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Speaker Asylum General speaker questions for audio and home theater. |
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Speaker Asylum General speaker questions for audio and home theater. |
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In Reply to: Re: Bi-amping and Speaker Efficiency posted by Bud on April 11, 2007 at 13:44:03:
With a speaker level-cross over, both amplifiers have the same input and output signals.Cross-over circuit impedance increases as you move farther outside the pass-band (with increasing frequency for low-pass filters on the bass drivers, and decreasing frequency for high-pass filters on the tweeters). Assuming a purely resistive load (which a speaker isn't), current = voltage/resistance, so the amplifier's current and waste heat will be lower for signals outside its passband. The tweeter amp voltage rails will sag a little less so it'll clip a little later but this won't be noticeable.
Using speaker level cross-overs if you want to be able to put equal power into woofers and tweeters of the same impedance (music doesn't have a power spectrum like this but it makes the math easy), you need twice the voltage which implies an amplifer that can deliver 4X the power needed for each driver. IOW, to get 100W + 100W you'd need a 400W amplifier. Since music favors lower frequencies, it's more like 65W + 35W with line level cross overs match the output of a single 200W amplifier with speaker level cross-overs although it gets more interesting.
You can exploit drivers with radically different sensitivities. For example, the Orion has an ear height tweeter arround 88dB/2.83V/1 meter and pair of floor-height sub woofers which exceed 100dB/2.83V/1 meter without padding the higher sensitivity driers down. To reach the same output levels with a passive cross-over that you have with the active setup and bass amp that delivers 100W into 8 Ohms you'd need an amplifier rated at over 1600W.Since the power spectrum of music favors low frequencies (down to 40Hz) it doesn't matter that the tweeter can't reach the same output levels as the bass drivers.
Rather than padding a single driver down to match its output at the frequencies where it's least sensitive (say due to baffle step), line level cross-overs can be tailored to increase amplifier output only where needed.
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- Re: Bi-amping and Speaker Efficiency - Drew Eckhardt 16:31:37 04/12/07 (0)
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