bass cab design help

[slr 5000]

hi all
im trying to sim my driver (vifa ne315w-04) and come up with a vented design to mate to a ss 2905-9900 an ss 18w 8531g and am having a little trouble

the top of the design is troels gravesens jensen and uses his passive crossover

for the low end ive substituted the revelater bass driver(to expensive) for the vifa mentioned above and have a mini dsp to cross the bass over to the mid at 200hz as per troels original design and have 80lts max volunme for the bass driver as the cabs are already built ,i can reduce that volume if need be to watever will work the best

now ive been using unibox and 80l gives me fb 33.5hz and f3 30.76hz with a 10.59cm diam port x 16cm long

xmax is reached at 26.8hz for 150w

can someone please look over this for me or offer some advice ,it seems ok to me but im still a noob and dont want to muck it up

also what should i be looking for as far as port speed goes ?

any way thanks in advance for any help any one can offer
cheers sheafer

 

[slr 5000]

gday all
here are some graphs from unibox ,i think it looks good so far but i,m hoping those with more experiance than i can advise
cheers sheafer

 

[slr 5000]

it seems to be a balancing act between fb,f3 ,port speed and driver excursion
ive tried to keep the f3 as low as possible whilst keeping the driver away from xmax in the usable range and port speed as low as possible also

i can use the minidsp peq to filter /cut any frequencys i need as well it seems to be very flexable

i hope i,m on the right track
cheers sheafer

 

[slr 5000]

heres another design ,seems to be a little better as far as cone excursion ,port speed ,f3 and fb goes

comments please ,i need to know if i,m going in the right direction

 

[slr 5000]

the port size and length is also more realistic for this design
the cone ecursion stays under xmax and port speed stays below 24ms
the fb point is as low as i can get it at 26hz and fb is 33hz

cheers sheafer

 

[slr 5000]

please help guys
i need to finnish this design

should i pick the lowest tuning i can get or go for say 30hz fb
should i go for a flat tuning or peak and what is a realistic power level to set in unibox to model with ,ive been using 150w but i see others using 50 or so watts

cheers sheafer

 

[PeteMcK]

re:'it seems to be a balancing act ' - yes, and the balance depends on what you're using the speakers for, which you haven't told us. Home theatre - tune low; Music, tune a bit higher; High volume - worry about port size, low volume, port size isn't much of an issue... A link to the specs of your woofer would help too

 

[slr 5000]

hi petemck
here is a link to the bass driver

http://www.d-s-t.com.au/data/Vifa/NE315W-04.pdf

the system is used for 2 channel music so i would like nice accurate bass but i also enjoy the kick of ported designs

the system is driven by icepower asx2 modules in btl mode so 500w per bass driver

here is the top cabs which are running off troels passive crossover design and also run from icepower ax2 modules in btl mode so 500w per cab

Jensen-

cheers
ps please forgive my first post it is a little hard to read

 

[PeteMcK]

Fb of 27 Hz in 80L looks good to me, any higher gives a bass peak, to be avoided

 

[sreten]

Hi,

Forget about f-3dB, instead optimise for F-6dB and F-10dB, this will compromise
F-3dB but forget that, you will get lower port tunings and better transient
response, and a more room gain friendly roll off than with F-3dB.

Best ported tunings are not flat, they roll-off from quite high slower than sealed.

Simple sims using WinISD indicate 80L sealed, Qbox 0.5 works well, and
the same box tuned to Fvent=18Hz gives IMO the best vented response.

rgds, sreten.

 

[slr 5000]

g,day all
hi sreten and petemck

i will try your suggestions and see how it looks

a few more questions for you all

1/ what power level should i use for the modeling in unibox ,is 50w ok

2/ what should i look for in the step reponse graph for a good result

3/ i have read in the elsinore thread that a good starting point for bass reflex is to aim for fb/f3 = 1.2 to 1.3 , any oppinions?

4/ what box stuffing should i model with ,i can choose between no fill ,minimal fill ,heavy fill and lined walls ?

i think no 3 will achieve what sreten is saying about a more room freindly rolloff

here is an example using joe rasmussens recomendations ,f3/fb =1.27

 

[slr 5000]

here is the step response graph

cheers sheafer

 

[slr 5000]

g,day all

here is another box model fb/f3 is 1.33 so bass should be nice and tight
74 l cab fb 23hz f3 31hz response peak is low at .31db

port length and dia is also manageable at 390mm x 90mm

sim is with walls lined no fill

cheers sheafer

 

[slr 5000]

and here is the step response

 

[slr 5000]

and also spl