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Gold Member Username: Arande2Rattle your ... Missouri Post Number: 2748 Registered: Dec-06 | I have been looking at a lot of amps, but I need info on how to select an amplifier. People have told me that I need an amplifier that can swing large currents and voltages with minimal recovery time. The use will be to power four eighteen-inch subwoofer drivers. After to the BL (took off 20%) to estimate xlim limited power input at low frequencies and adding in the estimated rolloff of my equipment, I found it takes 2500w of system input to bottom the drivers in the single digits. On the other hand, you're running at xmax at 11hz and 20hz with 1600w right before power compression starts creeping in. It takes 10kw of input to reach xlim at higher frequencies, where probably there's around 30% THD from BL non-linearity during excursion, but that's at 130dB AFTER power compression from BL/CMS non-linearity at mechanical limits has been factored in. The current amplifier I'm looking at would have the power to bottom the system below 11hz as it's rated for 4000w RMS. If bottoming ever happened, I would have to be playing the system at 125dB levels with material that has strong 5-10hz content. What I'm looking for here is help on an amplifier system to power these.. Should I split the load between multiple amplifiers on their own circuit? What should I be looking at? |
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Bronze Member Username: MagfanUSA Post Number: 68 Registered: Oct-07 | Andre I think you will severely damage yourself with 125db output at 5-10hz. I suspect you will emulsify yourself. If you hit the resonant frequency of your house, it'll collapse. Tesla claimed he could topple the Empire state building with 20hp which is about 15kw. But, if you insist:: First, Class D is your only shot at getting near that power level. You need every watt out that you put in, or at least 90%....hmmmmm. You will need a 230v or so outlet, like you were running your drier. 30A @230V is not even 7kw. That'l have to do unless you want to get 480 ran to your house. I'm sure the neighbors would talk when a transformer the size of a minivan showed up and was placed on the specially prepared concrete pad out back! Amp modules made by Hypex or ColdAmp may do. You will have trouble getting the ICE modules from B&O since they only sell to OEM and in minimum lot sizes. http://www.hypex.nl/ Look for the UcD700 http://www.coldamp.com/opencms/opencms/coldamp/products/amplifier_modules/ 'only' 400 watts. You can bridge some of these guys, too and some claim Very low impedence drive ability. ColdAmp also makes a switching PS (SMPS?) which is of very high efficiency. Don't bother to let me know when you switch this on for the 1st time. I'm sure we will have about a 6.5 out here on the left coast when you do. |
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Gold Member Username: Arande2Rattle your ... Missouri Post Number: 2749 Registered: Dec-06 | Well, I should first tell you that the 125dB linear output capability of the system is for a bunch of headroom and I don't plan to play anything at those high volumes. Besides, I really don't think I could handle that (nor the house), just like you stated. I was actually looking at more of something along the lines of a pro amp. It must have low distortion (as the subwoofers I've selected have VERY low distortion) as well. I know pro amps don't normally have very good sound quality, but I'm sure I could find one that does. The QSC RMX 5050 WAS in consideration, but people don't seem very impressed with it, so now it's not. I think I may be looking into Crown Macrotech.. I'm more interested in what I should be looking for rather than actual recommendations, unless you have a really good one. |
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Gold Member Username: Arande2Rattle your ... Missouri Post Number: 2763 Registered: Dec-06 | After a bit of looking it looks like the Crown takes the cake. The amp sheet states a 42-amp draw when delivering full power (2100w/channel -both driven-, 20hz-20khz, .1% THD). I will start with only one to power the system as I don't really think I'll need more than 4200w to drive the system, and I think you would agree. I chose these amps because people give them the thumbs up on sound quality, and these drivers and the enclosures I have designed for them are specifically designed for sound quality as well. The amp has also been chosen because it has the characteristics that someone suggested I look for in the amp regarding these specific drivers. A drawback might be that I can't keep the speaker-amp connection short. I will use the largest gauge I can, though. |
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Bronze Member Username: MagfanUSA Post Number: 72 Registered: Oct-07 | Where you gonna plug it in? |
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Gold Member Username: Arande2Rattle your ... Missouri Post Number: 2768 Registered: Dec-06 | Ahh.. I see. My dad is an electrician with a Master's License and he wired houses for many years and still does from time to time. In short, we're going to put in a dedicated circuit for the amp. I doubt a 30A circuit will be a prob since I don't really think I'll be using more than a few watts most of the time (casual listening). As you know, it's the first few watts that count. If we want reference output at 20hz with a house curve running, we'll need 47v from our amplifier to the 4.5-ohm impedance and we'll get our 124dB (115dB LFE, +5dB crossover, +4dB house curve), which is the linear limit of our drivers at 50% excursion. 15dB below reference, which is more likely, will require 21v into 2.15 ohms for 15hz at 5mm excursion and 3.5m/s port velocity. The amplifier has 200-volt supply rails and a 37.5-amp output limit in bride-mono mode. It has a 100-volt supply and 75-amp limit in parallel-mono mode. Each channel by itself has a 37.5-amp limit at 100v. The maximum outputs can be obtained at: 5 1/3 ohms in bridge-mono 2 2/3 ohms in stereo 1 1/3 ohms in parallel-mono Once you deviate from those you become limited by either current or voltage. You can run at any impedance you want, but you'll be limited by either current or voltage. Hmm... |
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Silver Member Username: WattsssupBarrie, ON Canada Post Number: 174 Registered: Aug-06 | English please.....english! Just kidding! |