This was posted on another forum by Alex Lindeman from Elemental Designs and I just thought it was very useful information for those who don't know how to set their gains and crossovers properly (like me.)
Instructional Video Here
This is a Tutorial on proper settings of an amplifiers gain structure.
First a little knowledge on the gain and what it does. A common misconception is that the gain is like a volume knob, or another one is that ½ way equals 50% power, and all the way equals 100%. These are not true, the gain is a level matching device, to allow you to match the signal being sent from your cd player, and create the most amount of power, without clipping which is the cause of distortion and excess heat to the voice coil. With most newer cd players being at least 4 volt outputs or more, there isn’t a need to turn the gains up as high as with, a 2 or even 1 volt RCA preouts. We will show you what clipping sounds like, and what it visually looks like at the end of the presentation.
We will first start with the items needed:
A digital multi meter or DMM , they can be purchased at a Radio Shack, automotive parts store, or Walmart in the automotive department, for usually around $15-20 dollars. The multi meter is a basic trouble shooting device that all 12-volt mobile electronics enthusiasts should have.
A screwdriver, or other device for adjusting the settings on the amp.
A cd with test tones, a 50hz 0-db, for setting of the gain on a sub-woofer amp, and a 150 Hz for setting the gains the other speakers in the vehicle, and then a tone for setting your crossovers. This tone is dependent on where you decide you want your amplifier crossed over at. For example. If you want to low pass your sub-woofers at 80hz. You will need an 80hz 0 db tone. If you want to lowpass them at 65hz, then a 65hz 0 db tone is needed.
Next we will be using a basic formula to figure out where the gain needs to be set.For this you need to know how much power your amplifier is rated at.
We will use a 2 channel nine.2. It is rated at 400 watts by 1 at 4 ohms when bridged.The formula is sq root of Watts x resistance(ohm load)
400 watts by 4 ohm is 1600 then we find the sq root of 1600 which is equal to 40
We now know that 40 volts is equal to 400 watts.
This 40 volts will be found with the DMM.
Now we will begin.
The first step is to turn your cd player on. Then set any boost settings, or eq setting to 0 or flat, turn bass boost or loudness features off.
If your cd player has crossover settings, and you decide to use those over the amplifiers, I suggest you turn those on now. A sub-woofer low pass setting should be no higher than 120hz, we recommend 80hz or lower, depending on listening preference. The high pass on the rest of the speakers in the vehicle should be around the same point as the low pass. For explanation purposes we will use 80hz today.
If you have more than one amp in the vehicle, I recommend you unhook the amps not being set. This will prevent any damage to the other speakers in the vehicle.
The next step is to go to the amplifier and set the x over setting to full. If using a mono block amp such as a nine, turn the crossover all the way up so it does not affect the signal.
Then proceed to make sure the gain is turned all the way down.
You will then hook the DMM up to the speaker terminals with the speaker wire in them, one in the positive one in the negative. You will keep the speakers connected during the process.
The dmm will need to be turned on, and set to voltage ac, your DMM owners manual should explain to you where voltage AC is at. As for the number settings, you will want to have the decimal place at a hundredth, for example 00.00
Since we are testing the nine.2 bridged for a sub-woofer. I will be using the 50hz tone. If setting the gain for upper frequency drivers the 150hz tone will be used.
Insert the tone cd and then proceed to turn the cd player volume to 75%. If using stock speakers running off the cd player, then turn it up to where they start to distort, and then down a little bit.
Turn the 0 db 50hz tone onto repeat.
With the DMM running, slowly turn the gains up, you will notice the voltage increase, slowly turn the gain up until 40 volts is reached.
With the 40volts being reached the speaker is seeing 400 watts. You can then stop the tone and turn the cd player down.
Now if you are using the amplifiers crossovers, we will be setting these now. Since we have a sub-woofer hooked up, we will turn the crossover to Low pass filter, or LPF. The LPF dial will then be turned all the way up. Since we decided to cross the sub over at 80 Hz, we will throw the 80hz tone into the cd player, we will then turn the volume up a little bit, so the sub is noticeable, no need to be turned up all the way. Put on repeat.
