Can a 8ohms amp drive a 4ohms speakers?

[Calvin Tan]

I'm having this Onkyo TX-DS838 AV amp with 100watts RMS per channel at 8 ohms at Stereo mode and 90watts RMS per channel at 8 ohms at Surround mode. And I'm planning to buy a pair of Dynaudio Audiance 52. The problem is they are 150 watts and 4 ohms impedence. Can my current Onkyo amp drive the Dynaudio Audiance 52 - 4 ohms impedence speakers?

Thanks

[Woochifer]

A few misnomers you have to get rid of ...

First off, your receiver's output is rated at 8 ohms because that's the most commonly used impedance when testing the output. The impedance is not caused by the amp itself, it's in the speaker (and to some degree in the cable as well, but that doesn't come into play unless you go for very long cable runs). A 4 ohm load simply means that there is less resistance in the output connection. This means that it's easier to draw a high amount of wattage output, and it also makes it easier to overwork the power supply in the amp.

Also, that rating on your speaker refers to the MAXIMUM wattage that it can safely handle. It DOES NOT refer to the minimum wattage needed to drive them. In most cases, you'll get up to fairly high normal listening levels with less than ONE watt of output. It's really the peak demands that determine whether or not your receiver/speaker match is right. Another thing to keep in mind is that the impedance rating on those speakers is the nominal impedance, and it can vary a lot throughout the frequency range. The type of load that it puts on your amp will vary depending on the material that you play.

The thing to keep in mind with using low impedance speakers like Dynaudios is that most home theater receivers can drive 4 ohm speakers without shutting down, but only one pair of them at a time. If you plan to eventually complete a matched multichannel speaker set, you might not be able to go with a full 5.1 Dynaudio speaker set unless you get an outboard amp.

[62ssw]

My monitor audio s10's show a nominal impedance of 6 Ohms, now I can switch my receiver to either 4 or 8 Ohms. Which would be optimal?

A few misnomers you have to get rid of ...

First off, your receiver's output is rated at 8 ohms because that's the most commonly used impedance when testing the output. The impedance is not caused by the amp itself, it's in the speaker (and to some degree in the cable as well, but that doesn't come into play unless you go for very long cable runs). A 4 ohm load simply means that there is less resistance in the output connection. This means that it's easier to draw a high amount of wattage output, and it also makes it easier to overwork the power supply in the amp.

Also, that rating on your speaker refers to the MAXIMUM wattage that it can safely handle. It DOES NOT refer to the minimum wattage needed to drive them. In most cases, you'll get up to fairly high normal listening levels with less than ONE watt of output. It's really the peak demands that determine whether or not your receiver/speaker match is right. Another thing to keep in mind is that the impedance rating on those speakers is the nominal impedance, and it can vary a lot throughout the frequency range. The type of load that it puts on your amp will vary depending on the material that you play.

The thing to keep in mind with using low impedance speakers like Dynaudios is that most home theater receivers can drive 4 ohm speakers without shutting down, but only one pair of them at a time. If you plan to eventually complete a matched multichannel speaker set, you might not be able to go with a full 5.1 Dynaudio speaker set unless you get an outboard amp.

[Woochifer]

My monitor audio s10's show a nominal impedance of 6 Ohms, now I can switch my receiver to either 4 or 8 Ohms. Which would be optimal?

That impedance switch on your receiver reduces the voltage output to the power supply as a safeguard against overloading with low impedance speakers. Not sure, but I think another reason it's there is because UL now requires one for certification. For a 6 ohm speaker, you should probably use the 4 ohm position, but the 8 ohm position probably would work fine as well so long as you don't drive the speakers too hard.

[vr6ofpain]

A few misnomers you have to get rid of ...
Also, that rating on your speaker refers to the MAXIMUM wattage that it can safely handle. It DOES NOT refer to the minimum wattage needed to drive them. In most cases, you'll get up to fairly high normal listening levels with less than ONE watt of output.

It is amazing how many people do not know this. My parents really old Fisher Integrated amp actually had levels on it, and honestly you could crank that thing pretty loud and it would still usually be at only a fraction of 1 watt(it was a 35watt per channel integrated).

That impedance switch on your receiver reduces the voltage output to the power supply as a safeguard against overloading with low impedance speakers. Not sure, but I think another reason it's there is because UL now requires one for certification. For a 6 ohm speaker, you should probably use the 4 ohm position, but the 8 ohm position probably would work fine as well so long as you don't drive the speakers too hard.

I always wondered what the purpose of that switch was, because on my old Kenwood, I was running 4 ohm MB Quarts and I couldn't hear a difference in sound between the two positions. You can learn new things every day, thanks for the info!