Bc 3500

[ricksi30 923]

[shizzzon 461]

[95Honda 486]

Ugh... You need to make the correlation between system efficiency at resonance. Velocity drops as system efficiency increases. This is the whole point of exploiting resonance.

Look, you still just need to understand one thing... Power changes with the same voltage drive when impedance changes. Ohms law.

If you truly understood this, you would understand why adjusting power ouput via voltage reference with unknown impedance is not possible.

Knowing this is true, why on earth would you set a gain voltage threshold into an unknown load? It is ridiculous if you think about it...

I'm done with this. If you can't figure this out, I can't help...

[Quentin Jarrell 671]

I didn't say anything about system efficentcy. Only the correlation between impedance and velocity.

If you use your graph and manually figure each with in the usable bassband using a voltage of 50 volts. If each tone between 35 and 85 hertz were played for one second we could conclude an estimated root mean square of 185 watts. It's a bit crude but the graph isn't clear enough to figure every hertz

Going by the graph this sub should have an re of around 12? If you then use that figure you would wind up with 208 watts

I believe we could conclude that that would be a very good starting point t o set the amp.

[95Honda 486]

Or you just don't waste any time and leave the DMM for something else.

It just doesn't work as advertised and is a waste of time + gives false confidence. Additionally, everyone always touts the importantance of getting every last "unclipped" watt out of the amp on car audio forums. Set it to Re and you'll never see full power 99% of the time...

You take a kid and give him a DMM and he will mentally masturbate himself for hours using these tutorials. And it won't do a thing for him....

Your missing the point that system efficiency is the link between system impedance and velocity (moreso displacement)... This is the whole exploitation of resonance...

We'll never agree, that is OK.

[shizzzon 461]

I have a question...

Example scenario-

80v 20a @4ohm= 1600w

80v 40a @2ohm= 3200w

80v 80a @1ohm= 6400w

In real world, by the time i get to 1ohm, the voltage will sag a little but disregard that....

If i had an amp and only a DMM.. why does impedance even matter in terms of let's say to the point of viewing a clip on an oscope...

Are we on the same page so far?

@1ohm - 64ohms, etc.. for example.. there will be a limit that the amp starts to clip..

Now, let's disregard music, let's just be using test tones...

Are you(someone in here, hehe) saying that if i set an amp to 80v at one tone and it was clip free... another tone at 80v can possibly clip?

To keep the scenario more realistic, the electrical system remains the same throughout all tests and all source material is the same from one frequency to another.

It is my understanding that the voltage output itself is what gets over-driven to cause clipping.

Low DC voltage drop will cause an amp to clip sooner but i have never measured to see if a bad electrical system allows AC voltage output up to, IE- 80v, and still be clip free or if low DC voltage actually lowers AC output voltage which can then create clipping.. i do not know.. .

Debate..

[95Honda 486]

If the amp in your scenario is a 3200 watt amp you set if for a 2 ohm load (80V) you are in trouble when the system impedance dips below 2 ohms. That is the whole point here. And 2 ohm nominal subwoofers will drop below 2 ohms in the pass band at least at one resonance point...

The whole thing here is Ohm's law is not up for debate. The merit of setting a gain threshold with no real values is what is up for debate. I say it is meaningless when you have tolerances that well exceed 50%, others do not. That is the debate.

[95Honda 486]

OK, I will give you a scenario you can relate to.

Take a FI Q 12. It handles 1500 watts and in dual 2 ohm we wire it up for a 4 ohm load. We use JL audio's tutorial for the 1500 watt amp we just bought. We set the voltage to the proper level for 4 ohms and 1500 watts.

Now, that woofer will drop down to roughly 2.8-3 ohms at a minimum of 1 point in it's passband. You will be attempting to give it 2000 watts now, and the amp will almost do that. It will be heavily clipped, but still almost 2KW.

All this while you safely set the voltage of your 4 ohm sub according to the safe charts JL provided.

And on the flip side, you stay conservative at set the voltage threshold to your lowest measured impedance. You are trying to get all the volume you can for a competition and you wonder why your amp is nowhere near max output at your peak frequency. That is because your peak doesn't correspond to your system impedance minimum...

Do you see the error in these tutorials now?

[Quentin Jarrell 671]

Take a look again at you sernario. The Fi q is rated at 1500 watts root mean square. Meaning when they tested the sub it's inductance raised and lowered just as it would in an enclosure.

They don't say "it's rated for 1,500 watts, but make sure you don't give it that much power bc inductance will cause it to pull more power from the amp". No they say by a 1500 watt rms rated amp and stick it on it.

[Quentin Jarrell 671]

And for competition how does inductance cone in to play at your peak frequency. By what you have already said over and over inductance is raised and lowered by frequency. If you are only burping one frequency then wattage aint gonna change therefor you simply set the amp by JL's method. It'll be off a little bc amp output resistance hasn't been calculated but it'll be close.

[95Honda 486]

No they have rated the Q at 1500 watts, not 2000. 2000 is more than it was rated for.

You still don't even understand how reactance plays a role in things here...

Bro, I am not even going to respond to you anymore, you have no clue what is going on... This is like your "8 db more efficent T-Lines" garbage a while back... You spread missinformation and the wrong people listen and screw things up...

OP- Set the gain so it doesn't sound bad. Be carefull, you can cook those subs with that amp no matter what you do...

[Quentin Jarrell 671]

So the sensitivity of a t-line can't be 8-12 db more than a ported box, ok.

