Ohms law help, not grasping

[Blindside1234]

Been doing alot of research on the topic, but I just cant get it. I have a dual 4ohm voice coil 1,100 watt sub. right now its running in parallel to achieve a 2 ohm impedence. Its ram by a 2 ohm 600 watt amp, the amp is just not giving it enough power. So im in the market for a new amp, the mono amps that im interested in are all capable of going down to 1 ohm, it is impossible to wire my 1 sub into 1 ohm, so if i send a 1 ohm (bridged from amp) load to a 2 ohm speaker this will blow it right? If not what are the risks. i understand idealy you want to match ohms, but all the amps go down to 1 ohm with like 300 watts more that wiring it into 2 ohms, this means i need a more powerfull amp (1000 at 2 ohms) to power it correctly. But if i could get the speaker down to 1 ohm i wouldn't need such a powerfull amp. hit me back, thanks

[Titano24's]

Originally Posted by Blindside1234

Been doing alot of research on the topic, but I just cant get it. I have a dual 4ohm voice coil 1,100 watt sub. right now its running in parallel to achieve a 2 ohm impedence. Its ram by a 2 ohm 600 watt amp, the amp is just not giving it enough power. So im in the market for a new amp, the mono amps that im interested in are all capable of going down to 1 ohm, it is impossible to wire my 1 sub into 1 ohm, so if i send a 1 ohm (bridged from amp) load to a 2 ohm speaker this will blow it right? If not what are the risks. i understand idealy you want to match ohms, but all the amps go down to 1 ohm with like 300 watts more that wiring it into 2 ohms, this means i need a more powerfull amp (1000 at 2 ohms) to power it correctly. But if i could get the speaker down to 1 ohm i wouldn't need such a powerfull amp. hit me back, thanks

an amp does not have a "ohm" rating..........amps are just stable down to a certain ohm load........

and your speaker won't blow, distortion blows speakers. any mono amp will be fine, while it won't make the same power as it would at 1ohm load it will still make a hell of a lot.

[bestatchess]

www.bcae1.com explains all this stuff. See, for example, section 58.

[grunge311]

Amps send out power, not rated at anything. The speakers you hook to it determines the load.

The lower ohm speakers you hook to it, the less resistance the amp has, which means the more power it pushed out, which means teh hotter it gets.

When they say and amp is 1ohm stable it means it goes down to one ohm before it gets so hot that it goes to protect mode.

It is NOT possible to wire a dual 4ohm into one ohm, one 2 or 8.

Also it will be VERY expensive to get 1100w into a 2ohm load.

What sub do you have? I don't know of any subs that go 1100w rms, max maybe, but never ever ever pay attention to max.

[Blindside1234]

audiobahn flameQ 12 inch, so if i bridge the outputs on my amp that would be sending a 1ohm load to the sub right? Or since the sub is only capable of a 2 ohm load it wont matter how i wire it to the amp it will always be 2 ohm (if wired in parallel) lets just say (so i can get it) a sub is wired to be 8 ohm and i wire it to my amp bridged (sending a 1 ohm load to it) will it be getting the full wattage of the 1 ohm, or will it be getting 8 ohms from my amp (and whatever the watts are that correspond to 8 ohm)

[MuskyHunter]

Its ram by a 2 ohm 600 watt amp, the amp is just not giving it enough power.

One thing I always hated about buying car audio is not knowing what you are getting and if often deceptive. I sold car audio for many years and ended up hating it because most of the products (with exception to the high performance quality brands) misrepresent the power ratings and you end up with poor results.

600 Watt amp rating you mention doesn't mean much on its own. Is this a two channel amplifier bridged mono to supposedly deliver 600 Watts in that mode, or is the 600W figure the summed channels of a multi channel amp. If you had an amplifier that delivered 600 Watts into 2 Ohms (roughly 300 Watts into 4 Ohms) over a frequency range of 20-20,000 Hz with under 0.5% distortion rated at a reference power voltage of a true 12V, that amp would be more than adequate for most people.

Second, power doesn't mean much as a speaker is a current device and not a voltage device. It is difficult to get a spec on the amplifiers output current unlike quality home components which give that rating. Many cheap car amplifiers using MOSFET output stages are high voltage, low current amplifiers. They are very common and marketable in that they can post some amazing power numbers for low cost, but sound like crap because of low current outputs. Amplifiers designed with Bipolar output transistors tend to be higher current and lower voltage amplifiers and are going to be much more expensive. If you aren't getting the kick out of your speakers, it is likely that your amplifier is not capable of delivering high output current levels.