The LPF dial will be slowly turned down until the sub-woofer starts to not play the tone with the intensity it did before, The sub-woofer will not stop completely playing the tone, but it will get quieter. You will then slightly turn the crossover back until the speaker is playing with all intensity again. You are then crossed over around 80hz.
The same goes for a other speakers playing your upper frequency range, only you will want to set the amp to high pass filter or HPF, and use the HPF dial.
Now that your gain and crossover is set properly the chance of damaging your speaker and amps is cut significantly, but you need to remember, a lot of music today is recorded with clipping, so you still need to be careful and watch for signs of driver stress.
How to Set Gains and Crossovers on an Amplifier
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Looneybomber
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Re: How to Set Gains and Crossovers on an Amplifier (phuphyter)
That's missleading. A speaker does not maintain a constant ohm rating throughout it's playing spectrum. Depending on MANY factors, the resistance at 80hz could be anywhere from 4.5ohm to 25ohms, maybe even higher.
*see pic* All are 4ohm speakers. Ohms on the left, hz on the bottom.
Let's say at 80hz, the impedence of that driver is 12ohms.400 * 12 = 4800 sqrt = 69.28v.If you set that amps gain to produce 40v, instead of getting 400w of power, you're now getting 231w, 57% of what that amp could do. You're wasting a lot of money since you're not utilizing all your available power.
Ideally, you should set your gains according to THD (Total Harmonic Distortion) which is easily measureable, but can get fairly expensive buying all the equipment. You can then use your ears, when you hear your subs distorting, turn the gain down a tad. Simple.
What you could do to atleast more perfect the process would be to switch your DMM (digital multi meter) to AC resistance, play your 80hz test tone and see how many ohms you have. You then use that number for the rest of your tuning.
THings to take into account, some cheap amps are over-rated at ungodly rediculous wattages. If you try to take their huge 1000w or 2000w peak numbers, you'll turn your gains waay too far up trying to reach the calculated voltage and blow your subs due to all the distortion. Another thing to think about are underrated amps. My MTX2300x amp is rated at 150x2 at 4ohm 20-20k. It's birth sheet says it will do 201x2 at 4ohm at either .5 or 1% THD (I forget which one). So I could then use 200w instead of 150w and utilize all of my amps power.
My .02ED has a few idiots that work there, mainly their owners. I've read many of their posts on their forum. They continually misspell words and use the incorrect "there" and "to". When it comes to getting technical, they don't know the nitty-gritty physics behind how a speaker works even though they design them?
Like why didn't they mention that a speaker does not maintain a constant impedence throughout it's aural spectrum?
So how does one trust someone that can neither spell nor explain in detail how their products work. I've bought one of their 19Ov.2's and will likely not buy another ED product again. If I get another sub driver, it will be from TCSounds.com
*edit* Fixed a spelling mistake.
Modified by Looneybomber at 4:20 AM 2/7/2007
*see pic* All are 4ohm speakers. Ohms on the left, hz on the bottom.
Let's say at 80hz, the impedence of that driver is 12ohms.400 * 12 = 4800 sqrt = 69.28v.If you set that amps gain to produce 40v, instead of getting 400w of power, you're now getting 231w, 57% of what that amp could do. You're wasting a lot of money since you're not utilizing all your available power.
Ideally, you should set your gains according to THD (Total Harmonic Distortion) which is easily measureable, but can get fairly expensive buying all the equipment. You can then use your ears, when you hear your subs distorting, turn the gain down a tad. Simple.
What you could do to atleast more perfect the process would be to switch your DMM (digital multi meter) to AC resistance, play your 80hz test tone and see how many ohms you have. You then use that number for the rest of your tuning.
THings to take into account, some cheap amps are over-rated at ungodly rediculous wattages. If you try to take their huge 1000w or 2000w peak numbers, you'll turn your gains waay too far up trying to reach the calculated voltage and blow your subs due to all the distortion. Another thing to think about are underrated amps. My MTX2300x amp is rated at 150x2 at 4ohm 20-20k. It's birth sheet says it will do 201x2 at 4ohm at either .5 or 1% THD (I forget which one). So I could then use 200w instead of 150w and utilize all of my amps power.
