4th order jeep wall

[Welterc50 0]

OK, 

So I recently aquired a 1996 jeep grand cherokee and am in the planning phase of the project.  I am looking at running a 3:1 ratio 4th order with either 4 15"  or 18" drivers.  The issue I am running into is that I am concerned that the box height will end up too low to mount the drivers on a flat baffle.  With this being said I was wondering if anyone has toyed around with angled baffles. With this setup I was going to do a driver's side port and tune around 45-50hz.  Would this be too much of a hassle and prove to be a nightmare, or should I try to use a more upward firing baffle to fit the 4 drivers (similar to watt's truck but larger and drivers stacked in a 2x2 config instead of 1x4).  By my figures I should have roughly 27 cubes to play with as far as interior box volume.  If anyone has any ideas im all ears (i like getting loud but like lows also).   Planned power is in the 15-18k range, and since my last build ran 12k and only touched 54s, id like to get as close to 60s as I can.  Not really new to box building, just having "writers block".

Thanks,

Chris

[lithium 358]

by 4th order you mean bandpass i assume? why bandpass over a typical ported configuration. wouldn't the smaller gross enclosure requirement be helpful considering you could run larger subs? 

[Julian 641]

A larger "ratio" will normally net you with a peaky response.

You should also model the enclosure around the subs, not the other way around.

[Sencheezy 689]

Yeah, you can try it I guess... or since you have the power, you can try 12" that would defeat your challenge and spread the power evenly. 

[frogcase2002 393]

I think you should work a lot with someone that can help you design a proper enclosure. Just throwing some ratio out there is not going to get you what you want

[Welterc50 0]

Here is the basic idea...  its a 2x4 shell with birch interior..  something like 3:1 ratio or close to it and 1.6 cubes sealed for each 15..  concern is that the height is too short, do you think 3 layers of birch is strong enough, or should I work this and try to fit them all in?

[Fi 4 life 0]

Don't forget bracing.

[///M5 2,833]

Whomever coined the ratio is a moron. Going to waste some wood. Either design a real bandpass or pick an alignment you understand.

[Welterc50 0]

Drivers are 15" crossfire xsv2s. How would you change it?

[frogcase2002 393]

What about the 6 zcons from your sig?

Edited July 26, 2014 by frogcase2002

[Welterc50 0]

Sold with the truck.. working on a jeep.. I guess I just got bored with ported boxes and wanted to push myself to learn something new (thinking that is a crime on here now). The zcon build was good but not what I wanted.

[95Honda 486]

Jeeze...  Nobody is saying thinking is a crime.  What people are saying is think about what you are doing logically and make informed decsions.  When we see bandpass ratios, port area rules of thumbs, RMS questions, etc. it makes the people who want to help think you aren't serious because you aren't doing all your homework.

 

The comments are meant to keep you from wasting time.

 

I remember when nodoby would get butt-hurt on audio forums, it has been a long time...  Lol... (And no, this comment is NOT directed at anyone in particular)

[Welterc50 0]

Any places you'd reccomend to figure this stuff out? This is my 2nd 4th order and first ever wall.. no I'm not an advanced box builder, but I am appreciative of any help given. I don't live by any big builders or have anyone to learn from in person so I try to find out everything on my own or in person, just sucks when you always see conflicting things on the web. Anyways I'll be heading back to the drawing board to get this right.

[///M5 2,833]

As always, first stop loudspeaker design cookbook.

In the meantime, just build a standard ported enclosure. No way, no how you are going to arbitrarily make a 4th order BP that performs anywhere near as well.

[Welterc50 0]

Boy good thing I didn't build that box.. it would've been a one note wonder that sounded like crap. I've been playing with the bandpass.xls spreadsheet (until my book comes in) with the driver parameters and managed to keep the gain under 2.55db and response from 30 hz to 76 hz (both -3 db cutoff). I'm almost contemplating 6th order after seeing how this spreadsheet graphs it all out.

[///M5 2,833]

4th order BP require a REALLY beefy front stage for them to sound even reasonable. And when you design them to do that you realize that they don't have any more output than a standard ported box. 6th order however you can tune for a gain and keep them musically interesting.

Today's music is also tough though as it has plenty of notes so low and high that it is basically impossible to get a 4th order to work.

[Welterc50 0]

That's what concerned me about a 6th, unloading the driver with too low a frequency. I like decaf ' s music with the lows but with a 6th that's dangerous..

[///M5 2,833]

That's what concerned me about a 6th, unloading the driver with too low a frequency. I like decaf ' s music with the lows but with a 6th that's dangerous..

So everyone with a standard 4th order box has a dangerous alignment?

If you like decaf and listen to anything else then a 4th order BP is double dumb.

[Welterc50 0]

My understanding was 4th orders sealed side prevented driver from unloading unlike 6th where having both chambers ported could leave the driver vulnerable. I mean if your lower -3 db is at 30 hz and the upper is 70 if the driver goes lower than 30 hz it risks entering an infinite baffle like state relying on the suspension of driver. Is this correct or is it subjective to series enclosure design ect? Also I found a website that talks about the content of the loudspeaker design cookbook and it says gains over 3 db can be hazardous to the drivers, so in regards to tuning to gain what would you determine your limit as to how much?

[///M5 2,833]

Standard 4th Order is NOT a BandPass. A simple ported enclosure is fourth order. And yes, by your statement a couple posts above you are claiming anyone with a ported enclosure will have problems. Needless to say this is why nearly all sub amps have SSF's.

As for your gain question, not sure what alignment you are referring to. Either way, bandwidth wise there is really no useable gain on a 4th order BP. Not unless you want a fart monster.

[Welterc50 0]

I was referring to 6th for the gain question

[///M5 2,833]

Have you played with designs? Once you model them the answer is somewhat self evident. Going to garner narrower peaks with more gain and less of a nice response. Unlike other alignments though a "gain" is actually possible. With a 4th order BP it is so narrow calling it a gain is a bit of a joke. 3dB is a relatively arbitrary limit, but use the actual response to decide.

[Welterc50 0]

OK, after a bunch of reading and trial and error this is what I've come up with...

I think I want to try the 6th (similar to yuey's layout)..
Specs....

4-15" crossfire xsv2s (Dual 1 ohm)

2 crossfire 8ks 
11 cube rear chamber tuned to 30 hz (going to end up 2-5.5 cube chambers) via 4- 5.5" aeros at 21.82" long

17 cube front chamber tuned to 58 hz with a single 30.5" by 13" rectangular port 2.16" long (router might fix 3 layer front to correct port depth)

 

Looks a bit peaky..lol..  I also tried reversing the box sizes (larger rear and smaller front) and got this..  (red is SBB4 @ 14cube tuned to 32hz for same subs for comparison).. I feel like im doing something wrong still, the larger rear box and smaller front box get a better response IMO..