So if I'm starting from Scrath... would I be better served going with a 2 channel AB or a class D mono Amp? Or are we back to the age old question of what subs I'm I wanna get and how much I want to spend?
First is the power requirement, making sure it's met. An AB amp will give better SQ because they're more linear and have less distortion, but the Class D is much more efficient (AB is usually 50-60% efficient, D is 80-90%) resulting in less current draw and less heat, also usually smaller amps. Class D amps also are cheaper per watt than an AB with the same power. Lower frequency distortion is hard to recognize and the difference is really up to your ears, Class D amps are getting better by design and really, most people don't notice a difference in SQ.
Amplifier Classes There are five main amplifier designs: Class A, A/B, B, D, and Tube amplifiers. All of these but tube amplifiers are considered "solid-state."
Class A amplifiers are the most sonically accurate. On the other hand, they have some drawbacks that make them not be the most common choice. Class A amplifiers use only one output transistor that is turned "on" all the time, giving out tremendous amounts of heat. Class A amplifiers are very inefficient (~25%). More heat means more heatsink area, so even though most class A amps have built-in cooling fans, they are big. Pure class A amplifiers are usually expensive.
Class B amplifiers are the most common and use two output transistors. One for the positive part of the cycle and one for the negative part of the cycle. Both signals are then "combined". The problem with this design is that at the point when one transistor stops amplifying and the other one kicks in (zero volt line), there is always a small distortion on the signal, called "crossover distortion". Good amplifier designs make this crossover distortion very minimal. Since each transistor is "on" only half of the time, then the amplifier does not get as hot as a class A, yielding to a smaller size and better efficiency (~50%).
Class A/B amplifiers are a combination of the two types described above. At lower volumes, the amplifier works in class A mode. At higher volumes, the amplifier switches to class B operation.
The class D amplifier (known as digital amplifier) is the last of the solid-state types. These amplifiers are not really digital (there is no such thing), but operate similarly in manner to a digital-to-analog converter (DAC). The signal that comes in is sampled a high rates, and then reconstructed at higher power. This type of amplifier produces almost no heat and is very small in size. Efficiency is much higher in class D amplifiers (~80%). The sound quality of a Class-D amplifier is much lower than that of other solid-state amplifiers, which is why Class-D amplifiers are only used for subwoofers in car audio. This is because the switching speed of the transistors, and lower sound quality are masked by the lower frequencies being reproduced by the subs, since distortion is harder to discern at low frequency.
Lastly we have tube amplifiers, which aren't often used in car audio. Tube amplifiers have about 50 to 60% efficiency. Tube amplifiers are said to sound more musical. The reason is that tube amplifiers produce even ordered harmonics. Musical instruments give off harmonics in even orders. Transistor amplifiers tend to give off harmonics that are odd ordered. These harmonics are not pleasing to the ear as second order harmonics are. Modern solid state amplifiers have very low distortions but their distortions are less tolerated by the ear than even ordered harmonics. This means that when you hear someone say a Tube amp is "warm" sounding, they are actually talking about the second order distortion produced by that tube amplifier, which they find pleasing to the ear. A good example of this is in guitar amplifiers, which often pride themselves on their second order harmonics. One should note that while most solid state amplifiers have very low distortions (Total Harmonic Distortion) for the left and right channel, other channels are often much higher as these specifications are rarely noted. Subwoofer amplifiers are particularly bad at creating odd ordered harmonics. I believe that the best tube and solid state amplifiers sound amazingly alike. Bad tube amplifiers sound tubby and slow. Bad transistor amplifiers sound harsh, bright and strident.
Just like you can't judge a good book by its cover, you can learn very little about an amplifier without digging in and seeing what is inside. Generally speaking, the most important component of any amplifier is its power supply. Is it sufficient? Is it accurate? Is it fast? Unfortunately, almost no amplifier company talks about their power supplies or what transformers they use (An example of a good company would be Eclipse, who uses dual toriodal transformers in their amplifier power supplies.) I think most manufacturers would prefer you not ask.
I hope this clears up some of the more frequent questions regarding amplifier classes, as well as tube versus solid state amplifiers.
class D is good for subs. relatively low price-per-watt, adequate sound quality for the job, small footprint, low heat, and available in larger power classes that you just can't get in class A/B.
that's pretty much the way to go for subs these days unless money is literally no object.
the only problem with class D amps are that it will tear up you speaker if played really load all the time,Becouse it over heats the voice coil 2-3 times as fast. so make sure you got tough subs
actually to clarify that, class D amplifiers have a steep increase in distortion at near-peak output. distortion will cause the coil damage. Most people never come close to the full output of a decent amplifier, since every time you double the audible volume, you're increasing power by a factor of ten.
