OK guys this is a pretty newbie-ish question, but whatevers. So when you turn up the volume for your subs, does that mean more power (in terms of watts) is going into them? (i.e. if u have a 1200 RMS amp, but u keep the volume low, can u send..oh say...100RMS into the subs?) That leads me to another question about clipping, this happens when a sub is underpowered? If that is the case, then for a a high rms sub, if you turned down the volume too low, would it experience clipping?
Pardon my newbieness guys. Thanks!
Replies (18)
uochronos on 01/5/2004 01:46:14
you should turn your volume on the Head unit to where you normal listen aproxamatly and then turn the gain on the amp up to where you get just a little distortion then back a bit and that should give you just about what you want so its not over powered or under powered. and yes turning volume and gain up and down changes how much voltage is in the mix. voltage times ampage = watts.... thats a really simple way of putting it though Swez ttoc or some of the other golds well probaly have a better way to explain it though.
no matter how far down you turn the gain or volume i dont think the sub would get as little as 100watts from a 1200watt rms amp though i'm not 100% sure.
devastating12s on 01/5/2004 02:15:20
thanks man. Anything on the clipping stuff I asked about? (at low volumes = low watt?)
PS: dont u mean "watts in the mix" isntead of voltage? I'm no electrical engineer, but isn't volatge constant from the battery? Please correct me if im wrong
kiaman on 01/5/2004 02:20:06
everything you asked is totally dependent on your particular system, expect the clipping. clipping occurs when more voltage is pumped into the amp than it is set to handle. therefore it trys to put out more watts. and the tops and bottoms of the signial wave it cut (clipped) off. as for getting 100w out of a 1200w amp...deffiently possible, VxA=W so, how much voltage your HU is putting out to the amp, times how many amppers your amp is drawing from your electrial system. that should equal the wattage. now, if its a class D amp it will be about 80% efficent, so you subtract 20% from W and you have a prety good approximation of how many watts your sub is getting.
Relax_The_Mind on 01/5/2004 05:52:01
In most cases ive seen you get clipped signals from the HU side. Turning the volume way up and it sends the amp/s a clipped signal. Amps amplify everything that it receives on the RCAs (or Speakers level inputs) Head units even today have max volumes of like 50 even though it will start to distort at around ~40-45. Dont ask me why...its an engineering thing.
If you underpower subs it would most likely just not be as loud. Subs dont "pull" power, therefore if you have a 1200w speakers and your only sending it 100w it isnt going to choke from not getting enough power but will sound like you have the volume on like 1 or 2.
RTM
devastating12s on 01/5/2004 14:28:04
OK so let me get this all straight.
If I simply turn down the volume, that means the speaker is receiving less watts.
And about gain, if for instance I set the gain at 7 when HU volume is at 5, then when HU volume is at 6, the gain will be 8 (approx, you get the point). So gain basically is at what HU volume will the subs be receiving what amount of watts. So theoretically it is Ok to run a 3000w RMS amp to a 100w RMS rated sub, if the gain is set properly? (even though ti is a huge waste of the amp's potential)
Munchiesyumm on 01/5/2004 19:59:39
If you run a 3000watt RMS amp on a 100 watt RMS sub it won't even take 30 seconds to melt the cone. With that much power I doubt you could turn the gain down enough.
Kia explained it very well. " VxA=W so, how much voltage your HU is putting out to the amp, times how many amppers your amp is drawing from your electrial system. that should equal the wattage. "
You can do a mathmatical equation to find out how many watts your sub is being sent. When you turn the volume down on the head unit the amplifer is signaled to supply less and less output to the subwoofer.
cplkittle on 01/5/2004 21:08:07
Excellent question..
I have often taken things as truth, and not researched them myself. Most of the time I want to know the hows and whys, and often annoy people who think they know the answer by asking more questions. In this case, I can't answer you completely, but I fully understand what you are asking. I have to leave for work in a few minutes, but when I get home in the morning, I will have a good answer for you if someone else dosen't beat me to it. This is something I have been meaning to research myself.
