I got a new sub for Xmas, and I'm going to build a custom box for it. However, I'm curious what size box I need. So, anybody running these, could you tell me what size box I need for this subwoofer?
Some info:
-will be going in a Subaru Forester(wagon environment)
-the box will be a sealed eclosure
-the sub will run off a Cadence Z1000 amp running at 2 ohms for 300 watts RMS
-the sub location will be right behind the rear seat(shaped to conform up against the rear seat) and will fire straight back
I know common box sizes are in the area of 1 to 1.5 cubic feet. I personally like a flat response and would tune the box to provide a flat respose. However, I know the car will provide its own gains and losses with make such tuning hard.
The sub's sole purpose is for accenting the front speakers. I'm not looking for loud or boomy.
Is there any worries about box shape or particular dimentions? I plan to build it as thin as possible(just a hair deeper than the sub) and then gain the volume through width and height(up to 2/3 fold-down seat dimentions). The box would fold down with the seat if desired or removed or moved if needed(thinking about lots of velcro).
What about things like fiberfill? As far as I'm aware, this is supost to help with standing waves and such. Am I worried about such things at lower frequencies? When would I be concerned with such things? Is fiberfull always benificial? I've heard this makes sub sub seem like it's in a bigger box. How is this? Whould I have to tune the box differently because of this effect? Or is this just nonsense?
Since I'm placing the sub into the box volume, do I have to compensate for the volume the sub takes up? Or do people not worry about this?
Sorry about all the questions. This is my first sub and will be my first box.
To get a flatter response, you could increase the size of the enclosure but the overall response wouldn't be perfectly flat. To build a system that had a perfectly flat frequency response (generally desired by audiophiles), you'll have to take the vehicle's transfer function into account (this will be discussed later). When a manufacturer recommends a particular enclosure, you should ask yourself (or, better yet, the manufacturer) what the enclosure is optimized for.
I'm kind of learning about it myself, but from what I've read you are supposed to take measurements of the sub in any kind of enclosure in an open field or open area using a set of test tones.
Then take the same sub and enclosure and play those same test tones in your car and measure the difference.
Then when you have these two different measurements you can use them in a program to determine what enclosure to use to get a flatter response.
I wish I knew more about it, but I'm still learning about transfer function and modeling different enclosures out. Maybe someone knows more about this than me.
Last edited by cam2Xrunner; 12-25-2005 at 12:42 PM..
Hmm, from the sub's data on TC Sounds' site and from the calculations from the link, it says that I need a 2.4 ft^3 box to get a flat response(Qtc of .707). The 1 ft^3 gives a Qtc of around .9, at least with that calculator.
I had a look with WinISD too, again 2.4 ft^3.
However, it seems I can go down to the .9-1.1 ft^3 box size without a hugh impact on the curve. Down at .9 ft^3 I only get a small dB gain starting at 50Hz with a gentile slope and a peak of +1dB around 72Hz. Below 50Hz, it just drops off similar to normal except the -3dB range is a few Hz higher, 39Hz instead of 36Hz.
It seems I have a bit of a range to work with without creating a detrimital effect on the sound. Running down around the 1 ft^3 range, it should be pretty easy to build a box.
I'd just use about 1cft sealed and eq the response.
You can go by ear, or try to measure it. Keep in mind the rear firing position as well as the seats etc. will dramatically effect the upper end response, whereas boundary/cabin loading gain will affect the bottom end. By the time you're done you'll realize the box made very little difference in the big scheme of things.
If possible, 1 or 2 band parametric eq can make a world of difference as well as proper level matching and xover flexibility.
A speaker is only as good as the room you put it in.
My HU can run down to 20Hz with the parametric, so I can do some adjustment as needed if I want. I can't quite devote 2 bands to it though, only got three to work with, and the second band can only run down to, 80Hz or 100Hz I think.
Yeah, car environment will have a big effect. I'm aware of that. Still, the initial characteristics of the box will determine my starting point as well as some limitations. I can't just throw it in whatever I want.
I'll have to get out my tape measure and get a good idea of the size constraints for how I want to place it. With 1 ft^3, I should have an easy time. However, I may just run it as big as I can within the physical liimitations that I want to set, be it 1.2 or 1.4 ft^3 in the end. I guess I could always fill in the box if I want to do some additional tuning, start out big and knock down the volume with a filler(wood blocks). That way I can both do a physical tune and an EQ tune.
As long as you're between a qtc of .5 and 1, generally you're fine. I always shoot for around .9ish, as in my experience that yields the flattest unequalized low end response for my car (midsize sedan). But afaik, if you don't have experience tuning a sub in your car or measurements of the vehicle's transfer function it's nothing more than guesswork to choose a box alignment.
A speaker is only as good as the room you put it in.
What box size? - TC Sounds TC2+ 12" DVC
Linear Mode