It's nice to have people that know their Sh*t. Okay. I bought a MTX 801d today. I'm assuming this should be ample power to push either 2 Shivas or Vmax's in a sealed box.
Can someone (perferably Glass or Jon)explain the Shiva's thermal rating of 375w per vc? Adire's site says much less power will push the woofer to full excursion. So is my 400W rms per sub going to be too much power, right on, or not enough?
Plenty of power, shouldn't be too bad. It depends on the size of the box, the larger the box, the less power handling the sub will have. The Shiva will generally reach full excursion in a 1.5-1.75 cu ft. sealed box with around 300W RMS in many cases. 400W RMS should be fine with them.
Pardon my ignorance, but i've only ever had a single sub sealed box. For a dual sub sealed box is it one big cavity or are the spaces separated for each sub?
I'm assumiing that's 1.5-1.75 per sub....since all the specs are in metric measurments on their site, was hard to tell.
either way. you can divide the box or share space. the only real difference is that if one sub fails, a divided box will help protect the second sub.. otherwise when one sub fails, the second sub now has a box twice the normal volume, with essentially a passive radiator if the first cone isn't frozen.
regarding thermal rating, power handling ratings on a speaker are the amount of heat (in watts) that teh coils can handle without thermal damage. the amount of power the speaker really requires to reach peak performance can be significantly less than the thermal power handling rating. this is a common mistake made by people.. they think the "power handling" is the amount of power the speaker "needs" or "draws" in order to work at it's best. not teh case.
class T. blah. it's a full-range class D amplifier with minor changes in topology. It's not the wave of anything. I'm not that impressed with their performance at all compared to a good class AB amp.
For for the VMAX rated at 300wRMS the MTX 801D isn't going to be too much, in a sealed box?
I'm not so much worried about the Shiva, it's at 375w per coil. Or should I be?
Last thing, both of these subs should work well in sealed or ported applications (Jonathan has already suggested some box specs) right? I'm gonna start with sealed because it's cheaper, but If I don't like it, it shoudn't be a problem to change to a different box? Is the MTX 801d going to be too much power for these subs in aported application?
You input is going to decide the fate of my setup! (Sort of, already bought the amp)
You may overpower the Vmax with one. The amp will push either to full excursion in either box, and the if the Shiva is in a small enough box, or if you get a Subsonic filter for a ported box, 400W RMS could be just right if the box controls the cone enough. In the normal application, 400W RMS is more than enough. If you're careful, you won't damage either sub. Back off if you hear the sub distorting and going beyond it's limits. Class T is overhyped really and may be the future alternative for those who can't afford a good Class AB amp with high power, I wouldn't take one over a good AB amp for components. The only alternative over class AB (which I may do if I ever upgrade again) is a vacuum tube amp, although uncommon in cars, tube amps from US amps and Butler are fantastic if you like the sound of a tube, which I love.
Glass, what's wrong with Zapco's C2K series? believe me in street max, the zapco will be MUCH more efficient than an AB, thus a much higher score. why wouldn't it impress you? don't you want maximum output of what you put in?
Well, it would be 2 subs.... Would you suggest since now I alrady bought the amp that I look for some subs that can handle some more power. I'm looking for something that's pretty idiot proof.
I've been looking @ the Orion P12s or the Diamond Audio CM3 12s. They handle considerably more power (500wRMS).
