jbart1981

For ne1 who has seen the size of the pass through. Is ti big enough to remove and replace with a sealed or ported sub. 10" maybe? From what it sounds like the bottom end in the bose system will not be satisfying after having dedicated subs in all of my previous vehicles. i am really just wondering what the dimensions of the space left behind if the pass through divider was removed hxwxd. The I can start the volume and enclosure calculations.

p.s. I am not a"thumphead" just looking for some crisp, clean, you can feel it in your butt-- bass notes

lefuton

if you mean 10" circle then i don't think it'll fit cause it's pretty narrow... i could go out and measure it if you really want but maybe a 6x10" speaker would fit in there.

MrWigggles

I believe the opening is 8 inches wide. Which mean you "could" make a speaker enclosure that fit between the two seats with an 8" woofer that faced forward.

I thought about this but in the end decided that I will be putting a small enclosure in that area with a 10" sub that faces backward. However, if I go the ported route, the port will fire forwards directly into the cabin.

I thought hard about this one. A JL audio 8W7 facing forward in that passthrough area is very tempting, but I think I will be doing a 10" sub instead.

-Mr. Wigggles

Doctorr

That's probably a great idea, jbart - an enclosure on the trunk side, vented into the cabin - lots of room back there, the opening is 8"x11.25" and the frame is good and solid for mounting a biggish (12"?) driver.
.
.
.
doc

Sputnik

You should be able to replace the passthrough with a 8" sub with an enclosure extending into the trunk, and cover it well so that it is hidden.

Considering the fact that by the time you consider the rim and surround, the sub's cone is less than 9". A ten inch sub shouldn't be choked too badly by an 8" slot. Make sure that you have a grille material in the passthrough so that the sound can come through.

---jps

r0tor

iTrader: (1)

ok... don't mind me celebrating the fact my snowboard will fit in there :p

... anyway, this sub idea sounds really good

jbart1981

mr. wiggles you took th ewords out of my mouth . after looking at more pics i realized front firing speakers were out of the question ut a ported, perhaps band pass enclosure wioth the speaker facing towards the trunk and the port behind it facing into the cabin might be the best way to go. Now just figuring out the design so that the resonance patterns inside the enclosure don't interfere too much . what do you think about a frenulated--top cut off-- wedge , trapezoidwiththe ports on the shorter side and the sub on the longer side alllowing for a larger sub? Any body with wave equation knowledge or box building expertise would be greatly appreciated.

Sputnik

Well guys, just to make sure that we're on the same sheet of music, let me point something out (especially to the uninitiated who may be listening in).

The way a ported enclosure is designed, the output from the port is supposed to combine with the output from the front of the driver to produce a stronger (louder) impact. When you are designing a ported box, you need to locate the port so that it's output can combine with the sub. This is why you see most ported enclosures with the port on the same side as the sub, or at least on an adjacent side.

A trunk is not normally sealed airtight from the inside of the car, but it is effectively sealed as far as far as airflow. When you build a ported box so that the port points into the cabin, while the sub points into the trunk, you've effectively eliminated the "coupling" of the outputs, and get rather poor results inside the car.

A bandpass enclosure (one where the sub is completely enclosed in the box, and there is only a port for output) is another story. One can be built so that the port is all that has to go into the cabin. The drawback is that a bandpass box HAS to be designed well, and is very unforgiving if you do not get that volume or port size correct. The port length is very important, so you can't just snake a pipe into the cabin either.

And don't forget about the narrow output that the bandpass produces, and how you match the midbass to it, and how low you need to go.

---jps

MrWigggles

I just measured the openning and it is 8" wide at its narrowest point at the rear of the passthrough. But the actual front face piece that goes between the two seats is a full 9.5" wide. (The removable storage bin itself is 4.5" deep and about 14" long.

So, I think you could do a little 8" sub enclosure in that area facing forward or do a 10" enclosure facing the rear like mentioned before.

Also, In my opinion the removable storage bin is useless, so with whatever sub enclosure you come up with you could easilly remove front face of the storage bin and somehow use it on the front your enclosure for cosmetic reasons. (i.e. put a nice little grill on it or something) Make it look factory.

-Mr. Wigggles

MrWigggles

On a small cabinet speaker the coupling of the port is important with the main driver. In these cases the tuned port is in the neighborhood of 100Hz.

But on a good sub enclosure the tuned frequency could be as low as 25Hz. At 25Hz the wavelength is 40 feet! The port doesn't need to be anywhere near the actual sub. With sub facing forward and the acoustic energy of the port lagging that of the main sub, having the sub fire backwards (in effect crude delay) might help to reduce group delay. This is all conjecture. The actual resulting acoustics are much more complicated than I describe (or even completely understand)

As far as bandpass enclosures are concerned, I have some experience in that area. My senior engineering project was a sixth-order bandpass enclosure using a JL audio 12W6 (still use it in my home theater). Bandpass definitely has some advantages but as Sputnik points out they are very tricky to build properly and size is one of their disadvantages (yes, you can change the design goals and make a small one, but it will either be too high in frequency or it will be very acoustically inefficient)

The bandpass sub I wound up with my 12W6 is an efficient 1.5 octave low frequency design that ends up taking a whopping 3 cubic feet in size and 100 lbs in weight! Not suitable for the RX-8.

With high power digital amps and woofers with high cone excursion these days, I don't see the real benefit of bandpass anymore over say a much smaller sealed (or ported) box with similar performance.

-Mr. Wigggles

Sputnik

Yeah, that's what I was thinking. The 8x4.5x14 space is going to be too small for an effective enclosure itself, but whether you use that space for part of the enclosure, or put the complete enclosure behind the seats "peaking" through the ski-hole, you should be able to put a nice grille on the front and have it look clean and stock and hidden.

---jps

r0tor

iTrader: (1)

...just a random thought here I thought I would throw out...

since we already have 9" speakers in the door, couldn't you hook up a modest amp to each and make them thump?

MrWigggles

You'll make them thump alright. Thump as they hit the grill in front of the woofer or thump as the voicecoil hits the rear back plate of the magnet housing (it is a neo magnet so there might not be a plate per se, but it will hit something)

I am pretty sure the front 9" are maxed out already as far as there work load. They are doing all the bass and most of the midrange in the front of the car.

A "real" 8" sub or 10" will be designed to take the abuse. The speaker will have a much larger x-max and a heavier stronger cone. This will allow a dedicated sub to play louder and deeper than say a "midbass" driver like the speakers in the doors.

-Mr. Wigggles