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Exploring the pros and cons of warming up audio equipment
Exploring the pros and cons of warming up audio equipment
Exploring the pros and cons of warming up audio equipment

Speakers

Warming up audio equipment: Advantages and disadvantages

Engaging in subjective testing of audio equipment has made me acutely aware of the importance of the warm-up phase. It’s common to hear colleagues say things like, “We let the system warm up for 24 hours before we start listening,” or “This setup was taken straight from the box without any warm-up, so I can’t make any definitive judgments based on my initial listening.” On the other hand, some people dismiss the need for warming up as nothing more than a marketing ploy.

The reality likely lies somewhere in between these viewpoints. For those who have been using the same audio setup for years, the warm-up phase is a non-issue since it has already occurred. However, when a brand-new device doesn’t deliver during the first twenty minutes of use, it raises questions about the warm-up process.

Let’s explore this further. The first question we need to tackle is: what exactly do we mean by warming up? An audio system, even a compact all-in-one unit, is made up of various components. It’s unlikely that the warm-up time and conditions will be the same for cables, speakers, and amplifiers. In fact, even within passive circuits and different types of semiconductor components, the warm-up needs, if they exist, are probably quite different.

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In English, the term “warm-up” is often replaced with “break-in.” This idea can be easily understood through the analogy of a car, which also requires a break-in period. A new vehicle needs time for its piston rings, valves, brake pads, shock absorbers, and other parts to adjust and wear in properly. This process is somewhat similar to how various audio components function.

Speakers

We should specifically focus on all contemporary sound sources. With the possible exception of ionophones, which involve the pulsation of ionized gas, all these sources demonstrate cyclic deformations in the bending of components within the moving system, such as diffuser suspensions and sections of flat or pleated membranes.

Let us begin with the diffusers. Typically, we are referring to the deformations of both the external and internal suspension systems, particularly the centering washer. Regardless of the materials used, which are generally polymers or composites, these structures consist of long molecules—most commonly fibers—bonded together with a binder and occasionally treated with a plastic composition through processes such as coating or gluing.

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Speakers

It is evident that cyclic deformations alter the characteristics of such structures, leading to a weakening of internal connections and resulting in a more flexible configuration. Since components of moving systems, like speakers, are often assembled under pressure, this process inevitably introduces internal mechanical stresses. Over time, these stresses are effectively mitigated by the cyclic deformations.

The outcomes of sound measurements from speakers are quite logical, indicating that warming up leads to a 15% increase in amplitude while the frequency range remains constant. Unfortunately, there is a lack of more comprehensive data… How did the frequency response evolve? I am skeptical that its shape stayed the same. This raises a critical question: what do these 15% signify for the average listener? Even a doubling of amplitude, which corresponds to a sound pressure change of about 3 dB, may go unnoticed by many. In this context, who will be able to perceive these 15% audibly?

The process is significantly influenced by the load on the speakers, the amplifier power applied (expressed as a percentage of the maximum), and the frequency spectrum of the music signal. It is well understood that under substantial power, the “voice” coils of the speakers can heat up considerably. In multi-band systems, and even in broadband systems for slightly different reasons, the extent of heating is contingent upon the music signal’s spectrum. For instance, white noise tends to heat the speaker uniformly to its operational state.

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When a testing specialist notes that the sound changed during the warming up of the acoustics, it raises the question of whether this was a genuine “run-in” or merely a result of the speakers heating up—essentially an increase in the temperature of their components during use. The coil heats up almost immediately, but the larger magnetic system may take significantly longer to reach a similar temperature, potentially exceeding the duration of one or two test tracks. It is worth recalling that speakers can fail similarly to traditional incandescent bulbs.

With such temperature fluctuations, referred to as non-stationary by thermophysicists, the impedance, magnetic field characteristics, and mechanical properties of all speaker components are altered. Therefore, to accurately assess the sound of the speakers, it is essential to allow them sufficient time to operate at a volume near maximum, enabling them to reach their optimal temperature.

Speakers 2

Additionally, there is a counterpoint to the notion of warming up, particularly regarding the idea of “run-in.” One publication presents a comparison of two subwoofers—one warmed up and the other not—where instrumental measurements indicated that their sound parameters remained unchanged. However, details regarding the warming process, including the type of signal used, the power level, and the duration, were not provided.

