[TNT-Audio Test Bench] The measurement of loudspeakers by TNT-Audio

The measurement of loudspeakers is an important tool for understanding their actual behaviour, going beyond listening impressions that can be influenced by the environment, placement, and inevitable subjective factors. A consistent and repeatable measurement protocol makes it possible to analyze fundamental aspects such as frequency response, off-axis dispersion, low-frequency behaviour, electrical impedance, and consistency between the two units of a pair.

Objectives of the protocol

The objective of this protocol is to provide a transparent, repeatable, and explicitly limited technical analysis methodology, suitable for evaluating loudspeakers in a non-anechoic environment. Measurements are carried out in a domestic setting using accessible yet reliable tools, with the aim of producing data useful for understanding loudspeaker behaviour without attributing a level of precision that would require dedicated professional facilities.

The protocol arises from the need to complement subjective reviews with a set of objective measurements, carried out according to consistent and well-documented criteria. All procedures have been designed to ensure:

How the measurements are performed

Measurements are performed using FFT analysis with the software Room EQ Wizard or ARTA, together with omnidirectional measurement microphones. Although these tools do not belong to the class of professional instrumentation used in research laboratories, they allow sufficiently accurate results for comparative technical evaluation, provided that the intrinsic limitations of the method are clearly stated and respected.

Since measurements are carried out in a domestic environment, time windowing (gating) is applied to reduce the contribution of room reflections. This approach allows reliable frequency response measurements above approximately 300-400 Hz, while complementary techniques are used for low frequencies, such as ground plane measurements or near-field measurements of individual system components (woofer and bass reflex port). The combination of these techniques makes it possible to reconstruct a plausible full-range response of the loudspeaker, while explicitly acknowledging a small degree of uncertainty in the transition regions between the different measurement methods.

Measurements are taken without applying smoothing greater than 1/24 octave, unless otherwise specified, with the microphone positioned at tweeter height, and after a loudspeaker stabilization period of at least two hours.

What we measure

A particularly important aspect of the protocol is the verification of matching between the two speakers in a pair. Whenever possible, both the frequency response and the impedance curves of the two units are compared. With this we can assess the consistency between the loudspeakers supplied by the manufacturer, a very important aspect for correct stereo reproduction that is rarely documented in reviews. Significant differences between the two speakers can affect tonal balance and the stability of the stereo image.

The combination of these measurements allows different aspects of loudspeaker behaviour to be described, including:

Measurements and subjective review

A fundamental principle of this protocol concerns the relationship between measurements and subjective review. To avoid any form of cognitive bias, the subjective evaluation of the loudspeaker is carried out before the publication and analysis of the measurements. The reviewer therefore does not have access to the measurement data during the listening phase, in order to prevent technical information from influencing perceptual judgment. Measurements are published and discussed after completing the subjective review thus allowing comparison between listening impressions and objective data.

Conclusions

This approach does not aim to replace subjective reviews or measurements performed in laboratory conditions or in anechoic chambers, but rather to provide a coherent, honest, and repeatable technical framework useful for interpreting loudspeaker behaviour and comparing different products within a consistent methodological context. In other words, the purpose of this protocol is not to eliminate uncertainty - impossible in a domestic environment - but to make it explicit, controlled, and comparable.

It is important to emphasize that such a comparison does not constitute a validation of either the loudspeaker�s quality or the reviewer�s accuracy, but rather represents an opportunity for critical analysis between perception and measured behaviour, within the declared limits of the protocol.

The analysis of the measurements will focus on the most relevant findings, contextualizing them according to the price and market segment of the speaker.

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The measurement of loudspeakers by TNT-Audio

Presentation of the measurement and evaluation protocol for loudspeakers

Introduction

Objectives of the protocol

How the measurements are performed

What we measure

Measurements and subjective review

Conclusions