Speaker cabinet construction..

Ports are of use dont toss the babie out with the bath water. But for smaller rooms and close seating. A sealed design will be far less colored and easyer to place. Poor designed loudspeaker cabinets can add much coloration to sound, smearing image since tweeters midrange etc is vibrating on baffle, causes bloom in bass notes since cab walls become a driver, plus reduction in low bass responce. Vibration on cabinets can be controled so vibrations do not cause problems. Seems many loudspeakers go more for WAF then performance and cabinet material choice show this.

thanks for posting a very interesting article.
greg

All the VSA speakers are ported, either front or rear, and employ a tunable transmission line woofer cabinet. The speakers can be tuned to the room by adding dacron filling to or subtracting from the port tube. The speaker can effectively become a sealed enclosure by filling the tube totally. This will tighten the bass but will likewise reduce the amount of bass. What you choose to do depends on your room acoustics.

Few understand that a transmission line IS NOT simply a vented enclosure, and that a properly designed TL can afford some of the lowest distortion bass available. The transmission line speaker was first described and patented in the 1960's. In a classic transmission line, the sound wave from the back of the woofer is channeled down a long pathway filled with a fibrous bundle of wool or bonded dacron, as in mine. This material is packed in deminishing density towards the end of the line, and turns the acoustic energy into thermal energy. In a properly tuned line, only very low frequencies exit the end of the transmission line and extend the low frequency response one half octave below the fundamental resonance of the driver.

In a transmission line enclosure, the back wave of the woofer does not bounce off an interior wall and radiate back into the room through the woofer's cone as in sealed or ported enclosures. These multiple echoes color the sound and can only be eliminated in a transmission line enclosure(IF there is to be an enclosure at all).

There is no pressure in a transmission line to excite strong enclosure resonances. In a sealed or ported box, enclosure resonances can usually only be controlled, not eliminated as in a properly designed transmission line enclosure.

In toto, a well executed TL's extended low frequency response, lack of multiple echoes from the inside of the box, and elimination of wall resonance will result in a very low distortion, fast and extended low frequency system.

Seems many loudspeakers go more for WAF then performance and cabinet material choice show this.

Absolutely. That is fundamentally what the majority of audiophiles plonking down $5K on a showpiece really want. Most are not aware of the colorations and many prefer teh colored sound (what they are used to hearing and expectations are everything)

Ports are of use dont toss the babie out with the bath water.

For sure ports have their merits especially large ones tuned very low can add little coloration, however, if you want to get fanatical about coloration simply take a look at the ort response from prototypical small port bass assisted design speakers from most Stereophile measurement plots and you will often find what is audible port output (distortion above 1%) up as far as the lower midrange.

In the context of extreme measures to reduce cabinet distortion it makes sense to talk about ports also....so WHY does the article ignore this? IMHO, since none of the discussion is breaking much new ground, it seems to be a very selective discussion clearly intended to be marketing material couched as science and technology.