Help with speaker subwoofer design - AVS | Home Theater Discussions And Reviews
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post #1 of 510 Old 10-10-2013, 09:31 PM - Thread Starter
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EDIT 1-5-14:

Hey guys welcome to the building page of the "Bass Cannon's" !!

The project really took off on its own direction and pretty much started with just a simple question. I had no idea what the end result would look like.

A special thanks to LTD02 and urapnes1 for all the time and input into the project!!

This is only a hobby so relax and enjoy the journey with me smile.gif









I really like the "marty sub" but it will not work for my application frown.gif

I need my subs behind my false wall and under my ATscreen so I want them to lay horizontal with two SI-18's per box and my JBL 3722N's will be sitting on top and in between the left center and right center I will have a JBL 4645C clone cabinet cut for me by a forum member.

Sorry for the crude picture but im not savy like some folks here....yet, lol redface.gif


My 2.35 screen will be above the subs. I'm thinking 48" wide x 24" x 24" gives me 16cuft - (8 per driver) would this be enough? what about the port?

http://www.hometheatershack.com/forums/ported-subwoofer-build-projects/69848-dual-ported-si-18s.html

This is a nice setup as well but not for my needs...I want front firing drivers.








Can anyone guide me here? I am going to send the plans over to be cut but I don't have a plan confused.gif

I have 16ft width in my room so I have plenty of room to work with but limited behind the wall.



Thanks in advance!!!

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post #2 of 510 Old 10-10-2013, 09:35 PM - Thread Starter
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I don't know why I have dual pictures but also keep in mind this is a rough sketch...not to scale.

My SI 18's have dual 4ohm VC so I will end up with a 4ohm load and if I will bridge to 1 EP4000 per cabinet.

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post #3 of 510 Old 10-10-2013, 10:21 PM - Thread Starter
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trying to figure this drawing stuff out smile.gif

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post #4 of 510 Old 10-10-2013, 10:52 PM
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I am thinking you will have roughly 13 cubic feet within each after you account for wood thickness and a double-thick front baffle. Tune nice and low 15-17 hz and rock on cool.gif
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post #5 of 510 Old 10-10-2013, 11:09 PM - Thread Starter
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biggrin.gif looking like the real thing...this is closer to scale

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post #6 of 510 Old 10-10-2013, 11:10 PM - Thread Starter
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Thanks Joel!!

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post #7 of 510 Old 10-11-2013, 12:41 AM
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if you can get the subwoofer drivers to roughly the quarter distances from the ceiling and the floor, you can kill lots of room modes.

not to scale:


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post #8 of 510 Old 10-11-2013, 12:54 AM
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Since you have a false wall, you have a possible advantage, external port. This probably the path i'm heading down myself shortly.

I must be guilty because people say I am guilty because they chose to call me guilty because they refuse to see the truth. Much easier to be part of the mob..
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post #9 of 510 Old 10-11-2013, 02:48 AM - Thread Starter
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LTD02, I was hoping you would chime in! So in the scenario you have there, I have the space, but which ones should be the sub bass SI-18's and which ones the 4645clone?

Im thinking the two flanking the center should be SI-18's?

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post #10 of 510 Old 10-11-2013, 02:49 AM - Thread Starter
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Trep, external port?

Thanks guys for the input!!

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post #11 of 510 Old 10-11-2013, 05:18 AM
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Quote:
Originally Posted by 316 View Post

Trep, external port?

Thanks guys for the input!!

Probably not my best explanation. The "tube" (vent) for a ported sub-woofer does not have to be inside the cabinet. It is just a tube which connects to the primary volume of the cabinet and releases it to the world via a constrained space. People tend to put them inside because it looks pretty/elegant/sexy/blahblahblah. However, by putting them inside you run into a host of issue of what you designed is probably not what you will get. Having it external allows you to easily tune but also give you a smaller box. the biggest negative is you now have a "chimney" on your box. Just a thought.

I must be guilty because people say I am guilty because they chose to call me guilty because they refuse to see the truth. Much easier to be part of the mob..
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post #12 of 510 Old 10-11-2013, 06:54 AM - Thread Starter
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Oh, okay so a literal external port...ok. yeah that would be different for sure.

My main concern at this point is since this is my first AT screen, how much effect the woofers will have on my screen....I do not want to see any movement which is why I kinda placed the speakers horizontal. However, if it is not an issue would it benefit me to make the cabinets 6' tall and gain cuft and getting the drivers up higher?

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post #13 of 510 Old 10-11-2013, 07:00 AM - Thread Starter
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post #14 of 510 Old 10-11-2013, 07:19 AM - Thread Starter
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Okay guys- boxes for my SI 18's, the way I see it I have 3 options:

48" tall 24" wide by 24" deep single driver 16cuft
36" tall 24" wide x 24" deep single driver 12cuft

72" x 24"x24" two per box 24cuft

Cuft not including bracing/driver.