Don't be afraid to ask anything, some questions, like this one are things that others often wonder about as well.
devastating12s on 01/5/2004 22:14:50
Thanks for all the help guys. cplkittle I look forward to your answer.
Perhaps the 3000w RMS into a 100w speaker was a bad example due to the fact it is too ridiculous. How about A 1200 RM amp into 2x 300RMS speakers (for 600w total). If careufl on the gain, should it be ok?
And any takers on my gain question?:
"if for instance I set the gain at 7 when HU volume is at 5, then when HU volume is at 6, the gain will be 8 (approx, you get the point). So gain basically is at what HU volume will the subs be receiving what amount of watts" True? False?
Munchiesyumm on 01/5/2004 22:24:13
The Definition of gain is:
An increase in signal power, voltage, or current by an amplifier, expressed as the ratio of output to input. Also called amplification.
To clear that up for anyone who did not know the true defintion of the term "gain"
kiaman on 01/5/2004 22:29:51
ok, if you have the gain set at 7, thats a mistake right there, i dont know of any HU that puts out 7v even at max power. most HU's now a days do 4v (at max output) some will do 6. if your HU output is 4v then set your amp to 4v and at max volume you will get the max amount of power from the amp. (This is the majority opnion in car audio) the other opnion is that the gain is just a volume control for the amp. and honstelly, i dont know which one to believe cuz everyone here states the first opnion. altho, when you crank the gain up on the amp, what happens? the subs will go louder. and when the gain is down, the subs will not be as loud. now, if the first opnion was true, then the oppisite would happen. (ex: hu output 4v, gain set at 2v, at half volume the amp should reach max output. and start to clip after that, I have tested this, and it is not the case, so what is the true answer? I honstlley dont know, i have taken swez's and toocs's word for it.)
btw, 1200w amp on 600w subs, is not a good idea, no matter how much you keep the gain down.
swez on 01/5/2004 22:33:58
Same here... will review this post again tomorrow and see what CPL has to say, then add any comments that seem appropriate to clarify the who matter.
A very short form answer... if your HU begins to clip (excess distortions) at say 60% of full power, the signal to the amps will also go in clipped, but come out louder due to gain increases from HU to amp that eventually feeds the subs (or other speakers) GIGO...
There is a tip in the FAQ topic section that explains how to set up your HU and amp gains. Read up and ask more questions if needed.
Here: http://www.clubknowledge.com/Car_Audio_FAQ/?t3
Swez
devastating12s on 01/5/2004 22:52:14
All the number I used weren't actual numbers; they were just there for a relative idea.
Muchiesyumm: " expressed as a ratio of input to output" - this would somewhat fall under the bad example I gave
Why would a 1200RMS amp be bad for 600rms speakers if gain is turned down (whereby max power would be reached at VERY high volumes)?
What the gain knob means exactly at certain settings and certain HU volume is still confusing. Perhaps this will get cleared up int morning....
Munchiesyumm on 01/5/2004 23:07:23
fall under what? I said it wrong?? I spent like a half anout reading about it because I didn't know my self what the actual definition meant but I couldn't find anything to exsactly anwser your question.
by all means if I got a bad source please correct me.
cplkittle on 01/6/2004 11:27:58
Ok, here goes...THINK
First of all, heat is the most common factor in subwoofer damage. This is caused by clipping, or underpowering your sub. Most clipping does occur from your HU. A quality HU that exceeds 25w RMS should not give you this problem, but first let me start from the beginning....
