Beware of LEDs that stay constantly-lit.

Today we have many portable devices, which attempt to run off battery power for a long time. At the same time, these devices can have LEDs, which indicate their status for the convenience of the user. There is an aspect to that, which some users might not fully realize, but which I think is important nonetheless.

If the LED is to stay constantly lit and bright, then the amount of current / power it consumes will be high, and will therefore be a strong drain on the battery as well. Additionally, our human eyes are less sensitive to blue light than they are to red, and less so to red light, than they are to green. Therefore, a blue LED which is to seem bright, is consuming an additional penalty of power, to appear as bright to our eyes, as a red LED is supposed to seem.

My new LG Tone Pro HBS-750 Bluetooth Headphones have all the correct behavior, in that during normal use, their Blue LED only flashes very briefly, in a code that restates the battery level, but with a duration of much less than 10%. They also have the correct behavior, in that their LED stays Blue continuously, when they are in pairing mode, which is only supposed to be a brief operation compared to their normal mode. And, when they are charging, some combination of their Red and Blue LED stays fully lit, because power is assumed to be in abundance when charging.

Now, the supposed HBS-730 headphones which I had before, would have a much brighter Blue LED, which was supposed to stay solidly Blue when pairing. Mine alternated between Red and Blue when pairing. And mine stayed fully lit 100% of the time, when in Standby, a mode in which the headphones are supposed to be drawing less current, than when actually playing music. And the LED on mine, would flash in Blue with 50% duration, when I was listening to music.

This was a design failure, and was also inconsistent, with what the LG manual for the HBS-730 explicitly states. According to that manual, their LED was also to stay fully Blue only when pairing, and was supposed to flash briefly, not 50% of the time, while playing music. This correct behavior would have been very similar to what my present HBS-750 Headphones do, but did not correspond to the real behavior of what I had been sold.

Dirk

 

HBS-750 Equalizer Function Actually Useful

The shape of my ears has generally been a problem, for ear-pieces to fit, in my past. Mine are narrow, so that I need the most narrow inserts already. But then it can happen to me, that my facial muscles tense differently, at different times of day, which I believe causes a subtle change in the shape of my ears. Do not laugh. And so simply because I may be cracking a smile, I will also be cracking a non-airtight gap between ear-pieces that just fit, and my ears, which results in a sudden loss of deep bass.

The LG HBS-750 Headphones have an equalizer function, that switches between three modes:

 

  1. Bass boost (the default),
  2. Flat,
  3. Treble boost.

 

When I try these settings indoors, at first the difference seems so slight, I tend to think, ‘What a waste of an equalizer.’ But when I am walking outdoors, I now find that switching from mode (2) above back to mode (1), gives me back exactly what I lost, because the ear-pieces are no longer airtight in my ears.

I tend to find that mode (3) is less useful, because it emphasizes the aspects of aptX -compressed sounds, that are more scratchy. But then again, maybe somebody else appreciates the treble boost feature of this headset.

Now, one way to tell whether a product is a forgery or not, is by the fact for example, that the equalizer on the HBS-730 I was playing with before, did not kick in. But in reality the logic is more confuted than that. The manual of the HBS-730 clearly states, that the equalizer settings cannot be changed, if that unit is in aptX mode.

The manual for the HBS-750, which I am using now, clearly states that its equalizer settings are available, when this unit is in aptX mode.

Further, today, when testing the HBS-750, I did listen to music for 7 hours straight. It was my initial intention, to run the batteries all the way down, just so that I could recharge them once, and allow them to live up to full capacity ‘in the field’, later. But after about 6 hours of my own music, I grew too sick of that. I could not force myself to listen to more than 7 hours of music, at which time the battery-level announcement still told me that the batteries were at “medium” level.

They then needed 70 minutes of charging time, to come back up to full.

With the HBS-730, I could not listen for more than 135 minutes, before they were dead. And to recharge the supposed HBS-730 only took 35 minutes, cycle after cycle.

Dirk

 

aptX Handles Polyphonic Sound Surprisingly Well.

Right now, as I am typing this, I am listening to Beethovens 9th Symphony on my real “LG Tone Pro HBS-750″ Bluetooth Headphones. The quality of sound is dramatically better, than what the fake HBS-730s had produced, simply because those were fake.

