A-hole
Banned
good question. I dont know either but I can guess it has to do with the most efficient way to cool off the coil while keeping the subs mechanical limits un molested by the force of air created by the cone movement. I personally think that the pole vent seems more practical. but I have seen subs with both. ventalation on the spider landing and pole vent. I think that is what they are called. I have even seen cones with holes in them under the dust cap.
Just my thoughts. I honestly dont know the thruth. who does? chime in...
Just my thoughts. I honestly dont know the thruth. who does? chime in...
Phoenix Risen
10+ year member
OG.... Original Ginger
there are far more categories than just that, but. subs with out pole vents are (generally) more geared towards spl and burps than daily use/abuse.
having a pole vent lets the sub breath and helps to keep it cool, which comes in handy when playing for long periods of time.
having a pole vent lets the sub breath and helps to keep it cool, which comes in handy when playing for long periods of time.
Bettr n' Revrse
5,000+ posts
I do what I want
Very good question... Kinda strange when you see motors like the 9500's that will take a ton of power but dont have them...
RAM_Designs
5,000+ posts
SketchUp Master
Vented pole pieces are mainly to let the back pressure out from behind the dust cap. A lot of times, in extreme setups, you'll see non vented subs pop off their dust cap. I believe people have done some testing and came to the conclusion that vented pole pieces don't help with cooling that much, and that other venting methods were more effective.
Bettr n' Revrse
5,000+ posts
I do what I want
So pretty much dont have a whole lot of use?
- Thread Starter
- #7
apart from the ability of sticking a biro pen up into the pole vent to push out your dust cap when one of your naughty kids thinks its a big button...lol //content.invisioncic.com/y282845/emoticons/up2something.gif.dd110ecf3ae4b76050d87598f2f8de7c.gif
im thinking there's gonna be less magnet area on the slugs..??, so surely power will suffer slightly (especially on those massive 4'' VC's)
ThaWaxShop
10+ year member
Senior VIP Member
no difference in slug sizes. its just the inside of the pole hollowed out. Ive heard of some subs that actually cool better with thier pole plugged
sundownz
Pro Seller
Supporting Vendor
Pole vents by themselves provide VERY little voice coil cooling... see this Klippel article on blocking a pole vent vs. leaving it open :
Thermal analysis and heat transfer
"Increase of voice coil temperature The figure above shows the heat transfer of a woofer in a loudspeaker system with and without vent in the pole piece. The air below the dust cap will be ventilated through the open vent, and the convection cooling of the coil is low giving a low bypass factor (pink curve in right diagram). After sealing the vent (shown in the left sectional view), the air is pressed through the air gap, and the high velocity of the air particles increases the bypass factor to 50 %"
As far as efficiency... plugging the pole completely with no other means of air release does reduce woofer efficiency a bit. On a Nightshade v.1 (not a super tight gap by any means) this represented a loss of 0.4 dB in my testing -- venting the coil former still maintained most of the benefits of plugging but brought that SPL right back as it released excess pressure but wasn't enough to totally prevent the air bypass over the former. The efficiency loss may be more on something like an MT with half the gap width of a nightshade -- but I didn't go in depth on the MT in testing as it's not my product.
There are a few other ways around the efficiency drop such as venting the cone body (which I don't like) or drilling channels in the pole (Fi/AA do this). These will both help reduce the efficiency drop and help keep dust caps glued on.
A pole vent can be used effectively when combined with other techniques -- you can see two different techniques between our Z v.2 and SA / NS v.2 lines. A third method was utilized on the E8 v.2 as well... all of which provide substantially more cooling than a simple large, open vent (I have done extensive thermal cycle testing to verify them all). You will note in all three the pole vent is quite small, though.
In any event... hope that helps.
Thermal analysis and heat transfer
"Increase of voice coil temperature The figure above shows the heat transfer of a woofer in a loudspeaker system with and without vent in the pole piece. The air below the dust cap will be ventilated through the open vent, and the convection cooling of the coil is low giving a low bypass factor (pink curve in right diagram). After sealing the vent (shown in the left sectional view), the air is pressed through the air gap, and the high velocity of the air particles increases the bypass factor to 50 %"
As far as efficiency... plugging the pole completely with no other means of air release does reduce woofer efficiency a bit. On a Nightshade v.1 (not a super tight gap by any means) this represented a loss of 0.4 dB in my testing -- venting the coil former still maintained most of the benefits of plugging but brought that SPL right back as it released excess pressure but wasn't enough to totally prevent the air bypass over the former. The efficiency loss may be more on something like an MT with half the gap width of a nightshade -- but I didn't go in depth on the MT in testing as it's not my product.
There are a few other ways around the efficiency drop such as venting the cone body (which I don't like) or drilling channels in the pole (Fi/AA do this). These will both help reduce the efficiency drop and help keep dust caps glued on.
A pole vent can be used effectively when combined with other techniques -- you can see two different techniques between our Z v.2 and SA / NS v.2 lines. A third method was utilized on the E8 v.2 as well... all of which provide substantially more cooling than a simple large, open vent (I have done extensive thermal cycle testing to verify them all). You will note in all three the pole vent is quite small, though.
In any event... hope that helps.
sundownz
Pro Seller
Supporting Vendor
Oh... to continue with that a bit. Often times drivers will have a large pole vent to keep air noises to a minimum as higher velocity air does make some noise; or simply because a more effective thermal management system is not needed -- as in the coil will already easily handle the power it needs with a simple vent. I had the same discussion a while back and a good example is the older RE SE... rated 600 RMS but has a decent sized 3" coil -- more power handling isn't needed to justify the rating so the large vent is fine. But... I have plugged those motors up and gained ALOT of thermal handling vs. stock.
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