Ive recently created a vented subwoofer enclosure of volume 80L tuned to ~35hz.
Im using two 58mm.D x 120mmL ports (flared) with my two speakers
specs for the 10 inch speakers are:
-Nominal impedance: 4 ohms (both 8ohm coils in parallel)
-Power rating: 200WRMS (total for both coils at 4ohm)
-Sensitivity at 1W@1m: 87.31dB
-Voice coil resistance (Re): 3.5 ohms
-Resonant frequency (Fs): 24.38 hz
-Mechanical Q factor (Qms): 2.639
-Electrical Q factor (Qes): .337
-Total Q factor (Qts): .299
-Equivalent volume (Vas): 73.19Lt
-Cone Area: 0.0346 sq meter
-Voice Coil Diameter: 50mm
-Xmax: 10.5mm
Speaker dimensions: A 260, B 246, C 240
The ports seem to sound fluttery when it gets to really high volumes. Is this because they arent big enough? I really would have thought that two FLARED ports were big enough for this enclosure. The speakers seem to distort at high volume levels as well (only in this enclosure). Does this indicate that there is too much free air for these speakers to be working in or does it indicate that vented enclosures are not the way to go with these speakers?
Can anyone highlight any potential reasons for my problems?
thanks,
lach
Im using two 58mm.D x 120mmL ports (flared) with my two speakers
specs for the 10 inch speakers are:
-Nominal impedance: 4 ohms (both 8ohm coils in parallel)
-Power rating: 200WRMS (total for both coils at 4ohm)
-Sensitivity at 1W@1m: 87.31dB
-Voice coil resistance (Re): 3.5 ohms
-Resonant frequency (Fs): 24.38 hz
-Mechanical Q factor (Qms): 2.639
-Electrical Q factor (Qes): .337
-Total Q factor (Qts): .299
-Equivalent volume (Vas): 73.19Lt
-Cone Area: 0.0346 sq meter
-Voice Coil Diameter: 50mm
-Xmax: 10.5mm
Speaker dimensions: A 260, B 246, C 240
The ports seem to sound fluttery when it gets to really high volumes. Is this because they arent big enough? I really would have thought that two FLARED ports were big enough for this enclosure. The speakers seem to distort at high volume levels as well (only in this enclosure). Does this indicate that there is too much free air for these speakers to be working in or does it indicate that vented enclosures are not the way to go with these speakers?
Can anyone highlight any potential reasons for my problems?
thanks,
lach
Make sure you are not driving them too hard below 35Hz. You might need a good sharp high pass filter here. 18-24 dB/octave? Below the tuning frequency the port becomes a king sized air-leak. The wheels suddenly and completely fall off. 
The vents are too small, bassbox recommends ~115mm dia vents for that 10mm xmax, I'd use 90-100mm dia minimum.(flared)
Turbulence means that the vents are too small. Distortion means the drivers are being driven too hard - if you change the box to a sealed box that will limit the driver excursion, but you will also lose a lot of bass and you will get the distortion back when you turn up the volume anyway. The only way to get less distortion is to turn the volume down!
The tuning of this box seems quite high, given the fs of the driver is fairly low. Is it for music only? I'd expect a tuning closer to the fs of the driver would work better. The problem with tuning too high above the fs of the driver is you can get an ugly bass hump - that should show up in simulations though.
cheers,
Paul
The tuning of this box seems quite high, given the fs of the driver is fairly low. Is it for music only? I'd expect a tuning closer to the fs of the driver would work better. The problem with tuning too high above the fs of the driver is you can get an ugly bass hump - that should show up in simulations though.
cheers,
Paul
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