figuring port length

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thatfloorguy

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Joined: May 14, 2009

Location: Ohio, United States

Posted: July 12, 2009 at 10:49 AM / IP Logged

I am assuming you guys would reccommend I keep my day job, as there isn't much call for pot noise models these days!! figuring port length - Page 2 -- posted image.

figuring port length - Page 2 -- posted image.

DYohn

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Joined: April 22, 2003

Location: Arizona, United States

Posted: July 12, 2009 at 11:12 AM / IP Logged

The actual geometry of the port matters far less than the opening size and length. As far as port noise, with that large an opening you shouldn't have audible noise at any power level short of destroying the driver (in a vented enclosure an L7 is power limited to less than 750 watts.) Up-firing should be OK for that woofer as I've seen it done, but I don't know the exact T/S parameters to tell you if that further limits the power handling capability due to sag, I don't understand your statement about "leaving 3" before it hits the deck"?? Do you mean between the face of the woofer and the nearest surface? The L7 will not move that far (indeed no woofer currently available will.)

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thatfloorguy

Copper - Posts: 95

Joined: May 14, 2009

Location: Ohio, United States

Posted: July 12, 2009 at 12:50 PM / IP Logged

Yes from the face of the driver to the bottom of the deck is 3" min 4" at most of the area. I doubt I am getting 750 rms out of the amp. I had 2 cvr 12's in a common chamber ported enclosure one with a bad VC and they never died. They are only 300 each in the ported enclosure. I had just under 4ft^3 for the both combined. So is putting another 1/4" along the inside port walls not a good idea? I thought to use 3" triangular braces to minimize displacement if so.I wasn't aware that the driver facing up will affect the handeling, interesting.Also will I get a smoother responce by attaching polyfill when I resin the interior, or would you not reccomend it in this enclosure design?

thatfloorguy

Copper - Posts: 95

Joined: May 14, 2009

Location: Ohio, United States

Posted: July 12, 2009 at 12:54 PM / IP Logged

I also have not even set the gain on the sub amp. It is still at the lowest setting. I have just been making my adjustments with HU controls and the wired bass boost remote. My digital cap readout says 14.10 volts but I am not sure how true that is. It is really just a big distribution block for my amps, plus I have to pull the fuse@battery if I don't use this vehicle for a cpl days. The stupid battery will discharge trying to keep the cap charged.

DYohn

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Posted: July 12, 2009 at 1:10 PM / IP Logged

re: battery discharging and amplifier gain setting. If the battery is discharging through the cap then you either have a defective cap or it is installed incorrectly. Please read the "How to set your gain" sticky in the Hot Topics forum. Using bass boost to adjust the relative volume level of the sub is one way to fry your voice coils as the amplifier will clip if bass boost is over-used. And you absolutely should not operate your system if there is no fuse on the main power cable at the battery, for safety reasons.

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thatfloorguy

Copper - Posts: 95

Joined: May 14, 2009

Location: Ohio, United States

Posted: July 12, 2009 at 1:49 PM / IP Logged

The amps will not even power on without the fuse. I have just been removing it to prevent my battery from discharging. Once I finish the enclosure I will turn all bass boosts down and adjust the gain. Oh when figuring port length I have been using internal dimensions on the calculator. Is this correct? not adding the material thickness, that is. until final design for displacement values.

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figuring port length

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