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Need Help with subwoofer design

post #1 of 24
Thread Starter 
Hello, I am totally new to this hobby and I need some help with my subs. I have a couple friends locally who directed me to come here for some answers. Here is what I'm working with.

Completely enclosed basement room 18 x 22.

I have purchased 3 fusion 10 kits, and 2 of the 8's. Also will have Onkyo 818.

Inuke 600dsp.

2 SI 18" 4 ohm drivers.

I have a complete sod shop at my disposal so I can build pretty much anything. The cabinets for the front and surrounds pose no challenges. The subs on the other I hand I've learned are way more than just a "box".

I was introduced to two different threads, the MartySub, and a Sonotube thread. I like the Idea of the Sonotubes for many reasons, footprint, simplicity, cost....

I am planning on getting this up and running with the 2 drivers and maybe down the road add two more. my question is with my room size which of the two are going to give me end result? Sealed, ported, tube, cabinet.....???

I have been trying to do as much research as I can. Like I said building these won't be the problem, just building them correctly. I have learned with a ported design the size and length of the port can be very important. I just don't want to spend the time to build a cabinet and it be all for not.

Any info will be very appreciated.

Thanks.
post #2 of 24
Quote:
Originally Posted by Jawbone311 View Post

Sealed, ported, tube, cabinet.....???

Based on your room size, I personally would lean towards ported for the higher output. That's based on the limited information at hand.
post #3 of 24
Thread Starter 
I was told to go ported as well by a friend.

Does anyone know the dimensions for a Porte sono build with an SI 18? I heard I should shoot for 11 to 12 cubic feet which is no problem with a tube.

Just don't know about the port dimensions. I was thinking about building an adjustable port with much smaller tube that slid in and out. Then my friends can come over and measure what it's producing. Is this possible
post #4 of 24
sounds like you are looking at the right options...a largish lowish tuned sub for your drivers would get the most out of them.

sonotube/sonosub is probably the easiest to build. with 24" tube, the area is roughly pi (3.14) square feet, so that multiplied by the height will give the volume (less the port of course). so a 5 foot tall sub would be about 15 cu ft internal before port and driver. no internal bracing needed in a sonosub. a 10" diameter port would work great and would tune the big sub to about ~17hz if it were about 40" long. first port resonance would be up around 155hz, so no problem there. 3-4 pillows from walmart stuffed in the enclosure will help minimize standing waves in the enclosure itself. allow the driver at least 4" of clearance on the bottom. really not a whole lot to it once the basic construction plan of a sonosub is understood.
post #5 of 24
and...a sonosub will perform the same as a "box" sub of the same internal volume and tuning. it's just a different form factor.
post #6 of 24
Thread Starter 
Thanks for your response this is exactly what I needed. based on your numbers here is what I am calculating for volume.

Main tube = 3.14 * (1 * 1) * 5 = 15.7 cubic feet

Port = (3.14 (5" * 5") * 40") * .00057870 = 1.817 cubic feet

Subtract the two and I come up with 15.7 - 1.817 = 13.883 cubic feet

Now this is not taking into account the thickness of the port, the top and bottom mdf rings, and the amount of space the driver takes up. I'm guessing all this will total a little over 1 cubic foot.

attached is a crude drawing, is this where I would position the port?

Thanks!

post #7 of 24
You don't have to be that accurate either. Small changes in volume make very little difference.
post #8 of 24
"attached is a crude drawing, is this where I would position the port?"

yeah, you've got it.

also, as joe (jpmst3) mentions, with a relatively large cab like this, small differences in volume/port length/etc. won't make a material difference on performance.

from your net internal volume, also subtract out about 1/3 cubic foot for the driver itself. I think I was running 13.5 cu ft net in winisd. edit: I see you mentioned that and the end caps, so yes, you are right on track.
post #9 of 24
here are some pics of one from another thread. he made a speaker grill cloth cap to go over the port, but that is not required.

not sure exactly what size his are.




post #10 of 24
That is a great example.
I love seeing that little SVS next to them. Hilarious! biggrin.gif
post #11 of 24
post #12 of 24
Quote:
Originally Posted by Jawbone311 View Post

Hello, I am totally new to this hobby and I need some help with my subs. I have a couple friends locally who directed me to come here for some answers. Here is what I'm working with.

Completely enclosed basement room 18 x 22.

I have purchased 3 fusion 10 kits, and 2 of the 8's. Also will have Onkyo 818.

Inuke 600dsp.

2 SI 18" 4 ohm drivers.

I have a complete sod shop at my disposal so I can build pretty much anything. The cabinets for the front and surrounds pose no challenges. The subs on the other I hand I've learned are way more than just a "box".

I was introduced to two different threads, the MartySub, and a Sonotube thread. I like the Idea of the Sonotubes for many reasons, footprint, simplicity, cost....

I am planning on getting this up and running with the 2 drivers and maybe down the road add two more. my question is with my room size which of the two are going to give me end result? Sealed, ported, tube, cabinet.....???

I have been trying to do as much research as I can. Like I said building these won't be the problem, just building them correctly. I have learned with a ported design the size and length of the port can be very important. I just don't want to spend the time to build a cabinet and it be all for not.

Any info will be very appreciated.

Thanks.

Welcome to AVS, neighbor! :) You're definitely going to get the right build advice here.