My .02ED has a few idiots that work there, mainly their owners. I've read many of their posts on their forum. They continually misspell words and use the incorrect "there" and "to". When it comes to getting technical, they don't know the nitty-gritty physics behind how a speaker works even though they design them?
Like why didn't they mention that a speaker does not maintain a constant impedence throughout it's aural spectrum?
So how does one trust someone that can neither spell nor explain in detail how their products work. I've bought one of their 19Ov.2's and will likely not buy another ED product again. If I get another sub driver, it will be from TCSounds.com
*edit* Fixed a spelling mistake.
Modified by Looneybomber at 4:20 AM 2/7/2007
You, PMQ, Audatious, and all the other audiophiles evidently know waaaay more than I do. I'm not saying what he posted is the absolute law or anything.
I never knew that the impedence changes at different hertz and your explanation makes total sense! So you take the impedence reading at the point you want to crossover at, then use that for the rest of the tuning, right?
Okay, what if the impedence is not a perfect parabola, like the blue (or is it purple? Sorry, I'm colorblind haha) line. It has two peaks. If you were to set the gain to receive max watts at 80hz, you'd use 32 ohms in your calculations, right?
Now what would happen when the speaker tries to play a 30hz tone? That creates an impedence of only 4 ohms. Would that cause any problems like too much power, or would it not be affected at all?
I know it's hard to explain, but what does distortion/ clipping sound like? _______________________________________ It's not my place to start an argument over the internet, but I'd like to see what they have to say to your correction on setting the gains on an amp. You ever think about posting it?
And I'd like to hear your review of the 19Ov.2 especially since it's coming from outside the ED forums, know what I mean? People often get caught up in the hype and start to have placebo effects based on what they read on the internet and/or don't have enough experience to make a legit comparison/review.
I never knew that the impedence changes at different hertz and your explanation makes total sense! So you take the impedence reading at the point you want to crossover at, then use that for the rest of the tuning, right?
Okay, what if the impedence is not a perfect parabola, like the blue (or is it purple? Sorry, I'm colorblind haha) line. It has two peaks. If you were to set the gain to receive max watts at 80hz, you'd use 32 ohms in your calculations, right?
Now what would happen when the speaker tries to play a 30hz tone? That creates an impedence of only 4 ohms. Would that cause any problems like too much power, or would it not be affected at all?
I know it's hard to explain, but what does distortion/ clipping sound like? _______________________________________ It's not my place to start an argument over the internet, but I'd like to see what they have to say to your correction on setting the gains on an amp. You ever think about posting it?
And I'd like to hear your review of the 19Ov.2 especially since it's coming from outside the ED forums, know what I mean? People often get caught up in the hype and start to have placebo effects based on what they read on the internet and/or don't have enough experience to make a legit comparison/review.
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Looneybomber
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Re: (phuphyter)
I'm not currently looking at that picture, but if it says 32ohms, then you would use that instead of 4ohms.phuphyter wrote:Okay, what if the impedence is not a perfect parabola, like the blue (or is it purple? Sorry, I'm colorblind haha) line. It has two peaks. If you were to set the gain to receive max watts at 80hz, you'd use 32 ohms in your calculations, right?
Oh wow, why do I get into technical stuff at nearly 6am. My thinking isn't clear. Yes, sorry you will run in to problems. Setting it up like I explained is what you'd do for SPL drags where you play a "burp" tone. If you read what I wrote, you will also notice poor sentence structures, inconsistancies in terminology and misspelled words. Please forgive me.phuphyter wrote: Now what would happen when the speaker tries to play a 30hz tone? That creates an impedence of only 4 ohms. Would that cause any problems like too much power, or would it not be affected at all?
What you would do is find the minimum impedence through your audio range. For example if you had a sub-sonic filter at 30hz and a lowpass at 80hz, you'd find the minimum between those frequencies and use that value. It might be 4ohms, it might be 5.2ohms.
Like poo. How do you explain what poo smells like? It just smells like poo. Same with distortion. You will hear one thing, then it will suddenly change and not sound the same. That is distortion. You may preceive it as an inaccuracy in the sound, a warble, or even a thwacking sound as your speaker bottoms out. They're all bad.phuphyter wrote: I know it's hard to explain, but what does distortion/ clipping sound like?