the C2K 9.0XD and 4KW are class D amplifiers, but still full range. They aren't actually class T. They are good amplifiers, and one of the only class D amps rated to handle full range with acceptable performance. You can also set teh output peak power on those amps via programming to limit their output to both match your speakers, and to avoid that distortion I mentioned at near-peak output. Class-T are mroe like the amps Blaupunkt hypes as the new greatest thing. They're ok on a cost level, if you're strapped and need lots of power for some reason, but really I'm more about SQ than I am raw SPL, and in IASCA events where SPL is capped at 130dB, and it's all about install, innovation, imaging, soundstage, etc.. I use all class AB amps throughout, and don't worry about their lacking efficiency. Yes they draw a LOT of current, but they're clean as can be. I use three Orion XTR2250 amps. two bridged to 1Kw each with a dedicated RE triple X 12" on each, and the third in stereo mode running 250w x 2 @ 4 ohms to the DynAudio System 360 front stage. It sounds terrific, and in a fastback '66 muscle car, it gets plenty loud for daily use. There are plenty of people with louder cars, but SPL events are like dragracing events.. it's all about "cubic money." the people with more money (factory sponsored, pro etc) win. They can afford to do pretty much anything they can dream up, where most people are realistically limited to retail pricing and a dayjob. Talk to most pro circuit top contenders these days and ask them if they had to pay full price for everything they're using. Car, stereo, etc.. see how many say yes. lol
Chief, Class D and T amps will really only be very good for audio reproduction when audio goes full digital. Class D amps don't amplify an analog signal as Class AB amps do. How is it different? Typical Transistors such as from Class A, B, and AB amplifiers have the signal applied directly to them, and the bias of the transistors is what amplifies the signal, and the output signal is directly proportional to the input signal. What Class D amps do, as Glass said, is take the signal that comes in, samples it at high rates, and then reconstructs it at higher power. How it produces a signal is by switching voltage values, (the amp has two voltage rails, one positive, and one negative, and the size of these rails determines the amps output power). This is why Class D transistors are usually referred to as switching devices. The power supply voltage determines the amount of amplification, and the gain and volume adjust the power supply voltage accordingly. The transistors switch between voltage rails, one being positive and one being negative. The reason for their efficiency is because when either of these transistors are on, all the power is dropped across the load (speaker) instead of the transistor, so theoretically they would be 100% efficient(although they aren't). This also limits the amp to only be capable of amplifying two-valued waves (binary, positive and negative, because you have a positive voltage rail and a negative voltage rail). Analog signals can assume any value at any frequency, so how does a Class D amplify analog signals accurately? Through Pulse width modulation usually. Basically, the amplitude of the input signal determines the percentage of time that a transistor will be on(this is called the duty cycle). The input signal goes through an analog comparator, which converts the analog signal into a binary waveform (this is the information that was originally on the CD you're using, you're converting back to the original signal), a binary waveform is a triangular waveform (continuously switches from high to low value, pos to neg /\/\/\/\/\) that would be the equivalent to an analog audio signal. The result is a signal that generates the same information as the analog signal, but allows the amp to produce it with just two (pos and neg) values. Basically, Pulse Width Modulation acts as a binary control signal that switches the transistors on and off depending on the amplitude of the analog input. This determines what frequencies are reproduced and how much power they're generated with. This switching also generates LOTS of noise in higher frequencies, which is why Class D amps are typically used on subs. The high frequency range (where switching occurs), which is heavily amplified through the PWM process, would overheat the speakers horribly if that information was allowed to reach them, meaning the amp uses a LPF to keep this information out, and smooth the output wavefrom from this switching. MOSFETS are the only way to go with Class D amps (for now, anyway), because of their switching capability, they are efficient, have low loss, and switch fast. Kind of complicated so far, isn't it? Especially complicated compared to traditional A, AB, and B amplifier design. As you can imagine, with this complexity comes error. A Class D amp generates a lot of distortion when compared to an A, AB, or B class amp. It does this in a few ways, the first is because the power supply isn't regulated perfectly, note that this doesn't mean a regulated amplifier will fix the problem. There is no way to get a perfectly regulated power supply, especially in a vehicle (at least not now with current technology). You can come close, but it won't be perfect. The output of the amp is directly proportional to the power supply, and unlike an AB amp etc., the generated output signal will deviate from the input signal because of this, and AB amp will not deviate in this way because the transistor directly amplifies the input signal and doesn't depend on the voltage rails or a converter to generate a signal. This deviation shows up as distortion, power line ripple, noise or hum. The power supply needs to be designed exceptionally well to combat this problem. Timing error of the transistors generates distortion as well. Of course, the transistors won't be perfectly matched (there will ALWAYS be error, close tolerances are key to better sound quality, but there will always be little differences). The time it takes for either transistor to turn on or off generates distortion (known as crossover distortion, this also occurs in AB and B amps, but not nearly as