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post #1 of 33 (permalink) Old 03-28-2008, 10:57 PM Thread Starter
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building a down firing box.

i have seen it said that you need a speaker that is suspended stiffer to do it so it will not sag. is this fact/myth/BS/or somebody assuming. i also saw it said that it would take more power to operate because gravity would make it harder for the cone to come back into the basket. i just can not see this because in theroy then, it would take less for foward excursion and speakers want to return to center naturally anyway.

the reason i ask is because i am going from a sedan with a truck mounted sub, to an X-cab and want to point the sub down to hide it and protect it from damaged. it will also allow me to still use the back as storage.

last question, what is the min backspacing i need from the magnet to the back of the box. it is a decent twelve that most likely never sees more than 100watts max.

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post #2 of 33 (permalink) Old 03-29-2008, 01:03 AM
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100 watts max is not enough for a 12... the sub is most likely rated at (and NO less than) 100 RMS

if you actually play that low of power most the time, you should prob consider a 10 or even an 8 and would get better sound as well as much more room to build a nice box.

the magnet does not need much clearance. 1 inch should be good prob even half. just remember you need to put legs on the bottom of the box so the sub has room to move around and is not constantly rubbing (sounds like shit and wears your surround quick)

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post #3 of 33 (permalink) Old 03-29-2008, 07:52 AM
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what sub(s) u running. some subs require 2" to cool off



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post #4 of 33 (permalink) Old 03-29-2008, 08:09 AM
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There are air space specifications for every speaker but generally a 12 inch requires no less then 1 cubic foot of air space, not saying you need a foot from the magnet to the back wall of the box, I am saying if you have 2 inches of space to the wall you just need to make up the space in the height and width of the box. This is the reason truck boxes have little depth but are larger than most boxes in height and width.
100 Watts is plenty if it is coming from a clean source. I give 120 Watts at 1/2 ohm to two DVC JL 10's in series and would put it in a SPL contest with anyone.
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post #5 of 33 (permalink) Old 03-29-2008, 08:13 AM
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Originally Posted by PGreenCobra
100 Watts is plenty if it is coming from a clean source. I give 120 Watts at 1/2 ohm to two DVC JL 10's in series and would put it in a SPL contest with anyone.
i wouldnt open ur mouth too much. This is texas and errything is bigger in Texas lol



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post #6 of 33 (permalink) Old 03-29-2008, 09:13 AM
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Quote:
Originally Posted by SNEAKY
i have seen it said that you need a speaker that is suspended stiffer to do it so it will not sag. is this fact/myth/BS/or somebody assuming. i also saw it said that it would take more power to operate because gravity would make it harder for the cone to come back into the basket. i just can not see this because in theroy then, it would take less for foward excursion and speakers want to return to center naturally anyway.
I have never heard that and if true, an upfiring woofer would sag into the basket. Bunk.


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last question, what is the min backspacing i need from the magnet to the back of the box. it is a decent twelve that most likely never sees more than 100watts max.
None, unless the woofer has a vented pole piece. Vented pole will require room for airflow to cool voice coil. You should contact the manufacturer for their advise.
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post #7 of 33 (permalink) Old 03-29-2008, 10:18 AM Thread Starter
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Originally Posted by EW
I have never heard that and if true, an upfiring woofer would sag into the basket. Bunk.
kinda what i thought


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Originally Posted by EW
None, unless the woofer has a vented pole piece. Vented pole will require room for airflow to cool voice coil. You should contact the manufacturer for their advise.
it is vented. i thought about trying to mount it at slight angle(not sure if i can build anything more than a square cornered box) to keep the height to a min, but still allow for plenty of air to the magnet.

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post #8 of 33 (permalink) Old 03-29-2008, 11:22 AM
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Originally Posted by PGreenCobra
I give 120 Watts at 1/2 ohm to two DVC JL 10's in series and would put it in a SPL contest with anyone.

AHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!!!!!!!!!!!!!!

