AV12 vents (1 Viewer)

[Paul Spencer]

I'm designing a vented box for my Stryke AV12. Basically it's a curved 70L box for which I plan to use a 4" vent, tuned around 22 Hz.

I'd like to hear of some experiences with AV12 and venting, or similar drivers. What diameter did you use, did you use flares and if so how big? Who has designed a vent that worked well and didn't have any turbulence?

The design I have in mind is on my site - follow the link on my signature

Thanks guys

 

[Paul Spencer]

Some more background:

I can't get a bigger vent in this box, so I'm looking at some strategies to reduce turbulence:

1. rumble filter to reduce output below tuning and hence useless excursion with turbulence problems
2. generous vent flares on both ends

I also plan to experiment with downfiring the vent. This extends the vent and gives effective tuning of 2 - 4 Hz lower, which means I can use a shorter vent. According to B&W, vent noise is less of a problem when downfiring, however I can see it might be more of a problem unless I place a cone under the vent so the flow is smooth rather than hitting the floor head on. I also intend to experiment with dimples as used by B&W for their vents (similar to golf balls).

 

[Paul Spencer]

No response :O
Surely someone has some experience to share here!!!!

 

[Jack Gilvey]

Hey Paul...cool pages!

I replaced the Shiva in a 141L EBS with my AV12. 18Hz Fb, very-widely-flared 4" vent.Worked fine with the Adire AVA250 plate amp I used, although if you wanted to stretch the driver with more power, you may get noise/compression.


Expound, please...

 

[Paul Spencer]

Jack, how do you find the AV12 compares to the Shiva?

More explanation. Normally people allow at least the diamater of the vent if it is downfiring so it doesn't alter the tuning. If the clearance underneath is less than the diameter, then it can be made to lengthen the vent and thus lower the tuning for a given vent length. With a 140L box you don't need this, but in a 70L box this helps as otherwise its very hard to fit the vent in. As you may have noticed, there is a big difference between 70L and 140L regarding the vent length for the same tuning. This works apparently if the clearance is say 30mm - too little means reducing output and probably turbulence, not enough and it won't lower the tuning effectively.

Note:
70L box, 18Hz tuning, 4" vent >>> 970mm
140L box, "" "" "" >>> 450mm

See how the bigger box means a shorter vent, even though you have more room to fit in a big vent? Hence the difficulty with small vented boxes! Of course you would not tune the 70L box to 18 Hz, that's too low, it isn't an EBS. Instead you would choose more like 22 Hz. The vent would then be 625mm. Much easier to fit but still quite large and needing a bend. Now say the vent were downfiring. Tune it to 25Hz and allow 30mm clearance under (achieved with spikes), so the effective length increase gives you 2 - 4 Hz lower tuning. The vent length is now 470mm - no bends required. My concern is what will be the turbulence effect of the floor at right angles to the air movement. I'm not sure if it will work with this driver pushed to its limits ...