Amp power draw

[themblues]

I have a question that's more technical overall so I thought I would post here.

I recently purchaced parts for a Sub project: Dayton Titanic MkIII 15" driver, Velodyne SPL-II amp, Def Tech PF15TL+ case. I can't justify the labor or cost for this reason: 50 watts. That is the max draw I'm getting on the SPL amp no matter how hard I push it according to my watt meter (Kill-a-watt basic, a crappy gadget for this I know, but it reads somewhere in the realm of where the draw is.) I started wondering about this after looking into getting a Crown XLS5000 amp and it only had a theoretical draw capacity of 2200-2400 Watts (110-120V x 20 amps) and that amp is rated for 2500 watts *per side*.

On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,) hence my question. :aureola:

So what's the deal? How are these amps "rated"?

[Glen B]

Amplifiers draw current in pulses. I opine the 50 watts you're reading for the SPL amp is only a continuous average current draw. The response of the Kill-A-Watt is not fast enough to read and display the peak current draw. With regard to the Crown amp, it is rated at 2,500 watts per side @ 2 ohms, but remember that is peak power, not continuous power. It is possible for an amp to deliver that much power into the load for a few milliseconds -- a 20A circuit will deliver the necessary current needed by the amp for a few milliseconds at a time without tripping the breaker.

[Dual-500]

What Glen said for starters.

Music has a peak to average ratio of somewhere in the neighborhood of 5-1 to 10-1 depending upon the program material.

An amp is ~70-90% efficient in terms of output -vs- input and the power supply stores energy - more for old school vintage amps. The stored energy in the power supply will smooth out the line surge demand for the amp. The energy lost in the amp is heat.

The (efficiency of the amp) x (demand in output) to the speakers will determine the line demand of the amp at any given time. There will be a slight lag in current demand caused by the energy stored in the power supply. The lag is short in terms of time and would take test equipment to measure and mentioned for reference only.

As far as manufacturer amp ratings go, you already pretty much summed it up: "On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,)"

With amps, essentially it boils down the Size Matters all other things equal. And, quality is quality. I would agree with your assessment of the two amps without seeing either given they likely have the same basic technology within them.

[Sir Terrence the Terrible]

I have a question that's more technical overall so I thought I would post here.

I recently purchaced parts for a Sub project: Dayton Titanic MkIII 15" driver, Velodyne SPL-II amp, Def Tech PF15TL+ case. I can't justify the labor or cost for this reason: 50 watts. That is the max draw I'm getting on the SPL amp no matter how hard I push it according to my watt meter (Kill-a-watt basic, a crappy gadget for this I know, but it reads somewhere in the realm of where the draw is.) I started wondering about this after looking into getting a Crown XLS5000 amp and it only had a theoretical draw capacity of 2200-2400 Watts (110-120V x 20 amps) and that amp is rated for 2500 watts *per side*.

On a side note: the Velodyne amp is positively whimpy compared to the amp in the Def Tech which is double the size & WAY better built. The Velo amp is weighs in a whopping 7 lbs tops (including the plate) and is supposedly double the power. I don't really believe it at all (they seem equally matched power-wise,) hence my question. :aureola:

So what's the deal? How are these amps "rated"?

I will tell you this much, the more power you give to a subwoofer, the better it will sound. Bass frequencies require a lot of power to get the deep bass in the room, and the more power you have the less chance of overdriving the amp, which lowers distortion, and makes for better sound quality over all. The Velo's use DASH amp, so its size will tell you very little about its power output abilities.

What Ohm rating are you testing the SPL II amp?

(must be hot as hell in Walnut Creek, cause it is hot as hell in San Leandro!)

[blackraven]

The Velodyne uses a Class D amp. You can't judge it by its weight. It's a digital amp and they weigh very little and generate little heat. I've heard the spl velodynes and they put out plenty of power. You can't judge a book by its cover!

The Velodyne amp is 95% efficient and is rated at 1,000 watts RMS and 2,000 peak!

http://www.velodyne.com/vproducts/docs/spl%20series%20II.pdf

[themblues]

That has put all my fears to rest. In that case I may continue the project! Thanks!!!

In the amp comparisons, thanks as well. My feeling is that the Velo and the Def Tech are equally matched as far as SQ and SPL. The Def Tech hammers out some serious bass for a 500W rating and the amp is built like a tank.