quote:Originally posted by Twellmann: a sidenote..
a woofer is designed to dispose of the excess heat, and it does that by movement of the cone mainly.
a lightbulb has no means of removing heat other than just sitting there..
a sub and a lightbulb are not the same...
Plus a lightbulb is more similar to a resistor in the fact that it is not a reactive load...A 100 watt lightbulb will always be the same ohm load at 100 watts. Also the power to a lightbulb is not varied as it is to a subwoofer. Also lightbulbs don't have impedence rise. Or a mechanical xmax limit. Or voicecoils that have thermal and mechanical limits. Not the same at all. Also, all amps are not designed to be ran at 4 ohms. Most good amps are designed to be ran at 1 ohm, and some can go as low as .125 or less for burps. Amp manufacturers know that most people are going to run their amps at 1 ohm loads, that is why they deisng around a 1 ohm load. An orion 2500d isn't called a 2500d because it puts 2500 watts into 4 ohms, it's called a 2500d because it puts 2500 watts into 1 ohm, because as i said already, most mid to high quality amps are designed to be ran at 1 ohm, that is where they are most efficient. I would however say that amps do like a higher resistance such as 4 ohms, but then again doesn't a ferarri like 25mph? (if you compared a sub to a lightbulb then i can compare amps to italian sportscars btw!!1 ). But a ferarri isn't designed to go 25mph, it's desinged to go 200mph, just like the 2500d is designed to put out 2500 watts...into 1 ohm. Ooh, and I could go on all day about amps to substitute for the 2500d, just don't have time to name a good 70% of the mid to high end amps. And yes, lower quality and/or more mainstream amps (ala rockford fosgate) are meant for higher resistances. Sorry if I'm a noob ripping on a pro here, but it had to be done. Flame away!
Why do you insist that ALL car audio amplifiers are designed to run at 4 ohms. Wake up! This hasn't been true for years. THere are several amps that deliver a consistant power at variable load impedances. There are quite a few more than are extremely stable into a 1/2 ohm load. An amp stable at 1/2 ohm is not, in most cases, designed to be run at 4 ohms. Yes lots of nasty things can happen when you reduce load impedance but if you remain safely within operating parameters you are in good shape.
What technical training do you have that backs up your statement. I know that practical experience can never be replaced by a book but from the qualifications that you list on your web page I see neither training nor practical experience in the design of amplifiers. I admit that I have only designed a few and they were never marketed commercially. If I am missing something please educate me (the posts you provided above did not do so).
-------------------- 2004 Saturn Vue Red Line Edition Alpine DVA9860 Alpine H701 MB Quart QTD-25 B&C 6MD38 6.5" Mid B&C 8NDL51 8" Midbass IDMAX (3) MTX 81000D (3) MTX 8302 (2) MTX 6304 (2) Posts: 284 | From: Huntsville, AL (go to BFE and take a left) | Registered: Oct 2003
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After reading this post I can see that the point has already been beaten to near death and far from the subject, but I figured why not put it out of it's misery and beat it completely to death.
I've designed a few amps in my day and have the education to back it up. Ok, now to the point.
First, Wattage has nothing to do with heat. Watts is a unit of power. When you're talking about a 100 Watt lightbulb you're talking about one that uses 100 watts of power. And when you're talking about and Incandescent Lightbulb (the kinda that get hot) you have to kinda go back and look at the meaning of Incandescent which is "Emitting visible light as a result of being heated." The whole point of an incandescent filiment is to get hot! Flourescent lights and LED's do not get hot because they use a more efficient form of light production. Which brings me to my next point. The reason an amplifier gets hot is because of inefficiency. If your amp ran 100% efficient it would produce nothing but clean electrical power...no heat. By the nature of design class A amplifiers are less efficient than class D and concequently run hotter. The lost power is disipated in the form of heat. Heat can be interpreted as energy, energy over time is power.
Second, Amps are made to run at different loads and voltages. Operational Amplifiers (opamps) are made to run at infinite impedance. The distortion in an amplifier has more to do with the output transistor curves and the way they are biased than anything else, that and the linearity of the transistor itself. So wherever the transistor is most linear and at what current load it is biased is where it is most distortion free. Being that voice coils are a dynamic load...good luck running it at exactly this point. Input voltage has a lot to do with this as well. The one thing I can say is that running higher current (lower impedance) will produce more heat. But at the same time more current at the same voltage equals higer power. It is also for this reason easier/cheaper to build amplifiers with high power at low impedance. Ever notice how much more expensive home amplifiers are for the same power into 8ohms?
