To bandpass or not to Bandpass

[audiofanaticz]

iirc 51 or 54 cubes for four 18s in my tahoe, does a 155-156 on music with 2 saz-4500s and a high 157 with 4 saz-4500s, Didnt gain much doubling the power, even after playing with ports, woofers just get instantly hot in the first 10-15 seconds with all 4 amps  at .7 , while with 2 amps at .35 it will play all day long.

[tboorn]

a lot of info in here and its all spot on, another thing with a bandpass is the space you need, over a simple ported box youre looking at probably 1.5x box size. i built a series tuned 6th for 2 18s in an impala and it was dirty, did 155+ at 24. but the box could have easily housed 4 18s ported

[06RTCharger]

7 hours ago, audiofanaticz said:

iirc 51 or 54 cubes for four 18s in my tahoe, does a 155-156 on music with 2 saz-4500s and a high 157 with 4 saz-4500s, Didnt gain much doubling the power, even after playing with ports, woofers just get instantly hot in the first 10-15 seconds with all 4 amps  at .7 , while with 2 amps at .35 it will play all day long.

Fort Knox lookin lol looks badass

[the_garynator]

14 hours ago, kalilac619 said:

I run a series tuned 6th for 2 18s....currently have Zv4s in at the moment and I've played with the rear port twice and front port about 5 times (shrinking and making larger) just to get where I'm happy with it.So like others have said it takes work but can be done...space wise can not be sacrificed what so ever...mine is about 35 cubes total net for 2 18s but have a bandwidth from 15hz-about 65ish hz....does a 155 sealed on the Dash at 29hz and a 154.2 sealed on the dash at 52hz which is my upper peak...from 20hz-57hz it'll do a 151+ sealed with the strongest bandwidth from 25-55(does a 154+ sealed) crack the driver window and it becomes a different beast and some of the peaks change will do a 156.7 on the dash window down and a 156.4 in the head rest all at 33hz.a 158.2 in the kick at the same frequency if that's your sort of thing...mostly the low frequencies pick up with the window down does a 153 at 20hz window down and a 155 at 25hz....sorry for the rambling but what I'm getting at is it took about a year and some playing with some things to get it to this point,so if you like testing and tuning and have the space I say go for it......p.s if I shrunk the rear chamber to get the rear port tuning as close to the front chamber tuning as possible I've gotten a 159.1 at 45hz sealed on the dash but only has a usable bandwidth of about 3hz MAX before woofers look like they'll jump out of the box 

The reason tuning close didn't work well is because the front chamber tuning of a series tuned 6th acts like a 4th order in the fact that it acts as an acoustic filter. It is used to tune the high frequency cut off. Think of it as a low pass filter. As you get close to its tuning frequency, output starts to drop off. So basically just as your rear chamber starts to reach its usable bandwidth, the front chamber starts to limit the output.  I've got some more detailed notes on how tuning them works from other posts I've made in the past I'll post later when I have time.