My New Crown XTi 1000s Are Here!!

[Deang]

Where are the bad measurements?

[BEC]

Where are the bad measurements?

We will have to get those from Mark. I could not find anything bad to measure.

Bob

[Deang]

Interesting way of wording that. So, since it measures good, it must sound bad.

[BEC]

Wow Mark. That would be a big crt and some big graph paper to show you 80 db signal to noise at 1 db per major division. I think I will just call this one close enough. I am from the old school with my amp test training way back in the 60s. I am sure there has been some progress since then, Heck we were even using tube amps back in those days.

Bob

[BEC]

I'm sure you can manage this, right?

Mark,

I really can't do the square wave test right now. Rebuilding the shop and can't get to my scope.

But, can you address the one number you did give on the Crown?. You said it was "brick wall limited at 20 khz". I measured the FR out to above 23 khz.

Also could you confirm or refute the 75 to 80 db signal to noise I measured? I know you wanted better resolution, but did you get close to that?

Bob

[sfogg]

"I'm sure you can manage this, right?"

No need to. Anyone that understands what a square wave is will and what the Crown is doing will know exactly what the 10kHz square wave will look like.

Shawn

[mark1101]

Bob, I'm glad the amps arrived safe and sound and appear to be working good, sounding good, and measuring good.

Others, I doubt any measurements can convey what an amp, any amp, actually sounds like. I know there is probably a good sized group that disagrees with some of my negative comments made about the sound of the XTI. Some agree with me. Doesn't matter. That's fine. I will remain in the minority with my opinion. However, it is just an opinion and others need to judge equipment by themselves and from their own listening. People should not pass over this amp and "solution".......because it is much more than just and amp..........because of anyone's opinion.

I always maintained that the XTI was a good value for all it can do. It would cost big bucks to try and duplicate all those features in separate components. It has an excellent user interface in the Harmon PC software which makes getting into speakers such as the Jubilee much less expensive. Many feel that this so called "less expensive" method even sounds like an audiophile solution. Many. So, I won't argue the point. Just hold my opinion.

Bob, you got a good deal and some cool looking amps. I always thought those Crowns were very slick looking. I'm sure you will enjoy the power (I did), and put the amps to good use.

[Deang]

"I know you are just dying to stick me on this..."

Yeah, that would be cool. [][] Really, I felt that way last week, but not so much now.

This amp is intended to be used at high power. The measurements at low power were unimpressive to me, and I was hoping to find some confirmation of their validity, But because I didn't have a way to confirm the numbers, I am not going to cite them."

I feel bad that you had to dig through that awful thread to find that. There were some things you said later in that thread that indicated some of the measurements might be "bad" -- you also said, "It was totally unacceptable for any home amplifier I'd be interested to own and use..." We talked about all this before and there's no reason to get into it all over again. I apologize for some of the things I said in that thread and I have no intention or desire to go down that road again! Right now, it more's about just trying to get a handle on why opinions regarding the sound are at opposite extremes. Did you catch Chris Robinson's comments after he heard Cask05's Jubilee/Crown setup? Chris is a huge SET/Klipschorn guy, and he said:

"I was trying to think of the best way I could describe them, but Rick said it at the end of our visit, and I thought it was right on. He said, "Those are really easy to listen to ..." I couldn't agree more. Ever have gear just scream at you and try to drill holes through your forehead? Well these are definitely not them. The two-way design and HUGE 402 horn just put out a seamless sound field that follows you around the room like Mona Lisa's eyes. The integrity of the music remains intact, and the emotional impact of the music is supreme."

Things just aren't lining up in any kind of way that makes sense and it's frustrating!

[Deang]

Man, that looks like crap, I'm going back to passives and tubes.

[PrestonTom]

Please Guys let's not turn this into another 30 page thread.

All of us know that a square wave at 10 kHz through a 20kHz brick wall filter will not look square. It may not be very audible either.

All of us know that a high frequency phase shift (that can make the square wave look like a sawtooth waveform) may not be very audible either.

All of us know that a 0.5 dB decrement at 5 kHz may not be terribly audible either (or would certainly be obscured by the transducer and the room).

Let us not waste Bob's time, he has got a shop to re-arrange and a business to get back to.

Quite frankly I have no idea why Stereophile uses some of those test signals or why they expand the scale (suggesting that the detail is relevant).

Good Luck,

-Tom

[sfogg]

"That's correct. Which is why I mentioned the brick wall filter. With a
sample rate of 44khz, you can't get past the Nyquist frequency. Result:
very lumpy response in the passband - as you can see if you magnify
Bob's 10dB chart to a more reasonable resolution. If this is impressive
for people - fine. It wasn't to me. "

That is not at all what I said. There is no reason whatsoever that the Nyquist frequency results in 'very lumpy response in the passband.' That is nonsense, look at CD players (that also are limited by the same Nyquist freqency) and you can find ones that are +/- well under a dB over their bandwidth. Not saying the Crown may or may not show a response like that, but if it does it isn't because of the sampling rate.

