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Old 9th January 2003, 12:49 PM   #21
Previously: Kuei Yang Wang
 
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Default Re: So where is the audiophile direction in diy?

Hi,

Quote:

What solid state diy designs are suitable for audiophiles?
I suspect anything with a massively overbuild enclosure 1" thick Frontpanels, massive feathery heatsinks and so on. What's inside deas not matter at all, as Jeff Rowland demonstrates with a large line of electronics based on Chip Amplifiers (LM3886 & some TDA ones, plus various AD811 and AD797 in his preamps). For Audiophiles sonics don't really matter, it's all about status and image.

Typhical Audiophile Speakers and Amplifiers BY DESIGN maximise systemwide distortion and compression (up to 50% Distortion in the Amplifier & Speaker System and as much as 6db compression are not uncommon).

If you want the best suound go fo high efficiency speakers and valve amplifiers or maybe some of the really outrageous solid state ideas. But as long as you imitate the current High End industry your system will sound as unrealistic, stylised and unpleasant than what you buy in stores.

Sayonara.
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Old 9th January 2003, 01:40 PM   #22
AuroraB is offline AuroraB  Norway
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OOPSS ( swallow-swallow )
If external gadgetry is the definition of audiophile equipment, I think have to withdraw from this community....
The meters on the front panel of the X amps look quite cool though.........

I think we can all agree that it is the final SOUND that counts...almost only...
But the final sounding result is a close interactions of the various parts in the chain. This is truly a multifaceted community where each corner seems to advocate their own arguments...
In one corner there seems to be a common understanding that any amp weighing less than 200 lbs. is worthless... but if you want ( or need ) 200w true class A, that's probably what will be the result.. But why should you need 200 Watts?? 120 dB SPL hurts... but if your loudspeakers have the sensitivity a par with granite, that's what you need, --- at least !!!

In this view, I agree with the line of high sensitivity speakers and medium power amps, but horn loudspeakers are not really appreciated for their outstandig linearity and low distortion ?? (I must admit though, that after having heard the JBL Paragon back in 1970, I have always wanted to have a set of horns......maybe one of these days......)

It seems to me that the users of this board generally has one thing in common,- we are all fond of uncomplicated circuitry,- albeit for the price of bying a bucketload of transistors to select the 4 we will be using... Isn't that why Nelsons designs are so popular....besides for their reputation of sounding extremely well?? So- circuit complexity, or rather the lack of it , is probably one of our parameters....??
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Old 9th January 2003, 02:00 PM   #23
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Many audiophiles out there don't have a clue about electronics that's why many high-end firm can exist.... They can't judge if the product is worth the money or not. A nice case is a plus in this business...
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Old 9th January 2003, 02:10 PM   #24
Previously: Kuei Yang Wang
 
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Hi,

Quote:
OOPSS ( swallow-swallow )
If external gadgetry is the definition of audiophile equipment, I think have to withdraw from this community....
I was being deliberatly contrarian. Modern Audiophile gear tends to be however based on very pedestrian circuits and conceps (patent or not) and often more ingenuity is being shown in the metal work than in the circuitry.

Worse however is a fundamental, systematic design error. Speakers, or more precisely the force excerted on the cone or dome is proprtionally directly and solely to the current flow in the voice coil and the strength of the magnetic field within which the voicecoil is located (okay, and the length of the coil winding).

As in speakers the magnet field and voicecoil is a given (and unlike many better pro Speakers most so-called High Fidelity speakers have very uneven magnetic fields, causing strong signal modulation with voice coil position) the variable to drive the radiating surface of our speaker is the current.

Yet the current flowing through an iron filled coil (magnet pole piece) driven by a low impedance voltage source (common "High Fidelity" amplifier will be distorted according to a cubic function (called eddy current distortion), giving rise to odd (dissonant - unmusical) harmonics which rise drastically with power (increasing the power applied to the driver tenfold increases the distortion thousandfold!!!!).

Usually the level of eddy current distortion in common socalled High Fidelity drivers reaches parity with mechanical and magnet field nonlinearity caused distortion (these distortions BTW follow a quadratic function, cause even harmonics and will give a hundertfold increase in distortion for a tenfold increase in power and/or excursion) at around 1 Watt.