severe) The worse the timing is and the higher the switching frequency, the worse the distortion is (another reason Class D amps sound poor on anything but low freqs.) The reason you have higher distortion with higher freqs. is simply because the transistors have to turn on and off more often, so error occurs more and it is easier to pick this up with higher frequencies. Class D amps also have trouble producing flat response, because without correction, they only do so at a specific load (4 ohms, 8 ohms, etc.) and EVERY speakers impedance will change at given frequencies. MOSFETs are very non-linear, this is why the flat response isn't seen on a Class D, although different methods are getting closer to a flat response, such as with Analog Feedback systems. Why did I say they'll be good when we go full digital? I honestly don't think they'll ever be as good as a well built Class A, AB or Tube amp for sound quality, at least not anytime soon, but they'll get very close. For example, when you play a CD, a digital to analog converter converts the signal into an analog waveform, this is to accomodate the 99.999% of people who will have an analog amp on mids and highs (Class A, AB, B, etc, and also the amp in a head unit itself). But, in the future when Class D and T amps become the most widely used, you will see head units that directly feed the digital information straight to a digital amplifier, such as Class D and T amps. Currently, the head unit converts Digital to analog, then a Class D or T amplifier has to convert analog back to digital. With head units sending a full digital signal to the amp, it will eliminate the process of converting through pulse width modulation, and the signal will be sent directly to the transistors, eliminating a lot of the current issues with Class D and T amps. There will still be the issue of transistor switching timing error, although not nearly as severe as before, but still worse than Class AB and B amps. Power supply regulation will still be a big problem, until methods are improved for achieving near-perfect supply method. I know this is very long, but a lot of people are mystified by the magical operation of a Class D amp and it's hard to find info. Note that this explanation above is among the simplest of Class D operation, they are getting more exotic and thus, more complicated and I haven't explaned everything that occurs in more current Class D amps. This is a general tutorial, believe it or not. I personally prefer simpler devices, because this nets better reliability and sound quality, which is why I'm not hyped up about Class D and T amps be "the amp of the future" as they're complicated and have known issues. It's not terribly expensive to go buy an alternator, and the efficiency gain, to me, just isn't worth it.
Would anyone suggest since now I alrady bought the amp (MTX 801d) that I look for some subs that can handle some more power. I'm looking for something that's pretty idiot proof, that's why I chose a sealed enclosure.
Considering 2 Orion P12s or 2 Diamond Audio CM3 12s. They handle considerably more power (500wRMS).
I'd stick with the Shivas, if you do two Shivas with about 2-2.5 cu ft per sub (net volume) tuned to 30-35 hz, then use Fmods for a subsonic filter, you'll reach full excursion with no damage to the sub.
Q: did you type all that up yourself? (that's a lot)
BUT IMO in the future amps will have such low of an error that the efficiency may be worth changing to. BUT if your ears don't need that much power/sound to fill them, than a class AB amp will always do it for you.
Okay....I will seriously consider ported. That's what a couple of people have told me. Thanks for taking the time with all my "what if" crap.
Doesn't the MTX 801d already have subsonic filter? The below is listed on the spec sheet.
Isn't the item list as Frequency Control the "subsonic filter". Or is it just not suited for the specific application.
Thunder EQ -- This equalization circuit is used to enhance the low frequency response of the vehicle's interior. With up to 18dB of boost and centered at 40Hz, the Bass EQ can be adjusted to meet your own personal taste.
Frequency Control -- This control is continuously adjustable from 40Hz through 200Hz at 24dB per octave. Factory setting is at 40Hz.
No, the frequency control is a low pass filter, Harrison labs makes a product called FMods, basically it connects between the RCA wire and the input of the amp, very simple, choose your frequency, and just plug it in. That'll get you set. Chief, yeah I typed it, took a while, but a lot of people have emailed asking about Class D amps, so I figured I'd clarify it's operation since it's such an unknown subject to many. Class A, AB, and B amps are much easier to understand. The Class D and T amps of the future may get better, but they'll need a lot of research and better materials than currently available. You have to consider that Class A, B, and AB amps will evolve as well, so it's a tough call whether the upgrade will eventually be worth it. Tube amps are going to be my next audio upgrade if I ever upgrade again, I love the sound of a tube and a well designed tube sounds better to me than all of them. Just not common in car audio, and not cheap. You won't get as much power out of one, the highest powered tube amp I've seen was by Butler, it was 150x2 at 4 ohms, 500x1 at a 4 ohm bridge, not sure of other companies, I know US amps makes a 4 channel tube that may have a bit more total power, but that's because it's a 4 channel.
I've found these FMods for about $25 + shipping. Does that sound about right ? The ones i've found say like 30hz High Pass. Would this work for the 2 Shivas tuned to 30-35 hz. I'm assuming I'd want to tune the box to 30hz if I'm using a 30hz Fmod.
Can only find like 20hz, 30hz, 50hz. Do they make ones in between like 32hz or 34hz?
I don't think they come in specific freqs like that. Like you, I've seen the 20, 30, and 50 hz. 25+ shipping sounds about right. I'd do a 30 hz and tune the box around 35, it won't hurt the sub to go a few hz below the tuning frequency, it's when you get really get below it that causes the most damage. I'd set the low pass filter from 60-80 hz.
(Sort of, already bought the amp)