# Should I worry about blowing a sub <20hz?



## LiquidClen (Dec 27, 2005)

I see a lot of people telling me to port a sub for HT at 20hz, 21 hz, etc. and I know a lot of movies contain content sub-20hz... How should much should I worry?

I want to do a 12W7 ported with maybe 500W (not sure if I can afford much more power) for those wondering


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## 6APPEAL (Apr 5, 2007)

Mine is ported at 28 Hz. No problems here.
John


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## 60ndown (Feb 8, 2007)

i doubt you can hurt a 12w7 with 500 watts. even free air.

in fact at tuning 20hz there is the least amount of hexcursion.


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## LiquidClen (Dec 27, 2005)

60ndown said:


> i doubt you can hurt a 12w7 with 500 watts. even free air.
> 
> in fact at tuning 20hz there is the least amount of hexcursion.


what about 1000?


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## poochieone (Aug 25, 2005)

1000 wrms is well beyond the manufacturer's thermal power rating for long term use. on a 13W7,, maybe, but i think the 12W7 will fail if fed that much power over the long run.


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## thadman (Mar 1, 2006)

Why don't you model it in WinISD and let us know? There are way too many variables to consider beyond "ported, 500 watts".

FYI make sure you model the filter you plan on using, otherwise excursion may look a little scary.


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## 60ndown (Feb 8, 2007)

LiquidClen said:


> what about 1000?


1000 wrms on a movie?

i bet your neibours love you,







nnnnnnnnaaaaaaaaaaawwwwwwwwttttttttttt.


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## Amish (Oct 2, 2006)

Eh, it's not that bad. I've got a 1000W plate amp on a 15" Adire Tumult with a pair of 18" passive radiators. When played at normal listening levels I've got things matched to wear it blends well and doesn't bloat on the bottom end. Crank some movies and watch the drywall flex though  .

As recommended before, plot the response in WinISD or Unibox and figure out how much power will be required to bottom the driver out. You've gotta realize that's also driving at full-tilt, I doubt you'll really see that 500W or 1000W or whatever all that often. I can tell you that my sub (parts above ~18Hz tune) gets NOWHERE near peak excursion even at "loud" levels. Tune low and be happy. Depending on the amp you use it may have a subsonic filter as well, mine's at 18Hz  , if I didn't just have to dump a bunch of cash into the daily driver I'd think about a pro-amp so I could let her sing full frequency.


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## Diru (May 23, 2006)

I don't know, should you be worried about blowing a sub?


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## demon2091tb (May 30, 2005)

I have a single tempest in 7cf tuned to 21hz and i'm perfectly fine, i watch it at louder than normal movies because huge excursion on any driver just scares me, but its perfectly fine, 250rms on it, adding another here in a few months so each in 8cf tuned at 16hz with 250on each.......Not looking for huge huge huge bass but just linear output to the single digits at my typical volume level, which should meet nicely.

You just gotta know how loud you can take it safely and at what frequencies......i've gotten that sweat a few times during a few differnet movies, ie RE2, LOTR's and a few others, but its still going very strong.....just backed down a few dbs and kept going.


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## unpredictableacts (Aug 16, 2006)

Anyone have an enclosure design that would suit the W7 in a HT set up the best?


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## Robert_J (Nov 9, 2006)

60ndown said:


> 1000 wrms on a movie?


 I have a 2,400w Behringer EP-2500 powering a pair of 15" TC-3000's. I don't even think my neighbors know I have a theater.



thadman said:


> Why don't you model it in WinISD and let us know? There are way too many variables to consider beyond "ported, 500 watts".
> 
> FYI make sure you model the filter you plan on using, otherwise excursion may look a little scary.


 Modeling is the only accurate way to do this without testing the driver/enclosure after it is built. I prefer Unibox for my modeling.



Amish said:


> Eh, it's not that bad. I've got a 1000W plate amp on a 15" Adire Tumult with a pair of 18" passive radiators. When played at normal listening levels I've got things matched to wear it blends well and doesn't bloat on the bottom end.


 This should be required reading for anyone getting into home theater. A Radio Shack SPL meter and a home theater calibration DVD are a must for minimum proper setup. Your ears are not reliable.



