Reverse Mount Sub Help

[DECIM8]

Hey guys,

Im going to mount my sub directly over the spare wheel and wheel well.. Is there a problem with this? Main issues at hand currently is ive got a F.O huge sub (comp level why I have it I dunno) and a Massive ported custom box. But its damn heavy, Together they weight in close to 70kg and changes in cornering (espeically with my bald tyres) is rather large.

So I just want to reverse mount the sub in the boot on a layer of MDF reducing the weight I may raise it slighty but the basic idea is the Boot will be the box.

Question is, Do I need any space for air to move infront of the cone? Its ok if I do as ill mount it on a stand but I need to know.

I dont want to remove the spare tyre so dont suggest it.

The sub will be directly mounted in the middle to improve performance. Currently the sub is loud but I dont need it to be insane. Do you think I will lose much performance from it?

If anyone could help please do..

I will post design plans shortly - To get an idea in the mean time this is HypeR33's boot setup, I want one sub where his two are and it will be facing the reverse way they are.

Heres a rough plan

Edited March 21, 2007 by DECIM8

[Chris Rogers]

do a mold of the tyre and then invert the wheel so you have more space. I would make the whole thing a plug that way you have a flat floor and still have the spare tyre.

[DECIM8]

Ive sent you a PM, However here it is for everyone else

Im unsure what you mean about a plug? I understand the reversing of the wheel and glassing it, Which is a excellent Idea, by plug im assuming you mean removable enclosure??

[Trav33]

Decim8 - how did you go with your install? Did you go ahead with this design?

[are33]

Thats an awsome design, Show us how it went.

Edited May 13, 2007 by OBNXSH

[DECIM8]

Hey guys thanks for the interest...

I built the whole setup and tore it out again, the fibreglass I felt was not thick and good enough for the sub, it actually had enough volume to make perfect sound which I was excited about...

The sub box is on its second trip to my garage for re-molding.. this time im using the original mold so my car doesnt stink of resin again..

It looked very sexy but a few tips

If you do this design make sure you elevate the sub and angle it to point outward.. this will stop shit collecting in the cone.. the subs weight holds the box down and the design stops it moving side ways I also screwed it into the metal struts in the R34 boot...

I expect my new design to be finished in the next two weeks. I didnt realise there was so much facination with my design .. just wanted to be different haha oh and have my car alittle more stable in cornering .. now I can do twisties without losing the rear haha..

Will update in the comming weeks

Quick note .. spare wheel had to be removed .. the sub needed a 57L sealed enclosure to efficently operate.. 80L ported its a mother of a suB!

Edited May 14, 2007 by DECIM8

[frx026]

I had the opportunity a little while ago to build a full on demo car. I mean, no budget, any gear. Awesome experience.

Our first design used inverted subs. They box was mm perfect. It sounded like crap.

Did a few experiments and this is what i found.

By inverting the sub it effectively reduces the cone area of the woofer. The cone that sees daylight through the basket, magnet and motor structure of the sub is less than the sub when it it is traditionally mounted.

We actually got a brand new sub, layed it face down. Shot a thin coating of paint of the back of it so it would fall on the exposed cone. Then, after it dried, cut the cone out of the woofer and added up the cone area that had paint on it, ie - the parts thats were firing out directly.

The results meant our 12' woofer was about the same cone area as a 6" speaker.

It certainally showed in the results of the sound. it sucked. we had no low bass at all. just a higher mid bass type response. definately not the sound you want from a demo car that is meant to impress.

Sure the subs looked cool all exposed. but sound was lost.

We also did some experiments about porting vs sealed with inverted and tradiationally mounted subs.

In all of what i did inverted made less output.

The test car was a hyundai coupe. We used an audio control RTA to measure spl and a sweep was used to determine the loudest spl figure.

To put some of this in perspective. 2 x 12 inverted netted us 128db, 2 x 12' traditionally mounted netted us 145db.

Box was the same sealed box, amps were the same. I know it is a huge jump 128 ->145. we actually checked the equipment was functioning correctly before going to far. Unfortunately it was.

While i wish you luck, and hope your setup works i just thought i would share my experience with inverted subs.

[Chris Rogers]

PJ,

got pics (point me to them.)