Third, for low distortion high performance applications, it is suggested not to use 2 Ohm speaker loads. Just because an amplifier is "2 Ohm stable" doesn't necessarily mean two 4 Ohm speakers can be connected in parallel. Speaker impedance is dynamic and fluctuates over the frequency range. With the impedance highest at speaker resonance, impedance drops quickly for frequency ranges higher than resonance, meaning your load may actually be lower than 2 Ohms over certain range of frequencies for the 4 Ohm driver. The closer to zero Ohms you get, the closer you are to presenting a shorted load to the amplifier, meaning higher amounts of audible distortion and potential amplifier damage.

The blue curve in the attached file is the impedance curve for a nominal 4 Ohm speaker. The dots on the blue line showthat from about 75 Hz to 175 Hz, the driver is operating in the range of about 2.5 Ohms. Run two of these speakers in parallel and you will be running about 1.25 Ohms from 75-175 Hz which is bad for a 2 Ohm stable amplifier. Some amplifiers may have internal protection which may limit output for impedances below 2 Ohm loads meaning a throttling back of output.

If it were me, I would run one of the coils to one amp/amp channel, and the other coil to another amp/amp channel so each amp/amp channel will see 4 ohms. In doing this you can do some "creative tuning" by having two different crossover points for each amplifier input. For example, on my home speakers I have a 2 1/2 way design with three drivers. The lower woofer operates from 30-200 Hz, the second woofer operates from 30-3000 Hz, and the tweeter operates from 3000 Hz +. Below 200 Hz the two woofers operate together to give me the surface area needed for low frequencies, but only one woofer is operational in the low to midrange to improve imaging and reduce midrange coloration.

In an active crossover situation with subs, you can have both coils operational at low frequencies, but you can dial out some boominess by having only one coil operational, lets say in the 60-80 Hz range by adjusting one crossover/input with a cutoff at 50 Hz and the other crossover/input cut off at 120 Hz.

If you are going to go out and buy and amp, watch your spec's. If an amp rates a power without reference to the frequency range, % distortion, and reference power voltage at that rated power, then that power number is useless. If the amp is rated at 600 Watts with a test frequency of 1 kHz, you could figure 5 to 10 times less power when rated over a range of audible frequencies (20-20,000 Hz).

[MuskyHunter]

Oops, here is the attachment.

[Blindside1234]

Originally Posted by MuskyHunter

One thing I always hated about buying car audio is not knowing what you are getting and if often deceptive. I sold car audio for many years and ended up hating it because most of the products (with exception to the high performance quality brands) misrepresent the power ratings and you end up with poor results.

600 Watt amp rating you mention doesn't mean much on its own. Is this a two channel amplifier bridged mono to supposedly deliver 600 Watts in that mode, or is the 600W figure the summed channels of a multi channel amp. If you had an amplifier that delivered 600 Watts into 2 Ohms (roughly 300 Watts into 4 Ohms) over a frequency range of 20-20,000 Hz with under 0.5% distortion rated at a reference power voltage of a true 12V, that amp would be more than adequate for most people.

Second, power doesn't mean much as a speaker is a current device and not a voltage device. It is difficult to get a spec on the amplifiers output current unlike quality home components which give that rating. Many cheap car amplifiers using MOSFET output stages are high voltage, low current amplifiers. They are very common and marketable in that they can post some amazing power numbers for low cost, but sound like crap because of low current outputs. Amplifiers designed with Bipolar output transistors tend to be higher current and lower voltage amplifiers and are going to be much more expensive. If you aren't getting the kick out of your speakers, it is likely that your amplifier is not capable of delivering high output current levels.

Third, for low distortion high performance applications, it is suggested not to use 2 Ohm speaker loads. Just because an amplifier is "2 Ohm stable" doesn't necessarily mean two 4 Ohm speakers can be connected in parallel. Speaker impedance is dynamic and fluctuates over the frequency range. With the impedance highest at speaker resonance, impedance drops quickly for frequency ranges higher than resonance, meaning your load may actually be lower than 2 Ohms over certain range of frequencies for the 4 Ohm driver. The closer to zero Ohms you get, the closer you are to presenting a shorted load to the amplifier, meaning higher amounts of audible distortion and potential amplifier damage.

