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Review and Measurements of Crown XLS 1502 Amp

sac

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If that's the case, something is wrong. Take it to be repaired.
lol, now how will this go "whats wrong with the amp sir" ....." a guy on the internet says my fan ought to be absolutely silent, but I can hear it metres away"..........you gotta be kidding.
 

Neddy

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My XLS is 8 ft from my chair, and I only know the fan is running b/c I can (sometimes) see it start to spin up through the front panel grill!
It's also sitting on top of almost all my other amps & processors....so it does get warmish...still can't hear it, but I assume it's a variable speed fan controlled by a temp sensor circuit, so could have a 'hurricane' mode if really needed.
I wouldn't put one of those on top of a high powered receiver, more out of concern for the receiver than the amp, though.
 
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I have two XLS 2502's on top of five Behringer amps in a closed rack that gets over 125ºf and when I open the rack door I still can't hear the fans. Before the 2502's I had a pair of 1002's in the same spot. I've also used the XLS amps a lot in actual pro environments and have yet to hear the fans.

sac, something is abnormal about your setup, or amps.
 

sac

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"I wouldn't put one of those on top of a high powered receiver, more out of concern for the receiver than the amp, though."

Neither would I, did I mention it was a few centimetres away? Ive since added 4 cm spacers which seems to keep the xls cool enough. to stop the fans triggering Not all of us have unlimited real estate to lay these things out vertically independent from each other and due to its size, the receiver has to go at the bottom of my stack. And yes its a high power receiver, but only providing line level signals , as I mentioned just the idle heat( 35 C on top panel) that rises that is enough to trigger the xls. Infrared measurements of the front panel of the xls, where it seems to get hottest, have the fans triggering in the region of 40 C, what temp on the critical parts inside, no idea.

My equipment is in an open rack, so any noise is not contained by walls of a cabinet etc.

Just putting this out there for folks, its highly unlikely Ive got the only xls that was supplied without the "silent fan", my hearing also is limited now to below 12 kHz , so not superhuman. The noise doesn't concern me enough to think there is something wrong with the unit, just letting people know that claims of it being silent are fanciful and perhaps more indicative of purchaser rose coloured glasses phenomenon.
 
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Neddy

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Sorry, I meant that literally (to myself), not as a put-down to you - I had a high power receiver with a small amp stacked 2" on pads above it, also running as a preamp only, and it still died of heat exhaustion...should have worded that better.

However, my hearing is a bit better than you say of yours (15khz), and the XLS is less than a foot away from the 'front' wall, also open backed, and I cannot hear it at all; but I can hear the fan in the dBX Venu 360, which is tiny, and whines like heck....so not rose colored glasses.
Before I purchased it, I called Crown tech support, and he specifically recommended this over their other Pro amps, partly b/c the fan in this was designed to be quiet enough for home use.
Wonder if the xls fan could be replaced with a Noctua equivalent - I use those elsewhere when I want super-quiet air movement.
I've also had good luck 'quieting' noisy fans simply by blowing/sucking the dust off them....
 

BYRTT

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1) ...I'm using mine only currently to biamp the low end on my speakers, so not going to hear any real effects from higher end harmonic distortion or noise issues...

2) ...I like the ability to able to use the band/crossovers and only send the signal to the drivers that they need, whether this enhances the life of the actual speaker crossovers, don't know.
Its not my business what users like of settings but hope you aware doing 2) in combination with 1) then new EQ filter will cascade to speakers original XO slope and change how intended XO summing region works, so in principle say speakers XO region was optionally voiced ab fabric then any new EQ filtering needs to be global else that optionally engineering work on XO region is detuned.
 

sac

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I
Its not my business what users like of settings but hope you aware doing 2) in combination with 1) then new EQ filter will cascade to speakers original XO slope and change how intended XO summing region works, so in principle say speakers XO region was optionally voiced ab fabric then any new EQ filtering needs to be global else that optionally engineering work on XO region is detuned.
Yes, I sort of understand what you are saying, but if I overlap the crossovers by at least half an octave will it matter?, given that the xls lowpass/high pass rolls off per octave as well? In my case the speaker crossover is at 500 Hz in my two way system, if I set the filter on the xls to 750 Hz to power the low end there will be plenty of overlap there? The top end at present is getting the full range sent to the tweeter..
 

BYRTT

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Yes, I sort of understand what you are saying, but if I overlap the crossovers by at least half an octave will it matter?, given that the xls lowpass/high pass rolls off per octave as well? In my case the speaker crossover is at 500 Hz in my two way system, if I set the filter on the xls to 750 Hz to power the low end there will be plenty of overlap there? The top end at present is getting the full range sent to the tweeter..
: ) as said its not my business if you like 750Hz as what you call plenty of overlap, what i know is if as said XO region was optionally voiced ab fabric that optionally engineering work for XO region will now be assymetric detuned relative to mid/tweeter bandpass and example of visual consequence is plottet below.