All I have posted was factual information by a reputable company that are one of the forefathers of modern car audio. If their technique is flawed I guess it's just dumb luck.

Using Your graph, and the formula for Root mean square we get a close wattage as when using the sub's Re alone. If the correlation can be seen then I'm sorry.

[Quentin Jarrell 671]

And OP. If you have a DMM can you please measure the output A/C voltage of the amp AFTER you set it by ear. I'd like to see how close JL is, just for giggles.

[///M5 2,833]

Huh? Are you seriously arguing this?

I = V/R

Now I changes so where do you set the V? Really fucking simple the ONLY way to do it is dynamically but there is no such thing so you can't.

Add to that it is a horribly stupid idea anyways. If all music was recorded with the same dynamics and peak then fine (although that would be REALLY boring). Since it isn't, then how do you pick your source level?

Citing that JL offers this is absurd as well. I can 100% guarantee that NONE of their engineers would use that method and YES I've worked with them. Completely asinine to think differently.

Not sure what is worse here. The complete lack of understanding or the role that the non-understanding person actually has in life. 95Honda's argumentation was rather easy to follow and super far from saying the same thing I can't begin how to comprehend that was even felt.

And to the OP. Seriously that method is absolutely terrible. As for gain setting that all comes down to your goals. If those aren't defined the method can't be, but the one prescribed to you by Audibel will just get you in trouble if you think you are "safe" using it. Absolutely nonsense.

[Quentin Jarrell 671]

I'm not arguing ohms law. I'm using it. We can all agree that music is dynamic, and that impedance changes. Yes I would be a fool to argue that. I'm not.

Going back to the graph posted by Honda if you manually calculate power by using the formula for RMS you get roughly 185 watts. Now if you take the re of that sub which would be around 12 by looking at the graph, using ohms law we get 208.33 (using 50 volts). So we can conclude the the RMS power would be less than the quadratic power. Correct? So if this amp was 225 watts RMS we could conclude that most of the time we would receive an unclipped signal?

Yes, again I agree impedance will drop below Re especially right above and right below tuning. But for the most part we would stay above this, correct?

Please don't get afended. I'm just using using ohm's law to calculate this. If this is incorrect that's fine. I just want something more than impedance fluctuates as a rebutle. Which I know, and has already been factored in with the formula for RMS and the impedance curve that had been posted.

I do agree to tune by ear, which is stated in the last paragraph of the JL tutorial. And this works fine when you have a 1,000 watt sub and a 1,000 watt amp bc in most any alignment you will come into mechanical noise before you hit the 1,000 watt RMS limit.

But say you have a Fi SP4 but you only have an amp that is 500 watts RMS. If you just tune it by ear you would be able to turn the gain wide open without hearing any type of mechanical noise. What would be the best approach to setting the gain in this senario?

Again please don't say it idiotic. Just respond with some mathematical data that disproves it.

[cbreen 0]

thanks for all the info but there is no way to set your amp but to just do it by ear. What about a SMD metter.

[ricksi30 923]

thanks for all the info but there is no way to set your amp but to just do it by ear. What about a SMD metter.

Pure marketing gimmick. It is completely useless.

[cbreen 0]

ok thanks. So my goal is spl so I need to set the gain to a 40 hz or lower?

[95Honda 486]

I would set it where you think you are going to burp, but again it is all relative.

Whatever you end up doing, just be carefull and use your senses when you start wailing on it. Smell for things getting hot, feel parts of the drivers for excessive heat, listen to signs of driver and/or amplifier stress... Do these things and you should be OK. Rely on only one thing (like setting your gain by voltage) and prepare yourself for damage with that power on those subs...

Everyone pretty much runs similar equipment in different enclosures/set-ups. What may be safe for someone in thier perspective application may not be the same for you. As we have beaten to death in this thread there are so many variations in impednace from design to design it is very hard to tell how how much is too much power...

Like I said, use your senses...

[///M5 2,833]

Just to clarify, he said senses which was plural. When you are squeaking as much as possible out of something making sure to smell, feel, look, and listen are important. No reason to taste though

Now if you take the re of that sub which would be around 12 by looking at the graph, using ohms law we get 208.33 (using 50 volts).

So now you are computing dynamic power with DCR? Perhaps you are more lost than I had originally thought.

What part of dynamic and frequency dependent is confusing to you?

I have another idea, you could arbitrarily choose a voltage and a frequency and randomly set the gain. Sounds good no? If so, then continue to do what you propose.

[Sencheezy 689]

[cbreen 0]

Good stuff. can't wait to see what the 2 12" dual 1 ssa zcons sound like on this amp going to try and hit a competition on August 5 if i get everything in. May not get to but im trying alternator is coming this week DC power. Had to change wire didn't want to use cca wire that the local store said it would be all right lol F*#k cca wire.

[Sencheezy 689]

lol No offense man, but please learn how to write a proper sentence! Cheese and rice I had to read that about 4 times and use my imagination to get what you were saying. Like two big ass run on sentences with no punctuation any where! lmao.

Edited July 24, 2012 by Sencheezy

[cbreen 0]

Sorry man didn't mean to make it so confusing. Oh its hard out here for a pimp.

[Adrian_D 520]

Yes, again I agree impedance will drop below Re especially right above and right below tuning. But for the most part we would stay above this, correct?

Just to make it clear, Re is Re, nominal resistance is a different thing.

If impedance is always = Re + Xe, where Xe = reactance, then you will never drop below Re. But if you have a 2 ohm nominal subwoofer, with an Re of 1.4 ohms you will drop below 2 ohms.