Infinite Baffle / Free-air installation.

[kachunkachunk]

Hey all,

I was wondering what your takes might be on replacing the factory 8" subwoofer with an aftermarket one. Say a JL Audio W3v3 or something.

I have an 08 Accord EX-L Sedan with an almost-complete aftermarket sound system:
- Apline PDX1.1000 with two Alpine Type-R 10" subs.
- Ported enclosure (going sealed-custom some time later).
- Alpine PDX4.100 with two pairs of Alpine Type-X 6.5" Reference components (front+rear).
- Pioneer Premier AVIC-F90BT head unit.

And I have an Alpine PDX2.150 sitting idle.
I'm pretty sure that I could wire up an 8" 300-watt sub in mono to the PDX 2.150, like the JL Audio W3v3.
It should fit right into the stock mounting area (someone fit a higher-end 8" JL sub in there, funnily enough). Maybe with minimal cutting of the mounting area, if it's required.

The problem, I'm thinking, is the infinite baffle setup here. The job I saw on someone's 09 coupe didn't really to the extremes implied to be required in IB setups (proper sealing of the baffle itself), and it's supposed to still sound quite good, but he was doing this completely without a proper box+amp+sub setup. Just using factory locations.

I don't think these subs are designed for IB setups at all - and subs in general aren't, you get proper IB drivers?
What do you think the drawbacks or risks will be using something like the W3v3 in this application? I figure it'd be less accurate because of the lack of sealing. And there's risk of damage of the sub somehow? Can someone comment on the risks/cons?

...You might be able to tell that I've sort of shooted for some accuracy so far with the setup, but I was hoping the 8" still more than compensates for a bigger concern - harder hitting kickdrums and bass guitars. It should hopefully be something that nicely fills in everything a wee bit higher than what my 10" subs in the ported box do properly now. If you think a sealed box is already perfect to address this, I could consider that. I know ported will mud stuff up a little and die off quickly when you go up.

That 8" factory mount is the only thing left to modify, heh, so I am hoping I get your blessings on doing this. Would be nice having the 8 AND the two 10s.

Thanks, I really appreciate your opinions.

[tsmith1315]

-A single 8 in IB wouldn't contribute a much to output given what you already have.

-Sealing the baffle wouldn't be a big issue, but having the 8 in the trunk along with the output from the 10's would be (for the 8).

-The biggest risk to the 8 is damage from overexcursion.

If you wanted to go strictly IB, that's quite reasonable. I would recommend at least four 8's, but prefer larger woofers.

If you're looking for more midbass, I'd suggest working with what you already have. Some suggestions:
-enclose your 6.5" woofers, you might be suprised what they have to offer.
-work with EQ/crossover tuning
-work with sub box tuning
-convert your sub box to sealed, as you mentioned, and spend a lot of time messing with EQ/crossover before you pass judgement

My opinions only.

[jol50]

I agree, one 8 IB will do little. I recommend minimum pair of 10s and more for more output with IB sub setups. You should be able to get your box to do that, even ported as its higher tuning should not be that different than a sealed. It is in your LP and EQ tuning mostly though the box can change it. Try different LP slopes to start. If you turn your LP to 100Hz and hear lots of high punchy bass, then you know they can do it....just a matter of the right tuning.

IB does not have to be perfectly sealed, but near the sub should be or you lose output. It needs to be solid or it vibrates. More cone area equals more output and IMO more xmax has less importance than for in-box subs but I've never bothered to run a really big xmax IB. You only need around half the amp to run IB.

I'd first try more tuning on the box LP, then if you have not try deadening your doors and even enclosures for the current midbass. They should sound good without huge bass with your subs off, if they sound like tin cans with no EQ that is your problem. Check phase on them.

You can try an 8 in there. I'd get one with medium to higher qts. If it will take reasonable power it might be ok but the 10s may push it around. Still output of an 8 at say 80Hz is not going to be that great and your 1KW on subs will blow it off like its not there. A pair of 8s might do more for midbass but I would not want to do IB with the 10s in the trunk.

A lot of subs can be run IB, just that IB has different needs and results than boxes. If you want SLP type loud then a box will do more for you usually. I like IB because it gets lower and takes up no trunk room. I have four 12s and a .8cf box with one sealed 10 took up more space in my trunk. Needless to say below 50Hz I can run half the amp I had on the 10s and get way more bass. On 400rms the back of the car just rattles everything and I can't hear the highs.

[kachunkachunk]

Ah, very interesting, thanks for the input.

I'm thinking more and more that I need to seal the box or get a custom one (after all I have not even heard my subs in a better/sealed box to begin with).

They're in some fairly cheap Bassworx box which I'm not quite content with the dimensions of. A custom build is the only way I can get something that conforms correctly in the trunk:


It won't really fit width-ways in the back near the seat, sadly.


I got curious about boxing the 6.5" drivers. Can I do that in the doors? Or was that more in reference to the 6.5" drivers in the rear deck? I suppose I could try to design/buy a box/sealing application for the rear deck in the trunk. Never really gave it a lot of consideration.

[kachunkachunk]

Sorry for the double-posting in effect. I'm under moderation and don't think I can edit.

Anyway, I wanted to comment that the above picture is pretty old but still pretty applicable. You can pretend that that thing is actually... you know, plugged in. :P

The box is about an inch too tall and an inch too wide to fit snug into the back of the trunk against the seatback.

[tsmith1315]

Originally posted by kachunkachunk

I got curious about boxing the 6.5" drivers. Can I do that in the doors? Or was that more in reference to the 6.5" drivers in the rear deck? I suppose I could try to design/buy a box/sealing application for the rear deck in the trunk. Never really gave it a lot of consideration.

It's certainly easier said than done.

Rears will be simpler. It will keep the subwoofers from modulating their output, in addition to getting more efficient bottom end out of the 6.5's. If nothing else, just some plywood silicone and L-brackets will get something in place.

Doors can be tricky, impractical, or just a bit of work depending on what you have to deal with in there. Since they are right up front with you, it's bound to be worthwhile if you're a critical listener.

Use your imagination. In my experience, even a half-assed attempt at an enclosure makes a difference in either location. Typical enclosure size for using a 6.5" down to ~100 Hz would be 1/4 to 1/2 cu ft. I don't know if yours would fall outside this range.

As jol50 said, work on crossover/EQ settings on the 6.5's with the subs disconnected, and then on the sub. With decent power and 4x 6.5's, you should get pretty good midbass at moderate levels as they are. A lot can be done with systematic tweaking.

One last thought, you may want to try removing the existing 8" woofer. Your trunk is well sealed, and the bass from the box has to radiate through the seat, rear deck, rear speakers, etc. An 8" opening could make a difference. A manifold directly coupling the woofers output to the hole would certainly make a difference, but that's yet another animal to deal with, and wouldn't be friendly with your existing box.