Amish said:


> Crank some movies and watch the drywall flex though  .


 I like to play a 10hz test tone. My subs are moving like crazy and my drywall is making all kinds of noise. And my theater room door is shaking violently like someone is trying to break it down.



unpredictableacts said:


> Anyone have an enclosure design that would suit the W7 in a HT set up the best?


 There is no "best". There are enclosure designs that will help you reach your goals for the low end of your system. The goals have not been stated though.

Like others have mentioned, tune it low. How low? How low do you want to accurately reproduce the LFE signal? Do you want to feel the 12hz material in War of the Worlds or the 8hz material in Black Hawk Down? You need to go very large and tune very low. Another option is go sealed and apply EQ. Even better, go with an IB. But that will require much more than a single 12" sub. I'm building my IB with four 18" TC Sounds/Fi Car Audio subs.

-Robert


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## 60ndown (Feb 8, 2007)

Robert_J said:


> Even better, go with an IB. But that will require much more than a single 12" sub.
> 
> -Robert


nonsense 

http://www.diymobileaudio.com/forum/showthread.php?t=31369


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## unpredictableacts (Aug 16, 2006)

Liquid how low do we want to go?


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## Robert_J (Nov 9, 2006)

60ndown said:


> nonsense
> 
> http://www.diymobileaudio.com/forum/showthread.php?t=31369


 That's just a sealed box. I mean an IB like this.

-Robert


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## 60ndown (Feb 8, 2007)

Robert_J said:


> That's just a sealed box. I mean an IB like this.
> 
> -Robert


i believe 5 x the vas of the driver = i.b., 

so it doesnt matter how its achieved, easy or hard, once your over 5x the vas it is in fact, i.b.


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## demon2091tb (May 30, 2005)

60ndown said:


> i believe 5 x the vas of the driver = i.b.,
> 
> so it doesnt matter how its achieved, easy or hard, once your over 5x the vas it is in fact, i.b.


As long as the front and back waves are seperated yes.


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## 60ndown (Feb 8, 2007)

demon2091tb said:


> As long as the front and back waves are seperated yes.


t.y.


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## Robert_J (Nov 9, 2006)

60ndown said:


> i believe 5 x the vas of the driver = i.b.,
> 
> so it doesnt matter how its achieved, easy or hard, once your over 5x the vas it is in fact, i.b.


 Thomas_W and his Cult of the Infinitely Baffled site is the default site for all things IB. Recommended size is 10x Vas with 4x Vas being minum. I'd still call yours a large box.

-Robert


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## 60ndown (Feb 8, 2007)

Robert_J said:


> Thomas_W and his Cult of the Infinitely Baffled site is the default site for all things IB. Recommended size is 10x Vas with 4x Vas being minum. I'd still call yours a large box.
> 
> -Robert


im crap at math, but the diyma is designed to work optimally in a very small box(.5) cubic i believe, my 'large box' is about 4 feet long and 12" diamiter, that has got to be well over 4 x vas of the driver and probably closer to 10x.

i call your i.b. install, 'absurd overkill'

even if i cant spell 

i had 2 x 12" rl-p in my van on 2500 wrms a while back, they are great subs.



















http://techronics.com/index.cfm?fuseaction=product.display&product_id=1829&aff=72182


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## LiquidClen (Dec 27, 2005)

thadman said:


> Why don't you model it in WinISD and let us know? There are way too many variables to consider beyond "ported, 500 watts".
> 
> FYI make sure you model the filter you plan on using, otherwise excursion may look a little scary.


I'm a n00b and don't know anything about box modeling or WinISD  
What other variable do you need to know?



unpredictableacts said:


> Liquid how low do we want to go?


As low as possible  Hell let's try to play that 8hz stuff in Black Hawk Down  



For everybody's reference, my "theater" is just going to be my room. It's a fairly medium-sized room (16x14 IIRC) so I don't want something that will make my dry-wall flex lol, just some accurately loud (subjective term, I know) reproduction of movie content.


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## unpredictableacts (Aug 16, 2006)

Well anyone have a rough design to get the W7 to reproduce a 8hz note?somthing about table hieght....probably no taller than 2'.


