or Connect
AVS › AVS Forum › Audio › DIY Speakers and Subs › Measuring Amplifiers
New Posts  All Forums:Forum Nav:

Measuring Amplifiers - Page 59

post #1741 of 1917
Crown XLS 802D - $429 NEW Shipped
vs.
Behringer EP4000 - $335 NEW Shipped

from what i've read so far, the ep is the best bang for buck, but, i found a good deal on a new crown 802 for less than $100 more. would the crown have better performance or is the ep still better even with this smaller price gap.

i've read numerous posts about different output from the 4000 in 4ohm stereo...
some say around 500 and others say 900. since the 2500 should be similiar, the 4000 should put out roughly 650 vs the rated 800w from the crown, plus the longer warranty and reputation.

edit: i could also get a used yamaha p5000 for $400 shipped (little to no fan noise from what i've read)
post #1742 of 1917
Hey gang:

I was looking at picking up a crown xti 4000 to power a Captivator but I read from a couple years back that the xti series suffered from crippled low (20 hz) output levels...not good for a sub amp, lol.

Anyway according to crowns site (and a couple of posts here on avs) it appears the problem was resolved.

Can anyone point to new tests or assure me otherwise? I could really use the 2400 8 ohm watts for the Captivator.

Thanks!
James
post #1743 of 1917
The XTi 4000 hasn't been measured yet. I've got one driving my LMS 5400 in a sealed 6 cu ft box. It has all the low power I ever use and then some.
My conservative guess is it has about 700-1000 watts @ 20Hz.
What's good and unique about the XTi is the parametric EQ and all sorts of Pro Amp protection along with filters, sub synth, and hook-up options.
post #1744 of 1917
Quote:
Originally Posted by LINEARX View Post

The XTi 4000 hasn't been measured yet. I've got one driving my LMS 5400 in a sealed 6 cu ft box. It has all the low power I ever use and then some.
My conservative guess is it has about 700-1000 watts @ 20Hz.
What's good and unique about the XTi is the parametric EQ and all sorts of Pro Amp protection along with filters, sub synth, and hook-up options.

Well since it's rated at 2400 watts bridged into 8 ohms, I'd like to think it's hitting that number (or more) from 20hz-20khz.

Thanks for the vote of confidence though.

James
post #1745 of 1917
You have to be careful NOT to give manufacturers too much credit for total honesty regarding the performance of their products.
At the beginning of this thread "Chuck" lists all the amps he's tested and their performance. Most don't meet specs, a couple come close, the XTi 1000 was a huge disappointment. The aftermath of the XTi testing produced some interesting dialogue with CROWN on their website. It's a good read and produced changes at CROWN . . . . not in their equipment, sadly, only in their advertising and marketing.
post #1746 of 1917
Quote:
Originally Posted by mastermaybe View Post

Well since it's rated at 2400 watts bridged into 8 ohms, I'd like to think it's hitting that number (or more) from 20hz-20khz.

Thanks for the vote of confidence though.

James

Not to mention that you might not be getting a full 110/120v at you outlet. You have line sag due to long runs of wire from the box, some only realize <110v. And is the circuit dedicated, etc. You can't get full power when are you already low even if the physical design allows it, much less the marketing. Some manufactures play games with the input voltage too, feeding 130v+ gives more output that you will never see....
On some amps you will be lucky to get half of what is spec'd.
post #1747 of 1917
Quote:
Originally Posted by LINEARX View Post

You have to be careful NOT to give manufacturers too much credit for total honesty regarding the performance of their products.
At the beginning of this thread "Chuck" lists all the amps he's tested and their performance. Most don't meet specs, a couple come close, the XTi 1000 was a huge disappointment. The aftermath of the XTi testing produced some interesting dialogue with CROWN on their website. It's a good read and produced changes at CROWN . . . . not in their equipment, sadly, only in their advertising and marketing.

Well, I'm doing precisely that. Hence my inquiry.

I only need one amp so I am of course only concerned with finding one that's meeting or nearing its speca (or at least a threshold that will work for me). In this case the xti looks pretty darn flexible and offers a great 8 ohm rating. Now, I'm simply looking from someone who may have measured it so I can get a better idea as to it's perormance rather than anecdotal sceanrios that (unfortunately) can be notoriously unreliable.


