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Luke's basic amplifier tests


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Hey I resemble that remark!  

The output power of a K20 vs an X4 K20:  145 V RMS for less than a second at 2.05 ohms both channels driven Then it limits to 58 V then it goes down to 52.  This means 10.5 kw per channel for

EDIT: The testing methodology was updated to use a non-reactive load (water heater elements). I purchased 10 of these (Camco 6000w 240v low watt density): https://www.amazon.com/Camco-Screw--Foldb

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This is custom amp that Dustin bought off Craigslist.  I don't remember the cost, but it may have even been free!

 

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pcQ6X5Z.jpg

 

 

 

Dustin took it apart and it appears to be two plate amps put into a single enclosure.  The front of the box has crossover and gain controls for each channel, and the back has phase and an RCA input for each channel.  Each side has a very large aluminum heat sink.

 

 

 

VH1eY9Q.png

 

 

 

Under 20hz the amp has pretty severe roll-off on its inputs.  From 20hz to 10hz, and I had to increase the main volume by almost 20db!  At 5hz, even by just 30Vpp of output on the amp, I was at +10 on my preamp and output clipping was starting on the RCA output of the preamp.  The 5hz test was aborted for that reason.  

 

I didn't test the output with both channels driven simultaneously, but both channels driven independently had exactly the same output down to the single volt.  

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Luke, wanted to thank you for this thread.

 

As a result of your testing I bought a secondhand XLS 2000 to drive my Ultimax 18 in a 4 cubic foot flatpack (which I bought after extensive research on this site and looking at the drivers available in my price range).

 

First one is done.

 

Springtime I will buy the second kit and another XLS2000 to drive it, and will have both Crowns on a dedicated 20amp circuit :).

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Luke, wanted to thank you for this thread.

 

As a result of your testing I bought a secondhand XLS 2000 to drive my Ultimax 18 in a 4 cubic foot flatpack (which I bought after extensive research on this site and looking at the drivers available in my price range).

 

First one is done.

 

Springtime I will buy the second kit and another XLS2000 to drive it, and will have both Crowns on a dedicated 20amp circuit :).

 

Awesome!  I'm glad some of these tests were useful.

 

There's a lot of debate about how or even if these tests translate to real world use, but regardless of that one of my main goals was to test all the amps under the same conditions for comparisons sake. 

 

Before I tested the Crest CC amps I knew their 10hz and below performance was sub-par based on experience with sealed subs and real content.  This amp testing confirmed my findings. 

 

There are many other examples of this but bottom line I've found how the amps perform during this testing to correlate very nicely to real world use. 

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Awesome!  I'm glad some of these tests were useful.

 

There's a lot of debate about how or even if these tests translate to real world use, but regardless of that one of my main goals was to test all the amps under the same conditions for comparisons sake. 

 

Before I tested the Crest CC amps I knew their 10hz and below performance was sub-par based on experience with sealed subs and real content.  This amp testing confirmed my findings. 

 

There are many other examples of this but bottom line I've found how the amps perform during this testing to correlate very nicely to real world use. 

 

Yes, my concern was the sub 20hz Crown debate which you put to rest.

 

Once I get things settled a bit my goal is to purchase a Balanced MiniDSP and play around with a low shelf filter to bring up the bottom end, so I needed to make sure the amp had "somewhat adequate" power below 20hz to accomplish my goal.

 

With a single sealed 18 I get tons of bass, still not enough for my personally, but the point of this is that I want to try my best to even out the SPL of the bass given the Equal Loudness curve and I think the shelf filter will help with that a bit.

 

When I add it, I will also evaluate just how much if any of the sub 10hz stuff I can actually feel with my large room and potentially then add a highpass to ensure I dont clip the amp with that content, given how much the wattage drops below that point, and by doing so potentially gain some ability to crank it above 10hz more.

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NU4-6000 - Stereo - 4ohm (essentially a iNuke 3000)

 

NU4-6000%20-%20Stereo%204ohm_zpsmn4e8fri

 

 

Summary of the 12 second 20hz sine wave test:  

 

4ohm one channel driven:

 

122Vpp / 465w RMS for 12s

 

DS1Z_QuickPrint6_zpsqwmstkwy.png

 

 

 

 

4ohm two channels driven:

 

115Vpp / 413w RMS for 12s

 

DS1Z_QuickPrint12_zpszutd9k5e.png

 

I know this is old but did you happen to test this 4 x 4 Ohms (all four channels driven, not just two)?

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I was asked to test this over 2 months ago but I've been a huge slacker:

 

http://www.prosoundweb.com/topics/sound_reinforcement/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/

 

The basic theory is that if an amp is driven in stereo and both channels are producing the exact same signal, both channels are also drawing current from the power supply at the exact same time/interval.  The author of the article claims that if you parallel the inputs but flip the polarity on the input of one of the channels, causing the sine waves from each channel to be exact opposites, the channels are now "taking turns" drawing current from the power supply.  

 

For these tests I used a CC4000, wired my test rig for 3.4ohm per channel, and used a 30hz sine wave for a duration of 2 seconds.  I pushed the amp as far as it could go while still producing a clean sine wave.    

 

For test #1, I used an XLR y-splitter cable to parallel the same signal to the inputs and the amp was in stereo mode.  

 

For test #2, I put the amp in bridged mode and didn't make any changes to any cabling.  According to the article, all this switch does is reverse the polarity going to the B channel of the amp.

 

 

Results:

 

Capture_zpstdxoniqp.png

 

 

Test #1:

 

DS1Z_QuickPrint3_zpsm9um0dtq.png

 

 

Test #2:

 

DS1Z_QuickPrint4_zpsvlpuz4zr.png

 

 

 

 

Really no difference at all, certainly not the 5-15% increase claimed in the article.  In fact, I think test #2 has slightly more distortion in the wave form when pushed to the same 190Vpp.

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I was asked to test this over 2 months ago but I've been a huge slacker:

 

http://www.prosoundweb.com/topics/sound_reinforcement/fighting_for_power_a_way_for_amplifiers_to_increase_actual_power_delivered_/

 

The basic theory is that if an amp is driven in stereo and both channels are producing the exact same signal, both channels are also drawing current from the power supply at the exact same time/interval.  The author of the article claims that if you parallel the inputs but flip the polarity on the input of one of the channels, causing the sine waves from each channel to be exact opposites, the channels are now "taking turns" drawing current from the power supply.  

 

For these tests I used a CC4000, wired my test rig for 3.4ohm per channel, and used a 30hz sine wave for a duration of 2 seconds.  I pushed the amp as far as it could go while still producing a clean sine wave.    

 

For test #1, I used an XLR y-splitter cable to parallel the same signal to the inputs and the amp was in stereo mode.  

 

For test #2, I put the amp in bridged mode and didn't make any changes to any cabling.  According to the article, all this switch does is reverse the polarity going to the B channel of the amp.

 

 

Results:

 

Capture_zpstdxoniqp.png

 

 

Test #1:

 

DS1Z_QuickPrint3_zpsm9um0dtq.png

 

 

Test #2:

 

DS1Z_QuickPrint4_zpsvlpuz4zr.png

 

 

 

 

Really no difference at all, certainly not the 5-15% increase claimed in the article.  In fact, I think test #2 has slightly more distortion in the wave form when pushed to the same 190Vpp.

 

I read that article many years ago, and in some cases, it can be applicable. Keep in mind that you are also driving essentially a dummy resistor load, and the results may be different driving a reactive load, where back EMF is reflected on the power supply.

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