Infinity 12.1 Perfect's

[synapsis]

Alright, so a few weeks ago i thought it was about time to make myself a couple DIY subwoofers, as i have a complete home theater system except for a sub! I was combing DIY fourms when i came across a plate amp made by MCM (mind you, it got shipped in a dayton box...) at 300W RMS for 85$. I picked up two. The next day at work, i had to come up with a driver for the box, and it just so happened that my store had demoed a pair of Infinity 12.1 Perfects in the store, without ever hooking them up, and they had just gone clearance. Lucky me, i picked up the pair for 120$.

After all of this, i figured i had hit a sang, as i had no idea (well i had SOME idea ) how to build a custom design subwoofer box that would fit the woofers acoustic properties. Avaserfi and WmAx gave me a bunch of advice, and now im on my way to design a proper box, modeled after avaserfi's box for his VQ (however, mine wont be nearly as complicated, as im making two and am not that articulate in my woodworking ).

So im planning to build a 3.95 cubic feet, with relatively the same dimensions as avaserfi, with 4 inch mineral fiber board dampening and some cross member bracing. The slot port will be the same as well, and im assuming back slot ports are the way to go? And other than some MDF, hardwood for bracing, and the mineral fiber board, is there anything else that needs to be added?

Im going to post some pics of what ive got, it'll be a slow build but i can keep everyone up to date.

Just want to shout out to WmAx and avaserfi for all the great help!

 

[synapsis]

alright, so my friend happens to work at rona, where im going to pick up some 1" MDF for building my box. Having never had to worry about a plate amp before, im wondering how to design the slot port. After looking at avaserfi's box, i realize i can't create my port like this, as it would be "in the port", if mounted on the back.

Im wondering if i should make a seperate chamber for the amp at the back of the box, and make the slot port longer along the width axes... but im concerned this will cause overheating of the amp... so i was wondering if cutting a small round hole would allow air flow, but would it cause harmonic distortion as well?

Should i just mount the plate amp elsewhere on the box? How does velodyne and other slot ports with plate amps on the back design their boxes?

Thanks
Dustin

 

[treejohnny]

I am building perfect kappa sub as well. I am getting closer to being done, I am having hard time finding the 8# miner board. Here are a couple of pics of my work in progress. I was planning on using a plate amp when I started and switched to the behringer ep2500, which I got from the brown truck tonight. Now I will have start another project, building or buying new stand for audio equipment and tv stand as it dont look like the rack mount comes off of the ep 2500.


I still need to borrow router and open up the outside wall for the port, as my router died on the construction.

 

[annunaki]

Looks pretty good. Are you using MDF and particle board together???

 

[synapsis]

i think ive decided that i will be making a seperate chamber at the back of the box for the plate amp. If need be, i can drill a hole in the back to give some airflow out, so as not to overheat (hell, maybe even put a nice little fan in there that kicks on whenever the amp is on). This way i can still have the staggered slot port like avaserfi. However i will have to run the + and - terminal wires through the port, along an edge. But if i drill a couple holes and caulk\silicon it down.

I wish i was good with autocad or something, so i could show everyone what i was looking at doing... ah well

Materials will be bought this week

 

[treejohnny]

I started using mdf, then I ran out.....got a 4X4 piece that was in the mdf area. Is this bad ?
I should have known better.....it was at closer store and I thought it drilled much easier...

 

[avaserfi]

i think ive decided that i will be making a seperate chamber at the back of the box for the plate amp. If need be, i can drill a hole in the back to give some airflow out, so as not to overheat (hell, maybe even put a nice little fan in there that kicks on whenever the amp is on). This way i can still have the staggered slot port like avaserfi. However i will have to run the + and - terminal wires through the port, along an edge. But if i drill a couple holes and caulk\silicon it down.

I wish i was good with autocad or something, so i could show everyone what i was looking at doing... ah well

Materials will be bought this week

Instead of mounting another box for the plate amp I would recommend building a small separate rack mountable box for the plate amp. This way if some day you want to upgrade to another amp you don't have to rework the box at all.

As far as finding a place for the binding posts the bottom of the box works well. I stuck mine on the bottom and its working out just fine, plus it looks better IMO. Also, bottom placement of the binding posts is a far better ideal than running anything through the port I would try to avoid doing that if I were you.

 

[WmAx]

I am building perfect kappa sub as well. I am getting closer to being done, I am having hard time finding the 8# miner board. Here are a couple of pics of my work in progress. I was planning on using a plate amp when I started and switched to the behringer ep2500, which I got from the brown truck tonight. Now I will have start another project, building or buying new stand for audio equipment and tv stand as it dont look like the rack mount comes off of the ep 2500.


I still need to borrow router and open up the outside wall for the port, as my router died on the construction.

Looks good so far. What exact driver are you using? Perfect 12.1? 12.1D? Perfect 12VQ? 12VQD?

Please specify the exact internal volume and port length width and height.

As for the amp, I would agree with Andrew: make a seperate enclosure for the amp(s) so that you can upgrade later if so desired.

-Chris

 

[WmAx]

Im wondering if i should make a seperate chamber for the amp at the back of the box, and make the slot port longer along the width axes... but im concerned this will cause overheating of the amp... so i was wondering if cutting a small round hole would allow air flow, but would it cause harmonic distortion as well?

Should i just mount the plate amp elsewhere on the box? How does velodyne and other slot ports with plate amps on the back design their boxes?

Thanks
Dustin

I have never recommended amplifiers to be built in to cabinets. Build a seperate box for each amp and have it outside of the subwoofer. What will you do in the future if the amp breaks, for example, and you have to replace it with another that is a different size? But if you do go the route of building it in, I would build a recessed box for it sit into. I don't entirely trust these amps to be 'air tight'. An air breach in a ported enclosure can cause substantial reduction of performance.