[DECIM8]

Thats very interesting .. Might design the box for both types of use this time .. swapping depending on music

Cheers

[frx026]

PJ,

got pics (point me to them.)

Hey,

i cant post pics, long story.

But i can email them to you.

Shoot me a pm with your direct email addy..

I think you might be surprised by what i send through

[Trav33]

Ok, point = inverting sub loses performance.

What about a ported enclosure vs sealed enclosure? Whats the advantages of a ported enclosure? Does the volume of a ported enclosure generally have to be larger?

[baron25]

Ok, point = inverting sub loses performance.

What about a ported enclosure vs sealed enclosure? Whats the advantages of a ported enclosure? Does the volume of a ported enclosure generally have to be larger?

In short, yes. In long, no.

To get the best possible output from a driver in a ported enclosure, it will be much bigger than the equivalent sealed box. Having said that, there is an overlap region where a larger sealed box will also work as a ported enclosure, but it just won't be the optimum setup.

Edit: i almost forgot - ported enclosures can give a higher output (anywhere over 3dB, which doesn't sound much but is actually twice as loud) but at the expense of sound quality. Ported boxes need to be 'tuned' to a particular frequency, which is boosted in volume, but the remaining frequencies may be diminished. Typically, sealed boxes have a tight, clean sound, where as ported enclosures tend to be more of a rumble.

Edited May 15, 2007 by baron25

[VB-]

inverting sub loses performance = wrong

there are technical things saying there are less cones area blah blah blah in reality you wont hear a difference.

ported = louder, and in general boxes are bigger

[DECIM8]

ported is deeper and often louder..

[frx026]

inverting sub loses performance = wrong

there are technical things saying there are less cones area blah blah blah in reality you wont hear a difference.

ported = louder, and in general boxes are bigger

In the testing we did, we had unlimited money. Unlimited new equipment if we blew something up and went through 17 different size and type sub boxes in 5 weeks.

All results showed that inverted subs provided less output than normal mounted subs.

Most of the results were that evident you could hear the effect even beofer seeing the metre.

I guess that's why the worlds loudest spl cars dont invert their subs. They loose total volume output.

[DECIM8]

was it done in the car? I mean I believe you but wank factor far outweights losing my hearing .. as if I want to quality ear blowing bass? common

[Trav33]

wank factor far outweights losing my hearing .. as if I want to quality ear blowing bass? common

At least your honest about ya need for bling!

[frx026]

was it done in the car? I mean I believe you but wank factor far outweights losing my hearing .. as if I want to quality ear blowing bass? common

Yes, this was done in a car.

The design brief for the car was not to be an SPL monster, but rather a good sounding street system. We were trying to keep the wank factor out of it.

In all the test we used the same amps.

The difference was incredible. It was like going from a pair of 6x9's off a headunit to a pair of 12's.

The only reason we needed to make sure it was loud and a little bass heavy is the car was to be used for display purposes for a manufacturer. potentially it would be at shows like auto salon etc, where things need to be a bit more bass heavy just to be noticed.

[G_Force]

Yes, this was done in a car.

The design brief for the car was not to be an SPL monster, but rather a good sounding street system. We were trying to keep the wank factor out of it.

In all the test we used the same amps.

The difference was incredible. It was like going from a pair of 6x9's off a headunit to a pair of 12's.

The only reason we needed to make sure it was loud and a little bass heavy is the car was to be used for display purposes for a manufacturer. potentially it would be at shows like auto salon etc, where things need to be a bit more bass heavy just to be noticed.

Did u take into consideration the volume of the sub itself? Reverse mounting in the same box would change the enclosure volume even though its not alot ie. maybe 1-1.5 cu ft difference for hte 2x12". Did u also reverse the polarity of the subs when reverse mounted?

Interesting experiment though, i would have like to have personally hear the difference.

[frx026]

Did u take into consideration the volume of the sub itself? Reverse mounting in the same box would change the enclosure volume even though its not alot ie. maybe 1-1.5 cu ft difference for hte 2x12". Did u also reverse the polarity of the subs when reverse mounted?

Interesting experiment though, i would have like to have personally hear the difference.

Yes, we made 17 different boxes.

All parametres were looked at for each design/size/shape.

Edited May 22, 2007 by frx026