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Discussion Starter #1
I have a 2007 Fahrenheit GTI and need some advice since all my other systems have been coming out of the trunk. As the title say's "What is the best box configuration for a hatchback?" I'm trying to figure out what's the best setup Sub's up/Port up, Sub's up/Port back, Sub's forward/Port up, or.....? ? ? Port tuning will most likely be 28-30hz max. I listen to mostly rap and really need to get a lot of volume at or below 32hz since I will also be running 8" subs for everything above 40-45hz.
I have about 9.0cu.ft. to work with, not including subwoofer, port, or bracing displacement. I'm still undecided on Subs but I'm leaning towards a single 15"/18" or two 15's. I am running a T1500bdcp on the substage and an old school a/d/s M860 on the mids & highs.
 

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In a GTI, even a single 15 in a ported box will be excessively loud. I'm not saying you should go smaller, I'm just saying that you certainly don't need to go that big for good bass. Hatchbacks provide a lot of cabin gain, getting a lot of bass is easy. I just finished a ported box for my 2014 GTI, tuned to 28hz for a 10" sub and don't have any desire for more output.

Are you trying to retain any space at all? There is no reason to low pass a sub at 40hz only to have another sub take over, any decent subwoofer will play up to 100hz without any issues. The more speakers you break up that bandwidth among, the more challenges you'll have with level matching, and phase. It's an unnecessary complication that won't be an improvement over using a single setup to cover the entire low end. I also think you'll be surprised at how high the low frequencies actually are. What most people think is a 30hz note is usually closer to 50hz.
 

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Sounds like a nice setup - I would be looking at a single Sundown X18v2 in as big of a box as you can fit (manufacturer recommends 7 cubes) tuned low like 26 Hz since you already have the 8s. Although I do agree with gijoe that you really don't need those 8s unless you are putting them upfront somehow. If you skip the 8s, I'd just go with the recommended 30-32 Hz tuning. Most people are running sub and ports up in these kinds of systems.
 

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I don't think there is a "best" setup. Its all about personal tastes. Their are so many different ways subs can be setup. I prefer ported... at least, comparing the ported enclosures I've built and listened to, to sealed enclosures. Now I'm working on a "tiny" enclosure for two Isobarically mounted (clamshell) 15"s with a passive radiator... which is actually, pretty close to the same as ported. But I'm super impressed with the initial results (from a test enclosure).
 

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In my 16v gti, I ran a single 15 for years although it was sealed not ported. That was a great sounding car. Basically comp set up front and sub in the hatch on two amps and eclipse head unit. That was pre dsp, so that car would sound far better knowing what I know now vs when I had the car
 

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Orange Crush, nice!

two 15's to run from 30-45hz plus two 8's? Have you reinforced the hinges on your hatch door :)

Outside of the good comments you already received above, you will surely get in to wave cancellation all over the place and possibly hear less than gain more. One subs sound wave will impede others etc. Clean it up! My recommendation would be two good 12's (like the Sundowns suggested) with 500w a piece (which you already have) and nothing more. In my opinion you will not benefit by feeling or hearing anything more with 15's or 18's. IMAX movie theaters have two 18' (made by JBL) subs behind the screen. You are putting that in your car. 500 seats vs 4 ;)

Also, as a previous VW owner watch out for their notoriously poor and superbly expensive alternators. Although, with T1500bdcp you already upgraded that.
 

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Discussion Starter #8
In a GTI, even a single 15 in a ported box will be excessively loud. I'm not saying you should go smaller, I'm just saying that you certainly don't need to go that big for good bass. Hatchbacks provide a lot of cabin gain, getting a lot of bass is easy. I just finished a ported box for my 2014 GTI, tuned to 28hz for a 10" sub and don't have any desire for more output.

Are you trying to retain any space at all? There is no reason to low pass a sub at 40hz only to have another sub take over, any decent subwoofer will play up to 100hz without any issues. The more speakers you break up that bandwidth among, the more challenges you'll have with level matching, and phase. It's an unnecessary complication that won't be an improvement over using a single setup to cover the entire low end. I also think you'll be surprised at how high the low frequencies actually are. What most people think is a 30hz note is usually closer to 50hz.
I have had 15's walled tuned to 32hz in my last trunk build and it got very loud & low. But Like a "Crackhead" It just wasn't' enough, I always wanted a more. Well to be honest it did everything I wanted above 32hz but I need more volume below that. (that's the only reason for considering the 18")

As for a single 10" I know for a fact it is not enough because I've been running a single 10" in a prefab box for the last two years while I dumped cash into performance upgrades, and I just installed 2-10"s in my wife's Passat for Christmas also on a T1500bdcp. For my wife 2-10's is almost to much but for me it's just a tease.

