Enough Power

[spacelord2002]

I am currently running a pair of Cornwalls and a pair of KG 2s. A friend of mine lent me his Heresy's to listen to as I intend on getting a pair of those too. Do I have enough power for all three? I am using an Ad Com GFA-2 with a power rating of 100 continuous watts into 8 OHM, and 150 watts into 4 OHMs. Does each pair drain juice from the amp or doesn't it matter? How does the idea work?

Thanks, Dave

[Ray Garrison]

Are you saying that you are thinking about driving all three pair of speakers from one speaker output on your Adcom?

If so, there are two different ways of hooking this up - parallel or serial. Both have advantages / disadvantages.

If you connect them in series (amp plus out to Cornwall plus, Cornwall negative to KG2 plus, KG2 negative to Heresy plus, Heresy negative to amp negative out) you should have enough power to drive them, and the amp won't be stressed because the resistance of the speaker chain will be fairly high. However, your bass response (particularly on the Cornwall) might be a bit "mushy" because the damping factor will be affected by the higher series resistance of the signal chain. Exactly how this works is a bit too complicated for a short answer here, but if you do a google search on speaker amp damping factor you should find some explinations.

If you connect them in parallel (three separate wires, one each from amp plus to each speaker's plus, and same for negative) you will really stress the output section of the amp at loud levels, as the resistance will be very, very low at some frequencies, and the amp will be dumping a ton of current into the load. The system might sound better this way, but you might break your amp.

HTH

Ray

[3dzapper]

That's a two channel amp right? If so three sets of speakers at once would be too low an impedence and could damage the amp, the speakers or both.

Rick

[3dzapper]

Ray, you snuck that post in there while Iwas figuring the impedence. You are right on the money as usual.

Rick

[spacelord2002]

Thanks for the responses, I should have elaborated better. I'm not directly running the speakers off the amp itself. I'm using the Ad Com GFS-3 speaker selector which is hooked up to the amp and is able to handle the three pairs. And it is a two channel amp.

[Guest BobG]

That Adcom switcher and most multiple speaker switch boxes have a very high power resistor to protect the amp from seeing the low net impedance of the 3 (or more) pair of speakers connected. It is an effective and low cost method of protecting the amp however it also means that the resistor itself may be receiving more than half the total power the amp puts out. As the net impedance of the combined speaker load drops, the resistor represents more than half the total load.

Overall, this approach will work, but be sure to keep the speaker switch box in a well ventilated location, especially when you run all three pair at high volume for a longer period of time such as a party.

[spacelord2002]

Thanks Bob for the feed back! It's good to have the forum to fall back on for tech. assistance.

Dave

[cdsang]

understanding ohm levls my self, it would be possible to run it all 3 over 4 ohmes. But it can be a really tricky wiring job and a real hassle. There 8 ohmes right? Wire 2 8 ohme speakers to 4 ohmes then wire the 4 ohmes to the 8 ohme aera would make 12 ohmes when wired right.Or you could wire the 2 8 ohmes speakers to 16 ohmes and wire that to the 8 speaker left to make 5.3333.... and so on ohmes. I delt alot with car audio math and someone nice enought on this forum gave me the formula for this to. I just forgot what parralled and series do the ohmes. Its been awhile, but I could find out.

CD