Combining vario and radio output into one speaker

Yes but the stuff you are linking to is *irrelevant*. These circuits are talking about driving line level inputs. Those line level inputs have ~tens of kohm input impedance -- that is not at all what you are trying to do. You are trying to blend a signal that is driving a very low impedance (nominally 4 ohm or 8 ohm) speaker. If you want to blend low output impedance signals to drive something like a speaker you need to buffer that low impedance, which gets you into an op amp or similar buffer on each channel and and/or drive a summing amplifier directly, then a power driver circuit. Basically you are building an active audio panel. All that complexity and need to power it and have yet another thing to fail.

The simple solution is use two speakers. Not hard at all.


On Thursday, February 26, 2015 at 9:40:28 PM UTC-8, Paul B wrote:
On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:


Now you're getting fancy :-)

Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four .

Cheers

Paul

On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:


Now you're getting fancy :-)

Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four .

Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.

Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.

https://learn.sparkfun.com/tutorials...ny85-use-hints

OK, I'm being silly.

I feel absolutely old-fashioned what with my vario speaker velcroed to
the top of my glare shield and my radio speaker mounted to the bulkhead
behind my right ear. But, hey! It works.

On 2/27/2015 12:00 AM, Bruce Hoult wrote:
On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:

Now you're getting fancy :-)
Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four .
Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.

Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.

https://learn.sparkfun.com/tutorials...ny85-use-hints

OK, I'm being silly.

--
Dan Marotta

On Thursday, February 26, 2015 at 11:00:11 PM UTC-8, Bruce Hoult wrote:
On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:


Now you're getting fancy :-)

Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four .

Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.

Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.

https://learn.sparkfun.com/tutorials...ny85-use-hints

OK, I'm being silly.

Oh come on, where is your ambition? Once you go digital there are lots of great options. You could add a digital parametric EQ, MIDI programming to customize the vario output, etc.

What is wrong with this industry and lack of innovation? Why has no vario developer offered MIDI output until now?

:-)

On Saturday, February 28, 2015 at 9:51:53 AM UTC+13, Darryl Ramm wrote:
On Thursday, February 26, 2015 at 11:00:11 PM UTC-8, Bruce Hoult wrote:
On Friday, February 27, 2015 at 6:40:28 PM UTC+13, Paul B wrote:
On Friday, 27 February 2015 15:05:45 UTC+10, Bruce Hoult wrote:


Now you're getting fancy :-)

Thanks Bruce

The fancy is what I want to avoid, as the initial idea was to simplify things - i.e. one speaker instead of four .

Well, the good news is all those bits (except volume controls with knobs) would cost less than $10 in total and fit on a board a maximum of a couple of square inches in size.

Heh. These days you could use a $2 ATtiny85 microcontroller in an 8 pin DIP package. 20 MHz CPU. 3 10 bit analog to digital inputs. Scale and add them digitally. Output a pulse-width modulated 1 bit signal at 50 KHz or so, low pass filter (i.e. a resistor and a capacitor), then to the amplifier.

https://learn.sparkfun.com/tutorials...ny85-use-hints

OK, I'm being silly.

Oh come on, where is your ambition? Once you go digital there are lots of great options. You could add a digital parametric EQ, MIDI programming to customize the vario output, etc.

What is wrong with this industry and lack of innovation? Why has no vario developer offered MIDI output until now?

:-)

If you're going to do all that, you might need a more powerful CPU -- how about a full 32 bit ARM in an 8 pin DIP package for about the same price?

https://learn.adafruit.com/getting-s...pc810?view=all

On Friday, February 27, 2015 at 2:03:14 PM UTC-5, Dan Marotta wrote:
my radio speaker mounted to the
bulkhead behind my right ear.

Is it better to have the radio audio output balanced between both ears? I assume that this would result in higher comprehension of radio calls with lower sound pressure (DB) driving each ear. If the speaker drives both ears equally, can you turn down the volume and get the same or better comprehension?

Is it better for the radio speaker(s) to have line of sight to the ears rather than bouncing the sound energy off the hard surfaces in the glider?

My thought is that the best solution is TWO small speakers each with line of sight to one ear. If the audio output bounces off a variety of hard surfaces, the echos will combine and make the signal that reaches the ears 'fuzzy'. So higher sound pressure will be needed.

So why do I want to minimize sound pressure? Hearing loss from exposure to high sound pressure is incremental and cumulative. The first step is to reduce wind noise in the cockpit. But the squeals coming over the air from malfunctioning radios are still pretty loud. Loud enough to be annoying and maybe loud enough to cause a tiny accumulating bit of hearing loss. There is no reason to not turn the radio down as low as feasible.

The vario can have one speaker buried anywhere. Unless you have one of those talking varios... a beep is a beep.

Thanks to all who replied, but I think the project came to an end when I came across this post on an electronics forum


"My guess is that the speaker output - terminal is not ground, but is driven to some AC voltage out of phase with the + terminal. It's how most automotive amps (and other low $ items) work to maximize power out, given a single +DC voltage supply like you'd have with a battery (vs a + and - DC voltage supply that would be made from the mains AC line) . The speaker + and - outputs should not be connected to anything other than the speaker itself."

I suspect that the the radio I have has an amplifier as described in the quote, they say not to connect the speaker -ve to a common ground.

Dual voice coil speaker is still a possibility though .

Cheers

Paul

The only solution I can come up with is to use transformer coupling with three windings - two input windings from the two sources and one output winding to the speaker. The windings could all be on one toroid. The only coupling would be magnetic. I haven't had the energy to calculate what values might work, but offer it as a conceptual solution.

Mike

On Monday, 2 March 2015 15:09:04 UTC+10, Mike the Strike wrote:
The only solution I can come up with is to use transformer coupling with three windings - two input windings from the two sources and one output winding to the speaker. The windings could all be on one toroid. The only coupling would be magnetic. I haven't had the energy to calculate what values might work, but offer it as a conceptual solution.

Mike

Interesting thought Mike, just wondering if the current in the windings of one output would not induce current in the other windings so you still would wind up with current backfeeding to the other amps.

I'll just go the conventional way for now .

Cheers

Paul

Not if it's a hybrid transformer

http://en.wikipedia.org/wiki/Hybrid_coil

I still would bet on sufficient independant speakers being the optimal
solution.

Second best is amplitude and impedance matching the vario output
into the aux audio input of the radio (with the bonus, or drawback,
that the vario output would be muted when receiving or transmitting.
No Outputting an 8 knot climb audio signal to your struggling
competitors)

Peter

At 05:38 02 March 2015, Paul B wrote:
On Monday, 2 March 2015 15:09:04 UTC+10, Mike the Strike wrote:
The only solution I can come up with is to use transformer coupling
with
=
three windings - two input windings from the two sources and one output
win=
ding to the speaker. The windings could all be on one toroid. The only
co=
upling would be magnetic. I haven't had the energy to calculate what
value=
s might work, but offer it as a conceptual solution.
=20
Mike

Interesting thought Mike, just wondering if the current in the windings
of
=
one output would not induce current in the other windings so you still
woul=
d wind up with current backfeeding to the other amps.=20

I'll just go the conventional way for now .

Cheers

Paul