Thursday, 19 September 2013

Harmony – Aspects of Technically Reproduced Sounds

Today I want to introduce a entirely fundamental questioning about qualities of speaker cabinets in sound reproduction. Under the influence of the evaluating my actual test cabinets a long time covered questions arose again. For years I am in the process of finding answers about timber woods, acceptable resonances and construction details of different loudspeaker cabinet design principles. Is there a relationship between the used materials and their harmonic properties? Does a speaker sound any better when built into a housing designed like an musical instrument? How does it compare against a technically advanced design aimed to reduce all resonances by the use of compound materials? Are directed resonances and inherent  harmonious effects superior than multi layered compound materials or even as far as dead damped materials? Let me ask in this specific case, does a speaker sound in a piano case more natural, subtile and more expressive as in a dead damped box? Is it even similiar with wooden instruments that certain types of wood in combination, their optimal growth, location and age, the degree of drying can harmonize a perfect housing for a moving coil cone speaker unit?

I think yes, these issues are important – indeed critical, and their optimized implementation can significantly improve a speaker cabinet dramatically towards its natural sounding capabilities. This actual understanding stands in contrast to the fundamental research project BBC RD 77/3 of classic loudspeaker cabinets done by H.D. Harwood for the BBC research department in 1977. This research was based on the speaker designs exclusive developed for the BBC in the late 1960ties, were companies like Rogers and Spendor have built several speakers for monitoring use like the BC1 and the well known LS-series. This research has build rails for the classic school of british loudspeaker design, commonly known as two way systems with small scale drivers (KEF), small baffle, rigid enclosures, complex crossover design and at the end highly inefficient properties.

Cabinets for BBC LS3/5a (30x19x15cm HWD )with synthetic foam damping
Less resonant materials have been researched, compound layers, even sometimes doubled with sand filling and highly strengthened constructions to find the acoustical "dead case". No wonder that cabinets made from three inch concrete came into account, just "to give resonances no chance". It ended up, as everybody knows with dwarf coffins, shoe box size speakers and 5 kg filter units for the crossovers (LS 3/5a, etc.) – loudspeakers with off-trained attitudes – sound generators with the need of 200 watts class a power to work with decent dynamics. Todays studio speakers have taken the relay race.

This is going to be a discussion between two contradictive positions, "the precision engineered system" and the traditional crafted musical instrument. We are talking about the technical advancement and its reliable proof by measurement, as we talk about the down passed traditional knowledge from generations of crafted masters over centuries of acoustical hand built instrument production at the other side. We are talking about the believe in technical advance and its opposition the faith into the higher order of natural superiority. There is no high tech stradivari nor a electronic enhanced piano known, able to displace this classic acoustic instruments. I cannot recall lots of arguments why a subtle harmony distribution should be different with loudspeaker cabinets?

Today we are looking back again to that time of the early beginning, the time were Western Electric, RCA, Klangfilm and others developed systems for professional use in theaters and cinemas in the late 1920ties. We are looking back to that time of inventors, were the difficulty of lacking amplifying power was confronted with the need to match the size of several thousand people filling halls. The shear physical demand of loudness made the mechanical support of the amplification necessary. Wood was the material of use to form funnels, cabinets and baffles for this reason. These inventors used constructive timber to strengthen their designs, northern coniferous wood sorts like they were used for other construction in other fields. They evaluated their designs by extensive listening tests and refined the results step by step. The designers did not have the opportunity to use modern composite materials, so they used solid timber wood and traditional wooden conjunctions to strengthen the constructions.

Today listening to such a system from Western Electric or Klangfilm shows us a lot about that principles. These huge size systems work with resonances and other side effects. Their tonality is colored and expressive, but they bring us a lot closer to the distribution of harmonies like the natural sound of acoustical instruments and its energetic content than contemporary solutions can do. Almost a whole century we tried in the believe of this myth – the technical advance as mastermind for any sort of progression. We have already learned about the shadowside of this believings and as well here, we need to rethink some basic ideas about sound reproduction.

Klangfilm  system with original baffle board made from solid timber woods in a japanese weekend residency. 
A huge speaker  (like a 12", or a 15" or even a 18" unit, permanent or field coil magnets) is a motor unit initiating a lot of mechanical energy during operation. This power of energy cannot be removed, it cannot be compensated by damping or with other forms of mechanical isolations. This energy is always present, it is just a question if its resonances will be used to distribute harmonies in order to complete the sound structure with emotional content.

I would be happy, if a sort of discussion will arise from this article and some of the countless readers of this blog, will start to comment this article with their personal experience and expertise in this field.

Read on soon, Volker

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