Crown Xti4002 Pro Stereo Amplifier Review

[amirm]

Can you expand on that compared to various Crown amp lines?

It is a modern way to get efficiency out of class AB amplifier. You run them normally at low voltage to keep dissipation low. But then switch to higher voltage for max power. Use of powerful fans keeps heatsinks small and costs lower.

 

[Doodski]

Can you expand on that compared to various Crown amp lines?

I have not seen many Crown amps internals and so don't know about their full line-up of gear and what uses TO3 transistors.

 

[Doodski]

These are not class D but standard AB amplifier driven by two rail supply voltages.

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.

 

[pseudoid]

Thank you @amirm,

Crown and QSC are competitors.
The 400W-ish (full ClassAB w/similar pricing) QSC RMX-1450a has a pretty big toroid as the basis of their version of basic industrial PA.

Would it be unethical to rent one (or equivalent) to test?

 

[amirm]

Would it be unethical to rent one (or equivalent) to test?

I can't buy and return if you are asking that. But you all are welcome to do that. If they rent it, then it is not an ethical issue at all.

 

[JSmith]

Wow, amazing to see a modern amplifier with TO-3 transistor packaging!

Yes, quite surprising, since they were designed in the 50's. Also considering a TO-264 or 4 TO-220's would likely outperform a trusty old TO-3.


JSmith

 

[amirm]

TO-3 has wonderfully low thermal impedance and can dissipate a lot of power even without a heatsink due its much larger package. Its issue was much higher cost and hence the reason it fell out of favor.

 

[Bird_of_Hermes]

Is it possible for class D amps to be able to reach such power figures in a reliable way? Most completed amps that I’ve seen are very lacking in heat sinking and even fans (if needed). I know that the pro amp companies use class D solutions, but last I looked it was for (relatively) lower power applications.

I see one can get 2k/channel with an Ice power module. I haven’t heard good things about their reliability, however.

This Crown amp really “doubles down” to 2 ohms, unlike other amps that just lower their reported 8 ohm measurement to make it seem that way.

 

[Chrispy]

Is it possible for class D amps to be able to reach such power figures in a reliable way? Most completed amps that I’ve seen are very lacking in heat sinking and even fans (if needed). I know that the pro amp companies use class D solutions, but last I looked it was for (relatively) lower power applications.

I see one can get 2k/channel with an Ice power module. I haven’t heard good things about their reliability, however.

This Crown amp really “doubles down” to 2 ohms, unlike other amps that just lower their reported 8 ohm measurement to make it seem that way.

FWIW I don't see the "doubling down" type spec, altho it is rated for 2 ohm. I have used mine at 2 ohm for subs in any case without issue. I am not pushing continuously high power output, rather typical home needs.

 

[robwpdx]

By consumer hi-fi standards, the noise and distortion is quite high. That is not the target of this amplifier class though. It is meant to produce a lot of power and do it day in and day out. And provide in-built DSP to handle jobs like crossover, delay, etc. To that end, the XTi 4002 delivers on its promise in an impressively way -- better than any amplifier I have tested to date.

Is the reason for noise in high power Class AB or D amplifiers the additive noise of parallel output stage FETs or transistors? And/or is it hard to find low noise power devices? It appears the output stage is conventionally biased in the linear range.

The other question is, do commercial power amps use automotive-military qualified chips or under rate their capacitor voltages?

To control the fan, they must have temperature sensors, so I wonder what junction temperature on the power stage they target. The higher the temperature, the shorter the reliability life.

The TO-3 package is great for heat. You have a good size die you have to remove the heat from the back of and conduct it to the heat sink.

I wonder what the state of SiC and GaN devices over silicon in audio power stages is today?

 

[Bird_of_Hermes]

FWIW I don't see the "doubling down" type spec, altho it is rated for 2 ohm. I have used mine at 2 ohm for subs in any case without issue. I am not pushing continuously high power output, rather typical home needs.

I was referring to this plot:

 

[tktran303]

What’s the background noise at a typical performance venue?
50dB-70dB. Probably 20-30dB more than a quiet home/studio listening room/studio/theatre

So a SINAD of 20-30 dB below home hi-if; at ~70dB is just fine.

Crown- Competently engineered and fully fit for purpose.


The show must go on.

Thanks to @amirm for characterising this.

Where do you typically use these type of professional amplifiers for custom installs?
High end theatres eg. 30-300 persons?

PS.
Class D can scale all the way up to x kW and all the way down to 1ohm too.

Just ask Lab Gruppen and Powersoft etc.

 

[Doodski]

Edited.

 

[phoenixsong]

I think the day isn't far that someone will draw up a fan fic of Amir stress testing audio gear

 

[Sokel]

The Apollon is €6000 a pair. US$6700.

The Crown is US$1300, 1/5th the cost.

Get one or a couple of these then,measurements are hundreds of times nicer and power is there too
(they will go up to 5KW at sometime as they have promised)

https://en.rougeaudiodesign.com/product-page/studio-n-11

Edit:Specs by Rouge is all over the place,better see them in the original PDF

 

[Rja4000]

This amp is maybe near lethal or could be lethal with this kind of DC voltage. Wow!

You'd better use Speakon connectors, indeed.

 

[jhaider]

Not too surprised, except by the fan noise. In law school I used XTi2000, the previous generation and next step down in power, to drive my desktop/nearfield subwoofer. It worked very well and the fan rarely kicked on. I wouldn’t use it with mains speakers. Too noisy.

 

[DanielT]

Thanks for the test Amir. Incredible amount of power. You say "locked up in a cabinet". But not too small a cabinet without vetilation. It might get too hot for the amplifier in that case. Or what do you think?

Edit:
Speaking of PA amps used for home hifi. Replacing existing fans with silent Noctua fans may be a solution? If it works technically and if such silent fans can pump enough air.

 

[DanielT]

How audible would the noise and distortion be if this is used for consumer subwoofer duty? At what frequency do we start to notice noise and distortion?

The higher the frequency, the more sensitive we become. When does noise and distortion become audible with subwoofer duty? Check out this study below.
Attached images are from that study. It takes a lot of distortion in the subwoofer case:
(around 60% distortion)

How Much Distortion Can We Hear With Music?

How much distortion can we hear with music? An experimental study at Axiom.

www.axiomaudio.com

For those who want distortion in % instead of dB can use this calculator:

THD to dB - convert percent % to decibels dB percentage voltage % vs per cent converter THD+N total harmonic distortions calculation signal distortion factor attenuation in dB to distortion factor k in percent decibel damping - sengpielaudio Sengpiel

Calculate THD and distortions decibels dB to percentage % per cent percent voltage % vs converter and dB signal distortion THD+N total harmonic distortions factor attenuation damping - Eberhard Sengpiel sengpielaudio

www.sengpielaudio.com

 

[Rja4000]

Looks perfect to push a pair of subwoofers (or the 2 drivers of a directional subwoofer) to high level: tons of power, and the sub passive filter will probably remove enough of the noise.
Quite good power for 1200€.

0.05% THD+N is a quite common figure for pro hardware, BTW.

@amirm
No longer power consumption measurements ?