[andyswof]

I have been reading these forums forever it seems and I am looking to put two ACI SV-12's inside my stage build. At 16w x 15h x 120long I can get the 466l enclosure with bracing WinISD recommends. I can either face the driver to the front with two 4" ports to the sides or face the drivers towards the sides with slot ports underneath the drivers. I am considering an O audio 500w plate amp for power, tuning would be to 18hz. My stage would be 18" high so I can basically build 2x4 walls for the joists and then line the walls with 3/4" mdf for the enclosure. Attaching the walls to the 2x4's should add significant bracing the the sub. This design would also take looks out of the equation.

My qestions are these being a 1st timer:

1. Are there any hidden drawbacks in my described design, something I am not thinking about?
2. The power side is not my strong suit, tips on wiring the two subs with one amp would be appreciated.
3. What are the thoughts on side or front mounting for the drivers? My preference is for side because that allows me to do a dvd shelf in the front and they would be better protected on the sides. My fear is the sound quality would suffer if driving into the walls (approx. 4' away) near a room corner.
4. If looks are not a factor, is screws for attaching the mdf an ok idea? People seem to shy away from using screws.

The driver info is as follows:

Impedance: 4 ohm
RMS Power: 350 watts (system power 500 watts)
Sensitivity: 90dB
Fs: 17.5Hz
BL: 8.9 Tm
Qms: 8.35
Qes: 0.41
Qts: 0.395
Vas: 250 liters
Cms: 1041.67
Mms: 99 grams
X-max: 12.87mm peak
VC Ø: 2" (51mm)
VC Height: 31.75mm
Air Gap Height: 9.652mm
VC Inductance: 1.45mH
VCR: 2.97 ohm

Frame diameter: 12-3/8"
Cut out hole diameter: 11-1/8"
Flange thickness: 3/8"
Depth: 5-13/16"
Overall height: 6-3/16"

Any other advice would be welcome. Again I am a complete noob and just looking for an interesting project and a reason for putting a stage in front of my screen. I have the drivers already but still need the plate amp which will be installed outside of the enclosure but on the side of the stage.

 

[Mike P.]

2 ACI SV-12's work well in 460 liters tuned to 18 hz. The subs will have to be wired in series for a 8 ohm load. That will cut the O-Audio's power in half to 250 watts, which isn't a problem since 250 watts into 8 ohms will take the subs to their Xmax. The high pass filter on the amp will need to be set at 20 hz. 2 - 4" flared ports 11 inches long will get the porting done.

Side firing with the walls 4 feet away won't be a problem.

There's nothing wrong with using screws and glue if you don't have clamps. Just make sure you pre-drill and countersink the holes so the MDF doesn't split.

 

[andyswof]

Thanks for the verification Mike.

A couple of things I have not been able to get my mind around, the drivers are rated for 4ohm but wiring for 8 ohm is no problem? Also, what does the high pass filter do exactly? Will setting it at 20hz kill all response below that or does it just restrain the driver below that to keep from exceeding xmax?

Thanks again for your help.

 

[sub_crazy]

Thanks for the verification Mike.

A couple of things I have not been able to get my mind around, the drivers are rated for 4ohm but wiring for 8 ohm is no problem? Also, what does the high pass filter do exactly? Will setting it at 20hz kill all response below that or does it just restrain the driver below that to keep from exceeding xmax?

Thanks again for your help.

You will need to wire the subs in series to get a 8 ohm load. There is a calculator here which shows you how to wire them:

http://www.the12volt.com/caraudio/boxcalcs.asp

A high pass filter is important for ported boxes as they drop off rapidly after the tuning frequency. if you are tuning the box to 18hz then you need the high pass filter set to around 20hz or you can kiss your woofers goodbye.

 

[andyswof]

Got it, thanks. So there is no need for a larger amp since I at the limit on power anyway.

So I just need to wire the amp using 10 ga wire to the drivers in series and connect my receiver to the amp with a mono imput (my receiver does not have a L R LFE output). I also have a 15" Cadance that I might place in the back or the room to even out the response and I can just run a splitter off the mono output of the receiver if I do that. My room is rather large, 25x25 with 11" ceilings that slope toward the edges, typical bonus room.

Is there any need for stuffing or lining the walls with poly? This is going to be a long 10" chamber for what that's worth.

Thanks for all the input. Any other input would be appreciated.

 

[Mike P.]

The ends will need at least a foot thick of batting, without it you'll have a resonance issue due to the cabinets 120 inch length.

 

[sub_crazy]

I knew I saw a thread with a build the same size your looking to do:

http://www.hometheatershack.com/forums/diy-subwoofers/17534-aci-sv-12-help-needed.html

His box is a ported at 16 cubic feet and of course Mike P. was there to lend a helping hand as well:hail:

Hopefully you can get some ideas from there as well. The OP likes it so you know your on the right track.

I have a few of these drivers as well that Mike P. helped me with too. I am not doing a large ported but a pair of smaller sealed for a family member.

Good luck and let us know how it turns out.

