutrality rules will be immune from rent-seeking, carved-out loopholes and other forms of regulatory capture by the biggest entrenched companies.
  • That these complex rules won’t raise the cost of business, restricting innovation, competition, and consumer choice.

Consider the alternative that the Senate Democrats ignored: competition. With competition, if one provider does something you don’t like, vote with your wallet and switch. You can switch at any time, for any reason: terms, privacy, cost, etc. Your vote hits the ISP where it counts: financially. Complex rules don’t bother them or protect you; their lawyers and lobbyists are better than yours, and are helping draft those rules.

Under competition, the rules we need are simple: prohibit fraud and establish property rights for access. There is no need for complex rules micro-managing data content and movement. This reduces rent-seeking and lobbying and keeps the cost of doing business low. Without complex rules dictating how to run their business, companies are free to innovate in technology and service to differentiate themselves, much like T-Mobile did for telecom.

But this works only under real competition. That means every person has a choice of several providers (not just two, a duopoly is not a market) and can switch between them quickly, easily, and cheaply. Unfortunately, we don’t have this in the USA. Why not? Primarily because multiple layers (local, state, federal) of complex regulations lock in existing ISPs and make it expensive for new companies. The reason some ISPs get away with bad behavior, like famously bad customer service and high prices, is because their customers have no alternative. Over-regulation protects them from competition. Adding even more more layers of regulation (e.g. Net Neutrality) will fix this like throwing gasoline on a fire.

To a large extent, the problem is local, not federal. Many of the restrictions that make it expensive and time-consuming for ISPs to compete are municipal and local rules and regulations about property access. Comcast and phone companies like CenturyLink love this – they’re already in there and the rules block competitors from entering the market. Net Neutrality does nothing to address this. It just adds even more regulation at the federal level.

Far better to address the root cause. Unwind the layers of regulations and municipal property access rules that lock in ISP companies and block competition. ISPs already are too much like utilities. This is the problem, not the solution.

Netflix New Rating System Sucks

Tech
by Mike Clements

In April 2017, Netflix changed their rating system. Instead of rating shows from 1-5, you now have only 2 ratings: up or down. And, the ratings Netflix shows you are NOT what other users have given the show. Instead, the rating Netflix shows you is how much Netflix thinks you’ll like the show.

This sucks. To be more precise, show ratings are now meaningless and useless. This is for 2 reasons:

1. The rating you see is not how others have rated the show. The show might be rated “5” by 90% of viewers, but it shows as “1” for you if Netflix thinks you won’t like it. The reverse is also true. The show could be rated “1” by 90% of viewers but shows as “5” for you if Netflix thinks you’ll like it.

For me personally, Netflix’s algorithm is quite poor. Shows I like often rate as 1, and vice versa. And it makes it impossible to see how others have actually rated a show. This is the underlying arrogance of this rating system: Netflix prevents you from seeing how others actually rated it, instead forces their own algorithm’s ratings on you. It’s like Netflix is saying, “Who are you going to believe: us, or your own lying eyes?”

Suggestion to Netflix: Never hide from customers the actual data they want to make decisions, and replace it with your own algorithmic interpretation. Especially if your algorithm sucks.

For example: most action movies have poor acting, cheesy dialog and plots with gaping holes. But there are a few good ones. You watch one good one, and Netflix floods you with abominable cheesy action movies all rated “4” or “5”. Not because they’re good – they’re not. Because Netflix’s stupid algorithm doesn’t know the difference. Humans do know the difference. If you could only see the actual ratings people have made. But Netflix won’t show you that.

2. Binary ratings have no way to differentiate between a show that was tolerable, one that was great, and the best show you’ve ever seen. All you get is up or down. This alone might be bad enough, but there’s more. This forces people to game the system, rating down shows they liked if they don’t want to see more shows like that. In the long term these fake ratings make the entire system worse. The system encourages–almost forces–people to game it with false ratings, which then spirals into a nose dive as those ratings make the recommendations even worse.

