Impious

You learned how to calculate the volume of a cylinder in grade school. It was probably one of those things you swore you didn't need to remember because you would never use it in real life.

Amplifier Headroom - SSA Car Audio Forum

Class A is the least efficient amplifier design. They are theoretically limited to a maximum efficiency of 25% (remember, that's maximum). They also are never "off", which means they are pulling full amperage from the electrical system even at idle, with no signal input. Class A/B is more efficient than class A. At full power, they can be in the 60% efficient range. However their efficiency worsens as power output decreases. At 1/3 power they are only about 30-35% efficient. And guess where they amplifier spends most of it's time? Here's a hint; It's not towards the full power end of the spectrum. Class D are typically more efficient than Class A/B. Class A/B and class D efficiency can be similar at full power output, however class D don't suffer from the loss in efficiency at lower power levels that class A/B suffer from. As to the real "question" that you posed here; An amplifier should be designed to function properly within the temperature range it will be operating in. If you have an amplifier shut down on a shorter time scale due to over heating when used within it's intended operating range and given adequate ventilation, then it's heat dissipation properties was given poor consideration by the designer and that would qualify as a poorly designed amplifier.

There have been many. Every single one of them has failed to demonstrate there is any audible difference based upon the class of the amplifier. You can "feel" there is a difference all you want, but every valid test that would identify just such a difference has failed to do so.

There's no such thing as a "sound quality" amplifier. THD is a pretty unimportant spec to look at. Any amp worth owning (meaning anything but extreme low end junk) will be capable of operating at a level of distortion that is inaudible with music. Most amps on the market have their power rated at a THD level of equal to or less than 1%, which means there will not be an audible difference between them distortion wise. Many people mistakenly believe that THD is a "lower sounds better" spec, but the truth is that once distortion gets down to a certain level (2% or less) you won't be able to hear a difference with music. So you can ignore it. Signal to Noise Ratio (SNR) is the same way. Any amp worth owning will have a sufficient enough SNR to be audibly indistinguishable. SNR can only even be used as a point of comparison if you know the testing conditions of the measurement. If one amp had SNR rated at 1w of power output, and another amp rated at 100w of power output, then the "rated" SNR of the amplifiers are NOT directly comparable. But regardless, it's a relatively unimportant spec and can generally be ignored. Damping Factor is another spec that can be ignored. Many people incorrectly believe that DF is a "higher is better" spec. The truth however is that once an amplifier has sufficient damping as to not audibly affect the sound, going any higher will not yield any benefit. A damping factor of around 20 is sufficient enough to not cause an audible difference. Just about any amp on the market will have sufficient damping as to not audibly affect the sound. Damping factor thread is here: http://www.soundsolu..._1entry537161 Class A/B does not sound any better than Class D. Class A doesn't sound any better than Class A/B or D. You can not attribute any particular sound characteristics to the "class" of the amplifier, and no one has ever been able to conclusively demonstrate that the "class" of the amplifier affects the sound. What should you look for in an amplifier? Look for an amp that offers the most power output within your budget, has the features you need, the build quality you desire, aesthetics you prefer, fits your space requirements and has a warranty & customer service you can live with. It's that simple.

Getting sort of off topic.....but no, running a 2-way active front stage + subwoofer is a 3-way active system. A 3-way active front stage + subwoofer is a 4-way active system. Majority of people are already running their substage "active" by using the amplifier's or headunit's onboard amplifiers for the crossover. So when I was having this same argument and including the sub in my setup and claiming to have a three-way active system everyone on this forum was like no you dont have one, dont include the sub stage. Why was that? (not arguing just looking for some clarification). **I do understand how people are using there subwoofers with there headunits and amps to make it active and all that stuff. I cant remember when the thread was made but Ill search for it. Because subwoofers are generally a mono source. Your front stage uses a stereo source. 3-way + sub is accurate. It's all a part of the same system.

Why couldn't it? A properly designed enclosure is required, as in any other situation. The benefit is the large surface area of the drivers which reduces excursion requirements for a given output level, which keeps the driver's excursion further within it's linear operating range which will reduce distortion compared to similar drivers with less total surface area operating at higher excursion levels.

x2, Because I was going to go out and buy some clamp meters and so on, if that is the case then Impious you saved me some money then? If it's something you just want to play around with in your driveway, there's nothing wrong with it. However the information you record won't really have much utility.

Pretty much. But really, does it matter? +/- 30% variation in power isn't going to be audible.

There is. But it requires a bunch of equipment that most forum users don't have access to. A distortion analyzer, dummy load, and stable power supply are a step in the right direction.

Poppycock. Two 18's can be excellent for sound quality. I would use 18's myself if I could fit them....in fact I had a pair I was planning to use but decided against it due to the amount of space they would consume. As to the original topic, I agree; Don't go ported with that amount of space.

Erm, okay

I don't get what you guys are laughing at. I see nothing wrong with the install.

No idea. I'd have to read the thread.