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Electronic components

It is important to recognize that both the emitters and the crossovers experience temperature increases during operation. While the extent of heating may not be as significant, it is essential to consider that within the enclosed space of the speakers, temperatures can rise when they are played at higher volumes. However, the situation becomes more complex with nonlinear and digital electronics.

It is important to clarify from the outset that I am not inclined to engage in a discussion about the warming of digital circuits. To be candid, I do not see how this factor influences the comparison of checksums. Clock frequency generators are specifically engineered to eliminate concerns regarding warming. This principle extends to nearly all facets of digital operation, with the possible exception of error rates. For similar reasons, I will refrain from discussing class D amplifiers in this context, as there has been relatively little written about their warming effects.

In contrast, the scenario with analog electronics is markedly different. It is well understood that analog systems consist of active and reactive resistances, along with semiconductor components, all of which generate heat during operation. When someone claims that a particular preset does not produce any heat, they are likely referring to a purely passive circuit (which, if examined closely, still generates some heat) or may not be entirely truthful. If you touch the device’s casing after an hour of use, it will invariably feel warm. This is particularly noticeable in a cooler environment.

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electronic components

Amplifier circuits, which are integral to all analog devices, are particularly prone to heating. Tube amplifiers, especially those operating in the uncompromising Class A mode, are the most notable in this regard. A small fraction of the energy is utilized for amplification, while the majority is dissipated as heat. With tube technology, the principle is straightforward: if the tubes are not heating, they are not functioning. The warming-up process is marked by a gradual degradation of the tube electrodes, and after approximately 2,000 hours of use, the need for replacement becomes evident as the warming-up effect diminishes.

In contrast, semiconductor circuits exhibit greater durability. However, during operation, analog electronics can experience significant changes in their parameters due to temperature fluctuations. This can lead to unexpected outcomes. The author has witnessed a situation involving a reputable device that, after 30-40 minutes of use, suddenly altered its sound and exhibited erratic behavior. The issue stemmed from transistors that were mounted to a cooling radiator, which was in turn attached to the circuit board. Thermal expansion caused the radiator to slightly displace the transistor legs from their soldered connections, and upon cooling, they returned to their original position. Diagnosing this problem took several days.

Beyond temperature variations, other factors also influence the performance of electronic components. The characteristics of conductive materials can change, while semiconductors and resistors may experience a phenomenon known as “creep.” Capacitors, particularly electrolytic types, can exhibit issues such as swelling, drying out, or even catastrophic failure, warranting extensive discussion on the subject.

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I have reservations about the benefits of these processes after, for instance, 50 hours of warming up. Initially, similar to speakers, a period of adequate load—approximately one hour—is necessary for the device to reach a stable operating temperature before listening can commence.

In addition to temperature processes, there are other factors that change the parameters of electronics.

In addition to temperature processes, there are other factors that change the parameters of electronics.

Additionally, there is a perspective that class AB amplifiers should remain powered on during regular use. It is suggested that they draw minimal energy while idling, which allows them to maintain optimal performance continuously. This approach certainly merits consideration.

The perspectives among semiconductor analog audio manufacturers regarding the necessity of warming up and running in their products vary significantly. Some manufacturers support a continuous operation period of one to two days under a proper load, while others assert that their products do not require this practice. Additionally, some companies incorporate this process as part of their final technological procedures. There are even those who utilize cryoprocessing for circuit components, submerging them in liquid nitrogen for a certain duration. While this method appears impressive and potentially beneficial, I have yet to encounter any compelling evidence or instrumental measurements that substantiate its effectiveness.

Cables

Cables undergo cryogenic treatment as well. Manufacturers defend this process by citing factors such as the crystal structure of the conductor, among others. A brief aside: I hope the “cable” companies will excuse me, but their narratives about new products occasionally evoke tales of mystical occurrences akin to those found in the practices of Eskimo shamans or the independent operation of UFOs.

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During operation, the impact of temperature on the properties of the cable is minimal. The heating of the acoustic cable, particularly in intercomponent configurations, can generally be disregarded. Additionally, the conductivity and shielding characteristics are unlikely to experience significant changes over time. However, it is important to remember that electronics fundamentally revolves around connections. Modern cables typically utilize crimped connections rather than soldered ones at terminals, tips, and connectors. This approach not only mitigates harmful electrochemical processes but also enhances production efficiency. Consequently, the primary variable affecting the transmission of an electric signal through a cable is the quality of the contacts.

