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My New Crown XTi 1000s Are Here!!


BEC

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So distortion measures low and there's barely any noise in the measurement, yet your scope traces look like that? I guess it's kinda hard to see the actual scale, but I find that kinda surprising...

Do you hear the noise?

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This is one hell of a free service you guys are providing to Crown. Has any amp ever been tested to this degree in so many places in such a short period of time I wonder?

Now - Shawn:

for the non-techies - what do those results mean? You seem to be saying no distortion and then lots of distortion at the same time depending on how you measure. Which measurement more accurately reflects the listening experience?

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Here's one for you.

I had a few hours yesterday afternoon to spend some time with my system without distraction, and decided to try one of the Crowns on another set of speakers -- I've only ever heard them on the Jubilees. I pulled out my refurbished old Advents for what I thought was going to be an afternoon of good listening.

The sound rated up there with some of the worst sound I've heard in my 30 years of audio -- profoundly bad. I've been listening to Advents off and on since high school, and I've heard them on a lot of different stuff -- it ain't the Advents. I simply can't think of a single positive thing to say about what I heard. Cloudy, congested, with the upper registers putting the squeeze on my ears at less than 90dB. I must say, I'm very impressed that Mark managed to spend 4 hours with it -- I lasted less than six songs. It's a completely different sound and presentation on the Jubilees -- I don't get it.

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Here's one for you.

I had a few hours yesterday afternoon to spend some time with my system without distraction, and decided to try one of the Crowns on another set of speakers -- I've only ever heard them on the Jubilees. I pulled out my refurbished old Advents for what I thought was going to be an afternoon of good listening.

The sound rated up there with some of the worst sound I've heard in my 30 years of audio -- profoundly bad. I've been listening to Advents off and on since high school, and I've heard them on a lot of different stuff -- it ain't the Advents. I simply can't think of a single positive thing to say about what I heard. Cloudy, congested, with the upper registers putting the squeeze on my ears at less than 90dB. I must say, I'm very impressed that Mark managed to spend 4 hours with it -- I lasted less than six songs. It's a completely different sound and presentation on the Jubilees -- I don't get it.

[:^)]

OK - did you change the settings when changing the speakers - I guess you must have done. Is there perhaps one setting that is critical to getting this weird thing to play properly? It really does seem to be a twilight zone product.

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"So distortion measures low and there's barely any noise in the measurement, yet your scope traces look like that? I guess it's kinda hard to see the actual scale, but I find that kinda surprising..."

Scale on the FFT is vertical from -80dB to 0dB linear scale and horizontal from 0 to 20kHz again linear scale. Noise is either below the FFT (which has more like 60 or 70dB of range) or above 20kHz.

"Do you hear the noise? "

Haven't hooked it to a horn yet, those are in a different room. On a small 2 way I could hear a little hiss right up at the speaker and there was also so hum if the input pots were turned all the way up.

I want to redo those measurements with the internal volume control ahead of the DAC turned down and see what happens then. That way you will have more signal through the A/D (more resolution there) and the same resulting signal level in the D/As.

Shawn

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Here's one for you.

I had a few hours yesterday afternoon to spend some time with my system without distraction, and decided to try one of the Crowns on another set of speakers -- I've only ever heard them on the Jubilees. I pulled out my refurbished old Advents for what I thought was going to be an afternoon of good listening.

The sound rated up there with some of the worst sound I've heard in my 30 years of audio -- profoundly bad. I've been listening to Advents off and on since high school, and I've heard them on a lot of different stuff -- it ain't the Advents. I simply can't think of a single positive thing to say about what I heard. Cloudy, congested, with the upper registers putting the squeeze on my ears at less than 90dB. I must say, I'm very impressed that Mark managed to spend 4 hours with it -- I lasted less than six songs. It's a completely different sound and presentation on the Jubilees -- I don't get it.

Wow!

http://cls.audiogon.com/cgi-bin/cls.pl?ampstran&1212445503

Double Wow!

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Dean,

I totally agree with your assesments...........I felt the very same way with the HK 730/930 Receivers..............what was all the hoopdala............

