Custom MDF enclosures : Install / Cost info needed (pics enclosed)

[s0uljah]

So Im nearing the end of my current ICE quest, which has been going on ever since I joined T-Bhp Im still in the process of SAVING towards the final install costs and exploring options that will save me some precious rupees...

Now coming to the situtaion at hand : I want to accomodate the 6.5" JBL 606ce in an enclosure in the FRONT of a Santro Zipdrive (manual windows). I have been informed by one installer that without power windows, I cannot make mods to the door ? From the pics I have seen of Rareone's 6" install in the front door of his santro... there seems to be some metal cut to accomodate the speakers. More on this later...




The above pod is fixed in a santro (power windows)... and holds a 5.25" CV comp...



The guy now has this MDF enclosure accomodating both the tweeter and mid of the CV comp... Im interested in something like this as it positions the mid a little better... Regarding tweeter Im unsure whether this is the best position... inclined to try Sam's DIY tweeter install.



Thats what his install looks like in the boot... Im after a SEALED box like that... minus the fancy flames

Iv been offered the component door pod + custom sub box (mdf+black carpet) for roughly 3k. Another installer quoted roughly 2.2k for just the sub box.

Today i visited a warehouse sort of place that stocks art leather seats and there was a lot of MDF planks, boxes, spacers etc lying around so I inquired regarding costs for custom stuff, he said for approx 2.3k I could get speaker enclosures + a custom sub box. The only issue with these guys is not the quality or finishing but how to get them to make accurate enclosures...

Can someone help me translate the following specs into measurements I can give the guys building the MDF enclosures ?

General Specs of JBL GT4-15

Frequency Response 20Hz - 400Hz
Sensitivity 91dB
Impedance 4 Ohms
Voice-Coil Diameter 50mm
Cut-Out Diameter 362mm
Mounting Depth 172mm
Overall Diameter 385mm
Vas 133 liter
Qts 0.44
Fs 28.36Hz
Qes 0.47
Qms 7.35
Sealed Enclosure (vol)43L
Vented Enclosure (vol)113L

Thanks in advance

[jkdas]

emm, one a Sony amp right? and its a ported box. There are websites which would provide you specs abt teh box you would need.

I have seen the front pods in an install done by a shop at Chennai ( via its website).

and while you at JBLfying, do damp your boot and door well. My car has started have the rattle problems, even my rear view mirror rattles :((.

A good installer should be able to fit 6inchers at frnt using MDF spacers or you can get fiber job

[Sam Kapasi]

Well, actually you already know the Recommended box size for both sealed and vented enclosure.

1Liter = 0.0353 cu.ft

So if you do the math, a 43 liter sealed box is 1.52 cu.ft - that can translate into 1ftX1ftX1.52ft or a similar combination.

And for vented, 113L is almost 4cu ft. So approximately 2ftX2ftX1ft or a similar combination.

In case you opt for the vented option, the length of the port is also given in the diagram.

Should be quite easy really.

[s0uljah]

Box is ported...yeah its a Sony monoblock and an oooold Alpine V12.
Dampening would definately be needed... though I expect it will be done only a weeks after the install due to budget constraints.

I just realised I should have visited SoundFactor and had a chat with Preetham before posting here.... Lol. *makes a mental note*
fibre - costs will explode ??

edit :
Sam your post appeared soon after my submitted mine, thanks for the diagram and figures.

another question... how important is the box shape ?? Online vendors selling gt4 -15" boxes show rhombus shapes... so is the vented sub box in my first post

[Sam Kapasi]

The shape of the box really makes no difference as long as you get the port right and the volume.

However when a box has completely parallel surfaces within, it causes "standing waves" and other issues, that are normally avoided by having non parallel sides.

I wont complicate you firther on that, though I fear Navin might

[s0uljah]

your right sam... doesnt sound like we need to get into that in-depth as it is not a crucial factor Im after a sealed box anyways...so no question of port

[jkdas]

sealed saves space too! 113lt in the boot! phew!

and so whats his amp and whats your recommendation?

[Sam Kapasi]

Frankly, I would have recommended a sealed box anyways, but i fear your amplifier may not have juice enough to drive a 15" sub in a sealed enclosure.