Breathe.

AHAHAHAHAHAHAHAHAHAHAHAHAHAHAHA!!!!!!!!!!!!!!

Thank you for the entertainment.
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post #9 of 33 (permalink) Old 03-30-2008, 11:24 PM
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Originally Posted by PGreenCobra
100 Watts is plenty if it is coming from a clean source. I give 120 Watts at 1/2 ohm to two DVC JL 10's in series and would put it in a SPL contest with anyone.
theres way too much wrong with that statement for me to even pick at lol... im just gonna have to laugh it off like jluv. i seriously had to read that post about 4 times to make sure i didnt misread what you were saying... i didnt, Lol!

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post #10 of 33 (permalink) Old 03-30-2008, 11:26 PM
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BTW, coolest smiley gif ever made definitely goes to slam

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post #11 of 33 (permalink) Old 03-30-2008, 11:56 PM
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down fire boxes

Well i speak from experience, a 10" woofer needs 3" from the floor, 12"- 4" and a 15" needs 5" of clearance. Also the more air space you have behind the woofer the better or tighter the response you will get. Make sure you go with the recommended air space the woofer calls for. If you already have the 100W amp hook it up and try it before you go out and spend the money on a new amp. one more thing your system will only sound as good as the headunit, so don't go cheap on that.
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post #12 of 33 (permalink) Old 03-31-2008, 12:02 AM Thread Starter
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Originally Posted by rainman64
Well i speak from experience, a 10" woofer needs 3" from the floor, 12"- 4" and a 15" needs 5" of clearance. Also the more air space you have behind the woofer the better or tighter the response you will get. Make sure you go with the recommended air space the woofer calls for. If you already have the 100W amp hook it up and try it before you go out and spend the money on a new amp. one more thing your system will only sound as good as the headunit, so don't go cheap on that.
oh, its a 400watt amp, but i doubt i run more than 100 to it.

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post #13 of 33 (permalink) Old 03-31-2008, 05:56 AM
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Quote:
Originally Posted by NeedleSharp
BTW, coolest smiley gif ever made definitely goes to slam
thank u thank u lol



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post #14 of 33 (permalink) Old 03-31-2008, 01:44 PM
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Quote:
Originally Posted by NeedleSharp
theres way too much wrong with that statement for me to even pick at lol... im just gonna have to laugh it off like jluv. i seriously had to read that post about 4 times to make sure i didnt misread what you were saying... i didnt, Lol!

120watts at 1/2 an ohm could easily be 2000+ watts depending on the cheater amp. My XS-100 is only 50x2 at 4 ohm stereo but puts out an easy 1700 watts at 1ohm mono bridged. Run it at 1/2 an ohm with 16 volts and it'd be 2500+ watts right before it started smoldering.

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post #15 of 33 (permalink) Old 03-31-2008, 02:04 PM
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Originally Posted by BP
120watts at 1/2 an ohm could easily be 2000+ watts depending on the cheater amp. My XS-100 is only 50x2 at 4 ohm stereo but puts out an easy 1700 watts at 1ohm mono bridged. Run it at 1/2 an ohm with 16 volts and it'd be 2500+ watts right before it started smoldering.
how? 120watts @ .5 ohms would be (very dependent on amp and very aprox) around 60 watts @ 1 ohm and 30 watts @ 2 ohms unless i am just very, very confused...

