need advice on box for a xls12 sub

[paulspencer]

For music the XLS is probably better than the Shiva. Shiva is designed more for HT use in larger vented boxes to get more extension and output. Linkwitz considers XLS superior to the Shiva and I'm inclined to agree, although this depends on the application of course.

In your case you need to consider what is good value from available suppliers. You can also enquire about getting drivers shipped.

[shannow]

Well the xls is cheaper for me than the shiva :s but it's a nightmare to chose the best compromised with the xls . A xls sealed isn't efficient and doesn't go deep at all so it needs a port ... on the data sheets they recommend a vented cabinet of 40L , 90mm diameter port 510 mm long (double flared) a tuning frequency of 30hz and a high pass filter Q:0.7 20hz .

[shannow]

Ok i've tried this:
-red it's the shiva sealed 88.5L 1watt
-blue it's the JBL GT4-12 sealed 88.5L 1 watt
-yellow it's the JBL GT4-12 vented 120L 23hz tuned 1watt
-violet it's the xls sealed 88.5L 1 watt (when i change the volume to 30L it barely moves anything....)
All have had a lowpass at 80hz butterworth
And what's interesting is how close the jbl is compared with the shiva . the jbl is slightly less efficient than the shiva but for 1db it's not an awfull lot ... the JBL talked here I can get one easily for £80 .
Is the curve correct and the main idea ? or have I gotten something wrong to say that the JBL and the shiva are the same in a 88.5L box?
many thanks

[richie00boy]

You are on the right track, but what you need to check now is the max SPL available from the Shiva and JBL. At 1 watt you are only testing the efficiency really.

The max SPL will be dictated by the excursion limit and voicecoil thermal power handling.

[shannow]

Well the shiva is i think perhaps better because it has 16mm xmax and 375w per coil 650w total and the JBL has a 12mm xmax and 250w (and on the website it's marqued 1000w max??) but i'll only put a 100 or 150 wrms sub amplifier with it ... so it souldn't make a huge diference , will it? thanks

[shannow]

I've just tried couple different situation whith these two driver on simulation and both relly follows remarquably well the same line they separate sometimes but never over 1.5db witch I think is very good . But do you think it will be alright to use a car subwoofer for a diy subwoofer for hi fidelity equipement ? my two columns I've paid 650£ the pair will it match the quality ? (i'll probably spent another 120£ for the electronics....)
thanks

[paulspencer]

Don't worry about how closely the curves match. If you are doing a sealed sub then you can eq to get the curve you want.

This is how I suggest you approach it.

1. start with drivers that are good value in your location - do your homework, ask for quotes for shipping if required, and look into drivers that are well known to be good value and good bang for buck. I'd stay away from car audio subs for this.

Think Peerless, Adire, Stryke/AE speakers, Dayton, Blueprint

2. model them with the same filters in WinISD pro - include the same crossover for them all, rumble filter and either linkwitz transform or parametric eq >>>> get the response curve you want

3. you might include a 6db parametric boost at 20Hz with a Q of 1 to simulate room gain to make sure it doesn't have a hump in response or that your linkwitz transform has too much eq. When you are happy with the response WITH your guess at room gain, switch off the boost as it will mess up the excursion

4. change the signal level to a power that won't cause overexcursion above 20 Hz - check the excursion graph

5. View the SPL chart - now you are looking at the maximum SPL you can get for a given power input with that driver. At this point you don't worry about comparing drivers on the basis of nominal efficiency or xmax, but on the basis of expected results.

Note: the XLS tends to have a better vented response when room gain is taken into account as room gain counteracts the early rolloff.

When you have done all this you can then compare things properly and make a good decision, taking account of the cost of the driver and the amp needed to drive it as well as the output and extension you will get as a result.

In USA the Shiva is cheaper than the XLS but in Australia it's the other way around. Keep in mind that comments about bang for buck with different drivers are often biased towards what is good value in USA, but it can be very different in other countries.

[richie00boy]

Excellent advice there, Paul. That's pretty much the way I approach it.

Have I convinced you on the vent sizing yet?

[paulspencer]

Originally posted by richie00boy
Excellent advice there, Paul. That's pretty much the way I approach it.

Thanks, I thought so too

Originally posted by richie00boy
Have I convinced you on the vent sizing yet?

*almost*
I can't let you off the hook with linking that article, now can I?

[richie00boy]

Don't worry, I will post it I'm just waiting for a friend off here to send me the scanned pages via email. It's 20 or 30 pages @ 200k each and he's on dial-up, so please be patient