You are right about not needing the 8's for the upper bass & I probably won't use them. I only considered it because I have them on a shelf in the garage and I have 8 channels avail. on my high end.

Before I posted this I double checked what 25hz up to 32hz sounds like to make sure I was correct in my 28-30hz. statement. But you are correct, most people don't realize how low it really is.
 

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Discussion Starter #9
Orange Crush, nice!

two 15's to run from 30-45hz plus two 8's? Have you reinforced the hinges on your hatch door :)

Outside of the good comments you already received above, you will surely get in to wave cancellation all over the place and possibly hear less than gain more. One subs sound wave will impede others etc. Clean it up! My recommendation would be two good 12's (like the Sundowns suggested) with 500w a piece (which you already have) and nothing more. In my opinion you will not benefit by feeling or hearing anything more with 15's or 18's. IMAX movie theaters have two 18' (made by JBL) subs behind the screen. You are putting that in your car. 500 seats vs 4 ;)

Also, as a previous VW owner watch out for their notoriously poor and superbly expensive alternators. Although, with T1500bdcp you already upgraded that.
I'm sure your right about multiple waves bouncing off the rear glass and everywhere else. I may just go with a single sub setup but I will need at least one 15" or 18" although the 15" is appealing because the box almost doubles in size when going from a 15 to an 18.

You are 100% accurate about the VW alternator they are weak and fragile. Plus none of the aftermarket alternator companies have anything for us. They cater to Ford, Chevy, Dodge, ect... Although I do have the big 3 and 1/0 gauge pure copper welding cable and a second yellow top. STILL NEED A MORE POWERFULL ALT.!!!
 

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I have had 15's walled tuned to 32hz in my last trunk build and it got very loud & low. But Like a "Crackhead" It just wasn't' enough, I always wanted a more. Well to be honest it did everything I wanted above 32hz but I need more volume below that. (that's the only reason for considering the 18")

As for a single 10" I know for a fact it is not enough because I've been running a single 10" in a prefab box for the last two years while I dumped cash into performance upgrades, and I just installed 2-10"s in my wife's Passat for Christmas also on a T1500bdcp. For my wife 2-10's is almost to much but for me it's just a tease.

You are right about not needing the 8's for the upper bass & I probably won't use them. I only considered it because I have them on a shelf in the garage and I have 8 channels avail. on my high end.

Before I posted this I double checked what 25hz up to 32hz sounds like to make sure I was correct in my 28-30hz. statement. But you are correct, most people don't realize how low it really is.
A couple things to consider, a hatchback is much easier to get good bass from than a sedan, so I could see needing 2 10's in your wife's car.

If I wasn't driving a hatchback, I'd go IB again in a heartbeat, I had 2 15's in my last setup, and they provided the best bass I've heard in a car.

Also, this is primarily a sound quality forum, and most of us here strive for a relatively balanced system. Those 2 15's that I had were throttled way down. It's understandable that you want to take a different approach, I was just helping to put my recommendations into perspective. You can get great bass with a single woofer, in less than 2 cubic feet, if sound quality is your goal. It sounds like you're leaning much further toward the SPL side. Don't get me wrong, even us "SQ guys" like strong bass, especially if the response goes low and stays flat, but we do still strive for balance.
 

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Discussion Starter #11
Sounds like a nice setup - I would be looking at a single Sundown X18v2 in as big of a box as you can fit (manufacturer recommends 7 cubes) tuned low like 26 Hz since you already have the 8s. Although I do agree with gijoe that you really don't need those 8s unless you are putting them upfront somehow. If you skip the 8s, I'd just go with the recommended 30-32 Hz tuning. Most people are running sub and ports up in these kinds of systems.
I have been looking at the U18 & X18's along with the U & X15's. Also considering PSI, Skar, DD, & DC audio subs
 

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A couple things to consider, a hatchback is much easier to get good bass from than a sedan, so I could see needing 2 10's in your wife's car.

If I wasn't driving a hatchback, I'd go IB again in a heartbeat, I had 2 15's in my last setup, and they provided the best bass I've heard in a car.

Also, this is primarily a sound quality forum, and most of us here strive for a relatively balanced system. Those 2 15's that I had were throttled way down. It's understandable that you want to take a different approach, I was just helping to put my recommendations into perspective. You can get great bass with a single woofer, in less than 2 cubic feet, if sound quality is your goal. It sounds like you're leaning much further toward the SPL side. Don't get me wrong, even us "SQ guys" like strong bass, especially if the response goes low and stays flat, but we do still strive for balance.
I'm with you on that. I guess if I had to label my system it will be SQL? I have a very nice front/center stage and will probably end up building/glassing custom door panels like I have in my previous systems to get the front imaging just the way I like it. It is a pain in the ass and takes hours and hours of glassing sanding, glassing sanding, glassing sanding, and then some more sanding.

