>>That's my question, Why wouldn't it blow the sub?
>>You had a 200 rms amp blow a 300 rms sub, but you dont think
>>that 250 rms can't blow a 500 rms sub? I'm lost.
>
>If the 250wrms is not near the max capabilities of the amp,
>why can't you understand? Now if it was a 250wrms rated amp
>instead of a 400wrms amp and the sub was a little less stout
>that the 500wrms one you're suggesting, it might just be
>possible.

but as long as its not overdriven, it wont hurt right?

 

>
>>
>>I think you luck is grand indeed, 0/8 right?
>Like I said.. What luck?

Didn't you say you consistantly underpower your subs and never have them blow? I would consider that either good luck or good setup or both.

 

>>
>>>
>>>I think you luck is grand indeed, 0/8 right?
>>Like I said.. What luck?
>
>Didn't you say you consistantly underpower your subs and
>never have them blow? I would consider that either good
>luck or good setup or both.
Either that or it's a myth that underpowering is what blows speakers..

 

>Also, this one if you wouldn't mind.
>
>Assuming gains are set to match preout voltage, which one do
>you really think would blow a 250 rms sub first?
>1.) 150 RMS amp
>2.) 1200 RMS amp
>
Beats me, it depends on how many wrms are going into the 250wrms sub. Are you saying 1200wrms into a 250wrms sub, or 250wrms into a 250wrms sub from a 1200wrms amp?

 

>>Also, this one if you wouldn't mind.
>>
>>Assuming gains are set to match preout voltage, which one do
>>you really think would blow a 250 rms sub first?
>>1.) 150 RMS amp
>>2.) 1200 RMS amp
>>
>Beats me, it depends on how many wrms are going into the
>250wrms sub. Are you saying 1200wrms into a 250wrms sub, or
>250wrms into a 250wrms sub from a 1200wrms amp?

I'll let you decide. As stated above: Assuming gains are set to match preout voltage.

(read: overpowering vs underpowering)

 

ok, if I'm buying an amp to power a 300wrms sub, I would want it to be atleast capable of delivering 350wrms or maybe 400wrms. I would feel comfortable that my amp could deliver a full 300wrms without any problems, and the extra money is worth the peace of mind.

I am not saying you could not get away with any other combination, but for my money and my systems, this is what I do. This is also what I recommend and I don't see what the big deal is about the recommendation.

 

>>>Also, this one if you wouldn't mind.
>>>
>>>Assuming gains are set to match preout voltage, which one do
>>>you really think would blow a 250 rms sub first?
>>>1.) 150 RMS amp
>>>2.) 1200 RMS amp
>>>
>>Beats me, it depends on how many wrms are going into the
>>250wrms sub. Are you saying 1200wrms into a 250wrms sub, or
>>250wrms into a 250wrms sub from a 1200wrms amp?
>
>I'll let you decide. As stated above: Assuming gains are
>set to match preout voltage.
>
>(read: overpowering vs underpowering)

Very well, I pick a 1200wrms amp delivering a full 1200wrms to a 250wrms sub would be the fastest and most sure way to blow it. It supports both of our arguments. The 1200wrms amp is putting out near its max and the poor 250wrms sub is receiving way too much power.

 

>Very well, I pick a 1200wrms amp delivering a full 1200wrms
>to a 250wrms sub would be the fastest and most sure way to
>blow it. It supports both of our arguments. The 1200wrms
>amp is putting out near its max and the poor 250wrms sub is
>receiving way too much power.

ok then.. last question then im gone..

making things equal again..
sub = 700 RMS
amp a = 200 RMS
amp b = 1200 RMS
Both at full unclipped/distortionless power

Both are either under or over powering by 600 watts..

Which would blow the sub first, and why?

 

>ok then.. last question then im gone..
>
>making things equal again..
>sub = 700 RMS
>amp a = 200 RMS
>amp b = 1200 RMS
>Both at full unclipped/distortionless power
>
>Both are either under or over powering by 600 watts..
>
>Which would blow the sub first, and why?

You mean 500wrms (1200-700=500)

I don't think amp a has enough power to damage a 700wrms sub.

