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Discussion Starter #1
I have been debating for about 8 months on my new system, and am EXTREMELY happy with the results of my "prototype" vented enclosure. I am currently running a Phoenix Gold Titanium 12 in about 1.9 cubic vented and tuned to 27 hz. Excluding competition cars, i have yet to hear its equal (and even some show cars!!!). Needless to say, I am very happy with this sound. Now, howver, after a few tried and failed attempts to make a suitable enclosure for this that doesnt cost my entire trunk or spare tire (hiere is a pic with two 1.2 cubic sealed enclosures (roughly 2.5 cubic if it was a single enclosure, but you cant fit it through the trunk opening)):




I
am contemplating doing 2 of these subs in an isobarak enclosure. I can go slightly smaller while increasing my response. I will stick with vented and have plenty of power:




so I am just looking for any input (pros vs. cons) on Isobarik enclosures. I am willing to move the amp, but frenkly, I like the way it uses up the "unusable space" between the seats and trunk and its moderately secure there (you can lock the seats in place making it one step harder to get to!). Also, its not really an easy amp to mount anywhere else!

I am most likely going to try something similar to the first picture, but only one speaker will show- the magnet side as it will be a "clamshell" iso.

PS, how do you spell iso barik?


THX!!!
 

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Going to an isobaric enclosure WILL make the box smaller, but it will also be only half as loud as it is now since you'll need twice the power (since there are 2 subs now) you'll be moving 2 motors and there will still only be the displacement fo one sub. If you really want to save space try an Infinite Baffle (free-air) setup. I don't know if the PG Tis will work in IB but 2 Image Dynamics IDMAX12s will sound awesome in an IB setup. When I get my second IDMAX12 I'm going to ditch the awesome sounding, but really friggin' big, 2.6cf 27Hz tuned ported box it's in and do an IB setup.


Paul :thumbup:
 

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Discussion Starter #3
quality_sound said:
Going to an isobaric enclosure WILL make the box smaller, but it will also be only half as loud as it is now ...
I understand I lose efficiency and therefore output, but I am only scratching the surface of my amps power- the gains are pretty much at zero (as is the bass "gain"). I should have plenty of power to compensate for that... whats more, I am running a pretty conservatively rated 1 ohm stable amp (many run well below that) at 2 ohms- I would likely run parallel and go with 1 ohm anyway.

I am more concerned with the intricacies of building this type of setup- what problems will I run into.

I am kind of afraid of infinite baffle- i have heard some amazing systems that way, but also some AWFUL systems. I would hate to cut massive holes in the rear deck only to find I hate the sound and have to patch them up. Maybe I can put the amp back under the rear deck (it fits- BARELY) and rebuild the baffle board between the seats and try that..

IDMAX 12's you say, huh...

hmmmmm.....
 

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I've heard systems wth ALL types of boxes sound good and bad. The downside to an Isobaric box is the space that the second sub takes up outside of the box is basically the same amount of space you save in the box so you'll end up taking up about the same trunk space.

You don't have to cut your rear deck to do an IB install. In fact, unless you use that as a mounting surface you're probably going to end up sealing it off fromthe cabin with a piece of MDF anyway.

The original IDMAX Passat (way back about 3-5 years ago) had 3 of them IB with an assload of power going to them and it did mid 150s at the the windshield. Just something to chew on.


Paul :thumbup:
 

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Lil bigger????? :???: If he wants a good sounding setup (and it sounds like he does) a bandpass would have to be HUGE to get anything close to a flat response with any real deep bass.



Paul :thumbup:
 

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i did a tahoe with 6 IDQ 10's in it that were isobarically mounted and and ported, and holy crap that thing hit like a sledgehammer. It is like having 3 quad voice coil subs. They have so much impact when they hit it is unreal. The cool thing about isobaric is that you run two subs in half the air space as one needs. So a box for two 12's that require 1.5 cubic feet each only needs to be .75 cubic ft to work properly. That is saving a lot of space, and is the reason we went with that setup in the tahoe - about 3 cubic ft box vs a 9 cubic ft box.

As far as construction goes, you can make a cool box using plexi for one side or something, basically you're adding a box inside of the box, and the easiest way (in my opinion) to mount it is to make one of the sides of the box removable and incorporate a seal so you can take the panel on and off, and screw it t together. So you screw one sub in normal, and then remove the panel of the box to screw the other sub in, and it's inside the box. I could draw you a picture if you'd like because that description seems kinda flaky, lol.

Hope This helps,

Morgan
 

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Discussion Starter #9
Seanboy88 said:
Go Bandpass lil bigger but again bigger sound!!! really depends on what you listen to as well :thumbup:
the sub i have (in the interest of using what I already own rather than replacing) doesnt do very well in a bandpass- by the time I get the t peaks out far enough, i have MASSIVE sag in the middle. But you are right, HELLA sound- about 7 to 8 db gain at the top and bottom of the range.

Right now I LOVE the sound (if you have WinISD, map a titanium in 1.9 with 27hz tuning) it STARTS to roll off under 30hz with NO transfer function!

I will likely make my baffle board 3 layers thick- cut 1 out for the bottom sub (counter sink it into the first layer so it is supported by the other 2), make a "ring" of mdf to go between and flip the outside one on top (it will stick out a bit, but not bad i am guessing)- mount them cone to cone.
 

