With that driver you can port low, here's a ported design...

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Date: March 21, 2003 at 22:34:58
From: norman bates, [oproxy3.rockwellcollins.com]
Subject: With that driver you can port low, here's a ported design...

Standard Ported
Vb 12.36 ft3
F3 17.48 hz
Tuning freq 17.06 hz
8" Port length 31.81 " long

Ported equations
Vb = qts^2.87 x 15 x Vas
F3 = qts^ -1.4 x .26 x fs
Fb (tuning) = qts^ -.9 x 0.42 x fs

A = 1.463 x 10^7 x R^2
B = Fb^2 x Vb (volume in cube inches)
Lv = (A / B) - 1.463 x R
R = radius of port

I believe passive radiators need to have more area than the driver (2 15s with 2 18s for radiators).
Tuning that low would be like the earthquake sub ($3,000).

Sealed qtc.707 yields a f3=fsb=31.77hz. Corner loaded should produce flat to near 20s.

There ain't crap down there besides organ, cannons, low synth, or bass cds used to show off your system or blow some steam by making your own earthquake. But hey, if you want to, go for it.

This ported alignment will go damn deep, but the box is big ( my 2 boxes of double 18s need 9ft3 each and room for a plenum and a 12" port 14" long, it's 6th order tuned to 26hz for -3db@below that in room and can hit 128db from 28hz up.) and will bottom out Like your qtc .5 at 25hz with the same amount of power as your sealed did, but you can put in more power from 17hz to 25hz, you are not gaining a hole hell of a lot by tuning, as yes you can take more than 100 watts at 17hz if you have enough port area to account for the massive amount of air rushing through the port but it may only take 40 watts at 25hz to crash into the bottom of the magnet.

My recomendation would be multiple drivers in that sealed qtc.707 and slot load them like the bassault by bag end (that costs $8,400, yikes !!!). As you double the drivers you gain 6db (but you need more power). Use 4 of them. If that doesn't work use eight. 6db is not double loud in treble region but it is in the bass region (till a certain point on the fletcher munson curve).

I would want a much larger port, but a 10" port in a 12.36ft3 box tuned to 17hz needs to be 51.5" long !!

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Follow Ups:

Re: With that driver you can port low, here's a ported design... kicker 18's 21-Mar-2003 23:58:46 (11)

I use Eminance (bought on closeout parts-express $100 each) norman bates 22-Mar-2003 01:03:03 (10)

Re: I use Eminance (bought on closeout parts-express $100 each) kicker 18's 22-Mar-2003 01:40:03 (9)

hey norman bates 22-Mar-2003 19:14:02 (8)

Wood djk 22-Mar-2003 20:05:23 (4)

How's it going djk !!!!!! norman bates 22-Mar-2003 21:17:56 (0)

Re: Wood kicker 18's 22-Mar-2003 20:25:50 (2)

Re: Wood mikeported 25-Mar-2003 20:13:12 (0)

Take any advice from djk when you find some.... norman bates 22-Mar-2003 21:20:47 (0)

Re: hey kicker 18's 22-Mar-2003 19:33:54 (2)

still fiending info on my previous post! Please!!! kicker 18's 22-Mar-2003 22:15:28 (1)

there is no 1 exact enclosure...... norman bates 23-Mar-2003 13:37:48 (0)

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