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Demon 10" Enclosure Design Advice


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Hi everyone, been on the forum for a long time but only recently got back into things. I'm a mechanical engineering student/intern at the moment and have had a passion in audio for nearly a decade now. I took it upon myself to design an enclosure for a pair of Demon 10"s for my civic hatch. I'm pretty happy with the punchiness, but the lower end is lacking pretty significantly and sounds "blown out" or "not really there" instead of "deep". I'm hoping to get some insight on where I went wrong with my design. As you can see, this is a non-traditional enclosure where the port effectively shares 4 walls with the enclosure on the outer sides. The design was done this way to maintain a specific outer dimension that fits like a glove in my hatch. Another issue I did come across was the subs not being particularly well suited to being in a ported enclosure in the first place, as the result of dividing the Fs/Qes yielded a value near 43.5. Any insight would be greatly appreciated, as I'm thinking of changing the enclosure to get better performance: I have a feeling I'm not getting as much out of these Demons as I could be.

Also, I designed this about a year ago, so I'm not sure what I did/used, but I can't seem to find a solid answer for the desired port area or volume for these subs...

sub box top down.jpg

sub section view.jpg

subwoofer excel sheet.jpg

tuning calc.jpg

masterbation is free, and even saves you money.sorry but someone had to say it

sorry, Jimmy...beat you to it (no pun intended)

LOLDON'T get a wife. Best advice I never got, and now it's too late <_<

My build: 12" DCON in a dorm room.

New/current build: 8" woofer, custom amplifier block, fiberglassed speaker pods

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So here's some feedback:

 

First thing is checking that both subs are connected correctly to the amp so the subs are not playing out of phase.

 

Second, torres can't calculate the correct port displacement for that box and you missed driver displacements, how you figured the port center line, port area is not constant.

 

Third your box just needed a single 6" round port to have the same port area and would be way easier to build.

 

Beyond that you don't mention what amp and vehicle models you use, how's your electrical, head unit, how you setup gains and everything else.

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Thanks for the reply and insight Joe, I CANT BELIEVE I didnt think of that back then! I do know that the subs are wired in phase, as they werent when I originally wired them up. Guess I'll go the aeroport route next time if I can get the length short enough to fit the box. To answer some of the other things I forgot:

 

Vehicle: 2021 honda civic hatchback

Electrical/HU: 4awg from battery to amp, 10awg from amp to subs. Factory HU, wired rear speakers to lc2i.

 

Amp: hifonics brutus 1200.1D (I know its old junk but I works and I tune it)

 

Tuning method: cheap o-scope. Used Oscope to find max HU volume without clipping, then used that HU value to tune amplifier to target voltage using 40hz test tone. I cant exactly remember how I tuned the filters, but I used a 100hz tone and 40hz tone and played with filter dials until a specific voltage was reached.

masterbation is free, and even saves you money.sorry but someone had to say it

sorry, Jimmy...beat you to it (no pun intended)

LOLDON'T get a wife. Best advice I never got, and now it's too late <_<

My build: 12" DCON in a dorm room.

New/current build: 8" woofer, custom amplifier block, fiberglassed speaker pods

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I think I'm answering my own question here, but after doing a bit more playing around with Triticum's port area calculator and some port velocity calculator, i found my port area is only one in^2 lower than minimum, but my port velocity is near 80m/s! Would that cause the extreme loss of output at lower frequencies?

masterbation is free, and even saves you money.sorry but someone had to say it

sorry, Jimmy...beat you to it (no pun intended)

LOLDON'T get a wife. Best advice I never got, and now it's too late <_<

My build: 12" DCON in a dorm room.

New/current build: 8" woofer, custom amplifier block, fiberglassed speaker pods

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Missed something, rear speakers from where you are getting signal likely are high passed, very likely not a full range signal.

 

With a tone generator and the cheap scope you can determine if the rear speakers signals are high passed or not.

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I figured out the airspeed using a couple online calcs, including this one: http://www.mh-audio.nl/Calculators/portairspeed.html

 

And you're right, rear speakers do get high passed so I wired to the front, no change in performance though.

 

also having a problem getting stuck in a design loop. A 6" aeroport would be difficult to fit in the box without making it larger, and still needs to be side mounted because 33hz requires 26.5" of port. I'm using triticums port area calculator and the torres box calc together here.

masterbation is free, and even saves you money.sorry but someone had to say it

sorry, Jimmy...beat you to it (no pun intended)

LOLDON'T get a wife. Best advice I never got, and now it's too late <_<

My build: 12" DCON in a dorm room.

New/current build: 8" woofer, custom amplifier block, fiberglassed speaker pods

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Hey @Joe XI was wondering if you could help me design a box for my 1 nsv3 12 in my 2008 Acura TL type s. So I’ve seen a lot of loud 150+ trunk builds have aero port inside box on the drivers side not really sure what to do tbh I’m currently running slot port 3ft^3 27hz

Edited by cxbritton
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On 8/6/2022 at 12:06 PM, bumpinTL364 said:

I figured out the airspeed using a couple online calcs, including this one: http://www.mh-audio.nl/Calculators/portairspeed.html

 

And you're right, rear speakers do get high passed so I wired to the front, no change in performance though.

 

also having a problem getting stuck in a design loop. A 6" aeroport would be difficult to fit in the box without making it larger, and still needs to be side mounted because 33hz requires 26.5" of port. I'm using triticums port area calculator and the torres box calc together here.

 

To be honest it's still not clear what your problem is, I am pretty sure the front speakers are high passed too, they usually are, other things that can kill your low end  and/or overall output are:

 

Subsonic filter set too high.

 

Bad box placement, you can try to move around the box and change sub aimings and see what it does.

 

you can phase invert both of your subs, it can be a big deal in some installs.

 

If your factory stereo is not a good full range source you can test connect dirctly to your amps a different source, bypassing completely the factory head unit.

 

 

Edited by Joe X
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