What I said is anyone that understands a square wave and what the Crown is doing will already know what a 10kHz square wave will look like without measuring it. The Nyquist frequency results in is a very hard upper frequency response limit. If the Crown is sampling at 44.1kHz (possible with a 23kHz top end) then if one plays a 10kHz square wave through it it is going to come out looking exactly like a 10kHz sine wave. And the reason for that is a 10kHz square wave is nothing more then a 10kHz sine wave with lots of odd order harmonics. The first odd order harmonic is at 30kHz which is above the bandwidth of the amp. So all that makes it through is the fundamental sine wave.

This isn't of the Crown but the Crown will measure the same wave... bottom trace is the test signal, top trace is the output of the device.

Shawn

[mikebse2a3]

Agreed. I have no interest in a measurement peeing contest whatsover. At this point I am simply defending one word of mine "unimpressive." Anyone is free to be as impressed or un, as they like. Lumpy frequency response on the neighborhood of plus minus 1 or 2 dB is not typical of home audio amps.

If, on the one hand, we are going to constantly claim that, "in AB tests you must level match to 0.1dB" and then when measuring an amp we get 20X that variation and think it isn't audible, I think we have a bit of contradiction going on.

.................................................................................................

Yes plenty of contradiction going on here!

I respect and use tube amps but hook any tube amp to any real world speakers and watch the frequency response shift several db as it tracks the speakers impedance variations.

So even though by nature tube amps aren't perfect we find that they can often give very impressive sound reproduction! So if the Crown measures certain ways due to design goals it is unimpressive! Talk about the Pot calling the Kettle Black.[]

mike tn[]

[mikebse2a3]

Agreed. I have no interest in a measurement peeing contest whatsover. At this point I am simply defending one word of mine "unimpressive." Anyone is free to be as impressed or un, as they like. Lumpy frequency response on the neighborhood of plus minus 1 or 2 dB is not typical of home audio amps.

If, on the one hand, we are going to constantly claim that, "in AB tests you must level match to 0.1dB" and then when measuring an amp we get 20X that variation and think it isn't audible, I think we have a bit of contradiction going on.

.................................................................................................

Yes plenty of contradiction going on here!

I respect and use tube amps but hook any tube amp to any real world speakers and watch the frequency response shift several db as it tracks the speakers impedance variations.

So even though by nature tube amps aren't perfect we find that they can often give very impressive sound reproduction! So if the Crown measures certain ways due to design goals it is unimpressive! Talk about the Pot calling the Kettle Black.

mike tn

The measurement we are referring to Mike is into an 8 ohm resistor, not a speaker. I've measured maybe - - a dozen SS home audio amps, and never saw one like this into a RESISTOR. So, pots and kettles calling each other black doesn't come into play here.

"Lumpy frequency response on the neighborhood of plus minus 1 or 2 dB is not typical of home audio amps."

It is when you use a tube amp with a typical speaker Mark! you can't have it two ways Mark! By your own criteria the Tube Amp isn't fit for home use!

mike tn[]

[mikebse2a3]

OK seriously!

You can't listen to amplifiers through 8 ohm resistors so even though you can obtain usefull information from that it far from tells the whole story.

It is very rare for any speaker to give anything close to a resistive load and those that get close often use impedance compensation networks so the fact is looking at an amplifier into a steady resistive load has very limited value!

I ran the amp up to about 200W into an 8 ohm resistive load and the power supply squeeled, groaned, moaned and vibrated in a dreadful way. The noise out of that supply was so loud I am sure it could be heard at 20 feet. Now mind you, that was ONE channel not even up to full power into a simple resistive load. I have never had a high power SS audio amp make those kinds of internal noises before. Again, my words were along the lines of "this would be totally unaccceptable in a home audio amp" - - and it IS! But, that's just my opinion. Look, jillions of guys here are getting off using these big pro amps, and I don't care, none of my business, but I think I have a reasonable right to my own opinion about them, and I gave it.

I'm not sure how Crown is using it's PWR Supply but if it is of some tracking form based on the music signal's demand then driving steady state (which music isn't) would most likely not represent what the amplifier was really designed for but instead it's PWR supply was designed for real world musical peaks reproduction ( Krell, Threshold, Carver and many more have used similar methods) and to test under steady state conditions might explain unusual noise from the PWR Supply.

mike tn[]

[jacksonbart]

Yes, 23 khz is roughly what I got. I rounded it down to 20 khz to underscore the implications of this kind of response. .

Gee that sounds like a very fair & balanced way to present measurements.

[mikebse2a3]

Hi MIke--

What's important is that if you like the way the amp sounds, that's all that matters, right? Who cares about the specs? Dig what you hear.

Hey Mark []

Well I have to say No! Both are very important IMHO. Knowing how to use both is very important also IMHO!

Let me give you one example Mark.

My using the Jubilee with active crossover and Tube Amplifiers is a good case for why both specs and listening matter!

