Impedance supplementation

[PhoenixFL]

Ok, 8 ohm + 80hm = 4 Ohm,
and 8 ohm > 8 ohm = 16 ohm. If I ran two 8 ohm cabinets in parallel, that would give me 4 ohms. But I need to be using 8 ohms I think (although my amp should run 4 ohm as well I dont want to risk it. . .) Is there any circuit I can inside the cabs to allow me to use one cab at 8 ohms or two cabs at 8 ohms? Or should I just risk plugging them both in parallel and give myself a 4 ohm load. The chip I'm building into the amp is a TDA7294V Will that run two parallel cabs fine? It's rated on the data sheet as 100w 4/8 ohms.

[jomor]

The answer is yes and no. 8 // 8 --> 4 ohm , but that's just the nominal value.. Impedance varies with frequency, you have to study the impedance graphs of your speakers (find them from the manufacturer, or measure them) to see the lowest value of the parallel combination. For example your speakers could have 5 ohm impedance at 300Hz, which means 2.5 Ohm @ 300Hz if you have two in parallel. Since the chip's constructor gives 4ohm load power specs, it probably can work with a slightly smaller load too, but why push it to the limits? From what i can see, the TDA7294 costs $7, so why not building 4 channels instead of two ? You 'll have better overall performance and you ll be playing it the safe way. Just a thought.

[Bill Fitzpatrick]

You can include the resistance of inductors and wiring in your impedance calculations.