The blue curve in the attached file is the impedance curve for a nominal 4 Ohm speaker. The dots on the blue line showthat from about 75 Hz to 175 Hz, the driver is operating in the range of about 2.5 Ohms. Run two of these speakers in parallel and you will be running about 1.25 Ohms from 75-175 Hz which is bad for a 2 Ohm stable amplifier. Some amplifiers may have internal protection which may limit output for impedances below 2 Ohm loads meaning a throttling back of output.

If it were me, I would run one of the coils to one amp/amp channel, and the other coil to another amp/amp channel so each amp/amp channel will see 4 ohms. In doing this you can do some "creative tuning" by having two different crossover points for each amplifier input. For example, on my home speakers I have a 2 1/2 way design with three drivers. The lower woofer operates from 30-200 Hz, the second woofer operates from 30-3000 Hz, and the tweeter operates from 3000 Hz +. Below 200 Hz the two woofers operate together to give me the surface area needed for low frequencies, but only one woofer is operational in the low to midrange to improve imaging and reduce midrange coloration.

In an active crossover situation with subs, you can have both coils operational at low frequencies, but you can dial out some boominess by having only one coil operational, lets say in the 60-80 Hz range by adjusting one crossover/input with a cutoff at 50 Hz and the other crossover/input cut off at 120 Hz.

If you are going to go out and buy and amp, watch your spec's. If an amp rates a power without reference to the frequency range, % distortion, and reference power voltage at that rated power, then that power number is useless. If the amp is rated at 600 Watts with a test frequency of 1 kHz, you could figure 5 to 10 times less power when rated over a range of audible frequencies (20-20,000 Hz).

So when i look for a new amp, its kinda like buying a used car the sticker price might seem like a great deal, but if you know nothing about cars, you dont know what your buying, and if you did know about cars you wouldnt buy the car that not only fits your checkbook standards but also the performance standards. So with my sub in mind (12 inch flameQ 1100 watt average power audiobahn wired into 2 ohms with a sealed box) i am not just looking for a 1100 watt (average power) amp im looking for much more, but all those terms were a little over my head. I want to stay at about 250.00 what attributes am i looking for. Not to use the car terminology again, but when purchasing a car dont just look at the sticker price and horsepower , but inspect the engine, trans, mileage, yada yada to insure that u have a quality product. I want an amp that will alow this sub to perform at its peak performance (or near it) instead of telling me what amp and model, please let me know the attributes that makes an amp good, powerful, clean ect. Thanks

[Titano24's]

Originally Posted by Blindside1234

audiobahn flameQ 12 inch, so if i bridge the outputs on my amp that would be sending a 1ohm load to the sub right? Or since the sub is only capable of a 2 ohm load it wont matter how i wire it to the amp it will always be 2 ohm (if wired in parallel) lets just say (so i can get it) a sub is wired to be 8 ohm and i wire it to my amp bridged (sending a 1 ohm load to it) will it be getting the full wattage of the 1 ohm, or will it be getting 8 ohms from my amp (and whatever the watts are that correspond to 8 ohm)

ok your amp does not send ohm loads to the sub.....as you say in your first sentence.

you amp just see's the resistance caused buy the speakers in what ever configuration you put them in series/parallel.

and you said your sub is "capable" of a 2 ohm load........well any sub is really capable of that if you have a DVC sub with each coil @ 4ohm.

so heres the situation, i'll break down the wiring and what your amp will see in said load....


Hook the Pos. side of the amp to one of the Pos. terminals on the sub and the Neg. side of the amp to the opposite side voice coil Neg. terminal then connect the remaining 2 terminals on the sub Neg. and Pos. of opposite coils you will be running series and your amp if you have 2 4ohm coils will be seeing 8ohm.