I'm sure I will do the same thing as you and have them throttled way back for a balanced system. But I want the ability to put the hurt on em' at will. My previous system was 2-15's walled out of the trunk and it was impressive how much bass and how good it sounded. I used to think to myself, How much more would I get out of this if I had some real cabin gain?
 

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I'm sure your right about multiple waves bouncing off the rear glass and everywhere else. I may just go with a single sub setup but I will need at least one 15" or 18" although the 15" is appealing because the box almost doubles in size when going from a 15 to an 18.

You are 100% accurate about the VW alternator they are weak and fragile. Plus none of the aftermarket alternator companies have anything for us. They cater to Ford, Chevy, Dodge, ect... Although I do have the big 3 and 1/0 gauge pure copper welding cable and a second yellow top. STILL NEED A MORE POWERFULL ALT.!!!
Two 12’s have a cone area 25%-ish bigger than single 15. And the smaller the subs, of the same type, more musically accurate it will be.

As you know box size depends of the sub you choose. They can vary a lot. For example a 12 type-R can be tuned to 32hz in a 1.5 cubic foot box which, times two, still leaves some room for groceries :)


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And the smaller the subs, of the same type, more musically accurate it will be.
No, just no. Size of the cone has nothing to do with accuracy. I run 18” and 24” subs at home and they are incredibly accurate and articulate. The JBL M2, Harmon’s most accurate studio monitor uses a 15” midrange/midbass driver.

I‘ve been told many times by audiophiles that a 12” sub is quicker than a 15” sub but the reality is the 15” is faster. If the volume output is the same between a comparable 12” and 15” sub, the 12” will have to move further than the 15” cone to reproduce the same volume since the 15” has the cone area advantage. A 15” may only need to move 2mm to reproduce the same volume output compared to a 12” driver that might need to move 3mm. So no, the smaller sub is not quicker or necessarily more accurate.
 

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No, just no. Size of the cone has nothing to do with accuracy. I run 18” and 24” subs at home and they are incredibly accurate and articulate. The JBL M2, Harmon’s most accurate studio monitor uses a 15” midrange/midbass driver.

I‘ve been told many times by audiophiles that a 12” sub is quicker than a 15” sub but the reality is the 15” is faster. If the volume output is the same between a comparable 12” and 15” sub, the 12” will have to move further than the 15” cone to reproduce the same volume since the 15” has the cone area advantage. A 15” may only need to move 2mm to reproduce the same volume output compared to a 12” driver that might need to move 3mm. So no, the smaller sub is not quicker or necessarily more accurate.
I agree that a 15"-18" can sound just good and be just as accurate as a 10" or 12" sub. As long as it is in a well designed enclosure, with clean power, and isn't being over driven like a lot of SPL guys do. My previous systems had plenty of bass but could never reproduce the low low stuff (25-30hz) at the same volume as the higher subwoofer frequencies (35-70hz). I want to be able to hit the low low stuff at high volume! I have noticed through my previous systems my 10" subs can do 28hz at a certain volume, but a 12" can play the same 28hz at a higher volume and a 15" is louder than a 12" @28hz and so on... I will most likely do a single 15" since the 18" will eat up every square inch of the hatch.
 

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There is definitely no replacement for displacement (cone and excursion) when going for deep bass. As you point out, larger drivers have more output and another key is that at the same output level as a smaller COMPARABLE driver, the larger driver will have less distortion because it isn’t working as hard. But as you surmise, going larger is great up to a point since the enclosures are usually larger not to mention heavier.
 

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I have 2 Alpine Type-R’s(SWR-1242D) at 1 ohm on 1200W in a custom ported enclosure roughly 4.33cuft net in a 2003 RSX. Subs back, port side. I’ve moved the enclosure around a few times, subs up, subs forward, but I always end up going back to subs to the rear. That’s my preference. The low’s rumble, the hits are tight, and precise, and I still that tickle in my gut when I really drive em hard. I also have 4x JBLGTO609C all passive on 1000w to balance the equation.

Just out of curiosity I’ve been looking at a design I came across that looks like a combination of a dual folded horn and a 4th order band pass, (I could be wrong on guessing the combination of designs.) when I first got the subs, (back in 2006 lol) I had them in a sealed enclosure, then moved to ported, and both performed quite well. I think the Type-R’s will excel in the design, it’s just a matter of getting all the measurements right before I commit.


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If you’re going to try different designs, you might want to give HornResp a try as that is what the sub gurus at data-bass.com use as their design program for more complex subs.
 
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