Really good moder Pro and Vintage Pro/HiFi Drivers (Tannoy, Altec, JBL Alnico et al) can absorb 10 - 50 Watt before the distortions reach parity AND offer usually a much higher efficiency, giving a MUCH lower distortion for a given SPL Level compared to modern "High Fidelity" drivers.

Another subject is thermal compression. As the applied power rises the voice coil heats up and the resistance of the copper, aluminum or silver coil goes up, as the voltage is not increased the current through the voice coil falls and thus the increase in SPL is less then the increase in applied Voltage. Compression levels of as much as 6db at rated power are not uncommon in Speaker Drivers.

Again, having a construction with a large vociecoil as found in older HiFi and modern Pro Drivers hepls to reduce the problem, equally, having a higher sensitivity wiil help reduce compression for a given SPL.

BTW, not once did I mention the word "Horn". You can make a high(ish) senitivity speaker using for example the Audax PR170M0 Midrange alligned to a good ribbon Tweeter (95db/2.83V/1m with a nice 8 ohm Load are fully possible) and add a suitable 15" Pro Audio woofer and build the result into a B&W Nautilus 801 Style box. It will not reach the N801's 20Hz LF cuttof, but anything in the 95 - 97db/2.83/m region, an easy load and a LF cutoff below 50Hz will be on the cards.

What has all that to do with Amplifiers you ask?

Well, if you where to make an active speaker you could make the amplifiers driving directly the voice coils behave as modulated current sources (output impedance approaches infinity). The loss of any mechgnical damping would likely mean you need to select drivers with a low Qm and operate them on an open baffle to reduce the system Q (an open baffle lowers the Q factor of the speaker system unlike sealed or reflex boxes or horns which increase it). But dipole woofers have a much better in room behaviour than monopole sspeakers so this is a bonus, not a penalty.

You could for example take the XP cone Seas 6.5" Coax and drive it from two "GainKlone" Chip Amplifiers operating in current mode on an open baffle. Add a suitable open baffle woofer (10" Peerless XLS) on the same baffle and another such driver in sealed mode to take over below the "critical" frequency of the room (usually around 30 - 40Hz).

You thus have a realtively easy to build and inexpensive Speaker/Amplifier combo that covers in room 20Hz-20KHz with pretty reasonable controlled directivity (Directivity Index 6db constant up to the point where the monopole tweeter takes over, rises then to around 10db) and I'm willing to bet my current stereo also a system that sounds much more real, dynamic, resolved and uncloured in your living room than most if not all of the common "High Fidelity" and "High End" stuff around.

So my real point was that if you want to "beat" storebought gear there is no point making the same fundamental mistakes that are designed into such gear. Think lateral and actually make something that works well in an electrical and acoustical sense AS A WHOLE SYSTEM. My own way are high senitivity speakers, Valve amp's and so on, but as discussed, I CAN imagine other ways to attain similar ends.

Sayonara
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Old 10th January 2003, 09:08 PM   #25
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Thanks for the replies. I have better info to now do a lot of research.

I see bringing up "audiophile" and "THD" caused quite a stir. Judging by the posts, everybody understood my point, but a heck of a lot of people still got on the soapbox. Fun stuff!
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Old 11th January 2003, 12:40 PM   #26
AuroraB is offline AuroraB  Norway
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Hehe

It is not often that I get up on the soapbox,-- but I had a rather frustrating day at work, where the cards fell down in the wrong order, so that I ended up doing very little productive work, because of no input from other projects..

Anyway.. THD is by all means an interesting subject, but I feel rather confident that it is not the actual figure or percentage that is interesting, rather than the actual looks of the distortion spectrum. Just look to the strong group of "Tube Dudes" out there, with their often fairly high content of 2nd and higher order even harmonics, which maybe isn't so bad after all......????

The reason for me stepping up in the definition of "audiophile" is that I think this subject has been brought into absurdum during the last years, with terms and definitions that often has little or no root at all in technology, and unfortunately too often by people with no teorethical or educational basis to support their claims.

