More About the M-DEX, and a Cool Blog: Hack and Hear [en]

[fr] J'ai trouvé comment faire marcher le M-DEX correctement! C'est pas si mal!

I have just listened to the really interesting talk on audiology, hearing aids, and hacking them embedded below. Helga (@helgarhelgar), the speaker, is a friend-of-a-friend, fellow geek (probably geekier than me!) with hearing aids. And she has a few years’ headstart on me exploring the tech. I’ve just started going through her blog, hack and hear.

Midway through her talk, I was inspired to give the disappointing M-DEX another chance (I wrote about it in my previous article about hearing aids).

Lo and behold, I figured it out, and it doesn’t work too badly!


Here’s the trick:

  • first of all, it increases the general volume of the hearing aids, so the horrible crackling sound I heard when I tried to use it with the phone is actually (mainly, as far as I can tell) outside sound: muting the “room” (with the mute button) takes care of that
  • second, music sounds like crap, even on the music programme (the M-DEX music programe — as far as I’m aware my aids don’t have one yet); this is maybe because of my hearing aid settings or programme, and understanding better how compression works and feedback loops are countered, I’m also understanding why my hearing aids behave badly during my singing rehearsals => so I’m sticking to voice for the moment
  • third, the M-DEX user interface is pretty crap, it’s hard to figure out which button to press when to obtain a desired result: what I do now is first mute, then press the middle button to get to the bluetooth menu, then enter that; however, if bluetooth is on and the device is selected (on my computer for example), it “switches on” when I start playing sound. Pressing the red button when listening to sound from the phone/computer and when on mute goes back to the main programme and un-mutes (if you’re just on normal mute it doesn’t do that). Very confusing. It’s probably going to take me some time to learn when not to press on which button.
  • fourth, it’s possible to pair the M-DEX with more than one device (I mistakenly thought it wasn’t) — to prevent the M-DEX from kicking into gear unexpectedly, I turn off bluetooth on the devices if I’m not using them, or turn off the M-DEX
  • fifth, the M-DEX needs to be pretty close to the hearing aids (which is why they provide a lovely strap so you can hang it around your neck like a necklace), or at least somewhere that is at a stable distance — if you move it around it crackles really annoyingly, and if an ear gets out of range the sound in it dies.

So, I might end up keeping the expensive toy after all if I settle on the Widex hearing aids! Still need to test it with a real phone call though, which I’m not going to do while in Spain.

Update: looks like I’m not alone in thinking the M-DEX is suboptimally designed!

After the glowing review of my hearing aids and my audiologist, it is unfortunate that I have to be so negative about the other component in question. The M-DEX is a piece of shit — I am a software engineer and architect, and I have never seen such poor interface quality or assumptions about the listener.

11 thoughts on “More About the M-DEX, and a Cool Blog: Hack and Hear [en]

  1. I saw one report that the M-Dex can handle as many as 8 pairings; but this does not seem to the the case with iOS 6.0.2, as I have to re-pair it when I switch between my iPod Touch 4 and iPhone 5.

    Also, even though the M-Dex presents as an A2DP headset to the sending device, in fact (and unlike the TV-DEX) only transmits a channel mixed monaural signal to the hearing aids. Worse, the headphone audio input jack is monaural, only sending one of the two stereo channels to both hearing aids: This I can tell because there’s a particular Color Beautiful commercial that is (annoyingly) played every hour on a particular DFW broadcast station where the speech audio switches between channels: I can only hear half of the words when my iPod is plugged in via stereo cable.

    Worse, when I went to the Widex Clear training session in August 2011 (and wearing a pair of Clear440 Fusion instruments with my M-Dex), I explicitly asked if there would be a firmware upgrade to enable stereo transmission and/or using the USB jack for digital audio input; and I was informed:

    1) The M-Dex is not capable of firmware updates, whhich I found out a year later that it’s due to them using ASIC architecture instead of FPGA architecture (probably to save battery drain and also to deal with their proprietary digital signal transmission protocol);

    2) The USB jack only has two pins connected for charging, and is not capable of accepting anydigital data.

    That being said, the Clear uses a 33k sample/second rate in the ADC connected to the mics with a 107 dB input dynamic range (IDR); and 22k sample/second rate for the digital audio signal path, both industry-bests.

    For much more on the ASIC vs FPGA issue, please see this article, including the footnote

  2. Anybody know if Widex is going to release a new version of M-Dex, I looking to buy but turned off by the reviews on current one. maybe if I can find a used one, I will try it.

  3. Yes, the M-Dex is entirely unremarkable. It does an OK job of transmitting phone calls, though the external noise — e.g. traffic when walking, others talking when in a room, remains. As for streaming, it does a miserable job. And Widex, despite saying that there’s a second generation M-Dex coming, doesn’t seem to have that in production, even now, half way through 2015. I wonder if they even have it in development. The HAs are very good, but the peripherals are miserable, almost as bad as Widex customer service (I use the term service with caution)

  4. I must have had the Widex M-DEX for years but never used it. I still have my widex aids but am trying phonak as i need an upgrade. But I’d like to try the MDex before deciding. I have plugged it in and nothing happens. Shouldn’t it charge up?

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