ED doesn't like me since I think their home audio stuff is mediocre and have deleted some of my threads before. There's nothing special about their HT products so I rank it up there with some low priced DIY projects. Oh hum.phuphyter wrote: It's not my place to start an argument over the internet, but I'd like to see what they have to say to your correction on setting the gains on an amp. You ever think about posting it?
At their current full price of 300.00 shipped, it's not worth it. Sure it will make some big sound, but that's because it's a big driver. What I bought it for was to move lots of air. In order to make lots of low/infrasonic bass, you need to move lots of air! That can be done with high amounts of xmax (excursion) and/or lots of cone surface area (SD). In other words, a few small drivers or one big driver. I opted for the single large driver.phuphyter wrote: And I'd like to hear your review of the 19Ov.2 especially since it's coming from outside the ED forums, know what I mean? People often get caught up in the hype and start to have placebo effects based on what they read on the internet and/or don't have enough experience to make a legit comparison/review.
Depending on what you're wanting to do, the 19Ov.2 might be for you, but I highly doubt it. For the money, invest in another speaker(s). I got mine for 1/2 price or I wouldn't have bought it.
Looney,
Bring me up to speed on what you are referring to as "AC resistance". I've been in mobile electronics for nearly 20 years, worked with component level electronics, I've owned many DMM's of varying quality levels, and I have owned several oscilloscopes, etc. etc. Never heard of an "AC resistance" setting on any of my test equipment. It's been my understanding since electronics in high school that you cannot measure resistance while the circuit being tested is under power. This is because the ohms setting on all ohmmeters provides it's own power to the circuit being tested to allow it to measure the circuits resistance.
I'm not saying you are wrong, just never heard of that. There are many instances where I'd like to be able to measure resistance while a circuit is under power so if you can confirm that procedure I'd appreciate it. If you were mistaken in that suggestion lets clarify that so we don't have someone fry their DMM trying to measure resistance while they are powering their circuit.
Bring me up to speed on what you are referring to as "AC resistance". I've been in mobile electronics for nearly 20 years, worked with component level electronics, I've owned many DMM's of varying quality levels, and I have owned several oscilloscopes, etc. etc. Never heard of an "AC resistance" setting on any of my test equipment. It's been my understanding since electronics in high school that you cannot measure resistance while the circuit being tested is under power. This is because the ohms setting on all ohmmeters provides it's own power to the circuit being tested to allow it to measure the circuits resistance.
I'm not saying you are wrong, just never heard of that. There are many instances where I'd like to be able to measure resistance while a circuit is under power so if you can confirm that procedure I'd appreciate it. If you were mistaken in that suggestion lets clarify that so we don't have someone fry their DMM trying to measure resistance while they are powering their circuit.
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PoorManQ45
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Re: (qsiguy)
He improperly stated the setting.qsiguy wrote:Looney,This is because the ohms setting on all ohmmeters provides it's own power to the circuit being tested to allow it to measure the circuits resistance.
What you actually need is an amp meter.
Play the frequency. Measure the voltage and the amps. There you go. YOu now have the impedance at that frequency.
It is possible to test the resistance in an active circuit. Here's how:
Take a Resistor of whatever ohms you'd like, preferably close to the impedance you think the circuit is at. Lets say 8 ohms.
Put that resistor in on the amplifier, and play the frequency you're aiming to test.
Measure the voltage.
Then remove the resistor and hook the speaker back up. don't change ANYTHING else.
Then test the voltage.
There you go. You have a base and a variable. Basic algebra will tell you the other impedance.
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PoorManQ45
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Re: How to Set Gains and Crossovers on an Amplifier (Looneybomber)
Looney! Do I have to explain this again!?!Looneybomber wrote:you'll turn your gains waay too far up trying to reach the calculated voltage and blow your subs due to all the distortion.
Distortion does not cause ANY problems. POWER is what causes problems.
The problems lies in that people associate clipping with distortion.