Too each their own..........

But what a flip in the middle of the stream!

Makes no difference to me I have never even heard one but WOW!

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Max,

"You seem to be saying no distortion and then lots of distortion at the same time depending on how you measure."

Distortion (harmonic distortion) is pretty low. That would be distortion related to the fundamental itself. So if you input a 1000hz fundamental signal distortion could occur at 2k,3k,4k,5k,6k...etc...etc. You can see this in the FFT as it breaks this all down for you.

The scope basically shows you everything that is going on with the signal. In these pictures the 'corruption' of the sine isn't due to distortion but to noise as can be seen by looking at the averaged signal. Averaging on the scope makes the signal(s) that are correlated between measurements stand out more from random signal. The samples that are correlated between measurements would be the fundamental AND the distortions, random signal is noise.

"Which measurement more accurately reflects the listening experience?"

They are both useful. Looking at just the FFT and you don't really see the noise, but looking at just the scope (without averaging) makes the fundamental look terrible when in reality the fundamental itself is fine (low in distortion) but something else is altering what the scope is showing.... noise. THD is pretty low (higher at 5kHz though) but THD+N is higher. The scope doesn't really tell you where the noise is though and the FFT isn't really showing it either. Is it lower in level the the signal and in the audible range... or is it above the audible range and higher in level? From these measurements we can't really say.

If I get a chance I will run this through WinAudioMLS as it has a greater dynamic range (can see more noise to a lower level) and will measure THD and THD+N directly.

What will be interesting is how various level settings in the Crown may alter this. For example turning down the digital control ahead of the DACs will mean you have to put more signal into the amp (and into the A/D) for the same output. That will give more resolution through the A/Ds with the same output of the D/As (for same output level from amp).

That may or may not improve things. Likewise if I add some attenuation after the D/As (I'll have to pull the board to trace this out... the DACs outputs are on the bottom layer) you can have more signal through the A/D and D/A to increase SNR there.

I also want to test the output of the DAC itself to see if the rising FR is from the digital section or in the amp itself. While doing that I can also look to see if the distortion is in the digital section or not too. Based on the harmonics it looks like it might be in the amp unless Crown left out the filtering on the D/As. I was seeing a harmonic at 30kHz which if that was in the digital stage should have been filtered out by the reconstruction filter. (Assuming a 44.1kHz or 48kHz sampling rate... haven't measured that yet)

Shawn

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Here's one for you.

I had a few hours yesterday afternoon to spend some time with my system without distraction, and decided to try one of the Crowns on another set of speakers -- I've only ever heard them on the Jubilees. I pulled out my refurbished old Advents for what I thought was going to be an afternoon of good listening.

The sound rated up there with some of the worst sound I've heard in my 30 years of audio -- profoundly bad. I've been listening to Advents off and on since high school, and I've heard them on a lot of different stuff -- it ain't the Advents. I simply can't think of a single positive thing to say about what I heard. Cloudy, congested, with the upper registers putting the squeeze on my ears at less than 90dB. I must say, I'm very impressed that Mark managed to spend 4 hours with it -- I lasted less than six songs. It's a completely different sound and presentation on the Jubilees -- I don't get it.

Well, there are others that are agreeing with me and now I don't feel so bad. The amp isn't a "bomb" with the jubilees biamped but can be unsatisfying in other applications. Works great on my subs right now with good software features to tweak.

jc

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I'll be using Cullison's DBX Driverack PA with K2 and other Crown DC amps. Hopefully that will be a smoother sound. We'll see. I have no direct experience with the Xti's. There are a lot of guys buying a pair for powering/tweaking Jubilees and they seem like a lot of features for the buck, unless....

M

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Shawn,

I had to get onto other pressing things around here and away from the Crown testing, but at the end of that testing I was doing, I was trying inductive loads on the Crowns and was getting some confusing results. A bad test lead faked me out once, but I still think the Crown is effected in strange ways when driving an inductive load (like a speaker). If I am right, that might be an explaination of the greatly different levels of satisfaction when used on different speakers.

Bob Crites

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