3 replies to this topic

[mc_daly]

hi,

i'm still relatively new to car audio... (as in i've only just got a car, so i've only just started playing with this stuff!)

but i've been interseted in audio for ages....

anyway, i don't have much money, so i'm trying to get some good sounding music into my car on the cheap....

so far i'm running a kenwood deck (with rear preouts only)

sony 6" 2way fronts (for now, they'll be getting replaced with splits in the next few months, probably re/sponse kevlars)

rears are JVC 6x9 3ways at the moment, but as i wont need them for the bass, i may replace them with the sony's as rear fill

i want to add a sub, which will be located in my boot. The entire back seat tilts forward in two parts, and i intend to leave it tilted forward all the time, make up an mdf section to go across the big whole and have the sub fireing into the cab there... (make sense?)

unfortunatly my boot is not very tall, so there's no way i can fit a 12" sub in, but i think a 10 should fit in a very short box.

i've mucked with winISD a bit, and i have these graphs for a Re/Sponse 10" titanium sub - i've only stuck the gain and spl graphs up, if theres ne thing else i should stick up i can - its measured at 1W/1M

the box is 60L and has twin 47mm ports of 206mm length

it'll be made out of 16mm MDF with heaps of braceing (thinking of using a 1" honeycomb internally of maybe 10mm mdf)

although i'd like to have a decent amount of volume, i'm more interested in high quality sound - do these graphs look ok??? it all seems fairly flat, and goes down relatively low - but are they good enough???

many thanks in advance!

sean

(sorry thats so damn long, just didn't wanna leave ne thing out that could be useful!)

[shiny_car]

hey

yes, the 'gain' response-curve looks very good. note though, when it's in a car (as opposed to 'out in the open' which the graph represents), you'll get significant 'boost' to the very-low-end frequencies due to 'cabin gain', which is the natural accoustic boost you get.

it should still go very well and sound nice.

47mm diameter round ports are very narrow. whilst 'narrow' means shorter ports, it also means higher air velocity through the ports, which can lead to audible turbulence, or 'chuff'.

you could consider a single larger-diameter round port, at least 3"/75mm, and preferably 4". you can use pvc plumbing drainpipe for this.

[mc_daly]

yeah, i would like to be able to, but i'm worried using wider ports will increase the port length.

the box is wide, while ebing short and shallow, and is meant to sit underneath my parcel shelf in place of my back seat, so i can sill have my entire boot section that is under the boot lid as useabl space.'

would it be ok to set the port a fair way to one side of the box, and gently curve it 90 degrees to run parallel to the face thats ported?

that way i could use wider ports to avoid chuffing..

sean

[shiny_car]

yes, adding a 90 degree elbow is common practice and a good way to go.

you initially proposed 2 ports, but using a single port will mean shorter length. so i think a better trade-off will be a single wider longish port than 2 narrow ones.

so the unfortunately implication of a wider port is length. :shrugs: