Different subs and enclosures (LOOONG) (archive)

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To port or not to port? (pros & cons)
i am thinking of installing some subs, has anyone on here done this before (port).

Sealed is easy to build as long as you get the volume right to the specs. Sealed is a lot quieter installation and takes a bigger box though. You likely need a pretty big amp to get loud volume from it since every time the speaker moves there is quite a lot of underpressure inside the box; thus it takes more power to move the cone.

If you go for ported installation the con is that you need to do it right, use one of the free computer programs which help you calculate the measures of the box and the diameter and length of the port (or ports) correctly. The pros are louder better sound (if the sub is meant for ported box of course) and a lot smaller box to build.

Then of course you could make a bandpass enclosure but those are really difficult to tune right and will only play a limited range of Mhz. Some really over-the-top pro comp builders have a bunch of subs in different bandpass enclosures (and crossovers to match) so that each sub will respond to certain frequency... Well I'm sure we all want to use our trunks as trunks and not just subwoofer enclosure compartment :-)

If you buy subs that are specifically meant for closed enclosures then naturally build one. Many are built so that they enable to use of either ported or closed enclosures, with naturally different volumes.

In my last megalomanic setup I actually had 2 Pioneer TS-W252F 12" free-air subs (was feeling too cheap to buy new ones since the crash of my former car) installed "isobarik", facing each other with the top one connected in reverse, so that they acted like one HUGE sub. I put them in a ported box but given their free-air nature they demanded a humongous 51,1 litre box even when ported. They sounded perfect though, I think I impaired my hearing with them (oops)... But Isobarik is only to be used if you have too many subs lying around or don't have much space. That car was a Touring (BMW STW, that box wouldn't have fit in a sedan anyway) so I didn't have to make any special tubing to deliver the sound to the cabin.

The optimal installation would have the sub AND the port both in touch with the cabin so that the box will suck in air vai ports from the same space (the cabin) as it blows air out via the subwoofer and vice versa when the sub returns to its normal, especially the e30 has problems with the trunk being too well sealed for the bass sound to travel to the cabin well.

The ski bag hole can be utilized to deliver the sound to the cabin (unless you have a ski bag that you want to use). Easiest way of course is to knock out the metal plate where ski bag would be installed. The negative effect is that the road noise will be delivered from the trunk as well. You could have the speaker facing the cabin and build a closed passage for the sound to travel to the cabin. Dunno what the rear seat back is like in the iL (electric seat right?) and if there is some sort of extra blockage compared to the normal rear seat. Would have to find out first.

Christine (my 750i) has kept me so busy with mechanical repairs that so far I've only upgraded the deck and front components (and changed the original rear speakers to a bit better but far from perfect ones) so subwoofer installation will take place next summer.

I intend to install a Kicker square sub in place of the ski bag which I have no use for (winter sports suck) and build a custom sub box by the rear seat/trunk front, with dual ports that point up and go through the rear deck. I'll upholster the rear deck with pass-through cloth that will hide the ports yet pass air through without resistance so it will still look stealth. Can always put the middle armrest up if I park the car in a nasty neighbourhood. I'll integrate the amp into the box and upholster it with similar cloth as the trunk is to make it look stealth in the trunk as well. (Yeah I'm all hyped abouth stealth systems since my last system showed a mile away)

If you intend to use several subs then a nice and likely very well working setup would have the ski hole removed, the two subs facing the hole at 90 degree angle towards each other (so that the 2 subs and ski hole for a triangle, excuse my english) and with separate ported box for each, the ports perhaps facing up thru the deck as I explained earlier or by the subs but I've read that the ports should NOT be really close to the subs so that might not sound as good as it could.

Whatever you do remember that in multi-subwoofer installation the subs MUST HAVE separate chambers which are never in open contact with each other.

And sealing is essential; especially the closed enclosure needs to be tight as a rock. (And so should the ported one) USe some sort of sealant that will NOT destroy your subs as many sealants produce gases which can damage the subs. I took a round of russian roulette in the last installation by using butyl sealant, dunno what it did to the subs but they seemed to work well for the full year and a half I had the car. I do NOT however encourage the use of butyl sealant; find out which is least harmful before sealing. And seal EVERYTHING with plenty of sealant.

Some people stuff the sub box full of cotton etc. which actually lowers the volume of the box and impairs the sound badly; I've fixed a few people's systems by opening the box and removing all cotton, then "fluffing" it and replacing one third of what was inside. The only use of cotton is removing the "echo" or at least so I recall (I'm at work and have no guides here).

Well, that's about it. For further sub Q's you can email my work address since I've been having trouble with both my home ISP and private email, here's the address:
henri.junkkala@huoltotrimmi.com

Well, my lunch hour ended 5 minutes ago so I'm off for a cig, good luck and remember that it is better to spend even 200 or 400 labour hours on a system that will sound perfect and work flawlwssly for years than to spend 2 hours quickly putting up something that won't satisfy you at all and that will corrode or have loose wires and leaks in a year or two.

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