This recording of Beethoven is stored on my phone, as a series of FLAC files, and Android Lollipop devices are well-able to play back FLAC files. I did this, in order to test the fake headphones at first, because I was not sure whether their poor performance then was due to some interaction of aptX, with MP3 or OGG compression, rather than due to the implementation of aptX I was getting. Playing back a FLAC file is equivalent to playing back a raw audio file.

From what I read, aptX not only splits the uncompressed spectrum into 4 sub-bands, but then quantizes each sub-band. The 4 sub-bands are approximately from 0 to 5.5 kHz, from 5.5 to 11 kHz, from 11 kHz to 16.5 kHz, and finally from 16.5 kHz to 22 kHz. These sub-bands are then compressed using ADPCM, which allocates 8,4,2,2 bits to each.

This implies, that the first sub-band contains the bass and the mid-range, and that what I would call ‘melodic treble’ sounds, do not extend beyond sub-band 2, since treble notes with fundamental frequencies higher than 11 kHz are not usually played. And sub-bands 3 and 4 simply add texture to the sound. This means, that to allocate fewer bits of precision to sub-bands 3 and 4 ‘makes sense’, since our natural way of interpreting sound, already sees less detail at those frequencies.

A question which I had raised earlier, was if the act of quantizing the sub-bands 3 and 4 greatly – down to 2 bits in fact – will damage the degree of polyphony that can be achieved.

And now that I possess true headphones I am finding, that the answer is No. The sub-bands 3 and 4, are still capable of being played back in a multi-spectral way, even though their differentials have been quantized that much.

(Edit 06/25/2016 : ) Instead of receiving a regular sequence of +1, 0 and -1 data-points, it is possible to receive an atactic sequence of them. The first thing that happens when decoding that, is an integration, which will already emphasize lower, original frequency components that have been deemphasized. After that, the degree with which the analog signal can be reconstructed is only as good, as the interpolation. And in practice, interpolation is often provided by means of a linear filter which has more than two coefficients. Having a longer sequence of coefficients, such as maybe 6 or 8, provides better interpolation, even in sub-bands 3 and 4, which we supposedly hear less-well.

 

I do find though, now that the entire signal is much more clear, that when I listen closely, the highest frequencies belonging to Beethovens 9th, seem to have slightly less resolution than they are truly supposed to have. But not as much less resolution, than I am used to hearing, due to poor headphones, or due to MP3 compression.

It is already a dramatic improvement over what my past told me, that today, Some Bluetooth Headphones can play back high-quality music, in addition to being usable for telephony.

Now, Beethoven died before he finished his 9th symphony, and later artists officially completed it, by adding the 5th movement, which is actually “Shiller’s Ode To Joy”. According to what I am hearing, that 5th movement is compromised more by the aptX compression than the first 4 were, that were actually written by Beethoven.

The reason seems to be the fact, that Shiller’s work is more operatic, and has choruses singing very high notes, which results in a lot of the signal energy being in the 2nd, 3rd and 4th sub-bands. So when I hear that movement, I can hear the quantization quite clearly.

It is usually not a preference of mine, to listen to this 5th movement, because I don’t find it to be authentic Beethoven. Right now I am listening to it, and observing this effect with some fascination.

Dirk

 

I now have LG Tone Pro HBS-750 Bluetooth Headphones.

And unlike how it went with the previous set, I paid the full price for these, and know that they are genuine.

I can now comment accurately for the first time, about the “aptX” sound compression they use.

I understand that most of the music that I will be playing, has already been MP3 or OGG compressed. But with my simple headphones, that were wired to the stereo mini-jack on my phone, there was a loss in quality, just in getting the sound to my ears, after MP3 or OGG decoding. With aptX, it could be argued that there is also some small loss of quality in getting the sound to my ears.

aptX, and the HBS-750 headphones, are able to get the sound to my ears, after lossy decompression, better than the wired headphones could. So the only sound artifacts that I will ever hear with these, will be those due to MP3 or OGG, and the OGG files will play better again than the MP3 files did, as the OGG files are supposed to do.

The sound of these headphones is truly superb.

Further, the reason for which the suggested app ‘Tone And Talk’ was not recognizing the supposed HBS-730 headphones, was the mere fact that this app was able to read the meta-data of those, and was able to determine, that those were just not on the list of supported headphones, even though I was fooled into believing that they were.

Tone And Talk works properly, with the HBS-750 headphones, that are genuine LG headphones. That is, unless I am to do a detailed test of this app, which may come later. But the app does not just sit there and stay lame, as it did with the counterfeit headphones.

Dirk