Newbie question.

I've been reading about speaker impedence and amp impedence and that ideally, they should match. What happens if they don't match? My speakers/amp will go up in smoke???

Should I do any calculations before getting a pair of speakers and an integrated amp?
Thanks.

??
from where did you hear that?
Ideally an amp should be a voltage source. 0 ohm output impedance. All commercial speakers are designed for this. By increasing the amps output impedance you could play with the bass tuning...

The higher the speaker impedance, the more current you need to move the speaker cones. Amplifiers' power outputs are rated by the system impedance, for instance an amplifier outputs 2 x 50 W @ 4 ohm and 2 x 38 W @ 8 ohm.

@daniel

I don't think you meant 0 ohm. Resistance/impedance value of 0 ohms would mean an infinite current at any nonzero voltage

nonono. The question was about amps output impedance, which is in the range of 0.001-0.1 ohms average with solid state amps, 0.5-5 ohms with valves. It is also known as damping factor.

an ideal (voltage) amplifier would supply infinite current to 0 ohms (short circuit), finite current to any other value.

There is seldom impedance problems with ampli/speakers. Speakers are generally 8 (common), or 4 Ohm (less common).
4 Ohm speakers makes the ampli more powerful, because it affects the polarisation of the transistors.

Impedance problems occur with non-electrodynamic speakers (electrostatic panels, for example), or maybe with audiophile valve amplis, and likely with both

This has also a downside. Cheap low quality amps may have trouble feeding to 4ohm, due to the limited capacity of the power source. This can cause overheating of the amp and less than optimal sound.

Actually, it's more the opposite. The lower the speaker impedance, the higher current requirements for the ampli.

So unless you have really really lot of money, you won't have impedance problems

@KikeG

I stand corrected. My tired brain didn't remember that impedance (Z = sqrt(R^2 + (X_l - X_c)^2))
!= resistance (R = V / I).

Sorry took me long to reply.

Actually I have a pair of Mission speakers, when I look at the back I see the following info:

Recommended amp power : 25-75 Watts
Nominal impedance : 8 Ohms

So if I get a decent amp what should I look out for?

Eg. 2x50W @ 4 ohm or 2x50W @ 8 ohm ??

Look for an amp from a good manufacturer that gives more power (watt) than your speakers in the appropiate imedance.
For example I have a 150W hooked up to 60W speakers, this way you avoid the clipping problem that some amps get when you crank them fully open + the amp will be better in control of the speakers.
A friend of mine for example has 400W (one of those ole BIG hifi amps) amp hooked up to his 80W speakers and believe me this baby "controls" the speakers.

And for a further note, Watts don't tend to mean a lot in hifi. You have Watts and sensitivity of the speakers, the capability of the amp to drive speakers, the stability of the amp, ...
As you can see alot of factors come into play.

I don't think you have to go that far, unless you have very unsensitive speakers, or listen at very high levels, or use a crappy amplifier.

If I have a pair of 30W spkrs, is it

30 x 2 = 60W OR just minimum 30W to drive the speakers?

Maybe it look's like a lot more but it's well known that it's easier, for the unknowing customer, to damage speakers with an amplifier that clips than with one that has breathing room.
Mine was bought on the grow and my current speakers are, at 86db/spl, a bit unsensitive .

Just buy active Genelec speakers and you don't have to worry about them stupid amps

www.genelec.com

And if you actually care about quality and have a lot of money buy a dynaudio-acoustics BM15A active near/mid-field speakers. Or BM6.
I'd still buy a passive BM15 and a good amlifier. (the BM15A have more power and reach a low frequency of 30hz though, which is awsome, passive reach 43hz)

sensitive speakers are awesome *thinking of Cabasse (w00t)* ...okok, a bit too much of a generalization


talking of low impedance, i got my speakers for $700 the pair (reduced from $3200 though), and they are quite a pain for amps, ditching as low as 2 Ohms.. i'm not sure which driver it is though, wasn't able to find the impedance graph anywhere on the net. it's probably the magnetostatic tweeter. sensitivity is 90 db spl @ 1W / 1M iirc.

btw, 150W amp vs speakers handling 60W? that's decent i'd say. i mean, turning up from 60 to 120 watts gives you like what? 3db of spl? (too lazy to look it up)

seeing as how you're from Toronto, why don't you head downtown to Bay Bloor Radio? Rated as one of the top 5 hifi stores in the world.

I bought a surround sound system from them about a month ago (their Challenge system: Energy speakers, Denon amp, Panasonic DVD) ... they love Energy speakers over there, along with Mission also. The salespeople are incredibly friendly, and they're not predators like at FutureShop. Go tell them what you have, and they will match up a nice amp for you.

Actually, they're selling a Yamaha amp + 5-disc changer with a pair of Mission speakers right now for $799, and it will blow the socks off of anything else priced below $1000. Great deal. These guys don't rip you off. If you have the same speakers they are selling, the best thing to do would probably be to buy the amp they're selling in that package. They pay a lot of attention to price and detail, and are very competitive quality-wise. You'd be hard-pressed to find something better. They take your price limitations into consideration also; they don't pressure you into making the big sale.

Amps have no such impedance as 8 or 4 ohm. Any amp can handle both. The writings vary, some recommend 8 ohm, some above 4, some 4 to 16, but they are basically all the same and support both 4 and 8.
It is safer to assume that any amp support 4 and 8 ohm than to trust the load impedance as advertised in the technical specs.

Power of speakers is meaningless. Some little speakers will be rated 300 W while a 0.5 W sine at 10 Hz is enough to tear off the woofer.
Often, a "musical power" is given. It is the highest power that can be fed into the speakers without destroying them. Way above the maximum power for hifi listening.

Yours seem more serious : they advise a power for the ampli.
In this case, don't buy an ampli much more powerful, it may be a waste of money.