Can somebody please check this build ?

[fishchris1]

First off, I decided to hold off until at least this Summer to do the huge T-line with two 15" mounted in an isobaric, clamshell configuration.

 

But for now, im just going to run the same two 15" subs isobaric, clamshell, but in a regular tuned ported enclosure.

 

I talked to a tech guy over at Parts Express for like 30 minutes, and after plugging in a bunch of different options, he came up with the following for my two 15"s....

 

4.4 cubes, tuned to 27 Hz, with a 6" diameter, 21" Aero Port.

 

Kind of surprised me, as I always heard that an isobaric setup required a lot less airspace ? 

 

Again, if somebody could double check this, it would be super appreciated.

 

Oh, the exact subs, if you want the specs, is;

https://www.parts-express.com/dayton-audio-rss390ho-4-15-reference-ho-subwoofer-4-ohm--295-469

 

Also, I'm giving them just shy of 1000 wts RMS, per the birth sheet of my Rockford Fosgate amp...

[CstrokerV]

They require less airspace then 2 subs ran side by side.. but when isobaric is used it uses the airspace of around one sub not 2...  what do you mean by clamshell only type of iso I’ve seen is face to face or rear to face... what do you mean by clamshell?

[fishchris1]

Face to face is also referred to as a clam shell. 

I know that isobaric requires less space, but I thought it was 1/2 of that, of one subwoofer, or 1/4 of what the two side by side would need, no ? Also, I believe this is an exact formula.

Anybody want to confirm or deny this ?

[shredder2]

I'm no expert but I always thought the only benefit of isobaric was a lower response, I thought it will have the same effective amount of cone as 1 after all. 

I've heard half as a space requirement as well but like any enclosure its probably power dependent to some extent, maybe the given space and low port area is because of the planned power and effective amount of cone?

Either way I'm tuned in... I haven't thought about isobaric since the late 90's

 

[CstrokerV]

It’s not exactly half and dependent on Other things just like any other box... and I had a page saved about these boxes but can’t seem to find it... I’ll look some more sometime this week

[fishchris1]

Hey guys, so after calling and talking to another tech guy, for about 20 min + chatting with another guy who was using the WinISD program, and bouncing around between about 5 different iterations, I'm 95% sure this is what I'm going with.....

 

2.7 cubes, tuned to 27 Hz with two, 4" x 36" ports (which will have to extend about 6" from the 31" box But that's okay. I think it will look kind of whacked , and go along great with the 15" sub sticking out of it too lol

 

BTW, the tech guys told me it could be as big as 4.4 cubes because I was only pushing 1000 wts to them. Had I ran 1600 (the max rms rating) it would be more like 3.5 cubes. I'm only going as small as 2.7 cubes to keep the ports from being rediculous long. Even so, they don't quite fit "all" in the box.

 

This model looks really good to me though. Pretty flat all the way to 35 hz or so with only a slight hump from 35 down to 27 Hz, then a steep dropoff. My amp has a 25 hz sub sonic filter anyway.

 

Anxious

[fishchris1]

Anybody ? Would love to have a second opinion.

 

To simplify it, here's the straight scoop;

 

2.7 cu ft

Two 4" x 31" ports

Two of these subs mounted isobarically (face to face)

....getting just shy of 1000 wts.

https://www.parts-express.com/dayton-audio-rss390ho-4-15-reference-ho-subwoofer-4-ohm--295-469?gclid=Cj0KCQiAxfzvBRCZARIsAGA7YMwV8bjG90Xas3BIkTdzsIXb8ghrFWLcHpLJUwCM_dnqM-IC9Y7TRxQaAhi4EALw_wcB

 

Unless somebody tells me, it will sound bad, and here's why.... This is going to happen very soon....