Hey guys, I'm not sure what section this goes in, since it deals with Home audio, car audio, amplifiers, and other stuff. Feel free to move it.
This has probably been asked before, but I've never found a clear answer.
My question is this: Why is Car audio equipment rated so much higher than Home Audio equipment?
Here is the comparison: I'm going to look at the Pioneer Elite A-20 and the Pioneer GM-A5602. Now don't get me wrong, I get that these are very different classes of Amplifiers, but I'm trying to understand why the $300 Elite only has 30W per channel, whereas the $100 GM has 150W per channel.
It seems like on average, home theatre amplifiers and receivers are rated rather conservatively, and car audio equipment is rated super high. A 1000W class AB car audio amplifier is nowhere near the cost of a 1000W class AB home theatre amplifier.
This seems like the case for speakers and subwoofer as well. The vast majority of 10" and 12" home theatre subwoofers are rated around 100-300W, whereas the vast majority of car subwoofers at the same size are rated around 1000-3000W.
Isn't it true that you can damage speakers by using too little wattage. If so, why are the majority of vintage receivers I find rated for only 30, 50, or 80W a channel, and were being used to drive these 200W 3-way cabinets?
Also, how does this make sense? How can a 50W amplifier damage a 500W speaker? Wouldn't the amplifier simply not have enough power to cause the speaker to bottom out, overheat, go over it's excursion limits, and so on?
If anyone has the answer to any of these questions I'd definitely appreciate it!
Thanks!
This has probably been asked before, but I've never found a clear answer.
My question is this: Why is Car audio equipment rated so much higher than Home Audio equipment?
Here is the comparison: I'm going to look at the Pioneer Elite A-20 and the Pioneer GM-A5602. Now don't get me wrong, I get that these are very different classes of Amplifiers, but I'm trying to understand why the $300 Elite only has 30W per channel, whereas the $100 GM has 150W per channel.
It seems like on average, home theatre amplifiers and receivers are rated rather conservatively, and car audio equipment is rated super high. A 1000W class AB car audio amplifier is nowhere near the cost of a 1000W class AB home theatre amplifier.
This seems like the case for speakers and subwoofer as well. The vast majority of 10" and 12" home theatre subwoofers are rated around 100-300W, whereas the vast majority of car subwoofers at the same size are rated around 1000-3000W.
Isn't it true that you can damage speakers by using too little wattage. If so, why are the majority of vintage receivers I find rated for only 30, 50, or 80W a channel, and were being used to drive these 200W 3-way cabinets?
Also, how does this make sense? How can a 50W amplifier damage a 500W speaker? Wouldn't the amplifier simply not have enough power to cause the speaker to bottom out, overheat, go over it's excursion limits, and so on?
If anyone has the answer to any of these questions I'd definitely appreciate it!
Thanks!
Ill start. First off, speaker damage from underpowered amps. This is caused by overdriving the amp into clipping which creates a lot of high frequencies which multiplys the amount of power into the tweeter. Tweeters normally take a fraction of the power the woofer needs so speakers are designed with this in mind. ( a 100 watt speaker has a 20 watt tweeter ) . If you don't overdrive your amp or have full range speakers this is not a problem.
Component power ratings these days have been taken over by the marketers. Mostly BS to sell the product. Especially car and home theatre amps. Comparing the 2 isn't easy. Home theatre "amps" are actually receivers and have anywhere from 5 to 11 channels and all the switching and decoding DSP not to mention a lot more of the more expensive parts, chassis power transformer and connectors.
I see a lot of home theatre receivers that spec 100 watts per channel (7 channels) but have a max input current of 3 amps. So 360 watts in is supposed to get you 700 watts out ? Wow noble prize for creating energy out of nothing.
I see a lot of home theatre receivers that spec 100 watts per channel (7 channels) but have a max input current of 3 amps. So 360 watts in is supposed to get you 700 watts out ? Wow noble prize for creating energy out of nothing.
Hey thanks for the reply cbdb! I understand that this might be true for tweeters, but is this the same principle for woofers and subwoofers?
I hope you can understand my question here. Power is finite, meaning that the power in and out of an amplifier can only be some amount of watts before the amplifier either burns out, catches fire, or shuts down.
I still find it hard to believe that an amplifier that has a Maximum rating of 100W, which is what the transformer is rated to deliver, can damage a woofer rated at 500W. Sure, high frequencies at 500W will kill it, but will high frequencies at 100W kill it as well?
I hope you can understand my question here. Power is finite, meaning that the power in and out of an amplifier can only be some amount of watts before the amplifier either burns out, catches fire, or shuts down.
