I've a couple of pairs of similar specced 2-way ported bookshelf speakers (5" woofer + tweeter). The ports on one pair expel air at a force that would blow out a candle, the ports on the other pair - almost nothing.
I always believed the theory was that vibration of the air inside the port produced low frequency sound. Subsequently, a cabinet expelling air was tuned too high and the counter was tuned to low.
?
I always believed the theory was that vibration of the air inside the port produced low frequency sound. Subsequently, a cabinet expelling air was tuned too high and the counter was tuned to low.
?
The air mass and port air velocity vary enough from speaker to speaker to be not easy to predict. Too much velocity can result in turbulence. Higher frequencies can be affected by internal damping material.
The port air mass resonates with the volume of air in the box to alter driver loading, and the port air velocity and area radiate outward.
The port air mass resonates with the volume of air in the box to alter driver loading, and the port air velocity and area radiate outward.
overall port area for small bookshelf
is limited.
so yes if the overall port area of both are reasonably the same size.
yes highly likely one is tuned higher.
or if port area is smaller velocity would be higher.
box volume is mainly dictated by the suspension
and tuning mainly by the resonant frequency of the driver.
Resonant frequency of small speakers of course vary.
so 65 Hz be impressive for small drivers. And 80 to 100
not a surprise either.
So one driver might have decent low resonant frequency
one a little higher.
If we measured the impedance curve, there would be no
guessing game. And resonance could be confirmed.
You would either see one is tuned higher.
Or if tune was relatively the same.
The higher velocity port would be because it is
smaller
is limited.
so yes if the overall port area of both are reasonably the same size.
yes highly likely one is tuned higher.
or if port area is smaller velocity would be higher.
box volume is mainly dictated by the suspension
and tuning mainly by the resonant frequency of the driver.
Resonant frequency of small speakers of course vary.
so 65 Hz be impressive for small drivers. And 80 to 100
not a surprise either.
So one driver might have decent low resonant frequency
one a little higher.
If we measured the impedance curve, there would be no
guessing game. And resonance could be confirmed.
You would either see one is tuned higher.
Or if tune was relatively the same.
The higher velocity port would be because it is
smaller
I just found the behaviour interesting. The cabinets and the ports are virtually identical in size. The bottom speakers are good, a regular pair of boomers, the (rear-ported) top speakers - not so much. I can only conclude that the bass drivers in the other cabinets are shite.