For example, we have one 400w RMS subwoofer. The 400w rating is derived from the mechanical Q (QMS) and the electrical Q (QES). This is the amount of power needed to overcome the mechanical and electrical resistance of the speaker necessary to make it move. When this amount of watts is applied the speaker cone moves freely in and out (excursion). The inward movement pushes air trapped in the dust cover of the speaker out around the voice coils, and likewise when the speaker travels outwardly, this sucks in more air, cooling the voice coil. (duh) I know this is elementary, but I am teaching myself as well here, so bear with me.. If you put a 200w amp on our 400W sub, the watts aren't enough to overcome the Q's of the speaker, and therefore the cone dosen't move as much, and likewise dosen't cool. Two things are going to happen here,
1) the user is going to get pretty peaved and crank up the volume MAD. Since the amplifier can not make the speaker perform, unusually high HU volumes are forced to compensate, giving you clipping.
2) The amplifier is going to try its best to push the maximum watts to the speaker. Since it can't push the necessary watts to move the speaker the distance necessary to provide the air flow to cool the voice coil, and at the same time putting out its maximum power heating up the voice coil further.... you get a thermal overload. Most of the time this melts the insulation on the voice coil windings causing them to contact each other. When this happens, the electricity isn't traveling the distance around the voice coil that it should (it's taking a shortcut). This in turn lowers the resistance of the voice coil, giving you a much lower impedance and damages your amplifier as well.
Ok, on to the million dollar question.... What about volume???
Reducing the volume on the HU does reduce the watts to your subs, and this does decrease sub movement, RELATIVE TO THE AMP POWER. Let's say your HU volume of 10 is telling your 400w RMS amp to operate at 400w. decreasing the volume of your HU by half will decrease the power you are pushing to your speakers by half as well (theoretically) now at a volume of 5 on your HU, your subs are getting 200w. let's turn it down to 2 now.. ok now your subs are getting 80w rms. Now the subs are underpowered, but they are not getting a clipped signal, and the heat generated within the voice coil is relative to the cone movement (figured by the manufacturer using the Q's mentioned earlier).
Let's compare the 200W amp and the 400W amp...
HU volume of 10 200w amp=200w; 400w amp=400w
HU volume of 5 200w amp=100w; 400w amp=200w
HU volume of 2 200w amp=40w; 400w amp= 80w
The only difference at a volume of 10 or below is that with the 200w amp is going to perform at half the volume, only after the volume level of 10 is exceeded (in our example-this is not a set point of reference) will the sub be in danger of overheating.
So, in conclusion, it took me alot longer to explain all of that than it should. GRIN
Running an amp at a lower than RMS rating of the sub will only damage speakers when the volume is turned up past the RMS performance of the amplifier. This is difficult to determine by ear because the max power of the amp can be exceeded without any audible clipping or distortion. So my recommendation is don't do it.
As far as overpowering a sub, I have read from various sources that the RMS rating of a sub is very conservative. Some sources even say that an amplifier rated up to 20-25% higher than the subs is ok. I say use common sense if you do this. And remember, new subs look cool, new hearing aids don't.
devastating12s on 01/6/2004 13:46:31
OK so just to wrap it all up. If I set my maximum amp power at say HU volume 3, then I should never exceed volume 3. Right?
And another question (for you cplkittle), that is based on your explaination (thanks for the helpful info!). Say for instance I have a 1200w RMS amp, and a 600w RMS sub :
1) Now, at HU volume, lets say 10. If I were to set the gain to only halfway, then would the the amp be punping out 600w at HU level 10, which would be ideal for the sub?
or
2) If I were to set the gain to maximun at HU level 20 (assume this level exists), but only listened to my music at HU level 10, would the power to the subs be halved (as u previously stated) and at 600w?
Which one is true? I personally think the 2nd one make more sense based on your explaination. If both are true which one do u recommend?
cplkittle on 01/6/2004 14:09:42
I am just learning myself, and some of the information may not be exact, but I don't think I can tell you in terms of gain levels vs volume how exactly to set your amp.
