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GhEttOrAiD
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Seal my subwoofer box, or don't.

Took another look at the botched-to-shit setup in my trunk.

Decided to replace my two Kenwood amps with a single class D mono amp (which shall remain unnamed)

In the thread where I was trying to get feedback on what amp I should pick, somebody thought to ask whether my box was ported. It is. And the box is alarmingly small (When you consider that it houses two 15" Kicker L5's.)

According to Kicker's documentation on these subs, ONE sub requires at least 3 cubic feet of in-box volume, if the box is ported.

I have TWO of these subs, so, I would need a SIX cubic foot enclosure. That's not gonna happen. However, if the box is SEALED, the interior volume recommended goes down to 1.5 per speaker. So 3 cubic feet. Really, the box is still nowhere near this capacity. BUT... Here's the question.

Should I slap a strip of MDF into the port? Seal it up, get "closer" to the recommended configuration for the subs?

I was told by a third party that the subs wouldn't hit as hard, or be as loud.
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Old 02-01-2012, 01:03 AM GhEttOrAiD is offline  
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mikeawesome
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you should remove the subs
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Old 02-01-2012, 01:10 AM mikeawesome is offline  
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GhEttOrAiD
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you should remove the subs

I'm not really ready to invest in the hardware required to deliver targeted bass across space/time, so this isn't an option.
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Old 02-01-2012, 01:13 AM GhEttOrAiD is offline  
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Nevermore
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Is the box divided?

Seems like you're probably going to waste time for no real gain, did the new amp make any noticeable improvement?
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Old 02-01-2012, 06:21 AM Nevermore is offline  
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Please learn how to design a proper sub enclosure, before you bounce your subs off their Xmax, destroy them, and come on here asking what happened. Running a sub in an improperly designed ported box can be almost as bad as running them in free air.

Go with a sealed setup. A sealed box isn't as capable of low frequency extension as a ported box, and has a theoretical gain 3dB below a ported box. But a sealed box has less phase delay so it'll subjectively "hit harder", and accurate low frequency reproduction doesn't seem important in this case since you're looking for a system that "hits hard". Most importantly, about the only error you can make with a sealed box is making the box too big and driving it with too much power, exceeding the Xmax of your subs.

So yes, seal your box's port. However, seal it from the inside, use a piece of hardwood plywood (or straight hardwood) instead of MDF, make sure it fits well and use a proper adhesive like 'no more nails' to glue it in place. Make sure the glue dries for a few days, so all VOCs outgass from the glue, before you reinstall the subs.

As for your "unnamed amp", every amplifier built nowadays is pretty much equally craptastic - I've seen horrible things done inside amplifiers that I'd normally associate with good names, and I've actually seen well designed "crap". One of the best designed amps I've ever worked on was a Jensen, believe it or not.
Old 02-01-2012, 07:06 AM gee is offline  
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One of the best designed amps I've ever worked on was a Jensen, believe it or not.

MATE! One of the BEST fucking amps I ever owned was Jensen, I had no clue the day I bought it that it would be such a fucking killer amp!
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Old 02-01-2012, 07:14 AM Nevermore is offline  
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I would also highly recommend not driving 2 subs sealed in a common chamber configuration. They should each be in their own sealed chamber.
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Old 02-01-2012, 01:22 PM Typhoon43 is offline  
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What if he added some poly fill to the box? Would that not help at least somewhat with it being the incorrect size?
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Old 02-01-2012, 01:33 PM Lurker is offline  
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What if he added some poly fill to the box? Would that not help at least somewhat with it being the incorrect size?

Stuffing makes a box appear larger to the driver because it slows down the sound waves, physically, as in the time it takes for them to return. You can reach up to a 30% perceived increase but if you stuff it too tight you will actually be reducing volume. Stuffing a sealed box is always recommended since you can't have too big of a box. Stuffing a ported system affect tuning and should be done carefully.


Ghetto - the thing with ported versus sealed is it should reflect the type of drivers you have. Some drivers are meant for ported, some for sealed and some can go either way. Plugging up ports is common for the sake of experimentation - or slots in your case it sounds like, which is just a cheaper version of a flared, rounded port which is ideal. If you had rounded ports you could simply use tennis balls, or anything else that fits. Similarly you can use whatever you can think of for the slot port. Don't make it too permanent at first in case you don't like it.

