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Simon Juncal
 
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Default unusual custom sub enclosure question

okay I've got the center console of a Jeep to use as a sub enclosure...
I've got an 8" JL 8W0 cocked at an angle roughly 45 degrees facing the
lid of the console. The inside dimensions (aprroximate due to curves in
the bottom) are 19" front to back, 8 3/4' wide by 7 3/4" deep. Not too
drastically off from JL's recommendations. However the sub will not be
firing out into the listening space, so I'm wondering what would be the
best way to compensate for that and the fact that the enclosure is
somewhat smaller than recommended and that the sub will be totally
enclosed. I've got a 2 1/2" PVC vent that I can cut down (JL recommends
2 1/2" by 12.4 but that's in a bigger box). So my question is with a
completely enclosed sub; should I use polyfill and a short vent, and
where along the length of the console should I mount the sub (at one end
or the other or in the middle?). Also should I face the sub towards the
vent or away from it?

If it sounds like crap I guess I'll end up getting a box and let it bang
around, but there's no good place for a sub enclosure in a jeep, and
hidden away inside the console is just too elegant to not at least try.

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

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Kevin McMurtrie
 
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Default unusual custom sub enclosure question

In article 3FFBCEFD.3030108@usefirstinitialandlastnameATerol s.com,
Simon Juncal
wrote:

okay I've got the center console of a Jeep to use as a sub enclosure...
I've got an 8" JL 8W0 cocked at an angle roughly 45 degrees facing the
lid of the console. The inside dimensions (aprroximate due to curves in
the bottom) are 19" front to back, 8 3/4' wide by 7 3/4" deep. Not too
drastically off from JL's recommendations. However the sub will not be
firing out into the listening space, so I'm wondering what would be the
best way to compensate for that and the fact that the enclosure is
somewhat smaller than recommended and that the sub will be totally
enclosed. I've got a 2 1/2" PVC vent that I can cut down (JL recommends
2 1/2" by 12.4 but that's in a bigger box). So my question is with a
completely enclosed sub; should I use polyfill and a short vent, and
where along the length of the console should I mount the sub (at one end
or the other or in the middle?). Also should I face the sub towards the
vent or away from it?

If it sounds like crap I guess I'll end up getting a box and let it bang
around, but there's no good place for a sub enclosure in a jeep, and
hidden away inside the console is just too elegant to not at least try.


I wouldn't use a port at all. It's asking for trouble when the box is
undersized and conditions aren't perfect. Most likely it will leak out
the low-end and buzz rather than create a mild resonation to help the
lowest frequencies. It will sound really bad if it buzzes badly enough
to make your CD player skip on certain notes.

The only kind of port likely to help would be a long and fat pipe that
adds to the box volume. A special speaker calculator is needed for
ports that are large compared to the enclosure. I've seen them before
online but don't remember where. It's probably more trouble than it's
worth, especially when it comes to routing a giant port under the dash.

Polyfill helps a sealed enclosure.

BTW, I do hope you're talking about an inclosure installed inside the
interior panels. The plastic panels alone won't hold much sound
pressure, maybe only 35W average without breaking or hissing from air
leaks. At least line it with fiberglass inside to stiffen it and form
an airtight seal.
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islandjeepman
 
Posts: n/a
Default unusual custom sub enclosure question

It sounds like you must have an older TJ. Newer ones have a grill by the
drivers seat for the "optional" subwoofer. As the system in a TY is so
crappy (I learned with my 2002) I did not order the upgraded system in my
2004. The center console still has the sub vent. You can pick up these on
ebay pretty cheap.

This weekend I will be installing an 8" Dayton Qu4tro Sub behind the grill.
I am powering it with a Blaupunkt amp (SMALL size) that I hope to mount in
the console. I hope for decent sound. Better than the crap DC sells in
J**ps. I replaced the horrible stock speakers with the Infinities I bought
for the 2002. The sub in the 2002 was lame at best. Hopefully this will be
good enough. I do not want the sub in a box in back. The only option I see
is the center console.

Stop by a J**p dealer and look at the center console. It will make sense.




