# best amount of power to... well power subs, help me deal with my friend



## ScaryfatkidGT (Mar 31, 2012)

So everyone knows you can blow a sub by underpowering it by constantly clipping the amp but he seems to think that if you over power a sub it WILL blow so he was throwing out all of these amps that put out a little to much or more than stated power (like the Rockford T1500bdCP puts out like 1780w or something like that).

Told him if you set the gains right your fine but some just told him that gain is just sensitivity and watts are watts, so I'm like ok just turn the volume down if you hear distortion but he didn't believe me and was telling me the voice coil would overheat even without distortion present.... what's the truth? Is it really that touchy?

I have heard tons of stuff; more power is better, the 75%-125% or the 75%-150% rule and that you "should" over power stuff by like 10% for optimal performance.

The 2 examples that were pissing me off was the T1500bd on my 2 JL W3v3's that are 1200w rms @2ohm combined, he said not to do and they would blow and then he was looking at getting a T2500bdCP for 2 T2's and some guy at a shop told him he would blow them up right away, because it is like actually 2800w or something and I was trying to tell him that is at 14.4v, its more like 13.8 and not even that once you run through the 8' of 1/0awg wire to the amp so it would work and overpowering 1000w rms subs by 300ish watts each is fine.

Whats right? aren't hi end stuff like T2's meant to take more abuse? I wouldn't run 500 watts rms into a cheap 300w rms sub but talking W7's and T1/2's I didn't think it would be an issue.


----------



## ATOMICTECH62 (Jan 24, 2009)

*Re: best amount of power to... well power subs, help me deal with myy friend*

I wouldnt put that 2500 on 2 T2's.It will toast them if he isnt carefull.
Subs and power are a touchy subject.Basically,the harder you push them the shorter their life span.But kid driving around pounding subs all day can kill a decent sub with too little power.Hard clipping is basically driving them with a square wave.This is where heat kills them.Try matching them up to an amp with similar power ratings,set the gains correctly and things should be fine.


----------



## ScaryfatkidGT (Mar 31, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*



ATOMICTECH62 said:


> I wouldnt put that 2500 on 2 T2's.It will toast them if he isnt carefull.
> Subs and power are a touchy subject.Basically,the harder you push them the shorter their life span.But kid driving around pounding subs all day can kill a decent sub with too little power.Hard clipping is basically driving them with a square wave.This is where heat kills them.Try matching them up to an amp with similar power ratings,set the gains correctly and things should be fine.


Yeah I'm not talking about clipping because that will kill them regardless of the amps power. Aren't highend stuff like T2's and W7's made to pound all day?

And what do you run 2 T2's with then? 2 T1000bdCP's? even that is 395w over powered at 1ohm, I guess you could get 2ohm subs and run them both at 2ohm's?

So with my subs I have an MRP M1000 and its dumb and get's really hot and then it doesn't hit as hard (pretty sure it would be better off at 4 ohms than the 2 I have it at) so I want a better amp, would the T100bdCP work? Rockford says it puts out 1299w at 2ohm dynamic power, whats that mean? but if I just look at the 1000w rms at 2ohm rating then I would want more.

Other wise I was thinking the PDX M12 or a JL amp, or if I don't find anything else the MRX 110 or what ever the MRP 1000 replacement is.


----------



## gijoe (Mar 25, 2008)

*Re: best amount of power to... well power subs, help me deal with myy friend*

Well first of all, you can not toast a sub with too little power. If you are clipping the signal it will only damage the sub if you are clipping the signal bad enough to over power the sub. The clipping itself will not hurt a thing, the sub doesn't care what shape the wave is as long as it doesn't contain more power than the sub can handle. You can clip the **** out of a low powered signal and send it to a sub without damaging the sub at all. 

Also, you aren't going to instantaneously kill a sub by giving it too much power. People often confuse how much power they have on tap with how much their speakers are actually getting. It's a good idea to have more available than you need and adjust the gains appropriately to keep the speakers within a reasonable limit.


----------



## amalmer71 (Feb 29, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*

Speaker power handling < Pro-Audio References


----------



## underdog (Jul 5, 2011)

*Re: best amount of power to... well power subs, help me deal with myy friend*

Also insure you have a correct enclosure.


