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Old 4th October 2011, 03:34 AM   #1
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Default unusual mono help request

Hi all,

My father recently suffered from an acoustic neuroma and lost one ear entirely. I wouldn't call him an audiophile but he has always enjoyed listening to music. The loss of half his hearing has been trying for him. Seeing him listening with a single ipod earbud, the other just clipped off, was pretty sad.

I would like to set up a good headphone system for him. I will probably make something based on a single grado driver. Not sure what kind of amp but there are a lot of interesting choices on this and other boards, Ill probably just give one a go. What I need help with is how to best sum the channels. I also wonder if there might be something better than just a simple mono signal. I thought perhaps delaying and reducing the other channel might give a pseudo stereo effect but perhaps that would just sound like an odd echo?

Thoughts, suggestions, circuits all appreciated.

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Old 4th October 2011, 08:32 AM   #2
Meldrew is offline Meldrew  England
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If you google "bone phones" you may find something applicable.
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Old 4th October 2011, 05:10 PM   #3
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I looked into "bone phones" but Im afraid they wont work for me. My father actually lost the entire inner ear structure from the surgery. It is not limited hearing, there is no ear there.

I know I could simply sum the inputs with a couple resistors. Seems pretty basic but I have a feel it has some limitations. Wouldn't this kill some of the signal? Wouldn't one channel drive the other to some degree? Is there an active version that would work better?

No thoughts on any psycho-acoustic tricks that bring a sense of depth/stereo to a mono signal? I dont even know how to begin searching for something like that. Most info out there starts with the assumption of 2 ears!
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Old 4th October 2011, 06:10 PM   #4
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Sorry to read of your dad's hearing loss. I truly empathize. You could send the output of the two resistors into an op amp. From there, regaining any "sense of stereo" would be difficult to impossible AFAIK. Some sort of ambiance processing may add a sense of space and/or depth to the playback. It's all I can think of.
It is error only, and not truth, that shrinks from enquiry. - Thomas Paine
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Old 4th October 2011, 06:27 PM   #5
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Location: Midland, Michigan
How tragic for your Father.
Summing the iPod output channels through external resistors should work for you.
You shouldn't lose anything in the audio mix. Of course, you will lose some output power from the iPod.
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Old 4th October 2011, 06:46 PM   #6
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well an idea,,for what its worth....
How modding and older closed style headphone, rip out the guts and shove a set of IEM's in there, mounting both the right and left into the one side ?
or perhaps one of those big custom molded IEM's but with both drivers it ?
Good luck
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Old 5th October 2011, 05:07 AM   #7
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I guess summing with resistors will work then.

Not sure what an IEM is...?
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Old 5th October 2011, 12:26 PM   #8
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Sorry ! In Ear Monitor, IEM or earbuds
I think a custom mold with both drivers in it.....I think there would be lots of room, there are kits for you to make your own molds and stuff.....
here are some pics.custom iem - Google Search The drivers will have to be back further in the housing, a little further away from the ear canal but it should be do-able either DIY or find someone to do it for you. just google custom IEM.
Good luck !
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Old 5th October 2011, 02:11 PM   #9
sreten is offline sreten  United Kingdom
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Location: Brighton UK

You really can't do anything better than simple mono, certainly not any sort
of pseudo stereo effect, any delay will give comb filtering effects and sound
downright weird.

There is a lack of detail in your plans and what quality / budget is wanted.

rgds, sreten.

Posting on Head-Fi.org - Headphone forums and reviews for audiophiles
would no doubt turn up some quality options with one damaged
driver you may get for next to nothing, and some good advice.

Last edited by sreten; 5th October 2011 at 02:15 PM.
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Old 5th October 2011, 04:44 PM   #10
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I am familiar with head-fi but more familiar with this board. Figured I'd start here.
Lack of detail in my plan is due to my desire for my father to hear normally conflicting with reality.
I looked at the IEM's but they look too much like hearing aids. Its a sensitive subject.

I think it might be best to simplify this. Ill make something that looks like a plug adapter that sums mono. This will let him listen comfortably at the office, coffee shop etc from any normal source without looking too odd.

As a separate project Ill introduce him to better headphones. Im a fan of grados and I think he will be too. If he likes and uses them I will look into making a little mono amp. Ive been wanting to get my feet wet with tubes, guess its a good time for that.

Thanks all,
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