"But to pass the time you read this magazine? 'S full of graphics." So I said vaguely surprised and shocked my daughter long ago, thumbed out of curiosity after a hi-fi magazine that I had left around the house. Indeed, the magazines High Fidelity "traditional" publishing has always instrumental tests Hi-Fi components, testing that should allow an objective assessment of the value of the components themselves.
manufacturers raced to get out more and better products with instrumental measurements, distortion more basse, risposte in frequenza sempre più estese, fluttuazioni inesistenti, e così via.
Tutto è continuato così, salvo per pochi carbonari che già contestavano questa idea di misurare tutto, sino all'arrivo del CD e ai suoi effetti collaterali imprevisti. Il CD tecnicamente perfetto, con risposta in frequenza perfetta, rispetto al giradischi, con rapporto segnale / rumore più esteso di quello di una sala da concerto con spettatori muti ed immobili, con distorsione inferiore al fondo scala degli strumenti di misura. E però qualcosa non andava all'ascolto.
E in parallelo, come reazione alla perfezione raggiunta solo sulla carta (millimetrata), si andavano affermando due categorie di items that were in total contradiction with the results of measurements: the mini-tube amplifiers and speakers. Soon he returned again and also vinyl, also preferred by fans to the designated successor of CD, Super Audio CD (or SACD).
In all these cases the distance in terms of measurement results between a tube amplifier and a state pay for equal power (but also less power), including a mini-speaker and a speaker to three or more routes, a turntable and a CD player, was abysmal.
Yet listen a growing number of enthusiasts prefer them. At first a few, wealthy, and esoteric. Then more and more, until now no one except a few hardcore positivists to the bitter end, he questions the musical quality of a tube amp or a good vinyl played on a turntable.
So if you are unable to discern between these glaring differences, what you need measurements?
depth on a bit ', without embarking on talks too technical, and hoping not to make excessive simplifications, helping us with some examples. Using some recent evidence from the magazine Audio Review (AR), the leading sector in Italy. Let me be clear, I state now that all the tests are conducted in a fully rigorous and that my comments are in no way directed to discuss his findings. These are just examples, taken from an authoritative journal in support of the observations and reflections that I propose.
start from the amplifiers
All electronic (and electrical), the component should be easily measurable. And indeed that is where they were tested several types of tests.
The first fact is the power that is detected. But in modern amplifiers (and in modern houses) is very unlikely to be sufficient. This information is required to classify the object, a bit 'as the capacity for cars. Then you need to focus on power quality. To measure AR (and before Suono) ha sviluppato una misura di sintesi molto efficace, un insieme di test, loro esclusivo, che hanno chiamato "tritim".
Osservando che la musica non è lineare, quindi non è un carico solo resistivo (come quello usato per misurare la potenza convenzionale) questo complesso test traccia la risposta dell'amplificatore per carico induttivo e capacitivo, al crescere della potenza. La sto facendo già troppo complicata, me ne rendo conto, e passo quindi a mostrare il grafico in questione. Che già spiega tutto o quasi.
Come si intuisce la risposta ideale dovrebbe presentare dei picchi e delle linee senza incertezze, sia nella zona nera (dove l'amplificatore lavora nelle condizioni ottimali, o "di targa") sia nella zona rossa (al di fuori). Le alterazioni indicano la "non linearità" rispetto alla situazione teorica ottimale, e quindi la possibile origine di difficoltà di pilotaggio delle casse e quindi di imperfezioni nel suono.
Il grafico mostrato è relativo ad un amplificatore a stato solido di buona qualità, provato con esito molto positivo dalla rivista, il NAD C316BEE , ma molto economico (costa meno di 500 €).
Come si vede i grafici sono praticamente perfetti in zona nera e buoni anche in zona rossa, con qualche imperfezione. Valori abbastanza buoni? Scarsi? Lo vediamo dopo.
Per intanto ci concentriamo on another important fact: distortion. As you can see from this other chart, always of NAD, the trend of the distortion is measured as the volume increases until the maximum power (around 80W in this case).
As you can see is always less than 0.1% up to maximum power, which rises in a net. Indeed, decreases steadily as the volume increases, up to 0.01%, reflecting, as it said the magazine, the system of counter-reaction to reduce the distortion that this amp (as most models) apply.
An amplifier tube instead how are you?
To see if these measures can effectively explain the very good feedback from that 'of this new product Nad try to compare it with a well-known tube amp. The choice fell on a very nice product from the German technical point of view, the T + A V10 .
And now we have a few surprises. Meanwhile tritim
curve in this case is not there. As with all tests of tube amps or so. The fact is that, for the inherent characteristics of electronic tubes, this type of measurement is difficult to apply, should always be out of scale, and also where would you respond to significant distortions. Worse than worst transistor amp, so to speak.
We leave this question for air and find another comparable measure: the distortion.
Here the curve is different, then go back down, but it is consistently above 0.1%, to reach close to 0.4% at -10 dB (high volume, but possible). So many times more than the NAD, which costs a tenth of this popular integrated valves.
Perhaps those tube amps and transistor just can not be compared.
