Need an amp 1000 watts True RMS
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jeffery Unregistered guest | I need an amp that is 1000 Wats TRUE RMS thanks for anyhelp. |
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Gold Member Username: GlasswolfNorthWest, Michigan USA Post Number: 4753 Registered: Dec-03 | at what load? how many channels? for what? |
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jeffery Unregistered guest | Load dont no probly 1 or 2 Ohms. 1 channal Class D amp For 2 12 and 2 15 V-Max's y 1 or 2 Ohms. 1 Ohm if i get the SVC or 2 if i get the DVC ones |
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Silver Member Username: FishyTamarac, FL USA Post Number: 561 Registered: Sep-04 | This brings up something I'm not sure I completely understand about amplifier ratings. Maybe Glass or someone could answer this. I learned in my Underwater Sound Propagation class a bit about impedance matching. Impedance matching basically says that you get the most power from an amplifier when you "match" the fixed(usually)internal output impedance of that amplifier to the load it is driving. At this point half of the power used is dissipated as heat(thru the amp's heatsink) and the other half is converted to "usable" power thru the load. At load impedances less than this more energy is converted to heat than to usable energy. At loads greater you deliver less usable power but even less a % of energy is "wasted" as heat. This makes a lot of sense when you consider that the typical car amplifier(disregarding the JL Slash series and other amps with separate voltage rails) produce a lot more heat when run at lower impedances. http://hyperphysics.phy-astr.gsu.edu/hbase/audio/imped.html What I don't understand is how this relates to the way different types of amplifiers are rated efficiency-wise. The most efficient amplifier used in car applications is D class witch are at most about 70-80% efficient. I guess my question is this. How is it possible for a 1000 watt D class to produce this much power with a pair of 50 amp fuses(whats recommended on the Xtant 1001dx's circuit board) with 70-80% efficiency? I guess it must have a VERY low internal impedance, much lower than the 1 ohm load it is designed to drive. If it was perfectly "impedance matched", by my calculations at 1 ohm it would be developing 2.67 kW, 1.33 kW as heat thru the heat sinks, 1000 W actual output, and another 333 W as heat somewhere else(25% reduction of efficiency for class D). There's just no way you can get 2.67 kW from a 14.4 volt power supply with only 100 amps or even 120 which is what the 1001dx actually came with fusewise. You're limited to 1.44 or 1.73 kW respectively. My only conclusion is that car amps, which unlike home versions have a relatively "limited" power supply, are never intended to run optimally impedance matched. The power requirements are just too great. Just trying to bridge the gap between theory and reality here and was hoping someone could clue me in on how things actually work. thanks  -Fishy |
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Gold Member Username: Jonathan_fGA USA Post Number: 2356 Registered: May-04 | I explained Class D in depth on this thread: https://www.ecoustics.com/electronics/forum/car-audio/84609.html Theoretically, they don't "waste" power as heat like A/B amps do(although realistically they do), making the current demand much less. A Class D isn't constantly on, it only produces audio when the signal requires it to. All amplifiers for audio are reactive and produce different impedances at certain frequencies, just as speakers are, you really can't match impedance perfectly. But anyway, the internal impedance of car audio amplifiers (A/B, A, D, whatever) is very, very low, hence the damping factor being measured. Say you have an amp with a damping of 200 at 4 ohm. That amp has an internal impedance of .02 ohms. And so on and so forth, most car audio amps have .1 ohm and lower at least. |
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Gold Member Username: GlasswolfNorthWest, Michigan USA Post Number: 4755 Registered: Dec-03 | first, amp suggestions.. look at Kicker and MTXC. the Kicker KX1200.1 puts out 1200 watts RMS at 1 ohm MTX has the 1501D and similar that put out uup tp 1500 watts at 2 ohms there's also the JBL bp1200.1 for 2 ohms or 1 ohm, since it puts out 1200 wRMS at both. also the JL audio 1000/1 which puts out 1Kw at 1.5 to 4 ohms as for amps, keep in mind that a class D amp works by sampling the source signal digitally, at a very high rate of speed, then reconstructs the signal at the output stage at a much higher amplitude. this is very different from how a class A or AB amplifier works. to put it simply, there's going to be a sweet spot for any amplifierif all you're worried about is peak efficiency, but in car audio, we honestly don't care much about that since this is for audio amplification. Within the given specs of the amp, each time you halve the load, you don't actually double the output as you noted, due to loss to heat, but since money is a factor here, we run amps at lower loads to get more power within acceptable ranges for heat and distortion, SNR, damping, etc. If you want to know more about audio amplifiers, these should help a bit: http://www.wickedcases.com/caraudio/amplifiers.html http://www.wickedcases.com/caraudio/ampspecs.html |
