I would like to connect some headphones in parallel with a single
>speaker. The amplifier powering the speaker is a 110-W, Sony STR-DE997
>A/V, surround-sound receiver. The speaker has an 8-ohm impedance. The
>headphones are Sennheiser model HD 580 (open air) with a nominal
>impedance of 300 ohms and a "load rating" of 200 mW.
>
>I'm sort of guessing/figuring that a 3K-ohm resistor in series with
>the headphones ought to work. The 3K ohm resistor in parallel with the
>8-ohm speaker would yield a net resistance of about 7.9 ohms to the
>amplifier. And if power divides the same way current does, that should
>provide a maximum of about 300 mW to the headphone. There would only
>be a signal to one side of the headphone, of course. I would also put
>a headphone volume control in the cord.
>
>As anyone ever done anything like this before? Does anyone know of any
>reason it wouldn't work?
>
>---------------------------------
>
>The reason I want to do this, incidentally, is to try to clear up a
>problem that I have with hearing dialog in TV movies, etc. The
>headphone would be connected to the center speaker of my surround
>sound system. The center speaker typically carries the speech part of
>the audio, while the other speakers carry mostly the sound effects.
>The fact that I would only get sound in one ear probably wouldn't
>matter at all since one of my ears is really, really bad and the other
>one is only sort of bad.
If you are hooking up to more than one speaker, realize that the negative speaker terminals are usually not common, and cannot be connected together.
You can get a 'speaker pad' to do the level adjusting, they are available in a number of different impedences.