Personally I think two fifteens is retarded in a small car. In any car really. To twelves is retarded. If you never reach their limits, what's the point of having it? They would be barely moving before outplaying the rest of your system, and the whole time you lose accuracy with huge sloppy cones - a single 12 is plenty unless you simply want to ruin your ears and annoy people. I think you need to remove one fifteen completely, run a single in a sealed box if the driver is compatible with sealed cabs.
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Old 02-01-2012, 03:14 PM [H]ard|On is offline  
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gee
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I would also highly recommend not driving 2 subs sealed in a common chamber configuration. They should each be in their own sealed chamber.
Provided they're driven with the same signal at the same amplitude, they're fine. Lots of pro audio speakers are constructed that way. Just don't wire the speakers with opposite polarity, then you'll have problems.
Old 02-01-2012, 03:37 PM gee is offline  
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GhEttOrAiD
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Please learn how to design a proper sub enclosure, before you bounce your subs off their Xmax, destroy them, and come on here asking what happened. Running a sub in an improperly designed ported box can be almost as bad as running them in free air.

Go with a sealed setup. A sealed box isn't as capable of low frequency extension as a ported box, and has a theoretical gain 3dB below a ported box. But a sealed box has less phase delay so it'll subjectively "hit harder", and accurate low frequency reproduction doesn't seem important in this case since you're looking for a system that "hits hard". Most importantly, about the only error you can make with a sealed box is making the box too big and driving it with too much power, exceeding the Xmax of your subs.

So yes, seal your box's port. However, seal it from the inside, use a piece of hardwood plywood (or straight hardwood) instead of MDF, make sure it fits well and use a proper adhesive like 'no more nails' to glue it in place. Make sure the glue dries for a few days, so all VOCs outgass from the glue, before you reinstall the subs.

As for your "unnamed amp", every amplifier built nowadays is pretty much equally craptastic - I've seen horrible things done inside amplifiers that I'd normally associate with good names, and I've actually seen well designed "crap". One of the best designed amps I've ever worked on was a Jensen, believe it or not.

Well, as long as the consensus is that all amps are shit... I'm a few minutes from pulling the trigger on a Hifonics 1200.1D. I will be rewiring the subs so that they are in parallel, will work out to be a 1ohm load (or so I'm told.)


Are you saying I should seal each sub independently? (option 1 vs option 2)

I was planning to use JBWeld, because I happen to have a pretty huge quantity on hand. Dad might have a tube of Liquid Nails somewhere...

Quote:
Originally Posted by [H]ard|On View Post
Personally I think two fifteens is retarded in a small car. In any car really. To twelves is retarded. If you never reach their limits, what's the point of having it? They would be barely moving before outplaying the rest of your system, and the whole time you lose accuracy with huge sloppy cones - a single 12 is plenty unless you simply want to ruin your ears and annoy people. I think you need to remove one fifteen completely, run a single in a sealed box if the driver is compatible with sealed cabs.

Yeah, this is one of the points made in my "what amp to buy" thread. They didn't dare say "thats too much speaker!!" it was basically just "sell the amps sell one driver buy a larger single sub box.
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Old 02-01-2012, 07:09 PM GhEttOrAiD is offline  
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Hifonics amp ordered... We'll see what happens I guess.
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Old 02-01-2012, 08:20 PM GhEttOrAiD is offline  
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One would think seal the ports at the ends... But I could be totally wrong, I have been before with car audio.
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Old 02-01-2012, 08:39 PM Tex Arcana is offline  
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One would think seal the ports at the ends... But I could be totally wrong, I have been before with car audio.

yeah, if you seal off part of the box you will further reduce the internal volume.

also that seems like it would be harder to do.
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Old 02-01-2012, 08:47 PM pyramid is offline  
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[H]ard|On
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Cut a piece of MDF the size of the port and screw the thing in with drywall screws. Use a sealant of your choice for cracks.

Not rocket science.



Also dual mono drivers in the same space is fine - for stereo bass you MUST have separate cabs or a partition, but otherwise no since they always play the same thing and hit at the exact same time.
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Old 02-01-2012, 08:59 PM [H]ard|On is offline  
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