Red trace example show a often used 500Hz LR 4th order low pass, looking up manual for XLS amp it say filter is another 4th order LR so blue trace show what you get cascade two LR 4th order filters at 500Hz and 750Hz:
1000.png


In amplitude domain say system was 2 way 4th LR at 500Hz that summed flat on some unknown design axis as blue trace example below then the cascaded 750Hz filter will add the pink trace amplitude difference on same design axis:
1001.png


In time domain on some unknown design axis say filter is textbook for a LR 4th order filter at 500Hz seen in left wavelet graph, then right wavelet show the difference cascade 750Hz filter (dotted line can be read as a group delay graph).
1004.png
 

sac

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: ) as said its not my business if you like 750Hz as what you call plenty of overlap, what i know is if as said XO region was optionally voiced ab fabric that optionally engineering work for XO region will now be assymetric detuned relative to mid/tweeter bandpass and example of visual consequence is plottet below.

Red trace example show a often used 500Hz LR 4th order low pass, looking up manual for XLS amp it say filter is another 4th order LR so blue trace show what you get cascade two LR 4th order filters at 500Hz and 750Hz:
View attachment 26083

In amplitude domain say system was 2 way 4th LR at 500Hz that summed flat on some unknown design axis as blue trace example below then the cascaded 750Hz filter will add the pink trace amplitude difference on same design axis:
View attachment 26084

In time domain on some unknown design axis say filter is textbook for a LR 4th order filter at 500Hz seen in left wavelet graph, then right wavelet show the difference cascade 750Hz filter (dotted line can be read as a group delay graph).
View attachment 26085
Thankyou for taking the trouble to reply and improve my understanding of this issue, yet I don't understand most of what you have posted:

1. XO region was optionally voiced ab fabric ?

2. Bottom graphs, what are they and what do they show?

3. Are you claiming my system would have a 5 dB dip in response at 500 Hz with the xls filter set at 750 Hz?

4. What frequency would the xls setting need to be above 500 Hz to avoid this? or is it impossible.

I do run audyssey on my system, and it returns the same equalisation settings regardless of whether the xls filter is used or not, is that telling me the overlap is enough?
 

BYRTT

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Thankyou for taking the trouble to reply and improve my understanding of this issue, yet I don't understand most of what you have posted:...
Welcome, try understand in examples i use a textbook perfect figure of a 20Hz-20kHz audio domain with a 4th order LR XO point at 500Hz and maybe your speaker ab fabric is not setup to same textbook perfect figure for many reasons, but the value of the difference/distortion graphs that show up as consequence of cascade single filter to only the lowest frq bandpass (assymetric) should be same numbers for actual speaker whatever its XO region looks like in reality.

... 1. XO region was optionally voiced ab fabric ? ...
One can't really know how state of the target/quality/precision was of a probably mass produced speaker build before shipped to customers.

... 2. Bottom graphs, what are they and what do they show? ...
Its time domain graphed as a wavelet in free REW, for info a perfect graph of a 20Hz-20kHz audio band in electric domain will be nearly perfect symetric before and after time zero line but for speaker systems use of filters to sum varius band passes will add phase differences/distortion.

... 3. Are you claiming my system would have a 5 dB dip in response at 500 Hz with the xls filter set at 750 Hz? ...
Yes that's what simulation suggest.

... 4. What frequency would the xls setting need to be above 500 Hz to avoid this? or is it impossible. ...
Sorry as close as possible to same bandwidth as for mid/tweeter bandpass, setting a new filter one should then measure system and and take care implement right filter slopes to the two band passes so they will sum as perfect as possible in amplitude and time domain on acoustic design axis.

... I do run audyssey on my system, and it returns the same equalisation settings regardless of whether the xls filter is used or not, is that telling me the overlap is enough?
Will be guessing here but in consequence of that in real world rooms its very difficult get any meaning full precise acoustic numbers say 500Hz and below, that could be the answer here, that said i have no clue how Audyssey works.
 

EX511

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What would you recommend to power my KEF Q750's using a Denon avr-x3400h or avr-x4400h as a preamp?

All the reviews i've read seem to be powering them with amps in the 250w @ 8 ohms per channel range to get the most out of the Q750's.

I was thinking about going with a 2002 unless you guy's think the 1502 would be plenty

thank you
 
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Hi, new here but I have read the forums quite a bit.
I was disappointed to read about the ADC and DAC conversion in the amps, I have a 1502 and a 2002
I monitor in my studio and have a nice new DAC arriving, so I really would like to know I will avoid this.
If I don't use the DSP for filters for low and highpass, will I bypass the ADC? or will I get it regardless, and if so what chips does it run through?
Thanks for info!
 
