i have seen in car amps that the wattage rating is based on ohm loading. when i started learning about car audio i just look for ways to get the ohm loading as low as possible and it wasent until this point that i started asking why am i doing this?
i can see how it would be easier to sell an amplifier that states 1000 watts stamped on the side vs 500 watt. but this doesnt really clarify what ohm loading the amp is recommended for normal use.
what is actually happening inside the amp 2 ohm vs 4 ohm load? do the transistors act differently when more resistance is introduced?
it doesnt help that there are people all over youtube boasting .25 ohm load on their car that can bend the trunk inside out.
it makes sense that if by halving the ohms you double available output of the amp then why not just keep halving it till you get the most power? i obviously realize this is a fast ticket to shorting the amp out but my question is still valid.
is there any difference in sound quality? efficiency? life span of the amp?
is there subs out there that come with insanly low ohms on a single coil? with the express intent of drawing a lot of current?
i can see how it would be easier to sell an amplifier that states 1000 watts stamped on the side vs 500 watt. but this doesnt really clarify what ohm loading the amp is recommended for normal use.
what is actually happening inside the amp 2 ohm vs 4 ohm load? do the transistors act differently when more resistance is introduced?
it doesnt help that there are people all over youtube boasting .25 ohm load on their car that can bend the trunk inside out.
it makes sense that if by halving the ohms you double available output of the amp then why not just keep halving it till you get the most power? i obviously realize this is a fast ticket to shorting the amp out but my question is still valid.
is there any difference in sound quality? efficiency? life span of the amp?
is there subs out there that come with insanly low ohms on a single coil? with the express intent of drawing a lot of current?
As you get lower, the amp becomes horribly inefficient. The lowest I've seen in person was the Incriminator Audio 20.1, stable into a quarter-ohm load (a real 1/4-ohm after impedance rise, not a nominal value)...it was a current hog like none other, though. This is why amp manufacturers won't offer warranty coverage below 1 ohm, generally - for a typical "street beater", it results in too many blown amps with people who don't know what they're doing.
The low ohm loads became popular through SPL competitions. They were in classes based on the amp's power ratings at 4ohms. Therefore people would wire their amps down as low as possible to 1/4 and 1/8 ohm loads to get the most available power when burping. Obviously this results in more power and a higher score. Some amps handle in better than others, many Korean amps (IA, Sundown, Atomic, RD,some DD) work at the ohm loads, while others cannot take it. Therefore they became popular choices in the SPL scene. They also produce coil/custom make coils, that are DVC 0.5/0.25, quad 0.5/1.0 etc.
However this is not adequate for daily driving situation. Those low loads were used for short periods of time often on sine waves. They would have trouble playing music, and staying cool for everyday listening. The extra current draw and lack of efficiency at the lower loads would also drain your vehical's charging system if not adequately beefed up. I believe the amp's THD also greatly rises as impeadence is dropped. Not a problem in competitions but an issue for daily.
Therefore it is not very practical to try these low loads for most situations. I have run an amp at 0.5 ohms for some time with no ill effects (amp rated down to 1 ohm). But it draws more current. In most cases the wattage gains found by dropping impeadence may not be all that audable anyway, and it just puts more stress on the amp.
However this is not adequate for daily driving situation. Those low loads were used for short periods of time often on sine waves. They would have trouble playing music, and staying cool for everyday listening. The extra current draw and lack of efficiency at the lower loads would also drain your vehical's charging system if not adequately beefed up. I believe the amp's THD also greatly rises as impeadence is dropped. Not a problem in competitions but an issue for daily.
Therefore it is not very practical to try these low loads for most situations. I have run an amp at 0.5 ohms for some time with no ill effects (amp rated down to 1 ohm). But it draws more current. In most cases the wattage gains found by dropping impeadence may not be all that audable anyway, and it just puts more stress on the amp.
You have already answered your own question😉
An amplifier is designed with certain goals in mind. Operating at a certain impedance is one of these goals. All of the components within the circuitry each have their own current limitations. Loading down an amplifier below it's rated limits will cause components to fail. Many times a protective fuse will not blow before some components will if the amp is abused.
(simplified answeres)
Typically sound quality goes down as impedance drops..
Efficiency depends on the amplifiers design..
Expect the life span of the amplifier to drop significantly if it is operating below recommended limits.
Keep in mind that as the load on the amplifier is lowered, current draw increases. More current draw=more heat. More heat=shorter life.
