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Measuring Amplifiers - Page 9

post #241 of 1917
Any updates?
Would love to see how the crown k2 measures up!
post #242 of 1917
Thread Starter 
My "pahtner in crime" ssabripo said he would bring one of his over yesterday, but he ended up having to take of his children so he never made it. He might be able to get away and bring it over today. As soon as I get it, I will start measuring. I am very curious to put it on the bench.
post #243 of 1917
Quote:
Originally Posted by chasw98 View Post

My "pahtner in crime" ssabripo said he would bring one of his over yesterday, but he ended up having to take of his children so he never made it. He might be able to get away and bring it over today. As soon as I get it, I will start measuring. I am very curious to put it on the bench.

I know....sorry guys, kids/family/business is freaking killing me!

I;m gonna see if I can drop it off tonite or something....i promise at some point, it will get there.
post #244 of 1917
Hey Chasw98! Maybe you should make some sort of an summary where to put all the tested amplifiers. Just to put all the data in the same place, so it's easy to find. For example in the very firs post in this thread. It's getting hard to surfing throught this thread to find all the specific amps and even more harder in the future. Just an thought.
post #245 of 1917
+1 on testing the K2. I have a K2 running my subs. I have four Eminence Sigma 18As in a pair of horn loaded cabinets. (Two 18s in each cabinet, running 4 ohms in each cab) You can see them in my blog. They work great.
post #246 of 1917
You just can't off handedly mention subs in concrete without giving AALLLL the details!!! Come on, your blog ain't nearly enough . . . . . more info, more pix . . . . please?
post #247 of 1917
Quote:
Originally Posted by LINEARX View Post

You just can't off handedly mention subs in concrete without giving AALLLL the details!!! Come on, your blog ain't nearly enough . . . . . more info, more pix . . . . please?

Thanks, there is some info in a thread I started a couple weeks ago. Look here... http://www.avsforum.com/avs-vb/showthread.php?t=896248

I would be happy to answer any questions and especially to listen to your thoughts about it. I am quite sure they could be improved. I haven't built very many speakers at all and I am new to real speaker testing procedures. These could be much better I am sure so any input would be great.
post #248 of 1917
How were the concrete enclosures designed and built? Any special additives in the concrete? Has the concrete been treated to be airtight? Is there an airtight membrane applied to the inside of the enclosure? Obviously the concrete enclosures weren't designed to be moved.
I'm wondering if there's a way to design a light weight concrete sealed box of about 7 cubic feet that can still be moved.
post #249 of 1917
Quote:
Originally Posted by LINEARX View Post

How were the concrete enclosures designed and built? Any special additives in the concrete? Has the concrete been treated to be airtight? Is there an airtight membrane applied to the inside of the enclosure? Obviously the concrete enclosures weren't designed to be moved.
I'm wondering if there's a way to design a light weight concrete sealed box of about 7 cubic feet that can still be moved.

Linearx,

Look at this page for details on the early construction of the cabinets. http://gdsamps.wordpress.com/about/
The concrete was not treated. It isn't anything special other than thick. The walls on each side are 6" thick. The floor is over 10" and the back wall is 8" thick. The cap over the top is also 6" thick. It isn't going anywhere. The concrete doesn't seem to be porous to me, but I am not an expert on concrete either. I could paint the concrete to seal it off if I had to but I don't think that will be necessary.

Concrete and light weight don't go together. Besides, the mass is one of the benefits of using concrete in the first place.

So that we don't dilute this amplifier thread, lets take this over to my other thread that I started to discuss my speakers and theatre room. http://www.avsforum.com/avs-vb/showthread.php?t=896248

Thanks,
post #250 of 1917
Thread Starter 
Quote:
Originally Posted by gigbyt View Post

Any updates?
Would love to see how the crown k2 measures up!

Yes, there are! I picked up the Crown K2 amplifier on Sunday. I started testing it tonight Monday, September 17th, 2007. I was able to get results for 8 ohm and 4 ohm measurements but I blew the 20 amp fuse in the unit while I was testing for 2 ohms. So we will have to wait until I can pick up a 20 amp fuse tomorrow to continue with 2 ohm testing.