That's my two cents
And as for why one voice coil would heat up more than the other...I have no clue. Soundstream was bought out by another company a few years back. The last thing that the original soundstream company made I think was the Mule subs and the original 2000watt tarantula amps (the ones with the cutout spider on top, not the raised one). I believe the new owner is PowerAcoustik. Possibly just a different level of manufacturing quality than previous...I don't know, I haven't bought any of their new stuff. Either way that should never happen with correct wiring and a properly functioning amplifier.
Posts: 121 | From: Streator, IL | Registered: Jun 2000
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My thought is.. Will you ever find 2 subs that are identical, If they were made even a few hours apart it could be a whole nother batch, the company could have had a slight defect in one, even if i check the resistance of two of my identical subs, i can find .001 Ohm diff in almost everyone (in a vacuu, sealed space), if the subs aren't of the utmost quality there may be even greater difference, I think that both hooked up the same, same length of wire, it has to be a defect or a difference in the sub... ...atleast that's my thought
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quote:Originally posted by Eli47: ...and the amplifier reacts to HALF the load presented to it, because only half of each channel is used.
Ummm... WHAT???
Eli, please do not try to teach people about amplifiers until you know what your talking about.
Learn, then talk
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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Well, if you're saying that "when bridged an amplifier does NOT react to half the load presented to it", then if you're correct, everyone else is wrong and we should all learn from you? I've been in the industry 30 years, I don't talk about things I know nothing about, this is something I know from basic electronics 101 & 102, and I'd strongly recommend you take the course. *Edit* Ok, not my usual type of response.., look at it this way, we are ALL here to LEARN from one another, I'm not an electronic engineer and I don't want to make it seem as tho I am. If I am wrong about something I'd be MAN enough to say I was wrong, and LEARN from that experience. So as unfortunate as it seems many here are more quick to berate(dis) someone, than to give the proper information, and quicker to give an "opinion" than sound "advice". So, if I am wrong on that issue please let me/us know how. BTW as for my personal web site, it was something I created in '99 with the help of a friend using basic HTML on Notepad, I haven't updated it in years, and as I write in my Audio Info. page, "the advice or info is meant to enhance your knowledge not to impress some hard working salesperson..," no offence inteded to anyone
quote:Originally posted by netlohcs:
quote:Originally posted by Eli47: ...and the amplifier reacts to HALF the load presented to it, because only half of each channel is used.
Ummm... WHAT???
Eli, please do not try to teach people about amplifiers until you know what your talking about.
posted
Eli, I was referring to the part of your comment where you say "because only half of each channel is used".
This is far from correct.
The short of it is that your average car amplifier creates a set output voltage, and the current (thus wattage) is dependant upon the load of the speaker.
I would crunch the numbers for you and explain exactly how it occurs (if you still want me to later I will), but I just got home from work and I'm tired... plus I just had the eye doctor put those damn drops in my eyes so I can't see for crap lol.
Moral of the story -> When you bridge an amplifier the output voltage is DOUBLED. If the impedance were kept the same the current would also double, creating a 4x increase in power. Since the FETs in the amp are most likely not able to handle this doubling of current, that is why you must double your impedance. When this is done, the voltage is doubled, and the current stays the same, giving you a 2x increase in overall amplifier output.
Clear as mud, right?
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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quote:Originally posted by netlohcs: Eli, I was referring to the part of your comment where you say "because only half of each channel is used".
This is far from correct.
The short of it is that your average car amplifier creates a set output voltage, and the current (thus wattage) is dependant upon the load of the speaker.
I would crunch the numbers for you and explain exactly how it occurs (if you still want me to later I will), but I just got home from work and I'm tired... plus I just had the eye doctor put those damn drops in my eyes so I can't see for crap lol.
Moral of the story -> When you bridge an amplifier the output voltage is DOUBLED. If the impedance were kept the same the current would also double, creating a 4x increase in power. Since the FETs in the amp are most likely not able to handle this doubling of current, that is why you must double your impedance. When this is done, the voltage is doubled, and the current stays the same, giving you a 2x increase in overall amplifier output.
Clear as mud, right?
constant voltage / variable current only applies to a parallel connection...in series it is constant current / variable voltage for each load
quote:Originally posted by kan3: constant voltage / variable current only applies to a parallel connection...in series it is constant current / variable voltage for each load
True.. but I'm failing to see how this is relevant to how an amplifier works while bridged?
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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If you read the entire sentence you'll find I was referring to a BRIDGED mode scenario, where either a Positive of ONE channel and Negative of the Other (I know you know )is used. since only half of each channel is used the amplifier will react to half the load of either channels, and are you saying I am wrong here?
