Hi,

I am about to build a sub box for a new pair of subs for my car.

Now, previous experimenting with the positioning of sub boxes in the boot/hatch area leads to a significant difference in the SPL.

Due to $$$ and effort factor, i dont want to build a few different sub box designs in order to see what works best. But i am hoping that there might be others on here who have, or at least know theoretically which one might produce the highest bass (and perhaps even other differences in sound). Nothing extravagent (sp?).

I have come up with 3 possible designs which i could use (excuse the drawing. it took me 2 mins to draw up ). Any others you can think of?

So, just want any info, advice, knowledge, etc etc on this question.

When it comes to things like this, How technical do i need to get? in terms of wavelengths, etc etc?

Please keep in mind i'm not entering any comps, but would like to get the most out of it.

Cheers

Forgot to add:

box is sealed, seperate chambers.

car is kf laser

subs: Most likely 2 x 15", ~400wrms each (if it matters)

Thanks

i would have both drives facing the same direction(1st pic) also mount the ports on the plane as the drivers, if it is a single enclosure(not divided internally) u need to ensure unsure each port is the same distance fom the sub. if one is closer than the other it casues one to unload un evenly...

as for mounting the box in ur car side fron or rear facing thats up to you... probably with a hatch(i kno its a laser but is it hatch or sedan?) id fire rear wards or upwards. sedan also fire rearwards.

if u want spl then port the box, speperate chambers 1 port for each chamber...

for spl most ppl go large ported boxes. build the box to the specs it provides and tune it at around 40Hz i would think...

i choose nubers 1 and 3

What about ports up, woofers upwards?

number 3 looks like it could look pretty good.
it all depends on the loading of your specific car to how loud each setup will be.

#2 will cause cancellation however the cones will load each other which may be helpful if you cram in a lot more power than the subs can really handle.

#1 is easiest to get right.

#3 will probably cause cancellation without the loading benefits.. I'd avoid it.

Hahahahhahahah no attack on you Blackice but i thought the same about facing woofers that way and i was told the wavelength of the sounds the woofers are playing are to long to cancel each other out .

ok Thanks for all the reply's guys.

Poisoner,
Have had ported boxes in the past. Got nothing against them, but want to go sealed this time. Like i said, not really entering any comps, and although this seems contradictary to what i'm originally asking, i'm not after that big ported bass (if you know what i mean)

car is a kf 5 door hatch.


Blackice,

you say that no2 would create a cancellation effect? Do you remember a few years ago i think it was that red 1300 wagon. it had a square tube going through the hole car into the front cabin, with subs on all 4 sides the whole way down the tube. Held the spl record for a while. This works on a similar principle i imagine? However, in saying this, they would have tuned it for 1 certain frequency (rather than a range), and all measurements (ie tube length and X-section widths and height) would have been carefully measured and calculated.

Also, what streetsoundz mentions may have some truth to it? i mean, if v=w x f...eg f=40hz, v=~340, therefore, w=8.5metres. To cancel each other out, it needs to be out of phase, ie 180deg, Therefore, a wall (or surface) needs to be about 4.25m away in which the original signal can reflect off, causing a COMPLETE cancellation. However, at the same time, any cancelling effects is bad, and we are not just worried about a complete cancelling (ie 180deg out of phase).

But i might be completely wrong in what i have written above, as this was more a "thinking out loud" comment, rather than a factual argument. So please correct me if i am wrong.

thanks.

Its one of those things I've tested during Xmas holidays.. it dont work so good.

Like i said i know myself thats facing subs like number 2 it causes cancellation but all the brainiacs on here with no real world knowledge told me otherwise .

ok no worries thanks blackice.

its on those Xmas holidays, where things like this get found out

Looks like i might just stick with the simple, yet effective rectangular box design.

thanks for the reply's ppl.

simple yes. it akes a hsorter tiem to design and build
so spend that time on tuning or making it look nicer with fibreglass or false floors etc...

No 2 is called compound loading, it works very well.

It's commonly used in PA stacks etc.

There is no real chance of cancellation, think about the wavelengths involved.

Phil

Thanks for the reply DD Phil.

Just did a quick search on "compound loading" and yea ive seen the isobaric design before. Never really put the 2 together before though (a enclosure incorporating a "V" like option 2 above, and the traditional push-pull isobaric design).

Anyway, if they are indeed a similar/same concept, the only advantages seem to be a smaller required box. Is this the only advantage? i'm not at all concerned with the size of the enclosure, but more so the advantages of increasing SPL.

If you can offer any info on option 2 (mailny through personal experience plz), that would be appreciated.



Also, just another option (not a realistic one due to the no of drivers reqd) that i'd like people opinions on, esp through personal experience.

cheers