Anyone have a half wall/back seat install?

[uhoh45 10+ year member]

this is for half wall half trunk

 

[Camineet 10+ year member]

Thanks a lot for the guidance. This particular box wouldn't work for my convertible, but it is a good reference from which to start considering such a box configuration. My convertible sits so low, that this box upside down might actually work. You see, just behind the rear seats is a steel wall. And just behind that wall are the actual rear wheels. This is a low SOB. This box upside down would allow for the back part to extend into the trunk space. After getting over the wheels, the trunk does dip down to the street quite a bit, and this box wouldn't take advantage of any of that space. In fact, the back part that extends rearward into the trunk would be awfully thin if I were to flip this box and try to implement it in my vehicle.

Hey what the heck am I thinking? The part that would extend toward the trunk would be the spot where the convertible top goes. Nevermind. Back to the drawing board. I think my original idea of tacking on eBay boxes to the back of the wall is still the only way for this vehicle.

 

[theCybe 5,000+ posts]

Hopefully 2 twelves in the trunk, 2 tens and 1 eight on the simple wall will be enough to satisfy the first time. I just don't have $1000 to throw at the local shop to design some kind of super custom scientific box for my vehicle right now.

We're all going to tell you that it's wrong to do this, but you aren't going to listen.

Lots of super-scientific box plans available for free in the sticky thread at the top of the enclosure design subforum.

 

[Camineet 10+ year member]

Do you mean that there are box plans in the sticky thread that will work well for this type of enclosure? I'd certainly be interested in checking them out. I'll have a look at that thread.

You're the 2nd responder who has advised against doing this, but nobody has yet to explain why I shouldn't. I have seen this done in at least three vehicles before, so I have reason to believe that it can work. Plus the OP said he heard a convertible Mustang with this type of enclosure that was awesome. So I would very much appreciate it if someone would shed some light on this apparent pitfall that I'm supposedly headed toward.

 

[inapontiac 10+ year member]

keep the back seat and do like i did

 

[JohnBlayz142 10+ year member]

1. I wasn't talking to you.2. I was talking to the OP.

3. Still, don't do it.

4. Yeah.

nG

I've heard systems like this that have sounded great....why wouldn't you do this?

And InaPontiac, I don't want do do all that sealing work. I just got my car and I'd like to keep it in factory like condition.

 

[theCybe 5,000+ posts]

Since have good manners and a grasp on the English language, I'll be happy to advise you as to why mixing subwoofer sizes will yeild dissatisfactory results.

When a woofer moves, it creates a soundwave by affecting the air around it. Air is compressed, and then rarefied. These waves travel at a particular velocity.

When you combine these waves with waves from additional devices on different trajectories, you experience a collision of waves, resulting in 'cancellation.'

A driver in your trunk produces a wave. That wave arrives milliseconds later at nearly the same point as another driver that is producing the wave - the delays (sonic, electrical, and mechanical) between waves being produced makes them 'out of phase' - reinforcing one part of the wave, and cancelling another part.

Which leaves you with poor sound quality and less than optimal performance.

Woofers of different sizes have different performance metrics, and although a 30hz electrical wave looks the same on the graph, what comes out of any different speaker, at any different position, from any different enclosure, of any different size, reflecting off any number of different surfaces at different distances -- you get the idea. They just don't match up.

//content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Choose a size, choose a plane, and install your woofers on the same plane.

Mixing them can be done properly in theory, but the mechanics and calculations involved are enough to drive a sane man mad.

 

[Camineet 10+ year member]

I agree with everything you said. I've operated under those same principles when designing all of my past systems. But this time around you may have been right when you said that no matter what I'm told, I'm going to still try this. Here's why I'm still optimistic. In recent years I've seen some really wacked out installations. I've seen numerous fiberglass fabricated boxes with woofers facing all different directions as if they was some kind of snapshot of a cluster of woofers exploding taken. None of them are on the same plane, and some of the darned things are even facing inwards into the box with the others conventionally mounted firing outwards. Plus, I've seen doors, sail panels, rear decks, trunks. etc. lined with multiple woofer sizes in these next gen installations. I figured that people had discovered that by throwing out conventional thinking and just going nuts, that they were achieving great results.

