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View Full Version : 4th order bandpass, need some assistance



savagebee
02-11-2008, 04:02 AM
I dont need or really want plans, as this will be an incar build, but I need some help determining the sizes of each chamber + tuning between them

I have a 10 cube + wall tuned to 28(ish) right now, but Im bored and wanting to do another in car build here...

so, please help...

space isnt an issue, as I have well over 20 cubes available for this, and thats without stretching or fiberglass, so that shouldnt be an issue

this will be for 2 elemental designs 19ov.2s
and I will have 2500wrms on tap for this

Im wanting extremely good low end extension, spl is important to me (its a wall with 2 18"s after all) but I dont want the fart box, at all. Overt peaks are something I want to avoid, but I know they will be there with a bandpass design any way

the wall is in a 92 caprice wagon, and it extends to the back of the second row of seats, here is a pic to show the placement of it

http://www.icixsound.com/vb/icixnation/images/2540_168.jpg
http://www.icixsound.com/vb/icixnation/images/2540_173.jpg
thanks yall

here are the t/s specs

Qts: .369
Qes: .37
Qms: 7.5
Fs: 26 Hz
Re: 3.5
Vas: 228 L
Mms: 307 g
Bl: 22.1 T*m
SPL: 90.5 dB
Sd: 1200 cm^2
Xmax: 22 mm
Voice Coil: 62.5 mm

Magnet Width: 8.200"
Cutout Diameter: 16.375"
Mounting Depth: 9.625"
Weight: 42 lb
Total Height: 10.600"
Displacement: .10 ft^3
Outside Diameter: 18.375"

BrianChia
02-11-2008, 04:06 AM
What is your response goal? SPL peak or flat extension? Also what car is it going in and how far up are you going to cut the wall in the cabin.

savagebee
02-11-2008, 04:08 AM
What is your response goal? SPL peak or flat extension? Also what car is it going in and how far up are you going to cut the wall in the cabin.

im sorry, I really should have put this in there...
Im editing the o.p.

Im wanting extremely good low end extension, spl is important to me (its a wall with 2 18"s after all) but I dont want the fart box, at all. Overt peaks are something I want to avoid, but I know they will be there with a bandpass design any way

the wall is in a 92 caprice wagon, and it extends to the back of the second row of seats, Ill find a picture to demonstrate that

savagebee
02-11-2008, 04:12 AM
my current wall was a ***** wall build, i built it outside of the car, so meh..
Im wanting to have something serious here, for this build I mean, Im getting to itch to go extreme again, and this sounds like fun to me

Ive already got to take this wall out, as Im upgrading my charging system, so I figured why not completely trash it and blow a few hundred on wood, right?

savagebee
02-11-2008, 04:14 AM
also, feel free to mock my subs if that makes it okay to give me some pointers

BrianChia
02-11-2008, 04:18 AM
Desired crossover frequency?

savagebee
02-11-2008, 04:20 AM
Desired crossover frequency?

top end @ 80 hertz max, anything around 70 is fine though, I have an undefeatable ssf @ 15, but I prefer to not use it at all, like I said, lfe is the important part of this for me

IamDeMan
02-11-2008, 04:21 AM
also, feel free to mock my subs if that makes it okay to give me some pointers

BWAHAHA I mock the E duhs!

You said to :hide:

savagebee
02-11-2008, 04:22 AM
BWAHAHA I mock the E duhs!

You said to :hide:

:cry:
:sad:


:over it now:

IamDeMan
02-11-2008, 04:23 AM
This is gonna be huge :fyi:

Where is 80 when you need him?

IamDeMan
02-11-2008, 04:24 AM
I wish I could help determine the air spaces but I have never designed one. Did you throw these is BBP to see what it says?

savagebee
02-11-2008, 04:24 AM
This is gonna be huge :fyi:

Where is 80 when you need him?

