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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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Propeller Head Plaza Technical and scientific discussion of amps, cables and other topics. |
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In Reply to: eliminating low frequenies impact on ohm/load handling of amp? posted by Phil0618 on August 16, 2004 at 08:50:21:
Assuming multiple pairs of speakers are used in parralel, bringing the load below the rated impedance of the amplifier, and one (for whatever reason) desires to not correct the impedance match by using a series parralel wiring scheme... Well, you place your bets, you take your chances. More speakers make for more efficiency, more efficiency requires less watts, so with most transistor amps, as long as you are not using more power overall than you were before you added all the rest of those speakers, and no more power than the output transistors are rated for, no problem. The problem comes as the party progresses and one of the guests (or yourself-oops, show off) turn it up- the outputs can deliver more juice than they were rated for, potentially frying themselves, or clipping ( and chewing up the speakers) at a lower point on the volume knob than they would at the proper load impedance. Not a good way to turn off the audio. On to protecting those speakers, often far more expensive, and harder to replace than the power amp.
Fuses are a great device to save picture tubes, power supplies, and houses from being burned down.
In my experience, fuses are useless for speaker protection in a Hi-Fi set up, but can be useful for protecting Hi-Fi speakers from idiot intervention.
A fuse is a short piece of wire that heats up and burns open curcuit. A speaker has a long piece of wire in the voice coil, (although some tweeters have less than a yard of hair thin wire, and a 3 amp fuse can toast 'em easy as pie) and reacts to heating slower than a fast-blow fuse. I will assume here that no one will argue slow-blow fuses to protect a speaker. A fast blow fuse capable of staying intact on the large transients that a voice coil can sustain without toasting can allow near the same average level through, letting it burn. The choice becomes a low amperage fuse below the speaker's rms power rating which will blow on peaks that the speaker can easily handle, or a higher amperage fuse that that will allow the voice coil to reproduce the peaks, but still burn up on compressed average signal.
My experience with fuses was in sound reinforcement, mostly on mid or high drivers, and they popped frequently on peaks, but when they were needed, when a Phase Linear power amp went DC, for instance, the HF drivers roasted leaving an intact fuse.
After seeing all that, relagated them to the equivalant of putting a 55 mph govener on a sports car, it will keep kids from exessive speed, but won't keep them from crashing.
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Follow Ups
- Flames, Amps, Fuses... - weltersys 01:09:43 09/29/04 (0)
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