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Crown XLS2502 Stereo Amplifier Review

amirm

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#1
This is a review and detailed measurements of the Crown XLS2502 DriveCore (switching) 2-channel amplifier. It is on kind loan from a member. The XLS 2502 cost US $645 including free shipping from Amazon. It has DSP functionality which I did not test. And is specified to drive 2 ohm load.

From the outside, the XLS2502 is built like a tank:

Crown XLS2502 Drivecore Stereo Pro Amplifier Audio Review.jpg

It is very light of course due to switching topology for the amplifier and power supply. But also very sturdy with plenty of steel to keep its shape.

The two gain controls are notched which gives them a nice feeling but the gain is not matched and is hard to get there using those notches.

Here is the back connectivity:
Crown XLS2502 Drivecore Stereo Pro Amplifier Back Panel Connectors Audio Review.jpg


There is a fan as you see but in normal testing it never came up. During stress testing, it did come on but was pretty quiet compared to what I expected. Mind you, I don't think you want it close to you if it is going to be running.

Alas, the fan was insufficient to keep the unit cool under full power. The red thermal indicators came up even though the fan was running. The amp seemed to be functioning still but to be on the safe side, I terminated my testing there. In typical home use, even for subwoofer duty, I doubt that this is a concern as you will see later as far as what wattage we are talking about.

Overall, the impression of the amplifier is positive, making you think you have something made to be run over by a car and still function reliably.

Amplifier Audio Measurements
As usual we start with our dashboard of 1 kHz tone into 4 ohm load at 5 watts:
Crown XLS2502 Drivecore Stereo Pro Amplifier Audio Measurements.png


I set the gain to 29 dB for consistency. I also tested it at 19 dB gain and it only made 1 to 2 dB improvement. The reason is that SINAD (signal relative to noise+distortion) is dominated by harmonic distortion. Here, those harmonics are very high order which perceptually is not very good as they are not masked as easily. Anyway, with a SINAD of 71 dB, we have below average performance:

Best Pro Amplifier Review.png


The XLS1502 did a bit better in this regard, garnering a SINAD of 77 dB.

Frequency response shows the same sharp cut off:
Crown XLS2502 Drivecore Stereo Pro Amplifier Frequency Response Audio Measurements.png


I don't know if this can be changed using DSP programming or not.

Above is with resistive load. Switching to a simulation of a 2-way speaker gets us little difference:
Crown XLS2502 Drivecore Stereo Pro Amplifier Frequency Response with Simulated Speaker Audio M...png


So there is some speaker dependency but I would not lose sleep over it.

Crosstalk is OK but could be better:
Crown XLS2502 Drivecore Stereo Pro Amplifier Crosstalk Audio Measurements.png


The red line is a $30 amplifier by the way.

32-tone test signal simulating "music" gives a more hopeful picture of distortion:

Crown XLS2502 Drivecore Stereo Pro Amplifier Multitone Audio Measurements.png


The spray of harmonics is high in frequency where our hearing threshold is higher.

Signal to noise ratio is poor at 5 watts but gets better at full power:

Crown XLS2502 Drivecore Stereo Pro Amplifier SNR Audio Measurements.png


Lower gain settings may improve this a few dBs.

Amplifier Power Measurements
You don't buy this amplifier to listen at 5 watts so let's see what it can do when its wings are given enough room to fly:

Crown XLS2502 Drivecore Stereo Pro Amplifier Power into 4 Ohm Audio Measurements.png


Wow! Nearly 500 watts of power is delivered into both channels simultaneously. The good news doesn't end there. Check out these ratings when distortion is relaxed to 1%:
Crown XLS2502 Drivecore Stereo Pro Amplifier Peak and Maximum Power Audio Measurements.png


1600 watts of peak power is delivered out of standard 120 volt outlet! These thing is a powerful beast.

Noise level is decent but I wanted to make sure the high gain was not impacting it. So I reduced gain to 19 dB which required some 6 volts of input to drive to clipping:
Crown XLS2502 Drivecore Stereo Pro Amplifier Power into 4 Ohm 19 dB Audio Measurements.png


There is no difference at all.

For the rest of these tests I stayed at 19 dB gain. Here is the power output with 8 ohm:

Crown XLS2502 Drivecore Stereo Pro Amplifier Power into 8 Ohm 19 dB Audio Measurements.png


Over 300 watts at what should be inaudible distortion for most people.

Finally we get to my stress test. I played with the settings because the high frequency noise shaping would not let me perform the sweep. So I decided to change this test and set the limit to 22.4 kHz (instead of usual 90 kHz) and limit the sweep to 6 kHz. That way, the third harmonic of 6 kHz (18 kHz) is still included in the computation. No music has full power at high frequencies anyway so I don't think we need to keep measuring to 20 kHz with respect to power. Here is the output:

Crown XLS2502 Drivecore Stereo Pro Amplifier Power vs Frequency Audio Measurements.png


As noted, the red warning lights came on as the sweep was going from right to left so I terminated the test. Delivered output was about 520 watts which is still plenty but is naturally lower than 1 kHz which was in high 600s.

