Subwoofer box's useable internal air volume

[Zeee]

To all the experts & bros here,

 

Example #1: A subwoofer manufacturer stipulates that for a sealed enclosure, the typical enclosure volume is 1 cubic-ft in order for the woofer to deliver its optimum performance.

 

Question #1: Does the above means the sealed enclosure of 1 cubic-ft is the net useable internal air volume?

 

Question #2: Does the above means the sealed enclosure of 1 cubic-ft is the net useable internal air volume excluding the physical volume of the subwoofer after assembled in the sealed enclosure?

 

 

 

Example #2: The specs of a 12-in subwoofer is as follows

 

[Apollo]

y u wanna build own box and not just pay the installer to do everything for u? not too exp afaik.

 

if i not wrong ard $150 niah niah for a non ported box.

[Zeee]

Hi! Just want to verify a few installers' feedback, and also to understand a liitle on woofer enclosure building.

 

Thanks for sharing on the cost of a normal box. Any idea how much would it cost if it is custom fabricated (e.g. a fiberglass enclosure) in a corner of a car boot?

[Ivan0507]

All this are for your info only,normally ,manufacturer will tell you the minimum volume & a maximum volume for a particular subwoofer.

(eg,1.0 cuft to 2.0 cuft )

actually,this is a acceptable air volume for this subwoofer .different sub come with different spec.the optimum is should be in between 1.0 to 2.0 cuft .and this doesn't include the sub displacement.if you want to make a box at 1.5cuft ,you have to build the box bigger(depend on the sub displacement) .after putting your sub to the box that will give you 1.5cuft internal air volume .

 

even you can build a box bigger than 2.0cuft ,it still work.

 

 

 

different wood ,different thickness will affect you subwoofer performance.

a acceptable wood thickness is 3/4"(19mm).if you used thinner wood ,let's said 1/2"thick ,you will lose out the punch /output of your sub.

 

also the back or rear wall of the box ,

if is a slope ,you will feel that the bass is a bit high up ,above your eye level ,when the bass coming from the rear boot.

 

if is a square box ,you will feel that the bass from the rear boot is hitting towards the driver seat,just behind your back, below your eye level .

[Zeee]

Thank you for your feedback and info sharing. Very much appreciated.

 

Very interesting feedback on the rear wall of the subwoofer. Looks like my box will have a slope wall against the rear seats.

[Ivan0507]

ya.enjoy listening

[Kb27]

I build my own sub box using birch shelves from Ikea.

There are many designs on the web. I just choose a simple sealed box and the result is a great sounding sub.

The volume is based on internally available air space...but a sealed box is tolerant to some errors.

[Zeee]

untreated birch wood from ikea? could you share a picture of the box? what color of lacquer did you use? hope you did not wrap the box in carpet...

[Kb27]

Was lazy to treat the wood. Still in its raw state from ikea.

 

[Zeee]

wow! thanks for sharing.

[Friedpiggy]

All this are for your info only,normally ,manufacturer will tell you the minimum volume & a maximum volume for a particular subwoofer.

(eg,1.0 cuft to 2.0 cuft )

actually,this is a acceptable air volume for this subwoofer .different sub come with different spec.the optimum is should be in between 1.0 to 2.0 cuft .and this doesn't include the sub displacement.if you want to make a box at 1.5cuft ,you have to build the box bigger(depend on the sub displacement) .after putting your sub to the box that will give you 1.5cuft internal air volume .

 

even you can build a box bigger than 2.0cuft ,it still work.

 

 

 

different wood ,different thickness will affect you subwoofer performance.

a acceptable wood thickness is 3/4"(19mm).if you used thinner wood ,let's said 1/2"thick ,you will lose out the punch /output of your sub.

 

also the back or rear wall of the box ,

if is a slope ,you will feel that the bass is a bit high up ,above your eye level ,when the bass coming from the rear boot.

 

if is a square box ,you will feel that the bass from the rear boot is hitting towards the driver seat,just behind your back, below your eye level .

 

Hiya, seems like you have experience with alot of boxes. I've got some questions need your advice.