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Silver Member Username: FishyTamarac, FL USA Post Number: 570 Registered: Sep-04 | Ahhhhhhhhhhh...... Jonathan you are my hero. You've killed two birds with one stone for me here. You verified my hunch about very, very low internal amplifier impedances and also explained to me exactly what dampening factor means. I've pretty much understood the differences between A, A/B, and D operations just didn't get this impedance matching thing. Another deceptive piece of info drilled into my head in my quest for "Higher Education". I dunno, guess with most sonar applications you are operating at very narrow frequency bands with piezoelectric transducers so the impedance curve is very predictable. Maybe you get away with pushing such task specific amps to that level, but I really couldn't imagine 1000 watts of heat behind MY seat. Thats like having ten 100 watt lightbulbs burnin back there. Probably catch my truck on fire. -Fishy [note] so I guess them Zapco competition amps have internal impedances on the order of just a few milliohms. Wow. |
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Silver Member Username: FishyTamarac, FL USA Post Number: 571 Registered: Sep-04 | Oh, do home amps have typically about the same dampening factors as the mobile audio stuff? or can they afford to run "hotter". thanks -Fishy |
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New member Username: W_c_rontgenMiddle of Nowhere, Central WI USA Post Number: 8 Registered: Oct-04 | The JBL BP1200.1 has a truckload of power at a reasonable price if you can find one. This is the only one I found on ebay: http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=18797%26item%3D5725713028 %26%26 You may have better luck finding a new one from an online dealer. I used the 1200.1 to power my Brahma 15". However, it did not last very long. I don't know if my problem was an isolated incident or if the 1200.1 burns out fast. I had it mounted in the back of my Ford Bronco XLT which is not the smoothest ride. I only have experience with the JL 500/1, but I have been supremely happy. The price difference is significant however. http://cgi.ebay.com/ws/eBayISAPI.dll?ViewItem&category=18797%26item%3D5725810670 %26 |
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Silver Member Username: FishyTamarac, FL USA Post Number: 574 Registered: Sep-04 | Here's a factory refurbished 1200.1. http://www.cardomain.com/item/JBLBP12001Z I'd say that was a steal at 200 bucks. -Fishy |
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jeffery Unregistered guest | thanks for the help but i cant run 1200 watts that to much for my HO Alternator i could only get the 160 Amp 1 and im having it specaly made.So far i Cant find a 200 Amp. I wish i could my old alternator was 105 amp so its not much of a change. But i have 33.3 amp being pulled for my amps right now a and my lights dim just a little but i have 8g wire runing so im going to run 1/0g wire and get an Optima yellow Top. I u could Help me find somewhere that can get me a 200 amp alt. I would epeciat very much. I have a 1992 Chevey Lumina 4 Door Sadan with a 3.1 V6. |
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Gold Member Username: GlasswolfNorthWest, Michigan USA Post Number: 4768 Registered: Dec-03 | Jeff, don't sweat it. the 1200.1 would be fine. it's peak curent draw is 115A, and again that's only at absolute peak output.. since you won't be listening to the stereo at full volume with a signal generator as a source, you'll really only be using a small fraction of that power normally. average listening levels even "loud" only draw an actual 50A at most usually. Short answer, you can use the 1200.1 with the 160A alternator just fine. If you want to help it more, use a 1Fd capacitor in conjunction with the 1200.1 and 160A alternator to smooth out spikes in current demand on the alternator and supply current more quickly to the amplifier. Fishy, damping really isn't a major issue unless the amp in question is specifically for driving subwoofers. for most home audio amps, good ones anyway like Krells, Pass Labs, Brystons, etc, they're class A, high current amps, and most are made to run full range speakers. Damping won't be as big of an issue there as it is in a class-D sub amp for a car. Home amps do run hotter generally though. Look at a Krell STA-250 as an example. it's a pure class A amp that produces 250wRMS x 2 @ 8 hms the amp weighs over 200lbs, it has fins that remind me of an old Chevy bel air, and it has active cooling to handle the heat.. but man that thing sounds jaw-dropping on a pair of MartinLogan Odesseys |
