4th order isobaric box/es.

Post by **smgreen20** » Mon Jan 16, 2012 8:15 pm

I'm using WinISD to look at output graphs for a 4th order isobaric pair concerning my TREO SSi12's. So far I'm liking the looks of things. Anyone know of any other free programs on the web that I can use?
Also, how do I save/copy the screen so I can post the graph here?

Post by **smgreen20** » Mon Jan 16, 2012 8:23 pm

Okay, upon further review, I see that WinISD is showing a 4th order bandpass. I don't want that. So, anyone know of any site that will let me "build" my own? Looking for something that would tell me chamber size, port size........This would be 3 boxes so to speak. The sealed chamber for compound sub, the chamber of the main sub, and the chamber of the port.

I'm not sure I'm conveying what I mean.

Mr. Wild · Post by **Mr. Wild** » Tue Jan 17, 2012 12:55 am

It doesn't make sense. How do you end up with 3 boxes with one "isobaric" (compound is the correct term) pair of subs?

Are you going for 4th order bandpass or vented?

In a compound configuration there is no main sub / compound sub. The pair of subs act as a single driver.

Winisd tells you chamber size and port dimensions.

In windows you can punch "print screen" and then paste in Paint and save.

wooferdog · Post by **wooferdog** » Tue Jan 17, 2012 4:23 am

on a iso set up don't you just half the box volume that 1 sub would normally use ?

Post by **smgreen20** » Tue Jan 17, 2012 5:48 am

Let me add the word 4th order Isobaric COMPOUND. I forgot to add compound. Here's a pic of the "3" boxes I was referring to.

I know how I want it laid out in my head, just don't know box volumes. need help with that. That's what I'm looking for.

avalanchels · Post by **avalanchels** » Tue Jan 17, 2012 7:29 am

Model a 4th order bandpass and if compound loading or using an isopair, cut the sealed volume in half. That's all you have to change...the ported section remains the same. There should not be much space at all in that 3rd section you are referring to.

Sent from my ADR6400L using Tapatalk

Post by **smgreen20** » Tue Jan 17, 2012 7:59 am

Thank you. That's what I needed to know.

Mr. Wild · Post by **Mr. Wild** » Tue Jan 17, 2012 10:47 pm

Actually the ported section is halved too when using compound.
Just use winisd and use 2 drivers and select isobaric / compound. You'll see. You can compare box volumes by modeling eith only one driver.

Port tuning is quite critical in a bandpass box. I usually multiply the port lenght winisd calculates by *0,7, otherwiswe the tuning ends up too low and the sound will be sloppy and slow.

Post by **smgreen20** » Wed Jan 18, 2012 5:51 am

Are you sure you half the ported chamber? You tune the box, for a given output, so halving the ported chamber would also change the port. Just want to make sure. It'll be a bit before I start on it. I'm waiting on a friend of mine to get back with me. He bought a metric ass ton of 7/8" x 4' x 4' (literally like 150 sheets) MDF for dirt cheap, he said I could have some. And I also need to draw up the plans still.

Mr. Wild · Post by **Mr. Wild** » Wed Jan 18, 2012 11:05 am

I modeled a bandpass sub with winisd using one sub and then acompound pair. Sure enough both chambers were halved in volume. Thats the only point in using compound, minimizing box size. The pitfall is porting, because you are forced to use smaller diameter ports.

Is compound a necessity?

Post by **smgreen20** » Wed Jan 18, 2012 1:59 pm

As I'm reading the "Loud speaker design cookbook", I've discovered that a 4th order compound isobaric box is what I'm after. I want SQ and need to save as much space as I can. On top of that it has the lowend extension out put I want. I run ported so I can get the extra umph out of the lower end that a sealed can't do. Along with more clarity that a compound box delivers.

I have an extended cab FS truck so I don't need a ton of out put to get loud, and some of the music I listen to has heller bass notes that are loud and low (Like Chimaira ), and I want that extra umph at the lower frequencies that a sealed cannot provide.

wooferdog · Post by **wooferdog** » Wed Jan 18, 2012 2:50 pm

i would just do the isobaric box sealed for space savings and throw a bass cube at it.

