jubilee

[sfogg]

Mark,

"Don't you think that if such a test were possible, every amplifier maker from Ajax to Zen would be showing those test results?"

No, they wouldn't. For the exact same reason most speaker manufacturers don't post a bunch of measurements on their speakers and employ smoothing..etc..etc. And differences in speakers are orders of magnitudes greater then between amps.

"At this point it is a true comedy that so many people claiming to be involved in music and music reproduction have not even a scintilla of appreciation for the application of subjectivity -"

Seriously, do you read what others write? I've said several times in this thread already that measurements don't determine taste.

Getting back to your original challenge...

"Ok, we have a listening room with two amps and a CD player. I have a stack of old Rolling Stones CDs here. Tell me how you will determine OBJECTIVELY which amp is more accurate at reproducing what was recorded by the Stones."

OBJECTIVE data about accuracy.... not subjective impressions... OBJECTIVE data...

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 2ohm output impedance feeding an 8 ohm resistor. Scale 0-2kHz.

First 30 seconds of Satisfaction.....

[sfogg]

Transfer function (input compared to output) of an amp with a roughly
2ohm output impedance feeding a '8 ohm' speaker. Scale 0-2kHz.

First 30 seconds of Satisfaction.....

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 0ohm output impedance feeding a '8 ohm' speaker. Scale 0-2kHz.

First 30 seconds of Satisfaction.....

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 2ohm output impedance feeding a '8 ohm' speaker. Scale 0-20kHz.

First 30 seconds of Satisfaction..... (drop off up high is because little content up there in the music)

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 0ohm output impedance feeding a '8 ohm' speaker. Scale 0-20kHz.

First 30 seconds of Satisfaction..... (drop off up high is because little content up there in the music)

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 2ohm output impedance feeding a '8 ohm' speaker. Scale 0-20kHz.

First 30 seconds of Roy's all music.....

[sfogg]

Transfer function (input compared to output) of an amp with a roughly 0ohm output impedance feeding a '8 ohm' speaker. Scale 0-20kHz.

First 30 seconds of Roy's all music.....

[Guest " "]

""Boy oh boy !!! what a bunch of loony squirts...Papa buys you the books sends you to school what do you do but eat the covers...""

that's almost name calling....thread is headed to be shut down....will we miss it...meant to say we will miss it...play on words...

[ZAKO]

Didnt Bob Carver do a transfer function of an amp???? I was mixing a movement from a Mahler Symphony ,,,listening intently to my superduper amp and monster speakers,,,, Then some one opened the door behind me walked in and placed there car keys on the table behind me... THAT was so real it unnerved me,,,So real that what was in front of me seemd like a carboard cutout.....Now that was a transfer function of great proportion,,,,A set of car keys sounded more real.

[ZAKO]

My reference to squirts ment we seem to be **hissing in the wind of a tornado on this subject...If we leave out the compairason of the LIVE factor...to the sound of that amp.

[sfogg]

".You cant observe the accuracy of the amps without compairing it to the origional LIVE source...That is the ultimate test..."

Not really since you then add in the inaccuracies of the speakers to the equation. If the inaccuracies of the amp compliment the inaccuracies of the speaker it could 'sound closer' then a more accurate amp.

To say nothing of the fact that the sound of some amps obviously changes depending upon the speaker it is connected to.

Objective accuracy of an amp is pretty simple to define... how accurate is the output of the amp compared to the input.

How that relates to ones subjective impression of the amp gets much harder, esp. when it is an amp that interacts with a speaker.

Shawn

[sfogg]

Mark,

Nothing that isn't already well understood... amps with higher output impedance interact with a speakers impedance. Which in turn alters the amps FR to make it less accurate. A sort of uncontrollable EQ which makes system matching more important since the same amp won't sound the same on different speakers.

Happens with test signals, happens when you play the Rolling Stones too.

Shawn

[DrWho]

What's fun about these discussions is that nobody can talk about measurements without being labelled as never listening to the music or appreciating the art or whatever. The beauty of data is it's a way to describe what you're hearing. I'd love for you guys to come hang out in the lab, where you'll find that the only time we use numbers is to quantify things we hear. Granted, sometimes we're way totally off by blaming the wrong things, but that's when you really start to learn what's going on. But if we choose to ignore measurements altogether, then I don't see how any understanding is to be gained.