Most amplifiers have an input sensitivity level, this should be matched to your HU output level (owners manual). If your amp only has gain on it, and with your scenario of a 1200w RMS amp and a 600w RMS sub (which is an example, I know. but I did note that some recommended a max of 25% over RMS-this is 50%) I would say that you have to do it by ear and common sense. Gain levels may not start at 1 and go to 10 in relativity to your HU volume. My amp's input sensitivity level starts at 0.1 and goes to 1.0, but not to scale, the halfway point is 0.3. If you decide to run a 600w RMS sub on a 1200w RMS amp, I would start with 10-15% gain and adjust from the normal listening volume. Never pushing the speaker to distortion or overexcursion.
cplkittle on 01/6/2004 14:42:32
The gain on an amp is not like you are asking, where HU volume is 5 and gain is 7, then HUvolume of 6=gain of 8
The gain setting on an amp is more like a multiplier of signal, not a 'one step above volume constant'.
swez on 01/6/2004 20:36:23
First off, let's define CLIPPING distortion...
This is when an amplifier has reached its maximum output capacity yet tries to keep up with the input signal gain ratio between the signal source "HU" and Amp. The amp hits an imaginary wall whereby the output signal is no longer a symetrical replication of the input signal. The wave form in, does not match the wave form out in shape or amplitude. (you can see this easily if you had a A/B channel oscilloscope; channel A connected to the amp input, channel B to amp output) The only difference you should see between channel A & B are signal amplitude values. If the signal shape varies considerably in channel B, you have a problem with clipping.
So.. what's wrong with this picture? The amp tries to put out the appropriate power, but runs out of voltage from the supply rails and we get a flat spot at the upper and lower peaks of the wave form. In an extreme case, "severe clipping", there is so much additional energy buildup (heat) into the voice coil(s), but the cone does not move (motivate) enough to cool the voice coil and former adequately. Hense, the voice coil over heats and either seizes in the gap or burns the voice coil windings. RESULT: OPEN CIRCUIT and a blown speaker!
OK, what happens to the speakers when they are underpowered? Under normal listening conditions... NOTHING! There is adequate signal voltage from the amplifier to motivate the speaker. This moves the speaker cone and draws/expells air to cool the voice coil adequately. No problems here... just modest output from the speaker. This happens all the time when we ride with the tunes playing low enough to hear our buddy in the co-pilot seat chattering on his/her cell phone.
SO WE CAN USE LOW POWER SAFELY ON SPEAKERS?
Yes... When we use a small amp to drive a high powered speaker, the speaker can take all the "clean power" the amp can deliver and more. But it's when we push the amplifer into high distortion ("clipping") mode, the speaker cannot move (motivate) in and out adequately to cool the voice coil. Eventually, this will even fry a very expensive speaker in this manner.
WELL THEN WISE GUY... WHAT CAUSES THIS "CLIPPING" THING?
Glad you asked! The amp will try to meet the power demand placed upon it, but it cannot exceed its design capabilities. This in turn, produces the deadly "square wave" output to the speaker. The speaker sees this severely clipped signal as something similar to DC current. Speakers cannot deal well with DC inputs. The cone goes in or out and stays there. No motivation to cool the voilce coil and sooner or later, the speaker will fail.
YEAH... YEAH... SO WHAT CAN I DO TO PREVENT THIS?
Alright, we know what clipping is, how it affects amps and speakers. What do we do to keep this problem from destroying our expensive drivers? Easy deal:
1. Use amps that closely match or modestly exceed the power rating of the speaker. A 100 watt speaker will love getting 125 watts of "clean power" vs a 100 watt speaker getting 25 watts of badly clipped (distorted) power.
2. Know what distortion sounds like and prevent it by proper amp setup procedures. (HU/amp gain matching, limited bass boost usage)
3. If you are not sure your system is clipping, best thing to do is get out
of the vehicle, open the doors and step to the rear of the vehicle about 10 feet and listen...
a. Are the highs and mids clear and natural sounding or harsh, shrill and very poor SQ? You are clipping the amp if you hear the latter!
b. Does the bass sound full, tight, have a definite thump and smooth transitions from one note to another? If not, good chance the sub amp is clipping or your enclosure design is not optimal for the subs.
