At 4800 watts max, your scratching 124dB, but your cone excursion rate is off the limits, can you imagine a ripped cone? Plus Matt90max, brought out an interesting point earlier. The thermal rating of those coils is not even near 750 watts rms. Another 12" Brahma might get you closer, around 126dB, that's with 4800 watts of amp power. Double the amp power and you are at 127dB. Maybe you should try this in another vehicle.

 

Those numbers are based on listening from the driver's seat the box is virtually located in the trunk 180 degrees (firing towards the back of the trunk). I plugged the distance from the driver seat to the trunk which is around 7 ft. (ran a tape measure from trunk end thru the armrest opening and to the driver's seat) in the program. There are other factors to consider, like you mentioned. Take also into consideration in-cabin gains, free power! I wish I have the program where it factors in a specific vehicle's internal acoustics.

 

something doesn't seem right...

4800 watts going into two brahma 12s only puts out 126 dB? i figured it'll be a hell of a lot louder than that, though the enclosure plays a huge role in how a speaker performs.

 

That's what I was thinking. I let the program figure out optimal enclosure size, it came up with 3.6 cu.ft. tuned at 28hz. That's what those numbers were based on. However, I just did something different. I plugged in 4.8 cu.ft. (exactly double the size of your new box) and voila!!!! 129.5dB @ the tuning frequency with 9600 watts of power. Cone over-excursion is eminent at 50hz and below. Your gonna need some pretty expensive amps to do this!!! Another thing to consider is the trunk's interior, something to do with wavelengths, I recalled something like that from a discussion awhile back! This is why I mentioned earlier that perhaps this is more appropriate for larger vehicles.

 

Fosgate Fan, here are some graphs for you....enjoy!

SPL graph:
http://img88.exs.cx/img88/8996/brahma-spl.jpg

Cone excursion (red line across top is the sub's XMAX):
http://img88.exs.cx/img88/7347/brahma-exc.jpg

Transfer function magnitude graph:
http://img88.exs.cx/img88/2/brahma-mag.jpg

BTW, there are two 12" Brahmas in the design.

 

cabin gain, etc.

 

to give you a idea of how much you db will change are a few systems i have had and how much its changed.

dd audio 9515 4 cubes, 45sq port 35 hz
150.7 with autotek 1500 watts no battery 4 guage



2 kove armeggedon 2.25 each box 25 sq each box 34 hz
140.6 with concept 2400a around 1900 watts, and battery with 0 guage


both played with a sweep. starting at tuning to 10-22hz above tuning for 10 seconds. the new mic was suction cuped to the glass in the passenger side windshield. and the mic reading the 9515 was held in the middle of the glass in the corner where the glass meets the dashboard.

 

matt90max,

It's interesting how one DD Audio was louder than 2 Kove Armaggedons. Perhaps its got something to do with wavelength deficiency in car trunks. Big subwoofers are wavelength hungry! Perhaps the two subs ended up cancelling each other out thus producing lesser dB.

 

Found this animated gif by accident while looking for the DD9515 t/s par...thought I'd share it! Its a pain to try and find their spec.



Check out this guy's setup: http://www.sounddomain.com/id/ddisloud

 

matt90max,

Just ran your DD9515 setup thru the software and I got 128.7dB @ 38hz. That means your in-cab gain was 22dB!!! That's a 3rd gen maxima right? Maybe the 4th gen isn't much different in cabin gain.

This can mean that Fosgate Fan's new box (2.4 cu.ft. tuned at 28hz) with one 12" Brahma can potentially produce 135.6dB @ 30hz once inside his Maxima trunk! And that's with a 480 watts of amp power. Feed that same setup with 1500 watts and you'll be looking at 140.6 dB.

 

that DD is a sick sub

 

I just updated my last post......you might wanna read it again.

 

my ears will hate me for that

btw matt90max, do you have any excursion vids?

 

OOOOPS, made a mistake on calculation. its not 128.7dB.............its 123.7dB. Now we're looking at 26.3dB cabin gain based on matt90max's numbers. For Fosgate Fan, that means more gains.

 

i doubt i will see that much of a gain. looks like he completely removed the rear deck and just covered the opening with that wire mesh. mine is still intact.

 

True that!!! However, just going by the general rule of 12dB cabin gain, your at 125.6dB with one 12" Brahma. To me that's loud enough. BTW, is your sub box MDF?

 

the one i have now is made out of MDF. when i bought the sub off this guy, he gave me the box as well...and it isn't the best constructed box out there

but it'll do for now, i just had to reseal the edges with some silicon.

 

I seen other use some type of really hard wood but I'm after for a lighter sub box eventhough I'm only using one 10" sub. What other material is comparable to MDF? BTW, when are you getting the vented box made?

 

baltic birch is what your after. im gonna make my new box for my shivas out of this... but ive been saying this for months now. finals suck.

 

baltic birch is what your after. im gonna make my new box for my shivas out of this... but ive been saying this for months now. finals suck.

 

no kidding, i got finals in the next 2 weeks

 

Where do you get them and are they expensive stuff?

 

it is considerably more expensive. maxima dan knows alot more than me. he actually built a box out of it for his brahmas. pm him.

 

Thanks....maybe he can build me the box. I'll just give him all the measurements and stuff.

