What do people mean by 4th order box ?

[john253a]

Don't have access to my PC for a few days

Try 22-25@5 and 70-120@3

Then play around with the numbers so you get the point flattened out and within 2hz over a 40+hz range

[CleanSierra]

Good review Jefe(not writing that whole screen name). I never took the time to model, and never looked into IF that Obsidian was any good for a 6th. EBP is 29.76 though, optimum for sealed or 4th order.

[bbeljefe]

I'll make it even easier on you Clean, just call me BB. Cause the first two letters are my initials and what most people call me in teh real world. At least, when they're not calling me various four letter words all strung together....

And thanks.

[swishahouse22]

so I guess il draw out a 4th order then so how big should I do each chamber I wanna get this 18 as loud as I can the amp I have for it is a MB QUART FX1.1000 Formula

[rockFord_Expedition]

not gnna lie these boxes are pretty easy to build I guess that's why I have moved to building 6th and 8th order boxes

so I guess il draw out a 4th order then so how big should I do each chamber I wanna get this 18 as loud as I can the amp I have for it is a MB QUART FX1.1000 Formula

I thought you said they were easy?

[bbeljefe]

To be fair, he said they were easy to build, not design...

Here's the Obsidian modeled in a couple 4th orders:

Both of these models assume two 4" round ports, for ~25 in² of port area. Both have vent machs of .02, which is well below the .06 threshold for a free flowing vent, for the 1KW you have to power the sub.

The blue graph is:

Vf = 2 ftⁿ

Vr = 4 ftⁿ

Fv = 40 hz

Vl = 18"

This box extends from -3dB at 20 hz to -3dB at 80 hz but it's -1dB through the high 30s to the low 40s.

The yellow graph is:

Vf = 3 ftⁿ

Vr = 6 ftⁿ

Fv = 35 hz

Vl = 15.31"

This one stays above flat throughout the passband and extends from 19 to 63 hz. It's not a perfectly smooth response but I don't know that I have time to play with it enough to get a perfectly flat line above flat. I did check to see what would happen if you made Vf 4 ftⁿ @ 35 hz and the response flattens out a good bit and, stays +3dB from 25 to 48 hz. Oh and, Vl for that alignment would be 10.74".

I also modeled at 2.5 & 5 ftⁿ, owing to the max manufacturer's recommendation for sealed boxes and the curve was no better than the yellow one above.

Personally, if I had the space, I'd stick that fucker in a t-line and make a beast out of it. You'd need an 11' long line with 202 in² of (port) area but if you could fit it, you'd definitely have a loud as fawk box with the widest possible bandwidth.

I'll be finishing up the one I built for an SA-15 today and will post up a video in my t-line thread.

[Tahoe2004]

I honestly wasnt expecting to see a lot of good information in this page!

What i though that i wouldnt require alot math done i now know that i does require.

But Thanks a lot !!

I really aprecciate all this info that have just left all quiet xD.

Btw i have a question for BB?

Is that red flat response u got on the computer a good thing or a bad thing ?

Thats something i havent got told yet

[bbeljefe]

The red line isn't a response line, it just highlights 0dB. The purple line below it is the -3dB or, 3 db down point, which is where loudspeakers become audibly quieter.

[DylanBunch]

To be fair, he said they were easy to build, not design...

Here's the Obsidian modeled in a couple 4th orders:

Both of these models assume two 4" round ports, for ~25 in² of port area. Both have vent machs of .02, which is well below the .06 threshold for a free flowing vent, for the 1KW you have to power the sub.

The blue graph is:

Vf = 2 ftⁿ

Vr = 4 ftⁿ

Fv = 40 hz

Vl = 18"

This box extends from -3dB at 20 hz to -3dB at 80 hz but it's -1dB through the high 30s to the low 40s.

The yellow graph is:

Vf = 3 ftⁿ

Vr = 6 ftⁿ

Fv = 35 hz

Vl = 15.31"

This one stays above flat throughout the passband and extends from 19 to 63 hz. It's not a perfectly smooth response but I don't know that I have time to play with it enough to get a perfectly flat line above flat. I did check to see what would happen if you made Vf 4 ftⁿ @ 35 hz and the response flattens out a good bit and, stays +3dB from 25 to 48 hz. Oh and, Vl for that alignment would be 10.74".

I also modeled at 2.5 & 5 ftⁿ, owing to the max manufacturer's recommendation for sealed boxes and the curve was no better than the yellow one above.

Personally, if I had the space, I'd stick that fucker in a t-line and make a beast out of it. You'd need an 11' long line with 202 in² of (port) area but if you could fit it, you'd definitely have a loud as fawk box with the widest possible bandwidth.

I'll be finishing up the one I built for an SA-15 today and will post up a video in my t-line thread.

i believe the side that asks for the tuning frequency is the ported side which needs to be the same size or bigger than the box that doesnt ask for a tuning frequency which is the sealed side

[john253a]

On that same graph

Can you post a standard ported box at say 28 and 35

So people can see the differance