Crown Xti front panel messages

Gene Hardage

Gene Hardage

Junior
Jan 14, 2011
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St. Pete-A-Bug FLA
www.sarasotaslim.com
Not sure if this is the right place to post this but it seems like a good spot so here goes. For the 2nd time I have been amazed by some warning message on the little screen on the front of a Crown Xti amp. The first time it happened about 2 years ago the warning message said something like short or protect because I had a few strands of wire that got loose in one of my NL4 speaker cables and it was shorting out - so I used a different cable and all was well. Today I was firing things up and I noticed a quick warning message on the front panel that said something like low line before it clicked on all the way. A dummy check on the front of my other rack showed that voltage was at 95! Of course having a power strip with the voltage readout is handy and I probably would have caught it eventually buy having that quick warning made me take notice right away and we were able to adjust the generator to 115 so again all was well. These newfangled amps are spiffy :)~:)~:smile:
 
Re: Crown Xti front panel messages

Spiffy, yes.

Just note that the "short" warning is not always accurate. There is a bug in the software that allows the amp to declare a short if a channel with speaker connected is muted and that speaker is then sufficiently excited to cause back EMF. The amp will think it sees a short, issue the warning and will also unmute the channel. Messed me up a few times til I figured out WTH was happening.
 
Re: Crown Xti front panel messages

Bennett Prescott said:
You plugged into a genset without metering it?
Click to expand...

I've been living a sheltered life - so yes. When we arrived it was running and lights were plugged in and a breakout distro was already hooked up so like a dummy I just jumped on that WhisperWatt bandwagon. I suspect they just dropped it off and never really adjusted anything on it before they left. I'm packing my handy dandy multimeter as we speak and tomorrow's generator will be probed prior to plugging in.
 
Re: Crown Xti front panel messages

john lutz said:
Spiffy, yes.

Just note that the "short" warning is not always accurate. There is a bug in the software that allows the amp to declare a short if a channel with speaker connected is muted and that speaker is then sufficiently excited to cause back EMF. The amp will think it sees a short, issue the warning and will also unmute the channel. Messed me up a few times til I figured out WTH was happening.
Click to expand...

The "bug" you speak of is really just Crown lowering the output power of all their amps to reduce warranty returns. Every firmware "update" simply lowers output power and shows warning messages anytime the amp is forced to put out any power at all.
 
Re: Crown Xti front panel messages

Rob Timmerman said:
That's an interesting theory. Got any data to back it up?
Click to expand...

It is not a theory, and yes. I do. I tested 4 of my 12 xti4000 amps by loading fw1.000 (factory firmware from the very first hardware revision of amplifiers) and saved that fw file on my computer. Then, I got out my fluke 199c 003s meter which was calibrated by fluke at the time and measured the output voltage of the amplifier using the internal pink noise generator with the amplifier connected to a 2ohm purely resistive dummy load in stereo. So, one channel driven at 2 ohms at maximum output from the internal pink noise generator and I measured the voltage. then, I took the same amp and loaded a later version of firmware 1.4 and repeated the measurement, then loaded the most recent firmware and repeated the measurement. The results did not surprise me. For every firmware update, the amplifier "loses" 6% of its total max output voltage into a 2 ohm load. When I stopped updating firmware, the same xti4000 went from 1988watts per channel into a 2 ohm load to 1426 into a 2 ohm load. The interesting thing about this experiment i did (way back when I thought the xti was a good amp) was that one could blow the circuit breaker in the amp by doing my experiment with the factory firmware, with subsequent firmware updates, it was impossible to blow the breaker. This whole experiment was repeated with 4 xti4000 amps manufactured on different dates with the exact same results. I called crown on it, but they simply replied that "xti amplifiers remained within specifications regardless of firmware revision." You decide for yourself what that means. Shortly thereafter, I sold all my xti amps.

For anyone who is interested, I actually still have my purely resistive 2000w dummy load--which was the most impossible thing to find I have ever looked for.
 
Re: Crown Xti front panel messages

Gene Hardage said:
I've been living a sheltered life - so yes. When we arrived it was running and lights were plugged in and a breakout distro was already hooked up so like a dummy I just jumped on that WhisperWatt bandwagon. I suspect they just dropped it off and never really adjusted anything on it before they left. I'm packing my handy dandy multimeter as we speak and tomorrow's generator will be probed prior to plugging in.
Click to expand...

