4ohm speaker to 8ohm amplifier

[saketkoria]

is it possible to conect a 4ohm speaker directly amplifier wch mentions on back panel 8ohm?
in case if its possible, will der be a quality loss?

 

[rnatalli]

It's possible. It really depends on what receiver we're talking about. It's not a question of quality, rather whether the amp section can handle the load. What receiver do you have and what's the sensitivity of your speakers?

 

[Midcow2]

larger receivers can usually handle

is it possible to conect a 4ohm speaker directly amplifier wch mentions on back panel 8ohm?
in case if its possible, will der be a quality loss?

In simplest terms power is voltage times current. Current is also voltage divided by resistance.

So 100watts RMS into 8 ohms would be 100=V^2/8 so V would be ~ 28.28volts. The current is 28.28/8=3.535 amperes

Assuming constant voltage then (28.28)^2/4 would need 200watts RMS and double the Current to 7.07. You would have a problem is the AVr is limited to 5 amperes.

Asuming constant power 100RMS you could only drive the voltage to 20 volts.

Bottom line with 4 ohms you either need a bigger receiver or you run at lower volumes.

Most AVRs have protective circuitry to prevent oveload due to low ohm speakers increasing the load. The protective circuitry typically powers-off which is better than frying the output power transistors.

 

[saketkoria]

It's possible. It really depends on what receiver we're talking about. It's not a question of quality, rather whether the amp section can handle the load. What receiver do you have and what's the sensitivity of your speakers?

hi thanks for replying,
the amp would b harmon kardon avr 147
and speakers are jbl scs 140

 

[Midcow2]

You need more power

hi thanks for replying,
the amp would b harmon kardon avr 147
and speakers are jbl scs 140

The AVR is 50RMS into 2 channel or 40RMS into 5 pretty low power.

The sensitivity measurement is how much power it takes to drive a speaker to produce the same SPL (Sound Pressure Level). Basically all speakers with a sensitivity of 90dB will require the same power.

However 86dB is a less than average efficiency speaker and but will require a reasonable sized amplifier- 100-125 rms per channel.

Depending on the specifics and size of the room a decent high end AVR should be sufficient. See the link for calculating the actual power needed.
http://myhometheater.homestead.com/splcalculator.html

 

[rnatalli]

I was really hoping your speakers had a 90db+ efficiency. I don't think I'd hook up those speakers to that HK receiver unless you were listening at low to moderate volume.

 

[PENG]

I was really hoping your speakers had a 90db+ efficiency. I don't think I'd hook up those speakers to that HK receiver unless you were listening at low to moderate volume.

Those speakers are little and weigh only 1.1 lb each. So I don't think they can play very loud regardless. The recommended power amplifier range is 10 to 50W rms. While the entry level HK will struggle, something like a RX-V663 will have no problem driving those little ones to destruction before the receiver clips. Again, I agree 86 dB 2.83V 1 meter means the speakers are relatively hungry but they are also not designed to play very loud judging from the size, weight and the recommended maximum power amplifier output.

 

[Seth=L]

I would upgrade the speakers before the receiver, those speakers won't sound any better or louder with a more powerful receiver.

 

[dorokusai]

That's not a hard loudspeaker to drive, even at 4ohms. The HK is more than enough power for that loudspeaker. You could run them off a tube flea amplifier. We are talking about that sub/sat system right?

Mark
Polk Audio CS