Crown Xti4002 Pro Stereo Amplifier Review

[Ziofrenko]

That's even more impressive...LoL. I was wondering about the heatsinks and such and figured hey! They really packed in the quality. No wonder they have a fan for cooling.
EDIT: So it's a switching power supply with class AB. Very unusual.

Absolutely not!
Before the concrete and reliable advent of class D it was the best weight/power ratio obtainable and has been widely used since the end of '90 for at least a decade!
It's called class H, and it was much easier to obtain it with switching power supplies instead of the classic linear ones.
We went from making 250w to making 1000w with the same dimensions and weights, it was a big revolution!

 

[Doodski]

Absolutely not!
Before the concrete and reliable advent of class D it was the best weight/power ratio obtainable and has been widely used since the end of '90 for at least a decade!
It's called class H, and it was much easier to obtain it with switching power supplies instead of the classic linear ones.
We went from making 250w to making 1000w with the same dimensions and weights, it was a big revolution!

IC... Thanks for heads up.

 

[Ziofrenko]

But I always view them as their long term cont output, not their rated spec. The K10 is a 1500w amp in my eyes, at least on 120v, etc..

K10 is a 3500/4000W amp in my eyes, couse forcing any normal amplifier to work at 2 ohm on the subs is criminal... Excluding welding machines such as the 10001 or the crown 10000 specifically built to work at 2 or 1 ohm.
X4L and IPAL systems fortunately, as I already said, they passed the Problem.
P.S. Have you ever tried to lower a track by 6dB in 15/20 seconds?! Few will notice that the volume has dropped, especially at high sound pressures!! Even the ear compresses

 

[Ziofrenko]

IC... Thanks for heads up.

A simple, and low cost/low quality, example Is the t.amp tsa 4-1300: about 900W at 8R and 1400 at 4R on 4 channel in about 13kg!! Modern class H amp...

2004 amp from a cheap Italian brand: 650w at 8R and 1200 at 4R in 12kg.

https://reverb.com/it/item/82797176-proel-psw2600-power-amplifier

 

[ryanmh1]

View attachment 300329

Considering that I am using a shared household outlet (12 gauge feed but 15 amp rating) this is impressive amount of power and consistent with company specs more or less.


I then threw the PowerCube at it to see how well it does with both reactive and loads going down to 2 ohm. As if to to say, "come on, give me all you have" the amplifier made all kinds of noises and lit up its red LEDs in protest. But still managed to produce numbers that are just unbelievable:
View attachment 300331

Yes, the amplifier produced nearly 90 volts out of its speaker terminals (both channels driven). And didn't care one bit what load I fed it! To put this in context, this is how much power we have:
View attachment 300332

Stunning! Note that the measurement only lasts long enough for the analyzer to capture it so likely less than a second. But still, the amplifier robustly fought the difficult load and peaked to nearly 8 kilowatts at 2 ohm load!!! It never went into any kind of protection and just ran.

I've checked a number of these reviews now with the Powercube measurements when I had a minute or two, and I'm pointing it out here again since this is not a Class D amp. The other I commented on was a Hypex. I thought it was perhaps an issue with the Powercube interacting with the Class D output stage, but it's not that since this is a rail switcher. The Powercube testing is reactive and capacitive loads is great, along with adding a 2 ohm burst capability, but the results do not make sense in many of the reviews which show near perfect cubes. The same is true here. There was a Purifi which did it too, and a handful more Hypex as well.

As far as I can tell, no one has noticed this issue yet. Having complex load result is fabulous, but not if the results are wrong or suspect. The test protocol that Audio Precision uses and which the Powercube uses for the two tests above are hypothetically identical (despite the named standard differing, the protocol is the same), both using 20ms 1kHz tonebursts. The reported power results, however, are (again) not the same. Instead of the ~1200W that APx reports at 4R, Powercube is reporting a perfect cube and 1958W at 4R. Crown's spec sheets have gotten laughably bad, but they also report 1200W of "Minimum guaranteed power, 1kHz" whatever that means. Burst? Continuous? Who knows. But at 2 ohms, they claim 1600W, not 4,000(!). I can't imagine if there was also realistic scenario under any sort of actual real benchmark they would have missed that trick of claiming an amp with a 8,000W dynamic power. (The whole pro amp industry has gotten just about as sketchy as the car amp industry, with many having borderline meaningless spec sheets.)

All of these weird results with "perfect" cubes, numbers that don't match up to spec sheets, disparate results between systems, leads me to believe there is something amiss with the Powercube results. Audio Precision is much higher volume, trusted, and less likely to have gotten this wrong. Whether a stimulus protocol error or a graphing error or a measuring error (or PEBKAC error, but seems unlikely), I have no idea, but there has to be some sort of bug going on that Audiograph needs to iron out. Sometimes the results seem valid and the two systems mostly match up, other times not so much. That shouldn't be.

 

[Old_School_Brad]

I've checked a number of these reviews now with the Powercube measurements when I had a minute or two, and I'm pointing it out here again since this is not a Class D amp. The other I commented on was a Hypex. I thought it was perhaps an issue with the Powercube interacting with the Class D output stage, but it's not that since this is a rail switcher. The Powercube testing is reactive and capacitive loads is great, along with adding a 2 ohm burst capability, but the results do not make sense in many of the reviews which show near perfect cubes. The same is true here. There was a Purifi which did it too, and a handful more Hypex as well.

As far as I can tell, no one has noticed this issue yet. Having complex load result is fabulous, but not if the results are wrong or suspect. The test protocol that Audio Precision uses and which the Powercube uses for the two tests above are hypothetically identical (despite the named standard differing, the protocol is the same), both using 20ms 1kHz tonebursts. The reported power results, however, are (again) not the same. Instead of the ~1200W that APx reports at 4R, Powercube is reporting a perfect cube and 1958W at 4R. Crown's spec sheets have gotten laughably bad, but they also report 1200W of "Minimum guaranteed power, 1kHz" whatever that means. Burst? Continuous? Who knows. But at 2 ohms, they claim 1600W, not 4,000(!). I can't imagine if there was also realistic scenario under any sort of actual real benchmark they would have missed that trick of claiming an amp with a 8,000W dynamic power. (The whole pro amp industry has gotten just about as sketchy as the car amp industry, with many having borderline meaningless spec sheets.)

All of these weird results with "perfect" cubes, numbers that don't match up to spec sheets, disparate results between systems, leads me to believe there is something amiss with the Powercube results. Audio Precision is much higher volume, trusted, and less likely to have gotten this wrong. Whether a stimulus protocol error or a graphing error or a measuring error (or PEBKAC error, but seems unlikely), I have no idea, but there has to be some sort of bug going on that Audiograph needs to iron out. Sometimes the results seem valid and the two systems mostly match up, other times not so much. That shouldn't be.

I think you might be onto something here. Given the amount of capacitance required to deliver those power bursts, it does seem questionable. According to my calculations, supplying 3,900 W for 20 milliseconds at 88.6 V would need around 20,000 uF of capacitance per channel.
The XTi4002 looks like it has a 7800 uF per channel which would amount to 1,530 W at the same conditions. This aligns far better with the specifications where a just 2 V higher voltage than the measured 88.6 V would make it an even 1,600 W per channel.
Theoretically.