I am sorry, but I still think that audio obeys to the rules of physics... I have no sense at all towards black magic
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Old 11th January 2003, 01:20 PM   #27
Previously: Kuei Yang Wang
 
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Hi,

Quote:


Just look to the strong group of "Tube Dudes" out there, with their often fairly high content of 2nd and higher order even harmonics, which maybe isn't so bad after all......????

Not only is it not BAD, used right it is actually GOOD.

Let's take a Tannoy Monitor Red Driver. At around 1 Watt applied and above 100Hz power you find the driver to have around 1% 2nd Harmonics and around 0.3% 3rd Harmonic (these values are broadly similar for all moving coil drivers at around 1 Watt). This happens in our case at an SPL of around 97db/1m or as stereo pair at 94db/3m in room, this a good mean SPL for large scale classical at realistic (concert hall) levels.

If we now take a 300B SE Amplifier which has around 1% 2nd Harmonics and 0.1% 3rd harmonics at 1 Watt output and we get polarity (phase) right (out of phase) between our 2nd harmonic contents we have made a SYSTEM that at 1 Watt has much less distortion than either Amplifier or Speaker on their own. We will likely have no more than around 0.3% 2nd and 3rd Harmonic for the given SPL.

If we now use a an Output transformer that is somewhat deficient in primary inductance our amplifier will increase it's 2nd harmonic content at lower frequencies, broadly the same way in fact our speaker does due to increasing excursion.

Driving the same speaker with a "distortion free" Amplifier (Mr. Selfs "Blameless Class B" or "Trimodal" Amp will readily suffice) will cause the system comprising amplifier and speaker to have much distortion DESPITE, or more precisely BECAUSE we made an amplifier with low distortion. Audio when done properly like with many a science tends to be highly counterintuitive, just as our case where removing distortion in one place causes the whole system to distort more.

Sayonara
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Old 11th January 2003, 01:40 PM   #28
SY is offline SY  United States
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Quote:
If we now take a 300B SE Amplifier which has around 1% 2nd Harmonics and 0.1% 3rd harmonics at 1 Watt output and we get polarity (phase) right (out of phase) between our 2nd harmonic contents we have made a SYSTEM that at 1 Watt has much less distortion than either Amplifier or Speaker on their own
I'd love to see actual measurements (rather than speculation and raw assertion) from just one system where this is true at more than one frequency and more than one SPL. I'm extremely skeptical that such a system exists, but can be convinced otherwise with some evidence. It sounds more like a rationalization of why someone chooses to build an amplifier whose output does not replicate its input, but has a "sound" which is pleasing to the builder (NB: there's nothing wrong with that as a design goal, it just ought to be admitted that that's what the design goal is!).

I note that this notion is put forth by the same people (not just KYW, I've seen this notion elsewhere) who tout the advantages of horns or other high-efficiency speakers because of their low distortion content, and who criticize push-pull topologies, despite their lower THD, because the even order distortion spectrum is cancelled! I'm unsure of how these two claims are mutually consistent, but again, I admit to having a very limited mind.
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Old 11th January 2003, 04:08 PM   #29
A'af is offline A'af  Indonesia
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Hi folk,

For about 15 years i try to find musical ecstacy with "big company" product and never got truly ecstacy, if i almost got it the tag priced make my spirit down, so now I involved in this forum, I'm never look intense in measuring performance, I'm only believe with my ears so the "simplicity", my result for best system are if they can reproduce sound can attack my heart (not my ear), coz this system almost make sound like truly infront of me and the system act "disappear" and make your body move, I look in High End arena and from 40 or more room just only 2 make me smile, one key to judge the system is bring your most hate record put it on and you take, at least fun, cause you see "sister of live performance" no matter is expensive or not, even in a boombox.

warm regards,


'Single Ended Single Driver Single Minded"
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Old 11th January 2003, 04:50 PM   #30
Previously: Kuei Yang Wang
 
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Hi,

Quote:


I'd love to see actual measurements (rather than speculation and raw assertion) from just one system where this is true at more than one frequency and more than one SPL.

Well, ignoring the "measurement" bit for a moment (we come back soon), if you study the sources of the distortion mechanisms in Speakers you will find several ones in which a square law function dominates.

