Why do some drivers have a "pole vent" and some dont?

[banginAltima]

To Pole Vent, or not to Pole Vent, that is the question.

In all honesty, it has alot to do on how the drivers cooling system is designed. Just because it doesnt have a pole vent does not mean it is a better, or an inferior driver to another that does or doesnt have that characteristic. most drivers that do not have one, have additional cooling channels machined into the motor structure to actually channel the air around the coil better to force a wind tunnel affect to help cool the coil in a more efficient fashion.

Look up Fi's Bp option that is offered on the SSD and Q series, kind of an example of what is done to help increase the cooling affect...

He is one fart smeller.....I mean smart feller...

This is the correct answer.

[banginAltima]

In addition to what others have posted, in some subwoofer designs the lack of a pole vent can also increase magnetic strength in the bottom plate by putting more metal around the coil. I believe I read this from some Fi article maybe on ***?

I would like to read that article.... Can't help but think why anyone would want to increase the motor force of the bottom plate... Seems like it would cause the coil to bottom out.

[E a r t h]

imo pole venting these days are used mainly to reduce the pressure under the cap so it doesnt blow it off.

many better ways of cooling the coil, useing the basket and top plate gaps or channels for air to flow through

[loganberry]

i have always had this question too, asked around a little bit and never got a clean answer, a friends bl 18" gets hot quick and smelly quick, signal isnt clipped and i got to thinking why does it have a screw/bolt in the spot where the pole vent was, the answer i got was this, without a pole vent the air is being forced back into the subwoofer and comming out the slots around the voice coil and any other exits, which i thought COOL that works great if the sub is cool, helps keep it cool, but as you get going and friction arises wouldnt it "in theory" cause the sub to get hotter and stay hotter? i mean if the sub is warm and gettin hot, the air not being forced out the back of the motor but being forced back inside of it, wouldnt that hot air thus make things hotter? im sure i could be on the totally wrong track and sorry if i am, just a question i myself would like to get cleared up

[Forevrbumpn]

Only person who hit it more than 75% correct was Decafs second posting

There is a better magnetic field around the pole piece when it is solid, meaning more Bl- Strength- Proven and tested.

I was talking to one of the engineers years ago at DD, and he said they made a 9500 sub with a solid pole piece gained a bunch of Bl, gained about 2-3 db using all the same parts, swapping subs only, (gained something like 0.5-1db overall- mic tested) but decided against it, because at that time, there wasn't any great cooling ideas.

The company I worked for, we did the same testing, also found higher Bl, and higher efficiency, but also went against that idea, and just went with tighter pole piece vents, like 0.75- 0.5" vents, over the standard 1"

Now you got companies like Fi who do a good job with machining of the pole piece, and top plates to allow more air flow, and other companies try "Direct cooling" which I think is gay- 5 -6 small holes in the wrong area isn't the best idea in the world

So for a daily street beater you might want a better cooling option, or do Fi's cooling, which seems to work, but competing only, who cares, solid for that extra little bit of out put

basically a catch 22, but for a half db gain, guess thats up to the user?

[E a r t h]

i have always had this question too, asked around a little bit and never got a clean answer, a friends bl 18" gets hot quick and smelly quick, signal isnt clipped and i got to thinking why does it have a screw/bolt in the spot where the pole vent was, the answer i got was this, without a pole vent the air is being forced back into the subwoofer and comming out the slots around the voice coil and any other exits, which i thought COOL that works great if the sub is cool, helps keep it cool, but as you get going and friction arises wouldnt it "in theory" cause the sub to get hotter and stay hotter? i mean if the sub is warm and gettin hot, the air not being forced out the back of the motor but being forced back inside of it, wouldnt that hot air thus make things hotter? im sure i could be on the totally wrong track and sorry if i am, just a question i myself would like to get cleared up

if you look at a standard pole piece, the coil rides along the outside diameter of it and the pole vent blows through the inside. to me thats not a great way to cool the coil.

backplate gap cooling imo is a better method vs a standard pole vent

some manufactures like dd even have holes in the former to bypass airflow through it and the top plate channels. in their application the pole vent actually aids in real cooling abilities. this is a prime example of pole venting aided by other methods together can be beneficial for cooling

obviously all manufactures approach it differently, but a standard old style pole vented motor from a classic standpoint is not efficient by itself for cooling.

on the other hand as said already, pole venting is less motor material, thus a lower bl and slightly weaker motor

[Forevrbumpn]

I would hope vented formers is just about standard on any heavy duty coil these days, the 3" and 4" coils I use all have vented formers

[Boon]

Vented former is crucial for not blowing dustcaps off IMO. Still managed it with my 9515