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post #16 of 33 (permalink) Old 03-31-2008, 02:28 PM
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Quote:
Originally Posted by BP
120watts at 1/2 an ohm could easily be 2000+ watts depending on the cheater amp. My XS-100 is only 50x2 at 4 ohm stereo but puts out an easy 1700 watts at 1ohm mono bridged. Run it at 1/2 an ohm with 16 volts and it'd be 2500+ watts right before it started smoldering.

i had one of those amps at .5 an ohm and didnt like it. Matter of fact i bought it from u and i sold it. They say it puts out over a 1000+ watts but its really about 900 bridged at 1ohm 12.5 volts; and if its at 14.4volts thats about 20% more. 2500+ watts come on man




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post #17 of 33 (permalink) Old 03-31-2008, 02:45 PM
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Quote:
Originally Posted by BP
120watts at 1/2 an ohm could easily be 2000+ watts depending on the cheater amp. My XS-100 is only 50x2 at 4 ohm stereo but puts out an easy 1700 watts at 1ohm mono bridged. Run it at 1/2 an ohm with 16 volts and it'd be 2500+ watts right before it started smoldering.
Got any spec sheets, links, or any good reading to back that up? Those are crazy numbers you are throwing out and I'd love to learn more about it.

I'm still LMAO at the guy saying he will put his two JL 10s up against anyone in an SPL contest.
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post #18 of 33 (permalink) Old 03-31-2008, 02:50 PM
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Originally Posted by jluv
Got any spec sheets, links, or any good reading to back that up? Those are crazy numbers you are throwing out and I'd love to learn more about it.

I'm still LMAO at the guy saying he will put his two JL 10s up against anyone in an SPL contest.

here is the pdf on the amp

http://rds.yahoo.com/_ylt=A0oGkyRyS_.../XSAmpsMan.pdf

and heres amp guts site. scroll about hlfway down

http://ampguts.realmofexcursion.com/



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post #19 of 33 (permalink) Old 03-31-2008, 03:00 PM
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Originally Posted by slam
i had one of those amps at .5 an ohm and didnt like it. Matter of fact i bought it from u and i sold it. They say it puts out over a 1000+ watts but its really about 900 bridged at 1ohm 12.5 volts; and if its at 14.4volts thats about 20% more. 2500+ watts come on man

not that it was a bad amp. just needed more power for a new setup



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post #20 of 33 (permalink) Old 03-31-2008, 11:25 PM
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Some of you guys crack me up. If you have a 100w amp, rated at 4 ohms stereo, and are running it at 1 ohm mono, then you can't say that you're only running 100w, although that might be the rating of the amp.

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post #21 of 33 (permalink) Old 03-31-2008, 11:58 PM Thread Starter
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Some of you guys crack me up. If you have a 100w amp, rated at 4 ohms stereo, and are running it at 1 ohm mono, then you can't say that you're only running 100w, although that might be the rating of the amp.
you aren't talking about me are you?

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post #22 of 33 (permalink) Old 04-01-2008, 12:40 AM
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Originally Posted by ThreeFingerPete
Some of you guys crack me up. If you have a 100w amp, rated at 4 ohms stereo, and are running it at 1 ohm mono, then you can't say that you're only running 100w, although that might be the rating of the amp.
im not really sure who your talking to but i do understand and know what you are saying. and im really not trying to be a smart ass when i say this but i dont understand how a 50x2 @ 4 ohms can put out 2500 watts @ .5 ohms... not arguing just looking for some kind of explanation because something like that is Very foreign to me.

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post #23 of 33 (permalink) Old 04-01-2008, 09:01 AM
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Originally Posted by NeedleSharp
im not really sure who your talking to but i do understand and know what you are saying. and im really not trying to be a smart ass when i say this but i dont understand how a 50x2 @ 4 ohms can put out 2500 watts @ .5 ohms... not arguing just looking for some kind of explanation because something like that is Very foreign to me.
Then do a little research. An amplifier will approximately double its power for every halving of resistance. So [email protected] ohms stereo is [email protected] 8 ohms, approximately [email protected], [email protected], [email protected], [email protected] ohms. Now, obviously most amplifiers won't run at 1/16th of their rated impedance, but some will. Plus all of those amps are unregulated, so if they were rated at 13v, and you can put 15-16 into them, the power output will increase significantly.

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post #24 of 33 (permalink) Old 04-01-2008, 10:37 AM
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i new that worked in theory but i didnt know most amps were actually capable of putting out that much power... interesting...

also i forgot to double the initial wattage for the bridge so the final was half as much... my bad.

