Aiwa HP-CN6 Noise Cancelling Headphones - Design or manufacturing.

I bought my Aiwa HP-CN6 Noise Cancelling Headphones at Panamá airport, kind of shopping mall in an airport. It´s fun there because you find street hitting items at a good price.

But of course often when you buy at an airport, if you are in the middle of connecting flights, there won´t be too much time for testing and checking, so i went to my international flight and opened my new headphone hoping in have a nice mp3 hearing while traveling with my also new Treo 650 and an adapter that i made for the micro headphones plug. But how big it was my surprise when plugged, activated the noise cancelling function and started to hear a uneven sound signal from the phone Portable Tunes application.

As it´s logical, the first thing i did was to switch back to no-noise position just to check that it wasn´t a problem of the song itself. Perfect sound flowed when noise cancellation function wasn´t operating. Then i swapped hearing position, left to right and right to left by simply rotating the headphones 180 degrees vertically. Same thing but this time in my right ear, sot it wasn´t a problem of my own ears. Asked to the person beside me to try and she noticed the same thing. Then i played a different song, just to check if it wasn´t a defect due to this particular song... It wasn´t. Same thing with several different songs, so what i did was to look for a monophonic mp3 file (found several 60´s oldies with this characteristic) and played. Again, a noticeable amplified noise in the left ear matching the outside ambient noise, while right ear was perceiving and enjoying the virtues of noise cancellation.

Then i blamed the connector that i made, so before after the plain was at cruise altitude, i took my laptop and started Media Player to check again. Same situation. Now i was convinced of a manufacturing defect. Unfortunately i made my way back to Bogotá through Costa Rica, so i had not opportunity to change the headphones in Panamá.

Then, at first, i associated remotely this with the problem that first transistor portable radios from Sony had in the beginnings when in its way to US had to pass through the Panamá Canal, ruining part of its components because of a particular condition of humidity and heat. I knew also that this was mostly unprovable because of strict quality controls in most well recognized make manufacturers like Aiwa.

Then, back in Bogotá i went to a store where i knew anybody may try an item before buy it, so i took the chance.

Same thing, same disgusting uneven sound in left ear in the second headphone tried. Two headphones probably well separated in time at manufacturing time. Then i get convinced that i was dealing with a design problem. Unfortunately, i went back to Panamá´s Airport more than 90 days after purchase date, so my warranty was void. Then with no valid warranty i decided to disassemble the headphones and check if there was any tunable mini-knob (like an adjustable variable resistor or condenser), but found a monolithic circuit with nothing tunable. I assembled them again and definitely reach at the conclusion of a design defect on those ones.