6 replies to this topic

[ubernoob]

I am going to use two Earthquake SWS8 woofers as a computer sub an d I am trying to model a nice small box but it isn't working for me. I know Earthquake say about 1/4 cu ft for a sealed enclosure is the minimum but I want to go for a ported box or a sixth order bandpass(if possible).

Earthquake specs are here-


I don't seem to be able to find a spec for inductance anywhere, will it matter for box design?

Can anyone model a box that comes on no higher than 40Hz and will play to 100Hz. Also the box really needs to be small if that is possible.

I don't know if it is me putting the specs in wrong or what but I just can't get any box to either hit fairly low or have a nice flat response.

Does anyone know what running a pair of subs in an Isobarik configuration will do to total power handling? Having the cone area of one sub and two motor assemblies would have to make the power handling take a massive dive, would it be the RMS rating for one woofer?

Apologies if this is hard to understand, my brain has gone to sleep but my eyes are open.

[Tiger]

For box design, you'll only require 4 items....

Fs
Qts
Vas

And driver displacement/qty.

Thats it, it's then up to program tweaks to sort out the rest, like tuning, cabin gain etc...

[TMM]

It's a good idea to also plug in Xmax and Sd(cone area) and Pe(Power) to check that you won't exceed xmax and affect power handling.

edit: qts of 0.669 and vas of 27L is what is preventing them playing nice in a small ported box. A driver with a high qts like that is more suited to infinite baffle, large closed box or really large ported box.

Isobaric will help because it will perform as if you have 1 driver, but a box twice the size. It won't be as loud as a single woofer in a larger enclosure though (i think?! someone correct me if wrong). Even with an Isobaric configuration the smallest acceptable ported box is around 40Litres, 22Hz.

You'd have better luck finding some woofers with a lower qts (say 0.3 or 0.4), smaller vas and higher Fs if you want them to work nicely in a small ported box. Or just run infinite baffle if the placement in your room allows for it

Edited by TMM, 22 January 2012 - 01:03 AM.

[ubernoob]

Thanks a lot guys, TMM, Earthquake do suggest a horn loaded enclosure that is just 250*250*75mm external dimensions so that is a rediculously small ported enclosure.

I have heard one of these woofers in a small ported box and it seemed to play lower than Win ISD would have you believe but that may have been due to cabin gain(?) as it was in an older Falcon ute.

[shiny_car]

Isobaric: it allows you to have a box half the size compared with using 1 sub; loudness is the same as 1 sub, but requires twice the power (cos you're running 2 subs); so the total power handling is simply the sum of the two subs (ie: double that of 1 sub); the only real benefit is halving the box size; you lose out in all other respects

For that sub, I'd stick with either a sealed box of 1cuft/28L, or normal (4th order) ported of 1.5cuft/42L tuned to 30Hz.

Particularly with sealed, you can either floor-load it (ie: have the box on little feet to raise it off the floor around 2~3" and face the sub directly towards the floor) or position/face it close to a wall/corner of the room. This creates the equivalent of 'cabin gain' which - as eluded to - is natural acoustic boosting of subbass frequencies. As such, the curve you see on WinISD will actually 'extend' lower/flatter, and not 'roll off' so early.

[ubernoob]

Thanks Shiny but Earthquake recommend a max sealed size of 16L which is why I am having dramas, Earthquake say on thing ISD shows something completely different.

I shot Earthquake an email to see what they say, I hate their site there is so much BS on there it's not funny and finding where a product is made is really difficult, bloody Americans!

[RAD]

That SWS 8" does'nt model well... all that you can do is try making their horn design, and pointing it towards a wall/corner like shiny said.

My suggestion all along would be to find a 10" with a low FS and Qts to suit a <1cuft low tuned enclosure.