Yes. I've seen some drivers with .3ohm coils. Typically designed for the SPL arena, and used with amplifiers designed to run very low impedances and/or very short time frames
as you guessed power output P = Esqared/R E is the voltage the amp puts out and R is the resistance of the amplifier . From the formula if R is halved then power should go up by 2. Providing that the amplifier can deliver the SAME voltage to a lower load. Example. Voltage is 20 volts, for an 8 ohm load power = (20*20/8) = 400/8 = 50 watts, for 4 ohms 400/4= 100, for 2 ohms 400/2= 200 watts. etc. Not all amplifiers can drive 1 ohm or lower loads, and what is the loss in the connectors and the hook up wire for the speakers. At very low loads wire losses, power supply losses(battery), connectors, wire length all become important factors. These losses are also inside the amplifier as well. Have you ever used an electric kettle and ran it to boiling then unplug the power cord? Was it warm? Power loss in the cord. You can put all the speakers you want to in parallel to increase the power output of the amplifier, can the amplifier actually deliver power to a very low load and how much is getting to the speaker it self? It doesn't take much to flex a trunk. push on a car panel, how hard was it to bend. If you look at the speaker builders threads all the DIY guys are forever trying to find ways to reduce panel flexing and vibration and not trying to flex the panels as much as possible.
what is actually happening inside the amp that causes more power to be output?
i have an understanding of ohms law but it seems there would be a finite amount of power in the amp. rail voltage remains the same doesn't it?
i have an understanding of ohms law but it seems there would be a finite amount of power in the amp. rail voltage remains the same doesn't it?
Nothing happens in the amp to produce more output power. You are changing the load that the amp sees. If you replace your 100 watt light bulb with a 250 watt bulb did you change anything in the lamp socket? No, you changed the resistance the socket sees.
The rail voltage will dip when the load impedence is dropped.
Infinite power, no, you can only get out what you put in. That is saying your amp is 100% efficient and it is not.
The rail voltage will dip when the load impedence is dropped.
Infinite power, no, you can only get out what you put in. That is saying your amp is 100% efficient and it is not.
1) Power out = power in minus friction
2) Power out = Voltage out * Voltage out / impedance
3) Voltage out = RCA Voltage in * amplifier voltage gain
A car amp is nothing more than a voltage multiplier. If the amp produces a gain of 20x, then a 1 volt input (RCA) signal produces a 20 volt output (speaker) signal.
Look back at #2 above:
The 20 volt output signal into 4 ohms will be
20*20/4 = 100W
into 2 ohms will be
20*20/2 = 200W
into 1 ohm will be
20*20/1 = 400W
This happens because for a given voltage output, as the load impedance drops, more current will be drawn. Hence, the power output is higher.
The higher output current must be delivered through the amplifier, which if it isn't designed to handle that, will smoke.
2) Power out = Voltage out * Voltage out / impedance
3) Voltage out = RCA Voltage in * amplifier voltage gain
A car amp is nothing more than a voltage multiplier. If the amp produces a gain of 20x, then a 1 volt input (RCA) signal produces a 20 volt output (speaker) signal.
Look back at #2 above:
The 20 volt output signal into 4 ohms will be
20*20/4 = 100W
into 2 ohms will be
20*20/2 = 200W
into 1 ohm will be
20*20/1 = 400W
This happens because for a given voltage output, as the load impedance drops, more current will be drawn. Hence, the power output is higher.
The higher output current must be delivered through the amplifier, which if it isn't designed to handle that, will smoke.
V/R=I
There is a limit to how low R can be before the amp can't deliver any more I. Also, the lower R is, the more V will drop under high output.
I think some of the confusion comes from why these low impedance configurations are more common in the car audio industry. It has to do with trying to get a higher voltage from that pathetic 12V power source. It's not so easy to build a SMPS with the high voltage needed to drive an 8-ohm speaker at >1000W.
There is a limit to how low R can be before the amp can't deliver any more I. Also, the lower R is, the more V will drop under high output.
I think some of the confusion comes from why these low impedance configurations are more common in the car audio industry. It has to do with trying to get a higher voltage from that pathetic 12V power source. It's not so easy to build a SMPS with the high voltage needed to drive an 8-ohm speaker at >1000W.
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I have seen amp manufacturers that claim their amplifiers will run stably into a dead short.
Is that a fallacy?
Is that a fallacy?
Ohms law says that if you drop the load by one half the current across the load will double. < Not taking into account the voltage drop that will also occur, loading any supply will cause Voltage to drop as Current rises.
This how they get to say the amp doubles power output. In the real world we all live in though its a completely different situation. Speaker loads are reactive and non-linear at best. So just adding speakers does not always get you where you think your heading or want to be.
Moving two comes does produce more air movement to a point so the aural effect can be similar to doubling your power.
You also cut the damping factor in half when you drop the speaker load and this can cause a SQ loss in some cases. Since Damping factor does effect SQ somewhat in many peoples opinion. Damping factor effects the amps ability to control speaker cone movement in simple language.
For the amp to actually double power the power supply must be able to supply twice the output current. hence all the blown power supplies, and outputs you see.
