Quick question about receivers

[Profoundsoup]

For example if the says receiver can play up to 6 ohm speakers does that mean it can play anything below that easily like a 4 ohm speaker? If it doesnt work this way, can I play 4 ohm speakers on a 6 ohm receiver? 

[Moonzy]

6 minutes ago, Profoundsoup said:

For example if the says receiver can play up to 6 ohm speakers does that mean it can play anything below that easily like a 4 ohm speaker?

i think its the other way around lol

if it can play 4 ohm, it can play 8ohm? lol

 

not an audio person here

[Profoundsoup]

1 minute ago, Moonzy said:

i think its the other way around lol

if it can play 4 ohm, it can play 8ohm? lol

 

not an audio person here

Well In the headphone world higher ohm means harder to drive. Like 800 ohm headphones require quite a bit of power. 

[Rmusic10891]

From a source in SSL's Blog. Many times amplifiers will tell you how much power they deliver at a given impedance.

 

"Why are ohms important?
Two reasons:
(1) If you connect your amplifier to the wrong speaker impedance, you risk damaging the amp.  In tube amps, too high a load impedance (or a disconnected load) can result in damage to the output tubes or output transformer,  while in solid state amps, if  the speaker impedance is too low, the amplifier will tend to overheat and more power is used up in the amplifier than is delivered to the speaker.  Too many speakers on a solid state amp can burn up the power output section.
(2) The amplifier will deliver maximum power (volume) to the speaker when the speaker impedance matches (is equal to) the internal impedance (called the OUTPUT IMPEDANCE) of the amplifier.  Too low an impedance will result in weak output and poor tone.  If the speaker impedance is higher than that of the amplifier, its power output will again be less than it is capable of. "

 

http://www.prestonelectronics.com/audio/Impedance.htm

[Sakkura]

Lower impedance means the current will get higher, eventually overloading the amplifier. But that shouldn't be likely with a single 4 ohm speaker. It's more of a thing that happens when people derp and connect speakers in parallel (so the total impedance drops).

[Pomfinator]

5 minutes ago, Profoundsoup said:

Well In the headphone world higher ohm means harder to drive. Like 800 ohm headphones require quite a bit of power. 

I thought we debunked his myth ages ago.  How hard something is to drive is an equation that includes both the resistance and sensitivity of the headphone, and is something that can only be really tested by actually plugging in your headphones and finding out yourself, since headphone companies don't always supply the same measurement of sensitivity.

 

For speaker amps, just find a receiver that tells you what they rated the power output at.  Even cheap SMSL mini-amps tell you that it's like 50wpc at 4ohm and 20wpc at 8ohm, etc.

[spwath]

It is best not to run 4 ohm speakers an amp that doesn't support it. It means 6 ohm and above.

 

That said, it will be fine if you are cautious. I run 4 ohm speakers on an amp that lists minimum impedance at 6 ohm.

[ThomasD]

What Rmusic said.

 

There are two different answers depending on the sort of amplifier involved.

 

With solid state amps - amps without output tubes (pre-amp tubes mean nothing)- you should never attach a load lower than the rated load.  Solid state amps generally have no built in protection for over dissipation.  When presented with a lower than expected load the amplifier will try to supply as much current as the circuit allows, this will cause it to over-dissipate and cook itself to death sooner or later.

 

Attaching a higher than rated load only reduces the maximum power output possible.  A high enough load (say ultra high impedance cans on a low power amp) may reduce output to inaudible levels, but it will not harm the amp or the cans.

 

Tube amps are somewhat different, and in general a lower than rated load is safer than a higher than rated load.  The reason for this has to do with what is called flyback voltage and the fact that tube amps also use an output transformer.  When voltage gets reflected back from the speakers it gets stepped up in the process.  A mismatch load can make this phenomenon much worse, to the point where the voltage either punches through the insulation between the laminates of the transformer core, or arcs across the pins of the output tubes.

 

Lower than rated loads are generally safer, even though the tube will try to over-dissipate just like solid state, but due to their inherent nature they are self limiting and simply will not over-dissipate to death (but tube life will be shortened.)

 

TL:DR - Solid state power amps require a matched or higher than stated load.

             Tube power amps can generally be run safely with a load from 1/2 to 2x stated load.

[EndlessOyster]

depends on wattage of the amplifier and how many watts your speaker can take, but wont matter as receivers have cheap amps in them most of the time.

 

and to all the people before saying you cant add this or that, well you can. if i have a 4 ohm 100w amp and i plug my 2 ohm 200 watt speaker in it will be perfectly fine.

[Stagea]

On 4/12/2016 at 10:00 AM, ThomasD said:

What Rmusic said.

 

There are two different answers depending on the sort of amplifier involved.

 

With solid state amps - amps without output tubes (pre-amp tubes mean nothing)- you should never attach a load lower than the rated load.  Solid state amps generally have no built in protection for over dissipation.  When presented with a lower than expected load the amplifier will try to supply as much current as the circuit allows, this will cause it to over-dissipate and cook itself to death sooner or later.

 

Most newer SS amps do have thermal protection though. They either shutoff or reduce output when the temps go too high. 

 

That being said, most cheaper AV receivers don't have enough current capacity to quickly self-destruct during real-world playback anyway. They have dinky transformers that causes the rails to collapse as you demand more from them (making the receiver sound bad at the limits, but not catastrophically die... at least not in the short term). Since they often have marginal heatsinks too, temps may start to rise if the listener can tolerate the distorted output (this can eventually trigger the thermal protect mode).

 

 

[spwath]

5 hours ago, Stagea said:

Most newer SS amps do have thermal protection though. They either shutoff or reduce output when the temps go too high. 

 

That being said, most cheaper AV receivers don't have enough current capacity to quickly self-destruct during real-world playback anyway. They have dinky transformers that causes the rails to collapse as you demand more from them (making the receiver sound bad at the limits, but not catastrophically die... at least not in the short term). Since they often have marginal heatsinks too, temps may start to rise if the listener can tolerate the distorted output (this can eventually trigger the thermal protect mode).

 

 

Yeah, i added a fan to the shelf the receiver was in, as it was getting warm, especially with my 4 ohm speakers.

[ThomasD]

11 hours ago, Stagea said:

Most newer SS amps do have thermal protection though. They either shutoff or reduce output when the temps go too high. 

 

That being said, most cheaper AV receivers don't have enough current capacity to quickly self-destruct during real-world playback anyway. They have dinky transformers that causes the rails to collapse as you demand more from them (making the receiver sound bad at the limits, but not catastrophically die... at least not in the short term). Since they often have marginal heatsinks too, temps may start to rise if the listener can tolerate the distorted output (this can eventually trigger the thermal protect mode).

 

 

Thermal protection yes, some better ones do have it.

 

But it doesn't take very much excess current to fry a cheap SS amp, and I would not depend on current limiting from the power transformer to save anything.  That's almost as bad as expecting power resistors to act like fuses.

 

Simpler and easier just to avoid using a light load.