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Old 3rd March 2013, 05:35 PM   #8531
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Hi ! are you sure your speakers have bad distortion figures ?
Anyway I am pretty sure that JBL speakers have very low distortion even at relatively high output level
Think of distortion like deformation of the shape of a signal .. this cannot be nice ... never
If you have measured high distortion with your speakers and still they sound nice .. I would be surprised
But maybe it is not the case
Regards,
gino
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Old 3rd March 2013, 09:32 PM   #8532
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One thing I speculated about was using DC offset to reduce distortion . The hypothesis being that when encountered it is due to the coil moving out of the magnetic field on the out phase of being driven . This could be controlled so as to never compromise the power handling ( over heating ) . My better idea was magnets in front and behind so as to have a more linear magnetic circuit . This is fine if a sub woofer . Old radios sometimes had a front mounted magnet to save space . If being really cute the magnet could serve a coaxial tweeter ( a bit of digital time delay to get it perfect ) .
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Old 4th March 2013, 06:03 AM   #8533
dvv is online now dvv  Serbia
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Quote:
Originally Posted by ginetto61 View Post
Hi ! are you sure your speakers have bad distortion figures ?
Anyway I am pretty sure that JBL speakers have very low distortion even at relatively high output level
Think of distortion like deformation of the shape of a signal .. this cannot be nice ... never
If you have measured high distortion with your speakers and still they sound nice .. I would be surprised
But maybe it is not the case
Regards,
gino
I am not sure, I assume it does from what a trusted friend has told me about the drivers. Not that I care, mind you, so long as it continues to please my ears.

Obviously, at least a part of the fun was the fact that the speaker was my idea, which I outlined to friend at the time professionally involved in speakers, and from there on, we developed it together. It took six months or so to get it just right, but we did it. Sadly, for personal reasons, he gave up his loudpeaker manufacturing career, so his company (B&M Acoustics) no longer exists. And just when it started selling ...

However, I am reasonably certain that it IS a very good speaker from comments made by my friends and acquaintances, some of whom don't even know the others, and who range from hard core tube, via hard core BJT to hard core MOSFET lovers.

As you can see, I live in a terrorist environment, EVERYBODY is hard core.
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Old 4th March 2013, 08:03 AM   #8534
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I once asked someone why we ask RIAA to be correct to +/- 0.05 dB when the cartridge is +/- 3 dB if very lucky . He said because we should get right what we can .

I have long said if an amplifier has less than 0.1% distrotion and looks for all the world like a class A design then it is hi fi . Better still the distortion harmonics reduce on a exponential graph which is similar at all signal levels . I built about 2 years ago an amp that was generally exactly that and would go right down to noise giving the same spec . It could offer 5 watts in class A and plenty more into class AB . For what it is worth I feel that mostly class AB sounds better than class A especailly if the first 5 watts are in class A . The reason being the class A amps are very demanding in the power supply dept . Equally many people fit under sized PSU's if class B as the hum is not obvious on idle . It modulates the music regardless of CMRR . 2 x 22 000 uF / 100 W / Ch I think we said as a minimum ? Some very good amps sound a bit bland and overly controlled when too many cheap uF are used . We called them muscle bound . At low levels sometimes not enough capacitance sounds good , soft and very open ( 2 x 3 300 uF perhaps ) . I would be tempted to have it switchable . Also as Yamaha we can arrange the PSU as half voltage 4 x capacitance class A , or full voltage class B .

I recently uprated my old Armstrong receiver . Not because I wanted to , just there was a special offer on caps and the old one was dying . I forget the exact change , I remember it to be about 50% more . It was cheaper also to go higher and has a 20 V safety margin now . It is very hard to say exactly what has changed . The sound is more modern and tighter . Mostly it is better , however it is not exactly an Armstrong now . A bit like cleaning a painting .

I was asked at the Bristol hi fi show how anyone starts to design an amplifier . Easy I said . Ask my boss the budget .Then buy the largest heat sink I can . Buy the best PSU I can . Then the less important bit , the circuit . He then said why are so many designs so complex ? I said it is to intimidate . I thought about it as I drove home and thought I would not change a word of that . The guy imports LAB 47 which pleased me . The only reason I am not happy with chip amps is that the bias tends to be a little bit less than optimum for very good reasons ( thermal ) . An analogy would be push-rod engines . There comes a time when it matters .

http://www.6moons.com/audioreviews/4.../gaincard.html

Last edited by nigel pearson; 4th March 2013 at 08:13 AM.
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Old 4th March 2013, 12:29 PM   #8535
dvv is online now dvv  Serbia
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Actually, to be precise, 2*22,000 uF/channel was what John told me when I asked what would he consider to be the minimum capacitance for an amp aiming for the stars.

