Subwoofer tuning and setup documents - Box Deisgn

Pillow · Post by **Pillow** » Tue Mar 09, 2010 8:01 am

Since there are always loads of subwoofer setup questions floating around I thought I would share some of the best information I have found on the topic. Hopefully this will help others model output curves that fit their needs and get away from some of the poor "manufactures suggested" installation guidelines.

Be prepared to be blown away! Some of the common "truths" will be shattered.

This is the best explanation of box dampening I have ever read, please enjoy. Short and simple. This will help when modeling drivers in WinISD and you will see the correlation between port length / box size and how it directly effects cone excursion! Clipping and over excursion are the two best way to kill a perfectly good sub-woofer.

>>>
Just because a driver is rated at 1600W does not mean it NEEDS 1600W, or that it can handle that 1600W in your application! How much power do you need? In many situations, 200-400W is plenty. Do not over-estimate what you need! You can easily get loud enough to cause permanent hearing damage with a Brahma 12 in a 1 cubic foot sealed box and 600W of power. If you value your hearing, and want to simply have a sub that sounds great, then be judicious about the amount of power you’re going to use. Use the power you will actually need, not what you think you want.

Thermally, Brahma can take a lot of power. Mechanically, it depends upon the box and application. The larger the box, the LESS power is required to reach a given SPL level. The system – box and driver – becomes more efficient. For example, a Brahma 12 in a 1 cubic foot
sealed box will reach full Xmax at 1300W at 20 Hz. In a 2 cubic foot sealed box will require around 800W to push full Xmax at 20 Hz. In 2.25 cubic foot ported and tuned to 30 Hz, 500W will reach full Xmax at 20 Hz. Choose your power based upon your application! Too much power doesn’t gain you more output, but can easily destroy your subwoofer.

Once again: a power rating is just that – a power RATING. It is NOT a requirement, or recommendation of power! You only need as much as your application requires and can safely handle; more power is the quickest way to destroying your subwoofer, and definitely constitutes
abuse. If you’re not sure how much power you need, ask around, or use a good modeling program like WinISD Pro (not the regular/original version – the Pro version is what we want!) or other accurate modeling tool that shows excursion of the driver, and look at the results. If the
excursion breaks 50-55mm peak-to-peak, you’re pushing it too far.
<<<

TS Parameters Explained:
http://www.hometheatershack.com/forums/ ... eters.html

WinISD explained:
http://www.hometheatershack.com/forums/ ... d-pro.html

Box Calculator:
http://www.hometheatershack.com/forums/ ... alculator/

Polyfill Explained:
http://web.archive.org/web/200410270512 ... fiberfill/

Enjoy!

Post by **fuzzysnuggleduck** » Tue Mar 09, 2010 9:02 am

What common "truths" were just shattered?

Pillow · Post by **Pillow** » Tue Mar 09, 2010 9:16 am

... It depends who is reading it

>The larger the box, the LESS power is required to reach a given SPL level. The system – box and driver – becomes more efficient. <

>a power rating is just that – a power RATING. It is NOT a requirement, <

Just the other day on DIYMA a person posted that a Sub RMS requirements must be met or that you will hurt the sub... This a-hole had 5500 posts as well! Hopefully one of those 5500 posts contained some accurate information. LOL

The real part of this is to play with WinISD and see the cone excursion and output curves of the various boxes. It really is eye opening once you start modeling different drivers.

Pedi · Post by **Pedi** » Tue Mar 09, 2010 10:09 am

Theese statements are based on a sealed enclosure, how about a ported box...??

Pillow · Post by **Pillow** » Tue Mar 09, 2010 10:51 am

Not at all. They apply equally for a ported or sealed box.

If anything WinISD will show the vast superiority of ported boxes. Good curves just require displacement. There is no replacement for displacement... And some polyfill voodoo.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Mar 09, 2010 11:04 am

Polyfill has always been a friend of mine, Ive never liked the sound of a box without it

Pillow · Post by **Pillow** » Tue Mar 09, 2010 11:10 am

Me too! A box sounds a bit hollow without it IMO. I usually use plain old R-13 insulation though. For me I cannot tell a difference between that and polyfill.

I have heard rumor that Dynamat (or equivalent) inside an enclosure is of benefit as well, but I have not tried it.

Stryker · Post by **Stryker** » Tue Mar 09, 2010 11:16 am

I enjoy my overkill in power, it's there if I need it. I've had loud systems for 15+yrs and my hearing is fine. thats just me.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Mar 09, 2010 11:20 am

^^^

(to your hearing being fine

)

Pillow · Post by **Pillow** » Tue Mar 09, 2010 11:28 am

Polyfill information added to the original post.

As Styker said, you can have MORE power than needed, but can be adjusted using a DMM to match your needs. Which is very well covered in another thread here.

gridracer · Post by **gridracer** » Tue Mar 09, 2010 7:40 pm

I always resin the inside of my boxes and it does make a difference in sound.

oldskoolmseriesfan · Post by **oldskoolmseriesfan** » Tue Mar 09, 2010 8:33 pm

gridracer wrote:I always resin the inside of my boxes and it does make a difference in sound.

just resin and no poly?I could see the resin at the very least, seal the box up air tight.Maybe the resin works in the way that the interior of the box is no longer pourus, there for changing the sound

NewOldStock · Post by **NewOldStock** » Tue Mar 09, 2010 8:57 pm

gridracer wrote:I always resin the inside of my boxes and it does make a difference in sound.

x2

SLICK · Post by **SLICK** » Tue Mar 09, 2010 9:05 pm

So 2 ti 10's running off a ti400.2

the 400.2 should be enough for them shouldn't it ?

- Slick

gridracer · Post by **gridracer** » Wed Mar 10, 2010 5:51 am

oldskoolmseriesfan wrote:
gridracer wrote:I always resin the inside of my boxes and it does make a difference in sound.
just resin and no poly?I could see the resin at the very least, seal the box up air tight.Maybe the resin works in the way that the interior of the box is no longer pourus, there for changing the sound

No polyfill just resin the inside completely. I use cheap $0.10 brushes and usually do 2 layers leaving brush hairs all over the place. Exactly right no longer pourus perfectly sealed. People argue that it doesn't help but those are usually people that have never tried it.

Also I was also told never use fiberglass insulation in a box instead of polyfill. something to do with fiberglass dust particles getting in the voicecoil or something I don't know if thats possible but why risk it poly is cheaper.

Post by **Bfowler** » Wed Mar 10, 2010 10:24 am

SLICK wrote:So 2 ti 10's running off a ti400.2

the 400.2 should be enough for them shouldn't it ?

- Slick

well, depends what you mean by enough? they will play music. nice music infact. but they wont reach full excursion (in a normal sized box for them)

i guess if you dont like it you can throw on another 400.2!