When clipping occurs the power output more the doubles! This is what will kill the speaker
Thanks for that explanation PoorMan. I am familiar with ohms law and how to calculate those figures but I never thought of that method of checking a speaker output. Actually I never needed to as I usually wire the output to my o-scope which makes it simple to determine the power output. What I was referring to wanting to measure resistance in a powered circuit was actually in a PCB checking for defective parts.
So phuphyter, don't try to use your resistance setting on your DMM on your speaker outputs when your amp is on. Use the AC Amperage setting and install your DMM in series with your speaker and take an amperage reading. Then with the amp settings the same, check the voltage on the output using the AC volts setting and take a reading. Better yet, if you have 2 DMM's you can wire them both at the same time and get both readings at once.
Using ohms law you can determine the resistance of the speaker. For example if you have 20 volts and 2 amps the formula is 20/2=10 ohms at that frequency.
So phuphyter, don't try to use your resistance setting on your DMM on your speaker outputs when your amp is on. Use the AC Amperage setting and install your DMM in series with your speaker and take an amperage reading. Then with the amp settings the same, check the voltage on the output using the AC volts setting and take a reading. Better yet, if you have 2 DMM's you can wire them both at the same time and get both readings at once.
Using ohms law you can determine the resistance of the speaker. For example if you have 20 volts and 2 amps the formula is 20/2=10 ohms at that frequency.
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PoorManQ45
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For a PCB it should be even easier.
You should already know what the resistance should be!
You should know the voltage going into the circuit also. Therefore you know the amperage.
Check the amperage. If it's out of the normal tolerance range of a few % then something is wrong.
Now, to find out exactly what is wrong is a little trickier.
BTW, most cheap DMM don't have an amp meter. Usually has to be a >$50 model.
Also, some DMMs need to be wired in series. But some are wired in parallel and use a shunt to test the amperage
You should already know what the resistance should be!
You should know the voltage going into the circuit also. Therefore you know the amperage.
Check the amperage. If it's out of the normal tolerance range of a few % then something is wrong.
Now, to find out exactly what is wrong is a little trickier.
BTW, most cheap DMM don't have an amp meter. Usually has to be a >$50 model.
Also, some DMMs need to be wired in series. But some are wired in parallel and use a shunt to test the amperage
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PoorManQ45
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Re: How to Set Gains and Crossovers on an Amplifier (PoorManQ45)
Clipping can occur anytime the output signal voltage is greater than supply voltage at a given frequency. Clipping is more based off voltage rather than power or amperage.PoorManQ45 wrote:
Looney! Do I have to explain this again!?!
Distortion does not cause ANY problems. POWER is what causes problems.
The problems lies in that people associate clipping with distortion.
When clipping occurs the power output more the doubles! This is what will kill the speaker
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PoorManQ45
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That is correct.
The thing is is that a clipped signal sends out the equivolent of ~2.5~3 times the amount of power as a sine wave!
This is what kills speakers and causes the distortion that so many people think is killing their speakers.
Also, a power supply will do neat things when you try to draw more power then it is meant to supply.
They will all eventually shut off, but before that their behavior becomes erradict. This is where that 2.5~3 times the power comes from. It isn't constant, but it's long enough to do damage if the VC can't handle the power.
The thing is is that a clipped signal sends out the equivolent of ~2.5~3 times the amount of power as a sine wave!
This is what kills speakers and causes the distortion that so many people think is killing their speakers.
Also, a power supply will do neat things when you try to draw more power then it is meant to supply.
They will all eventually shut off, but before that their behavior becomes erradict. This is where that 2.5~3 times the power comes from. It isn't constant, but it's long enough to do damage if the VC can't handle the power.
Re: (PoorManQ45)
I dont think thats true (the clipped sine wave sending out 2.5-3x more power).
When the output signal voltage is more than the supply votage (having the gain set too high), the op amp of the circuit cuts off the top of the sine wave, so the maximum voltage is under the supply votage of that given frequency. The signal is so deformed now, the speaker trying to play it has a very hard time reproducing it, leading it to blow.
The power spike you speak of isnt really there. Its just a very impure signal. Although, the higher the volume of the stereo, the better the chance of you blowing the speaker.