 

2DaMax,

Sorry if I've missed something...I didn't have time to looke through all 3 pages of posts.

I saw that you already answered one of your questions. You were under the assumption that the low bass you heard might have been in the 25Hz range...and then you realized that is was much higher than that. Good realization.

Kudos on all the reasearch you did, with all the graphs and #s.

I don't know exactly what you're looking for, but remember than a ported box is tuned to a certain frequency. This box will play that frequency louder than the others. A sealed box will not be as loud in that particular frequency, but it will give you better power handling through damping (the air in the box will act to damp the cone's motion) and it will give you better low-end frequency response. In general, the sealed box will give you a flatter fequency response. Some people like this, others don't. A SQ purist will take the sealed box any day because it produces the sound more "naturally" without the equalization the port provides. Someone that listens to rap might be happier with their ported box because it can be tuned to give you a good 45Hz pounding that rap music is known for.

I would also like to point out that I have NEVER used a subsonic filter and I've never had any problems.

Also, I guarantee you that I can hear down to 20Hz quite well, so the RF guy was a little too quick to say that 30Hz is the threshold. Also, you need to understand that 10Hz can be FELT...if not heard (even though most music material will never play that low).

If you're looking for a small box with DEEP bass and a very flat frequency response, I suggest you look into an aperiodic box. It's the best of both worlds in that the box is VERY small yet the low bass extension is near perfect. The only tradeoff is a loss in volume. You would never win a SPL contest with an aperiodic box, but you could certainly hold your own in the SQ arena. Check them out!!

Tony

 

well i would agree that with most subs 30hz or a little above is the threshhold. even tho people say our ears can hear down to 20hz. anything below around 30hz will be heard not as a tone. you will hear the sub moving things in the car and you will think its bass when its really just the resonnece of loose things in your car moving or just the sound of moving air. our ears are not good enough to acuratly pickup a tone below 30hz.

 

I've heard of aperiodic boxes before but I'm not sure exactly what it is. Is it vented?

 

Immediately after I posted the question, I got on my favorite search engine and began searching for a good source for AP design. EliteCarAudio.com featured a really good article on this box design. Reading thru the article, I found a few things which are required in order to accomplish good results from this box design, certain subwoofer physical factors: ie QTS and voice coil. On my particular subwoofer, its QTS is within the recommended spec. However, being that mine is a DVC doesn't make this sub quiet the perfect candidate, AP design prefers SVC. Also, you'd need to make sure that the trunk is TOTALLY sealed from the cabin of the vehicle, like you would with a free air setup. In a sedan, like our Maximas, you need to create a baffle that will totally seal the trunk from the cabin. You would also need to seal the rear deck, and hunt down every little airpassages to make the trunk airtight. This requires a lot of work in my opinion, probably too much work for me for the outcome in decreased output in the bottom octaves. For people with a quality outboard EQ, this might not be a problem as boosting the deficient frequencies can correct them. But for me, I am relying in the h/u's built-in 3 band parametric EQ which probably won't do a good of a job as an outboard one. I'd see this design more suitable for smaller cars, like a roadster or a convertible with very limited trunk space.

Thanks for the input Tony.

 

Hey, no problem! Yes, the elitecaraudio was one of my sources of information when I designed and built my box.

If you want pictures of my 5th gen with my AP box (yes, the trunk is sealed off from the cabin) then check out THIS page. It was a ton of work and required lots of patience and attention to detail, but is was DEFINITELY worth it. The subs have such amazing articulation and detail and literally sound as if they're mounted in my front doors, not at all behind you in the trunk. Simply the best SQ sub setup I've ever heard, and I'm not just saying that.

Tony

 

if anyone wants it i have an excel program for ported boxes that i made that uses the jl formula. all you do is put in the size of the box the port area and the port depth and it will give you the tuning. its nice cause you can mess with it until you get the result that you want.

 

Yeah I saw the pictures in your cardomain page. Very impressive and simple! You can totally make that setup inconspicuous. Also, unlike the 5th gen, the 4th gen rear seats do not fold down. Also, there's an aluminum plating that supports the rear seat-back which needs to be taken out for this kind of setup. Also, the trunk opening is not quite as big as found in the 5th gen. I did notice that you did what Audionutz recommended regarding membrane diameter size being half the size of the driver's cone. BTW, where did you get the membrane and mesh from? Did you put this together yourself or was there a kit that you can get specific for a particular driver that you have?

 

Hook it up man.......I want it.

 

I can see how the 4th gen would be impractical for this type of box then. Too bad!

I used fiberglass insulation for the resistive element. I cut up 4 10-inch waffle speaker grills for the mesh. It seems to work perfectly. There is a kit made by USD (that's quite expensive) for specific woofer size, but not specific woofers. http://www.usdaudio.com/products/ap.php

Tony

 

So how did you calculate the amount of fiberglass needed to exactly tune your system? The fiberglass is the same stuff you'd get from Homedepot for home insulation? Would the mesh keep the fiberglass from getting all over the trunk? I remember years ago when people would use this kind of material to dampen their ported boxes and there would be fiberglass debris all over the trunk because they exit through the box port holes while the subs are going.

I just read this from the article:
That definitely made the decision for me as I am a big hip-hop and trance listener. Too bad x2.