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quality_sound said:
CaptainMorgan said:
The cool thing about isobaric is that you run two subs in half the air space as one needs.
- about 3 cubic ft box vs a 9 cubic ft box.
I think your math got messed up somewhere. :D

Paul :thumbup:

It would seem that way, but really that's just because of two separate box designs where if we did them all normal they would have been 9 cubic ft, but with the isobaric design it came out to about 3....but yeah, you're right if that was the same box design that would have been pretty far from right.
 

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j said:
Seanboy88 said:
Go Bandpass lil bigger but again bigger sound!!! really depends on what you listen to as well :thumbup:
the sub i have (in the interest of using what I already own rather than replacing) doesnt do very well in a bandpass- by the time I get the t peaks out far enough, i have MASSIVE sag in the middle. But you are right, HELLA sound- about 7 to 8 db gain at the top and bottom of the range.

Right now I LOVE the sound (if you have WinISD, map a titanium in 1.9 with 27hz tuning) it STARTS to roll off under 30hz with NO transfer function!

I will likely make my baffle board 3 layers thick- cut 1 out for the bottom sub (counter sink it into the first layer so it is supported by the other 2), make a "ring" of mdf to go between and flip the outside one on top (it will stick out a bit, but not bad i am guessing)- mount them cone to cone.


Your description of the sound of the bandpass you had is exctly opposite of the way a bandpass works. I'll bet you had tons of midbass (most people get midbass and low bass confused becuase they've never heard REAL low bass) and not much low bass.

Just remember that in IB you will reach the subs physical limits sooner so I would suggest less power AND a subsonic filter.


Paul :thumbup:
 

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Discussion Starter #12
quality_sound said:
j said:
Seanboy88 said:
Go Bandpass lil bigger but again bigger sound!!! really depends on what you listen to as well :thumbup:
the sub i have (in the interest of using what I already own rather than replacing) doesnt do very well in a bandpass- by the time I get the t peaks out far enough, i have MASSIVE sag in the middle. But you are right, HELLA sound- about 7 to 8 db gain at the top and bottom of the range.

Right now I LOVE the sound (if you have WinISD, map a titanium in 1.9 with 27hz tuning) it STARTS to roll off under 30hz with NO transfer function!

I will likely make my baffle board 3 layers thick- cut 1 out for the bottom sub (counter sink it into the first layer so it is supported by the other 2), make a "ring" of mdf to go between and flip the outside one on top (it will stick out a bit, but not bad i am guessing)- mount them cone to cone.


Your description of the sound of the bandpass you had is exctly opposite of the way a bandpass works. I'll bet you had tons of midbass (most people get midbass and low bass confused becuase they've never heard REAL low bass) and not much low bass.

Just remember that in IB you will reach the subs physical limits sooner so I would suggest less power AND a subsonic filter.


Paul :thumbup:
I dont understand... I am just describing the response curve of a 6th order bandpass; it usually shows impressive output "peaks" (often 8 db or more!) at 2 frequency points (the larger the volumes, the closer the peaks are to the tuning frequencies). If I spread the peaks out to about 90 and 30 hz by playing with the volumes of the enclosures and the tuning frequencies, the middle usually sags pretty bad, often 10 db or more. So, I end up with great sound in a very narrow range(s) with fast roll off at the bottom and top, but weak bass in between.

Here is the curve if I put a single Titanium 12 in a 6th order band pass, the front chamber is 0.25 ft3 tuned to 75hz, the rear is 2.1 ft3, tuned to 25 hz

 

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If your peaks are at 30 and 90 you will actully have pretty good low bass, nothing from say 50-70 and another big bump in the midbass. That's all relative though. Even that "sag" in the middle will still be WAY louder than "flat". So you won't have "weak middle" but even more excessive output at the tuned frequencies.

This must have been a HUGE gain box to exhibit this type of behavior as well. Most bandpasses will look like a mountain with the top chopped off when viewed on an RTA and it sounds like yous had "horns" on either end of the "mountain top". There was a serious problem with that box.

Just to nitpick, I think you meant "dual reflex bandpass". The whole "order" thing was some marketing crap some tech department made up years and years ago. You can make a 6th order IB setup if you want.


Paul :thumbup:
 

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The graph actually popped up this time and it reaffirms my feelings that your box had serious problems. I'll bet if that front chamber was larger the response would have improved dramatically. What's even weirder is that there wasn't much gain (for a bandpass anyway) for the amount of bass you lost in the middle. No wonder it sounded terrible.


Paul :thumbup:
 

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Discussion Starter #15
quality_sound said:
The graph actually popped up this time and it reaffirms my feelings that your box had serious problems. I'll bet if that front chamber was larger the response would have improved dramatically. What's even weirder is that there wasn't much gain (for a bandpass anyway) for the amount of bass you lost in the middle. No wonder it sounded terrible.


Paul :thumbup:
Paul,

this box was never built- it was only called up to show what i was describing. Below is what I have now and LOVE it, but want to try and make something that fits my trunk (right now i have a big cube sliding around in my trunk). The pics at the very top show a previous attempt, and I may do something similar- but the cones you see would be covered by another set of speakers showing magnets (in isobarak). I have sold off the x-max's and am running a single titanium, but i may either by 1 or 3 more, depending on how crazy i want to go with this...

 

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I know how an isobaric works. :crazy: My point WAAAAAY back was that the since you'lle have an entire motor assembly exposed the overall space savings will not be as great as you think. Yes, the "enclosure" will be smaller, but the sub motors will take up space and on top of that you'll probably not be putting stuff near them so you don't mess them up which will increase their "size". Most of the time an isobaric won't help much unless you do like Morgan and are making a HUGE box to start with.


Paul :thumbup:
 
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