Been going over my sub, having used this sub, other subs, in this car and out - I can't stand the way up-firing subs sound.

Aiming a sub back in a corvette results in a pretty good boost in volume and sound quality, but the problem is: How do you do it?

You can tilt back, which I've done. But this results in volcanoes. Volcanoes are best left to tropical islands.

So, I've come up with this...

In reality, the bottom half will be fiberglass. The top and ring will be mdf or birch. The cone will probably be a modified reinforced concrete tube with (you guessed it) fiberglass.

The transparent section is a curved subwoofer grill. Its just speaker cloth. This allows the sound to easily exit and prevents junk from falling in.

This is scaled for a 12" IDMAX subwoofer. Internal should be a little less than a cubic foot. The top should (just) clear it np.



Thoughts?

 

Protrudes out too much for me, kind of reminds me of my Bazooka Tube.

What about an up firing sub with that kind of half dome cover shape to direct the sound? An acoustic foam insert with the subs logo could be inserted in the opening for a finished look.

Nice idea though.

 

why not just fire them forward from the back in a molded enclosure like i did, it sounds better than rear fired subs.
the secrit is tuing the enclosure by porting it, you get way more output and can use smaller subs.

 

GKK: You can sort of cheat that way with the roof as it is. My sub sounds MUCH better with the spare roof panel over it. But yeah, basically it's half a tube sticking out of the rear.



Forward sounds worse than even up firing to me, and you lose a great deal of cabin gain to boot. My rear fired dual 8s in .33 each in my subaru are louder (over 40hz) than my single 12 in the corvette. (150 to two 8s, vs 350 to one 12)

I don't use porting for more noise. Just to extend low frequency response. The last time I built a ported box it was 2.4 cubic feet and had such a large/long port for sub 30hz tuning that it basically took up the entire back of a tacoma up to the bottom of the windows. It was something else when the music went down to 20hz or so. no need for a subsonic filter.

Of course the big drawback of porting is that the boxes have to be much larger and you have to have an adequate port long enough and large enough to not have any port noise.


I'm also considering getting my old IDQ10 out of storage and putting it in. The IDMAX is a little much, and a bit of a waste with only 1/3 the power it likes.


I've also considered using flat edges rather than round - it would be much, much easier to carpet!

 

Kale... with a fiberglass bottom section there is more airspace than you would think. The preliminary measurement (with sand) on our C5 buck for just the well section is 1.37 cu. ft. This is taking into consideration .325 inch wall avg thickness and an imaginary .325 flat top (flush to the floor). By looking at our buck there should be enough space to shift your sub down even more and minimize the hump protrusion.

I would flare the bottom section rather than conform it around the sub diameter. That will minimize anomolies and, considering the subs you might use, it will help to minimize suspension rocking due to pressure differences. Subs designed around motor control wouldn't be an issue but subs with tight vc gap and centering reliant mostly on sustpension (like ID) will most likely have premature failure due to coil rub with your current sketch.

Hope this helps.

 

Good point, I hadn't even thought of that. The Max is a bit of a picky sub.

 

i disagree, my boxes fill up the entire top to bottom clearance of my vette hatch in each corner and are only .55 cu ft. essentially they make the rear wall of the trunk a little closer. when you build a sub this way you will not get any cancellation because there is no place for it to be cancelled.

facing rear is the easiest way to eliminate this cancellation problem, it does extend the wavelength and a sealed box will benefit from the cabin gain. however a correctly aligned ported box configuration will accomplish the same thing by lowering the f3 and the cabin gain lost pointing forward more than makes up for the gains of a sealed facing rear.

as for port noise it's only an issue for sustained bass tones below 30 hz and if you chamfer the ports on both ends it is mostly eliminated.