In nearly all cases I would say damage would result from amp b, especially seeing the amp is near max capabilities.

I think these are extreme cases that would never be called into question anyway. Furthermore, I would not recommend either. The heart of the issue is a 300wrms sub and a 200wrms amp.

 

>Objective: Power is not proportional nor in phase with
>either the voltage or the current in an R-L circuit.
>
>Definitions: PI=3.1415926..., F=frequency, t=time,
>L=inductance in henrys. The rest is explained as
>progressed.
>
>PROOF:
>The instantaneous potential difference is the max potential
>difference multiplied by the cosine of the angular velocity
>multiplied by time. Or say v=V*cos(2*PI*F*t).
>
>The same can be said about current, i=I*cos(2*PI*F*t)
>
>Now, we can apply ohm's law to this, V=I*R
>
>Therefore, v=i*R and then by substitution we have
>v=I*R*cos(2*PI*F*t). This is the instantaneous potential
>difference (voltage) across a resistor.
>
>Now, how about an inductor? We start with ohm's law again,
>V=I*R
>
>The induced EMF is given by E=L*(slope of i plotted against
>t or di/dt). Now, by substitution we have,
>E=L*d(I*cos(2*PI*F*t))/dt which works out to be
>-I*(2*PI*F)*L*sin(2*PI*F*t). Now, since
>cos(anyangle+90)=-sin(sameangle) we can substitute and
>write: E=I*(2*PI*F)*L*cos(2*PI*F+90). This result shows
>that voltage can be viewed as a cosine function with a head
>start of 90 degrees. Thus, for a pure inductor, we can say
>the voltage leads the current by 90 degrees, or 1/4 cycle.
>
>Now, on to power. Instantaneous power is given by p=v*i.
>In the case of a pure resistor, v*i is always positive
>because v and i are always in phase with each other and are
>always both positive or both negative. But, in the case of
>an inductor, the voltage leads the current by 90 degrees and
>they are not always both negative or both positive.
>Therefore, when we multiply v*i, the product is negative for
>half a cycle and positive for the other half and is neither
>in phase with i or v. The average power is zero and when p
>is positive, the field in the inductor is being produced and
>when p is negative, the field is collapsing. The net energy
>transfer over one cycle is 0.
>
>Anyway, the instantaneous
>power=(V*cos(2*PI*F*t+90))*(I*cos(2*PI*F*t)) for a pure
>inductor.
>
>When we add resistance and/or capacitance to the mix, we
>can't use 90 degrees any longer. We must use a phase angle
>with respect to the current i and the instantaneous power p.
> Call this phase angle Ph, then cos(Ph) is called the power
>factor of the circuit. To compute the power factor for an
>L-R circuit, we may use this equation, tan(Ph)=(2*PI*F*L)/R,
>solve for Ph and then take the cosine.
>
>A low power factor is undesirable in power circuits because,
>for a given potential difference, a large current is needed
>to supply a given amount of power.
>
>If you have to read this more than 3 or 4 times and still do
>not understand, you may need an elementary book on circuits
>and/or physics. However, your complete understanding is
>required before we can progress any further in this study.
>Please let me know when you understand.


This is basic first year stuff.. and really very irrelevant!

1) For one thing, the discussion was on cone MOTION lagging behind the current through the coil/resuting coil magnetic force, NOT on the current lagging behind the voltage, power lagging behind voltage, etc.

2) I really really hope you aren't trying to argue that BACK EMF could contribute constructively with the motion of the voice coil and subwoofer!
If you are, you should patent the worlds first perpetual motion machine!
Just set a voice coil in motion and watch it pick up speed, right?
Hahahaha... :+
(hate to break it to you, but BACK EMF works AGAINST you!)

3) As for the power argument, and the phase angle being disjoint...
Also irrelevant, as regardless, you aren't going to prove that you have MORE power at any point in the cycle...
You can't end up with more power out of it than you put into it, right?
"energy can neither be created nor destroyed"
they teach that in 4th grade nowadays, don't they?

I do see that these textbooks you are so proud of simply are first-year and/or high school level texts, eh?

