Running 4ohms on a 8ohm reciever?

TTerry944

Question #1: I have two 10'' EX10 Series 2 Polk Audio car subwoofers that run at 4 ohms. I have a home reciever that runs at 8 ohms. Is there anything I can buy or do that will enable me to hook up the speakers to my home reciever without blowing them?
Question#2: How do I change the Ohms on my car amp? For example, if I have them running on 2 Ohms, how do I change it to run at 4 Ohms?

sgtgto

Hi:

How do you plan on connecting two subs to your receiver? Are they powered?
Look at the documentation on your amp to see how to bridge it to the mode you want.

Gary

jcaut

If you wire the two woofers is series (connect the "+" on one to the "-" on the other, then connect your amp to the remaining two terminals) it will present an 8 ohm load to your receiver.

I'm not sure if that's what you mean.

I don't understand what you're asking on Q#2. As far as I know, on most car amps, there are no settings to change for speaker impedence. If your amp is stable when driving a 2 Ohm load, it should have no trouble with a lighter, 4 Ohm load. Power output will probably drop some. You might have more luck with that one in the car stereo forum.

[Deleted User]

Hello Terry,
Thanks for participating in the Forum. Perhaps I can offer some helpful information. Receivers that use transistors for the power section can be connected to speaker impedances from around 4 ohms to 16 ohms with no problem. Think of the receiver as if it were a water pump, producing water pressure and gallons of water per minute. This pump has connections for attaching an 8", 6" or 4" diameter water pipe. The size water pipe that gets attached to the pump will effect the capabilities of the pump. The larger the pipe the more difficult it is for the pump to produce water pressure and gallons per minute. The same thing happens when you connect a speaker to a receiver, as the impedance drops from 8 ohms to 6 ohms to 4 ohms, the level of difficulty for the receiver increases. More "water pressure" (Voltage) and more "gallons per minute" (Current) are needed at higher playing volumes.
The second consideration is the way speaker impedances change depending upon how they are attached. If we go back to the water pump comparison, if we connected two 4" diameter water pipe simultaneously to the same pump it would present the same kind of connection as a single 8" diameter pipe. With your receiver if you connect the two 4 ohm drivers in parallel to a single channel of the receiver, the receiver will function as if a 2 ohm speaker were attached. At higher playing volumes this would probably be below the capability of your receiver. However, if you connected one 4 ohm driver to the left channel and the other 4 ohm driver to the right channel since these would be two independent connections to two separate "water pumps" the receiver would function as a 4 ohm load. Most "high current" receivers can operate with a 4 ohm speaker impedance.
So, there really isn't a way to change a receiver's impedance, that is something that happens when you connect a speaker. The speaker and its characteristics determine the kind of load that the receiver "sees". The playing volumes influence the level of Voltage (pressure) and Current (gallons per minute) that comes from the receiver. If you multiply Voltage and Current together you will have Power; 5 Volts flowing at 2 Amperes equals 10 Watts of power. If the impedance drops by half, then 2.5 Volts would flow at 4 Amperes, giving the same 10 Watts. The Wattage remains the same, but the relationship between Voltage and Current changes as the load impedance changes.
I don't know if all of this helps or not, basically, if you play any sound system at fairly high volumes using a lower impedance speaker load, the device that's powering it needs to be able to produce fairly high amounts of current. For your situation, connect one driver to each audio channel and keep an eye on the volume control.
Best regards, Ken Swauger