CRAZY insane Subwoofer Box Idea (w/ Pictures) - Page 2 - GM Forum - Buick, Cadillac, Chev, Olds, GMC & Pontiac chat


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View Poll Results: What do you think?
LOVE IT! BUILD IT! 1 4.55%
Interesting approach i'd like to see the outcome... 13 59.09%
Um not a chance, you're wasting your money. 6 27.27%
Holy crap Cleatus I just seen my first UFO!!! 2 9.09%
Voters: 22. You may not vote on this poll

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Old 03-19-2007, 02:56 AM   #11
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I am curious as to your plan to hold the cross tube to both of the boxes. Its not a subject I have researched in depth, although it does interest me.
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Old 03-19-2007, 01:27 PM   #12
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You don't specify....what size tube are you going to use? I think the tube will be the downfall of this design. Not for the fact that it'* incorrectly sized, but for the fact that fixed length and diameter of the tube will "tune" the back wave to a certain frequency and the setup will be boomy at that frequency, and thin across the rest of the spectrum. Or that'* what I'd expect it to do.

Have you considered slot loading the 12'*? That'* where the 2 12'* face each other and a small slot provides the output into the vehicle.

Or if you want an esoteric loading, go the route of a "tuba"....the auto tuba found here. http://www.billfitzmaurice.com/autotuba.html I'm a real fan of horn loading. I have a pair of Focal 38 VX'* installed in an old set of Altec VOC cabinets. Outside in an open parking lot from 50 feet away people thought the bass was too loud. Ah, I love them horns.

Dan McCann
2000 SSEi
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Old 03-19-2007, 05:42 PM   #13
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Quote:
Originally Posted by bmsgaffer86
According to WinISP (or whatever that subwoofer design software is) i calculated that that would give me more VOLUME but less accuracy. It would distort about a 50Hz section in the middle of the band to be too loud. Where as the Isobaric makes a more accurate curve and reproduces bass 10-15Hz lower than a standard 2 driver system putting my -3db point at closer to 25 Hz than 40Hz.

Why is the box too big for an isobaric design is it a factor of the drivers im using?

Are you going for SPL or quality most of your recommendations seemed like they were based on volume?

Sorry for all the questions Im just trying to learn and I am going at this with an open mind.

Thanks!
Ok, my first post was basically speculation. However, after doing a bit more analysis my opinion doesn't change much. Your isobaric sealed box isn't as oversized as I speculated. However, here are a few plots to back up my statements.


The pink line is your design, the yellow line is 2 sealed subs sharing 3cu.ft., and the green line is an isobaric ported enclosure in rougly 2.2cu.ft tuned to 30Hz. Your design has a decent, gradual rolloff and would sound decent. Personally though, the ported design'* rolloff is about the same down to rougly 27Hz (also smooth response). Looking at the -3dB points, both the isobaric sealed and standard sealed boxes cutoff about the same point (~58Hz isobaric, ~60Hz standard sealed box). The ported on the other hand hits the -3dB around 40Hz. This would likely give smoother performance in a car due to the stronger lowend.



As far as feeding the sub power, the isobaric systems are simply less efficient. All are shown eating 200w. If your front speakers are too powerful, an isobaric setup likely won't keep up and leave you wanting more.

All in all, you design is worth a shot. But, I'd personally consider going ported. Also, the tube between may become your Achilles heel for the structural integrity of the box.
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Old 03-19-2007, 10:57 PM   #14
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That looks like an interesting design. Did you compensate for the volume of the connecting tube ad the driver displacement? Ide say give it a try, but where is the tube going? To avoid resonances from the tube you should make the tube cross sectional area as big as possible. Also if you use fiberglass fill inside the box you can get away with a smaller volume. IF you reverse one of the subs, you will get a cleaner sound because the mechanical distortions will cancel out. Keep in mind that the response of the system will get changed completely when you put it into your car, so if the response looks perfectly flat on the graph, it could have a huge hump or dip when you try it in the car. You would probably do fine with one sealed sub in each side of the trunk. Let us know how it turns out!
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Old 03-20-2007, 04:11 AM   #15
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Quote:
Originally Posted by sandness
Quote:
Originally Posted by bmsgaffer86
According to WinISP (or whatever that subwoofer design software is) i calculated that that would give me more VOLUME but less accuracy. It would distort about a 50Hz section in the middle of the band to be too loud. Where as the Isobaric makes a more accurate curve and reproduces bass 10-15Hz lower than a standard 2 driver system putting my -3db point at closer to 25 Hz than 40Hz.

Why is the box too big for an isobaric design is it a factor of the drivers im using?

Are you going for SPL or quality most of your recommendations seemed like they were based on volume?

