Building Speakers to Last
Northern Michigan is a beautiful place. I didn't realize how beautiful until I grew up and ventured out to other areas of the country. I took it for granted because Up North was where you went for vacation if you grew up in Southeast Michigan, and even Northern Ohio/Indiana. It's where my parents went every summer when they were kids - it's where I went every summer - it's where my friends went every summer. Many families had small cabins in remote locations in Northern Michigan where they spent summer weekends. Occasionally, I was lucky enough to tag along with a friend's family on one of their vacations where I stayed in their cabin and was governed by a different, and often much more lenient, set of parental guidelines. The story of my adventures under limited supervision are best told in another setting, but there was a common theme among many of these excursions that always intrigued me.
On more than one such occasion, I was told by my host friend that his grandfather had built the cabin we would stay in. This was a very romantic idea to me and I immediately found myself inspecting the details of the interior and exterior, and studying the design choices that were made 50-60 years prior by the amateur home builder. We would go out picking wild blackberries and bring back bowls full to wash in the kitchen his grandfather had built. We would walk back from the beach and track sand onto the hardwood floors of the washroom his grandfather had built. We would lie in bed and tell age-inappropriate jokes and stories as we drifted off to sleep in the bedroom his grandfather had built. Our activities were always framed for me by this accomplishment from half a century ago, and I wasn't even a part of the bloodline.
I actually don't know the details of how the construction took place. It could have been that his grandfather had hired some very experienced help to construct the cabin while he supervised, or maybe just paid to have the cabin built while he was downstate working a well paying factory job. Whatever the reality of those details, I fully imagined a single human painstakingly designing and building this cabin, nail by nail, for the enjoyment and security of his family. I reveled in that idea and grew up thinking that I would learn how to build homes, and that I would build a place for my family to dwell and that maybe one day, one of my grandchildren would tell his friend, "my grandfather built this house."
Nobody really does this anymore. Very few people learn a craft and create something with their hands, especially something that can last for generations and maintain its value over those generations. Mass production has made it so almost everyone can afford one or two of anything a body could want. If it breaks, and it probably will, you just buy a new one. It's not a bad system and honestly, our lives are much more convenient as a result of it. We don't really need things to last for generations... but there's something about that that sucks.
I never learned how to build houses, but I did learn how to build speakers - good ones that are more capable than anything most people will ever have in their homes. And if loudspeaker technology and consumer trends stay on the same trajectory as they have for the last 50 years, the speakers I build today will still kick relative ass 50 years from now. As I sift through the variables and make compromises in each system I design and build, those words linger in the back of my mind: "my grandfather built this." As such, there are a handful of choices I make that really don't contribute much to the immediate sound quality, but contribute greatly to the potential longevity of the system. Some of these choices are more costly and because of this, are opted against by many designers. Most of them, however, just require limiting the pool of potential drivers or utilizing good construction techniques. Either way, every speaker I design is designed for the long haul. The following is a list of those choices and why they are important to building a speaker that will last:
1) Cabinet Construction:
Using proper construction techniques will ensure that your speaker cabinet will stand the test of time. This includes accounting for the seasonal expansion of solid wood and creating clean joints with adequate glue and clamp pressure.
2) Surround Material:
Although foam surrounds are much less susceptible to dry rot than they used to be, they still don't last as long as a rubber surround, and probably because of this, they seem to be less available today. If longevity is on your wishlist, choose drivers with rubber surrounds.
3) Ferro Fluid:
This ferrous liquid is sometimes used to fill the gap in which a tweeter's voice coil sits to reduce the impedance peak and conduct heat away from the voice coil. This fluid can break down over the years changing the tweeter's impedance in the process. This in turn changes the crossover's transfer function and ultimately the sound of the speaker. Choosing a tweeter without Ferro Fluid will prevent the possibility of this change.
4) Capacitor Material:
Non-polarized Electrolytic capacitors are cheap and effective in speaker crossovers, but they don't last forever. Eventually they can dry out, changing the crossover transfer function at best and stopping the signal completely at worst, depending on where the capacitor is in the circuit. The solution is to use a Polypropylene film capacitor in place of the NPE and never give it a second thought. Poly caps are generally much more expensive than NPEs, but I say it's worth it to ensure that the speaker you build performs just the way you intended it to for as long as anyone is willing to listen.
I make these choices so that maybe one day in the future, maybe long after I'm gone, something that I made will be displayed in a living room, scuffed from countless moves, playing the hits of 2067, and maybe someone will yell across the room, over music playing at ear damaging levels, "MY GRANDFATHER MADE THESE." Now, I know a pair of speakers is not quite as noble or grand as a structure that a family can live in, but it's still pretty cool.