Chuck
post #251 of 1917
A sneak peak of the 4 ohm and 8 ohm results wouldn't hurt while waiting...

Edit: Never mind. Thanks!
post #252 of 1917
Thread Starter 
Finally, here it is. The long promised Crown K2 amplifier measurement and test. This unit does not have a fan. This unit gets very, very hot when testing. Frequency response is +-0.25db from 20 Hz to 20 Khz. There is an 8Hz double integrated 3rd order Butterworth high-pass filter and a 30 Khz 7th order Gaussian low-pass filter. So there!

Power output per channel at 1 Khz with both channels driven to 0.1% or less True THD : 1,250W @ 2 ohms; 800W @ 4 ohms; 500W @ 8 ohms; Bridged Mono 2,500W @ 4 ohms.
Signal to Noise (A-weighted): >100 db below rated power.

These specifications come verbatim directly from the owners manual. Here is what this model looks like.







On to some testing...........
post #253 of 1917
Thread Starter 
Here are the results for 8 ohm measurements. The unit would never reach full rated power with both channels driven as specified in the manual, (I don't know why, possibly age & use), so I went ahead and set the 1 Khz measurement to the rated .1% THD and then checked 20 Hz and 20 Khz from that point without changing any levels at all. You will notice that frequency response almost meets specs except in the 20 Khz region.



This is what the output waveform looked like at full rated power.

post #254 of 1917
Thread Starter 
This is what the waveform looked like at .1% distortion.



Notice the oscillation just starting to form in the peaks and troughs of the distortion component waveform on the bottom trace.
post #255 of 1917
Thread Starter 
Here are the results of 4 ohm testing.



Even though this unit does not meet power output specifications, it has been the most well behaved amplifier I have tested recently. It does not shut down, it gets very hot but makes no noise. It survives my old school 'plug in a load and let it cook' testing quite well. I have always been very curious about the '8 Hz high-pass filter' that Crown claims to put in this unit. So I measured it at the bottom end. I had to pull out my Wavetek sweep generator that goes down to .1 Hz and guess what? At 4 Hz the amp is 18 db down, 6 Hz 6.6 db down, and at 8 Hz 2 db down. Not a bad filter.
post #256 of 1917
Aahhhhh...sweet! Not too shaby. Im actually surprised by the low-end roll-off. Was thinking it would be much worse with the filter @8hz. Almost nothing at the upper single digits. Very cool! Not surprised at the power output though... Nice distortion levels too. Still stickin' with my 2500. Ah ha!

Very curious about the 2ohm tests....

Ill be patient.

Nice work, Chuck!
post #257 of 1917
Yes!!!!!!!!!

Well, this confirms what I've been experiencing all along!! pure, clean, QUIET, power. Since my subwoofer design was amp limited at 800W, I'm good to go.

Well done chuck...thank you.

Now leave that puppy alone, and no more testing on it!! Don't want momma to cut my other nutsack if she finds out I blew the amp and need money for another one!
post #258 of 1917
Chuck's test @ 20hz, 0.075% THD @ 120VAC? = 633w
Bink's test @ 20hz, 1% THD @117VAC = 724w

Seems to correlate, higher distortion test yield more power.

***

Bink's test @ 20hz, 1% THD @96VAC = 446w
Chuck's test @ 20hz, 1% THD @ 96VAC = ???

??? = if this test was done, it probably correlates too.

Some people don't value Binks test I guess in spite that it
has been correlated to Chuck's test. lol
https://home.pacbell.net/lordpk/bink/bink.jpg
post #259 of 1917
Thread Starter 
Quote:
Originally Posted by ssabripo View Post

[size="7"]Now leave that puppy alone, and no more testing on it!!

Ya big baby. I only blew one other fuse tonight testing 2 ohm and 4 ohm bridged mono. It still works!

Quote:
Originally Posted by thylantr View Post

Some people don't value Binks test I guess in spite that it
has been correlated to Chuck's test.

