Sound Quality Vs. Measurements

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Scott,



What I find interesting in that are a few things.

First numbers are thrown around without any reference level and context.

Without being specific about SPL's involved, frequencies etc. the number alone is meaningless.

Second, instead of a sensible fair use quote something totally different is said instead:


What must be realised is that the adjustment referred to is not a 2nd harmonic adder, but rather adjusts the overall distortion profile of the Amplifier, plus it even affects overall gain if adjusted enough.

So I would expect P3 adjustment to be audible, but not because 0.1% 2nd HD are reduced (or not), but because of other effects it has.

Ciao T

If you choose to think "definately alters the sound" and "things going on below 0.1% are audible" are totally misconstrued by my interpretation so be it. And I did say null not add. This is not the first time he has mentioned it, his amplifiers usually have mostly only low order 2nd's and 3rd's and he has attributed their characteristic "sound" to the relative 2nd's to 3rd's ratio.

The trim would usually add large amounts of inbalance before hitting the stops, I don't see much change in gain for any resonable amount of trim.
 
diyAudio Member RIP
Joined 2005
I could not get to trigger or see anything that looked like ringing after the cutoff. Just random noise.

Current probes are helpful. Sometimes in lieu of that I make a little pickup coil with low-enough inductance to be fast and try to "sniff out" the really high-frequency energy that may be emitted, and which can propagate.

As someone mentioned earlier, the simplest snubbers don't so much snub as they lower the frequency of the ringing, which makes it less likely to propagate.

This thread is long and meandering enough as it is, but someday I will tell the story of the most nearly-disasterous problem with a powered speaker I've had to date. It involved a ceramic cap that was installed in anticipation of the need, with ultra-cheap rectifier diodes, to sometimes need to suppress switching spikes that would have potentially introduced a low-level buzz in the audio. The double failure mode of capacitor and a.c. adapter almost started a fire in a college dormitory room. Had flammable material been nearby it could well have led to fatalities. :eek:
 
In the post #2493 you write the same, but using more literature language, regarding some certain opamp-style topology, while my answer is more common and precise. In your example resistors loading stages with high output resistance are viewed by the next stage as part of output resistance of the previous one. Balancing such a way power amplification between stages you optimize the whole amp.

Now, THAT'S an answer I wanted to read - thank you!
 
Wife said no. Too big for the living room. No to the Sequals, No to the Vandersteins. I should have made the switch when I still had the old Ditton 44's. Now it is small monitors or else.

Serves you right.

Whatever possessed you to change those Dittons? Couldn't you just refresh them, perhaps used still better quality caps, and so forth?

Now you are forver damned to not hearing the bottom octaves. :rolleyes:

You might want to try bribery - it worked for me. I told my wife that she loved calssical music so much, it was only right that she should have her own system. So I got her an H/K 680 integrated, a pair of JBL Ti 600 floorstanders which fit in PERFERCTLY in her room, and, in the name of sane economy, a Sony CD/DVD player. Oh man, is she happy, or what!

She was so happy that I was moved to plonk down some serious bread for a pair of serious van den Hul speaker cables.

HiFi bonus, pax in domus. :D :D :D
 
Went looking for the rectifier ringing in the DH120 so I could select proper snubber values. After all, the datasheet for hexfreds say "reduced snubbers" not none. It does not even have the original disk across it.
Hmmm. No ringing. A bit of general noise that is probe cable sensitive, that's all.

OK , are you still going to add snubbers..? did you match your hexfreds ...?

in contrast to a Rotel 951 with conventional rectifier, cap only snubbers.

So conventional block with snubbers , any thoughts on how this affects the sound vs the hexfreds ...?

5 mV, .5mS. on the Rotel, 10mV on the Hafler at I think 1ms. I don't have a storage scope, so getting a single shot is not possible. What it does show is the glitch on the conventional supply. It was less stable to trigger on as well. You might have noticed.

Interesting ....
 
Serves you right.

Whatever possessed you to change those Dittons? Couldn't you just refresh them, perhaps used still better quality caps, and so forth?

Now you are forver damned to not hearing the bottom octaves. :rolleyes:

You might want to try bribery - it worked for me. I told my wife that she loved calssical music so much, it was only right that she should have her own system. So I got her an H/K 680 integrated, a pair of JBL Ti 600 floorstanders which fit in PERFERCTLY in her room, and, in the name of sane economy, a Sony CD/DVD player. Oh man, is she happy, or what!

She was so happy that I was moved to plonk down some serious bread for a pair of serious van den Hul speaker cables.

HiFi bonus, pax in domus. :D :D :D

Ah, but I built a pair of 12" peerless subs, proper electronic crossover etc. Yea, 44's sure did have a nice bottom end. I had to replace the T-2000's years ago with some Seas units. A tad smoother with no crossover change. A friend of mine is still using them with an Acrus amp. Pretty sweet. The cabinets are not up to what I build now, and 40 years have improved driver technology. It would be fun to put in a modern tweeter and rework the crossover. The mid was pretty good too, but they used it too high.
 
Then build them , what are you currently using ....?

I am building them. I was working on another set when I got distracted by amp design. I was in the middle of a tweeter bake off. I have just about convinced myself that regardless of measurements, I don't like metal domes. Waffling between a Seas Excel or ScanSpeak Revealtors with soft domes. This time I am stepping up the driver budget because I think I know just enough to get some value out of them.