Post by **ttocs** » Wed Jan 18, 2012 2:55 pm

funny that is what I thought earlier. I have yet to find a system that with a sealed enclosure and a cube that could not make me happy.

wooferdog · Post by **wooferdog** » Wed Jan 18, 2012 2:58 pm

you get the cube dialed in and it's low end for day's

Post by **smgreen20** » Wed Jan 18, 2012 4:32 pm

I have a cube and it's installed, I just want to do it w/as little eq possible.

wooferdog · Post by **wooferdog** » Wed Jan 18, 2012 5:21 pm

bass cube is 1 band. can't get much smaller than that for a eq. the iso pair will play lower than a single sub in the larger box.

Post by **smgreen20** » Wed Jan 18, 2012 6:43 pm

I know it is, but I use the BC for "mood" adjustment or for when songs don't have enough low end (like Metallica's pre Justice albums) I turn it up and vise verse for songs with to much low end.

Keep in mind, I also have an Audio Control DQS that I will also use to "set and forget" on the sub channel. the BC would be just for minor tweaks from song to song.

I'm going to do a few more WinISD charts and see what I get.

Post by **smgreen20** » Wed Jan 18, 2012 7:48 pm

This is what I'm trying to design, the 2nd one down IN the box outlined/titled "Single Reflex - Band Pass Enclosures"

http://www.the12volt.com/caraudio/boxes4.asp#3

00goobs · Post by **00goobs** » Wed Jan 18, 2012 8:40 pm

Funny, on that site he says the band pass enclosure is less efficient than a typical ported enclosure. I was always under the impression that a band pass enclosure was the most efficient enclosure because of the front and rear "loading" of the speaker...

Mr. Wild · Post by **Mr. Wild** » Wed Jan 18, 2012 10:51 pm

A ported box the same size as a bandpass box (sealed + ported chambers put together) is more efficient in the low bass region. But you cant beat a bandpass box for upper bass kick.

When I make a bandpass box I usually design it with two ports. I then install three of these tubes winisd has specified. If the tuning seems too high, I just stuff a towel in one port. Gives you tunability. Other trick is to use one port which is too large in diameter. Later the diam can be reduced by lining the port with thin stiff camping matress.

Mr. Wild · Post by **Mr. Wild** » Wed Jan 18, 2012 11:46 pm

I tried modeling TREO SSi12.22 and 12.44 with Winisd. Which model do you have?

I'm afraid you'll have to forget about compound bandpass.
The ported chamber is about 8 or 10 liters (SSi12.22 / SSi12.44). You will be hard pressed to get a port larger than 2" diameter in there. 3" diam already translated to about 20" lenght. That's not nearly enough for a powerful 12" driver.

If you use just one driver in a bandpass box the ported enclosure will be about 16 or 20 liters. A 4" diam port would be about 18" in lenght. I would not use anything smaller than 4" diam and even thats small if you have lots of powa.

If you want small and powerfull, porting becomes impossible. Just put the pair in a 50L liter sealed box.
Compound is nuts even in a sealed box. Too small to sound good.

Post by **smgreen20** » Thu Jan 19, 2012 5:52 am

I have the SSi12.22's.

The ports displacement can, and will have to be, added to the internal volume of the box, so I would be able to put the SSi's in one.

I know what I want and am willing to experiment. I wont be throwing away the box I currently have so if this doesn't sound good, or for whatever reason, I can put them back in the current box. All I'll be out is time and very little in materials, which for me I have plenty of laying around.

The 4th order compound isobaric box gives me what I want. All I'm after right now are the definitive answers on volumes, front and rear (ported).

Lowcountrypsulion · Post by **Lowcountrypsulion** » Thu Jan 19, 2012 6:52 am

smgreen20 wrote:I know it is, but I use the BC for "mood" adjustment or for when songs don't have enough low end (like Metallica's pre Justice albums)

"Shortest Straw" is ridiculous when played on a good system with a tight sub. I'm only running my Punch 12 with an M25 and the Punch sounds like it's going to explode!

Post by **smgreen20** » Thu Jan 19, 2012 7:43 pm

OK, I think I've got it figured out. I was questioning halving the ported side of the enclosure, but to those that said to, I apologize, you were correct.

I did a few different comparison tests that I hadn't done yet and I stumbled upon one that led me to find that to be true. Sealed rear chamber= .825 cf, front ported chamber= .464 cf tuned to 41 Hz.

The one that I stumbled on that led me to believe what WinISD gave is correct was exactly double the volume and the tuning freq was only .18 Hz off.