4th order basics

[ptcary]

Are these basic assumptions correct?

2:1 ratio ported to sealed

Port tune 45-65hz

Larger port area better?

I have at least 27 cu ft to work with. 9 sealed and 18 ported enough for 2 18"s? 2 15"s? Fi Q?

[ptcary]

2200 watts

[ptcary]

Ok emailed Fi and they say 2 18" Q's with high QTS option will work, but I need to tune to control a peak in the 50-60hz range. I have read that a 45hz tune is low for a 4th order, do I need to tune that low to control the peak? vs say a 55 hz tune.

What do you guys think?

Edited March 7, 2011 by ptcary

[matt402]

that box would be too big for 2 18s, in that space u could fit 3 or maybe 4 18s.

for tuning hi 40s or low 50s would be good.

Edited March 8, 2011 by matt402

[ptcary]

How is it to big? I can always build smaller. Fi said it would be fine. Q18"s spec 4 cubes sealed each on the smaller side of their recommendations.

Please elaborate.

Edited March 8, 2011 by ptcary

[ptcary]

Ok I have been reading a lot and emailing Fi. I now see that my intended ratio and that large box would have been really peaky - not what I wanted at all. So thanks for steering me into more reading. Think I am on the right track now, just have to play with the calculators some more.

[fecupe2001]

4th orders peak around tuning frequency, smaller sealed area allows you to use more power, 2:1 ratio plays a very large range of frequencies, 3:1 ratio is a little bit more peaky but are louder!

I dunno about a 18" sub, maybe 2.5 cubic feet on the sealed chamber and 6.25 cubic feet on the port area with 16 SQ of port per cubic it´s what i would do with 2200 watts