-------------------- E.C. Wuz here Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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Yes, I am saying you are wrong in that statement.
Saying "since only half of each channel is used" makes essentially no sense. If only "half" of each channel is used, how is the amplifier doubling its output?
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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aaahhh, ok, sorry about the mis-understanding, what I meant was, in Bridged mode the power doesn't double, it sums (adds up) the total of both into one channel. is this where you were headed? And when bridged I still maintain that ONLY HALF of each channel is used, IE; one positive one negative , and therefore the amplifier will react to half the load preesented.
-------------------- E.C. Wuz here Posts: 1057 | From: Vancouver, British Columbia, Canada 'eh | Registered: May 1999
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quote:Originally posted by Eli47: And when bridged I still maintain that ONLY HALF of each channel is used, IE; one positive one negative , and therefore the amplifier will react to half the load preesented.
That unfortunately still isn't correct. Just because you are only connecting wires to one lead (weather it be positive or negative) per channel does not mean that only half of that channel is used. If you truly were only using one lead per channel, you would get no output.
When an amplifier is bridged, one channel is inverted, and the two "unused" leads of each channel are then connected. Probably the simplest way to understand whats going on would be to observe what happens when you strap two individual mono block amplifiers.
One amplifiers signal is inverted, and the negative leads of each amp are then connected together. As I stated previously, the reason that you must double your impedance when strapping amplifiers is the current capabilities of the FETs inside the amplifier. You are essentially running two channels in series, and when you run voltage sources in series, the voltage is additive (in this case doubled, assuming the channels have equal potential output). If you were to keep the same load on the strapped pair as you did on the single channel, the current would also double (according to Ohm's law) and you would have 4 times the power. Since the FETs are not capable of infinite current, this is why impedance must be doubled.
If your still not clear on this, read through the post here in advanced topics titled "strapping more than two amplifiers". There is a break-down of the numbers and why this works the way it does.
-------------------- Nate Scholten Team Sounds And Motion SS 1-2 3rd place 2004 finals -THE BUILD- ~Our Drinking Team Has A Stereo Problem~ Posts: 4253 | From: Rhinelander,WI | Registered: Dec 1999
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A "bridged" amplifier doubles the voltage swing across the load. In the case of eli, you are correct in that the two voltages are "summed," however, they are out of phase so nate is even more accurate in his statements.
Half a channel is used in a logical sense, you only wire up one terminal from each channel
The whole current stage of each channel is used for a bridged amplifier, so, in essence the "whole channel" is used in an electrical sense.
Copper has a tendency to increase in resistance as its temperature goes up. I would guess that one subwoofer is slightly different in either Revc or Zop, causing it to reach a higher temperature equilibrium than the other. Alternatively, there could be some flex in the former/cone attachment, which would heat up as it is stretched back and forth, or, one subwoofer might have less ferrofluid, a misaligned set of plates obscuring the vent, or even a less conductive attachment between the leads and coil, causing a "pinch" and subsequent heat. Is the magnet and basket hotter as well? How fast does it heat up?
Also, wattage has a great deal to do with heat. Heat energy is radiated, and the rate at which any energy changes is "power" and measurable in watts.
I do indeed concur with eli's statement that the higher the resistance of the load, the better things typically go. I like this idea. Yay. Go resistance.
The lightbulb thing.. wow.
ShizzadowStar
-------------------- You can't build a reputation for what you're GOING to do.. But you can build one for TALKING about it!
It's all about knowledge, love and respect. Posts: 2579 | From: Somewhere In the Northeast | Registered: May 1999
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Since both of your subs are already blown, diagnosis is out the window. But one of the speakers in your system had a problem and not necessarily the one that got hot. If you are running dual voice coil woofers then you have 4 coils to watchout for. If one should fail then the system will still play but the majority of the power would be trying to roast the remaining coil in that speaker.
It all depends how you have the speakers wired. But my suspecion is that some where along te line you lost a voice coil in one of the subs.
It has nothing to do with the ohm rating of the amp. Also as to the statement that all amps are designed to run at a 4 ohm load well that is a myth.
If that were the case then all speakers would be wired with dual 8 ohm voice coils etc. And what you find is none of those out there.
Typically it is a inneficient practice to hook up speakers in series. So why would the same manufacturers that design thier amps to work at 4 ohm loads make Subwoofers with dual 2 ohm voice coils, dual 1 ohm voice coils, Quad .5 ohm voice coils 3 ohm voice coils, and the like.
But that is getting off topic, You probably blew a coil in one driver and were unaware of it, till total melt down.
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