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Could I cheat the James Randi speaker wire challenge with ultra high impedance?
sfs1:
I understand (understand might be an overstatement) that in headphone amplifiers, you want to have a ratio of output impedance to headphone impedance of about 8:1, and that a low ratio will change the frequency response. Presumably the same is true for amplifiers and speakers. So I had this thought that if I used an ultra high impedance cable to connect the speakers to the amp, and it changes the frequency response, I would be able to reliably tell it apart from the coat hanger and claim the prize.
I guess I'm not sure if the impedances just add up in the way I'm imagining, i.e. if a 10Ω output impedance amp with 450Ω impedance cable looks the same as a 460Ω output impedance amp. Also, if the idea could work, how much of an impedance would you need to get a noticeable change.
exe:
--- Quote from: sfs1 on March 08, 2021, 10:26:47 am ---you want to have a ratio of output impedance to headphone impedance of about 8:1
--- End quote ---
Why?
I'd think the smallest output impedance is the best. Change my mind :)
sfs1:
Ugh I meant to say ratio of headphone impedance to output impedance of 8:1 :-[
exe:
Well, the statement "if a 10Ω output impedance amp with 450Ω impedance cable looks the same as a 460Ω output impedance amp." looks mostly correcy, except for the part that impedance is a complex number. So, this holds true for resistive impedances. If this is what you want, then you can use a low-impedance cable and add a 450 Ohm resistor with it.
If you want a cable with 450 Ohm characteristic impedance (in the same way as, say, 50 Ohm coax), then it will probably not work because the "apparent" cable impedance is only "valid" at high frequencies. At sound frequencies you'd need many kilometers of wire, the length should be comparable to the wavelength. Like, hundreds of kilometers (but then it will have huge losses). Otherwise it will look just like a small-walue resistor.
PS I googled what "James Randi speaker wire" challenge is. I'm not sure what you want to achieve here. For sure you can distinguish a coat hanger and a shielded cable. Just use a siggen and oscilloscope, or something. I think what he asks for is to prove that an expensive cable is better than a hanger, that's different.
sfs1:
Right, the challenge is to be able to detect your supposedly better cable. The cheat would be to design a cable that completely messes up the sound and so you can reliably distinguish it just by listening. If anyone asks you can say it sounds "warm" or "musical". :D
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