----------



## ScaryfatkidGT (Mar 31, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*



gijoe said:


> Well first of all, you can not toast a sub with too little power. If you are clipping the signal it will only damage the sub if you are clipping the signal bad enough to over power the sub. The clipping itself will not hurt a thing, the sub doesn't care what shape the wave is as long as it doesn't contain more power than the sub can handle. You can clip the **** out of a low powered signal and send it to a sub without damaging the sub at all.
> 
> Also, you aren't going to instantaneously kill a sub by giving it too much power. People often confuse how much power they have on tap with how much their speakers are actually getting. It's a good idea to have more available than you need and adjust the gains appropriately to keep the speakers within a reasonable limit.


well I know woofers have a peak rating that they can put out for a shot period like a bass drum hit so you can have a little more power, but amps have a peak rating too?

and like you said just cuz an amp is 1200w rms doesn't mean that is going to the subs but here are the 3 examples im confused about.

My 13.5" W3v3's in a JL custom sealed box, I currently have a MRP M1000 and it over heats at 2ohm after an hour or so of playing and then doesn't hit as hard until I let it cool and its touch and I had to send it to alpine once already so I want a better amp. So should I stick with something like the PDX M12 or JL HD1200/1 or could I run something like the T1500bdCP? but then even the T1000bdCP says it puts out 1299w at 2ohm "dynamic power", what's that mean? and what amp should a run to get a little more power and better SQ and not wreck my subs?

Then I might splurge and get 2 13.5" W7's that I would run a JL HD1200/1 to each (one being the one I buy for my current subs) but my friend has a 12" W7 he doesn't want so if I find another one for a good price il run 12's but what do I power those with? I'm probably stick with a sealed box but there are no 2000w rms amps? should I run a HD750/1 to each and not have full power? or run a 1200/1 to each and risk hurting them? or run like a T2500bd to both and home its a good match at 3ohm?

and finally my friends 12" T2's hopfully in a custom ported box, what do you power those with if not the T2500bd? a T1000bdCP to each? or what...



underdog said:


> Also insure you have a correct enclosure.


I'm pretty happy with sealed boxes right now so aslong as there enough volume I should be good


----------



## ScaryfatkidGT (Mar 31, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*



amalmer71 said:


> Speaker power handling < Pro-Audio References


5. Selecting amplifier power

In general, the amplifier power needs to be larger than the speaker's rated power. This is because an amplifier only delivers its rated output power with sinewave signal, and delivers much less with a real signal with dynamics. As general guideline, it is recommended to use an amplifier delivering 50% more power than the speaker's average ("RMS") power. For example, for a speaker with 450W average power, an amplifier with an output of 700W may be used. If a small amplifier is used, sufficient level will not be reached, nor the perception that it is attained, so the signal will tend to be clipped to compensate, thus endangering the integrity of the speaker.

So is that agreed to be true? All car audio amps are rated at sinewave power? What about RF's "dynamic power" rating?


----------



## Zippy (Jul 21, 2013)

*Re: best amount of power to... well power subs, help me deal with myy friend*

Let's clear up some things. 

1st off, under powering a sub will not damage it. My T2's have been running under powered for over 6 years and still are in perfect working order. What kills subs in an under powered situation is when someone turns up the gains on the amp to the point of clipping. It's clipping that will kill the sub. And clipping doesn't care if it's under or over powered.

2nd, if you are going for SPL then the extra 10% rule is valid. If your end goal is SQ, then under powered is what you want. My T2s are silent as can be on a track without bass Jimmy Buffet-Margaritaville and come to life when I play something like Lorde-Royals. 

3rd, what's on the RF birth sheet is what they put out as far as power goes. If you want the 10% over for SPL, then match the power output rating on the RF amp to the subs and let the birth sheet cover the extra.

Hope that was helpful.


----------



## minbari (Mar 3, 2011)

*Re: best amount of power to... well power subs, help me deal with myy friend*



Zippy said:


> Let's clear up some things.
> 
> 1st off, under powering a sub will not damage it. My T2's have been running under powered for over 6 years and still are in perfect working order. What kills subs in an under powered situation is when someone turns up the gains on the amp to the point of clipping. It's clipping that will kill the sub. And clipping doesn't care if it's under or over powered.


that is true to a point. if I have subs that are 1000RMS and power them with a 300 watts amplfiier. I can clip it to 100% squarewave all day long. that is still only 600 watts. wont hurt them a bit. if I have a 700 watts amplifier, then 100% clipping would be 1400 watts, good chance you will damage them. So you cant just say that clipping will hurt a speaker.