in my experience and it varies by sub of course, people stuffing a 10 for example in .75 cu ft sealed never really get much bottom end. mostly 60 hz and above that same sub would perform better in 1 cu ft and be more efficient.
if you take the same sub and port it 1.1 cu ft is mor ethan enough to tune to 38 hz with a reasonably short port (less than 12 inches usually) depending on the diameter. also even tuned this high i have never in 18 years of doing systems ever needed a subsonic filter. i simply don't play freq's low enough to be a problem.
when i build a ported box i will usually favor the shorter port length and smaller diameter unless my vent velocity is excessive, in thoes cases ill run 2 ports or better yet a slot port so i can adjust my vent velocity while maintaining the correct tuning frequency without excessive length.
with that in mind yes a ported box will be larger than sealed, but in real world i do not believe .6 cu ft as in my example larger given the additional output and lower frequency responce is giving up anything.
in your example of the 8's in .33 cu ft i am running 8's in .55 ported.

in addition to that consider this..
if someone wants the bass of a pair of 10's for example i can build a box with a pair of 8's in the same airspace as 2 sealed 10's that plays louder and lower than the sealed 10's. so to say it takes up more room would be inaccurate.
unless someone has somthing to prove by getting bigger subs because they are lacking or making up for somthing else lacking in the eyes of their male counterparts!
i do not see the point so many people seem to be trying to make with the argument of a ported box has to be bigger. if the overall finished outcome performs better, plays lower, is more efficient, who cares what size subs you use?
i built a box for someone once under the seat of a chevy full size pickup and there was no clearance for much of anything, so i went with (4) 6.5" drivers ported and everyone who sits in it is totally dumbfounded as to how we got so much bass in so small of a space.

yes it has to be bigger, bigger by just about the amount of space needed to accomidate the port itself. ive built boxes that had external ports that i was able to snake to a different location that took up NONE of the internal space of the box.
and if i can get better results with a size smaller driver in the same space why wouldnt you?

your quote of:
Of course the big drawback of porting is that the boxes have to be much larger and you have to have an adequate port long enough and large enough to not have any port noise.

is a little difficult to understand since the larger the box, the shorter the port, in my case the boxes are still pretty small and the ports are a little longer but compared to what? is 12 to 13 inches to long? as long as i can fit in the box and it doesnt make noise what's the problem?

 

A 10" subwoofer in a 1.2 ft^3 box in the back may work just as well - I won't disagree with you there. But I've got a 12" sub to work with.

I did mention my IDQ10, but I'm pretty sure it's the wrong impedance and it's buried in storage. I'm a firm believer in overpowering speakers, but I'm not sure I'd want to put 350+ watts on a 10 year old 200w subwoofer in a ported box.


And porting an IDMAX is going to call for 2+ ft^3. And the port will be obnoxious since I'll have to tune it under 30hz to avoid the nasty 40hz peak in a C5.

I used a slot port when it was in the truck - something like 25-27 inches long.


Although you remind me - I built my dual 8 box in my subaru so I can move a wall in the box to expand it to .6 per 8 and be able to port it... I just never did on account of the lazy.

 

thanks for the reply, i kinda expected you to lash out at me. so many people online can't deal with any kind of constructive critisizm difference of opinion. its actually nice to chat with someone who obviously has some knowledge on the subject!
i wish you lived a little closer to colorado, if you could hear my setup you would be quite impressed i am sure.
i absolutly love the way my staging sounds. i dont know if you saw my thread or not about the build i did in my c6z i went all JL audio. ran their ZR800 components in the doors threw 300 watts at the pair went with a 3.5" 2 way in the top of the door.

to be honest i went out a little on a limb aside from what most people would have done putting a simple component set with a 6.5 or smaller where the sub used to be and a tweet where the 3.5 used to be.
i am so glad i stuck with my gut on my install.

i had no idea you could get such good sound staging and SQ from a 3.5" speaker and the bass in my car is just incredible from every frequency.
it makes me want to drive the car more just to listen to the system.

 

Shoot, if you can make it sound good, which is the hardest thing to do with small enclosures, who care what it looks like.

If you told me it slammed, and sounded nice doing it, I'd pay you for a set today!

Good luck, nice drawing...