"Simon Juncal" wrote in
message news:3FFBCEFD.3030108@usefirstinitialandlastnameAT erols.com...
okay I've got the center console of a Jeep to use as a sub enclosure...
I've got an 8" JL 8W0 cocked at an angle roughly 45 degrees facing the
lid of the console. The inside dimensions (aprroximate due to curves in
the bottom) are 19" front to back, 8 3/4' wide by 7 3/4" deep. Not too
drastically off from JL's recommendations. However the sub will not be
firing out into the listening space, so I'm wondering what would be the
best way to compensate for that and the fact that the enclosure is
somewhat smaller than recommended and that the sub will be totally
enclosed. I've got a 2 1/2" PVC vent that I can cut down (JL recommends
2 1/2" by 12.4 but that's in a bigger box). So my question is with a
completely enclosed sub; should I use polyfill and a short vent, and
where along the length of the console should I mount the sub (at one end
or the other or in the middle?). Also should I face the sub towards the
vent or away from it?

If it sounds like crap I guess I'll end up getting a box and let it bang
around, but there's no good place for a sub enclosure in a jeep, and
hidden away inside the console is just too elegant to not at least try.

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein



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Simon Juncal
 
Posts: n/a
Default unusual custom sub enclosure question

Kevin McMurtrie wrote:
I wouldn't use a port at all. It's asking for trouble when the box is
undersized and conditions aren't perfect. Most likely it will leak out
the low-end and buzz rather than create a mild resonation to help the
lowest frequencies. It will sound really bad if it buzzes badly enough
to make your CD player skip on certain notes.


I'll try without the port first but I worry about the sub not having any
access at all to outside air, all fully sealed boxes I've seen (where
the sub is mounted entirely inside the box I forget what this mounting
style is called), have had vents to let it push some outside air around.

The only kind of port likely to help would be a long and fat pipe that
adds to the box volume. A special speaker calculator is needed for
ports that are large compared to the enclosure. I've seen them before
online but don't remember where. It's probably more trouble than it's
worth, especially when it comes to routing a giant port under the dash.


Cool I'll do some googling and try to find it.

Polyfill helps a sealed enclosure.
BTW, I do hope you're talking about an inclosure installed inside the
interior panels. The plastic panels alone won't hold much sound
pressure, maybe only 35W average without breaking or hissing from air
leaks. At least line it with fiberglass inside to stiffen it and form
an airtight seal.


I've got some thin MDF I was going to use, but fiberglass might be
easier to deal with the curves. I hadn't thought about that thanks.

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

  #5   Report Post  
Simon Juncal
 
Posts: n/a
Default unusual custom sub enclosure question

islandjeepman wrote:
It sounds like you must have an older TJ. Newer ones have a grill by the
drivers seat for the "optional" subwoofer. As the system in a TY is so
crappy (I learned with my 2002) I did not order the upgraded system in my
2004. The center console still has the sub vent. You can pick up these on
ebay pretty cheap.


Actually an 88 YJ.

This weekend I will be installing an 8" Dayton Qu4tro Sub behind the grill.
I am powering it with a Blaupunkt amp (SMALL size) that I hope to mount in
the console. I hope for decent sound. Better than the crap DC sells in
J**ps. I replaced the horrible stock speakers with the Infinities I bought
for the 2002. The sub in the 2002 was lame at best. Hopefully this will be
good enough. I do not want the sub in a box in back. The only option I see
is the center console.


I just put some decent Kenwood 4x6's in the dash (no fun getting those
in) the boost in sound quality is amazing, good enough that I'm starting
to think I might get this Jeep to actually not sound like a Jeep But
that'll probably all go out the window once the hard top comes off and
the noisy soft top goes on in the spring.

Now all I have to figure out is where to put the damn amp, under the
seat leaves it potentially exposed to water (hate to fry my amp the
first time I get the Jeep stuck in mud up to the floorboards). Just
about anywhere else I put it will be visible... Nothing screams "I have
hundreds of dollars worth of stereo gear; steal it!" quite like a big
colorful amp. That's another reason I want the sub in the console, and
have relatively cheap Xplod 6x9's in the back enclosures.


Stop by a J**p dealer and look at the center console. It will make sense.


I know what you're talking about, there are aftermarket consoles that
have sub woofer options too. I hadn't really thought about swapping a TJ
console in, but if my little experiment fails that might be my next option.