Conclusions
These pro amps have mastered the technique of delivering tons of power with distortion and noise kept under control. Lack of power is the #1 reason an amplifier can sound bad. Don't care how good the SINAD is at 5 watt. If you run out of power, you will hear distortion, lack of dynamics, etc. So if you need the power, it is best to get it than to have less of it. And on that front, the Crown XLS 2502 delivers tons of it, breaking all previous records for any amplifier I have tested. The price is ridiculously low for the amount of power you get as well.

Ideally, you would use more finessed amplifiers above bass frequencies and use the XLS 2502 to drive the subs. But if not, the XLS2502 can deliver good performance.

Overall, I am going to recommend the XLS 2502.

------------
As always, questions, comments, recommendations, etc. are welcome.

It is two minutes to midnight. Getting my panthers to model this late at night is costing me overtime pay at 2X their normal hourly rate. So while my time is free, theirs is not. So please donating generously using: https://www.audiosciencereview.com/forum/index.php?threads/how-to-support-audio-science-review.8150/
 

pierre

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#2
Pro amp have more expensive options: does someone know one that has better performance while keeping lots of power? From labgruppen, powersoft, the expensive crown ... I have a small labgruppen ipd 1200 that I could send from Europe if that helps.
 
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amirm

amirm

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Thread Starter #3
I don't think any of them target higher performance (distortion/noise) levels than what we are seeing. It just isn't their market. But we will see as we test more.
 
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amirm

amirm

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Thread Starter #4
Shoot. Forgot to post the FFT spectrum:
Crown XLS2502 Drivecore Stereo Pro Amplifier 1 kHz Broadband FFT Audio Measurements.png


Since there has been a lot of talk about ultrasonic power, here it is at near full power:

Crown XLS2502 Drivecore Stereo Pro Amplifier 1 kHz Broadband FFT Full Power Audio Measurements.png
 

Cahudson42

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#5
Reminds me of the amp/speaker scene in 'Back to the Future'.. Just what speakers can use, and handle, this kind of power?
 
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#6
Reminds me of the amp/speaker scene in 'Back to the Future'.. Just what speakers can use, and handle, this kind of power?
This kind!
A Crown xli3500 on each bass cabinet.
 

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milosz

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#7
Reminds me of the amp/speaker scene in 'Back to the Future'.. Just what speakers can use, and handle, this kind of power?
Big sound-reinforcement subwoofers used for big venues or outdoor concerts certainly can absorb this power- AND MORE. With the long wavelengths of bass frequencies, the speakers typically are omnidirectional, so perceived loudness will fall off as the SQUARE of the distance. Of course there's also room gain... so many factors....

And pro midbass arrays can handle some big watts, too, as well as some midrange arrays. Big venues / outdoor events need LOADS of power. And you don't want the amps even coming NEAR clipping on peaks,

With the mids and treble, the speaker arrays are typically designed to be directional and so often have distance-loudness relationships that better the inverse-square law.

Remember loudness and power have a logarithmic relationship- to produce DOUBLE the perceived loudness you need TEN TIMES THE POWER, regardless of distance.
 

RayDunzl

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audioBliss

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#9
I had higher hopes for this one. I have passive sealed subs so it would be nice with something that's flat to 5Hz at least. Looks like this one starts dropping at around 80Hz. LAB Gruppen PDX3000 looks interesting. But also measurements of the Behringer EP4000 would be interesting.
 

JohnBooty

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#10
I would recommend everybody listening to a system with high efficiency (90+ dB/watt, ideally 95+) speakers and/or a high-output amp like this, if you ever get the chance.

Once you have heard a system that achieves that, it will change the way you look at audio.

It's not about hitting massive SPL output levels. (Although that's obviously fun too, for brief periods of time)

It's about sounding "effortless" - handling every dynamic peak in your music without audible distortion. Even at moderate listening levels, this is very pleasing to the ear.

Reminds me of the amp/speaker scene in 'Back to the Future'.. Just what speakers can use, and handle, this kind of power?
A lot of affordable tower speakers are rated to handle peak output in this range. Lots of cheap Klipsch floorstanders are rated for like 100W continuous / 400W max. Floorstanders with 12" and 15" woofers can often handle 200W+ continuous.
 

kaka89

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#11
I would recommend everybody listening to a system with high efficiency (90+ dB/watt, ideally 95+) speakers and/or a high-output amp like this, if you ever get the chance.
Do you know why is that? I have the same experience but I don't know why.
Most people said 5W or 10W is enough to drive the speaker to a very high SPL.