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Gold Member Username: GlasswolfNorthWest, Michigan USA Post Number: 4769 Registered: Dec-03 | yet more on damping factor.. Damping Factor degradation: Using super low impedance loads on an amplifier will degrade the system's damping factor (discussed in detail below). Degradation of damping factor means that the amplifier will have less "control" over the speaker system, possibly resulting in "boomy" bass response. So, just because an amplifier has a super powerful 2 ohm rating, don't look for ways to wire up multiple speakers in order to "use" this power! Treat the 2 ohm rating as "headroom" and know that your amp has the ability to more easily handle the most difficult "normal" speaker loads that you are likely to ever encounter. If you need more power, get a second amp. Two medium powered amps are better than one monster (what if your one big amp dies? With two smaller amps at least you can still run!). Noise All amplifiers generate a certain amount of electrical noise. Generally, the more powerful the amplifier, the more noise. If you turn on an amplifier (with the input jacks disconnected) and listen to a speaker you can clearly hear a hissing sound. This pretty much represents the noise floor of the amplifier. For a powerful system, the noise might seem pretty obvious; however when actual music is playing the noise will be totally masked. All electrical circuits generate a certain amount of noise. Better designs minimize the amount of noise, however no matter how good the design there will always be some. The noise is generated by the movement of electrons in the system and cannot be eliminated (unless you chill your equipment to absolute zero!). The noise floor of an amplifier by itself is usually not obviously audible in a typical car (unless you are sitting right next to a speaker). However, the remaining components in a system (preamp, equalizer, processors, etc.) each add in some noise. So, the total system noise (when no music is playing) might be objectionable. If this is a serious problem, a device called a noise gate can be used. Such a device is essentially a "squelch" which is wired in just before the power amps (or electronic crossover in multi-way systems). The device basically cuts noise from upstream components when no music is playing. Most noise gates have adjustable controls to set the threshold at which noise cut begins and also to set the amount of desired noise cut. The noise floor of an amplifier is relatively constant, meaning it does not increase with increasing output signal (unless the amplifier has a poorly regulated power supply). In other words, the amplifier's noise floor is pretty much the same whether or not music is playing loudly or softly. So, when music is playing softly, the noise will be proportionally larger. When music is playing loudly, the noise is essentially "buried" or masked. As stated, an amplifier with a poorly regulated power supply can create some additional noise. If the filtering of the power supply is marginal, the "smoothness" of the DC power supply voltage will be degraded when the amplifier is playing loudly. This will result in additional noise being added to the system (generally in the form of alternator whine). This type of noise isn't really part of the noise floor. Such noise is often inaudible when music is playing loudly. It can be clearly heard however when playing test tones at levels near the output limit of the amplifier (don't try this unless you are thoroughly familiar with testing practices... blown speakers will otherwise be the result!) |
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classDchris Unregistered guest | Hi, The movement of the electrons you speak of constitutes but one type of noise, and only would make up the noise floor in the most ideal of systems, which I know you'll agree, is never the case. A decent amp would also surpress this enough to be totally inaudible, some even with the gains turned up, thanks to the feedback. As far as car audio goes though, I would think road noise is your true noise floor. |
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Gold Member Username: GlasswolfNorthWest, Michigan USA Post Number: 4818 Registered: Dec-03 | oh gain can make a very noticeable amount of distortion.. easily heard if the gain is set too high on the amp. I think we were just discussing one aspect though as you noted. The problem with class-D amps is the distortion curve. It peaks sharply at full or close to full output of the amp. This causes major issues with SPL competitors driving systems to peak output since they tend to shred subs quickly (every event sometimes) due to the amount of distortion being sent to the subs when burping the system. anyway that stuff aside, yeah in a moving car you can be dealing with up to 90dB of noise floor so it's not an ideal setting for an audiophile, but car environments never have been, and that's always been acknowledged. If you're after a very quiet system with a low noise floor, you'll be using noise gates anyway (Rain, USD, etc) like I have in a few installs I've done. (example: http://www.wickedcases.com/caraudio/USD-noisegates-lg.jpg) I guess it's a matter of if you're worried about audible noisefloor, or actual distortion or clipping that can cause damage to components. "noise" can cover a fairly wide range of subjects from EMI/RFI to clipping, to noise floor. good point though. |
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