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Mixing Speaker Impedance?

I am considering purchasing either an onkyo pa-mc5501 or integra dta 70.1.

My question is that both of these power amps have a 4/6 impendance switch on the back of them. How will this effect my speaker setup if I am using speakers that have mixed ohms? My front L/R monitor audio RX8s are 4 ohms, my center gxc150 is 8 ohms, and my surrounds gx1 are 6 ohms.

Thanks,

in advance for any advice.
azag
azag OP
2 posts
 
Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?
zd542
5,339 posts
 
"08-28-13: Azag
Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?"

It shouldn't because you will be setting the volume levels for each speaker when you do the setup with your preamp. The only other question is to weather the amp has enough power do drive the speakers. MA is not a difficult speaker to drive. I can't imagine either of your 2 choices not working.
tls49's avatar
tls49
1,351 posts
 

The switch is for the amps protection so that it doesn’t get too hot.
Wont setting the amp to 4 ohms limit speakers with 8 ohm requirements?
This setting limits the amp, since it alters the operation of the amp to run cooler, that typically results in less power output capability. The 4 ohm speaker requires the most power, with the 6 ohm being less, and the 8 ohm less than that. Also, the size room and how loud you play the system are factors. Obviously, louder volume and larger rooms require more power. In a way this may not make sense, but as I said, it is to protect the amp, by limiting its output to stay cooler. Ideally it is best use a 4 ohm rated amp with 4 ohm speakers.

Just curious as to the choice of a 9 channel amp for 5 speakers, if you don’t need the extra channels, why not get a 4 ohm rated 5 channel amp?
zd542
5,339 posts
 
If you have extra channels, try doing a vertical biamp. It may sound a lot better.
tls49's avatar
tls49
1,351 posts
 
Sorry Zd, a vertical bi-amp means using one stereo amp per speaker, therefore L & R are totally independent. Horizontal bi-amp is a one amp for low input of both speakers, and another amp for the high input of both speakers. We will probably need to call this scenario a horizontal bi-amp since all channels are in the same chassis.

The amps rated power is 150wpc with 2 channels driven, and HT Review’s measured power on the amp is 119wpc with 5 channels driven. The OP said he was considering the purchase of this amp, so IMHO, I would take that amount, plus the additional for extra interconnects and cables needed to bi-amp, and purchase a good 4 ohm rated 5 channel amp with more power. The RX8’s will perform so much better, and the center and surrounds will benefit also, especially, if he is in a large room.
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