I still find it hard to believe that an amplifier that has a Maximum rating of 100W, which is what the transformer is rated to deliver, can damage a woofer rated at 500W. Sure, high frequencies at 500W will kill it, but will high frequencies at 100W kill it as well?
Just looked up specs for a decent pro amp (qsc ). The second "feature" they tout on their "spec sheet" says " the 4000watt xxxx amp operates of a standard 15amp plug (120v). So 1800 watts in for 4000watts out. WTF. Do the marketers think the pros using this gear believe this BS. Maybe they do.
I don't know who says it, I've just heard it floating around, and I'm trying to understand if that is in fact possible. IMHO I find it hard to believe that I can destroy my 500W car subwoofer with my 50W per channel home amplifier, but that's what I've heard before.
"When you under power a sub and over drive the amp because the amp can not Supply the amount of power needed to run the sub the amp will produce DC Current and cook the Voice coil its like a radiator heater the coil heats up and expands. "
"Severe clipping can produce up to 2x the rated thermal power...obviously this could cause thermal damage"
Something like this I guess, but I don't believe it.
"When you under power a sub and over drive the amp because the amp can not Supply the amount of power needed to run the sub the amp will produce DC Current and cook the Voice coil its like a radiator heater the coil heats up and expands. "
"Severe clipping can produce up to 2x the rated thermal power...obviously this could cause thermal damage"
Something like this I guess, but I don't believe it.
Yes, I agree that most of it is marketing BS, but still... why? It seems so strange to rate Home theatre equipment at 100W and similarly priced car audio equipment at 1000W. Maybe it's the same reason people buy 3HP blenders and 5000psi pressure washers...
The plug needs to be rated for just clipping pink noise, which is 1/8th of the power that the amplifier would output if it were capable of driving continuous sine waves at the onset of clipping.
Not all amps can drive continuous sine waves.
Continuous pink noise with a 9dB crest factor driven to clipping is supposed to be a pretty much worst-case scenario. It is possible to get worse, but its quite rare.
If the amp can deliver 8x that power continuously as a sine wave, then you might find an amp that's rated at 500w (plus a little bit for inefficiencies) from the wall, but can in fact output 4KW.
It will draw more than 4KW from the wall, if you ask it to produce sine waves at the onset of clipping and keep it there.
So, in most usage, the 4KW peaks will occur briefly. They'll be unclipped. But the average power will be around 500w.
FWIW that's for fairly efficient amps. For class AB etc, double the power from the wall for the same output.
Chris
Ok i'm no expert in this matter but usually you don't listen to perfect sinusoidal waves but music. Music has highs and lows (dynamics) and so the input fuses are rated for about 1/8 or 1/4 total power...This is how you create power from nothing. You are listening to an average say 100 W musical energy before clipping (but You thing you are hearing 1000 W) Yes there will be some peaks and the amp can withstand them for a fraction of a second.... If you were hearing perfect sinusoidal waves or even DC, you would be building heaters.
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Take an amp which can output 50W average power continually. Some people might describe that as a 50W amp. However, on temporary peaks with quieter passages in between it can manage 80W average. Assuming sine waves, 80W average is 160W peak power. There are two channels, so call it 320W. 320W is almost 400W, so call it 400W. Use Chinese watts and it is 600W or more. Use a 4 ohms speaker instead of 8ohm and call it 1kW.
Also, remember that for some car audio enthusiasts power is everything. Whatever is the main selling point will get exaggerated in advertising.
Also, remember that for some car audio enthusiasts power is everything. Whatever is the main selling point will get exaggerated in advertising.
Yep. That's how it's done. And then rate the car amp bridged into a 2 ohm load and you've got you huge power numbers.
I remember Rod Elliott's article on this topic.
For the stupid numbers, you can do something like the following:
- measure the steady-state voltage of the power supply
- short it, measure instantaneous current. It doesn't have to survive.
V*I=maximum possible power output. Even a 12v wall wart will pass a lot of current for a microsecond.
Most PA amps follow what I said in my previous post, though.
Chris
For the stupid numbers, you can do something like the following:
- measure the steady-state voltage of the power supply
- short it, measure instantaneous current. It doesn't have to survive.
V*I=maximum possible power output. Even a 12v wall wart will pass a lot of current for a microsecond.
Most PA amps follow what I said in my previous post, though.
Chris
Think about how a flash unit on a camera works. AA batteries produce a few watt hours of power. However, if you charge a capacitor and discharge it in a millisecond, the power dissipated at that moment can be hundreds of watts.
