On Tue, 17 May 2005 12:36:17 GMT, "Tim Martin"
wrote:

"Jim Lesurf" wrote in message
...
In article .com,
wrote:
Hi,

Can you please tell me the advantages and disadvantages of 4 ohm
compared to 8 ohm loudspeakers?

*In theory*, a 4-ohm speaker can be more efficient, but that may not
apply in practice. What *is* universally true is that, since the
'official' dB/w/m sensitivity is measured with a 2.828 vrms input - a
nominal 1 watt at 8 ohms - a 4-ohm speaker immediately gains a 3dB
hike in its spec-sheet sensitivity compared to a true 8-ohm speaker.
Some manufacturers like the look of this in the sales blurb.

Depends entirely on the speakers in question, the equipment you use them
with, and your personal tasts/circumstances.

The only general comment is that *for the same applied voltage* the 4 Ohm
ones may draw more current, and that some amplifiers may not like this.

Very few decent SS amps have a problem with a 4-ohm load. Tube amps,
of course, always have a problem, as they are rated to put out the
same power pretty much regardless of load, so you get 3dB less sound
level with a 4-ohm speaker, if you use the 4-ohm taps rather than the
8-ohm taps on the output transformer.

By the way, some manufacturers offer near-identical speakers in 4-ohm and
8-ohm versions, with otherwise similar specifications.. Does anyone know
how they do this ... is there some simple trick to it?

Different motor assemblies in the drivers, with fewer turns and/or
thicker wire on the 4-ohm units.
--

Stewart Pinkerton | Music is Art - Audio is Engineering