This variability is crucial, as a poorly connected, even high-end cable, can adversely affect the sound quality of a good audio setup. It is well-documented that contact resistance tends to decrease after a period of initial operation, a phenomenon often referred to as “warming up.” I believe that after cables have been connected for some time, internal mechanical stresses may dissipate, leading to a more ordered crystalline structure, which could positively influence sound quality. Is it possible to perceive these changes? I have spoken with individuals who assert they can hear these differences. Do I dare to dispute their experiences?

As for cable manufacturers and their thoughts on warming up (running in), everything here almost coincides with the opinions of semiconductor component makers.

As for cable manufacturers and their thoughts on warming up (running in), everything here almost coincides with the opinions of semiconductor component makers.

One issue associated with contacts is the alteration of their surface composition, which occurs not only due to oxidation. Any environment inhabited by living organisms, including even the most dedicated audiophiles, harbors waste products that accumulate on all exposed surfaces, forming an invisible film. This includes the surfaces of contacts.

This phenomenon can be easily demonstrated; for instance, after a decade of undisturbed use, wiping a TV screen in a living room that has seen considerable smoking can lead to a dramatic enhancement in brightness, color, and contrast. It appears that cleaning the screen with a sponge positively influences the HDR capabilities of the display. Professionals who handle contacts routinely clean their surfaces for a reason—there was a time when pure alcohol was a common cleaning agent. In fact, even a simple action like disconnecting and reconnecting cables can yield more noticeable improvements than merely allowing them to warm up.

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Regarding the perspectives of cable manufacturers on the necessity of warming up (or running in), opinions largely align with those of semiconductor component producers. Some assert that warming up is unnecessary, others claim it has already been accomplished during manufacturing, while some suggest, “give it a try; it won’t hurt.” Additionally, the degradation of polymer insulation materials can affect the operating parameters of cables, but this issue appears unrelated to warming up, as its progression typically requires a significantly longer duration.

Evaluating sound quality

Evaluating sound quality through audio setups, which is primarily how one assesses the effectiveness of warming up and running in, involves subjective testing. In contrast, objective testing necessitates the use of instrumental measurements or, at a minimum, assessments conducted by multiple experts who complete protocols and score various sound characteristics. Additionally, employing a blind comparison method enhances the reliability of the evaluation.

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It is widely accepted that after a brief pause of around twenty seconds, our ability to recall the characteristics of a sound diminishes significantly, making it challenging to detect subtle changes, such as those resulting from a speaker cable replacement. This raises the question: how can one expedite this replacement process, especially when the same technician is both listening and making the change?

This is why I find it remarkable when colleagues assert that after returning to the listening room following a 24-hour period of “warming up” the setup, they perceive dramatic differences in aspects like the width and depth of the soundstage, the bass response, and the clarity of female vocals, while noting a perceived lack of clarity in male vocals.

Objective testing requires instrumental measurements, or at least listening by several experts with filling out protocols and scoring aspects of the sound. Moreover, using the blind comparison method.

Objective testing requires instrumental measurements, or at least listening by several experts with filling out protocols and scoring aspects of the sound. Moreover, using the blind comparison method.

I often wonder about the expert’s state of mind the previous day—did they feel a bit under the weather on their commute, have a disagreement with a partner, or enjoy their morning coffee? Each of these elements can influence their sound evaluation the following day, potentially as much as the “run-in” period of interconnect cables and filter capacitors in the linear power supply circuit.

There is an additional element to consider: the adaptation to the listening environment itself. Furthermore, who among us has not experienced the revelation of new nuances in a familiar recording, seemingly without any changes to the room or the audio components? This phenomenon can occur at any moment, simply by shifting your listening mindset. I encourage you to engage in active listening rather than passive hearing. This straightforward approach often yields results that far exceed any preliminary warm-ups or break-in periods.

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So, what is the takeaway? Is warming up necessary? Absolutely! It is essential. Immerse yourself in music daily. Savor it, whether after a delightful cup of coffee or a less satisfying one, in varying temperatures, alone or in the company of fellow enthusiasts. This practice will undoubtedly serve as an excellent warm-up for your equipment. It is indispensable.

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