Please bare in mind that clamp tests are not a very reliable or accurate test method, and not a method that should be used to compare one amplifiers performance to another for daily use applications or to determine the "actual" performance of any single amplifier. If I recall correctly RF claims their amplifiers will still make rated power down to around 12.5V, I believe this is part of the reason why the "birthsheets" show higher power output than rated (birthsheets are @ 14.4V). RF amplifiers are CEA-2006 compliant so they must state power is "rated" at 14.4V, but that doesn't mean they can't design the amplifier to still provide rated power at lower voltage levels. I didnt say anything about this test as being used as the holy grail, he asked what they do around 12 volts and I just posted a link for him to look at. I didnt want to say they do this so I posted what the owner of the company posted as a guide or reference to what their capabilities can be thats all; instead of me answering a question I have no facts on so I gave the OP facts. I understand. I posted my comments so others reading the thread, including the OP, didn't base decisions upon the information contained in the linked thread as the method used is inaccurate and unreliable and it has as of yet to be pointed out. Going forward, when linking to relatively unreliable or inaccurate data in response to a specific question asking for actual data it would be helpful to everyone if you included a short comment in your post indicating the inaccuracy of the provided information. In actuality, the linked thread doesn't answer the OP's question at all, and a clamp test doesn't represent "facts". It's data, unreliable data...that's all.

Getting sort of off topic.....but no, running a 2-way active front stage + subwoofer is a 3-way active system. A 3-way active front stage + subwoofer is a 4-way active system. Majority of people are already running their substage "active" by using the amplifier's or headunit's onboard crossover as the filter.

Please bare in mind that clamp tests are not a very reliable or accurate test method, and not a method that should be used to compare one amplifiers performance to another for daily use applications or to determine the "actual" performance of any single amplifier. If I recall correctly RF claims their amplifiers will still make rated power down to around 12.5V, I believe this is part of the reason why the "birthsheets" show higher power output than rated (birthsheets are @ 14.4V). RF amplifiers are CEA-2006 compliant so they must state power is "rated" at 14.4V, but that doesn't mean they can't design the amplifier to still provide rated power at lower voltage levels.

Keep in mind part of "sound quality" is accurate reproduction of the material, which includes sound level. It can require a good bit of output to properly reproduce an organ or piano, and having sufficient output capabilities to handle dynamic peaks that occur in well recorded source material is also required. For example, it takes a fair amount of displacement to accurately reproduce the 18hz organ in Planet Kryptonite. "Sound quality" and "loud" go hand in hand as an inability to reproduce the material at realistic levels would be a failure to achieve the initial goal of sound quality. Too many people (not necessarily you, just in general) equate "sound quality" with "quiet". That said, there is a large difference between designing a system with sufficient capabilities to reproduce the source material at realistic levels, and the typical use of the term SQL which is all too often supposed to mean "Hey guys I'd like to be able to hit 145db on music without it sounding like total crap"....which has no semblance of sound quality, hence the problem with the term "Sound Quality Loud".

There is nothing to be gained sound stage wise from having the subwoofer mounted in front of you.

That statement is so horribly inaccurate it's painful. It will completely depend upon the specific speakers being installed. Especially in car audio where the vast majority of drivers are designed to work optimally IB. Most companies want the consumer using their product to obtain the best performance possible from their products. Most car audio companies understand the vast majority of consumers are just going to toss speakers in their door, and as a result design their products to perform best in such an environment. Are there some car audio speakers that may perform better in an enclosure? Yes, it's possible. But to make the statement that an enclosure will "yield the tightest bass with most components and cleanest SQ" and state it as a fact as opposed to opinion (which is evident from the first part of your statement, "regardless on opinions") is simply a display of immense ignorance. It is far more likely that they were designed to perform optimally IB than in an enclosure. I also think that a tweeter should be mounted backwards...max reflectivness for the square wave X- E=MC3 crist dude...if someone states "regardless of opinion" on the internet you Don't take it seriously .....LOL it definately gave this thread a kick start though.... The problem is other people who are less experienced may read a statement that's worded as though it's fact, when it is not, and consider the information trustworthy. This is how all of those myths continue to perpetuate. Which is why it's important to denounce those inaccurate statements when they are made.

That statement is so horribly inaccurate it's painful. It will completely depend upon the specific speakers being installed. Especially in car audio where the vast majority of drivers are designed to work optimally IB. Most companies want the consumer using their product to obtain the best performance possible from their products. Most car audio companies understand the vast majority of consumers are just going to toss speakers in their door, and as a result design their products to perform best in such an environment. Are there some car audio speakers that may perform better in an enclosure? Yes, it's possible. But to make the statement that an enclosure will "yield the tightest bass with most components and cleanest SQ" and state it as a fact as opposed to opinion (which is evident from the first part of your statement, "regardless on opinions") is simply a display of immense ignorance. It is far more likely that they were designed to perform optimally IB than in an enclosure.

Car audio drivers are typically designed to perform optimally without an enclosure. You would have to email JL Audio and obtain the T/S parameters to determine what if any enclosure size might "improve" performance.

First you need to know the actual outside diameter of the tube. If you have 20.75" internally & need 8" of clearance, then you can only have 12.75" of port inside the enclosure. Then the volume of the port inside the enclosure would be; V = Pi * r^2 * h Where r is the radius of the OD of the port and h is 12.75" You would then subtract V from the 5.38cuft of enclosure volume you've already calculated, so you would have; 5.38 - V = net enclosure volume You would then use the following formula to calculate how much total port length you would need; Lv = (Av*1.84*10^8)/([Vb*(Fb/0.159)^2] - 0.823*sqrt(Av)) Where Av = area of the port, Pi * r^2 Vb = net enclosure volume Fb = desired tuning frequency It's basic math, you can work out the calculations.

MECP certification is a joke and most of the better shops realize this.