# using 4 subs in isobaric.

phase1
Member - Posts: 7
Joined: July 11, 2015
Location: Indiana, United States
Posted: July 21, 2015 at 7:38 PM / IP Logged
There is like no information about using more than 2 subs in a sealed compound isobaric enclosure so out of curiosity, thought I'd ask. I know with 2 subs in iso, it cuts the box size in half but also degrades efficiency so it makes me wonder if this holds true using 4?
1. So if 2 subs in compound isobaric cuts the VAS in half, then can you do 4 subs in the same enclosure, say cone to magnet configuration, would it cut the VAS into 1/4th?
2. If 2 isobaric loaded subs cuts the output by 3db's, would 4 cut the output by 6db's or would it raise it back up 3db's?
3. What if the 1st sub faces forward and each behind it is cone to magnet so that all 4 subs are facing the same direction, each behind each other in a row....could you add a tuned port behind the 4th sub without increasing box size or would the final chamber need to be larger or half of the required ported enclosure requirement?
phase1
Member - Posts: 7
Joined: July 11, 2015
Location: Indiana, United States
Posted: July 22, 2015 at 6:21 PM / IP Logged
No one knows anything about them?
haemphyst
Platinum - Posts: 5,054
Joined: January 19, 2003
Location: Michigan, Bouvet Island
Posted: July 28, 2015 at 8:50 PM / IP Logged
There is no benefit at all to go to 4 subs in a compound chamber. Mathematically, sure it works out that the enclosure is 1/4 the required enclosure size, but what abut all that chamber required to house 4 compound drivers? The only volume that is divided by 4 is the volume behind the last (or first) one driver, it's NOT the entire enclosure volume. By the time you add it all in, allowing space for adequate clearance... <dave shakes his head>. This, in addition to the fact that you now need four times the power to make the output of one driver. Yes. You only have the surface area of one woofer, right? How will the others cause any "sound", if they're buried?
Isobarik or not, an enclosure tunes the same way, and it doesn't matter how many woofers are acting upon that air volume. X volume tunes to Y frequency with Z vent. Period. 100 woofers or one.
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice.﻿ You should write it down."
DYohn
Moderator - Posts: 10,741
Joined: April 22, 2003
Location: Arizona, United States
Posted: July 29, 2015 at 10:01 AM / IP Logged
Only if you compound all four drivers as one is the VAS cut to 1/4. If you have two sets of 2 ISO aligned, then the VAS is cut in half. But as haemphyst says, there really is very little benefit (especially in a vehicle) of doing this. You'd get more bang for you buck with four drivers mounted conventionally even in too small an enclosure. Plus (and please don't take this the wrong way) your questions indicate that you don't really understand isobaric loading, so I recommend (especially if you want to vent it) that you don't do it.
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