Now if you hook the Pos. side of the amp to one Pos. side of the sub to the other and do the same for the Neg. side that would be parallel and you will see (with a 4ohm DVC sub) 2ohm at the amp.

thats the best i can put it to get across that the AMP DOES NOT CREATE THE OHM LOAD. hope that helped

[Titano24's]

Originally Posted by Blindside1234

So when i look for a new amp, its kinda like buying a used car the sticker price might seem like a great deal, but if you know nothing about cars, you dont know what your buying, and if you did know about cars you wouldnt buy the car that not only fits your checkbook standards but also the performance standards. So with my sub in mind (12 inch flameQ 1100 watt average power audiobahn wired into 2 ohms with a sealed box) i am not just looking for a 1100 watt (average power) amp im looking for much more, but all those terms were a little over my head. I want to stay at about 250.00 what attributes am i looking for. Not to use the car terminology again, but when purchasing a car dont just look at the sticker price and horsepower , but inspect the engine, trans, mileage, yada yada to insure that u have a quality product. I want an amp that will alow this sub to perform at its peak performance (or near it) instead of telling me what amp and model, please let me know the attributes that makes an amp good, powerful, clean ect. Thanks

well lets stop throwing around the 1100watt sub because that sub will handle no where near that..........and for 250 bucks you won't find an amp giving you 500 true watts, maybe more along the lines of 250 watts, when it comes to amps you will pay on average a dollar per watt any less and its a POS and isn't worth it, now that dollar is on the pretty high side of the range but for a 1000watt amp look to spend 600+, but then look to spend more on a sub once that so called "1100"watt sub frys hehe

[lizardking]

Ohm is a unit of measurment for resistance. Think of resistance like flowing water then you put your hand in the flowing water to slow/disrupt the flow of water.





An analogy for Ohm's Law


All About Circuits > Volume I - DC > Chapter 2: OHM'S LAW > An analogy for Ohm's Law

--------------------------------------------------------------------------------

An analogy for Ohm's Law
Ohm's Law also make intuitive sense if you apply if to the water-and-pipe analogy. If we have a water pump that exerts pressure (voltage) to push water around a "circuit" (current) through a restriction (resistance), we can model how the three variables interrelate. If the resistance to water flow stays the same and the pump pressure increases, the flow rate must also increase.



If the pressure stays the same and the resistance increases (making it more difficult for the water to flow), then the flow rate must decrease:



If the flow rate were to stay the same while the resistance to flow decreased, the required pressure from the pump would necessarily decrease:



As odd as it may seem, the actual mathematical relationship between pressure, flow, and resistance is actually more complex for fluids like water than it is for electrons. If you pursue further studies in physics, you will discover this for yourself. Thankfully for the electronics student, the mathematics of Ohm's Law is very straightforward and simple.

REVIEW:
With resistance steady, current follows voltage (an increase in voltage means an increase in current, and visa-versa).
With voltage steady, changes in current and resistance are opposite (an increase in current means a decrease in resistance, and visa-verse).
With current steady, voltage follows resistance (an increase in resistance means an increase in voltage).

--------------------------------------------------------------------------------

Power in electric circuits
In addition to voltage and current, there is another measure of free electron activity in a circuit: power. First, we need to understand just what power is before we analyze it in any circuits.

Power is a measure of how much work can be performed in a given amount of time. Work is generally defined in terms of the lifting of a weight against the pull of gravity. The heavier the weight and/or the higher it is lifted, the more work has been done. Power is a measure of how rapidly a standard amount of work is done.

For American automobiles, engine power is rated in a unit called "horsepower," invented initially as a way for steam engine manufacturers to quantify the working ability of their machines in terms of the most common power source of their day: horses. One horsepower is defined in British units as 550 ft-lbs of work per second of time. The power of a car's engine won't indicate how tall of a hill it can climb or how much weight it can tow, but it will indicate how fast it can climb a specific hill or tow a specific weight.

The power of a mechanical engine is a function of both the engine's speed and it's torque provided at the output shaft. Speed of an engine's output shaft is measured in revolutions per minute, or RPM. Torque is the amount of twisting force produced by the engine, and it is usually measured in pound-feet, or lb-ft (not to be confused with foot-pounds or ft-lbs, which is the unit for work). Neither speed nor torque alone is a measure of an engine's power.

A 100 horsepower diesel tractor engine will turn relatively slowly, but provide great amounts of torque. A 100 horsepower motorcycle engine will turn very fast, but provide relatively little torque. Both will produce 100 horsepower, but at different speeds and different torques. The equation for shaft horsepower is simple:



Notice how there are only two variable terms on the right-hand side of the equation, S and T. All the other terms on that side are constant: 2, pi, and 33,000 are all constants (they do not change in value). The horsepower varies only with changes in speed and torque, nothing else. We can re-write the equation to show this relationship:



Because the unit of the "horsepower" doesn't coincide exactly with speed in revolutions per minute multiplied by torque in pound-feet, we can't say that horsepower equals ST. However, they are proportional to one another. As the mathematical product of ST changes, the value for horsepower will change by the same proportion.

