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Old 8th January 2006, 08:01 PM   #11
EC8010 is offline EC8010  United Kingdom
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Douglas Self shows in his "Power Amplifier Handbook" that for a typical bipolar transistor power amplifier, distortion driving a 4 Ohm load is higher than driving an 8 Ohm load. Using his argument, a 16 Ohm load would further reduce distortion (it's all about current). However, transistor amplifiers are voltage sources, so if a loudspeaker manufacturer makes their loudspeaker 4 Ohm rather than 8 Ohm they gain 3dB of apparent sensitivity. That's why most modern loudspeakers are 4 Ohm. Conversely, the 11 Ohm LS3/5a loses out even further...

If we used 16 Ohm loudspeakers, we could get away with thinner loudspeaker cables.

As previously mentioned, valve OTLs have a heart attack when faced with loads < 16 Ohm.

Valve amplifiers with output transformers don't really mind whether it's 4 Ohm, 8 Ohm or 16 Ohm (provided their output transformer can be configured correctly).
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Old 9th January 2006, 06:55 AM   #12
rjb is offline rjb  New Zealand
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Scottmoose

That figure you quote for a Phillips speaker is not far out from memory. They called it Hi-Z, made a number of different driver sizes, and used it in mains transformerless valved amplifiers and TV's. Lethal items that would kill any unwary serviceman. Valve filaments were in series, and the mains directly rectified. The chassis had to be totally insulated to protect users, but this was poorly done, and any cabinet damage could turn them into a death trap.
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Old 9th January 2006, 08:44 AM   #13
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Shocking...

I bet the required number of windings in the driver made them nice and reliable too...
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Old 9th January 2006, 10:25 AM   #14
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Quote:
Originally posted by EC8010
That's why most modern loudspeakers are 4 Ohm.
Most modern speakers are 8 ohm, 4 ohm are pretty rare (although continental manufacturers tended to use 4 ohms), except for in-car speakers where you have a lack of voltage and 4 ohm is the norm.

Historically, in the valve days, most speakers were 16 ohm.
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Old 9th January 2006, 11:19 AM   #15
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Depending on the manufacturer they can be 4 ohm, 6 ohm, or 8 ohm for home usage products. Most common.

Commercial applications can be 8 or 16 ohm as it is common to have either 8 or 16 ohm diaphrams for high frequency horns or a choice of 8 or 16 ohm low frequency drivers.
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Old 9th January 2006, 02:06 PM   #16
jeremym is offline jeremym  Canada
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The drivers in my TV are marked 32 ohms, I was surprised by this.
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Old 9th January 2006, 02:27 PM   #17
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The drivers in my TV are marked 32 ohms, I was surprised by this.
I see the occasional 64 ohm speakers in TV's as well.
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