-Chris

 

[synapsis]

what difference in sound does changing the port from the back to the front make (if any...).

I assume with corner placement in a room and a back firing port, the lower frequencies are amplified, does a front port take away that extra low end gain as it is shooting out into the room rather than reflecting off the corners?

 

[Sheep]

Rona means you're in Canada. All the local Rona's near my house don't carry 1inch MDF. 3/4inch Oak Ply is better anyway.

SheepStar

 

[avaserfi]

what difference in sound does changing the port from the back to the front make (if any...).

I assume with corner placement in a room and a back firing port, the lower frequencies are amplified, does a front port take away that extra low end gain as it is shooting out into the room rather than reflecting off the corners?

Port location doesn't matter just be sure to place the subwoofer properly. You will want the port to be at least 6 inches from a boundary.

As far as room gain goes corner placement will give you the most, but might not be the ideal location in your room for overall response. To get ideal response I suggest using Room EQ Wizard found at the HometheaterShack (its free) and just spend some time moving it around. This will also help determine if equalization as well as further acoustic treatments would benefit your room and possibly how much.

Rona means you're in Canada. All the local Rona's near my house don't carry 1inch MDF. 3/4inch Oak Ply is better anyway.

SheepStar

Plywood is a superior choice to MDF in terms of weight and rigidity, but the type of ply doesn't really matter as long as it is at least "cabinet grade" (referring to the actual layers of ply used). All the forms of ply I have seen that are classified as a specific type of wood refer to the laminate finish not the actual wood used to my the layers of ply.

 

[treejohnny]

I am using the perfet kappa 12 VQ the box I designed needs some tweaking as I have made some miscalculations. I just got done measuring all that I have done and since I changed plans and went with external ep 2500 instead of plate amp and made some minor changes in overall sizes for better construction. I will have to add 4.1" to port and then fill .775 cu ft of enclosure.

Will there be any noticeable differences if I do use the particle board doubled up on the encosure ?

 

[synapsis]

The rona in my area does in fact have 1" MDF, however i will weigh cost vs benefits of ply when i get a price quote from my friend in store. I have been working up a storm trying to find the easiest \ cheapest box to build.

Right now ive come up with a box that is 30"H x 18"D x 18"W exterior dimensions (my first design was 24"H x 18"D x 24"W). I havent decided which of the two i will use, will the "boxier" have a different sound than the "taller" box?

I have also been trying to figure out how i will design the port, as using the plate amp mounted in the cabinet (i know, everyone says not to do it, but i want that nice clean manufacturers look) on the back, renders the back wall useless for port applications.

Thus i have to run the port along the bottom of the sub, making me mount the subwoofer itself higher on the cab than i wanted (though i suppose it doesnt really matter if the sub is mounted right at the bottom vs 12" from the bottom).

Either way i should be able to get away with building the whole box from a single 4x8 sheet of MDF, braces included. Any thoughts on which box would be better?

 

[treejohnny]

I thought I could build whole box from 4X8 sheet as well...but by the time i got done with the 5 outside edges and the port the sheet was gone. I bought a 4X4 sheet afterwards and it is gone as well. All that is left is the scraps, which I hope will be enough to finish my box. Of course I do have some small pieces of 3/4 plywood as well....this box will look like hodge podge from the inside. lol

Are you gonna have the driver down firing or foward firing? You could always port out the back or bottom. What are the dimensions of the plate amp?

 

[synapsis]

I am going to front fire the driver, with the slot port coming out the back.
I think ive finalized my box now, going with the 24"H x 18"W x 24"D. The plate amp is roughly 11" x 10" x 6"D, which will be mounted into the back of the box. The slot port will be two full sections at the bottom of the sub, plus a little bit, giving me 16"x3" 54" long.

This makes my sub about 8 inches from the bottom of the box when front firing. I wish i could have it lower, but the slot port wont allow it. C'est la vie.

I have a feeling you are right, that i will need another 4x4 sheet (probably of 1\2" or 3\4") of to finish the job, as i want to double up the front for flush mounting, and take up some more volume on the inside with braces to strengthen and match up the perfect volume.

 

[MY99 2.5GT]

What software did you use to calculate box and vent size?

 

[avaserfi]

What software did you use to calculate box and vent size?

WinISD is a free program that can be used to calculate all the needed information. Be sure to not only look at box and vent size, but air velocity cone excursion etc...

 

[synapsis]

did a couple of quick calculations this morning. I found that my overall volume, after bracing and mounting the woofer and the plate amp should be bang on at 4.05. This is excluding the fiber board as i was told not to take this into consideration when calculating volume. Now that i've finally got everything figured out, i just need to get some exams out of the way, and get on to building this badboy!

Im just going to start with one at a time, this way when i go to build the second one, i should have a few tricks up my sleeve to help speed up construction.

Im slightly worried about my port however.

Will 16"x3" 54" long cause me any port resonance? Other than rounding off the corners, does anything else help make the port quieter so it will be less "chuffy" or airy?

Thanks again

 

[avaserfi]

Will 16"x3" 54" long cause me any port resonance? Other than rounding off the corners, does anything else help make the port quieter so it will be less "chuffy" or airy?

I just modeled the Kappa Perfect 12.1 in WinISD with your box size of 4.05 cubic feet and the port you mentioned 16"x3"x54". It seems your tuning frequency will be 23Hz with first port resonance at 125Hz which will be okay if you integrate the subwoofer with a sufficiently steep crossover.

If you properly round all the corners and use a radius of at least 1" I highly doubt you will have any audible chuffing. I know I haven't. Be sure to have rounded areas placed at the junctions where the slot intersects with the cabinet if you round the port otherwise your effort will be in vein.

Here is an example: