Dual 12" bipolar subwoofer

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Here is the new woofer I'm in the process of building for my combined HT/2 ch system.I wanted to update my aging DIY dual 10" woofer setup with something that would extend deeper into the bass and play louder with less potenial for distortion or over excursion.This sub will be used to augment my main speakers only and will not be used for the LFE channel as I have a pair of woofers already serving that purpose.

The Infinity 1242w car subwoofers I chose are certainly far from exotic but they will work perfectly in my intended enclosure.Using a pair will increase sensitivity by 6 db so they won't need to be driven as hard as a single unit ,plus distortion will be reduced and power handling increased.
I generally prefer the sound of low Q sealed boxes over ported designs so thats what I will be using.

I will be mounting the drivers opposed (one facing forward one back) in a bipolar arrangement that will help cancel cabinet vibrations. As the pics show I also braced the heck out of it so it should be fairly inert and heavy.

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here are some pics.

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anonymouse wrote: »

How did you model out that box?

I used Win ISD to do all the response modeling.

zingo

Looks good and I still claim that you are the DIY subwoofer king.

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zingo wrote: »

Looks good

Thanks

and I still claim that you are the DIY subwoofer king.

uummm definately not ,just an enthusiastic hobbyist.:D

zingo

GV#27 wrote: »

Thanks uummm definately not ,just an enthusiastic hobbyist.:D

Well you run circles around me, and I have some fair electronics experience. Cool design for the box, and way to go with the car subs. I like a project that goes outside the box.

ward91

i got so fed up of using win isd (both of them, beta pro ? and the other one)to model my box i just built an approximate one coz i got fed up of trying to accurately calculate the volume minus the batons in the sub and the effect of foam ect.
i have always wanted to know how to compensate in the modelling/design about putting foam in the box , my sub (custom) was sealed but at the time i didn't have a decent amp to drive it and id didn't sound much. i went for a rather risky port frequency at 17hz just to seem what it sounded like. the port defiantly changed the sound and yup it did unfortunately boom things up a bit, so i had to be extra careful with placement.

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zingo wrote: »

Cool design for the box,

I wanted it to take up as little floor space as possible and I will be placing it in a corner.So it ended up being 48" tall and it only takes up a little more than a square foot.

way to go with the car subs.

As long as they have the correct T/S parameters there is no reason a driver designed for car use can't be used in a home sub and these ones suited this project.Also I had budgetary contraints impossed by my lovely bank manager/accountant so these were inexpensive Ebay snags.

jakelm

What are you driving them with? Subs ran bi/polar does not cause a phase problem? And Ohms will double? Its still sealed, if I understand correctly, stuffed/padded? That is a small Thiel design.

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jakelm wrote: »

What are you driving them with?

Either a Bryston PP120 or ICE Power ASP 250 classD module,I have both units so I will try and see which I prefer.

Subs ran bi/polar does not cause a phase problem?

No,they are wired in phase and though they face in opposite directions, both woofers move outward and inward at the same time(push-push) so no cancellation will occur.

And Ohms will double?

drivers are both 8 ohm but wired in parrallel so impedance will be 4 ohms.

Its still sealed, if I understand correctly, stuffed/padded? That is a small Thiel design.

Yes it is just a regular sealed designed using the Theile/ Small parameters.There will be some polyfill or fibglass stuffing.

jakelm

GV#27 wrote: »

No,they are wired in phase and though they face in opposite direction both woofers move outward and inward at the same time(push-push) so no cancellation will occur.

Ok, I must be confusing it with di/polar. "di" is out of phase, "bi" is in phase.

I'm curious to hear your thoughts after everything is up and running.

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jakelm wrote: »

Ok, I must be confusing it with di/polar. "di" is out of phase, "bi" is in phase.

Yes.

I'm curious to hear your thoughts after everything is up and running.

I have to get my butt in gear and get it glued together then veneered.Probably 1-2 weeks.

jakelm

Curious, the walls in the middle of the box. Are they for a sonic or purpose or just for bracing?

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jakelm wrote: »

Curious, the walls in the middle of the box. Are they for a sonic or purpose or just for bracing?

Strictly for bracing.

jakelm

GV#27 wrote: »

Strictly for bracing.

Fairly inert and heavy? I'd say fairly...lol

48" x ? x ? Looks about 14" x 14" x 48"

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jakelm wrote: »

Fairly inert and heavy? I'd say fairly...lol

With the drivers added it will be.