> 2nd, if you are going for SPL then the extra 10% rule is valid. If your end goal is SQ, then under powered is what you want. My T2s are silent as can be on a track without bass Jimmy Buffet-Margaritaville and come to life when I play something like Lorde-Royals.
> 
> 3rd, what's on the RF birth sheet is what they put out as far as power goes. If you want the 10% over for SPL, then match the power output rating on the RF amp to the subs and let the birth sheet cover the extra.
> 
> Hope that was helpful.


----------



## Zippy (Jul 21, 2013)

*Re: best amount of power to... well power subs, help me deal with myy friend*



minbari said:


> that is true to a point. if I have subs that are 1000RMS and power them with a 300 watts amplfiier. I can clip it to 100% squarewave all day long. that is still only 600 watts. wont hurt them a bit. if I have a 700 watts amplifier, then 100% clipping would be 1400 watts, good chance you will damage them. So you cant just say that clipping will hurt a speaker.


I've seen voice coils detach due to clipping even grossly under powered. The prolonged excursion of the sub has an effect even at 300rms on a 1000watt sub. It just takes longer for the effects to show up. Also on a side note, have you heard what a clipping sub sounds like? Just plain bad.


----------



## minbari (Mar 3, 2011)

*Re: best amount of power to... well power subs, help me deal with myy friend*

I dont disagree that it sounds REALLY bad. but I also have heard people play subs well beyond mechanical limits and thought it sounded good, lol.

I dont agree with you on the power issues. if a sub can handle 1000 watts of heat, then it doesnt matter where that heat comes from. speakers dont care if it is a sine,square or triangle wave. it just moves back and forth. Now if you are suggesting that the extra power from hard clipping will cause mechanical failure, that is possible. if you have a 300 watt amplifier on a 1000 watt sub and it only takes 400 watts to reach past xmech, then 100% clipping (600 watts) would be past its mechanical limit. But any amplifier with more than 400 watts of power would do that same thing, so clipping still plays no role in it, just the amount of power.


----------



## Zippy (Jul 21, 2013)

*Re: best amount of power to... well power subs, help me deal with myy friend*

It's not a power issue it's a physics issue. When excursion happens there is a force in one direction. With the clipping when the cone tries to return the other way it gets bounced back where it came from by the still exerted clipping block wave. This causes stress on the voice coil connection to the cone. Hence my point of voice coil detaching. Power handling is not an issue at all. It'll handle the power just fine.


----------



## minbari (Mar 3, 2011)

*Re: best amount of power to... well power subs, help me deal with myy friend*

no it doesnt. play a 1 hz square into a sub and watch watch it does. it will extend forward, stop. then pull back, stop. then go back forward. only difference with a sinewave is that it doesnt stop at the squared off ends of the signal. A squarewave is technically still sine waves. Its just alot of harmonics that add up to make it square.

You cant send a signal will will make a sub want to go both ways at the same time. physically and electrically impossible. there is no magic in a speaker. it is just a linear actuator with a cone attached. it can only go one way at a time. There is no extra stress because of the waveform type. 

Do you really believe that jerking a cone back and forth 20 or 40 times a second is less or more stressfull based on the waveform? its still going back and forth, that is all it does.


----------



## Zippy (Jul 21, 2013)

*Re: best amount of power to... well power subs, help me deal with myy friend*

I may not be explaining myself well. Let me try this approach. Pick up a book and hold two opposite corners, one in each hand. Now move that book like a speakers cone back and forth slowly. Not a lot of force on your hands. Now do the same thing with abrupt stops to form the block wave of a clipping signal. There is noticeably more force on your hands at the stop points. That increase in force is what causes the damage over time. Not a day or two, but a month or more.


----------



## amalmer71 (Feb 29, 2012)

Zippy,

Conduct an experiment.

If you're so convinced the square wave is what causes the voice coil to overheat and become damaged, use this tone generator to create a file with a square wave at 100Hz and try it.

Square Waveform | Online Audio Wave File Generator


----------



## Zippy (Jul 21, 2013)

amalmer71 said:


> Zippy,
> 
> Conduct an experiment.
> 
> ...


Would you please show me where I said it would overheat? I never said that. It's a physical stress issue.

As a matter of fact, let me quote myself.



Zippy said:


> It's not a power issue it's a physics issue. When excursion happens there is a force in one direction. With the clipping when the cone tries to return the other way it gets bounced back where it came from by the still exerted clipping block wave. This causes stress on the voice coil connection to the cone. Hence my point of voice coil detaching. Power handling is not an issue at all. It'll handle the power just fine.


NO OVERHEATING! All physical stress. 

