[midnightcarving]

Hey guys, i've been dabbling in building systems for quite some time now, but most of its just cobbed together stuff, anyway, i recently obtained a nice classic pioneer sx-580 reciever, and decided it was time to upgrade everything else.

My biggest question has to do with speaker impedance, basically, what is the best, is it better higher or lower? and when wiring, are there any configurations that are better/worse than others. On the back of the reciever it says "a,b = 4 or more ohm, a + B = 8 ohm" and im not sure what they meant.

my next question has to do with tweeters, what kind would you reccomend? cuz i have some very nice polk audio speakers, but the tweeters in them are busted.

anyway, thanks for any help you can provide.

[warnerwh]

Welcome to Audiocircle. You will want to use 8 ohm speakers with that receiver although four ohm will work.  Speakers should have either dome or ribbon tweeters.  There's alot of variation in sound even within the category so you need to listen to what you can.   Cheers

[Sintz]

The impedance of speakers varies with frequency and design, so a speaker rated at 4 ohms may dip as low as 2-3 ohms or as high as 10-15 ohms, again depending on frequency.  With regard to the recommended impedance on your amplifier, it looks like your amp is rated for 4-ohm speaker loads when driving either the A or B speaker terminals. Since the amplifier is rated for about 4-ohm operation, running A+B together (two sets of speakers) would reduce the impedance of two 8-ohm speaker sets to 4 ohms (parallel configuration using Ohm's law... google "ohm's law" if you want more info on that).   or try http://www.the12volt.com/ohm/ohmslaw.asp

The vast majority of home audio speaker systems are rated between 4-8 ohms with most of those rated between 6-8 ohms.

You can get away with running two 4-ohm pairs of speakers on this amplifier (giving you a 2-ohm load, 1/2 of the rated impedance of 4 ohms), but be VERY careful in doing do. Being 'careful' includes limiting listening to low levels, for shorter periods of time, listening for ANY signs of distortion, and checking the amplifier's temperature frequently.

Again, be VERY careful doing so because you're asking your amplifier to deliver 2x the amount of current (I) every time you lower the impedance in 1/2. (P=I2R, ohm's law again). This means that the internal resistance of your output stage in the amplifier will be dissipating more heat per watt delivered to the speakers. In short, it makes the amp run hotter, with greater risk of failure.

You're best off with a higher effeciency speaker with higher impedance because you'll be able to play the music without running your amp too hot.

Hope that helps.

Welcome to the forum!

[warnerwh]

Being that is a nice receiver that's over 25 years old I'd be conservative with my speaker choice.  I have a very nice Pioneer SX 780 and have Dynaco A 25's on their way for it. At this age excess heat could cause something to fail prematurely.