How much excursion will I get.......

[oxsign 5,000+ posts]

get out of a 10" high roll sub with about 1K to them? The subs are in a 2.9cube box (after all displacement). They are down firing, and I'm trying to figure out just how high from the bottom they will need to be to clear without problems. Right now I'm looking at 3", but after the sub is in place that leaves me about 1.5" from the top of the sub/high roll to the floor. Not sure if that's going to be enough. I would "think" I wouldn't get more that 1.5" excursion one way, but i'm not to sure.

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[subzero 5,000+ posts]

what sub are you talking about. Look at the spec on the sub and it should tell you how much excrusion you will get.

 

[oxsign 5,000+ posts]

Their custom built Ssacket recones. No "real" specs to go off of.

 

[ciaonzo 5,000+ posts]

Even if you have the physical clearance necessary, you'll also want to consider the loading effect on the diaphragm if you bring it too close to the floor. To avoid compression/loading/damping effects you want to have a minimum of 75% of the Sd open after full excursion is reached for the air immediately in front of the diaphragm to escape freely. The Sd of a 10" is roughly 57sq.in., so about 42.75sq.in. would be necessary per driver. That would mean roughly 3 inches of clearance on all four sides of the driver.

BUT...

Depending on how everything is set up, you could see gains in certain areas by taking advantage of slot loading effects experienced by a closer proximity to the floor. At the very least, don't make it so that the cone is just millimeters away from the floor at full excursion. That would be pretty restrictive and would actually limit output. It will also put you at risk of thermal compression or thermal failure. You can test this out by taking a driver in free-air and holding it level, very close the the floor, while playing low tones at high excursion. At a certain point you will be able to appreciate the restricted movement of the cone simply because it's too close to the floor.

Play around with it and you'll be able to come up with something.

 

[oxsign 5,000+ posts]

Even if you have the physical clearance necessary, you'll also want to consider the loading effect on the diaphragm if you bring it too close to the floor. To avoid compression/loading/damping effects you want to have a minimum of 75% of the Sd open after full excursion is reached for the air immediately in front of the diaphragm to escape freely. The Sd of a 10" is roughly 57sq.in., so about 42.75sq.in. would be necessary per driver. That would mean roughly 3 inches of clearance on all four sides of the driver.
BUT...

Depending on how everything is set up, you could see gains in certain areas by taking advantage of slot loading effects experienced by a closer proximity to the floor. At the very least, don't make it so that the cone is just millimeters away from the floor at full excursion. That would be pretty restrictive and would actually limit output. It will also put you at risk of thermal compression or thermal failure. You can test this out by taking a driver in free-air and holding it level, very close the the floor, while playing low tones at high excursion. At a certain point you will be able to appreciate the restricted movement of the cone simply because it's too close to the floor.

Play around with it and you'll be able to come up with something.

VERY good info. Thank you.

 

[ciaonzo 5,000+ posts]

You bet, hope it works out.

 

[nauc 10+ year member]

you cant power up the subs and look and get a rough idea?

 

[RAM_Designs 5,000+ posts]

I'd do a double baffle and recess the subs, then go with 3" from the flush piece.

 

[SPLaudio 5,000+ posts]

ur too close. cause if its a high excursion sub it can easily travel 1.250" each way. this will put alot of strain on ur cone and maybe make ur coil rub from cone wobble. because ur almost cupping to the floor.

redo the baffle in the box and counterbore the sub in thickness of mdf 3/4" and it will be fine...