Let us try to compare our Nad with another solid state amplifier, the integrated McIntosh MA-6600 , provato nello stesso numero. Cominciamo con la curva di tritim:
Non è molto migliore, anzi la risposta lineare si ferma prima. Certo, c'è che da considerare che è molto più potente (150W contro 88W, in regime impulsivo su 8Ohm) e che quindi la zona lineare in termini di potenza si estende di più. Bisogna tener conto però che il McIntosh costa oltre 20 volte di più del piccolo Nad, e quindi che abbia più potenza sia comprensibile. Fino a dove la potenza di targa è sufficiente (con 88W si sonorizza tranquillamente qualsiasi ambiente domestico normale) il comportamento dei due integrati a questa misura, abbastanza impegnativa da mettere in crisi gli amplificatori di qualche anno fa, è praticamente identico, anzi è di un filo più lineare per il Nad. Veniamo allora alla distorsione.
E anche in questo caso il comportamento è molto simile. Sempre sotto allo 0.1%, scende fino a che il volume raggiunge il massimo, poi sale velocemente, e viene limitata da un apposito circuito anti-clipping può deciso di quello del Nad. Ma siamo nella situazione di volume al massimo con un amplificatore da oltre 150W, i vicini hanno già chiamato i pompieri o è il proprietario che si sta lanciando sul volume rimasto ruotato al massimo per errore per salvare i poveri altoparlanti. Non una situazione di ascolto reale.
Notiamo solo. come ultima cosa, che anche la curva del McIntosh mostra chiaramente il ricorso alla controreazione (che ultimamente non è molto popolare tra gli audiofili) ma il recensore di AR in questo caso, a differenza che per il Nad, sorvola su questa osservazione.
E le casse come vanno?
Un'altra misura che negli ampli dice poco, e che era la misura principe agli albori dell'alta fedeltà, è la risposta in frequenza. Come restituisce il suono in ingresso il nostro amplificatore al variare della frequenza? Se fosse ideale dovrebbe fare questo mestiere sempre allo stesso modo per tutta la gamma udibile, then from 16Hz to 20KHz (for those who come to hear them). In other words, this measure should show a perfect straight line 16 (or 20) Hz up to 20 (or 16) KHz. Let's see how are the Nad and McIntosh.
Nad's response (above) is almost linear with only a slight attenuation at 20 Hz for both, a bit 'more remarkable for the McIntosh (even at 20KHz in this case), in the figure below (both the lyrics are at 2.83 V at 8 Ohms).
The sound, however, comes from the speakers, so let's see if this behavior as linear through this too fundamental component and get it safely to our ears. We know that this is the most critical component Hi-Fi, and then we do not take such a budget speaker. We take the best model of the famous English manufacturer Monitor Audio (cost more than € 6500) and see how it goes.
A party that starts a lot later, at 40-50 Hz, to become linear, then presents a number of oscillations, amplitude approximately + or - 3dB (warning).
But because this model has failed badly, in fact is a speaker of high quality, but because physical limitations you can not do much more. There are more linear speakers (studio monitors for example) but the curve has always oscillations, although perhaps within 2dB or less.
The point is another: if the sound output is so altered (while remaining, as we know, appreciate) how do we perceive any alteration of one or two orders of magnitude lower, the upstream component?
Let the distortion . For speakers measuring the intermodulation distortion, so the comparison is probably a bit 'forced, but the chart that we show more ...
... we see that we are at much higher levels, at different frequencies and harmonics can also be reached at 1%, 5 times or more that of the amp, tube or transistor to be. The same holds true: this rate of distortion should be able to mask any differences in the upstream component.
We then discovered that components do not retain what they promise? The
McIntosh, despite the price, that is like a Nad? The tube amps are a collective hallucination? No way, anyone who has tried them judges them much higher, and I think that would exceed even objective tests in double blind. And McIntosh is superior to the NAD (which is worth 20 times that the judge who thinks to buy):
The fact is that the superiority of listening, the renowned musicality and transparency are talking about usually reviewers, clearly depends on other factors, for which there are no measures that can be used, or the measures are too complex to set up and run nperché involve many parameters.
This is why some magazines have abandoned the high-fidelity measures since the 90s (and AR public by that time also the section AudioClub, with trials without measurement) and judge the music machines just by listening.
Therefore, measures should help or not?
To select a component or another, as they did in the '70s, I would say not. To choose a component without going through the listening phase, not really. To learn more about how it's done in a component, for those interested, yes, may be useful. But certainly not essential. Welcome then, magazines with only listening tests.
To compare in an objective way the components and choose the best components the only objective system but is, in our humble opinion, the double-blind test, of whom we spoke at the time and on which we shall return.
(The graphs are taken from the magazine Audio Review, numbers 316, 303 and 244, as anticipated in the text of the article, absolutely partial extractions are used only as an example of measurements taken from magazines specialist Hi-Fi, full articles, for those interested, I read the magazine, to get back issues to read the signs in the magazine or on the same site. The hi-fi shows is the Rogers LS3-5A, a case developed for other purposes, to monitor the mobile studios of the BBC, which has become the initiator of the mini-speakers that have dominated the market of hi-fi in the '90s).
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