OK, that's about all I can do for now on this topic... Class dismissed and PLEASE... NO CLIPPING ALLOWED !!! 15 yard penalty and you will pay the piper eventually.
Swez HAPPY
Pardon my newbieness guys. Thanks!
Replies (18)
uochronos on 01/5/2004 01:46:14
you should turn your volume on the Head unit to where you normal listen aproxamatly and then turn the gain on the amp up to where you get just a little distortion then back a bit and that should give you just about what you want so its not over powered or under powered. and yes turning volume and gain up and down changes how much voltage is in the mix. voltage times ampage = watts.... thats a really simple way of putting it though Swez ttoc or some of the other golds well probaly have a better way to explain it though.
no matter how far down you turn the gain or volume i dont think the sub would get as little as 100watts from a 1200watt rms amp though i'm not 100% sure.
devastating12s on 01/5/2004 02:15:20
thanks man. Anything on the clipping stuff I asked about? (at low volumes = low watt?)
PS: dont u mean "watts in the mix" isntead of voltage? I'm no electrical engineer, but isn't volatge constant from the battery? Please correct me if im wrong
kiaman on 01/5/2004 02:20:06
everything you asked is totally dependent on your particular system, expect the clipping. clipping occurs when more voltage is pumped into the amp than it is set to handle. therefore it trys to put out more watts. and the tops and bottoms of the signial wave it cut (clipped) off. as for getting 100w out of a 1200w amp...deffiently possible, VxA=W so, how much voltage your HU is putting out to the amp, times how many amppers your amp is drawing from your electrial system. that should equal the wattage. now, if its a class D amp it will be about 80% efficent, so you subtract 20% from W and you have a prety good approximation of how many watts your sub is getting.
Relax_The_Mind on 01/5/2004 05:52:01
In most cases ive seen you get clipped signals from the HU side. Turning the volume way up and it sends the amp/s a clipped signal. Amps amplify everything that it receives on the RCAs (or Speakers level inputs) Head units even today have max volumes of like 50 even though it will start to distort at around ~40-45. Dont ask me why...its an engineering thing.
If you underpower subs it would most likely just not be as loud. Subs dont "pull" power, therefore if you have a 1200w speakers and your only sending it 100w it isnt going to choke from not getting enough power but will sound like you have the volume on like 1 or 2.
RTM
devastating12s on 01/5/2004 14:28:04
OK so let me get this all straight.
If I simply turn down the volume, that means the speaker is receiving less watts.
And about gain, if for instance I set the gain at 7 when HU volume is at 5, then when HU volume is at 6, the gain will be 8 (approx, you get the point). So gain basically is at what HU volume will the subs be receiving what amount of watts. So theoretically it is Ok to run a 3000w RMS amp to a 100w RMS rated sub, if the gain is set properly? (even though ti is a huge waste of the amp's potential)
Munchiesyumm on 01/5/2004 19:59:39
If you run a 3000watt RMS amp on a 100 watt RMS sub it won't even take 30 seconds to melt the cone. With that much power I doubt you could turn the gain down enough.
Kia explained it very well. " VxA=W so, how much voltage your HU is putting out to the amp, times how many amppers your amp is drawing from your electrial system. that should equal the wattage. "
You can do a mathmatical equation to find out how many watts your sub is being sent. When you turn the volume down on the head unit the amplifer is signaled to supply less and less output to the subwoofer.
cplkittle on 01/5/2004 21:08:07
Excellent question..
I have often taken things as truth, and not researched them myself. Most of the time I want to know the hows and whys, and often annoy people who think they know the answer by asking more questions. In this case, I can't answer you completely, but I fully understand what you are asking. I have to leave for work in a few minutes, but when I get home in the morning, I will have a good answer for you if someone else dosen't beat me to it. This is something I have been meaning to research myself.
Don't be afraid to ask anything, some questions, like this one are things that others often wonder about as well.
devastating12s on 01/5/2004 22:14:50
Thanks for all the help guys. cplkittle I look forward to your answer.