James
post #1748 of 1917
You might want to try something used.

I picked up a couple of the older Crown CE4000s. They are amazing and handle loads well above and below specs, have great output, run very cool, and are usually affordable.
post #1749 of 1917
Quote:
Originally Posted by jpmst3 View Post

Not to mention that you might not be getting a full 110/120v at you outlet. You have line sag due to long runs of wire from the box, some only realize <110v. And is the circuit dedicated, etc. You can't get full power when are you already low even if the physical design allows it, much less the marketing. Some manufactures play games with the input voltage too, feeding 130v+ gives more output that you will never see....
On some amps you will be lucky to get half of what is spec'd.

I get a solid 119-121 at my outlet.

I realize there's plethora of over-specced amps out there.

I am not looking for those that do not...I know a good number exist that DO (or nearly) meet their specs.

I'm looking for one of THOSE, lol.

James
post #1750 of 1917
Ha, as luck would have it, it appears that a 3rd party HAS done a bit of testing on an xti 4000:http://www.abeltronics.co.uk/amptest...crown_XTI-4000

And if these are to be believed it appears the 4000 could be a good choice for me.

I mean unless it completely falls through the floor at 20hz, it's pumping out near 1100 @ 4ohms with both channels at 40hz, and I believe the problems with xti 1000 started at 50?

No bridged mono testing going on, but it's reasonable to conclude the stereo 4 and 8 ohm results could be nearly doubled?

EDIT: wait though, this appears to have been tested in the UK with a 240v line. Does that negate this performance?

James
post #1751 of 1917
Good find 'mastermaybe'. Interesting series of tests. It may be that operating the Crown XTi amps on 230 volts makes a significant difference in the positive results shown in those tests. I don't remember the CROWN website advertising better performance running on 230volts.
The tests low freq of 40 is NOT our DIY standard of 20HZ. The XTi 4000 measured 1089 watts @ 40HZ. It may well end up being only 600 to 700 watts @ 20HZ. But like I said, I have it driving an LMS-5400 and it makes all the volume from 10HZ-100HZ that I can stand.

Lots of other good amp tests in there too!

Crest Audio PRO-9200
Peavey CS4080
Peavey GPS3400
Peavey IPR-1600
QSC PLX 3002
QSC RMX4050HD
QSC PL4.0
QSC PL380
QSC PLX3402
QSC PLX 3602
Crown MA5002VZ
Crown XTi 1000
Crown XTI 4000
Crown ITECH 8000
Lab Grupen 1600
Powersoft K8

And a bunch more.
post #1752 of 1917
Thanks.

Seems like the 240v operation could just add more confusion, lol.

Well, seeing that the xti 4000 won't do the subsonic filtering I need anyway for my passive ED A7-450, I may as well look into other options, seeing I'm goign to end up using a minidsp.

Again, for what it's worth, outside of the poor performance of the xti 1000 in the early stages of this thread, I haven't read a bad word about them (the xti series), elsewhere. And the Crown tech I spoke pretty much scoffed at the idea that the amps were significantly underperforming down low.

Who knows?

James

James
post #1753 of 1917
Quote:
Originally Posted by mastermaybe View Post

Again, for what it's worth, outside of the poor performance of the xti 1000 in the early stages of this thread, I haven't read a bad word about them (the xti series), elsewhere. And the Crown tech I spoke pretty much scoffed at the idea that the amps were significantly underperforming down low.

I do recall that later on users tested their XTi series amps and found no audible differences...

The XTi 2 series is out now. It would be interesting to see the XTi 1002 tests.
post #1754 of 1917
^ Don't suppose you can point to a vendor? All those I find say they won't be available for another month?

And if I cannot go below 20hz with these for filtering purposes, they don't really put me ahead either.