In electric circuits, power is a function of both voltage and current. Not surprisingly, this relationship bears striking resemblance to the "proportional" horsepower formula above:



In this case, however, power (P) is exactly equal to current (I) multiplied by voltage (E), rather than merely being proportional to IE. When using this formula, the unit of measurement for power is the watt, abbreviated with the letter "W."

It must be understood that neither voltage nor current by themselves constitute power. Rather, power is the combination of both voltage and current in a circuit. Remember that voltage is the specific work (or potential energy) per unit charge, while current is the rate at which electric charges move through a conductor. Voltage (specific work) is analogous to the work done in lifting a weight against the pull of gravity. Current (rate) is analogous to the speed at which that weight is lifted. Together as a product (multiplication), voltage (work) and current (rate) constitute power.

Just as in the case of the diesel tractor engine and the motorcycle engine, a circuit with high voltage and low current may be dissipating the same amount of power as a circuit with low voltage and high current. Neither the amount of voltage alone nor the amount of current alone indicates the amount of power in an electric circuit.

In an open circuit, where voltage is present between the terminals of the source and there is zero current, there is zero power dissipated, no matter how great that voltage may be. Since P=IE and I=0 and anything multiplied by zero is zero, the power dissipated in any open circuit must be zero. Likewise, if we were to have a short circuit constructed of a loop of superconducting wire (absolutely zero resistance), we could have a condition of current in the loop with zero voltage, and likewise no power would be dissipated. Since P=IE and E=0 and anything multiplied by zero is zero, the power dissipated in a superconducting loop must be zero. (We'll be exploring the topic of superconductivity in a later chapter).

Whether we measure power in the unit of "horsepower" or the unit of "watt," we're still talking about the same thing: how much work can be done in a given amount of time. The two units are not numerically equal, but they express the same kind of thing. In fact, European automobile manufacturers typically advertise their engine power in terms of kilowatts (kW), or thousands of watts, instead of horsepower! These two units of power are related to each other by a simple conversion formula:



So, our 100 horsepower diesel and motorcycle engines could also be rated as "74570 watt" engines, or more properly, as "74.57 kilowatt" engines. In European engineering specifications, this rating would be the norm rather than the exception.

REVIEW:
Power is the measure of how much work can be done in a given amount of time.
Mechanical power is commonly measured (in America) in "horsepower."
Electrical power is almost always measured in "watts," and it can be calculated by the formula P = IE.
Electrical power is a product of both voltage and current, not either one separately.
Horsepower and watts are merely two different units for describing the same kind of physical measurement, with 1 horsepower equaling 745.7 watts.

[92TripleBlack]

Don't forget, the lower the Ohm rating you use, the dirtier the sound. Home speakers run on 8 ohm, car 4 ohm. You can go lower, but on anything but a sub, it will sound pretty junky, and subs start becoming more flappy and less tight when run at lower ohms. Cheap way to gain more power at the cost of sound quality.

[grunge311]

In a nutshell.

Your amp probably only puts out 150-200w, really, they lie thru thier teeth and tell you 600w. Its completely normal.

Your sub will fry at the thought of 1100w, it really could handle probably 300, maybe 400w RMS..

The audio industry is known for this, they lie, lie, lie, lie, and lie. Even the most reputable company is guilty of this. The real trick is being able to see thru thier BS.

[Headred15]

Originally Posted by grunge311

In a nutshell.

Your amp probably only puts out 150-200w, really, they lie thru thier teeth and tell you 600w. Its completely normal.

Your sub will fry at the thought of 1100w, it really could handle probably 300, maybe 400w RMS..

The audio industry is known for this, they lie, lie, lie, lie, and lie. Even the most reputable company is guilty of this. The real trick is being able to see thru thier BS.

Also keep in mind, many amps claiming to be stable at 1 ohm, really arent.

[JLTD]

The 1000/1 http://mobile.jlaudio.com/products_amps.php?amp_id=221 will deliver 1000 Watts RMS into an impedance range of 1.5 -4 ohm.
The e1800D http://mobile.jlaudio.com/products_amps.php?amp_id=259 will deliver 800 Watts into a 2 ohm load.