Stress case: Speaker enclosures that work, vs ones that don’t.

A speaker enclosure; some wood, glue, a few fasteners, nothing special. A statement that I disagree with fervently as nothing could be farther from the truth. The work of an enclosure is complex, the gravity of its inabilities can not be out-run and the successes are generally overlooked, under appreciated, dismissed entirely, or worse yet, credit is bestowed elsewhere. Yes, the perception of mass marketing is that the work of the enclosure is to “look nice” with little attention being drawn to the physics behind things that are to remain put, not fall down, or otherwise crumble under stress. Speaker enclosures that work is the critical difference most people are in fact looking for but do not yet realize it.

On various forums, such as AVS, Audioholics, ASR and other sites, and without pointing to specific instances, the general consensus is that the role of the subwoofer enclosure is to prevent sound waves from cancelling and to shape the frequency response. The reality is that the forces put on an enclosure apply both positive and negative pressure to an enclosure, along with vibrations down to whatever the driver can produce. The enclosure's job is to resist these stresses. How can a material that is designed for either cosmetics or high sheer conditions (kitchen cabinet doors, baseboards, floor joists, or wall studs) resist both positive and negative forces in, not only sheer, but tension, and compression? If that isn't enough, you also have to look at elastic properties in resistance to resonance as well, I'm looking at you MDF. To put it simply, what an audio enthusiast asks of an enclosure is n to the 6th power more complex than what is commonly lauded as “good practice”. Disagree if you must, however, known for shoddy workmanship and ambiguity, I am not. The mechanical and acoustic limits of the material become a large part of the system limit long before cosmetic styling cues and mass production cost savings. Precision production is where we anchor ourselves, and this is our foundation. 

Tenet or Donnie Darko?

Neither. This is not some inverted time warp or paranoid schizophrenic delusion. It’s literally all around us, every day. The name is temporal distortion, and most people loathe it without knowing its name. Temporal distortions deliver a sense of a harmonic distortion that is out of phase, lost and out of sync with time. Like time is bending. It can sound like intermodulation distortion (IMD), it can go away and come back based on the content. It can sound fuzzy, buzzy, or just not clear. It takes time to build up and time to dissipate. It can localize or even work with your room resulting in some very strange effects, again, based on the content you are playing, and minimizing these effects is exactly what results in an audio experience that makes you want to stay and marinade vs one that you would rather take a flame thrower to. 

Controlling this ill effect isn’t anything you haven’t seen before either. From a building with seismic and acoustic controls or in the chassis of your car, this brand of engineering has been around since the 1930’s. Enclosure science is all about controlling the good vibrations and limiting the bad and how this is done is by engineering the structure to withstand the forces imposed on it. In short, bracing m’dude, bracing. Sticks and stuffing is simplistic at best, whereas using structural engineering makes the result better and, by extension, harder to achieve in mass production terms. 

All in all…

However, we are not bricks, and neither are your speakers. Actually, bricks are a terrible enclosure material too. So what material makes a good enclosure? The answer is complex and pedantic, which, by extension, also makes it annoying. So in the spirit of getting this part over with in as short a fashion as possible, here are the bullet points:

• Not a material that's essentially dust held together by glue. MDF is trash. There is a reason it is not used as building material like studs or beams. You might disagree, but the modulus of elasticity doesn't and Young’s modulus doesn't.

• Strength in all directional vectors: flexion, tension, compression and in all directions.

• The right proportions of damping.

• And even more right proportions of stiffness.

If you use these principals and sort through the mishigas, the list of suspects becomes unusually short. 

What does this do to the price? A lot. A painful lot. The cold and bitter truth is that CNC is not the savior of production volume and speed everyone wants to believe it to be. The reality is that most CNC enclosures have reliefs cut into them to allow for the tolerance of the CNC tooling. It is widely asserted that wood CNC machines operate to about +/-0.13mm with the best achievable tolerance being +/-0.05mm, and by contrast we manufacture to 0.0mm tolerance. In other words, they are precision enclosures, but only within an allowable degree… usually determined by someone who counts things for a living, and does taxes, and knows what a financial report is. So if the universal blessings of CNC are subject and in relation to financial scrutiny, then the consistency of the product must also have an allowance for a certain percentage of stool. And if the consistency of the product has a tolerated turd quotient, then just maybe more work needs to be done on the manufacturing level to make the unit work reliably, predictably, and sans a certain odor. 