Perhaps the 3000w RMS into a 100w speaker was a bad example due to the fact it is too ridiculous. How about A 1200 RM amp into 2x 300RMS speakers (for 600w total). If careufl on the gain, should it be ok?
And any takers on my gain question?:
"if for instance I set the gain at 7 when HU volume is at 5, then when HU volume is at 6, the gain will be 8 (approx, you get the point). So gain basically is at what HU volume will the subs be receiving what amount of watts" True? False?
Munchiesyumm on 01/5/2004 22:24:13
The Definition of gain is:
An increase in signal power, voltage, or current by an amplifier, expressed as the ratio of output to input. Also called amplification.
To clear that up for anyone who did not know the true defintion of the term "gain"
kiaman on 01/5/2004 22:29:51
ok, if you have the gain set at 7, thats a mistake right there, i dont know of any HU that puts out 7v even at max power. most HU's now a days do 4v (at max output) some will do 6. if your HU output is 4v then set your amp to 4v and at max volume you will get the max amount of power from the amp. (This is the majority opnion in car audio) the other opnion is that the gain is just a volume control for the amp. and honstelly, i dont know which one to believe cuz everyone here states the first opnion. altho, when you crank the gain up on the amp, what happens? the subs will go louder. and when the gain is down, the subs will not be as loud. now, if the first opnion was true, then the oppisite would happen. (ex: hu output 4v, gain set at 2v, at half volume the amp should reach max output. and start to clip after that, I have tested this, and it is not the case, so what is the true answer? I honstlley dont know, i have taken swez's and toocs's word for it.)
btw, 1200w amp on 600w subs, is not a good idea, no matter how much you keep the gain down.
swez on 01/5/2004 22:33:58
Same here... will review this post again tomorrow and see what CPL has to say, then add any comments that seem appropriate to clarify the who matter.
A very short form answer... if your HU begins to clip (excess distortions) at say 60% of full power, the signal to the amps will also go in clipped, but come out louder due to gain increases from HU to amp that eventually feeds the subs (or other speakers) GIGO...
There is a tip in the FAQ topic section that explains how to set up your HU and amp gains. Read up and ask more questions if needed.
Here: http://www.clubknowledge.com/Car_Audio_FAQ/?t3
Swez
devastating12s on 01/5/2004 22:52:14
All the number I used weren't actual numbers; they were just there for a relative idea.
Muchiesyumm: " expressed as a ratio of input to output" - this would somewhat fall under the bad example I gave
Why would a 1200RMS amp be bad for 600rms speakers if gain is turned down (whereby max power would be reached at VERY high volumes)?
What the gain knob means exactly at certain settings and certain HU volume is still confusing. Perhaps this will get cleared up int morning....
Munchiesyumm on 01/5/2004 23:07:23
fall under what? I said it wrong?? I spent like a half anout reading about it because I didn't know my self what the actual definition meant but I couldn't find anything to exsactly anwser your question.
by all means if I got a bad source please correct me.
cplkittle on 01/6/2004 11:27:58
Ok, here goes...THINK
First of all, heat is the most common factor in subwoofer damage. This is caused by clipping, or underpowering your sub. Most clipping does occur from your HU. A quality HU that exceeds 25w RMS should not give you this problem, but first let me start from the beginning....
For example, we have one 400w RMS subwoofer. The 400w rating is derived from the mechanical Q (QMS) and the electrical Q (QES). This is the amount of power needed to overcome the mechanical and electrical resistance of the speaker necessary to make it move. When this amount of watts is applied the speaker cone moves freely in and out (excursion). The inward movement pushes air trapped in the dust cover of the speaker out around the voice coils, and likewise when the speaker travels outwardly, this sucks in more air, cooling the voice coil. (duh) I know this is elementary, but I am teaching myself as well here, so bear with me.. If you put a 200w amp on our 400W sub, the watts aren't enough to overcome the Q's of the speaker, and therefore the cone dosen't move as much, and likewise dosen't cool. Two things are going to happen here,
1) the user is going to get pretty peaved and crank up the volume MAD. Since the amplifier can not make the speaker perform, unusually high HU volumes are forced to compensate, giving you clipping.