I'll be honest, if I really thought I could get 100% satisfying results with the two twelves I already have to put in the trunk, I would probably not bother with trying to add more woofers. But since the convertible trunk is so small, it just won't accomodate a large ported box. A sealed box is all that will fit. I'm just not confident that this will get her done. So I'd like to try some experimentation with this wall thing, especially if others have succeeded.

The other thing is, I love the appearance of Polk Momo woofers. These are the twelves I started with. Then I realized that I had another amp that could power an 8 inch woofer, and that I'd just love to see one of those Momo's in the passenger compartment rather than having to open my trunk to see the twelves. I envisioned it as being positioned similar to the Dodge Viper 8 inch woofer in the same place (at least the early models had this I recall). Then I realized that I have yet another amp that can power two tens, and I could toss those on the wall as well and still fit my carPC, the original two amps with which I started the design, distribution, crossover, caps, and 6x9's. So this isn't entirely for achieving crazy SPL. I want to put these woofers in a visible place for cosmetic reasons, and I'd like to implement a decently efficient design in order to achieve enough bass to satisfy me. My reason for posting is in the pursuit of putting these things on the wall in a way that will hopefully achieve some echo chamber effect if it can be found at all in this configuration. If the only effect I get with these additional woofers is similar to the results of tossing a sealed or ported box into the backseats of a sedan, then I won't entirely regret it. If by turning off the wall woofers and just playing the twelves I get better results, then I will certainly not include them in the final installation.

Again, thanks for your guidance and patience. If in the end the twelves sound better alone, I will certainly know why after reading your response. Given that I will at least go forward with this as an experiment, any additional advice you have that moves me closer to a result that's better than the 'box in the back seat of a sedan' effect would be great. Thanks again.

 

[Camineet 10+ year member]

Oh, one more quick thing. I remember now why I decided to go forward with this experiment in the first place. I did do a quick check to see if this wasn't totally erroneous. Here's how: When I first thought of throwing in the eight incher, I first recalled what I knew about cancellation. Then I immediately recalled all of the wacked out installs that I had recently seen. Then I recalled something from personal installation experience. My first system started off with two Kicker tens. Then I added two fifteens. This was in highschool before I knew better. Well, I recall hearing about cancellation and checking my highschool system back then to see if I was indeed wasting gas and electricity by hauling all 4 of those different sized woofers around. Nope, I listened to them separately and together. That system was definately as incrementally loud as each set of woofers were alone, when combined. Does that make sense? In other words, I ran them independently and together, and found that the system wasn't experiencing any noticeable cancellation. And the tens faced inwards from the sides of a Daytona hatchback with the fifteens in the farthest back facing the glass. If I had a big 'ole truck I would certainly follow plane, size, and wave principles. But this is a really limiting installation, and I gotta be bold. Thanks for your understanding, and hopefully your support.

 

[theCybe 5,000+ posts]

I say go for it then, if you're aware of the implications.

Just a sideline regarding inverted subs; It's fine to do this, just reverse polarity on the inverted one. So mechanically, that's "less crazy" than multiple sizes, and crazy-pointing woofers. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

Best of luck, and do keep us posted on your progress. //content.invisioncic.com/y282845/emoticons/smile.gif.1ebc41e1811405b213edfc4622c41e27.gif

 

[Camineet 10+ year member]

Right on thanks. I've started a new thread asking if there's anyone like Moe Lester who can design me a box for a fee. I wouldn't mind building one like he has posted, but the ports are all front firing. So I asked the forum if there's someone who can use some software to design me one like Moe's, but with the vent on the bottom. I've seen little wedge boxes with the ports on the top, so although this may not normally be a great way to build boxes, I do know I've seen it before and can at least hopefully get me better results than a sealed box. We'll see.