sealed design prevent sagging?

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I plan to do build a small enclosure sealed sub in the near future. I wish to do down firing. My only concern is gravity pulling on the cone all the time when it is off. I am inclined to think however that a properly and completely sealed enclosure will keep the driver centered as the vacuum created as the cone falls will counteract the gravity and keep it in place. Thoughts or experiences regarding this?
 
Good thinking but wrong - lol

The fact that the enclosre is sealed has nothing to do with how much the driver will sag.

It really depends upon a number of factors and some drivers are more suitable for down firing than others here's a LINK to a good article on how to see if the drivers you are considering would be good candidates for down firing
 
Hi,

A small and sealed subwoofer is very unlikely to have cone sag issues.

FWIW though a driver that does sag can be built with an offset coil
to make it specifically optimised for downfiring, and / or some cheap
drivers are notably assymetrical when tested, and a bit of sag is OK.

A lot of basic drivers tend to to move towards the magnet as
average position under heavy drive, due to magnet assymetry,
and downfiring can counteract that effect somewhat.

Some drivers are simply not sealed enough for the air to act
as a spring short term, some are, but long term sag is not
affected by the air in the box, air diffuses through surrounds
and paper cones, just like your car tyres going down.

rgds, sreten.
 
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Thanks everybody, I will be moving with downfiring. I plan to keep it for a long time (years and years) but using the formulas provided in the link above (thanks by the way), both provide under 2% sag. The leakage will be as minimal as I think it can be as the driver has a one piece poly cone and heavy rubber half roll surround. Thanks for all the points of view!
 
I plan to keep it for a long time (years and years) but using the formulas provided in the link above (thanks by the way), both provide under 2% sag. The leakage will be as minimal as I think it can be as the driver has a one piece poly cone and heavy rubber half roll surround. Thanks for all the points of view!
I have a down firing one piece poly cone neoprene half roll surround sub in my kitchen.

After around 14 years, it appears to have around 2mm sag, probably half of it's Xmax.
That said, it still seems to sound OK, though I'm not paying much attention in the kitchen ;).
 
I have a down firing one piece poly cone neoprene half roll surround sub in my kitchen.

After around 14 years, it appears to have around 2mm sag, probably half of it's Xmax.
That said, it still seems to sound OK, though I'm not paying much attention in the kitchen ;).

I wish I had a sub in my kitchen.. :(

This has 14mm one way, so I have a little room for sag anyway. Thanks!
 
Ummm... a whole lot depends on the mechanical stiffness of the suspension and the mass of the cone. The mass of the cone is related to the Fs figure.

A driver with a rather unstiff suspension and high Xmax will likely sag over time, how much time is where the issue is.

I've had drivers that were stored sag. Rotating them in their boxes is good practice.

The other issue with downward firing is the effect that the floor has upon the sound, and the distance to the floor... sometimes it works out well, sometimes not so well...

_-_-
 
I understand and agree. I know front vs down firing is a whole different and highly debatable topic (I'm ok with going there and discussing it here..).

I prefer the looks of front firing and sometimes feel like down firing transfers too much energy into the floor, and suffers from the effects of compression and loading if there isn't enough room under it. I just feel like mechanical driver noises are more eliminated by the floor (assuming carpet of course) and thus the sub is less localized.. I'm not worried about localizaton from cabinet resonances as the cab design will be 1.5" thick on all sides braced, but just feel the down firing is more forgiving in placement.

I also would want the front firing facing out and forward, because I'm kinda nuts with symmetry, and murphys law says then that it will sound best with the driver facing a corner so the amp and wiring will all be exposed..just because that's the opposite of how I want it..:D
 
You could do like this:

Use dual drivers instead, smaller if you don't have a need for extreme SPL and build the box around them. Wired out of phase of course.

You will gain vibration cancellation which is awesome for a sub, you will also gain massive even order distortion cancellation which is even better, especially as copper rings doesn't do much in sub drivers down low. PP subs like this are awesome =)
 

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but just feel the down firing is more forgiving in placement
At sub frequencies it makes no difference if your sub is front, up, down or side firing - Room modes are room modes and if you have issues that way you will have to contend with them by varying your sub placement, room treatment or both. Going with multiple subs, IMHO, works best "if" you have serious room mode issues.
 
You could do like this:

Use dual drivers instead, smaller if you don't have a need for extreme SPL and build the box around them. Wired out of phase of course.

You will gain vibration cancellation which is awesome for a sub, you will also gain massive even order distortion cancellation which is even better, especially as copper rings doesn't do much in sub drivers down low. PP subs like this are awesome =)

Interesting..only have one driver though.. What is the calc for determining the necessary volume of the cavity and area of the opening? I assume that it would be like a bandpass if too small..
 
At sub frequencies it makes no difference if your sub is front, up, down or side firing - Room modes are room modes and if you have issues that way you will have to contend with them by varying your sub placement, room treatment or both. Going with multiple subs, IMHO, works best "if" you have serious room mode issues.

Totally agree that at sub frequencies it makes no difference, but crossovers aren't straight dropoffs and the driver moving isn't always silent. Also, your output, expansion, etc. will vary if firing into the room vs floor, corner, wall, etc..some scenarios making almost a quasi horn (not always a good one either)..
 
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