:dead_horse:


----------



## BuickGN (May 29, 2009)

So are you trying to say there's more gforce on the cone with a square wave because of a more abrupt stop at the end of each stroke?


----------



## amalmer71 (Feb 29, 2012)

Zippy said:


> Would you please show me where I said it would overheat? I never said that. It's a physical stress issue.
> 
> As a matter of fact, let me quote myself.
> 
> ...


Oh. I was trying to decipher and make sense of what you said, but I guess I failed. I'm so used to dealing with people that incorrectly think the coil overheats because of amplifier clipping, I didn't realize there are people who think it causes a mechanical failure, too. 

:freak:


----------



## ScaryfatkidGT (Mar 31, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*



minbari said:


> no it doesnt. play a 1 hz square into a sub and watch watch it does. it will extend forward, stop. then pull back, stop. then go back forward. only difference with a sinewave is that it doesnt stop at the squared off ends of the signal. A squarewave is technically still sine waves. Its just alot of harmonics that add up to make it square.
> 
> You cant send a signal will will make a sub want to go both ways at the same time. physically and electrically impossible. there is no magic in a speaker. it is just a linear actuator with a cone attached. it can only go one way at a time. There is no extra stress because of the waveform type.
> 
> Do you really believe that jerking a cone back and forth 20 or 40 times a second is less or more stressfull based on the waveform? its still going back and forth, that is all it does.


Only thing I can think of is the voice coil having to hold the cone all the way up or all the way down, idk if that is bad or not or if it generates more heat, the G's would be the same or less but it might take a lot more energy to hold it there vs. letting it spring back especially in a sealed box.

AAAAAAaaaannnnny way does the synwave power and needing 150% power apply to car subs? Cuz from what I have been told/read I probably shouldn't go to much over the RMS rating of my subs? So ill probably get the JL HD1200/1 for my dual W3v3's....

Why is this stuff so convoluted and every one has there own opinion, hasn't everyone tried and figured this stuff out 20 years ago?

And people play squarewaves to test headphones all the time all thought not at very high volumes and not with 1000 watts to heavy sub drivers.


----------



## ATOMICTECH62 (Jan 24, 2009)

I agree with you.
If you connect a sub(or any speaker)up to an amp with a scope monitoring the wave,you can watch the cone follow the gradual up and down motion of the wave.Push the square wave button and it wants to slam forward,stay there for the duration of the dc its getting,then slam rearward,stay there for the duration of the dc its getting,then repeat over and over. 
The gradual up & down motion of the sub with a sine wave creates an even flow of air around the voice coil cooling it.The square wave doesnt allow the cone to move in a linear motion.Its always fully forward or rearward 99%of its duty cycle so its nonlinear motion doesnt provide adequate cooling.
Since the RMS of a sine wave is .707 of the DC (which is a square wave alternating its phase 180 degrees)rail voltage you can multiply the RMS output voltage of the amp by 1.414 when its hard clipped.
An amp that does 45 volts RMS into 4 ohms=506watts.
45x1.414=63.63 volts.
63.63 volts into a 4 ohm load=1,012 watts.
So now the amp has double the power and the sub has less cooling capabilities.
To me this shows that an amp driven to clipping can damage a sub even if the amp has a lower power rating then the sub.
Plus I have pulled too many smoking subs out of boxes that are so hot they can melt the skin off my hands(I learned the hard way)with amps that had lower ratings then the subs.


----------



## BuickGN (May 29, 2009)

*Re: best amount of power to... well power subs, help me deal with myy friend*



ScaryfatkidGT said:


> Only thing I can think of is the voice coil having to hold the cone all the way up or all the way down, idk if that is bad or not or if it generates more heat, the G's would be the same or less but it might take a lot more energy to hold it there vs. letting it spring back especially in a sealed box.
> 
> AAAAAAaaaannnnny way does the synwave power and needing 150% power apply to car subs? Cuz from what I have been told/read I probably shouldn't go to much over the RMS rating of my subs? So ill probably get the JL HD1200/1 for my dual W3v3's....
> 
> ...


If it's playing a given frequency but it's getting to the end of stroke quicker and holding there, there has to be more peak gforce but maybe the average gforce is similar. I have no idea if it's significant or not.


----------



## ATOMICTECH62 (Jan 24, 2009)

Power ratings on subs is very arbitrary.The Kicker SoloX 18 has a 10,000 watt rating.But looking closer at Kickers website shows 3 different power ratings depending on the box.10,000,5000 and 4500.We sold 2 different people 1 Solo18 and 1 Kicker ZX2500 amp.The boxes were built to kicker specs and subsonic filters were used.
They both blew within a month.We reconed them and they blew again.They both now sit for sale in the display case with new cones and have been for about a year.
So what went wrong?How much power should they be given?
If you blow a sub with a smaller then recommended amp,could it be because its overrated also.


