4th order port question

[oldschoolboomer 10+ year member]

building a 4th order for 8 concept css-10's. using the carstereo.com 4th order calculator, I know the ported section needs to be 3.24 cubes tuned to 58hz. it doesn't do port calculations, so i am using re's calculator for that. my question is about the port area. whats the rule of thumb? is it @1/3 of cone area?

Click to read more...

 

[oldschoolboomer 10+ year member]

nobody knows?

 

[oldschoolboomer 10+ year member]

bump surely somebody has some knowledge. Isn't this caraudio.com?

 

[oldschoolboomer 10+ year member]

did i accidentally stumble into nambla.com?

 

[fearof85 10+ year member]

I would run 4-5 cubes sealed and 10 cubes ported w/ as much port as you can get away with.

EDIT-lower tuning to around 46-50 hertz as well.

Drew

 

[Cabin_Pressure 10+ year member]

How much Xmax do the tens have?

 

[80INCHES 5,000+ posts]

building a 4th order for 8 concept css-10's. using the carstereo.com 4th order calculator, I know the ported section needs to be 3.24 cubes tuned to 58hz. it doesn't do port calculations, so i am using re's calculator for that. my question is about the port area. whats the rule of thumb? is it @1/3 of cone area?

no

use the biggest port u can possibly fit in ur ride

i hope that 3.24 is for 2 subs

80

 

[galacticmonkey 5,000+ posts]

Definately needs to be bigger. Go with around .6-.7 sealed per sub and then 1.2ish ported per sub, with around 20-24in^ of port per cubic foot of ported airspace. Tune to around 45-50ish hz.

 

[oldschoolboomer 10+ year member]

How much Xmax do the tens have?

a half inch

 

[oldschoolboomer 10+ year member]

Definately needs to be bigger. Go with around .6-.7 sealed per sub and then 1.2ish ported per sub, with around 20-24in^ of port per cubic foot of ported airspace. Tune to around 45-50ish hz.

gln305 says these subs get sloppy in more than .5 sealed. concept recommends only 1 cube ported, so I would assume these sizes would be too big. Or am I missing something? Here are the ts parameters:

Fs = 26.1 Hz

Qms = 4.34

Vas = 1.678 cu.ft

Xmax = 0.472 in

Qes = 0.377

Re = 3.2 ohms

Z = 4 ohms

Pe = 250 watts

Qts = 0.347

1-W SPL = 85.38

 

[oldschoolboomer 10+ year member]

when I use an f3 of 36Hz, I get the following numbers for one sub:

sealed 0.445

ported 0.396

tune to 56.98

boost 2.36 dB

passband 36-90.2Hz

Qbp 0.76

when I try lower f3's it tells me my boost is negative 1.xxx dB.

Try a different calculator? Please enlighten...

 

[oldschoolboomer 10+ year member]

did some more research. carstereo.com's port area calculator says a minimum of 320 sq. inches of port for 8 10's with 12 mm xmax in a 4th order.

 

[galacticmonkey 5,000+ posts]

You dont need a calculator to design a bandpass.

 

[oldschoolboomer 10+ year member]

I built one around 12 years ago for 2 jbl gtx 15's. I just guessed on everything. @ 4 cubes sealed into @10-12 cubes ported in a blowthrough. The port was the blowthrough. @ 6" x 22" 6" deep. Didn't know the tuning I just made the port as big as I could. The bass flexed my windshield, shook the doors and steering wheel to the point the striker plate was starting to rip. Windows of stores would flex when I got within 15 feet. All on 500 watts. Only problem was it would only play between @10 and 35 hz. I want the volume and efficiency in a more usable range. The goal is tons of 40-45 hz. Can you help me out?

 

[oldschoolboomer 10+ year member]

bandpass bump