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post #25 of 33 (permalink) Old 04-01-2008, 11:32 AM
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Quote:
Originally Posted by NeedleSharp
i new that worked in theory but i didnt know most amps were actually capable of putting out that much power... interesting...

also i forgot to double the initial wattage for the bridge so the final was half as much... my bad.
Most amps (99%) are NOT capable of doubling their power into 1/2 the resistance. Now, start asking about current required for that much power, voltage required, how long they will operate at stupid-low loads, the damping factor at 1/2 ohm, etc. I'll pass on all of that.
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post #26 of 33 (permalink) Old 04-01-2008, 12:59 PM
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down fire boxes

As most amps go they are only between 60 or 70% efficient unless they are digital and then those are not 100%.
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post #27 of 33 (permalink) Old 04-01-2008, 01:03 PM Thread Starter
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wow, this went form a down firing box question to a discussion of Ohms and amplifier efficiency

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post #28 of 33 (permalink) Old 04-01-2008, 01:56 PM
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wow, this went form a down firing box question to a discussion of Ohms and amplifier efficiency
what other questions do you have? we are more than happy to answer them but it seemed as though there arent any more questions so i felt that is was necessary to jack the thread

its actually relevant to what you were saying about 100 watts max. regardless of what the resistance is, if you want 100 watts max then its 100 watts. thats MY point. how you achieve the 100 watts you want doesnt really matter.

my point is you wont get great sound from a 12" sub with only 100 watts. get a quality 10" with some head room (100 RMS is a good start for a small cabin) and i think you'll be much happier

also, i would love to hear anyone with a down firring box with a nice setup. i also have a truck and am going through the sub mounting problem but have just thrown a big box on my rear bench for the past 2 years. my only worry is the higher freq roll-off on a down firring box... i've only heard lower end setups and dont like the way they sound at all...

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post #29 of 33 (permalink) Old 04-02-2008, 01:05 AM Thread Starter
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what other questions do you have? we are more than happy to answer them but it seemed as though there arent any more questions so i felt that is was necessary to jack the thread

its actually relevant to what you were saying about 100 watts max. regardless of what the resistance is, if you want 100 watts max then its 100 watts. thats MY point. how you achieve the 100 watts you want doesnt really matter.

my point is you wont get great sound from a 12" sub with only 100 watts. get a quality 10" with some head room (100 RMS is a good start for a small cabin) and i think you'll be much happier

also, i would love to hear anyone with a down firring box with a nice setup. i also have a truck and am going through the sub mounting problem but have just thrown a big box on my rear bench for the past 2 years. my only worry is the higher freq roll-off on a down firring box... i've only heard lower end setups and dont like the way they sound at all...
if you have wood working skills, you are more than welcome to help me build the box.

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post #30 of 33 (permalink) Old 04-02-2008, 06:08 AM
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if you have wood working skills, you are more than welcome to help me build the box.
was that an invitation or a smart ass comment? i couldnt tell

you supply the beer and the tools and im there man. unless your being a jackass then i will come to piss on your vehicle

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post #31 of 33 (permalink) Old 04-02-2008, 07:01 AM
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wow, this went form a down firing box question to a discussion of Ohms and amplifier efficiency

Yep...and some of the experts (ahem, jailbird from Kansas) need to go back to school...lemme throw out this equation/educational reading:


http://www.the12volt.com/ohm/ohmslaw.asp


I've heard BP's set up...and it works
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post #32 of 33 (permalink) Old 04-02-2008, 11:32 AM Thread Starter
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was that an invitation or a smart ass comment? i couldnt tell

you supply the beer and the tools and im there man. unless your being a jackass then i will come to piss on your vehicle
it was an invite. it would be a week or two till i am ready. i should have other stuff in today and will put it in first.

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post #33 of 33 (permalink) Old 04-02-2008, 02:50 PM
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cool man shoot me a PM whenever

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