James
post #1755 of 1917
Quote:
Originally Posted by mastermaybe View Post


Well, seeing that the xti 4000 won't do the subsonic filtering I need anyway for my passive ED A7-450, I may as well look into other options, seeing I'm goign to end up using a minidsp. James

Not exactly true.
It IS true the XTi has no "exact filters" to reduce damaging driver cone excursions below box tune but it DOES have a way to reduce the power from subsonic frequencies with built in power (watts) limiters that would accomplish the same thing.
Also the XTi can shape the output curve to eliminate the frequencies below a certain Hz to protect the driver from over excursion by using either the DSP Equalizer or the X-Over filter section with slopes ranging from 6db Butterfield on the minum side to 48db Linkwitz Riley on the maximum side. Both sections have +-15db capability.
This is part of that flexibility mentioned earlier
post #1756 of 1917
Quote:
Originally Posted by LINEARX View Post

Not exactly true.
It IS true the XTi has no "exact filters" to reduce damaging driver cone excursions below box tune but it DOES have a way to reduce the power from subsonic frequencies with built in power (watts) limiters that would accomplish the same thing.
Also the XTi can shape the output curve to eliminate the frequencies below a certain Hz to protect the driver from over excursion by using either the DSP Equalizer or the X-Over filter section with slopes ranging from 6db Butterfield on the minum side to 48db Linkwitz Riley on the maximum side. Both sections have +-15db capability.
This is part of that flexibility mentioned earlier

Hey my friend, I'm all ears!

I'm unfortunately getting so much conflicing information that it's driving me a bit nuts.

I mean when a Crown tech-head essentially tells me I cannot use it for this purpose what's an intelligent but dyi-greenie like me to do?!

What my understanding consists of is basically, this:

I CAN achieve the needed filtering/what have you to avoid damage, but NOT without significantly hampering the last hz's of output that this sub is capable of.


What I really need is likely a crash course on all of this and I do not expect anyone hear to administer one, but perhaps maybe a helpful hand as to where I can really get into the nuts and bolts of this entire subject.

One gentleman already provided what I THINK was an accurate depiction of these slope "widths" (octaves) and that helped quite a bit.

I'm now waiting for a conflicting definition of course.


thanks for the assistance, linearx.
James
post #1757 of 1917
Quote:
Originally Posted by LINEARX View Post

It IS true the XTi has no "exact filters" to reduce damaging driver cone excursions below box tune but it DOES have a way to reduce the power from subsonic frequencies with built in power (watts) limiters that would accomplish the same thing.

Wouldn't that also limit power at freq that the sub *can* handle?
post #1758 of 1917
^ This is/was my thoughts exactly.

I certainly know less than the vast majority around here, but I'm simply not seeing the avenue here where I'm NOT significantly reducing 13-20hz response and still protecting the driver.


BUT!

Here's my next question: let's say I implement a 12dboct slope at 20hz...will Audyssey XT 32 (upon the measuring process) recognize that the 450 IS capable of 13-20 hz output and "re-boost" these freq's up "x" number of db's to improve what the slope cut? Maybe not, as the amp already has it down so significantly so quickly. (?)


I've posed this question to multiple folks now and have yet to get a solid answer...this includes Crown techs.

Calling Audyssey now to hopefully get an answer!

James
post #1759 of 1917
Audyssey says that it will EQ based on what it finds the low freq rolloff point to be.

That will depend greatly on sub placement and room gain, so realistically you won't know until you try.
post #1760 of 1917
Quote:
Originally Posted by noah katz View Post

Wouldn't that also limit power at freq that the sub *can* handle?

The limiter will affect ALL frequencies.
However, since it's those subsonic frequencies that carry the huge watts (in this case near tune), the limiter most of the time comes into play (for home theater use anyway) only on those subsonics that would damage the driver with over excursion. How near to tune is a good question.
I've always wondered how exact we have to be when dealing with the subsonic filters. If we want a filter @ 18Hz and end up with actual operating filter being 16Hz, have we placed our driver in jeopardy? I think a good policy would be to proceed with caution and find out exactly where in your system the danger lies. A good dose of cautious trial and error is in order.
In the PRO application the limiter is used for any and all frequencies where the user is attempting to get the last little bit of USEFUL power into the sound system without clipping the amp or burning VCs of the drivers.
The next step, of course is to have expander and compression equipment to limit total sound levels to avoid having lost soft sounds and limit loud peaks.
There are an awful lot of ways to, skin the cat, available for the home theater officianado now days. Most of "todays" AVRs have systems that will
produce a flat useful frequency response (MCACC and Audyssey) and supply a sub-out for those of us that need our daily dose of double digit dig down deep subsonic low stuff.
Then we can add a PRO amp with thousands of watts to supply 18" 85 pound sub drivers . . . . or even 21" behemoths that'll play down to almost "nothing" Hz and do it all in the name of entertainment.