 

Quote:
Originally Posted by LTD02 View Post

sounds like you are looking at the right options...a largish lowish tuned sub for your drivers would get the most out of them.

sonotube/sonosub is probably the easiest to build. with 24" tube, the area is roughly pi (3.14) square feet, so that multiplied by the height will give the volume (less the port of course). so a 5 foot tall sub would be about 15 cu ft internal before port and driver. no internal bracing needed in a sonosub. a 10" diameter port would work great and would tune the big sub to about ~17hz if it were about 40" long. first port resonance would be up around 155hz, so no problem there. 3-4 pillows from walmart stuffed in the enclosure will help minimize standing waves in the enclosure itself. allow the driver at least 4" of clearance on the bottom. really not a whole lot to it once the basic construction plan of a sonosub is understood.

LTD, thanks for chiming in.

 

Since Jawbone is brand spankin' new to the home theater scene, I recommended the ported route. That will get him the most bang up front...and then once we get him hooked, he can go after the last couple of octaves... :cool:

 

Is it possible to get a 12-13hz tune with sonotubes with an 8ft ceiling? My recommendation was to tune the sub as low as possible...

 

-Dom

post #13 of 24
Thread Starter 
Thanks Dom! I can't wait to get started on these. I found a 12 foot tube for 88 bucks. Can't beat that.

If 12 to 13 is what I need, then that's what I want to build if it can be done.
post #14 of 24

What size Sonotube would jawbone need to get to a 12hz tune? Or better yet, he has 8ft ceilings, what is the lowest tune that he could get with a sonotube in that room?

 

Would someone mind running it through winisd?

post #15 of 24
6' H.. 25" diameter sono 15hz to 12hz tune ok 20cf. You would need to add about 6-8" for the base and top cap though.
Edited by steve nn - 2/6/14 at 7:51pm
post #16 of 24
"Is it possible to get a 12-13hz tune with sonotubes with an 8ft ceiling? My recommendation was to tune the sub as low as possible..."

yes, but with the si drivers, they run out of excursion before they run out of power in a very large low tuned sub.

here is max spl with a 20 cubic footer tuned to 12hz and a 13 cubic footer tuned to 17hz.

the low tuned sub goes lower of course, but at the expense of less spl around 20hz. opinions on which is best will differ and it really depends on what the user is looking for. generally, I'd point folks to the 17hz tuning, but that is just one opinion.

what creates that "dip" is where the driver is running out of excursion for those who aren't familiar with this kind of plot.

post #17 of 24
"What size Sonotube would jawbone need to get to a 12hz tune?"

if we limit maximum port length to 44" so as to keep the resonance kind of out of the passband...

and we limit the minimum port diameter to at least an 8" to keep air flow kind of under control...

then the minimum enclosure size for a 12hz tune is about 19 cubic feet.

better would be 40" port length, 10" port diameter, a slightly higher tuning, perhaps 15hz...gives a minimum enclosure size of almost 20 cubic feet on the button.
post #18 of 24
Quote:
here is max spl with a 20 cubic footer tuned to 12hz and a 13 cubic footer tuned to 17hz.

+1 I think members loose sight of that chasing the real low tuned options. A nice tune of 15-19 works very well and is a better rounded choice imo. (it’s also good to take room gain into account if a guy knows) I once had to take the skill saw to a sub I tuned to low, it really lacked vesicle impact. Thus sneaking the 15hz option in even though just asked for just the 12hz tune. wink.gif
post #19 of 24
I would not recommend going with the 12hz tune as you would likely be sacrificing mid-bass in the 40hz to 120hz region, right? I think something like a 17hz or 18hz tune is ideal, as you can't even hear anything below 20hz, and most of the wow factor is achieved in the 30hz and up category.
post #20 of 24
Quote:
Originally Posted by Martycool007 View Post

I would not recommend going with the 12hz tune as you would likely be sacrificing mid-bass in the 40hz to 120hz region, right? I think something like a 17hz or 18hz tune is ideal, as you can't even hear anything below 20hz, and most of the wow factor is achieved in the 30hz and up category.

In general I would agree with you Marty except to say if a guy knows his room it can add or detract from what options might be best suited for the user along with knowing what he prefers. So I wouldn’t go so far as to make a sweeping statement, but in my experience so far (I only built one really/super low tuned sub once and placed it in a certain room) and that was the case. Different people have a different sensitivity regarding their hearing when it comes to the 20hz freq and below also. I never could understand some posts until I was corrected regarding. Say like you can see something and I can’t, our hearing is like that also.
post #21 of 24
Quote:
Originally Posted by Martycool007 View Post

I would not recommend going with the 12hz tune as you would likely be sacrificing mid-bass in the 40hz to 120hz region, right? I think something like a 17hz or 18hz tune is ideal, as you can't even hear anything below 20hz, and most of the wow factor is achieved in the 30hz and up category.
In my room, 30hz and up is great, but a lot of systems (on avs anyway) can reproduce this at reference levels, so it becomes par for the course, IMO. The wow factor to me is those that can produce it 20hz and below. In my room, it's 10-16hz or so.

Also, according to ltd's graph not much is lost from 40 and up.

You guys bring up a good point though about sacrificing 20hz with this driver...he's in a concrete bunker so will get some room gain down low (15 and below) but not as much gain at 20hz. 15hz may be the way to go as he'll keep the 20hz output, and potentially have some room gain to get him useful output to 12 hz or so.
post #22 of 24
"I would not recommend going with the 12hz tune as you would likely be sacrificing mid-bass in the 40hz to 120hz region, right?"

not really. you can see in the plots from 40hz up, it is pretty close.
post #23 of 24
Quote:
Originally Posted by LTD02 View Post

"I would not recommend going with the 12hz tune as you would likely be sacrificing mid-bass in the 40hz to 120hz region, right?"

not really. you can see in the plots from 40hz up, it is pretty close.

I stand corrected!
post #24 of 24
If you know what your room response is (say it has a bump in the 35-65hz or a loss in the 15-25ish area) your going to be working at bringing the bump down no matter what.
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