When the output signal voltage is more than the supply votage (having the gain set too high), the op amp of the circuit cuts off the top of the sine wave, so the maximum voltage is under the supply votage of that given frequency. The signal is so deformed now, the speaker trying to play it has a very hard time reproducing it, leading it to blow.
The power spike you speak of isnt really there. Its just a very impure signal. Although, the higher the volume of the stereo, the better the chance of you blowing the speaker.
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PoorManQ45
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Ok, sorry about that. I just checked my info again.
You are correct that the supply voltage cannot be exceeded.
What I meant was that when the amplifier clips audio energy is added to the higher frequencies which can push the output in the treble to the limits of the amp. If the amp is powerful enough, this could damage your tweeters.
Sorry about that.
Good catch
You are correct that the supply voltage cannot be exceeded.
What I meant was that when the amplifier clips audio energy is added to the higher frequencies which can push the output in the treble to the limits of the amp. If the amp is powerful enough, this could damage your tweeters.
Sorry about that.
Good catch
I'll add my $.02 to the clipping subject. You've all described clipping correctly as a cutting off of the top and bottom of the sine wave but what you get when the top and bottom are cut off is DC instead of AC and it's like wiring your speaker directly to a battery. You are not getting a spike, you are sending DC current to your speaker instead of a smooth AC signal.
Clipping is what the amp output does when the amp is overdriven, distortion is what the speaker does when it received either a clipped signal or is overdriven with too much power.
Clipping is what the amp output does when the amp is overdriven, distortion is what the speaker does when it received either a clipped signal or is overdriven with too much power.
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Looneybomber
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Re: (qsiguy)
I know AC resistance is wrong, but is very close to what I meant to say. Resistance, not AC resistance.qsiguy wrote:Never heard of an "AC resistance" setting on any of my test equipment.
Clipping is a form of distortion. I lump it all together to be more simple.PoorManQ45 wrote:Looney! Do I have to explain this again!?!Distortion does not cause ANY problems. POWER is what causes problems.
You beat me.qsiguy wrote:but what you get when the top and bottom are cut off is DC instead of AC .
Re: (Looneybomber)
Please explain that one.Looneybomber wrote:
Clipping is a form of distortion. I lump it all together to be more simple.
Re: (qsiguy)
The signal is still AC after its been clipped. For example if the amp is sending out a 60hz signal, and it gets clipped, its still sending out a varied 60hz signal 60 times a second, which isnt DC. The resulting clipped wave may sort of look like a DC, but its just an impure AC signal.qsiguy wrote:I'll add my $.02 to the clipping subject. You've all described clipping correctly as a cutting off of the top and bottom of the sine wave but what you get when the top and bottom are cut off is DC instead of AC and it's like wiring your speaker directly to a battery. You are not getting a spike, you are sending DC current to your speaker instead of a smooth AC signal.
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PoorManQ45
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A clipped signal is still AC.
The problem is that the wave gets near to a square wave. This is bad because to reproduce the wave the driver must accelerate infinitely fast outwards, then hold still, the accelerate infinitely fast inwards, then hold, etc...
This causes the speaker to sound distorted.
A amplifier should NEVER send a true DC current to the speakers. If it does then something has broken internally on the amp
The problem is that the wave gets near to a square wave. This is bad because to reproduce the wave the driver must accelerate infinitely fast outwards, then hold still, the accelerate infinitely fast inwards, then hold, etc...
This causes the speaker to sound distorted.
A amplifier should NEVER send a true DC current to the speakers. If it does then something has broken internally on the amp
Re: (PoorManQ45)
WordPoorManQ45 wrote:A clipped signal is still AC.
The problem is that the wave gets near to a square wave. This is bad because to reproduce the wave the driver must accelerate infinitely fast outwards, then hold still, the accelerate infinitely fast inwards, then hold, etc...
This causes the speaker to sound distorted.
A amplifier should NEVER send a true DC current to the speakers. If it does then something has broken internally on the amp
Clipping, distortion and related tendancies
I new but let me jump right in!What blows speakers is "power over time".
A speaker is a "dumb" device. It is also mechanically inefficient, only converting approximately 5% of the energy it receives into sound. The rest is dissipated as heat.