Im okay with that, with the pregnancy advancing, and my wife not working as much after this month, I need some new projects for getting into the shop, and the coffee table Im doing wont take long

I like huge :)

hopefully 80 will make an appearance

savagebee
02-11-2008, 04:25 AM
I wish I could help determine the air spaces but I have never designed one. Did you throw these is BBP to see what it says?

no, Ive had a hell of time trying to get good results with WinISD, and I dont have BBP

BrianChia
02-11-2008, 04:27 AM
Rear chamber roughly 12 cf, front chamber roughly 7 cf, port tuned 60-65hz. This should yield a fairly flat response from 20hz-70hz. The simulated response curve is actually almost beautifully flat.

savagebee
02-11-2008, 04:35 AM
Rear chamber roughly 12 cf, front chamber roughly 7 cf, port tuned 60-65hz. This should yield a fairly flat response from 20hz-70hz. The simulated response curve is actually almost beautifully flat.

wowza

awesome

Ill play with this, and post some sketchup suff up

how do you think the output would match up with my conventional ported box?
(Wild *** guesses perfectly acceptable)

BrianChia
02-11-2008, 04:37 AM
give me the specs of the ported and i'll try to predict...

savagebee
02-11-2008, 04:37 AM
also, any advice about the ports sq"?
is the rule of thumb apply here the ame as conventional ones?
10 sq" per cubic foot?

would it be 70sq"?

or 190sq"?

savagebee
02-11-2008, 04:37 AM
give me the specs of the ported and i'll try to predict...


okay

10.4 cubes (net)
28 hertz
190 sq" of port
i know how these type of questions are, but I have no experience with bandpasses

BrianChia
02-11-2008, 04:42 AM
is that with the same subs or different? if they are different let me know what you're running

BrianChia
02-11-2008, 04:45 AM
If those are the same subs on the same power, the ported box should actually peak slightly higher from 25-40hz but drop off much faster below 20hz and above 45hz.

BrianChia
02-11-2008, 04:48 AM
I would shoot for at least 150 sq. in. (which will be pretty short anyways).

savagebee
02-11-2008, 04:50 AM
I would shoot for at least 150 sq. in. (which will be pretty short anyways).

what about more?
would that have a negative effect on anything in this type if application?

I was thinking about leaving the port dead senter, and large enough to have access to the subs behind it

I know it wouldnt be that hard to remove the front panel, swap subs, then attach a new one, but for simplicity sake, Itd be nice If I could arrange it to where eveything was available to be left accessible without damaging the enclosure

savagebee
02-11-2008, 04:51 AM
also, thanks for all the help

BrianChia
02-11-2008, 05:05 AM
It would work, you could make the port something like 20" x 20" to access the subs. The problem is that it starts to get a long. A 20x20 port would be about 15" long if the front chamber was 8 cf. You can bump up the tuning a little bit, lose a little bit of midband output, tuning at 70hz with an 11" x 20" x 20" port, 8 cf front chamber.

savagebee
02-11-2008, 05:12 AM
It would work, you could make the port something like 20" x 20" to access the subs. The problem is that it starts to get a long. A 20x20 port would be about 15" long if the front chamber was 8 cf. You can bump up the tuning a little bit, lose a little bit of midband output, tuning at 70hz with an 11" x 20" x 20" port, 8 cf front chamber.

okay, gotcha
how close do I need to be to your suggestions you made to achieve a fairly flat response?

I mean, how much leeway do I have, seeing as how its going to be incar, something will pop up Im sure

savagebee
02-11-2008, 05:13 AM
I just had a moment
Ill just make the port removable, with a large mounting flange, so I can do whatever is called for by the time that comes

dee deee deeeeeeh

thanks again

BrianChia
02-11-2008, 05:24 AM
Yeah, I was actually going to suggest that. I'd probably go for around 200-250 sq. in. still.

Also you could easily experiment with different tuning frequencies that way. Remember that all the specs I've given you are very rough estimates and some fine tuning is still probably needed.

savagebee
02-11-2008, 05:35 AM
Yeah, I was actually going to suggest that. I'd probably go for around 200-250 sq. in. still.

Also you could easily experiment with different tuning frequencies that way. Remember that all the specs I've given you are very rough estimates and some fine tuning is still probably needed.

not a problem, it wouldnt be a hobby any other way lol
thanks a lot for the advice

BrianChia
02-11-2008, 05:40 AM
No problem, be sure to keep us up to date on the build progress. Good luck. :)

savagebee
02-15-2008, 03:49 AM
any more input into this?

I plan on ripping out the current wall in the next week or so