Btw, notions of "accuracy" don't seem to be a topic of debate anywhere else in the electrical engineering world where amplifiers are being used. In fact, the impulse response absolutely describes the entire behavior perfectly. [] Understanding how to interpret it is another topic altogether. But for what it's worth, here's a log squared impulse response of the early behavior of our amplifer....anyone see any problems? (keep in mind that it's bandwidth limited to 24kHz since I'm using my computer's sound card).

(this was taken driving the Chorus II).

[DrWho]

"Didnt Bob Carver do a transfer function of an amp????"

-------------

Yes. 20 some years ago he would map the transfer function of any amp, like shawn has shown in the above, and add equalizers inside his amps to "duplicate" or mimic the the transfer function of another amp, thereby convincing some people the amps were the same. He had some success doing the trick. Not that many people buy his amps though.

Looking at the frequency response without the phase information is practically meaningless. There are all sorts of ways to make the frequency response flatter, but not all methods will ensure better behavior in the time or phase domains (like equalizers for example). That's where Nyquist spiral plots become handy and will quickly show the shortcomings of arbitrary EQ's...

[DrWho]

...amps with higher output impedance interact with a speakers impedance. Which in turn alters the amps FR to make it less accurate. A sort of uncontrollable EQ which makes system matching more important since the same amp won't sound the same on different speakers.

It's a bit more complicated than just that too. The output impedance of the amplifier will also have a reactive component that will also affect the transient behavior. The actual impedance of the speaker is always changing too. There is always the hypothetic perfect amplifier for driving the super complex load, or one can just simply lower the output impedance of the amplifier and keep the variability to a minimum.

I only mention it because the "problems" extend beyond the "frequency response", which so many people get hung up on. The way I like to think about it is the frequency response abberations resulting from the impedance interaction are representative of other problems that can be better seen in the time or phase domains.

[DrWho]

""Boy oh boy !!! what a bunch of loony squirts...Papa buys you the books sends you to school what do you do but eat the covers...""

that's almost name calling....thread is headed to be shut down....will we miss it...meant to say we will miss it...play on words...

lol, Maron doesn't know what he's missing out on. Them book covers taste great!

[DrWho]

Your SuperTECH1000 might be 0.0001% THD and XYZ tube amp might be 1% THD. You win. You have the more acccurate amp in that regard.

I do not agree with your conclusion considering the scenario you propose.

[6foot8]

Hey Roy,

I don't know that I have ever thanked you for those wonderful speakers you and Chuck worked so hard to get me. So I would like to do that now...Thanks! I Talk to and email Chuck frequently ant still owe him pictures of the completed room and set up from our last discussion a few months ago when the KPT 884 showed up. I use a complement of 3 BGWs for the Jubliees and a QSC 4050HD for the sub. I remeber reading somewhere that PWK had an affinity for one particular amp that is near and dear to my heart, the BGW 100. It was back in the early 1980s that I started using those amps, and Klipsch speakers, in part because of each products reputation. That was a very important factor for me in selecting the amplifiers I used for the speakers you designed...PWK's opinion of the BGW 100. I am certain that there are some other amps (both Tube and SS) that would sound better on some recordings and not as good on others but I like what I have and it sounds good to me. For me I think it was the opinion PWK had of that amp and the nostalic experience of going back in time for me that was the two biggest determining factors of my slection...and I think it sounds very good none the less.

I have played around with settings and balances, EQ...etc etc for a year and a half or so and found the "tune up" that sounds very good to me without contantly changing bass, treble or the balance between the amps between each song. And I admit that although I break out an "electronic measuring device" occaisionally the over riding factor is whats sounds good to my ears. And while I am sure there are purchases that I could make that would enable me to travel a little farther down that yellow brick road to audio nirvana, I have come to that place in the road where I am fully content. I think anything else would be just "different"...not necessary any better overall and most certainly not worth the added expense.

Thanks again!

[Guest " "]

6foot8

Nice combo.

How large of a room?

So you are active 3 way on the Jubs and active on the 884?

Are your 3 way Jub's stock?

884 xover frequency?