Actually, Binks test is one of the very few that have all the apples equal when you want to compare horsepower. Even the FTC does not require any standards for pro amp measuring at all.
post #260 of 1917
Thread Starter 
Here are the measurements for 2 ohms. I did not test any frequency other than 1,000 hertz because of overheating issues with this much power. Plus, I don't own the amp



As you can see it puts out some power. Not its rated 1,250 watts but a good showing none the less.

Here is the 4 ohm bridged mono measurement. Once again, only at 1 Khz.

post #261 of 1917
Thread Starter 
Here is an interesting comparison. One channel of Crown K2 and one channel of Behringer EP2500. They are so close that specs are not the determining factor.



I like the circuit breaker on the EP2500. I like having no fan on the K2. I like the removable power cord on the EP2500. I like the warranty and reputation on the K2. It really seems like a coin toss.
post #262 of 1917
It looks like the K2 likes lower loads. From ~640W (4ohm) to ~1000W (2ohm) is a good ratio. Does anyone wonder how it would fare at 1 ohm load?
post #263 of 1917
Quote:
Originally Posted by chasw98 View Post

Here are the results of 4 ohm testing.



Even though this unit does not meet power output specifications, it has been the most well behaved amplifier I have tested recently. It does not shut down, it gets very hot but makes no noise. It survives my old school 'plug in a load and let it cook' testing quite well. I have always been very curious about the '8 Hz high-pass filter' that Crown claims to put in this unit. So I measured it at the bottom end. I had to pull out my Wavetek sweep generator that goes down to .1 Hz and guess what? At 4 Hz the amp is 18 db down, 6 Hz 6.6 db down, and at 8 Hz 2 db down. Not a bad filter.

EP-2500 @ 4 Ohms:

post #264 of 1917
Quote:
Originally Posted by chasw98 View Post

Here is an interesting comparison. One channel of Crown K2 and one channel of Behringer EP2500. They are so close that specs are not the determining factor.



I like the circuit breaker on the EP2500. I like having no fan on the K2. I like the removable power cord on the EP2500. I like the warranty and reputation on the K2. It really seems like a coin toss.

Daaaammmmmn right! Thats pretty damn close with a big markup on the K2. Look at the S/N ratio too .... very interesting.

Its only $15 to make the 2500 damn near silent and I have a very quiet house and my amp is in front if the tv... not bad for <$400.

Do you think Sherv will let you go wild on this one and try out the low freqs at 2ohm/4ohm bridged, Chuck?
post #265 of 1917
Quote:
Originally Posted by Richard Mayer View Post

It looks like the K2 likes lower loads. From ~640W (4ohm) to ~1000W (2ohm) is a good ratio. Does anyone wonder how it would fare at 1 ohm load?

Yup ... that 1000 Hz signal will sound great on a sub, too ...

Seriously, too bad Chuck could not do the 20 Hz test @ 2 ohms ... but it appears the K2 is not the amp for my Dual SDX sub, either.
post #266 of 1917
Thread Starter 
Here is the K2 2 ohm at 20 Hz.



For you, Craig!

PS, the amp is cooling down right now.
post #267 of 1917
Man, that cheap Behringer EP2500 is looking good!
post #268 of 1917
Quote:
Originally Posted by mojomike View Post

Man, that cheap Behringer EP2500 is looking good!

Yes, its reputation as one of the best bargains in amplification stands strong.

Especially when you can have multiples of them for the cost of one of the "better" amps.
post #269 of 1917
Quote:
Originally Posted by chasw98 View Post

Here is the K2 2 ohm at 20 Hz.



For you, Craig!

PS, the amp is cooling down right now.

Thanks, Chuck. Much appreciated ... As pointed out by others, the Behringer is looking pretty good ... I should have stuck with the first plan, and built 4 single driver boxes for the SDX-15's.

The right amp to drive 2 to their limit is going to cost a lot of $$$$.
post #270 of 1917
Hey Chuck,

Do you happen to have access to a CE400?

If so, I am not sure about others, but I would love to see that baby tested.
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