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Exceeding recommend box size?


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trying to build a custom box for 2 sa8's on 800 watts rms. The max size of a box I can get in the space I have is 3.2 cubic feet (not taking into account port and sub displacement) and for 2 sa8's sundown recommends .5 to .75 cubic feet. So for 2 I would need only 1.5 cubic feet. How does building the box bigger than recommended size effect performance? The box is going in a 2011 crew cab Silverado, ported, out fire. Also with this being said only having a height of 11.5 inches to work with could an sa10 work or would it be too close to the edges? Also considering the box angles downwards toward the back woukd mourning depth be an issue with the 10's?

Also how would selaed 10's in the right box compare to ported 8's? It looks like selaed isn't recomended on the sa8 or 10? Thanks

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From what I have built in the past, you need to be pretty specific with box specs in a given environment when dealing with ported enclosures. Dealing with low numbers of SA-8s in particular, you are going to have to create a labyrinth of porting in order to create a rectangular port the required length, or have an external port.

Also you have 800 watts. Those SA-8s are conservatively rated at 500 each. I would recommend going with a different woofer, and keep it as simple as possible.

Is this box going under the rear seat? I don't have a 2011 crew cab Silverado to see where I would mount some subs. I have never been able to find a great space in a quad cab.

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I had a sealed box with 12's previously and there is no where near enough volume for 12's under the seat. The box in that video was probably less than half of what 12's require. That's why I was looking to switch to 8's that out fire rather than downfire but even with 8's to out fire I need to raise the seat atleast a half inch or so unless I want the box to stick out from under the seat. As far as I've been able to find out 8's is the best option for under the seat in this truck. Anyone have any other opinions? Or designs?

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It is fairly common for people to exceed recommended enclosure size to boost output of a subwoofer. However, you do run the risk of exceeding the subs mechanical limit and causing serious damage. The more power you run to a subwoofer, the smaller the enclosure must be to keep the cone under control. Since you will be running these subs under rated power, you should be ok making the enclosure slightly larger than recommended and be fine, plus you will see a decent rise in output over the same setup in a smaller box.

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LOL. The guy in the video.

That box would be lucky to have a cube sealed per 12. And then I see a $70 bass amp mounted on the box and all questions were answered.

Back on topic for the OP. All you would need to do is adjust the height and depth a little to shrink the box. Take away an inch or two in any direction, account for wood displacement and port displacement and I would be shocked if you had 3.5 cubes of AIR to work with. 3.5 external might be true.

Also, you can TUNE a sealed box by volume also. You change the total system Q (speaker compliance vs the box compliance = response) by going smaller or larger. So a smaller sealed box would peak at a higher frequency and have a more camel back looking response then a larger box. A larger box would likely peak at a lower frequency and have a flatter response. But this is very generalized. Box design plays a huge roll in the response curve... Both sealed and ported for every kind of speaker can be modeled and optimized for a particular environment.

We also need to consider how much cone area we will have with 2 10's sealed. In the sealed box we will have about 157sq inches of cone to work with but we will only be hearing output from the front side of the cone. In the 2 8's ported we will have closer to 100Sq inches of cone to work with but that will be doubled (sort of) because we get output from the front and the back of the cone. I would decide based on your RMS power... then decide which would be better. In this case I would recommend a properly built and designed 2 8's ported.

My old YouTube channel : http://www.youtube.com/user/SwordLords1234?feature=mhee

My old build log : http://www.stevemeadedesigns.com/board/topic/161872-96-accord-b2-sundown-sky-high-dc-power-re-re-build-for-heatwave/page-37

My New Build - http://www.stevemeadedesigns.com/board/topic/207041-2016-mazda-6-sql-build/

2016 Mazda 6 Touring

JL Fix 86 - OEM signal correction

B2 prototype DSP 6to8

B2 Ref63 - 3 way active set

2 B2 Class H quattro's

1 B2 Zero.5R @.5

2 B2 HNv3 12 d2

B2 SLIP40 - Lithium in the trunk

Northstar Group 35 under the hood

100ft 2/0 welding cable

30ft 4ga welding cable

20ft 8ga welding cable

All stinger OFC speaker wire

Soundrive custom RCA's

Tons of attention to detail.... Can it be perfect?

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We are on the same page. A while back I got my ass handed to me when I stated that I tuned my sealed enclosure. lol

91 C350 Centurion conversion ( Four Door One Ton Bronco)

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We are on the same page. A while back I got my ass handed to me when I stated that I tuned my sealed enclosure. lol

Well... some people get it and some people dont. I once had someone argue with me to the point of making a $100 bet about his "Diamond" box vs a basic (but still custom modeled) box. When I pulled out a term lab, same sub, same amp, same vehicle, same tone sweep...... and showed him the results. Lets just say he never argued with me again. If i remember later Ill make a post about it in my build log with screen shots of the term lab screen.

My old YouTube channel : http://www.youtube.com/user/SwordLords1234?feature=mhee

My old build log : http://www.stevemeadedesigns.com/board/topic/161872-96-accord-b2-sundown-sky-high-dc-power-re-re-build-for-heatwave/page-37

My New Build - http://www.stevemeadedesigns.com/board/topic/207041-2016-mazda-6-sql-build/

2016 Mazda 6 Touring

JL Fix 86 - OEM signal correction

B2 prototype DSP 6to8

B2 Ref63 - 3 way active set

2 B2 Class H quattro's

1 B2 Zero.5R @.5

2 B2 HNv3 12 d2

B2 SLIP40 - Lithium in the trunk

Northstar Group 35 under the hood

100ft 2/0 welding cable

30ft 4ga welding cable

20ft 8ga welding cable

All stinger OFC speaker wire

Soundrive custom RCA's

Tons of attention to detail.... Can it be perfect?

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internal volume of the box is 3.2 cubic feet without including sub and port displacement. So I'm assuming maybe 2.5-2.75 cubes total. That's about 1 cubic foot too big according to sundown audio website. Is that way too big? I guess my question is, is there an exact number over recomended that is "too big" I have the kx800 amp that's 800rms but has a certificate stating it's been tested to 940 watts. Really appreciate all the feedback I'm getting. Thanks everyone

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