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Plate Amps: SpeakerPower SP1-4000 vs. Minidsp PWR-DSP1

post #1 of 10
1/30/13 at 4:34pm
Thread Starter 
Guys,

I need some advice. I need a plate amp to drive a sealed LMS-Ultra 5400 build (3 cu ft; wired for a 4 ohm load). I want to maximize the low frequency capabilities of the sub for home theater use. I was about to pull the trigger on the Minidsp PWR-DSP1 amp, which is rated at 2400 watts RMS and has built in DSP. This uses the pascal amp module (discussed below) which is the same module used by Funk Audio. Anyhow, I came across the following comparison posted in the recent SpeakerPower thread where Brian (the owner) stated the following regarding amp capabilities:

Pascal Xpro3 CH1 only 120VAC mains
1400W/4 1KHz 1% for 2 seconds, dropping to 223W after that
730W/4 40Hz 1% for 10 seconds dropping to 223W after that. Lower frequencies are even worse.

Lab Gruppen FP14000 120VAC mains
3000W/4 for 200 milliseconds dropping to 1500W/4.
4800W/2 for 80 milliseconds dropping to 1500W/2
Yes that's right. Milliseconds. Thousandths of a second.

SpeakerPower SP1-4000 120VAC mains
2400W/4 40Hz 1% indefinitely
4000W/2 40Hz for 4 seconds, dropping to 2000W/2

If "real life" performance is the primary concern, should I go with the SpeakerPower amp? This comparison seems to suggest that the Minidsp Amp (based on the pascal module) is no where near as capable as the SpeakerPower amp. Can anyone help me make an informed decision here? If I go SpeakerPower, then I would have to order a balanced Minidsp to EQ the low end.

Thanks!
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post #2 of 10
1/30/13 at 5:03pm
I'd probably stick with the speakerpower amp, more proven imo. I don't know of anyone that has used the minidsp one.
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post #3 of 10
1/30/13 at 5:50pm
Thread Starter 
I'm with you regarding the SpeakerPower reputation. What about the specs cited above? Would this translate into noticeable differences for my HT experience?
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post #4 of 10
1/31/13 at 9:24pm
What's missing is data points between the small time for which max power can be delivered and the amount of continuous power.

I'd actually be fine with the Pascal, as max power for a couple of sec is plenty.

The average power of any program material that demands full power on peaks is several dB less, which is to say a fraction of it.

Personally I wouldn't buy an amp that can supply full power continuously, as I'd be paying for something I'll never use.
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post #5 of 10
2/1/13 at 7:14am
Thread Starter 
What about the fact that the pascal module doesn't appear to produce its max power at all? It looks to be pretty far off its advertised mark of 2400 watts, at least based on the numbers above. I'm curious if this would be a problem at the really low frequencies (below 40Hz). Also might it be limiting for EQ if you want a flat response down to 10 or 15Hz since it will require boosting up the low end?
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post #6 of 10
2/1/13 at 7:31am
Noah,
The difference is that we are often directly comparing ratings between amps yet one might be a 50ms burst at 1khz, a second might be capable of the rated power for 1 full sec 20-20Khz. A third might be capable of full rated power 20-20khz indefinitely (Let us call that 30sec or more.)

Now if the first and second amps were rated the same way as the third they would have a greatly reduced specification. You can say that full power for 30sec isn't required in any actual source which is true so the first two amps are rated more appropriately which again may be true. However it goes both ways and it stands to reason that most amps rated for actual continuous rms power over wide bandwidth will achieve a significantly higher power rating if using a 50ms 1khz burst instead.

IMHO there is no need to be able to weld with the amps for audio use unless you are doing the type of testing I am where it does come in handy. However amps that can't sustain full rated power for even half a second are over rated. I think a realistic rating is what the amp can maintain for 3seconds or so. This is higher duty than 99% of audio material but not completely unrealistic.
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post #7 of 10
2/1/13 at 11:07am
Quote:
Personally I wouldn't buy an amp that can supply full power continuously, as I'd be paying for something I'll never use.

Agreed
Quote:
The difference is that we are often directly comparing ratings between amps yet one might be a 50ms burst at 1khz, a second might be capable of the rated power for 1 full sec 20-20Khz. A third might be capable of full rated power 20-20khz indefinitely (Let us call that 30sec or more.)

VERY hard to compare even if you have the equipment, knowledge and desire to do so.
Quote:
However amps that can't sustain full rated power for even half a second are over rated. I think a realistic rating is what the amp can maintain for 3seconds or so. This is higher duty than 99% of audio material but not completely unrealistic.

Along the same lines, I proposed at my session on Specifying Class D Solutions at the Audio Engineering Society a couple years ago a three number power spec based on hold time: How much power will the amp deliver for 40ms (a drum beat), 4 seconds ( a crescendo) and 4 ever (until thermal). With this information you can decide if the amp power is right for your application. Full range systems systems can use a high ratio of short/medium term to long term power efficiently. But at very low frequencies and demanding types of music or sound effects you need higher medium and long term power capability to avoid the amp gacking ( that IS a technical term). This latter category of amp is hard to find these days because it is more expensive to make and why bother if people can be fooled with bogus specs?

Brian
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post #8 of 10
2/1/13 at 4:05pm
Ricci, Brian, well said.

"Gacking" is a new one on me; what's it mean?

I trust it's not any of the meanings given onb the 1st page of google hits.
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post #9 of 10
2/1/13 at 5:08pm
Quote:
Originally Posted by noah katz View Post

Ricci, Brian, well said.

"Gacking" is a new one on me; what's it mean?

I trust it's not any of the meanings given onb the 1st page of google hits.

I'm picturing nickelodeon's old show "you can't do that on television" with some green slime. Either that or something dirty on the 1st page of google results.
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post #10 of 10
2/1/13 at 5:09pm
....and the google results were..... entertaining.......
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