 

How about if the back of the box is irregular shape? ie: fg box. I'm thinking of putting one at the relatively un-used portion of the trunk where there is a dip in on both the left & right sides so that i can keep more space available in the trunk. Probably i'll choose the left side with the woofer anyhow aimed(necessary? since we cant sense direction for below 100hz) towards right front seat for more output. I've seen alot of people do it there to save space but wonder how would it sound like.

 

Also thinking of maybe trying the inverted setup with the magnet on the outside. How would this sound as opposed to the conventional magnet inside assumming having same airspace?

 

Another question is should the box need to be firmly secured to the chassis? I only intend to just use velcro's to keep it in position.

[Ivan0507]

my experience ,the box is irregular shape will also affect you sub bass.also when placing yr sub ,the sub cone facing up ,the bass will reduced.not really much experience on fg box.was heard a few set up customised fg before ,in malaysia -friends' set up. fg box more towards SQ setup.found that the bass not really good if you want solid /punch bass.unless you made half fg half mdf (front fg with rear wall mdf board)output more great.

 

if you want to make a fg box.you should make it thicker,actually ,one mat is 1mm .so have to apply one layer by layer.

is better to secured to the chassis ,by using a screw and nut ,make a hole behind the fg box ,and use the screw to hold it .this's the best why to do it.velcro is not a good solution.the box still will fly.

[Ivan0507]

you using birch shelves for your sub box.is your sub bass respond slower?.was heard one of the set up (friends'set up )using this wood in meleka malaysia.found that the sub bass really slower down . he was using home audio speakers -kef in kickpanel in the doors,and full MIT INTERCONNECT ,with custom made ported box.the port using pvc pipe ,the port noise ,he really tune untill minimum.was surprise with his box.

[Kb27]

If you mean phase shift, slowing down in bass as compared with higher frequencies....no, I don't experience it with this box.

 

It's a sealed box and is more tolerant to errors and phase shift.

 

When you build a ported box, then you have to be careful with the calculation and dimension...due to sound reflection and reverberation.

[Kianbeng]

If you mean phase shift, slowing down in bass as compared with higher frequencies....no, I don't experience it with this box.

 

It's a sealed box and is more tolerant to errors and phase shift.

 

When you build a ported box, then you have to be careful with the calculation and dimension...due to sound reflection and reverberation.

 

Actually I want to also build a sealed box - small one so that I can fit my 8" under my passenger seat. Just like an active subwoofer. But I am worried if the internal volume is too little ie <1cubic ft then it may damage the speaker itself. So now thinking of making it ported so that air pressure will be a bit flexible but then when I saw your statement regarding being careful with calculation of the dimension I got worried hehee..

 

Maybe just drill some holes instead of a standard port hole?

[Kb27]

Actually I want to also build a sealed box - small one so that I can fit my 8" under my passenger seat. Just like an active subwoofer. But I am worried if the internal volume is too little ie <1cubic ft then it may damage the speaker itself. So now thinking of making it ported so that air pressure will be a bit flexible but then when I saw your statement regarding being careful with calculation of the dimension I got worried hehee..

 

Maybe just drill some holes instead of a standard port hole?

Never heard any speaker damage due to seal enclosure. Maybe it might heat up a little if you rammed the speaker hard. But I wouldn't worry too much.

 

You could try with some holes, but you probably need to experiment a bit.

 

At one time, I removed the sub and put it inside the door panel, to save space. It sounded terrible and I put it back in the enclosure.

 

Ported speaker is hard to control. My home one is like sometimes resonating at low frequency very loud like runaway volume control.

[Kianbeng]

Ok. Thanks.

 

But what about if the box is not really cube? coz below the passenger seat, due to height constraint, I can only make a flat square box...and maybe a big longish extending forward. So it will be a uncommon shape.

 

Actually the design will be opposite of a tube. coz the tube will have alot of space behind the woofer. But my box will have no space behind the woofer but more space on it's side.

 

Will this also be a problem?

[Kb27]

This is an excellent but technical site.

http://www.bcae1.com/speaker.htm

 

What I know is that subwoofer put in a sealed enclosure has a certain optimum internal volume.

It doesn't matter what shape it is as long as the volume is correct.

 

I also checked with the manufacturer what is their recommendation and then find an average value.

 

I have a MM2084, 8" sub, so I used the recommended 0.35 cu ft.

http://www.polkaudio.com/caraudio/subbox/