best sealed box shape?

[psychotic]

Ok... is there any sound quality advantages to having a sealed box with the back slanted at a certain angle as opposed to having it be a perfect cube or rectangular prism??

A rectangle/cube would be easier to make, are there any downsides to this? Anything I shoudl try to avoid? I'm building a box for an 8" that is going to be about .5cu ft

 

[410Fortune]

1/2 cu ft? what kind of 8" speaker?

Sealed is better. Having one slanted wall will not effect the sound too much, especially if you seal the MDF correctly (at least paint) and you can always use insulation to fool the speaker into thinking it has more air space then it really does........

MDF is not air tight, it needs to be sealed.......give me some details on your plans, I have been a long time believer in sealed enclosures only, but I have also built several bandpass and vented style enclosures.......

 

[psychotic]

I know i'm going to make a sealed box...
My question is does the shape effect sound quality?

the 8" is an audiobahn flame woofer (aw831t), i want it to give me more mid bass.

i'm going to build 2 identical but seperate boxes for them, and audiobahn recomends .25-1 cubic foot for these. since I'm going to have a 15" cover the lower bass, I figured i'd only make the box 1/2 cubic foot so it would hit the higher frequencies better.

 

[Hokie]

yes, the shape does affect the sound quality. You want to minimize the number of parallel sides. I was going to build a triangle shape box back in highschool but got lazy. This is why Q-Form boxes are always trapezoidal and have slanted tops (that and they stuff behind seats better). The worst thing you could do is build a perfect cube. There's actually a ratio of width to lenght when building a rectangle, but I can't remember it off of the top of my head. Measure most any home audio speaker and you can figure out the ratio.

 

[410Fortune]

well the speaker size, crossover freaquency, and enclosure type will give you the mid bass that you want.

No having the rear wall slanted will not effect the sound - much. Like I said before all boxes sound different but in your case you will be fine with one wall slanted....
Of course all enclosures sound a little different from one another based on shape, but you wont have a problem..

Sounds like a good plan....two 8's will do mid bass fill nicely. .5 is a good plan

Just make sure you seal the interior of the MDF before you drop the speaker in and the most important thing is to match the amp to the sub (RMS to RMS and OHM to OHM)

Hokiebert, it depends greatly on the driver. Many speakers/subs ARE designed for a square box with all 3 walls parallel.....my Boston Competitor 2 ohm 12" is built from the factory in the exact same box I built for it. (cheaper) perfect square, 1.25 cu ft, sealed.........

from what I understand the shape of the box has alot more effect on the sounds when you are dealing with vented enclosures, where the port length and location are "tuned" to give a cerrtain low extension at a given frequency.....

 

[Hokie]

Originally posted by 410Fortune
Hokiebert, it depends greatly on the driver. Many speakers/subs ARE designed for a square box with all 3 walls parallel.....my Boston Competitor 2 ohm 12" is built from the factory in the exact same box I built for it. (cheaper) perfect square, 1.25 cu ft, sealed.........

from what I understand the shape of the box has alot more effect on the sounds when you are dealing with vented enclosures, where the port length and location are "tuned" to give a cerrtain low extension at a given frequency.....

Ummmm... Ok

If you really wanna get the down low on speakerbox building, check out The Loudspeaker Design Cookbook - Its pretty cool

 

[onelasttry]

You can change technology all you want, you can't change the base principles of sound. The "perfect" box is rectangular in shape, slightly longer than wider (15 to 25 % ) and holds correct airspace.

Creating a perfect cube can cause phase shift, though ocasionally a subwoofer will be designed to run like that. (never understood why).

 

[psychotic]

I think i have the amp and subs matched ok.

My amp i'm running them with is audiobahn's A2601T.
it puts out 420 watts x 1 channel bridged at 4 ohms.

I'll wire the speakers parallel-series (dual 4 ohm voice coils on each) for a 4 ohm load, and they handle 200 watts rms.

 

[terdrocket]

Go here -
http://www.loudspeakers101.com/

 

[psychotic]

ok, so the internal dimensions it gave me when i entered the QTS, VAS, and FS for the 8" were these...

depth 5.5"
height 15"
width 9.25"

The pieces i'd need to get these dimensions inside(using 3/4" mdf) are
2x 5.5" x 15"
2x 10.75" x 15"
2x 10.75"x7"


Picturing it in my head looks like a weird box for an 8 to be in, at least for a car. Especially 2 of them. But if its what the sound waves like, then i'll make it .
at least i don't have to make up dimensions.

 

[psychotic]

I don't know what this all means, but here are the values i'm looking at when i build this. Will it sound good?
(internal)
Depth - 5.5
height - 15
width 9.25

volume - .4416 cubic ft
qts - .44
vas - 1.5 cubic ft
fs - 36.8 hz

Qtc - .92
Fc - 77.16 hz
F3 - 63.12 hz

 

[psychotic]

any body know if this is going to sound bad before i build it...?

 

[AnabolicFrolic]

having the slanted side is bogus..
The idea behind the one angled side is to prevent standing waves from developing inside the box.
Otherwise the shape doesnt do anything acoustically.

as for standing waves.. they can only occure where the distance they travel inside the box is at least half the length of the sound wave itself.. and since soundwaves created by bass frequencies are in excess of 15ft long.. u cant create a standing wave inside the box unless its like an 8ft long box.. and i doubt you are building a box thats 8feet deep..