The Triode Output stage follows a 2/3 square law, so it will not fully but only partially compensate. With Falling SPL both Speaker and SE Triode Amplifier decrease their THD following a similar function. This BTW is not true of most Push-Pull and Solid state amplifiers, here there is always a further distortion maxima at lower levels due to the uneven "handover" between devices, eliminated only in true class A PP/Solid State Amplifiers.

At a critical level (usually in the 1 - 3 Watt region with well matched systems) the canellation of distortion is maximised, above that The Amplifier distortion begins often to dominate the system, due to limited available output power. The result is low distortion at a wide range of levels.

Taking our example of Tannoy Monitor Red 15" Drivers with 94db/3m @ 1W RMS and a 10W RMS (< 5% THD) 300B SE Amplifier we find low distortion for average levels of 94db (< 0.5%) and moderate (probably around 2 - 4%) levels of distortion at average levels of 104db/3m. Higher peaks will be badly distorted, but the higher the SPL, the lower teh audibility of distortion.

Of course, as I pointed out in another thread, one can combine a low level Triode stage and a Chip Amplifier to achieve a similar behaviour, one does not "need" a 300B Triode Amplifier.

Now for measurements, by Eduardo de Lima taken from:

http://usuarios.uninet.com.br/~edelima/REASONS.htm#pt4

Click the image to open in full size.

fig. 1: speaker 2nd harmonic distortion with transistor amplifier. This amplifier has less than 0.05% 2nd harmonic distortion when driving this load.

Click the image to open in full size.

fig. 2: speaker 2nd harmonic distortion with SE amplifier. The SE amplifier has around 0.8% 2nd harmonic distortion when driving this load.

Click the image to open in full size.

fig. 3: speaker 2nd harmonic distortion with the same SE amplifier. The SE amplifier has around 0.8% 2nd harmonic distortion when driving this load. The polarity is inverted compared to figure 2.

Quote:


I'm extremely skeptical that such a system exists,

Suit yourself, I have one in my living room playing right now....

Quote:


It sounds more like a rationalization of why someone chooses to build an amplifier whose output does not replicate its input, but has a "sound" which is pleasing to the builder

Actually, it sounds to me that what you present is a rationalisation by someone who builds an amplifier that FORCES the attached speaker to give an acoustic output that does not replicate the input signal to the system (recording) to a much LARGER degree than neccesary and who blames the messenger for the message....

Quote:


I note that this notion is put forth by the same people (not just KYW, I've seen this notion elsewhere) who tout the advantages of horns or other high-efficiency speakers because of their low distortion content, and who criticize push-pull topologies, despite their lower THD, because the even order distortion spectrum is cancelled! I'm unsure of how these two claims are mutually consistent, but again, I admit to having a very limited mind.

It is clear that you have not really read anything of my comments on the subject.

1) High sensitivity speakers have a lower 2nd and 3rd Harmonics for a given SPL than low sensitivity speakers

2) Using the right type of high sensitivity speaker driver we find that at usable, semi realistic SPL Levels 2nd and even order Harmonics dominate the Distortion, lower sensitivity speakers tend to have 3rd and odd order harmonics dominant.

3) If we inject a suitable degree of suitably phased 2nd (and even) order harmonics ahead of the speaker we can reduce the distortion of the signal. This is hardly new and a similar application was found in the 1960's to 1980's in cutting records using a socalled "Tracing Simulator" (and no, Tracing Simulator usage was NOT limited to Dynagrove - it was universal in this period).

Thus, if we make an Amplifier that has a low output impoedance and very little 2nd (and even) order harmonic content in the output we maximise the distortion in the replay chain.

Of course, quite obviously there are folks around who very much like the sound of distortion and compression, I just happen not to be one of them, hence my use of Single Ended valve Amplifiers and High Senitivity Speakers, as such a system, competently and correctly implemented ensures materially lower distortion and compression than available from common "High Fidelity" and "High End" gear. And this is easily proven.

Of course, as long as everone thinks in their own little Box ("I make amplifiers that measure well into an 8 Ohm resistor" thinks the Amp guy, "I make speakers that measure well on axis in an anechonic chamber - Distortion - what is that?" thinks the speaker designer and so on) what we get is gear that measures well under limited conditions but is literally UNFIT for the stated purpose....

Too much certainty in measurements breeds mediocrity at best. Too many convictions make too many convicts.

Sayonara
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