A Disappointing Reality, of Manufacturing Today

In This Posting, I wrote how I had my “LG Tone Pro HBS-750″ Bluetooth Headphones around my neck, with the ear-pieces attached to the end of the collar-piece via magnets, that I put my head down on a cushion for a moment, and that immediately, I had a kink in the very thin cable that connects the left ear-piece to the collar-piece.

This happens because the very thin cable has as outer tubing, a rigid kind of material, which develops kinks especially easily. Rigid tubes will form kinks instead of bending.

The headphones have not stopped working yet, but I am very worried by how long it may only take, until that happens. Right now it strikes me, that the average lifespan of a pair of Bluetooth Headphones is 3 days.

Inside the ear-pieces, there are driver coils, which produce variable thrust, in response to voltage and current changes, and which move slightly, across the magnetic field lines of permanent magnets. These driver coils have traditionally been made out of enameled wire.

The way devices were manufactured a long time ago, there would be some kind of contacts inside the ear-pieces, which transfer the current from the enameled wire of the coils, to thin braided wire in the cables that connect the ear-pieces to the collar-piece.

What I find very disturbing, is the degree with which companies have cut corners. The companies have spared every expense. By now, the enameled wire of the coils is merely extended down the tube, that connects the ear-pieces to the collar-piece. That is all.

What this means, is that instead of having changes in the series resistance, the probable mode of failure will eventually be a break in the enameled wire. And when that happens, there will be absolutely no way to repair the damage, other than just to spend another $ 90, and to buy a new set of BT headphones.

Because of a tiny little wire, that was never designed correctly in the first place.


(Edit : ) Also, the free end of this one enameled wire is just soldered into the circuit-board, on either side of the collar-piece, so that an earnest attempt to replace the whole ear-pieces, requires that we use a soldering iron. After we undo the trick, which secures the thin cables to the shroud of the collar-piece mechanically. And it just so happens, that not any type of soldering job will be good enough. The soldering iron needs to be low-wattage enough, that it is safe to use with modern, small-component circuit-boards. It is possible for some people to be able to do basic soldering jobs, but not ones at low wattage, on the tiny circuits of modern circuit-boards.

I should just point out, that this particular problem is not specific to LG. For example, I have owned Sony, wired, over-the-ear headphones for a long time, where for one reason or another, the outer tubing on one of the cables has slid, and has exposed the enameled wires underneath, right at the edge of the headphone where there is a lot of wear and tear.

But on those age-old Sony headphones, that enameled wire next lasted for a long time, and never really broke.

(Edit : ) There exists a recent advancement, which makes the concept more feasible, and which did not exist in that past era, which I still use as a reference-point. It is possible to manufacture an apparent wire which looks at first glance like a single, enameled wire, insulated with a transparent resin, but which under closer inspection, is braided out of several, even-finer wires. Therefore such a supposed wire, is also not truly a wire.

This is one of the improvements which also help explain, why the enameled, braided wire does not fatigue close to the driver coils, which deflect back and forth 20,000 times per second.

My Sony headphones used that, and it would only be fair to assume, that my LGs also use that. But, because the wires of my LGs have not been exposed (so far), I cannot be 100% certain.


I have damaged my HBS-750 headphones slightly.

The “LG Tone Pro HBS-750″ Bluetooth Headphones differ from the newer “Infinim” Headphones, partially in that the HBS-750 still have a thin cable connecting each ear-piece to either side of the collar-piece, that cable being on the outside of the collar-piece. I read that with the Infinim series of headphones, there is an even thinner cable on each side, which retracts inside the collar-piece. A review by other testers suggested doubt, about the longevity of these ultra-thin cables, of the Infinim-series headphones. The thin cables of the HBS-750 are at least not quite as thin.

But after only owning my HBS-750 for a few days, I made a foolish mistake with them. With the ear-pieces of mine, held in place in each of the magnets on the ends of my collar-piece, I lay down on a cushion, even though I had my collar-piece around my neck. I lay down on my left side while watching television, with my actual phone placed safely on a table in front of me.

What has happened as of yesterday evening, is that the very thin cable on the left side, has developed a slight kink.

There is a hypothetical possibility of such a kink affecting sound quality. In general, headphones should operate with the sound balanced perfectly between left and right. A kink in a cable on one side can do two things:


  1. It can short-circuit the cable.
  2. It can insert some small amount of resistance, in series with the ear-piece in question.


The problem lies in the fact, that even if HQ ear-pieces are just stated to have ’32 Ohms’ of impedance, in reality their impedance curve is frequency-dependent. Ideally, this impedance might then be equal to 32 Ohms – neglecting any imaginary component – in the middle of the audible spectrum. But on the low-frequency end, as well as on the high-frequency end of the spectrum, it is likely that their impedance is much lower. This is due to the fact that a certain part of this impedance is actually due to the resistance of the wire in their coils, while most of it is due to the fact that their coils move, within the static magnetic field of their magnets.

Hence, to insert maybe ? 1/2 Ohm ? in series with one of the ear-pieces, will not affect performance much in the middle of the spectrum, but may affect performance at either end of the spectrum, where these hypothetical 1/2 Ohm will be in series with much lower impedance, due to the ear-pieces themselves.

What I have found, thankfully, is that for now, the actual kink in that cable, has not affected the sound coming out of the left ear-piece one iota. Yet, over time, these thin cables may deteriorate below the condition they are in right now. In fact, they may receive more kinks and blemishes in the near future. All of which prompts the question, of how long blue-tooth headsets are expected to last in general, with normal wear and tear.

One lesson learned: Do not lie down on one side of the head, while wearing them… The next time, I may not be so lucky. Right now, my sound still seems to be perfectly-balanced, and not in any way that favors specific frequency-ranges on one side. I also still get good, rich bass and treble on the left side…