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Hi, nice review. Is it possible to heave your audiophile measurements not with 5W but with 0,3 / 0,5 / 1 Watt ? 5 Watt is already very loud with most speakers and above typical average listening volume.
 

gene_stl

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The subject of Crown professional amps is a very big one. I have been delving into it deeply. Right now I have a stack of
XLS 602 amps from the early 2000. These have a huge toroidal linear supply and fully complementary output stages. They have dual fans that come on with the power switch and are too noisy to use as is. My initial thought was to replace the inexpensive fans with some quiet Pabst fans from chermany (this would be about $50 per amplifier two fans at $24 each) and then control them with a thermostatic control like this one.

https://www.amazon.com/Temperature-...tat-Waterproof/dp/B07H2X4NNR/ref=cts_ap_1_vtp
there are many electronic fan thermostats available from AlieExpress and Banggood too. Some based on an Intel chipset designed for exactly this purpose. Apparently gamers don't want their gaming concentration disturbed by fans either.
https://www.aliexpress.com/item/32909074552.html?spm=2114.search0204.3.84.51d64e00cwOQM9&ws_ab_test=searchweb0_0,searchweb201602_1_10065_10130_10068_10547_319_10546_317_10548_10545_10696_10084_453_454_10083_10618_10307_537_536_10059_10884_10887_321_322_10103,searchweb201603_52,ppcSwitch_0&algo_expid=a84fdf3c-d1d8-4424-b9aa-f3b4d0940541-15&algo_pvid=a84fdf3c-d1d8-4424-b9aa-f3b4d0940541

https://www.aliexpress.com/item/329...lgo_pvid=a84fdf3c-d1d8-4424-b9aa-f3b4d0940541

There were two or three iterations of these amps and they bear no resemblance to the current XLS amps which are SMPS and Class D or I or whatever they call it. (all called Drive Core now , I think). I am not sure why they "recycled" the model numbers. The build quality is impressive even though they were built in China. I do have one that came to me with one spewed filter cap.

Then I discovered that a local guy has a pallet of CTS 600 and 1200 series amps. These have switching power supplies but are class AB (but quasi complementary like the original crowns not fully complementary. It is doubtful that there would be any audible effects of this in this day and age).
The CTS series are controllable via their system architect. Unlike many audiophiles I would not want to bypass this section. The DSP is an Analog Devices Sharc which is used in many very high end pieces (like Meridian Audio products among many others) I realised that with a stack of these I don't need a crossover network. I will probably be using a bunch of them. The CTS series fans are totally thermostatically controlled from the factory.

The CTS are about ten years old. The newer stuff does even more tricks. The CTS have CobraNet which Crown tech support said was a PIA. The newer ones allow audio to be transported via BLU8 net. The new ones also have their DriveCore chip which they developed with TI and is not available anywhere else. It does a lot of very interesting tricks. (So do all the DSP equipped Crowns like for example reducing power if necessary to keep the output devices in their Safe Operating Areas on a real time, essentially cycle by cycle basis , by being able to calculate way faster than audio frequencies even ultrasonics)

The DSP has very programmable limiting too both on the amp input and output so my beryllium tweeters and midranges will never experience a clip.
And 300 watts per channel will also ensure that only sine waves will reach the drivers. I don't remember much clipping with the 30 wpc class As that will be replaced with these Crowns ,either. I do listen to mainly classical music.
 
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amirm

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Hi, nice review. Is it possible to heave your audiophile measurements not with 5W but with 0,3 / 0,5 / 1 Watt ? 5 Watt is already very loud with most speakers and above typical average listening volume.
You have that in this measurement:



All amplifiers will be noise bound below a few watts so we won't be measuring distortion there.
 

gene_stl

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Re the above discussion of fans.

I have started working with the CTS 1200 and multiple CTS 600. While dusting them and inspecting them I have plugged them in and of course the fully automated fans don't so much as budge.


BUT! there is a tiny nasssty little (probably 20 mm square) fan in the input module plug in that starts right up with the power and is very noisy. I may have to rig up some kind of piping and cover perhaps leading to a larger and slower fan to get rid of that noise. Lots of High Frequency like a little siren. Small circular perforations for vent holes. What were they thinking? The fan is in the Pip USB3 CN module. I think the plain analog inputs may not have a fan. But they don't have the DSP either. The DSP module has lots of chips on it.
 
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I read a lot about bad performance for Subwoofer in German Facebook groups (for all class d/h) . Is it possible to measure continuous power and distortion at 40 to 80 Hz?
 

Jonas_h

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@amirm, this is a very interesting review - thanks!

Did you ever do something like this with a Crown Class-I amplifier? Or have you ever compared a Class-I to other amps? I own the M2s driven by BSS and MA5000i as spec'ed by Crown and I'm thinking what an amp-upgrade could give me.
 

Skrattar

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I was thinking, could it be possible to solder in the 4 missing power transistors to get a 1502 up to 2502?
 

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