 

> Therefore, I would say the 450wrms amp would
>be stressed far less by delivering 200wrms and the 200wrms
>amp would be very stressed trying to keep supplying the
>200wrms.
>


Please define what you mean by "stressed"
If the amp is not clipping, as you say (and verified with an Oscilliscope, right?), how would the amp be "stressed"
Quantify that...
Describe what elements of the amp would be "stressed", and how that would show up in the output from the amp (that's the most important part).


>Furthermore, power is not necessarily power. As you will
>see when you come to understand those equations I have
>posted, the power phase and power factor can change
>according to the impedances presented by the driver. If an
>amp cannot continue to supply the required current, for
>whatever reason, it should be an easy observation to see why
>the power factor and phase will change as well, possibly
>requiring more current that the amp can already supply.

The phase angles are either perfectly "in phase", or else they are not.
No doubting you (or really, the commonly known formulas) on that they will not be perfectly in phase..

But when that happens, the result can be nothing other than there being LESS power than if all angles were perfectly in phase (which, I actually believe, is... impossible!)

And the resulting power output would still be clean, still be a perfect sine wave out, if the input was a perfect sine wave out.. it just wouldn't have as much power.
Phase angle of current vs. voltage vs. power is COMPLETELY not an issue. It cannot be constructive, only destructive.. and by that the signal still remains perfectly well formed, couldn't be any more harmless on the subwoofer.

 

Since no reply in a few hours...

This very chart from JL Audio themselves on the power recommendations for your subwoofer:
http://www.jlaudio.com/subwoofers/RP_Chart.html
is enough to prove your theory for failure wrong (barring a defective driver, if all other factors were correct as you say they were, and we say were not).

Summing up the chart:
Green = Maximizing woofer longetivity, minimizing SPL potential
Yellow = good woofer longetivity, good SPL.. recommended compromise.
Red = minimizing woofer longetivity, maximizes SPL potential.

Look at your woofer, the 12W6:

Note two things:
1) The "green zone" extends down to 125 watts. Your 200 watts was not running below JL's recommendations (remember, 300 watts is a maximum RMS upper limit).
2) Per JL's own descriptions [on the different color zones], the trend is that as the power decreases, woofer longetivity is increased (while SPL also decreases).

 

New hear, but not to car audio...I'll add my $.02 worth, take it as you will.

We find two major contributors to blowing subs.

1) over powering a sub

2) pushing a sub past it's mechanical limits

We do not find any problems with underpowering a sub...we do find problems in these cases with customers cranking the gain up like a volume **** in these cases.

Install on any system will be the main determing factor, but customer abuse, also has to be taken into consideration, when subs blow.

As far as putting 200 watts to a 300w woofer..as long as the gains are matched, go for it!

Tracy Focht aka Polecat
Kicker Car Audio
www.kicker.com

 

Okay, so basically just about everybody but RanDawg has accepted that underpowering a sub will not blow it. Good, I guess if only one person believes 200rms Amps blow 300rms Subs then that is a good thing.

I've run a good dozen underpowered sub systems and currently only use 1000rms to power my 1600rms Brahma sub. According to RanDawg my sub is danger of blowing. Yet everyday it fires up and thumps away and I'd bet that sub keeps thumping away until I decide to retire it.

For pics of my endangered sub. http://members.sounddomain.com/jimi7

 

>New hear, but not to car audio...I'll add my $.02 worth,
>take it as you will.
>
>We find two major contributors to blowing subs.
>
>1) over powering a sub
>
>2) pushing a sub past it's mechanical limits
>
>We do not find any problems with underpowering a sub...we do
>find problems in these cases with customers cranking the
>gain up like a volume **** in these cases.
>
>Install on any system will be the main determing factor, but
>customer abuse, also has to be taken into consideration,
>when subs blow.
>
>As far as putting 200 watts to a 300w woofer..as long as the
>gains are matched, go for it!
>
>Tracy Focht aka Polecat
>Kicker Car Audio
>www.kicker.com

Hey Tracy, this is quinton from CAF> Thanks for showing up. Maybe this will put his depute that "kicker says underpowering is harmful to subs" to rest.