As I mentioned earlier knowing that Tube Amplifiers have a relatively high output impedance(specs) compared to solid state amplifiers I wanted to have the best of both worlds which was to limit the tonal shifts due to the Tube Amp's output impedance interacting with the Jubilee's LF Horn and HF Horn impedance changes. So I asked Roy if he would supply me with impedance compensation network values to acheive this. What resulted was I implemented them with the HF Horn/Amp and it resulted in a tighter frequency response (approximately 2db) when tube driven. What is noticed is a slight tonal shift between the two conditions. It's not night and day but it is audible and more accurate when used with the impedance compensation.

mike tn[]

[mikebse2a3]

Oh. I thought we were talking about the Crown Xti 1000.

The way the ground is shifting here, I don't know what anyone is talking about anymore. Jubilees, tube amps, active crossovers, equalization curves? I was only posting in this thread about the Xti, and more specifically about Bob's measurements vis a vis my original comments! But yeah, if you equalize something, it changes the tone, that is for sure.

Mark I responded to your question with a reasoned answer with a good example of why both Specs and Listening are important!

Sorry you didn't appreciate the answer but you aked a question which I thought was important because alot of people want to say all that matters is how it sounds yet one example proves it's false to think that way! But I guess thats not the Topic!

So everyone be warned in this thread only talk about the Crown Xti and BEC's test will be allowed from this point forward!!!!!! per Mark

mike tn[]

[mikebse2a3]

heh, heh, well, I say let anyone talk about whatever they like. My point Mike, is that when I said to you a few posts ago, "if you like the way it sounds, the specs don't matter" - the "it" I was referring to was the Crown, and the "specs" I was referring to were Bob's measurements, or any other measures mentioned. I thought it was a simple enough comment. It almost feels like you are trying to go out of your way to be contrary, which is fine too, but at least understand what my remark was intended to mean. Yeah sure, other specs about other topics mean other things.

If you call responding to your comments as contrary then guilty!

The trouble with forum communication is it's easy to misunderstand someone and all I know to say to you Mark is that you are expressing your thoughts, opinions and I'm responding with mine and trying to be intelligent and respectfull while doing that. Hopefully the end result is people learn something with these exchanges and maybe sometimes we are fortunate enough to learn something not directly but indirectly related to the topic at hand as well.

mike tn[]

There seems to be some hostility toward ME concerning this amp, which is pretty hard to understand. Bob is the guy who made the measurements, and I think they speak for themselves. By which I mean, anyone is free to be be impressed, or unimpressed as they see fit. By reading some of these threads, you'd almost get the idea that the Xti 1000 was a Sacred Cow or something. It's just an amp fellas. If it's working for you, enjoy it.

[BEC]

OK first report on the sound. With the room as quiet as I could reasonably get it, did some ear up to the speakers listening for noise. I could hear a bit of noise out of one channel of tweeters, but not the other. That is with the ear right up inside the tweeter horn. I could not hear it 3 inches away. My son Michael is younger and has more sensitive ears than I. He could hear the noise at 3 inches from one tweeter and around a foot from the other tweeter. Neither of us could hear any noise at a normal listening distance.

Next we heated the amp up playing about 30 minutes of tunes at "pretty loud" volume. Then repeating the listening for noise test, results were the same. Fan in the amp was on for a couple of minutes after that 30 minutes of relatively high power performance.

The Cornscala has the tweeter attenuated 3 db like a Cornwall. With a Khorn or Lascala which does not attenuate the tweeter at all, you would expect to hear a bit more noise.

By the way, this was all with DSP off. Just using it as an amp.

Bob Crites

Quoting myself here. This is the thing that has been chewing on me all day. If I can hear it, I should be able to measure it. The test I did for this was, volume adjusted to produce 1 watt then removed the input signal and looked at the output. My test equipment noise level is at about 90 db below 1 watt. I saw nothing above that noise level. Repeated that with gain adjusted for 10 watts. Still nothing.

OK, I heard some noise, but less than others report. I think Mark reported more noise than I heard. Is it possible that we all need to look upstream of the XTi 1000 to find the noise. I used probably less equipment than others and heard less noise.

What do you guys think?

Bob

[sfogg]

"If I can hear it, I should be able to measure it. The test I did for
this was, volume adjusted to produce 1 watt then removed the input
signal and looked at the output. My test equipment noise level is at
about 90 db below 1 watt. I saw nothing above that noise level.
Repeated that with gain adjusted for 10 watts. Still nothing. "

It
may be below the noise floor/range of your instrument. I ran into this
when working on the Teac's to lower their noise floor. They had a lot
of ultrasonic noise in them and the difference between that noise and
the audible noise floor hiss was a wider dynamic range then what my
SD-380 could handle. Keeping the ultrasonics below clipping the input
into the SD-380 resulted in the Teac's hiss being below the noise floor
of the SD-380. Trying to turn the signal level up to 'see' the hiss and
I'd clip the input and get all sorts of false readings. I ended up
measuring it on my computer which had more dynamic range then the
SD-380.

Shawn