What filtering For Peerless XLS+PR

[kinser]

After i took 2 months to think about, I decided to get the XLS Sub over the Boston Acuostics Sub, the XLS has a much better value to the money, and observing both sub's T/S paramaters, the XLS is a better peforming sub in my eyes.

So, i ordered the Peerless XLS 830500 12" sub, and the 12" PR with 425g of whight.
for an amp, i have 4/6x OPA549 on 22-0-22 550VA xformer.

What filtering should i use? 4th order low pass or 2nd order low pass? same goes for high pass filter, which will be cutting at about 18Hz.

This will be the 2nd sub+amp i am building, and due to that fact that i am using the XLS, i wand evrey thing to be right, so that i can enjoy the sound.

Thanks,
David Resnik

[kinser]

anyone?....

[tinitus]

I have been thinking about a hybrid sub filter with maybe 2nd order active and additional passive filtering at "higher" frequencies
Problem is that "higher" frequencies is still pretty low and may call fore bigger components

AudioConcepts(ACI) have used an interesting combination of two variable filters, but it seems they keep it more secret now


Maybe this can be of some use

http://sound.westhost.com/project116.htm

http://www.groundsound.com/kits.html

[kinser]

Passive is not an option for me, as they cost alot for the parts.

Ive' been reading a little bit on 2nd and 4th order low pass filters, understande that 2nd order is 12dB/Octave and 4th order is 24dB/Octave, but what does that mean? that the cuttoff will be steeper on the 4th order?

Baisicly, the plan is to cross between 50Hz - 150Hz (more or less) high pass at 17Hz or 18Hz to limit both driver's excursion. also added with be ESP's 8 band Sub EQ, becuase my room acustics are not the best out there..
but i do not know what to use, or how do design this kind of filter, with high pass, low pass and phase control.

David Resnik

[tinitus]

Excuse me, but you have ordered the drivers without knowing the differense between 12db and 24db, yet still want to design your own subamp with advansed facilities - I would say that you are very brave

Maybe a plateamp will save you a lot of trouble and money

[kinser]

Just Realised that i wrote "Orded" :S .. sorry for the mistake there, i ment that i am going to order them, as the 830500 is not in stock yet, and have not done all my research. i dont buy thing with out looking around for info first, thats why i am here..

no matter how many times i try to understand the diffrence betwenn a 12dB filter and 24dB filter, i just cant seem to understand.
Ive seen on a few threads that people recommend a 4th order LPF for vented main speakers.

Could you try expaine to me the diff' between the two?

Thanks,
David

I wish i could go with a plate amp, but cant buy them here, and i can't import from overseas, tax is way to high on them (on the subs i will have to pay 32.5% import tax =[)

[richie00boy]

The order of the low-pass filter will depend on your main speakers. 4th-order (24dB/octave) for vented and 2nd-order (12dB/octave) for sealed. I'm with the other guy here that if you don't yet know something as basic as filter orders then you have your work cut out.

I really can't see the point of an active filter with additional passive. Just make it all active, it will be cheaper and work better.

I'll probably have the board designs you need on my website soon, but you might find ESP's boards good for you.

The dB/octave refers to the rate of roll-off of the filter, so a higher number is steeper.

Personally I'm not a fan of paralleling chip amps, and you will probably have to do bridge + parallel to get the swing you need. Although I suppose if you have a surplus of chips then...

[kinser]

thanks richie00boy,
you cleared some things up for me! on a schematic i can tell the diff' between 2nd order and 4th order, but what was not clear is what each one was for, and how they roll off.
I realy would like to get these drivers, as all i have read here and on the net it good things about them.


does the same go for the high pass filter? 2nd order? (becuase my mains are sealed) or is it something else?
BTW, never planned on going passive filtering.. and regarding the amp, the plan was and is to brige-parallel the chips..
Thanks,
David Resnik

[richie00boy]

The high-pass filter can be what you want. It's the low-pass filter that must be a certain order because it has to match the rate of the main speakers roll off. Sealed speakers have 2nd-order response and vented speakers more often than not have 4th-order response.

Depending on how you use and design the sub, you might not even need a high-pass filter.

[kinser]

Well,
I was doing some simulating on WinISD Pro, 830500 Sub, with 830548 PR (425g), added 200g to cone mass = 625g in a 40L box, with input of 200 watts, both the driver and passive radiator pass Xmax limit at just about 16/17Hz, thats why i want to put a high pass at 17Hz - 2nd order Butterworth filter. which keeps the excurtion under the limits.

David Resnik