Easy Impedance Matching

Within the last two weeks, I have received several calls from prospective customers all looking for the proper way to connect more than one pair of speakers to a stereo amplifier and a single volume controller. Low-budget audio distribution, yes, I thought, but far better than having no audio at all, right?  Hmmm… I wonder if  all those calls were from the same person? Nonetheless, the easiest way to connect multiple speakers to a single amp/volume controller is through the use of Buffalo Electronics’ impedance matching volume control, BEVC5A.

This device has built-in impedance matching, and it does it automatically. There’s no need for  jumpers that could fall off or get lost. No need to figure out (meaning no math required!) what the total impedance is of the speakers that are connected in parallel.  No thinking required, really, just hook up no more than four eight ohm pairs of speakers to the BEVC5A, and you are good to go.  For you with inquiring minds out there, I’ll let you in on how the volume controller does its thing. The volume controller is preset to multiply the impedance by a factor of four. If you have four pairs of eight ohm speakers in parallel, the total impedance is two ohms (click here for homework). Multiply that by four, and voila! your amplifier is now fat, dumb, and happy seeing an eight ohm load even with four pairs of speakers hanging off of it.

Amplifiers perform at their best when properly matched to the designed load, which is typically eight ohms. Loads greater than eight ohms are no problem for the amp for the numerically higher impedance presents a greater resistance to current flow. When you go below eight ohms, and approach, but never reach zero (decaying exponential ), a numerically lower impedance in this case, the load begins to look like a short circuit and short circuits let gobs of current flow through it for a short period of time for the load appears to have no resistance at all.  Amplifiers cannot supply an infinite amount of current, and so the amp shuts down due to the overloaded condition.  Think of a tripped electrical circuit breaker, or blown fuse, when a circuit’s capacity is overloaded.

OK, I mentioned earlier that no thinking was required to use this volume controller so let’s now end this topic with this lesson learned: Don’t exceed four eight ohm speakers when using the BEVC5A. 

Nutznboltz, Out!