looking to upgrade the system in my recently purchased b5 a4. It came with the bose "premium" sound package however I am not impressed with the quality and am looking to upgrade my system. For now, I wanted to buy speakers and get amps subs and receiver later. I read somewhere that the bose amp only puts out 2ohms of impedance, is this going to be a problem if i buy aftermarket speakers that are 4ohm??

thanks in advance

 

Get a multimeter from home depot for like $20 and test the resistance of a speaker (pull it, disconnect, and test the resistance of the two terminals). It'll save you a headache down the line. Wattage is halved when resistance doubles, so it wont hurt it to run higher impedance, it will just be significantly quieter. Running lower impedance than the amp/headunit can handle is a recipe for disaster, or it simply won't work depending on the level of sophistication of the amp/headunit.

I have also heard that the bose system is a funky impedance. I also agree that the bose system is below satisfactory.

 

The ohms of impedance on amps are just power ratings, and have nothing to do with what an "amp" can do. An amp will always have a certain voltage, but that's rarely advertised. However, the ohms of your speaker will decrease the power that pumps out your speaker.

EDIT: oh, should have read the above post before.

Geek version w/ calculations:

http://www.kpsec.freeuk.com/ohmslaw.htm

Oh, the idea is the greater the impedance, the greater control, the better sound quality, as well as less likely to blow out your speakers. We won't get into amp class and "cleanliness".

If you want to do a system right (even one that doesn't cost much). Pick out your speakers, head unit, and subs, then buy the amp you need to run them. Make sure your head unit has enough preouts and voltage to handle all the amps you want.

Good luck!

 

Amps times Volts equals Watts
Volts divided by Watts equals Amps
Amps divided by Watts equals Volts

Voltage is "potential", think PSI in tires, except electrons instead of air and circuits instead of tires. Amperage is current, how *much* is flowing. 1 Ampere is 1 Coulomb flowing past a given point in the period of one second. 1 Coulomb is 6.24150948×10^18 electrons, roughly.

The ohms have no impact on what the amplifier *can* deliver, however given a certain impedance, it will effect how much it *will* deliver. Given one amplifier putting out 12V signal (forgetting stability at low impedance for a second), a speaker connected to it at 1 ohm will let twice as much current (amperage) pass through it as a 2 ohm speaker would connected in the same way. Using the 1 ohm speaker for reference here for amperes (X), the 1 ohm speaker is getting 12V 1(X) amperes. The 2 ohm is getting 12V .5(X) amperes. For sake of example, a 4 ohm speaker would get 12V .25(X) amperes.

Hopefully I haven't confused the situation more, I was hoping to help explain what impact ohms would have. Also, *PLEASE* if you find the ohms of those Bose speakers in your travels, please post back with that data. As with most calculations, real-world data will vary, wildly. Some Amplifiers won't just "double" the wattage at lower impedance (ohms), though the output will still be significantly higher, and somewhat close to double. It all has to do with efficiency, which is beyond the scope of this little ditty.