----------



## jdsoldger (Feb 14, 2012)

Hoo boy. This is quite a subject that involves a lot more than just amplifier rating, sub power rating and clipping or not. It takes into account mechanical limits, driver construction, box design, how it will be used and the most important part, the person running it all. I will leave this post here for now and work on putting together as comprehensive of an answer as I can since this seems to get asked a lot of places. I also refuse to try to put it together while typeing on a phone. I have class tonight but hopefully tomorrow evening I will have time to put something together.


----------



## Hillbilly SQ (Jan 26, 2007)

You can never have too much power if you know how to use it


----------



## ScaryfatkidGT (Mar 31, 2012)

jdsoldger said:


> Hoo boy. This is quite a subject that involves a lot more than just amplifier rating, sub power rating and clipping or not. It takes into account mechanical limits, driver construction, box design, how it will be used and the most important part, the person running it all. I will leave this post here for now and work on putting together as comprehensive of an answer as I can since this seems to get asked a lot of places. I also refuse to try to put it together while typeing on a phone. I have class tonight but hopefully tomorrow evening I will have time to put something together.


Yeah I mean a lot of things sparked this post being told many things from many different people but my friend seemed to be set on a X watt RMS rated speaker needs an X watt RMS rated amp or it will be underpowered or blow and I was like "Dude you can throw a 1500w amp on a pair of 600w RMS subs and not blow them just don't listen at full volume and set the gains right also if your 6x9's are 100w and your 6.5's are 65w a 100w x4 amp will work fine" and he seemed to think thats wrong.

But then we both have recently gotten into W7's (2 12's and a 13'5", the 2 12's being mine when I buy them from him and he is going to rock a 13.5" in a ported box) and JL a good company that honestly rates there stuff accurately or conservatively (not like the new Type-R's and over-rated high-end kickers) only recommends 750-800w on there 1000w rms W7 and 1000-1200ish on there 1500w 13'5" W7, I always thought hi end stuff was made to take more of a beating but I guess not?

I was going to throw a T1500bdCP on my 2 13'5" W3's to upgrade from my "touchy" MRP-M1000 but then you look and the 1500 does 1550w but under dynamic power the T1000 does 1299w @2ohm so idk what to go by, what voltage are these ratings at? Seems stupid to go from one 1000w amp to another but I don't want to wreck my subs either.... home audio is so much easier.

Would a 2500bdCP work with 2 T2's? and looking for W7 amps is even harder because only JL rates there stuff at 3ohm.


----------



## Hoptologist (Sep 14, 2012)

*Re: best amount of power to... well power subs, help me deal with myy friend*



Zippy said:


> If your end goal is SQ, then under powered is what you want.


I disagree with this. I was giving my Black12 (Arc rates it at 500RMS) 750RMS from my Audison LRx 5.1k and it was pure sq all day.


----------



## Hoptologist (Sep 14, 2012)

ScaryfatkidGT said:


> because only JL rates there stuff at 3ohm.


JBL does too.


----------



## squeak9798 (Apr 20, 2005)

ATOMICTECH62 said:


> I agree with you.
> If you connect a sub(or any speaker)up to an amp with a scope monitoring the wave,you can watch the cone follow the gradual up and down motion of the wave.Push the square wave button and it wants to slam forward,stay there for the duration of the dc its getting,then slam rearward,stay there for the duration of the dc its getting,then repeat over and over.
> The gradual up & down motion of the sub with a sine wave creates an even flow of air around the voice coil cooling it.The square wave doesnt allow the cone to move in a linear motion.Its always fully forward or rearward 99%of its duty cycle so its nonlinear motion doesnt provide adequate cooling.
> Since the RMS of a sine wave is .707 of the DC (which is a square wave alternating its phase 180 degrees)rail voltage you can multiply the RMS output voltage of the amp by 1.414 when its hard clipped.
> ...


95honda on another forum conducted an experiment many years ago where he actually tested this. He could not demonstrate within the scope of the experiment that the shape of the waveform caused early failure to the driver. When using normalized power and comparing driver failure times, a clipped vs sine wave signal caused essentially the same failure times. Which means it's the amount of power, not the shape of the signal, that causes driver failure.


----------