Now, I can not speak for all manufacturers, but I can and have spoken for myself. What I know is that the real precision fit and finish of woodwork comes from the hands of people. Using CNC for our production, sure, however everything, and I do mean ev-er-y-thing, gets clearanced by hand and with painstaking precision. This is where the old adage jumps in; good, fast, or cheap, pick two. This also so happens to be the exact same point at which we say “good” isn’t good enough. 

So the real question is, how does all of this relate to the Harbottle LDLC thing? If I may further entertain you,  LDLC is a maximum limit of poor sound characteristics.  This includes a maximum amount of temporal distortions from the enclosure, i.e. enclosure resonance as reviewed above. This coats certain frequencies with a layer of fuzzy sound, especially in the upper bass into the crossover and beyond into the main speakers bandwidth. All distortions are restricted to the “inaudible” level, which seems wonderful, but in the often shocking world of reality, the art of getting there is decidedly more involved. Inaudible distortion from the enclosure, means that the enclosure must resist everything that the driver delivers. Again, ev-er-y-thang. So in some cases it is not enough that the enclosure is precision crafted, it needs more. 

Carbon; villainized element of climate change? Or a really strong thing?

It’s strong. The climate change thing, well, we all manufacture carbon dioxide, and plants eat it to make more oxygen, plus a host of other factors, I will leave the debating and taxation for the politicians.

The question I get asked often, very often in fact, is ‘what is the difference between your product lines?’ And this question generally circles around our Cassini Carbon subs. Carbon fiber is a magical tool that allows our drivers to beat on the enclosure without mercy. So hard, in fact, we can run up to 9600 watts rms /20,800 watts peak, on a single box with driver mechanical limits at 80 mm of excursion and still maintain LDLC limits of audio sound quality. The work involved to get a box to perform to this level is exponentially more and more difficult, because the last thing that carbon fiber is used for is a finish. It’s not a finish. Carbon has structural properties and so we use it as a structural component, and there is nothing that is simple about the carbon manufacturing process to make it a structural member.

“So if the base material needs to be of a quality that actually works to reinforce driver behavior while remaining neutral, and carbon can be used to make the enclosure work better and get better sound, but doing this work is costly and hence not what the average person generally signs up for, then why offer it in the first place? Who cares?” Fair points on all fronts. The truth is that Cassini Carbon subs are for people who are fed up with marketing hype and genuinely want the most inert enclosure for their subwoofer. Which can be any one from the trash collector that runs your block, to the nurse in the hospital who is tired of hearing PA audio all day. Quality that is founded doesn’t have a defined demographic, because its home is a personality type. 

There are three reasons to want Cassini Carbon: 1) you love the look and nothing else will do,  2) you are tired of fuzzy sounding subs,  3) you plan on serious levels of audio output and demand that sound quality is retained. Any two of these reasons should be enough to seriously consider Cassini Carbon. But it doesn't mean it's the only option. Cassini Tradition and Signature are both viable, they just limit sooner. The prime example of this is the Cassini Signature 124 mk2. This gets so close to the edge of LDLC limits, it's really the subwoofer that defined LDLC into the terms we use today. Then the 218S further reinforced that definition. The question is, do you need less resonance in your life?

Understandably, Cassini Signature offers the best of both worlds from a sound quality standpoint. Afterall, Signature is my personal opinion on how a subwoofer should work in the real world. 

The only reason to need a 200 hz subwoofer unless you need to deal with poor main speaker bass performance. And the fact that you can actually use the Tradition subs up to 200 hz means there is a lot of wasted bandwidth efficiency, where the extra bandwidth becomes more of an insurance policy. 

Whereas Signature is far more realistic in bandwidth which gives you far more "subwoofer" per unit. So if you have reasonably good mains, Signature is a good bet without the commitment of Carbon.

Which one is right for you? That is for you to decide. Will they all work for the high-fidelity gain most people are looking for? Yes, undoubtedly and with resolve, yes.