[navin]

Originally Posted by Sam Kapasi

The shape of the box really makes no difference as long as you get the port right and the volume....I wont complicate you firther on that, though I fear Navin might

you forgot to include the volume of the woofer in your calculations. and in case of the ported box the volume of the port too.

so actaully you have to build a sealed box that is 1.5cu. ft. + a bit more to compensate for the volume of the woofer.

Sam, i believe you asked for this information.

Now that we have the volume done I am working on a new box idea. B&T and GTO have seen the first layout of this (the day of the JBL store opening at Attira). It involves using 6mm marine grade ply encased in resin bonded fiberglass. total wall thickness will be 12mm but it should be as stiff as if not stiffer than 25mm MDF. The other advantage of this technique is that you can build boxes to any shape rather easily.

6mm ply (not MDF) bends quite well (you can use 4mm ply if you need tighter bends). now use this as your "mould". encasing in resin bonded fiberglass makes it awfully stiff and light. In the end if you still have resonances to damp use a mix of 1.5mm lead sheet, glass wool, and open cell foam depending on the nature of the resonances.

[Sam Kapasi]

The port is a hollow tube ya, the volume will be super negligible. The old man is too much

[low_bass_makker]

ya and a little 5 % there and there will not matter much so dont go in such small detail.......

[Bass&Trouble]

Originally Posted by navin

Now that we have the volume done I am working on a new box idea. B&T and GTO have seen the first layout of this (the day of the JBL store opening at Attira). It involves using 6mm marine grade ply encased in resin bonded fiberglass. total wall thickness will be 12mm but it should be as stiff as if not stiffer than 25mm MDF. The other advantage of this technique is that you can build boxes to any shape rather easily.

Hmm yeah. The enclosure in your Skoda RS looks like a good project. Can't wait for it to finish completely.

What Navin is doing is actually overkill. Most people building a fiberglass enclosure wouldn't have a full MDF/ Ply structure underneath. This will be more rigid inspite of not having a 18-25mm wall thickness.

Originally Posted by low_bass_makker

ya and a little 5 % there and there will not matter much so dont go in such small detail....

Originally Posted by Sam Kapasi

The port is a hollow tube ya, the volume will be super negligible. The old man is too much

No ya young man, you have to do the mach-mach of accounting for port displacement, driver displacement and sometimes even for bracing ya. Otherwise all these five-five percent will add up and become too much ya. And for ported enclosure, the sound can be very bad ya, if your volume is over or under by 10%.

Btw, port displacement does not mean just the volume of the material used for making the hollow pipe ya. You need to account for it as a solid cylinder. And before the 'old man' points out, when calculating the port displacement, please add the wall thickness of the port to the effective or internal port diameter considered in the volume calculation. Wall thickness is low for PVC but can be high if it's a slot port made of MDF. I'll stop now before you call me old too.

[navin]

Originally Posted by Sam Kapasi

The port is a hollow tube ya, the volume will be super negligible. The old man is too much

the port is a hollow tube but the air mass in the tube is a Helmholtz resonator. A Helmholtz resonator is nothing more than an enclosed volume of air connected to the outside world by a narrow tube, called the port. but for volume calculations it is better approximated as a solid rod and not a hollow tube.

This book explains it in better and greater detail.
http://en.wikibooks.org/wiki/Enginee...closure_Design

[gunbir]

Originally Posted by Bass&Trouble

No ya young man, you have to do the mach-mach of accounting for port displacement, driver displacement and sometimes even for bracing ya. Otherwise all these five-five percent will add up and become too much ya. And for ported enclosure, the sound can be very bad ya, if your volume is over or under by 10%.

Btw, port displacement does not mean just the volume of the material used for making the hollow pipe ya. You need to account for it as a solid cylinder. And before the 'old man' points out, when calculating the port displacement, please add the wall thickness of the port to the effective or internal port diameter considered in the volume calculation.

Agreed 100%. While sealed enclosures are comparitively more forgiving, ported means being precise.

[navin]

Geez, I dont belive it. I think I may be right this time after all! Now isn't that a rare occurance *looking for a blue moon tonight*.