--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein



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Kevin McMurtrie
 
Posts: n/a
Default unusual custom sub enclosure question

In article 3FFC3E2A.2070204@usefirstinitialandlastnameATerol s.com,
Simon Juncal
wrote:

Kevin McMurtrie wrote:
I wouldn't use a port at all. It's asking for trouble when the box is
undersized and conditions aren't perfect. Most likely it will leak out
the low-end and buzz rather than create a mild resonation to help the
lowest frequencies. It will sound really bad if it buzzes badly enough
to make your CD player skip on certain notes.


I'll try without the port first but I worry about the sub not having any
access at all to outside air, all fully sealed boxes I've seen (where
the sub is mounted entirely inside the box I forget what this mounting
style is called), have had vents to let it push some outside air around.


The hole isn't to let out air. It is to set up a resonance at a low
frequency (resonate like a large glass bottle does) where a sealed
enclosure would begin to perform poorly or have too much excursion.

Tuned port enclosures are common because they're louder than sealed
enclosures. Also, a large sealed enclosure may cause overexcursion in
the speaker because there's too little of an acoustic load. Adding a
tuned port increases the acoustic load at the tuned frequency. The
downside of a tuned port is that it can easily sound very bad when done
wrong. A sealed enclosure has a smooth frequency roll-off where a tuned
port enclosure has a very sharp drop-off below the tuned frequency.
Below the tuned port frequency, the port is just a big air leak.

Small enclosures are almost always best without a tuned port. They're
inefficient but they at least produce some deep bass. A small enclosure
with a tuned port will hum or buzz and produce no deep bass.

You can find frequency charts online that compare the two enclosures.


The only kind of port likely to help would be a long and fat pipe that
adds to the box volume. A special speaker calculator is needed for
ports that are large compared to the enclosure. I've seen them before
online but don't remember where. It's probably more trouble than it's
worth, especially when it comes to routing a giant port under the dash.


Cool I'll do some googling and try to find it.

Polyfill helps a sealed enclosure.
BTW, I do hope you're talking about an inclosure installed inside the
interior panels. The plastic panels alone won't hold much sound
pressure, maybe only 35W average without breaking or hissing from air
leaks. At least line it with fiberglass inside to stiffen it and form
an airtight seal.


I've got some thin MDF I was going to use, but fiberglass might be
easier to deal with the curves. I hadn't thought about that thanks.

  #7   Report Post  
Simon Juncal
 
Posts: n/a
Default unusual custom sub enclosure question

Kevin McMurtrie wrote:
In article 3FFC3E2A.2070204@usefirstinitialandlastnameATerol s.com,
Simon Juncal
wrote:


Kevin McMurtrie wrote:

I wouldn't use a port at all. It's asking for trouble when the box is
undersized and conditions aren't perfect. Most likely it will leak out
the low-end and buzz rather than create a mild resonation to help the
lowest frequencies. It will sound really bad if it buzzes badly enough
to make your CD player skip on certain notes.


I'll try without the port first but I worry about the sub not having any
access at all to outside air, all fully sealed boxes I've seen (where
the sub is mounted entirely inside the box I forget what this mounting
style is called), have had vents to let it push some outside air around.



The hole isn't to let out air. It is to set up a resonance at a low
frequency (resonate like a large glass bottle does) where a sealed
enclosure would begin to perform poorly or have too much excursion.

Tuned port enclosures are common because they're louder than sealed
enclosures. Also, a large sealed enclosure may cause overexcursion in
the speaker because there's too little of an acoustic load. Adding a
tuned port increases the acoustic load at the tuned frequency. The
downside of a tuned port is that it can easily sound very bad when done
wrong. A sealed enclosure has a smooth frequency roll-off where a tuned
port enclosure has a very sharp drop-off below the tuned frequency.
Below the tuned port frequency, the port is just a big air leak.

Small enclosures are almost always best without a tuned port. They're
inefficient but they at least produce some deep bass. A small enclosure
with a tuned port will hum or buzz and produce no deep bass.


Excellent explanation. I've got the sub temporarilly inside the console
(which is a work in progress) with no port and I'm getting the idea that
it will actually sound decent. It actually sounds pretty good just
sitting free inside (not rattling on anything), which is obviously very
inefficient. It thumps a lot harder mounted, once I get the walls
reinforced with fiberglass, and fabricate a sealable top and polyfill
it, it should thoeretically smooth out again right?

--
Simon
"I may be wrong, but I'm not uncertain." -- Robert A. Heinlein

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