Increasing box airspace
Printed From: the12volt.com
Forum Name: Car Audio
Forum Discription: Car Stereos, Amplifiers, Crossovers, Processors, Speakers, Subwoofers, etc.
URL: https://www.the12volt.com/installbay/forum_posts.asp?tid=30424
Printed Date: July 06, 2025 at 11:50 PM
Topic: Increasing box airspace
Posted By: fuseblower
Subject: Increasing box airspace
Date Posted: April 15, 2004 at 12:39 PM
I am trying to increase my airspace in my box but want to keep the same box dimensions. I was thinking about using 5/8 mdf instead of 3/4 mdf. The box will be very small do to space limitations. The size of the box will be about : Front - top to bottom 11" Left to right 15", the back will be about 4 inches high with the same width. The dept will be about 12 inches. The angle of the front will be about 62 degrees. Will using a thinner mdf help to increase air space with out weaking the integrity of the box.
Replies:
Posted By: thapimpfromchi
Date Posted: April 15, 2004 at 1:05 PM
How about stuffing the box? Technically it doesnt increase airspace, but it fools the woofer into thinking its in a larger enclosure. Using thinner wood is only gonna cause problems, especially if you are using a quality woofer. ------------- 1990 Honda Civic HB:
Clarion DXZ545MP H.U.
2- 6.5" Power Acoustik interiors
Diamond Audio 600.1 amp
Diamond Audio 15" M6MKII
Pyramid PB881X 4 CH. Amp
Posted By: DYohn
Date Posted: April 15, 2004 at 1:09 PM
Thinner MDF will increase the interior airspace AND will result in a weaker enclosure that is more prone to flexing. To combat this, you'll have to add more braces, which will defeat the purpose by eating up interior voulme... unless you add the braces on the outside. As thapimpfromchi recomends, stuffing the enclosure with polyfill can increase the effective airspace by as much as 25% (although 10% is more realistic.) The only thing you will lose by using too small an enclosure are some of the lowest bass frequencies. Build your "box" and see how it sounds. Add about 1lb of polyfill per cuft and see if it helps. ------------- Support the12volt.com
Posted By: forbidden
Date Posted: April 15, 2004 at 1:50 PM
Here is another trick to help strengthen a box and it does not eat up much space. Run a threaded rod through the box from one side to the other, secure eachen with a large washer and a nylok nut, tighten as necessary. The only downfall is that you now have a threaded rod and nut to disguise on one or two of the sides.
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Top Secret, I can tell you but then my wife will kill me.
Posted By: DYohn
Date Posted: April 15, 2004 at 2:12 PM
Wow, that is grat idea! A new trick for my bag... Thanks! ------------- Support the12volt.com
Posted By: fuseblower
Date Posted: April 15, 2004 at 5:29 PM
I like the rod idea but because the airspace is so limited and with the speakers depth the rod might not work. I currently have about a half pound of poly fill in each side of the box. The box is so small that is about all of the polyfill that I could fit in the box with out getting in the way of the sub. I am trying to squeeze the box under the rear seat of a '99 dodge quad cab truck. Current measurements give me about .06 cu ft of airspace. My subs recommend .08 I don't think that I am getting close to this even with the polyfill. I heard the exact subs in a box that meet the specs and they sounded much deeper.
Posted By: thapimpfromchi
Date Posted: April 16, 2004 at 12:30 AM
well, i dont know if you are up for it, but you can also invert them. the difference from not having the cone in the box, might have you meet your requirements. I dont know if you want the woofers stickin out though, but, it was just a suggestion.
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1990 Honda Civic HB:
Clarion DXZ545MP H.U.
2- 6.5" Power Acoustik interiors
Diamond Audio 600.1 amp
Diamond Audio 15" M6MKII
Pyramid PB881X 4 CH. Amp
Posted By: fuseblower
Date Posted: April 16, 2004 at 7:45 AM
thapimp, thought about that but I have to try to keep my speakers as concealed as possible. I have to try to keep the kid proof. I was thinking about raising my seat for the extra space but it might make the seat a little unsafe.
Posted By: DYohn
Date Posted: April 16, 2004 at 8:31 AM
If you sub requires .8cuft and your enclosure will be .6, add one pound of polyfill and the effective enclosure size will be closer to .75. Also, if you have the money and some enclosure building skills, you could build an isobaric loaded system. This uses two matched woofers mounted in a "push-pull" configuration, and it requires the enclosure to be exactly 1/2 the size necessary for one speaker. If you're interested in looking at this option, check out www.diysubwoofers.org ------------- Support the12volt.com
Posted By: thapimpfromchi
Date Posted: April 16, 2004 at 10:41 AM
Hey DY, just a quick question for you. Earlier in the thread you said " polyfill can increase the effective airspace by as much as 25% (although 10% is more realistic.)" I read elsewhere that using polyfill you could increase airspace in an enclosure up to 40%. So, if I had a 1 cu ft box, i could stuff it, so the sub would think its 1.4 cu ft. Is this true? I forgot what site i saw this on, but if i find the url ill send it to you.
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1990 Honda Civic HB:
Clarion DXZ545MP H.U.
2- 6.5" Power Acoustik interiors
Diamond Audio 600.1 amp
Diamond Audio 15" M6MKII
Pyramid PB881X 4 CH. Amp
Posted By: DYohn
Date Posted: April 16, 2004 at 11:05 AM
I think 40% is way overstated, although it is possible depending on the type of material used. Standard spun poly-fiber or dacron fiber fillers will result in about 10% effective increase with one pound per cubic foot. But different materials will result in different values. ------------- Support the12volt.com
Posted By: thapimpfromchi
Date Posted: April 16, 2004 at 11:07 AM
good enough, I just wanted your input on that. Thanks.
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1990 Honda Civic HB:
Clarion DXZ545MP H.U.
2- 6.5" Power Acoustik interiors
Diamond Audio 600.1 amp
Diamond Audio 15" M6MKII
Pyramid PB881X 4 CH. Amp
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