 

[andyswof]

I have see sub made by Jeeper89, it looks awesome. We have the same parameters but since mine is long and inside the stage, it is a different build.

I still have a couple of questions for the gurus of forums:

1: How or where do I add the batting since my drivers are located on the ends? Would two foot in the middle do the same thing?

2: Does the port need to protrude inside the box? I am thinking of running the 11" port through DVD shelf I am placing in front of the stage which would run flange to flange with nothing actually inside the box. I cant see how this would matter but I want to be sure. The port will be facing the front, the drivers in the sides, that shouldn't cause any problems I dont think.

Again, thanks for all the considerate advice. In all the posts I have read this is the best for suffering newbies and I appreciate it.:T

 

[sub_crazy]

I have see sub made by Jeeper89, it looks awesome. We have the same parameters but since mine is long and inside the stage, it is a different build.

I still have a couple of questions for the gurus of forums:

1: How or where do I add the batting since my drivers are located on the ends? Would two foot in the middle do the same thing?

2: Does the port need to protrude inside the box? I am thinking of running the 11" port through DVD shelf I am placing in front of the stage which would run flange to flange with nothing actually inside the box. I cant see how this would matter but I want to be sure. The port will be facing the front, the drivers in the sides, that shouldn't cause any problems I dont think.

Again, thanks for all the considerate advice. In all the posts I have read this is the best for suffering newbies and I appreciate it.:T

On your first question you can just line the walls with a thin layer of insulation or foam as it is ported.

You can have the port on the outside of the box which will free up some space inside to make the enclosure smaller.

If you download WinISD there is a really good help section that I believe covers these topics was well.

Good luck.

 

[Mike P.]

1. I'm not sure. Someone else will have to chime in here.

2. External ports are not a problem:

http://www.subwoofer-builder.com/sidewinder.htm

 

[Mike P.]

On your first question you can just line the walls with a thin layer of insulation or foam as it is ported.

The issue with this build is the 120 inch length of the cabinet. Without thick damping of the ends there will be a resonance problem.

 

[collo]

If you had a single driver in a box with a depth of 10 ft, you would have a resonance at about 57hz.
This is where the distance represents one half wavelength.

Moving to a driver on each end, where the drivers occupy most of the face changes this somewhat.
Because the drivers are in phase, you get a resonance where the distance represents one full wavelength, ie double the previous frequency = 114hz

I would recommend adding a partition to the centre of the box, making two boxes, each half the original volume, and with one of the two ports each. The depth is now 5ft, with a half-wave resonance of around 114hz.

You still have the same frequency to treat, but now you have a nice solid surface to glue / staple your damping treatment to. I would go with some closed-cell foam, and then a couple of thick layers of felt.

 

[Mike P.]

Thanks Bill! :T

 

[andyswof]

Thanks again for all replies. So put a divider in the middle to make two enclosures with batting at the ends as described will resolve any resonance issues. That is simple enough.

The batting is not figured in the enclosure space, correct? Lining the walls, as I have seen in alot of builds, will not be necessary, correct? How would a black rubber closed cell foam used in insulation like Armaflex work in this application, or am I better off with foam for seat cushion's, or does it matter?

Every answer you guys give me brings up a few more questions but I am almost ready to start building.:huh:

 

[collo]

You generally don't adjust the volume for the damping material.
For treating frequencies this low, open cell foam is useless. The closed-cell is better...

 

[andyswof]

I have begun my build. Here is a picture of beginning my bracing. I decided to cut 2.5" round holes instead of boring square holes. I will be adding pictures as soon as I can figure out how to upload the pictures better. I have most of my wood cut and one box mostly glued together. I will be looking to have the boxes completed and doing test runs by the end of labor day weekend.

 

[sub_crazy]

ahhhhh, I love the smell of freshly cut MDF in the morning:bigsmile:

 

[andyswof]

Here is my handy duty circle jig. This bowl was 11" exactly which was perfect for my inside driver hole. I bought a router attachment that was for circles but it didn't work worth a flip so I just marked and used the jig saw.

This is a picture of the driver in the inside hole.

With outside piece on top.

Starting my framing for the stage that is going around my two subs.

Here is my first box getting ready to glue. I like the look of my bracing but it was a lot of work for something that will not get seen. I still have not cut all the holes for the second box.

I will be posting more pictures later. I have one box glued together except for the top and once I get the holes cut for the bracing on the second box it will be glued.

 

[andyswof]

I do have a few vent questions because I dont want to mess that up. Mike P. said to do a 4" vent 11" long flared. I am assuming that I flare both ends? I also read somewhere to use half the radius of the flare for the effective length of the port, can someone confirm this. I am mounting the port on the outside if the enclosure and am installing two outside flanged port connections and mounting on inside of enclosure and outside of the side of my stage.

Thanks again for everyone's help.

 

[Owen Bartley]

Looking good andyswof. Those braces really do look like they took a lot of drill time. I think I remember that if a given port length is specified as flared, you would count the length from the very end of one flare to the other. Usually this only becomes annoying if you have to calculate the centre section length... but I might be wrong.