Right now, the living room has first generation Paradigm studio 20's with my own Peerless subs. I have some Kef Q1's in my office, and several pairs I have built I swap in and out of my guest room where I do my serious evaluations. Mostly Seas/Vifa/Dayton based. I really need to get the Q1's out of here. I have done better. I have a pair of slightly modified Tanburgs on my desk. Old and comfortable like well worn shoes. Another project in the works was a set of very narrow towers I priced someone. The narrow baffle is causing me bigger issues than I thought. They are based on the Zaph driver and a Seas metal dome, 6th order effective. Crossover is getting expensive. That is how I decided a more expensive tweeter is easier to use and the crossover savings can pay for the tweeter. Same on the mid. $50 drivers are more expensive to use than $100 drivers.
 
OK , are you still going to add snubbers..? did you match your hexfreds ...?



So conventional block with snubbers , any thoughts on how this affects the sound vs the hexfreds ...?



Interesting ....

Sound? Well I like both amps, but my wife's super ears did not like the Hafler stock. I doubt the power supply is the main reason, but it is one step. I have a list of changes I plan to make, IPS degeneration and changing the dominant pole to Miller comp. I was using it as my bench amp and wanted to reduce residual distortion. It measured 8 to 13 dB better, so that was a success. Then I got carried away. We have been under the weathers so not in a mood for critical listening.
 
Hi,

Went looking for the rectifier ringing in the DH120 so I could select proper snubber values. After all, the datasheet for hexfreds say "reduced snubbers" not none. It does not even have the original disk across it.
Hmmm. No ringing. A bit of general noise that is probe cable sensitive, that's all.

Look at the transfomrer secondary, secondary current, diode current and output...

Ciao T
 
Just fed some sine waves through my speakers, and to my consternation found that one tweeter was generating an audibly raspy overtone on anything above a certain very low level. It was a bit intermittent, and prodding it about a bit I managed to improve it, but it's obviously not long for this world, and must have been sounding terrible, although impossible to pin it down when listening to real music in stereo.

I've recently worried about the sound of my system, but I was thinking more along the lines of amplifier, PC sound card (for that is the source), passive 'pre-amp' etc. The speakers were supposed to be the one thing I could rely on without question. It occurs to me that the average hi fi buff could spend his life savings trying to improve the sound of his system, but might never play some sine waves through it and listen to the result - a mixture of measurement and listening for 'sound quality'.
 
Hi,

Just fed some sine waves through my speakers, and to my consternation found that one tweeter was generating an audibly raspy overtone on anything above a certain very low level.

Murphy's "High End Audio Speaker Law"

"The Loudspeaker is the last chance of the system to add colorations, distortions or otherwise make high fidelity impossible, hence speakers will usually be defective right out of the box and disintegrate into Twitter, Squeaker and Wuffer at the least provocations. Often crossovers are added to increase the likely-hood of creating audible errors and defects."

Depending upon your tweeter it could be a bad solder-join on the Alu Voice Coil Wire to leadouts, or if they used the voicecoil leadouts from there to the tags. Usually repairable.

It could also be dried out ferrofluid (if you or speaker manufacturer where daft enough to specify using this stuff to save a few bucks) this too is repairable, but often it is better to just remove that stuff and add the necessary LCR trap to the crossover.

Finally it could be a fried or distorted voice coil, especially if you play loud a lot and your amp's don't clip nicely. In this case it needs a recone/repair kit, or a new tweeter if it is not intended for field repairs. If you repair one tweeter it is probably a good idea to repair both, often the units change slightly in production with time and an "old" and a "repaired"unit unit suddenly measure quite different.

Ciao T
 
Objective subjectivity??:scratch2:

Yes. The notion of objective vs subjective is totally false. A truer dichotomy is controlled vs uncontrolled.

The IEC protocols are highly useful for answering certain types of questions, less so for others. Like any other standard test methods, they provide useful guidance and a good baseline, but should not be used as a Procrustean bed.
 
Hi,

Yes. The notion of objective vs subjective is totally false. A truer dichotomy is controlled vs uncontrolled.

No, controlled/uncontrolled is a tiny aspect of this, which some would like to turn into a major in itself, when at best it is a sideshow.

Objective implies in the context that primary consideration is given to measurements, that is something does not measure well (in an extremely limited set of tests) it MUST sound bad and the reverse and where no differences are measured (by an extremely limited set of tests) then no audible differences MUST exist. It should be noted that measurements in themselves are not controlled and may be deliberately or unintentionally made to give incorrect indications.

Subjective implies in the context that primary consideration is given to listening impressions, that is something does not sound well (even if it measures well in an extremely limited set of tests) it MUST be bad and the reverse and where audible differences are heard (even no differences are measured by an extremely limited set of tests) then audible differences MUST exist. It should be noted that listening tests in themselves are not controlled and may be deliberately or unintentionally made to give incorrect indications.

Suitable controls and repetitions are needed if we want to ensure that the tests give results that are repeatable and can be generalised, which is where statistics and other issues come in.

However, for example a controlled test that is myopically controlled only to avoid (false) positives and uses extremely poor instrumentation has very little claim to offer anything that can be generalised, even though it is a controlled test, while an uncontrolled test with exceptionally good instrumentation also has no good claim.

The IEC protocols are highly useful for answering certain types of questions, less so for others. Like any other standard test methods, they provide useful guidance and a good baseline, but should not be used as a Procrustean bed.

I made no reference to anything from the IEC. The things I linked are from the European Broadcast Union (EBU) which may be seen as the European AES, with higher standards of evidence and relate to the "instrumentation" of subjective tests. They do not address controls, only how such tests should be conducted in terms of environment, design of questionnaires and data collected.

Controls are a completely separate issue.

Ciao T
 
My apologies- I said IEC when I meant EBU. Perhaps if I'd had one less cup o coffee, I would have typed "ASTM." But same comment applies to all the alphabet soup standards and recommendations.

In any case, controlled listening is the sine qua non of objective evaluation of subjective aural perception and/or preference. How one overall enjoys having something in one's living room is a separate matter.
 
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