Does the damping factor has anything to do with it? Archimago have been measuring and ranking amps by their damping factor recently.

http://archimago.blogspot.com/2019/12/measurements-emotiva-xpa-1l-gen-1-class.html
 

FrantzM

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Absolute

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#13
It looks like Crown knows how to make amplifiers, so why can't they just get rid of those nasty high-order distortions? I can't understand the "recommended" label given to such mediocrity considering that the output of an amplifier isn't a quality trait by itself.

Edit; I would also like to see a full review of products like these with fancy stuff like dsp. I reckon it's not good enough for a site such as ASR to write "I don't know if the dsp affect the performance" in a review where a major part of an amplifiers appeal will be that functionality.

If ASR won't bother to publish measurements with and without some audio-altering functions included, who will?
I think the quality of the reviews are more important than the quantity, so I would like to wish for just that little bit of extra value in cases of particular interest. Which, of course, means products that have something out of the ordinary going for them in one way or another.

This baby has heaps of power and dsp functionality for peanuts, so a special case imo. :)
 
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Willem

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#14
Plenty of power does have its sonic benefits that are probably greater than those of the last few dB lower noise or distortion. Anyway, here is an AP test of the pretty good but discontinued 2x350 watt Yamaha p3500s: https://www.homecinema-fr.com/forum...mpli-yamaha-p3500s-mise-a-jour-t30056383.html Until recently it sold for about 350 euro. I bought the less powerful 2x250 watt P2500s for my son, and it sounds absolutely fine. I would love to see how this series measures with Amir's protocol.
These have now been succeeded by a new series of class D amplifiers, and I would not mind seeing a test of those as well. Anybody in the US have one?
 

DonH56

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#15
-45 dB relative to 600 W is 18.974 mW.

Years ago, wish I could find the reference, the average-to-peak value for music was measured at 17 dB (I think for classical but am not sure). 17 dB is a factor of 50 in power, so at 1 W avg you need at least 50 W for peaks, and at 5 W average 250 W for peaks. I have read more recently about 20 dB (power factor of 100) for high dynamic range music and ~30 dB (! -- power factor of 1000) for some movies. I have not verified any of these numbers but they are found on various fora and websites.

Damping factor is a function of output (and load) impedance which is usually lower (better, higher damping factor) for high-powered amplifiers due to the additional output devices in parallel to provide sufficient SOA (safe operating area) and (sometimes) higher feedback factor. That will not provide more power, but does mean less sensitivity to loudspeaker impedance and less sensitivity to back-emf (energy kicked back to the amplifier as the drivers move) so less dynamic distortion.

My speakers, Revel Salon2's, are rated at 86.4 dB/2.83 Vrms/m (fairly low), 6-ohms nominal (though around 4 ohms for a wide range). The specs do not list a power rating but I am pretty sure they'll handle 300 - 500 W peaks in the bass.

FWIWFM - Don
 
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Matias

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#16
It looks like Crown knows how to make amplifiers, so why can't they just get rid of those nasty high-order distortions? I can't understand the "recommended" label given to such mediocrity considering that the output of an amplifier isn't a quality trait by itself.
I think the price allows for sins to be forgiven. If this amp cost 4k it would get a beheaded panther I guess. :)
 

Absolute

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I think the price allows for sins to be forgiven. If this amp cost 4k it would get a beheaded panther I guess. :)
No doubt, but why should we accept the worst kind of distortion at a level where they can be audible from a serious manufacturer?
 

Francis Vaughan

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#19
Damping factor is exactly the nominal speaker impedance divided by the impedance of the output stage divided by the feedback factor of the amp. That is it. It can be a surrogate for some design decisions made in the amplifier, but as a figure of merit on its own it is meaningless.

Conventional amplifier designs will add series resistors on each output device. These serve to provide both some linearisation of the device and when multiple devices are paralleled, they ensure current sharing. Typical value you see is 0.22 ohm, although Douglas Self tends to suggest 0.1 ohm is preferable. Given this, output impedance, and thus damping factor, is then mostly determined by the feedback factor in use, and this is going to be a mix of design decisions that will be governed by overall stability margins. How many output devices are used is an engineering tradeoff, and more is not necessarily a figure of merit, it may be a decision to use multiple cheaper devices to keep costs down.

Paring damping factor back to its external effects, it is just a measure of the output impedance of the amplifier. Given that audio amplifiers are voltage sources, all you are doing is specifying the Thevenian equivalent source - which is identical to simply adding a very small additional series resistance to the circuit. Given you already have 8 ohms in that circuit, the additional tiny resistance is essentially meaningless.
 
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