[jonny_chad]

Hey guy's, I got a question for ya.

I am completely deaf in my right ear due to a recent head injury. Now I'm about to go out and buy a decent pair of headphones (price range = $US80-200). I would like to know how to solve the stereo problem, which sends one channel of sound to my dead ear. I'll be using a sony discman which I'm pretty shore doesn't have a mono setting.

First of all, is it possible (and not extremely difficult) to convert a pair of headphones (say Sennheiser HD200's), so that both channels are wired into one ear? combined channel mono.
If it is possible...then how?

If this isn't possible can you purchase special leads or headphones that could achieve the same thing. If so, what?

Thanks heaps. Hope someone can help out.
Jonny

 

[Budgie]

Bummer about the hearing, jonny. The easy way to get mono for your headphones would be to use an outboard amp, such as an Airhead or similer (or build your own) and then to convert the input to mono at the input of the amp. This can be done with a stereo to mono converter plug or by just connecting the left and right inputs together. You then will get mono signal going to both sides of the headphones.
It is much harder to do that at the output of the amp, without causing problems.

 

[needgoodphones]

However note that this too has it's problems. Sounds that were 180 degrees out of phase (which is a technique that many studios like) almost completely cancel. It would probably be better to make a crossfeed filter with a very high amout of crossfeed.

 

[jonny_chad]

Quote:

better to make a crossfeed filter with a very high amout of crossfeed

Love to know what one of these is. Also how I would go about making it.

Cheers,
Jonny

Note: I'm by no means an expert in this area.

 

[eric343]

Sorry to hear that man

(no pun intended)

As far as I know there isn't any way to fix the sound-out-of-phase problem, since a crossfeed filter will also be affected by the phase canceling (since it's just blending the signals, though in a special way - it [hopefully] does a minimum of phase shifting). However, a strong crossfeed would have the advantage over a stereo->mono converter that since it doesn't blend the two channels completely, you'd still hear the out-of-phase signals, though considerably quieter.

 

[averydonovan]

Quote:

Originally posted by needgoodphones However note that this too has it's problems. Sounds that were 180 degrees out of phase (which is a technique that many studios like) almost completely cancel. It would probably be better to make a crossfeed filter with a very high amout of crossfeed.

One possibility to get around this to build an amp with two different parts. One is a normal amp stage with both left and right bridged to mono at the inputs. The other uses two opamps in parallel, one set up as normal and the other set up as inverting, and each channel would be hooked to each opamp. The idea is that only when the left and right channels are out of phase that a signal will come out, and be added back to the original amped signal. So those formerly inaudible in mono sounds would be heard again. I don't know if this would actually work, and there may be simpler ways to do it.

 

[eric343]

You know, that might work...

 

[averydonovan]

Here's a crude ASCI representation, so you can see what I'm talking about:
Quote:

Maybe we can simplify it by just using one opamp, or a single comparator (although I don't know if comparators would be of high enough quality for audio).

Edit: The simplest way to build this is to have all those opamps above in unity gain, and then have the output go through voltage gain. Doing it like that you can use a single quad opamp if you wanted to do a simple CMOY type amp.

 

[Jupiter]

I think jonny_chad is looking for an audio mixer (recording terminology) or summing amplifier (EE terminology).

 

[Xanadu777]

Just a thought here but I remember having a pair of quadraphonic headphones in the 70's. I know you can still get them on ebay.

What I'm thinking is one ear stereo. Since there are 4 drivers in these, 2 per side (front/back x2), rewire so left and right are in your good ear (instead of front left/rear left or front right/rear right. Quad headphones have 2 seperate 1/4 plugs, one for front one for rear.

At least you would have real stereo instead of mono.... Seems to me some of these headphones were decent and in your price range.

 

[Haoleb]

im sure with a combination of different cable adapters you could get the effect your looking for, much cheaper than the above mentioned.

 

[Squalish]

Quote:

Originally posted by Xanadu777 Just a thought here but I remember having a pair of quadraphonic headphones in the 70's. I know you can still get them on ebay. What I'm thinking is one ear stereo. Since there are 4 drivers in these, 2 per side (front/back x2), rewire so left and right are in your good ear (instead of front left/rear left or front right/rear right. Quad headphones have 2 seperate 1/4 plugs, one for front one for rear. At least you would have real stereo instead of mono.... Seems to me some of these headphones were decent and in your price range.

I think that would still destroy 180 degree out of phase sounds, , but acoustically instead of electrically.

 

[Budgie]

There is very little sound recorded 180 out of phase in recordings. It will cost nothing to try it my way. If you have any troubles (and you won't) it is very easy to undue. I have used this solution in my work many times over the last 25 years, without any problems.

 

[jonny_chad]

Thanks heaps guys for all your suggestions.
Although the canceling of out of phase sounds may be a problem I think I will try Budgie's solution first, because it does sound the easiest to setup.

Before I do, I just have a question regarding Budgie's idea. What's the advantage of using the amp after the stereo to mono conversion other than the normal benefits from using a headphone amp?

Its just that I don't want to invest in an amp if its not entirely necessary, especially if the out of phase thing is going to be a problem.

 

[Budgie]

The advantage is that the input to the amp will ignore the two channels being tied together, since the input impedance is much higher then the output impedance of the source driving it.

If you would like to check my opinion, feel free to dig up the schematic of any preamp with a stereo/mono switch. They just bridge the two channels together at the input. Cheap, easy and effective.