If a speaker is capable of handling 300 watts then it doesn't matter if it is 300 watts of pure clipped distortion or an unclipped audio signal. Watt is a measurement of heat therefore there is no such thing as distorted heat.
There are two types of power handling in reference to loudspeakers; thermal and mechanical.
Thermal power handling, as you might guess, is the speakers ability to function with "x" amount of wattage or heat being sent to it. Typical failures would be glue joint failure(from heat) or a burnt voice coil(not a manufacturing defect). Burnt voice coils are from excessive power, PERIOD. An over powered or burnt voice coil is totally black indicating excessive heat(easily created by plugging a speaker into the wall outlet). This type of ABUSE is easily diagnosed.
Mechanical power handling is the speakers range to physically move with audio input and not have a mechanical failure such as torn spiders, torn surrounds, neck joint failure (the point where the voice coil, spider and cone body attach), torn tinsel leads (the little wires that connect the speaker wire terminal to the voice coil). Also encountered could be a combination of mechanical and thermal. As a speaker reaches it's excursion limits, the entire cone and voice coil assembly can "rock" or tilt inside the speaker frame. If this happens the voice coil can rub against the pole piece of the motor assembly and cause localized damage to the voice coil. Think of a mechanical failure as operating well above red line, sooner or later something is going to fly apart.
A speaker is a "dumb" device. It is also mechanically inefficient, only converting approximately 5% of the energy it receives into sound. The rest is dissipated as heat.
If a speaker is capable of handling 300 watts then it doesn't matter if it is 300 watts of pure clipped distortion or an unclipped audio signal. Watt is a measurement of heat therefore there is no such thing as distorted heat.
There are two types of power handling in reference to loudspeakers; thermal and mechanical.
Thermal power handling, as you might guess, is the speakers ability to function with "x" amount of wattage or heat being sent to it. Typical failures would be glue joint failure(from heat) or a burnt voice coil(not a manufacturing defect). Burnt voice coils are from excessive power, PERIOD. An over powered or burnt voice coil is totally black indicating excessive heat(easily created by plugging a speaker into the wall outlet). This type of ABUSE is easily diagnosed.
Mechanical power handling is the speakers range to physically move with audio input and not have a mechanical failure such as torn spiders, torn surrounds, neck joint failure (the point where the voice coil, spider and cone body attach), torn tinsel leads (the little wires that connect the speaker wire terminal to the voice coil). Also encountered could be a combination of mechanical and thermal. As a speaker reaches it's excursion limits, the entire cone and voice coil assembly can "rock" or tilt inside the speaker frame. If this happens the voice coil can rub against the pole piece of the motor assembly and cause localized damage to the voice coil. Think of a mechanical failure as operating well above red line, sooner or later something is going to fly apart.
Re: Clipping, distortion and related tendancies (AudioGod)
Let me introduce the term "crest factor".
This is the difference in the audio signal (using amplifier output for the purpose of this discussion) between average amplitude and maximum amplitude aka average volume vs. maximum volume. Since we are dealing with an audio signal, all we are looking at is the sine wave, either as AC voltage, decibels, etc.
We will speak referring to this AC voltage as db from here.
Ever wonder why some songs you could turn WIDE OPEN and they still sounded great(Dire Straits, Money for Nothing)? Recored in the 80's and the engineers were all excited about the dynamic range of this new thing called the CD.
The reason is that this particular track has a crest factor of about 20db. This means that the average db and the maximum db of this track is 20db apart. If we understand Ohm's Law, we know that it takes an exponential increase in power to gain 20 db of signal.
Look at some current music; Evanescence, Going Under and Godsmack, Awake.Each other these songs have a crest factor somewhere around 8 or 9 db.
The reason for this is twofold; today, most music is played back on junk. Headphones, boom box in a kids room, TV speakers, or crappy car stereo, etc. The music is actually mastered by the recording engineer to be "hot". By doing so, it "sounds" better on these playback systems.This problem is exacerbated by music compression, MP3, AAC, WMA and other types of music compression.
A square wave has a crest factor of 3db. In other words, the average with a square wave, which is essentially wide open or off, is only 3db and if we remember, 3db is approximately the minimum increase in volume that the human ear can discern.
