High current or normal?

 

Bronze Member
Username: Xxraiderxx

1, Ga Us

Post Number: 23
Registered: May-06
what is the diffrence cuz i wanna get this hardon kardon but it says its 50watts per channel

and the otherones say like 110watts per channel
which ones are better & yes im a noob
 

Gold Member
Username: Kano

BC Canada

Post Number: 1009
Registered: Oct-04
Most receivers fudge their numbers to market their receivers. Harman Kardon does not, 50 watts is the minimum the unit will deliver driving a full load across all channels. If you look at some manufacturer's product line, you will see every receiver from their $200 model to their $2000 model is 100W/C. Which ones really are? When one weighs 20lbs, and the other 60lbs, it is easy to tell which has the power supply and heat sinks to deliver the most power.
 

Gold Member
Username: Petergalbraith

Rimouski, Quebec Canada

Post Number: 1555
Registered: Feb-04
"High current" means that the receiver can handle a more difficult load (lower impedence) such as speakers rated at a nominal 4-ohms (instead of 8 ohms), or with low dips at certain frequencies.

It's a good thing.
 

Bronze Member
Username: Xxraiderxx

1, Ga Us

Post Number: 24
Registered: May-06
OK CUZ IM NEW TO THIS I DONT KNOW WHAT THE F$%@ IS WHAT THANKS
 

Gold Member
Username: Frank_abela

Berkshire UK

Post Number: 1421
Registered: Sep-04
Raider,

Being new to this does not give you the right to go around yelling at people...it's counter-productive in the long run because people will stop answering you.

Peter is quite correct. The point he was making is that if a speaker is rated with a lower impedance, then it requires more current to drive it. So typically speakers come in three main guises, 4-ohm, 6-ohm and 8-ohm. An 8 ohm speaker needs half the current of a 4-ohm speaker and a 6-ohm speaker is somewhere in between.

There is also an efficiency rating which tells you how much sound you get from a speaker for 1 watt of power at a distance of 1 meter from the speaker. The average efficiency speaker is considered to be one that produces 87db/w/m. However, this depends a bit on the impedance again because if it's a 4-ohm speaker it's still going to need twice the current of an 8-ohm speaker. The average is considered to be an 8-ohm speaker. So both impedance and efficiency should be considered together.

Now I don't want to confuse you, but here's the thing. The impedance value of a speaker is actually a nominal value. It's an average, not an absolute. The impedance of a speaker varies considerably with the frequency of the signal being fed into it. Typically a 4 ohm speaker will vary between 3 ohms and maybe 30 ohms. An 8 ohm speaker won't drop below 5-ohms but again, it could go up to 100-ohms. The really nasty speakers drop to 1-ohm. They're nasty because at that frequency the amp has to pump 8 times the average amount of current into the speaker than usual.

Now an amplifier has to get this current energy from somewhere, and this is why the power supply is so important. The power supply is most often a high power transformer which can feed energy into some storage capacitors. The capacitors store the energy, so when the speaker impedance suddenly drops to an ohm, the amp literally dumps the energy in those capacitors into the speaker. This has all sorts of consequences in terms of dynamic headroom, control etc. and how fast the amp does it has a direct consequence on how quickly it can replenish its reserves. If there isn't much in reserve, it can't dump much current.

So you could get an amplifier which is only 50w/ch total, but if it has big reserves, it'll be able to dump current into speakers and seem like a more powerful amp than another 70w/ch unit. Power supplies are therefore the most important part of a power amplifier.

The power supply I described above is called a linear power supply. There is another type of power supply which is becoming more common in amplifiers which is the switched mode power supply. This is the supply of choice in computers. For a given rating the SMPS is smaller, lighter and cheaper to make. The SMPS switches at very high speed (100khz or more is usual nowadays) and remains cool so it has many applications to which linear supplies aren't so adapted.

I hope this helps a bit.

Regards,
Frank.
 

New member
Username: Sethe123

Post Number: 1
Registered: Jun-06
Please Help, lost and confused. I have a 10in 1400 watt subwoofer, heres the kicker-its a 12ohm. Is there any way to increase the resistance for a car amp to be able to push more current through or does this matter. Is there an adapter? thanks for any suggestions.
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