[DIY] Four simple DIY loudspeakers

A journey through no-brand loudspeaker land - Part I

Four, simple DIY projects

Author: Richard Varey - TNT New Zealand
Published: February, 2015

This is a tale of open baffles, vintage drivers, super-tweeters, and a fascination with simple enjoyment of recorded music. The "loudspeaker" is often the simplest component in a music reproduction chain, yet it can have a profound impact on musical enjoyment. Speaker drivers come ready-made, so what can be done with them, and what if this was as simple as possible? Over the past couple of years, I've been exploring in search of full-range and open baffle projects. Music is my daily pleasure and my quest for an engaging experience is always satisfying but never finished. As a member of the TNT-Audio team, I think an account of my experience traveling the road less travelled, far from the madding (some might say maddening) retail crowd in brandland might encourage and inspire DIY experimentation.

By way of context for this story, a look at my introductory pieces for TNT-Audio (see here and here) will indicate my penchant for finding another way to pursue my hobby without succumbing to the siren call to be the "legal prey" of big-bucks brand-marketers. Why spend thousands on speakers? Could I side-step the large profit margins and excess of extravagance by turning to re-use? I don't believe that "new" is always better, and enjoy experimenting and DIY.

Could frugality be an audiophile virtue - part of the quality syndrome? I'm a self-confessed frugal-audiophile muso experiencing music highs without the high-end prices. How so? This is the classic make or buy choice, but we are profoundly conditioned by seductive sales promotion to buy, and especially subject to snake oil promises. So, why buy retail when this means marketed product and inescapable hype? A quick glance at my Pinterest board "Loudspeakers that Inspire" shows two things: I like unusual speakers, and there is mega-variety in forms. A search of the Internet reveals an almost endless variety in speaker form - shape, materials, colour, size, degree of complexity, cost - I was inspired and started collecting interesting projects on my Pinterest board.

In thinking "without a box", my criteria were: simple construction/easy home DIY, low cost / recycle, and a real enhancement to my listening experience. I previously used KEF iQ7s (cost in retail NZ$1,800 in 2007) with a recently new T&A Power Plant Balanced amplifer (which replaced a Cambridge Audio 840A that failed spectacularly). I was already using an REL Acoustics Quake Q200 powered sub-bass speaker (which operates down to 17Hz (-6dB)) in my music room which is 6.4 m x 3.9 m x 2.4 m, with three wooden doors, and glass doors on one side, and with a concrete floor covered with floating wood laminate. Cabling is hand-made bi-wire by Brendan of RuleConnect, Waimata (New Zealand). I wanted to reproduce recorded music with a big soundstage and musical realism to experience the excitement of the musical performance by hearing and feeling what the musician(s) expressed in the recording. But I had no intention of becoming a loudspeaker engineer.

What level of music reproduction satisfaction could be acomplished with a DIY approach using salvaged - perhaps vintage - full-range drivers and minimal woodworking skills? What is it achievable as a frugal audiophile? I sought appropriate technology for the purpose rather than what we are sold. I have oberved in my more than 40 years of music and hifi hobbying the law of diminishing return on investment in over-engineered products made for profit. Put another way, I wanted as simple as possible - no cabinets, no cross-overs, no tuning, suitable for my room setting, and no specialist equipment rnecessary - cutting holes for the drivers would be the hardest task, so a router was to be the most sophisticated tool needed.

Recent experience in certain discussion forums reinforced my desire to escape brand, model number and price boasting. What could be achieved for my ideal price - as little as possible? I was told to leave one forum when I questioned the $10,000 to $250,000 price tags of the products everyone was advocating. I was aggressively told that I was not wanted in the group if I was going to be critical and suggest frugal alternatives. In another popular audio discussion forum, a member recently asked other members for opinions on performance and value-for-money of a loudspeaker brand and model - after he'd bought them for $43,000!! Is this staggering naivety or stealth boasting?

So, here I'm telling my story of four projects in a 2-year journey of adventures in "no-brands/no fashion land" - largely inspired by my regular and avid reading of TNT-Audio reviews and other articles over several years. I began by asking why are loudspeakers usually boxes? Simplified, they are a baffle or mounting plate for the driver that controls the coupling of the driver to the air in the listening space. Keep looking long enough, and you can even find speakers without baffles!

A combined airflow controlling, driver mounting, and aesthetically pleasing box is a complex design problem. Solutions to volume, shape, bracing for rigidity to deal with vibrations and resonances and other colourations, drivers mountings, and other design problems require a compromise of cost of materials and machining, assembly, size and weight, packaging and transportation, storage, presence in the domestic setting, etc. Some speakers seem to have been conceived in the region where advanced carpentry and engineering and sales glitz are more important than musicality.

Project 1 - unknown drivers in simple transmission line cabinets

Simple transmission line project

In starting this journey, two opportunities coincided that prompted action - Eric Cross at Vintage Audio World in Christchurch, New Zealand had a pair of 6.5" full-range drivers for sale for NZ$100. He had coated the diaphragms with Meranti Damar natural resin to enhance tone and they had an old Kauri wood puck glued to each magnet housing to "reduce resonances". I was intrigued. A local used audio trader had a pair of transmission line cabinets that were almost finished and a steal at NZ$25. They just needed drivers, internal wiring, and painting. I mounted the drivers on off-cut baffles that I attached to the cabinets, added CAT5 cable and banana sockets, and painted them.

In use there was an immediate impression of more punch, yet delicacy and detail compared to the KEFs (which were relegated to the TV room). By now I had the experimenter's bug. If that was the excellent result of a cabinet mount, what might an open baffle sound like with bigger and better drivers?

Project 2 - vintage full-range on an open baffle

Plessey 8" full range drivers

I used new old stock Plessey 8" full-range drivers made in New Zealand in the 1970s (again from Vintage Audio World), and mounted them in waxed 900 mm x 450 mm x 35 mm Pine boards with the cable connectors soldered directly to the driver wiring tags. The baffles are held upright in position with hinged single leg props, so I can adjust their angle of recline. The sound is more open and detailed than the KEFs and punchier and more airy than the transmission lines. This project cost me NZ$200 total. Assembly of working speakers couldn't have been easier!

After a few months of enjoying my music and further exploration of DIY speaker projects for my Pinterest board, I accepted that brand names and model numbers on drivers are important as indicators of quality of performance - and cost! (but for me not as a boasting badge). What could I accomplish with higher performance drivers?

Project 3 - vintage 12" full-range mounted on a designed baffle

Philips in JE Labs baffles

A 12" diaphragm is about 2.25 times the surface area of an 8" driver and 3.4 times the area of a 6.5" driver, depending on the shape. Could I get greater musical realism from a bigger sound by moving more air?

I got a pair of vintage 12" Philips AD 1256-M8 AlNiCo 8 ohm 30W dual cone full-range drivers in excellent condition (response range 45-16,000 Hz (98dB sensitivity) - some specs. show the upper limit as 17 KHz), made in Holland probably about 1969, for about NZ$400 from Eric Cross at Vintage Audio World. These drivers are quite rare nowadays and sought-after when in great condition. They are renowned performers, and have been described as "probably the best sounding full range driver ever". Eric promised me that they would sound great.

I initially mounted them in a popular JE Labs design - with a 900 mm x 800 mm x 30 mm waxed Pine baffle. Materials cost $160 plus 15 hours preparation and assembly time.

In situ these proved to be way too big for the room - and sounded rather dull and muffled and lacking clarity and openness. This was a big disappointment, especially after so much woodwork (relatively), and I removed the drivers for a further experiment. What if I again went as simple as possible - but more so?

For the fourth DIY project you should wait for the second part of this article.