Loudspeaker enclosures Bass Reflex and Sealed Cabinets.
For the old peeps here is a really great article:
McIntosh and the Grateful Dead’s Wall of Sound
There is a lot of intriguing information about speaker enclosure design in books and the internet and the single thing that stands out the most to me is the emphasis on the sophistication in the design of bass reflex speakers. Bass reflex loudspeaker enclosures are ported to get optimal bass. Much of this article is coming from my own experience and I am not an audiophile by a long shot.
Audio Technica AT-SP3X
It is true that a sealed box enclosure is the simplest and possibly the one that can least go wrong. Just possibly!
My first experience was in high school woodwork where I stupidly decided to build speaker enclosures as a project. Of course nowadays we just butt join a couple of MDF boards together – I hade to dovetail all the pine sides to a perfect fit, not a simple task for a person of mediocre ability in the woodworking class.
Move on a couple of years I had the finances to purchase 12″ 8 Ohm Fane drivers and piezo tweeters. It sounded great to the untrained ear coupled to my Autono 125W quasi-complimentary 2N3055 amplifiers. What is important though is that it may have sounded a complete disaster to anyone in the audiophile community, one thing that I can assure you – sensitivity of the speakers were good. In those days 100W per channel was plenty for a small gig. Our ears were still working at optimal performance. Compare this to the modern versions of the 12″ speaker systems used in sound systems. I’ll single out the Atos TS412s for example.
Alto TS412 – 1kW Active Speaker
Plastic enclosures, In total about 1kW per speaker (continuous power albeit Class D). Who would have thought that these enclosures would have sounded so good down in the low end. Just how many audio gear designers have always warned us against the quality of the plastic “boxes”. Well for professional usage they have very little cons, the pros all being around the power to weight ratio. (watch out for that spec coming soon).
Getting back to the point, the original Fane enclosures were sealed boxes and they actually sounded good considering the enclosures didn’t follow standard rules. Actually there were no rules that were followed, looking back the enclosure sizes were most probably a pretty good match for these drivers – by fluke. There was one specific manufacturer of DJ gear that didn’t follow the rules, his two Fane drivers per enclosure always had massive cone flap, either because of the uncontrolled bass excursions or design issues. The sealed box never really had that problem. I recently purchased a home made enclosure system which had two Hybrid 15″ per enclosure. Absolutely ludicrous amount of uncontrolled cone movement below 100Hz -due to a poorly ported design. If one reads the books, the ports on these big speaker enclosures are usually quite a few feet in length and often times 2 ports 6″ (15cm) in diameter. These enclosures definitely did not encourage any form of low frequency resonance, with the added misery of not being able to control cone movement, the final result for the listener was a total disaster.
While we are on the subject of enclosures note that there is a difference between a woofer and a sub woofer, the former has a response curve in the 40Hz to 2kHz region and is usually in the same enclosure as the midrange and high frequency drivers whilst the sub only operates in the 20Hz – 200Hz range. I first noticed the popularity of subs in home theatre systems and the first movie I can recall was Earthquake through a Sensurround system. Although my own recollection was that nobody used subwoofers in the 1970s, everyone now uses a sub for some or other reasons post 2010. Class D amplifiers play a huge role here.
Some interesting websites I have come across, the simpler, the better:
Kick off here:
Elliott Sound Products (ESP) – https://sound-au.com/articles/enclosures.htm
Audio Judgement: https://audiojudgement.com/sealed-vs-bass-reflex/
Eminence: https://eminence.com/blogs/blog/sealed-vs-ported-enclosures article by Anthony Lucas of Bass Gear Magazine
DESIGN
https://www.omnicalculator.com/other/speaker-box