I hope this helps.
This is the difference in the audio signal (using amplifier output for the purpose of this discussion) between average amplitude and maximum amplitude aka average volume vs. maximum volume. Since we are dealing with an audio signal, all we are looking at is the sine wave, either as AC voltage, decibels, etc.
We will speak referring to this AC voltage as db from here.
Ever wonder why some songs you could turn WIDE OPEN and they still sounded great(Dire Straits, Money for Nothing)? Recored in the 80's and the engineers were all excited about the dynamic range of this new thing called the CD.
The reason is that this particular track has a crest factor of about 20db. This means that the average db and the maximum db of this track is 20db apart. If we understand Ohm's Law, we know that it takes an exponential increase in power to gain 20 db of signal.
Look at some current music; Evanescence, Going Under and Godsmack, Awake.Each other these songs have a crest factor somewhere around 8 or 9 db.
The reason for this is twofold; today, most music is played back on junk. Headphones, boom box in a kids room, TV speakers, or crappy car stereo, etc. The music is actually mastered by the recording engineer to be "hot". By doing so, it "sounds" better on these playback systems.This problem is exacerbated by music compression, MP3, AAC, WMA and other types of music compression.
A square wave has a crest factor of 3db. In other words, the average with a square wave, which is essentially wide open or off, is only 3db and if we remember, 3db is approximately the minimum increase in volume that the human ear can discern.
I hope this helps.
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PoorManQ45
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- Joined: Fri Jul 02, 2004 5:13 pm
Nice post.
What is so dangerous about a square wave is that the VC's power handling(thermal) is rated with the cone moving. On almost every speaker the cone movement is used as a cooling mechanism.
With a square wave the cone goes out, holds, comes in, holds.
With a sine it is constantly moving.
With the square wave since it's holding there are a bunch of momentary pauses in the cooling from air movement. If left long enough this will cause the speaker to be damaged, even if the rated thermal power level is not exceeded!
If the speaker is thermally rated to 300w RMS and you run a square wave through it at ~275w RMS more then likely you will kill the speaker
What is so dangerous about a square wave is that the VC's power handling(thermal) is rated with the cone moving. On almost every speaker the cone movement is used as a cooling mechanism.
With a square wave the cone goes out, holds, comes in, holds.
With a sine it is constantly moving.
With the square wave since it's holding there are a bunch of momentary pauses in the cooling from air movement. If left long enough this will cause the speaker to be damaged, even if the rated thermal power level is not exceeded!
If the speaker is thermally rated to 300w RMS and you run a square wave through it at ~275w RMS more then likely you will kill the speaker
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Looneybomber
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10 G37S (white)
Re: (scole)
dis·tort /dɪˈstɔrt/ Pronunciation Key - Show Spelled Pronunciation[di-stawrt] Pronunciation Key - Show IPA Pronunciation –verb (used with object) 1. to twist awry or out of shape; make crooked or deformed: Arthritis had distorted his fingers. 2. to give a false, perverted, or disproportionate meaning to; misrepresent: to distort the facts. 3. Electronics. to reproduce or amplify (a signal) inaccurately by changing the frequencies or unequally changing the delay or amplitude of the components of the output wave.scole wrote:Please explain that one.
Is the source signal being reproduced accurately by the amp at clipping? No. The amplitude is effected, thus it's distorted.
For an very small period of time, the current is not alternating, physically speaking, the cone stops moving and maintains a position. To do that it must have a direct current flowing to it to hold it at that position for maybe only .01 seconds, but on a short enough timeline, it would still be DC.scole wrote:The signal is still AC after its been clipped. For example if the amp is sending out a 60hz signal, and it gets clipped, its still sending out a varied 60hz signal 60 times a second, which isnt DC. The resulting clipped wave may sort of look like a DC, but its just an impure AC signal.
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PoorManQ45
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Re: (Looneybomber)
Theoretically this is correct, but in practice that is not how it goes.Looneybomber wrote:For an very small period of time, the current is not alternating, physically speaking, the cone stops moving and maintains a position. To do that it must have a direct current flowing to it to hold it at that position for maybe only .01 seconds, but on a short enough timeline, it would still be DC.