48" x ? x ? Looks about 14" x 14" x 48"

Close, 13.25" x12" x48".

jakelm

Very small footprint. Cloth cover or paint?


You know so many of us are looking into sono tubes. Its nice to see something alittle different and square.

Since I cant seem to find a sonotube anywhere, I was thinking of building something like what you have. And my wife would have yet another place to put a plant...

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It will be veneered like this one.

jakelm

Nice,,

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jakelm wrote: »

Nice,,

Thanks,the new one will be in the opposite corner so visually it equals the room ... atleast thats what I told the Mrs.:D


I removed the bass trap behind it so it actually sits tight into the corner as will the new one.

ShinAce

Looks great. I love the fact that you routed or cut channels for the bracing panels. Should come together like lego, if your saw is square.

Let me know how the dipole responds in room, I'm interested to find out if it'll smooth the overall response throughout the room.

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ShinAce wrote: »

Looks great.

Thanks

I love the fact that you routed or cut channels for the bracing panels. Should come together like lego,

I used a stacking dado blade,and yes it makes assembly much much easier.The pics were taken with it just press fit ,no glue.

if your saw is square.

Yep,its dead nuts square.:D

Let me know how the dipole responds in room, I'm interested to find out if it'll smooth the overall response throughout the room.

Slight distinction, its bi polar and I'm not sure if it being so will help the in room response or not,but one maker of commercial bi polar subs(Mirage) claims it does.I will let you know after I get a chance to test it out and compare to my non bi polar unit.

jakelm

GV, why not slap a nice plate amp in there? Or are you more of an external amp guy?

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jakelm wrote: »

GV, why not slap a nice plate amp in there? Or are you more of an external amp guy?

http://www.bryston.ca/pp120sst_m.html
The Bryston PP120 I have will bolt right to the back of the box if I decide to use it.It does not have an integral crossover like a plate amp but I already have that and specialized EQ in a separate chassis.

jakelm

Ever looked at Rythmik plate amps? I am using one for each sub, they are really work horses.

jakelm

GV, you might know this answer,

I'm working with an SVS 12.1 driver. I am planning to built an enclosure similar to yours. 16 X 16 X 48... 5.6cuft. The SVS tubes are 16 dia, 46H, 4.2 cuft.

Since there are no prameters for the SVS, how do I know if I am going to have too much air space? There is a point where too much air, is like free air.

Is my enclosure too big? Should I stick with the same cuft as SVS?

jakelm

Im really suprized Ben hasnt chimed in

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jakelm wrote: »

Should I stick with the same cuft as SVS?

Jake, if you want the same response as the stock SVS then yes the internal volume and port size need to be very close to the same on your custom box as in the SVS tube.(Also don't forget to deduct volume for bracing etc). If you want to experiment with different volumes and port tunings then you would need the T/S parameters of that driver and do simulations with Win ISD or Unibox.

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jakelm wrote: »

Ever looked at Rythmik plate amps?

Yes I have and interestingly would likely be my first choice for a plate amp.It is one of the few that have the option of using a customized EQ circuit (Linkwitz Transform)which my design needs.Rythmics 12" and 15" kit designs look to be really good designs as well.

jakelm

GV#27 wrote: »

Jake, if you want the same response as the stock SVS then yes the internal volume and port size need to be very close to the same on your custom box as in the SVS tube.(Also don't forget to deduct volume for bracing etc). If you want to experiment with different volumes and port tunings then you would need the T/S parameters of that driver and do simulations with Win ISD or Unibox.

Yeah, thats what I thought, after bracing I would probably be around 4.8cuft. And instead of 3-3" ports, 1-6" or 1-4" port will do. Unfotunatly SVS dose not provide specs on thier drivers, so I will have to wing it.

Did you get any more accomplished on your project? Or are you letting the glue dry?

jakelm

GV#27 wrote: »

Yes I have and interestingly would likely be my first choice for a plate amp.It is one of the few that have the option of using a customized EQ circuit (Linkwitz Transform)which my design needs.Rythmics 12" and 15" kit designs good to be really good designs as well.

The only issue i have is the roll off for their xover. Its only a 6db, I would have prefered a 12db stock roll off, with out mods. But I can say i love the "rumble" filter. Saving the life of my drivers. The amp realy has great options for tuning. And dont let the 350watt scare you. My SVS **** when its cranked. The amp can easily over excurse the drivers. I wished the SVS had alittle better Xmax.

If you can, explain Vas for me. Is that the airspace? What exactly is that? It reads in cuft, but I dont quite understand.