6 replies to this topic

[mr_jay_318i]

hey guys,

soooooooo looks like im getting a 12w7 yay!

just working out the box for it and was wondering if anyone has had much experience with them.

jl recommends 38.94lts sealed, which sounds like a pretty decent box.

OR would i be better off porting it and tuning it to the car?

any help would be much appreciated

cheers guys

jay

[broadz]

I run mine (two eights) ported to get that low end extension they are terrific at achieving. If you can EQ the subbass - smoothing that "ported tuning frequency peak" I'de be porting it. Sealed sounds nicer straight out of the box without tuning but the W7s are a lot more fun ported.
With your monster front stage (using 8s) I'de be focusing on that real bottom end achievable with only a handful of subs - W7 being one of them.

[mr_jay_318i]

broadz, on 21 May 2010 - 08:44 AM, said:

I run mine (two eights) ported to get that low end extension they are terrific at achieving. If you can EQ the subbass - smoothing that "ported tuning frequency peak" I'de be porting it. Sealed sounds nicer straight out of the box without tuning but the W7s are a lot more fun ported.
With your monster front stage (using 8s) I'de be focusing on that real bottom end achievable with only a handful of subs - W7 being one of them.

hmmmmmmmmmm........

ill say sealed so far is very smooth and no problems hittin the really lows.

agreed i am going to design a ported box, but im getting the 1000/1 first to then see how it goes.

VERY good volume for sealed and half power. just needs more controll..... I NEED MORE POWER!!

[shiny_car]

Did you have this running at MEASQ Tragas? I should have a listen next time we catch up.

39L sealed models very well, so should be very good.

For ported, I think you'd need to look at something like 2.5cuft/71L nett, with a port tuning the box to ~30Hz. Should still be very good for SQ, and add that fun factor of low, effortless subbass.

[mr_jay_318i]

shiny_car, on 21 May 2010 - 10:33 PM, said:

Did you have this running at MEASQ Tragas? I should have a listen next time we catch up.

39L sealed models very well, so should be very good.

For ported, I think you'd need to look at something like 2.5cuft/71L nett, with a port tuning the box to ~30Hz. Should still be very good for SQ, and add that fun factor of low, effortless subbass.

it went in on Wednesday. sounding like theres a few people that want a listen

sealed is performing better than expected. it mixes real well with the 8's still but needs more power.

thats what i was thinking for the ported.

how do you work out a port for sq??

resonant of the car then work it from there??

[shiny_car]

Resonant frequency of the car is of less importance with SQ. Or at least, any peak at that point should be targeted by your EQ (if you have one).

When modelling the specs (ie: Qts, Vas, Fs; in software like WinISD), I generally aim for a flattish frequency response (the 'gain curve'). The software models the curve as if the sub/box were positioned in an anechoic chamber (equivalent to an infinitely big room); it means the subbass frequency response 'rolls off' on the graph. Whereas, once inside the confines of a car, it is boosted ('cabin gain' or 'transfer function'). This effect is not easily predictable (ie: you can't readily predict the acoustic effects of the car, or the effects of the position/direction of the sub), so if possible you would measure the stereo's frequency response on an RTA, and tune an EQ accordingly.

But, the port (ie: tuning frequency of the box) can be designed to attain a nice smooth, flat graph. Once you achieve the tuning frequency, this dictates the dimensions of the port. For SQ, you typically tune to 30~40Hz (ie: relatively low, compared with SPL box designs).

Another thing to factor in is group delay, which is also modelled in the software. High group delay (ie: >>12ms) can result in laggy sounding subbass for the frequencies affected; it is never equal across all frequencies, and tends to be worse with lower subbass, which fortunately doesn't usually feature in most recordings (ie: under 30Hz).

This screen shot is from using WinISD for the 12W7-3, comparing sealed vs ported.

 winisd.jpg   203.38K   0 downloads

You can see the ported (green) curve extends 'lower' and is 'louder' for virutally all the subbass, compared with sealed (yellow). At 40Hz, ported is over 5dB 'louder' on the graph; possibly more by the time the sub is in the car; the effect of cabin-gain will be to naturally boost the subbass; 'how much' depends upon the car, but the effect should mean the 'sealed' curve actually extends out much flatter for the frequencies below 70Hz (ie: it won't be rolling off dramatically like the graph). In turn, it can also mean the ported box can have too much subbass!

Now, I don't know if that actually answered your question. You may already know all that stuff!

[mr_jay_318i]

Wow rich, cheers heaps.

Haven't had a chance to put it in winisp, but that is a massive difference. And that answered me perfectly...
Now that low end boost once its in the car is what scares me. If its a massive boost, its goin to be hard to eq it 100% out. On that same token i spose if i made a ported box then found that it resonates, i could then use that box as a template to then tune the next one a bit better.
At the moment it must be hitting the 135db mark, which for how it is, thats great. I think ill get the 1000/1 first then decide.
I will make a ported box for the fun factor anyway, just use it sometimes......
Cheers again rich