Optimization of design and acoustic parameters of wood-based loudspeaker enclosures

Abstract

This thesis focus on the optimization of the design and acoustic parameters of wood speaker enclosures, more precisely the acoustic properties of baffles made of solid wood from low-preparatory, or “pioneer” woods, such as rowan, willow, aspen, birch and alder.

Loudspeaker enclosures will be manufactured according to design proposals, which will also be one of the main pillars of this work. At the same time, a market study and trends will be conducted based on survey studies conducted across the general public.

As a result, will combine design, originality, sound, different price options, with cheap and undervalued preparatory wood. Solid wood is still a better resonance material than agglomerated materials that are generally used for the production of enclosures. However, it also has heterogeneous and anisotropic characteristics that must be addressed depending on the proposed design in order to maintain optimal acoustic properties. As well as wood defects, this will, however, be an effort to take advantage of the originality and uniqueness of each complete speaker system.

Introduction

The design & acoustics of speaker enclosures made of wood, or materials based on it, are essential haptic parameters (perceptible by hearing, sight and touch), which need to be solved as a complex matter in mutual synergy, and of course also with regard to the price. Although this is not a completely unknown area, there is still a lot of space for innovation, both in terms of design and acoustic parameters. According to Loučanová et al. (2017) innovation is an important prerequisite for commercial success in the market. It can be assumed that the customers’ decision-making when choosing loudspeakers will be influenced by functionality, price and also appearance, which is more related to the aesthetic and emotional perception of the product. For example, the importance of the color of wood products, which is important from an aesthetic point of view, as stated by Cademartori et al. (2014), or Sedlar et al. (2019).

For the sake of uniqueness and aesthetic qualities, there will also be an effort to work with wood defects in the production of sound boxes, which could appear to a certain group of customers as pieces of design interest. Here, however, there can be complications with maintaining optimal acoustic properties, even in general due to the unreliability of solid wood due to its anisotropic and variable properties, as reported by Hardwood, et al. (1977), and for that reason relevant attention will be given to this issue. As Bucur (2006) states, thanks to the choice of the shape of the enclosure, it is possible to achieve some predetermined goals of the acoustic design in a targeted manner.

Methods

As part of the literature search, the relevant properties of wood and materials based on it will be processed. Furthermore, the issue of sound technology and loudspeakers will be discussed. Acoustic parameters are determined for the wood of preparatory species (birch, aspen, alder, possibly also willow and cranesbill), i.e. acoustic constant, acoustic wave resistance, logarithmic attenuation decrement and resonant frequency. After making design proposals for loudspeakers for machine and manual production, the enclosures will be physically manufactured and then the acoustic parameters (impedance and frequency characteristics, quality factors — Qes, Qms, Qts) will be determined and analyzed.
An impulse response will be used to measure the resonance characteristics of each loudspeaker, and it is assumed that the method of retuned harmonic signal or “retuned sine” or “Sine Sweep” will be used (Sauther 2013). In this method, the system is excited by a harmonic signal whose frequency increases over time (exponentially in this case) and the response of the system will be recorded. Subsequently, the impulse response can be obtained by filtering the input signal with an inverse filter, or by separation in the spectral region. When proceeding with this method, an advantage is, for example, the separation of harmonic distortion.
Finaly, a marketing survey of the market will be carried out with regard to the current preferences and financial possibilities of potential customers.

References cited

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4. Dudík, R., 2021. Preferences of colour shade of birch veneer at potential customers, 14th International Scientific Conference Wood EMA 2021

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