Fluke 117 Electricians True RMS Multimeter - Amazon.com

Bennett Prescott tested, mother approved. Best cheapest meter you can buy for this sort of thing.
 
Re: Crown Xti front panel messages

Tim,

1) How did you engineer a dummy load with no inductance or capacitance?
2) Did you monitor the temperature of your load throughout the testing, or at least its resistance, and at the end of your testing did you re-flash to the original firmware to confirm that the power delivered returned to normal?
 
Re: Crown Xti front panel messages

Bennett Prescott said:
Tim,

1) How did you engineer a dummy load with no inductance or capacitance?
2) Did you monitor the temperature of your load throughout the testing, or at least its resistance, and at the end of your testing did you re-flash to the original firmware to confirm that the power delivered returned to normal?
Click to expand...


1) I special ordered scientific power resistors which have no temp shift and no reactance of any type. They were both expensive and unavailable to normal people. I had to use scientific channels to acquire them. note: they look nothing like conventional power resistors.
2) I did reflash all my amps to the first firmware before I sold them and confirm that more power came out of every single one.
 
Re: Crown Xti front panel messages

Tim Duffin said:
The "bug" you speak of is really just Crown lowering the output power of all their amps to reduce warranty returns. Every firmware "update" simply lowers output power and shows warning messages anytime the amp is forced to put out any power at all.
Click to expand...

Anyways.....I do not think that is what I am describing at all. What I am describing is a specific amp behavior that anyone with an XTi can see for themself.

I was simply commenting to the op's observation of "spiffy" features and pointing out a "bonus feature". That being that under certain conditions the amp gives a false short warning and unmutes a muted channel. It takes back EMF to do it.

Now, what that may mean for XTi's overall performance, I have no idea.
 
Re: Crown Xti front panel messages

john lutz said:
Anyways.....I do not think that is what I am describing at all. What I am describing is a specific amp behavior that anyone with an XTi can see for themself.

I was simply commenting to the op's observation of "spiffy" features and pointing out a "bonus feature". That being that under certain conditions the amp gives a false short warning and unmutes a muted channel. It takes back EMF to do it.

Now, what that may mean for XTi's overall performance, I have no idea.
Click to expand...


Actually, it is. The behavior you describe only happens in some firmware versions. (later versions) if you "downgrade" to the first firmware--that entire problem miraculously disappears.

Try it. I already have.
 
Re: Crown Xti front panel messages

Tim Duffin said:
Actually, it is. The behavior you describe only happens in some firmware versions. (later versions) if you "downgrade" to the first firmware--that entire problem miraculously disappears.

Try it. I already have.
Click to expand...

Since it was Crown who first called the odd behavior I am describing a "bug", I will use that term.
Even if it is true that this bug only shows up in later "output reducing" firmware versions how do you know that this bug is part of whatever controls power output and not just another unintentional random annoying bug?
 
Re: Crown Xti front panel messages

Tim Weaver said:
Do you know (or suspect) that the output of an xti has been reduced at 8 or 4 ohm loads?
Click to expand...


I do not know, because I could not get my hands on a purely resistive 2000 watt 4 or 8 ohm dummy load. My test reflects only 1 specific use of the xti amps; 2 ohms stereo. I would imagine that since the amp is not pushed to its limits at 4 or 8 ohms, the average user would not know that they are being shortchanged and therefore would believe that the device is working normally.
 
Re: Crown Xti front panel messages

Tim Duffin said:
1) I special ordered scientific power resistors which have no temp shift and no reactance of any type. They were both expensive and unavailable to normal people. I had to use scientific channels to acquire them. note: they look nothing like conventional power resistors.
2) I did reflash all my amps to the first firmware before I sold them and confirm that more power came out of every single one.
Click to expand...

I have a 2.5kW (per channel at 2 ohms) fan-cooled bank I built for amplifier engineering. Its resistance shift over a 24 hour period is less than 0.1%! :)~:)~:smile: Inductance is also insanely low due to its planar construction. Its thermostatically controlled fans keep it from becoming the lab's EZ Bake Oven. The resistors themselves are around $60 each, but I bought mine on eBay as "Motor Brake Resistors". They're made by EBG (UXP 300) and are specifically designed for handling incredibly high transient power.

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