Many amp makers design there power supply to limit the 2 ohm power to about 50% more then 4 ohm loads. On record are the Harmon Kardon TC series of amps which honestly IMO stated that their High current amps only did 1.5 times their 4 ohm rating into a 2 ohm rating.
There is a finite limit to load dumping versus power gain, and remember the most that load dump got you was 3 DB's more power to the speaker. That does not mean you got 3 DB's more out of the speaker. And 3 DB's is the noticeable level change that most people can hear as "somewhat louder".
To actually double the SPL you would need to go 10 DB the power to double the SPL. Most folks over look the laws of acoustics when SPL'ing. Hence the multitude of 10KW amps on the market. Most all of which to my limited knowledge are Class D switch amps which like the description says are nothing more then D class Power switches turning on and off huge DC power supplies into speaker/motor loads. Or light bulbs or just about any load you might try to run I guess...😎
And its all up the outputs and the power supply to handle all this. I say buy 10 gazillion watts worth of amps at 4 ohms and run them happily at 4 ohms with very little failure rates. Remember you get what you pay for in this world, and if you really need all that power then buy it at a reasonable load level and get a reasonable lifespan out of your gear... Stop letting a marketing salesman tell you what to do....Hot-rodding gets very expensive, and I never saw a NASCAR car with 100,000 miles on it, have you ????
No certain real amp makers have designed there amps so that a short circuit will not harm them. They can do this by using huge arrays of power output devices and by limiting the power supply feeding them so it literally shutdown after X amount of load power draw.
My Adcoms can play into screw drivers, I know this cause I tested them this way back in the 90's when they were built and sold.
many amp makers test their safety circuitry by shorting the amp output, but this is just a safety test an the amp is suppose to shut down not play.
It is a paradox - A speaker is a voltage driven device - car guys only have 12 of them - or 13.8 if you include the charge increase.... and car ppl tend to strap more speakers on the end of an amplifier, finding every hole, cleavage and butt crevice to insert them in. Then after that, install a 15" subwoofer (requiring the bulk of the energy) with only 200 cubic litres of air to move before saturation - possibly inside something as tame and meaningless as a Ford **** box.
Also an industry which has the propesity to claim Watts that dont exist. Like you'll see an amplifier no bigger than a small book claiming 3000Watts
That's because the sales people use Volts squared... instead of Volts squared over impedance.
But in answer to the question of 2Ω or 4Ω -- which ever makes the loadest hum. 😉
...I'm going straight to hell for this, I just know it -- I hope my fellow designers come in here and drag my bones outta here and bury me with honours. 😉
My guess would be the sound was a little "thin". Probably sounded good playing Metal though.
😛
Lol lol lol I actually had a 4 ohm mono load connected also and the music level muted sharply as the screw drivers sparked together. I did this for 4 minutes trying to destroy a Adcom 4402 powered by a HP Harrison type lab grade 50 amp supply. The sales rep said it was almost indestructible. We tried to find out for him.
A 80 watt amp mono'ed into a dead short powered by a 50 amp 14 volt lab grade supply. Oh the screw drivers did get hot by the way lol lol lol..too hot to touch...It took a minute or two for the amps fans to speed up to full speed.
Oh and we loaded the supply all the way to 50 amps at 14 volts doing this test, so the short was drawing some fair power.
I seriously think if I had more power the worst I would have seen would have been a foil trace act like a fuse under the board. I have repaired several of these copper trace fuse links before over the years.
The amp went right back to playing music after the dead short was removed like nothing had happened at all...I was impressed for the year of 1992... And I have never seen anything like this again since...ahh the good old days...🙂
since i started this thread i have been looking around at amps and they ALL seem to just say...
X watts at 4 ohm and
X(2) watts at 2 ohm
some even make the leap to 1 ohm. it makes sense that they are relying heavily on the math to prove this. then just take the biggest number and stamp it on the amp. this makes it difficult for new guys like me trying to compare amps.
my question then, is which ohm rating is most valid? if the amps power supply is a little over built to handle 1 or 2 ohm loading then is it possible to have double or quadruple the power efficiantly transfered to a loud speaker. what is causing me to ask these questions is that as soon as i wire a 2-1 ohm load then the amp gets hot quite quickly. this has to be wasted energy here doing this and this has to be eating into the advertised power rating numbers
now i have 2 jbl bp1200.1 amps driving one dual voice coil speaker. do i wire one amp at 2 ohm to produce 1200 watt OR two amps at 4 ohm each driving its own winding in the coil (600x2)? according to the marketing its the same thing
i dont really get confused by these although i see these amps all over the place i just dismiss them as a complete lie. where i get confused is a reputable amp manufacturer claiming 3000w at some completely ridiculious ohm load.
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