The same goes for the class D amplifiers. They rely on the crest factor of music (about 9dB). Sure, their continuous average power is limited by the wall socket x efficiency factor, but capacitors can store more energy for a kick drum hit.
Average crest factor of recorded music is not 9 dB, unless you are listening to some very compressed music. Just FYI
The way it used to be:
Home amps were rated (FTC) RMS power per channel with specified 20-20k distortion into 8 ohms and had to survive a 30% power warm up stage (many could get quite hot during this). Often they would put out 10-20% more power than rated, depending on the mfg. Amps like NAD or Proton which were touted as having high 'dynamic power' were really just amps built with small heatsinks and power supplies.
Car amps were rated for peak power (2x RMS) into 4 ohms. This means that they usually rated 4x higher than an equivalent home amp. Amps rated into 2 or one ohm could have an additional factor of 2 or 4.
Pro amps were usually given model numbers based on the sum of 2 channels into a 4 ohm load, or sometimes bridged. Say the amps was 250W RMS per channel into 8 0hms. That amp would put out roughly 500 per channel into 4 and the model # would then be xxx1000. Bridged, it might do 700 watts at 8 ohms and 1400 at 4, so the model could be xxx1400. Most true pro amps would also give the FTC style rating buried in the specs somewhere.
I owned a pair of computer speakers (bought in 1998) that were advertised 200W and perhaps weighed a half pound. I laughed when I bought them, and laughed even harder when I took them apart. These had a <1W chip amp in them.
Modern home theater amps are usually rated with one or two channels driven, afaik.
Crest factor for recorded popular music back in the 60s-80s may have been ~12dB, but today 9dB would be fairly good. 😉 The highest crest factor recording I have is 23dB.
Home amps were rated (FTC) RMS power per channel with specified 20-20k distortion into 8 ohms and had to survive a 30% power warm up stage (many could get quite hot during this). Often they would put out 10-20% more power than rated, depending on the mfg. Amps like NAD or Proton which were touted as having high 'dynamic power' were really just amps built with small heatsinks and power supplies.
Car amps were rated for peak power (2x RMS) into 4 ohms. This means that they usually rated 4x higher than an equivalent home amp. Amps rated into 2 or one ohm could have an additional factor of 2 or 4.
Pro amps were usually given model numbers based on the sum of 2 channels into a 4 ohm load, or sometimes bridged. Say the amps was 250W RMS per channel into 8 0hms. That amp would put out roughly 500 per channel into 4 and the model # would then be xxx1000. Bridged, it might do 700 watts at 8 ohms and 1400 at 4, so the model could be xxx1400. Most true pro amps would also give the FTC style rating buried in the specs somewhere.
I owned a pair of computer speakers (bought in 1998) that were advertised 200W and perhaps weighed a half pound. I laughed when I bought them, and laughed even harder when I took them apart. These had a <1W chip amp in them.
Modern home theater amps are usually rated with one or two channels driven, afaik.
Crest factor for recorded popular music back in the 60s-80s may have been ~12dB, but today 9dB would be fairly good. 😉 The highest crest factor recording I have is 23dB.
My Ultimate Fireworks Blu-ray, which I recorded in 24-bit/96KHz with five channels/mics, has an 86dB crest factor. Everything varies, but average music has been listed as being about 9dB.
A subwoofer effectively air-cools itself with it's excursion while it works. A severely clipped signal limits it's peak-to-peak excursion and therefor it's ability to cool itself. Yes, a 30W amplifier feeding a heavily clipped signal can fry a 300W subwoofer's
... voice coil?
I know that my car stereo installer / repair buddy can relate horror stories of fried crossover components -generally attenuation resistors, and melted caps, burnt pcbs - from over driving, and even melted power cables from systems with heavy duty alternators, back up caps, batteries, etc, but can never recall a blown subwoofer.
I know that my car stereo installer / repair buddy can relate horror stories of fried crossover components -generally attenuation resistors, and melted caps, burnt pcbs - from over driving, and even melted power cables from systems with heavy duty alternators, back up caps, batteries, etc, but can never recall a blown subwoofer.
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An RMS value of -18dBFS was a widely used mastering level for years. Many good rock, pop, jazz and country CD where done at that level. Classical tended to be -22dB to -24dB. A CD mastered at -9 would be LOUD! They do exist, and are getting more frequent, but they are the ones that so many people complain about being overly compressed -AKA the Loudness Wars. I do have a few heavy metal CDs that are at -10dB.
The whole amp power thing is so goofy. When does it date from - the old AM radio transmitters? Did that get carried over into audio amplifiers?
Rating them in volts RMS would be sooo much better. That's not going to happen, but it would be a much better way to rate amplifiers.
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