Ain't we-all somethin?
post #1761 of 1917
Let's make things more complicated, or fantastically more simple:

Just spoke to an Audyssey rep, he told me in no uncertain terms:

"A SUBSONIC FILTER IS NOT NEEDED WITH AUDYSSEY AS NO INOFRMATION IS SENT TH THE SUB BELOW ITS -3DB POINT."

Ok. This was my inclination all along, but I simply ignored it as I thought there would never be such a throng of filter-advocates who either: A. didn't use audyssey. B. didn't realize this fact. or C. Simply wouldn't mention it when someone like me asked and included the fact that I intedned to use Audyssey.

Is this true?

James
post #1762 of 1917
Quote:
Originally Posted by mastermaybe View Post

spoke to an Audyssey rep, he told me in no uncertain terms:

"A SUBSONIC FILTER IS NOT NEEDED WITH AUDYSSEY AS NO INOFRMATION IS SENT TH THE SUB BELOW ITS -3DB POINT."
James

I doubt that it's true. There isn't any filter that I've ever heard of that has a 100db slope.
But more to the point, in your "Captivator", according to the manufacturers specs, useable output is 130db @ 60Hz and 121db @ 20Hz a difference of 9db.
If your manufacture's rep is correct, the Audyssey will not produce anything below approx. 25Hz because that is about where the -3db point is.
post #1763 of 1917
thanks. ^ Just found out on the Audyssey thread that I've now been misinformed by a Crown and Audyssey tech on the same day.

There is no filter with Audyssey. It simply WON'T BOOST below the 3db point. Anything else is free to c'mon down and be the next contestant on: "Destroy James' Sub" (cue the music).

Pretty pathetic when that's EXACTLY what I poposed when he said I was "safe".


BTW: I've decided upon a passive ED A7-450 instead of a Captivator.

James
post #1764 of 1917
Quote:
Originally Posted by LINEARX View Post

I doubt that it's true. There isn't any filter that I've ever heard of that has a 100db slope.
But more to the point, in your "Captivator", according to the manufacturers specs, useable output is 130db @ 60Hz and 121db @ 20Hz a difference of 9db.
If your manufacture's rep is correct, the Audyssey will not produce anything below approx. 25Hz because that is about where the -3db point is.

In any event, I assume that's max ouput and 75/85db test tones would reveal a much lower -3db point.

James
post #1765 of 1917
Quote:
Originally Posted by mastermaybe View Post

BTW: I've decided upon a passive ED A7-450 instead of a Captivator.
James

Darn! We haven't seen or heard much from owners about the "Captivator" we've heard a lot about the Ed subs.
Good luck. Let us know how it works out and what amp you choose. Lot's of choices.
post #1766 of 1917
Quote:
Originally Posted by mastermaybe View Post

I get a solid 119-121 at my outlet.

Under full (or at least high) load of the amp or at idle / just loafing along? Potentially big difference there.
post #1767 of 1917
Quote:
Originally Posted by whoaru99 View Post


Under full (or at least high) load of the amp or at idle / just loafing along? Potentially big difference there.

According to my panamax, pretty solid all the way to a 10+ amp draw.

Jamed
post #1768 of 1917
Well, that's not bad, but consider a 3-4kW amp on the test bench or in your living room, trying to test full continuous output, will be looking for something on the order of 35-40A, give or take from the AC mains.
post #1769 of 1917
James,

I think there are two different issues with the Xti amplifiers.

One is the problem that Chuck found where the Xti 1000 had low power output below 100Hz. As the frequency decreased, so did the power output. Crown seems to have fixed that. My Xti 2000 amplifiers never suffered from that problem. See posts 1413 and 1428.

