Ohms (no, i'm not meditating, though maybe that would help)

[Ghoulish Delight]

Amp and speaker impedance. Drives me bonkers. I get confused enough without the added obfuscation of marketing numbers vs. reality.

So I'll try to boil this down to a simple yes or no question.

For an amp with the following specs:

Power: 165X5 @3ohm
Power consumption: 165W

Can I swap out a 3ohm speaker for an 8ohm? Do I need to know anything more about the 8ohm speaker and/or the amp it's currently connected to before answering that question? If I use 8Ohm speakers on 2 of the channels, would I then be risking over-powering the 3ohm speakers on the other channels?

argh, this sh*t gives me a headache.

[Cadaverous Pallor]

Don't know if this matters, but our speakers say 140W max input power.

[Ghoulish Delight]

Max won't be an issue. The question (if my vague understanding of this crap is right) is whether our speakers would be under powered.

[DreadPirateRoberts]

Ohm's law: V=I*R V=voltage, I=current, R=resistance
Power: P=I*V I=current, V=voltage

put it together

P=I*(I*R)= I*I*R

for your current setup, P=165, R=3 ohms

If you replace the 3 ohm speaker with 8 ohms, there will less current used to generate the 165 watts, so the speakers should not sound as loud. It should not hurt anything.

[CoasterMatt]

What amp do you have that's rated at 3ohm?

(I've seen 2, 4 & 8 ohm, but not 3)

[Ghoulish Delight]

No amp yet. I'm looking at the handful of bluray home-theater-in-a-box options out there* pretty much all of which are marketed as 3ohm. From what I've read, that probably isn't a real number and is a bit of marketing fudge. *shrug* who knows.

Of course, the other question is connectivity. All of these home theater systems have nifty little plugs at the end of the speaker wires that easily pop into the receiver. Our old receiver just has a spring loaded connector that I stick a bare wire into. It looks to me like I can just splice the new connector onto the old speaker wire, yes?



* I know, not the highest quality choice, but it's the only way the upgrade to bluray AND surround sound will fit in the budget. Plus, we're no audio-philes. And we don't have a large space to fill. So I'm not overly concerned.

[Capt Jack]

Я не знаю, что ад язык, который вы говорите

[Ghoulish Delight]

Pondering a new strategy. Surround sound in our little livingroom is probably overkill anyway. But a receiver upgrade is still in order (our 17 year old Kenwood is still a fine component, but it's not designed to make sense of the way audio is mixed for a digital world).

So instead of the all-in-one solution, I can get a standalone receiver that will properly drive the current speakers, and a standalone blu-ray player for around the cost (if not less) of the all-in-one. Then, when we do move somewhere where a full 5.1 solution is more necessary, all we'll need to do is add a few speakers.

[Alex]

Originally Posted by Capt Jack

Я не знаю, что ад язык, который вы говорите

Монгольский

[Kevy Baby]

The three ohm thing sounds weird to me too. But apparently

As DPR said, replacing a 3Ω speaker with an 8Ω should not present a problem; it actually lightens the working load on the amplifier. I am not sure if this is what DPR was saying, but with everything else being equal, you will not get the same sound pressure levels (SPLs) with an 8Ω speaker as you would with a 3Ω speaker on a 3Ω amplifier. Amplifiers double their output (in wattage) at half the Ω load: an amp rated at 100 watts @ 8 Ω will output 200 watts with a 4Ω load. Your 3Ω amp power output of 165 watts per channel would only output 82.5 watts at 6Ω: I don't remember the calculation exactly, so I can't tell you what the 8Ω output would be. But, as you mentioned about the marketing hype, a lot depends on the TRUE specifications.

And if you want to get real geeky about it, if you run two speakers in parallel off of one channel, that "sort of" cuts the collective Ω rating in half: two 8Ω speakers connected in parallel creates a 4Ω load on the amp. I say "sort of" because the correct calculation is "the reciprocal of the sum of the reciprocals of the speakers":

1/8 + 1/8 = 1/4: two 8Ω speakers in parallel gives a 4Ω load.

The reason this formula is used is for when you have different rated speakers. If you ran an 8Ω speaker and a 3Ω speaker in parallel:

1/8 + 1/3 = 11/24: a 3Ω and an 8 Ω in parallel gives an approximately 2.18Ω load.

OK: I've gone way to far for this discussion...