Sorry for all the questions Im just trying to learn and I am going at this with an open mind.

Thanks!
Ok, my first post was basically speculation. However, after doing a bit more analysis my opinion doesn't change much. Your isobaric sealed box isn't as oversized as I speculated. However, here are a few plots to back up my statements.
[edit out big picture in quote[/img][/URL]

The pink line is your design, the yellow line is 2 sealed subs sharing 3cu.ft., and the green line is an isobaric ported enclosure in rougly 2.2cu.ft tuned to 30Hz. Your design has a decent, gradual rolloff and would sound decent. Personally though, the ported design'* rolloff is about the same down to rougly 27Hz (also smooth response). Looking at the -3dB points, both the isobaric sealed and standard sealed boxes cutoff about the same point (~58Hz isobaric, ~60Hz standard sealed box). The ported on the other hand hits the -3dB around 40Hz. This would likely give smoother performance in a car due to the stronger lowend.

[edit out big picture in quote[/img]

As far as feeding the sub power, the isobaric systems are simply less efficient. All are shown eating 200w. If your front speakers are too powerful, an isobaric setup likely won't keep up and leave you wanting more.

All in all, you design is worth a shot. But, I'd personally consider going ported. Also, the tube between may become your Achilles heel for the structural integrity of the box.
I really like that ported design. But i could only reach 2.6 cu.ft. with that tube and other box. My goal was to fit the whole design completely in those little holes and if i make one box 2.2 cu-ft it will be too big to fit there. Do you think that porting this design would even come close to working? Ill try the sealed version first, and if it doesnt completely wack-out ill give that porting idea a try. Do you have any specs on the ports?

That tube is 4" I.D. schedule 40 PVC pipe. I agree with you, that the PVC connection will be the hardest to keep together (and probably do some nasty resonance thing). I have an idea in my mind that involves adapters pressing on the wood from both sides with a rubber seal to absorb some of the vibration energy in the joint while still keeping it completely air-tight.

phoenix - i read that if you point them together you loose ALL midbass, so i decided to do the parallel scheme cause my car needs all the midbass i can get I did acount for the tube, but cannot account for any weird resonances it has. That is another reason for the angled backs, to keep really long standing waves from forming through that tube. Im hoping the resonant frequency of the tube is so low from teh length and diameter that it will not be in play, but who knows
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Old 03-20-2007, 04:42 AM   #16
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The TS-W300R has different specs so i updated the same graphs and here they are. Yellow is my design, Green is isobaric ported, blue is two sealed in 3cu ft box.

GAIN:
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SPL:
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and this one seemed interesting, looks like ported designs have all sorts of delay in the lower frequencies. Not that its unacceptable range, just interesting.
GROUP DELAY:
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Old 03-20-2007, 03:23 PM   #17
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Hooking up one sub backwards has nothing to do with midbass, just make sure that you switch the speaker polarity of one of the subs. That way the subs both move in the same direction at the same time (In phase). Ported designs can have up to a 180 degree phase shift (or latency), thats not a problem, but designs such as a bandpass can have up to 450 degrees of shift, which means the bass is hitting late by more that one whole wave. Thats quite a bit. Sealed has the least shift and therefore should be the most 'in-time' with the rest of the speaker system. Its not critical though, just interesting to know. A sealed design would benefit more from an isobaric alignment than a ported one would. Of course anything will work if you build it right. Use a lot of bracing in your box. One millimeter of box vibration is like 20 watts of real power lost.

Another tip : since your using a box design program, there should be a 'QTS' value. You are going for SQ so you should try to keep the box/sub combo around .707 . Its a number that describes the shape of the frequency response chart. See if your program has this spec. It can be helpful when designing sealed boxes. If this is a little ahead of you dont worry, its not super important, i just havent used that program before so I dont know how much it gives you.
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Old 03-23-2007, 03:12 AM   #18
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Heres the wood im using. Its not MDF, sorry all you diehard MDF fans. Its not as dense but its as stiff, if not stiffer. I NEEEEDed the weight savings and i made my last box out of the same stuff and it worked great. I save approx 50lbs using this wood over MDF.

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And heres where im at laying out the stuff in my trunk. Paper is actual dimentions of the box, just at 14 inches to the height.

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Old 03-23-2007, 04:22 PM   #19
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I'd like to see this work out, I've never seen anything like this before.
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Old 03-28-2007, 12:29 AM   #20
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I have kinda but my subs were in two boxes and didn't have pipe in the middle was in my ga
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how deep is the sub you plan on putting in front? because by your diagram it doesn't look like you have that much room my boxes held one sub each and the magnet was only a couple inches away from the back of the box?
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