2) The amplifier is going to try its best to push the maximum watts to the speaker. Since it can't push the necessary watts to move the speaker the distance necessary to provide the air flow to cool the voice coil, and at the same time putting out its maximum power heating up the voice coil further.... you get a thermal overload. Most of the time this melts the insulation on the voice coil windings causing them to contact each other. When this happens, the electricity isn't traveling the distance around the voice coil that it should (it's taking a shortcut). This in turn lowers the resistance of the voice coil, giving you a much lower impedance and damages your amplifier as well.
Ok, on to the million dollar question.... What about volume???
Reducing the volume on the HU does reduce the watts to your subs, and this does decrease sub movement, RELATIVE TO THE AMP POWER. Let's say your HU volume of 10 is telling your 400w RMS amp to operate at 400w. decreasing the volume of your HU by half will decrease the power you are pushing to your speakers by half as well (theoretically) now at a volume of 5 on your HU, your subs are getting 200w. let's turn it down to 2 now.. ok now your subs are getting 80w rms. Now the subs are underpowered, but they are not getting a clipped signal, and the heat generated within the voice coil is relative to the cone movement (figured by the manufacturer using the Q's mentioned earlier).
Let's compare the 200W amp and the 400W amp...
HU volume of 10 200w amp=200w; 400w amp=400w
HU volume of 5 200w amp=100w; 400w amp=200w
HU volume of 2 200w amp=40w; 400w amp= 80w
The only difference at a volume of 10 or below is that with the 200w amp is going to perform at half the volume, only after the volume level of 10 is exceeded (in our example-this is not a set point of reference) will the sub be in danger of overheating.
So, in conclusion, it took me alot longer to explain all of that than it should. GRIN
Running an amp at a lower than RMS rating of the sub will only damage speakers when the volume is turned up past the RMS performance of the amplifier. This is difficult to determine by ear because the max power of the amp can be exceeded without any audible clipping or distortion. So my recommendation is don't do it.
As far as overpowering a sub, I have read from various sources that the RMS rating of a sub is very conservative. Some sources even say that an amplifier rated up to 20-25% higher than the subs is ok. I say use common sense if you do this. And remember, new subs look cool, new hearing aids don't.
devastating12s on 01/6/2004 13:46:31
OK so just to wrap it all up. If I set my maximum amp power at say HU volume 3, then I should never exceed volume 3. Right?
And another question (for you cplkittle), that is based on your explaination (thanks for the helpful info!). Say for instance I have a 1200w RMS amp, and a 600w RMS sub :
1) Now, at HU volume, lets say 10. If I were to set the gain to only halfway, then would the the amp be punping out 600w at HU level 10, which would be ideal for the sub?
or
2) If I were to set the gain to maximun at HU level 20 (assume this level exists), but only listened to my music at HU level 10, would the power to the subs be halved (as u previously stated) and at 600w?
Which one is true? I personally think the 2nd one make more sense based on your explaination. If both are true which one do u recommend?
cplkittle on 01/6/2004 14:09:42
I am just learning myself, and some of the information may not be exact, but I don't think I can tell you in terms of gain levels vs volume how exactly to set your amp.