I completely understand a fast moving innovative company like Netflix must “move fast and break things”. But a rating system this arrogant and broken should never have rolled to production. However, I won’t cancel my subscription. At least not yet.

The astute reader will claim that Netflix never did show the actual ratings in the 1-5 system. The rating you saw was how Netflix thought you would rate the show. That’s true, but only partially true. The rating you saw was based on both–how others rated it, weighted mix with how they thought you would rate it. The bottom line is, however the old system worked, its ratings were more accurate and useful than the current system, which is completely broken and useless.

Call-out to Netflix: fix this broken ratings system!

Review: Audeze LCD-2 (2016)

Audio
by Mike Clements

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 return policy.

Review: JDS Labs Element

Audio
by Mike Clements

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 slight; you won’t 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. My first impression was to call this sound reference quality, but a side-by-side comparison with my Oppo HA-1 and Corda Jazz took it down a notch. All are clean and neutral, but the HA-1 and Jazz have a richness in the bass and sweetness to the mids and highs that the Element lacks. This difference is subtle, I hear it only on high quality recordings with my Audeze LCD-2 headphones. It disappears with Sennheiser HD-580s. I don’t believe this is euphonic distortion; the HA-1 and Jazz are honest neutral amps, nothing like the tubuliciuos sound of a great SET amp. Some people call the Element “dry” and I believe this is what they mean. It’s clean and neutral, yet it lacks the last bit of refinement.

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 Element’s USB DAC can accept up to 96 KHz – 24 bit. When listening to this digital source the amp has considerably less gain. I found this was caused by software mixer settings; after correcting the Element’s DAC and analog levels had about the same level. I used the Element’s low gain setting with my LCD-2 and HD-580 headphones, and it had plenty of unused range to the volume knob.

The Element has unbalanced analog line level RCA inputs and outputs and can be used as a pure analog amp. If you plug in an RCA input it bypasses the DAC. When powered off, the Element powers off the headphone output but is still “on” internally, routing the line level input to the analog output. When turned on, it powers up the headphone output and powers off the line level output. This gives the Element great flexibility as an in-line device and headphone amp.

The Element’s DAC does not run in async mode; it relies on your computer to clock the data. JDS claims this has no audible drawbacks, but my experience belied these claims. I heard occasional tics or brief drop-outs, suggesting that it was re-syncing slight clock differences. These were seemingly random, not reproducible when backing up and replaying. This might not happen with other computers. Driving the Element from the same computer in pure analog mode eliminated this issue. By “pure analog mode” I mean: instead of feeding the Element’s DAC from USB, I installed a high quality sound card and fed the Element the analog unbalanced line level output. This bypasses the Element’s DAC entirely.

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, 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 has excellent sound quality, though just a bit short of absolute reference quality. It’s fantastic the level of engineering, sound quality, and output power you get for the price.

Background: JDS Labs Element & Audeze LCD-2 2016

Audio
by Mike Clements

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

Audio
by Mike Clements

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.

LineageOS is Alive!

Tech
by Mike Clements

Last night I installed LineageOS 14.1 on my Galaxy Note 8 tablet.

I’ve been running CM 13 on this tablet for the past year or so and it works great – stability, performance, battery life. But the last build was Christmas Eve 2016, then Cyanogenmod died. I’ve been watching CM relaunch as LineageOS. They now have a home site and are running weekly builds for many devices. The Galaxy Note 8 happens to be one of these devices – with more to come.

The installation procedure is the same as CM. First, install TWRP recovery. You should do this no matter what build you’re running, even stock, because it has great features like full backup & restore. There are plenty of install guides. I had it installed already. Then, install LineageOS:

  • LineageOS Zip
  • Open Gapps Zip – use version 7.1 for LineageOS 14.1.
  • SuperSU Zip (if you want root)

The root ZIP provided by LineageOS did not work – TWRP had an error trying to install it. I used SuperSU instead, and it worked perfectly.

I’m still restoring backups & such, but first impression is that LineageOS 14.1 seems solid and fast. I’ll report back later after I get some time to use it.