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## LiquidClen (Dec 27, 2005)

unpredictableacts said:


> Well anyone have a rough design to get the W7 to reproduce a 8hz note?somthing about table hieght....probably no taller than 2'.


I can go about 2-2.5' high, probably 5' wide. Depth... maybe 1.5-2'? I'll try to get measurements tonight

*EDIT*
My #1 goal is SQ for those wondering


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## Oliver (Jun 25, 2007)

LiquidClen said:


> I see a lot of people telling me to port a sub for HT at 20hz, 21 hz, etc. and I know a lot of movies contain content sub-20hz... How should much should I worry?
> 
> I want to do a 12W7 ported with maybe 500W (not sure if I can afford much more power) for those wondering


Tune it low.[ 7 hz ]

Don't worry!


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## thylantyr (Jan 21, 2008)

> Why don't you model it in WinISD and let us know?


I've been watching for forum for a month now and it seems
people avoid simple woofer modeling..... like vampires avoiding the sun and garlic.


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## thylantyr (Jan 21, 2008)

> I'm a n00b and don't know anything about box modeling or WinISD


That's not a problem. Try these two forums. They talk
about woofers for home audio all the time.

http://www.avsforum.com/avs-vb/forumdisplay.php?f=155

http://www.hometheatershack.com/forums/diy-subwoofers/

http://www.diyaudio.com/forums/forumdisplay.php?forumid=63


WinISD if free, a small learning curve, but it is very good
vs. guessing.

http://www.linearteam.dk/default.aspx?download=winisdpro

Perhaps somewhere in this forum, a tutorial on WinISD? I don't remember where
I saw it... lol


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## chad (Jun 30, 2005)

thylantyr said:


> WinISD if free, a small learning curve, but it is very good
> vs. guessing.
> 
> http://www.linearteam.dk/default.aspx?download=winisdpro
> ...


I would go with WinISD BETA as opposed to pro for the beginner, pro can be a REAL Bish at first!


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## Robert_J (Nov 9, 2006)

60ndown said:


> i call your i.b. install, 'absurd overkill'


Even though that is not mine (it was the quickest example I could find), I consider it a complement. I'm going for 'absurd overkill'. Those are just 15's in my link. I'm building four 18's with TC9 motors and Fi recones that are tweaked by Scott to work better in an IB. If four isn't enough, I have enough parts for two more.



60ndown said:


> i believe 5 x the vas of the driver = i.b.,
> 
> so it doesnt matter how its achieved, easy or hard, once your over 5x the vas it is in fact, i.b.


 But you didn't achieve it. Based on your 12" diameter, 4 foot tall enclosure you have 88.9L of enclosure space. pi * r^2 * 48 = 5248 cubic inches. Divide by 1728 and you get 3.14 cubic feet. Multiply that by 28.3 and that gives you the 88.9L enclosure. The Vas that npdang listed here is 41.7L You are barely 2x the Vas of the driver.

-Robert


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## 60ndown (Feb 8, 2007)

Robert_J said:


> Even though that is not mine (it was the quickest example I could find), I consider it a complement. I'm going for 'absurd overkill'. Those are just 15's in my link. I'm building four 18's with TC9 motors and Fi recones that are tweaked by Scott to work better in an IB. If four isn't enough, I have enough parts for two more.
> 
> But you didn't achieve it. Based on your 12" diameter, 4 foot tall enclosure you have 88.9L of enclosure space. pi * r^2 * 48 = 5248 cubic inches. Divide by 1728 and you get 3.14 cubic feet. Multiply that by 28.3 and that gives you the 88.9L enclosure. The Vas that npdang listed here is 41.7L You are barely 2x the Vas of the driver.
> 
> -Robert


oh well, maybe ill cut the top off the tube and run it thru the roof


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## demon2091tb (May 30, 2005)

a$$hole said:


> Tune it low.[ 7 hz ]
> 
> Don't worry!


Unless you have alot of mechanical play or surface area i'd not advise a 7hz tune, if your watching alot of movies sure, be very careful though........cone area is always a plus in home...


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