The second problem is the DC protection circuitry. To detect DC voltage at the amplifier output, a low pass filter at maybe 5Hz is applied to the output. Then the resulting signal is rectified into DC. This DC voltage is compared to some reference DC voltage level. If it gets above the reference voltage, the protection trips. The important thing to realize is that there could be either an actual 10VDC signal at the output of the amplifier or 20VAC of signal spread from 3-5Hz and no actual DC. Both of these could trip the DC protection circuit. How sensitive the DC protection circuit is to AC signals is a function of the LP filter frequency and the slope.

The problem occurs when you apply eq below about 40Hz to the signal. If your enclosure+driver is -3dB at 40Hz and you want the system to be -3dB at 10Hz, you need to apply 24dB of boost at 10Hz. When you do this, you are also going to be boosting frequencies below 10Hz. How much is a function of the eq filter type. It is easy to end up applying enough boost in the upper frequency range of the DC protection circuit to trigger it. This can occur at levels much lower than the amplifiers maximum power output. If you test for power output with sine waves, above 10Hz, you will never see this problem on the test bench.

My guess is that Crown doesn't care about this issue at all since the amplifier is designed for live sound applications where no one is boosting anything below 40Hz, so the problem doesn't occur.

You mentioned above that you found something about Crown making improvements to these problems on their website. If you can provide links, that would be appreciated.
post #1770 of 1917
Quote:
Originally Posted by Jack Hidley
James,

I think there are two different issues with the Xti amplifiers.

One is the problem that Chuck found where the Xti 1000 had low power output below 100Hz. As the frequency decreased, so did the power output. Crown seems to have fixed that. My Xti 2000 amplifiers never suffered from that problem. See posts 1413 and 1428.

The second problem is the DC protection circuitry. To detect DC voltage at the amplifier output, a low pass filter at maybe 5Hz is applied to the output. Then the resulting signal is rectified into DC. This DC voltage is compared to some reference DC voltage level. If it gets above the reference voltage, the protection trips. The important thing to realize is that there could be either an actual 10VDC signal at the output of the amplifier or 20VAC of signal spread from 3-5Hz and no actual DC. Both of these could trip the DC protection circuit. How sensitive the DC protection circuit is to AC signals is a function of the LP filter frequency and the slope.

The problem occurs when you apply eq below about 40Hz to the signal. If your enclosure+driver is -3dB at 40Hz and you want the system to be -3dB at 10Hz, you need to apply 24dB of boost at 10Hz. When you do this, you are also going to be boosting frequencies below 10Hz. How much is a function of the eq filter type. It is easy to end up applying enough boost in the upper frequency range of the DC protection circuit to trigger it. This can occur at levels much lower than the amplifiers maximum power output. If you test for power output with sine waves, above 10Hz, you will never see this problem on the test bench.

My guess is that Crown doesn't care about this issue at all since the amplifier is designed for live sound applications where no one is boosting anything below 40Hz, so the problem doesn't occur.

You mentioned above that you found something about Crown making improvements to these problems on their website. If you can provide links, that would be appreciated.
Thanks Jack, there was indeed a link on the site regarding an "improvement" but that had to do with fixing something causing the amps to actually fail altogether, not that this "issue" (which they seem to not even acknowledge, see below) was remedied.

The Crown tech I spoke with vehemently denied the amps suffered from any kind of low end shortcomings during actual use and scoffed at the notion of using 2 and 4 ohm sine waves to gage an amps ability to do "real work".

Please remember these are his words and ideas, not mine.

I have to say that I've yet to read anyone unhappy with an xti 2 or 4000 so this is a bit of a conundrum for me as I can pick up the 4000 new relatively inexpensively ($400), but I'd pay another $100 for piece of mind if need be.

Seems the Crown XS900 should now be on my list as it appears verified to push out quite a bit of power bridged into 4 ohms as well as into a stereo 4 ohm load. This way I could potentially throw my second A7-450 on it down the road.

I've of course considered the behringer EP 4000 as well. Any other ideas for a solid hi powered 4 ohm pro amp between 3-$500?!

Thanks for the help Jack,
James
New Posts  All Forums:Forum Nav:
  Return Home
  Back to Forum: DIY Speakers and Subs
AVS › AVS Forum › Audio › DIY Speakers and Subs › Measuring Amplifiers