I believe him to be right, with just one note - I would prefer caps in parallel, but wuld still end up thereabouts.
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Old 4th March 2013, 05:26 PM   #8536
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Quote:
Originally Posted by nigel pearson View Post
I once asked someone why we ask RIAA to be correct to +/- 0.05 dB when the cartridge is +/- 3 dB if very lucky . He said because we should get right what we can.
I have long said if an amplifier has less than 0.1% distrotion and looks for all the world like a class A design then it is hi fi . Better still the distortion harmonics reduce on a exponential graph which is similar at all signal levels . I built about 2 years ago an amp that was generally exactly that and would go right down to noise giving the same spec . It could offer 5 watts in class A and plenty more into class AB . For what it is worth I feel that mostly class AB sounds better than class A especailly if the first 5 watts are in class A
This is a good sounding amp ...

Click the image to open in full size.

so some amount of distortion is not a limiting factor I suppose

Quote:
The reason being the class A amps are very demanding in the power supply dept . Equally many people fit under sized PSU's if class B as the hum is not obvious on idle . It modulates the music regardless of CMRR . 2 x 22 000 uF / 100 W / Ch I think we said as a minimum ? Some very good amps sound a bit bland and overly controlled when too many cheap uF are used . We called them muscle bound . At low levels sometimes not enough capacitance sounds good , soft and very open ( 2 x 3 300 uF perhaps ) . I would be tempted to have it switchable . Also as Yamaha we can arrange the PSU as half voltage 4 x capacitance class A , or full voltage class B .
I recently uprated my old Armstrong receiver . Not because I wanted to , just there was a special offer on caps and the old one was dying . I forget the exact change , I remember it to be about 50% more . It was cheaper also to go higher and has a 20 V safety margin now . It is very hard to say exactly what has changed . The sound is more modern and tighter . Mostly it is better , however it is not exactly an Armstrong now . A bit like cleaning a painting .
I also did something of similar as an experiment
The original amp had 2 very nice Sprague of 6800 uF
After reading of the cap upgrading I decided to try
Being completely ignorant I did not know which value to use
So just to be on the safe side I tried two nos Mallory of about 60.000uF
with a new 40A bridge
The new caps were so big that did not fit inside the amp chassis (I left them outside just to try)
The result was so astonishing that I would recap heavily any amp I have
But the manufacturers, that are not stupid, leave very little space for bigger caps ... this is done intentionally ... I think
The PS caps are like the lungs for a runner
And computer/industrial grade caps are so much better than the average caps in mid hifi
Of course if you open a ML you will find the computer grade ones

Quote:
I was asked at the Bristol hi fi show how anyone starts to design an amplifier . Easy I said . Ask my boss the budget .Then buy the largest heat sink I can . Buy the best PSU I can .
Then the less important bit , the circuit . He then said why are so many designs so complex ? I said it is to intimidate . I thought about it as I drove home and thought I would not change a word of that . The guy imports LAB 47 which pleased me . The only reason I am not happy with chip amps is that the bias tends to be a little bit less than optimum for very good reasons ( thermal ) . An analogy would be push-rod engines . There comes a time when it matters .
6moons audio reviews: 47 Laboratory Model 4706 GainCard
if you need current delivery maybe a chip amp is not the best solution even if a famous brand paralleled some of them
Now there are class d and SPS pushing strong
Someone says that the latest offerings are good
Maybe we are at the dawn of a revolution ?
By the way I love big caps ... and the nos ones are also very very cheap
A tester is needed I suppose
But any amp benefits from a cap upgrade
Thanks for the very kind and valuable directions
Kind regards,
gino

Last edited by ginetto61; 4th March 2013 at 05:30 PM.
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Old 4th March 2013, 08:14 PM   #8537
DF96 is offline DF96  England
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Quote:
Originally Posted by ginetto61
This is a good sounding amp ...
It appears to have 15% 2nd and perhaps 5% 3rd (which means similar levels of IM). At 1.6W I can only assume this is some sort of joke. Have you shown the wrong plot?
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Old 4th March 2013, 08:40 PM   #8538
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Maybe you like better this graph ?

Click the image to open in full size.

this is the link to the tests

Jadis SE300B monoblock amplifier Measurements | Stereophile.com

I would like to add a consideration
Usually this kind of amps are tested with "easy" speakers
So maybe the good overall performance is due to the speakers ?
Regards,
gino

Last edited by ginetto61; 4th March 2013 at 09:08 PM.
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Old 5th March 2013, 11:39 AM   #8539
DF96 is offline DF96  England
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So appallingly high distortion at quite low power and lumpy restricted frequency response provides 'good overall performance'? It seems to me that this is the old idea of 'tone' (as found in wireless sets and radiograms 60 years ago) being revived. Sometimes known as 'euphonic distortion'. Sadly, sometimes called 'high end'. Nothing whatsover to do with hi-fi.
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Old 5th March 2013, 11:49 AM   #8540
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Agree with Dave, but it doesn't answer the question why in this case, like for example with the WAVAC, the distortion is euphonic. Because usually, gear with such distortion figures would sound plain horrible. What could explain this?
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