|WikiProject Professional sound production||(Rated C-class, Mid-importance)|
Resonant bass noticeable
"Because of the complex frequency dependent loading, ported enclosures generally result in poorer transient response at low frequencies than in well-designed sealed box systems. Whether or not the effects of this in a properly designed system are audible are debatable."
I was surprised by this, as I've always thought it noticeable. Because bass reflexes produce resonant bass from the port, this has 2 noticeable effects:
- Firstly resonance takes time to build up, thus the low bass is always time lagged
- Resonance also does not die down instantly, so the low bass does not have the tight temporal control that a closed box has, rather it is a wolly vague soft and ill timed thing. Sounds fine for easy listening but performs poorly for 'harder' music.
I read some miss assumptions,
The designer can make many mistakes. You can't say a Bass reflex has poorer transient response, there are several variables.
1) It depends on a right port circumference to be > 30% of Sd good air load no air noise. To small circumference port will sound boomy (resonant).
2) And use a driver with the right parameters for BR. Low QTS about 0,45-0,25 and QES. (Only indication)
3) With low resonance frequency 20-30Hz so the speaker has good air load down to 20Hz by the bass reflex port tuning. So it can't resonate at any audible frequency.
The air load is caused by the opposite resonating air in the port, to the backside off the driver. And will also reduce the cone extrusion at the tuning frequency, benefit low distortion and good controlled drive of the voice coil (motor) at tuning frequency.
4) low BR-tuning brings the group delay to very low frequency's so that isn't audible <20ms (lower then 10msec would be even better).
5) Use efficient drivers so there is less energy storage in the driver/loudspeaker system that could cause a resonance.(driver high SPL small cone-extrusion by big circumference Sd)
When you do it right you have a transient response like a horn loaded speaker and also the sound. And more open dynamic sound than a closed box system.