- Mar 21, 2020
- Montreal, Canada
In my opinion, you build a box to obtain good low frequency performance. By venting a box for a driver with a Qts higher than 0.5, you're aiming for good LF performance at the cost of poorer transient response. You don't gain anything and you might as well keep it sealed. All the experts say so. I have been building speakers for over 50 years. Just get a good loudspeaker building software and you will find the right answers.It is port appropriate because the fs is higher.
It is a relationship between the two.
With higher fs drivers(90-120) higher QTS/QES(.5-.9) is good for ported boxes.
Over .9 would change things a bit but that would be a very unique driver.
Model this driver yourself.
With a higher fs driver you are tuning the port to support what is the upperbass/midbass and not the lower bass region. Therefore the desired QTS/QES parameters are different from when tuning for the tradition bass zone.
In a driver where the fs is lower and the natural response already covers the midbass you would get a peak or boom there, not so in a driver like this where the natural response is severely rolled off in the midbass and needs support.
If this driver was in a small sealed box it would have no bass at all and barely any lower midbass. Completely unsuitable response in this use case.
That's why you need a lower Qts for a vented design. By the way, a high Qts speaker in a small sealed box might still produce some low frequency response, but not as efficiently as the one in a vented box. The purpose of an enclosure is to isolate the back wave produced by the driver from the front wave in order to get a LF response, the proof being that you can get subwoofers in 1 cubic foot cabinets producing low frequencies. The LF response depends on the Thiele-Small parameters of the driver and the box design.