Most amplifiers have an input sensitivity level, this should be matched to your HU output level (owners manual). If your amp only has gain on it, and with your scenario of a 1200w RMS amp and a 600w RMS sub (which is an example, I know. but I did note that some recommended a max of 25% over RMS-this is 50%) I would say that you have to do it by ear and common sense. Gain levels may not start at 1 and go to 10 in relativity to your HU volume. My amp's input sensitivity level starts at 0.1 and goes to 1.0, but not to scale, the halfway point is 0.3. If you decide to run a 600w RMS sub on a 1200w RMS amp, I would start with 10-15% gain and adjust from the normal listening volume. Never pushing the speaker to distortion or overexcursion.
cplkittle on 01/6/2004 14:42:32
The gain on an amp is not like you are asking, where HU volume is 5 and gain is 7, then HUvolume of 6=gain of 8
The gain setting on an amp is more like a multiplier of signal, not a 'one step above volume constant'.
swez on 01/6/2004 20:36:23
First off, let's define CLIPPING distortion...
This is when an amplifier has reached its maximum output capacity yet tries to keep up with the input signal gain ratio between the signal source "HU" and Amp. The amp hits an imaginary wall whereby the output signal is no longer a symetrical replication of the input signal. The wave form in, does not match the wave form out in shape or amplitude. (you can see this easily if you had a A/B channel oscilloscope; channel A connected to the amp input, channel B to amp output) The only difference you should see between channel A & B are signal amplitude values. If the signal shape varies considerably in channel B, you have a problem with clipping.
So.. what's wrong with this picture? The amp tries to put out the appropriate power, but runs out of voltage from the supply rails and we get a flat spot at the upper and lower peaks of the wave form. In an extreme case, "severe clipping", there is so much additional energy buildup (heat) into the voice coil(s), but the cone does not move (motivate) enough to cool the voice coil and former adequately. Hense, the voice coil over heats and either seizes in the gap or burns the voice coil windings. RESULT: OPEN CIRCUIT and a blown speaker!
OK, what happens to the speakers when they are underpowered? Under normal listening conditions... NOTHING! There is adequate signal voltage from the amplifier to motivate the speaker. This moves the speaker cone and draws/expells air to cool the voice coil adequately. No problems here... just modest output from the speaker. This happens all the time when we ride with the tunes playing low enough to hear our buddy in the co-pilot seat chattering on his/her cell phone.
SO WE CAN USE LOW POWER SAFELY ON SPEAKERS?
Yes... When we use a small amp to drive a high powered speaker, the speaker can take all the "clean power" the amp can deliver and more. But it's when we push the amplifer into high distortion ("clipping") mode, the speaker cannot move (motivate) in and out adequately to cool the voice coil. Eventually, this will even fry a very expensive speaker in this manner.
WELL THEN WISE GUY... WHAT CAUSES THIS "CLIPPING" THING?
Glad you asked! The amp will try to meet the power demand placed upon it, but it cannot exceed its design capabilities. This in turn, produces the deadly "square wave" output to the speaker. The speaker sees this severely clipped signal as something similar to DC current. Speakers cannot deal well with DC inputs. The cone goes in or out and stays there. No motivation to cool the voilce coil and sooner or later, the speaker will fail.
YEAH... YEAH... SO WHAT CAN I DO TO PREVENT THIS?
Alright, we know what clipping is, how it affects amps and speakers. What do we do to keep this problem from destroying our expensive drivers? Easy deal:
1. Use amps that closely match or modestly exceed the power rating of the speaker. A 100 watt speaker will love getting 125 watts of "clean power" vs a 100 watt speaker getting 25 watts of badly clipped (distorted) power.
2. Know what distortion sounds like and prevent it by proper amp setup procedures. (HU/amp gain matching, limited bass boost usage)
3. If you are not sure your system is clipping, best thing to do is get out
of the vehicle, open the doors and step to the rear of the vehicle about 10 feet and listen...
a. Are the highs and mids clear and natural sounding or harsh, shrill and very poor SQ? You are clipping the amp if you hear the latter!
b. Does the bass sound full, tight, have a definite thump and smooth transitions from one note to another? If not, good chance the sub amp is clipping or your enclosure design is not optimal for the subs.
OK, that's about all I can do for now on this topic... Class dismissed and PLEASE... NO CLIPPING ALLOWED !!! 15 yard penalty and you will pay the piper eventually.
Swez HAPPY
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