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post #15 of 510 Old 10-11-2013, 10:20 AM - Thread Starter
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I'm only going to do this setup once so I want to get it right and be done with it smile.gif

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post #16 of 510 Old 10-11-2013, 10:30 AM
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How many SI18's will you have? I think that the verticle duel driver enclosures would be great if you could do two of them on the front wall facing forward.
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post #17 of 510 Old 10-11-2013, 10:40 AM - Thread Starter
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Hi, I currently have 4 SI drivers, and plan on 3 2242's. I really wanted 4 2242's all along but 3 is cool and it looks good ...thanks to LTD02 smile.gif always great insight!

I like the towers myself too ..

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post #18 of 510 Old 10-11-2013, 01:30 PM
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316 I'm in a similar dilemma. I've got 8) SIs, 2)FTW 21s, and 3)2242s. So far I haven't figured out how to get the 2242s in the mix in terms of space.
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post #19 of 510 Old 10-11-2013, 03:11 PM - Thread Starter
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eek.gif Well seein as how I have not purchased my 2242's yet and I need 3, and you're struggling whit there to put your three.....hmmm...tongue.gif

Wow, 8 and two 21's plus 3 2242's! eek.gif Man I bet that's gonna sound good!

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post #20 of 510 Old 10-11-2013, 03:54 PM
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"LTD02, I was hoping you would chime in! So in the scenario you have there, I have the space, but which ones should be the sub bass SI-18's and which ones the 4645clone?

Im thinking the two flanking the center should be SI-18's?"

yeah...si's in gray in that pic. no particular design, just roughly idea for placement. since they will cover the bass region where the room modes are sticking them in the 1/4 distance positions is where they will have the most benefit.

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post #21 of 510 Old 10-11-2013, 03:56 PM
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"I'm only going to do this setup once so I want to get it right and be done with it"

do you have 2 feet deep behind the screen or more or less?

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post #22 of 510 Old 10-11-2013, 04:02 PM
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if you don't have space constraints, it would be very easy to build something that would fit in between the center and the mains.

big, slot loaded, ported cab. vertical standing. large slot upward facing.

placement of drivers can be such that they end up in the 1/4 distance from the floor and 1/4 distance from the ceiling even if not symmetrical on the cab itself.

three drivers could also be used if you want to get even more crazy. :-)



now, there is a wild optical illusion.

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post #23 of 510 Old 10-11-2013, 04:14 PM - Thread Starter
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LTD02, you da man!! WOW man that's cool!! I love the idea of the slot at the top and was also thinking of the potential for a third driver at some point....basicly that's like a delayed completion rather than a total redo, lol.

I love it!!

I have as much room as I need but want to keep it around 2-4 feet but I also want to place my gear back there

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post #24 of 510 Old 10-11-2013, 04:24 PM
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yeah...they are pretty cool. :-)


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post #25 of 510 Old 10-11-2013, 04:29 PM
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since you are running one driver per amp channel, just get an additional 2 drivers and 1 amp.

dual4 ohm drivers give 2 ohms per channel. that is good on an ep4000 or inuke 3000dsp. either way about 1000 watts per sub.

at 2 feet x 2 feet x about 7-8 feet tall, that will net somewhere around 8.5 +/- cubic feet per driver which is good. a tune of around 16hz would be easy with that big slot.

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post #26 of 510 Old 10-11-2013, 04:39 PM
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1000 watts on each driver drives them to 20mm or so. 128db at 16hz before room gain. yeah...that should do it. :-)


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post #27 of 510 Old 10-11-2013, 04:58 PM - Thread Starter
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Okay guys, the plan is set and in motion! Here is what I would like to do, since I have no height restraints and I know that at some point in time the upgraditis bug will hit, I want to build full sheet length kick-a$$ subs and they shall be called...drim roll please... "Bass Cannon"... Okay, so I'm taking andvantage of my last name, lol.

8' tall by 24" x 24"

For starters I will run two subs per cabinet at 1/4 spaces as LTD02 described and I am going to have my cabinet builder engrave an outline for two more subs per cabinet so I can jigsaw the holes at a later date and drop in more drivers.

Question: slot port, what should the dimensions be?

You heard of the "Marty sub" now its time for the "Bass Cannon" lol...tongue.gif

BTW, I've always marveled at the VMPS monsters from years ago, now I'm going to make my own monsters!! biggrin.gifeek.gifwink.gif

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post #28 of 510 Old 10-11-2013, 05:01 PM - Thread Starter
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LTD02, you are a genius....I was just getting off the phone with my builder Joel and came to this conclusion, start posting my decision, and BAM.....you're already there!! Dang!!

I would have about 6" from the ceiling, would the top firing slot have any issues with that?

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post #29 of 510 Old 10-11-2013, 05:39 PM
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VERY cool renderings LTD02. 316 you should be in for a real treat when it's all done. If I decide to stop clutching my 2242s I'll letcha know.
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post #30 of 510 Old 10-11-2013, 06:29 PM
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well...at 2'x2'x8' and using 0.75" wall thickness and roughly that same amount of material for the slot, bracing and so forth; and then subtracting off roughly 0.75 for three drivers and subtracting off for the port gives something in the ball park of 23 cubic feet net.

one slot port with a little over 20% adjustment factor (whatever the source of the adjustment!) bring it in at a nice round 6" x 21" x 36" long for about a 16hz tuning.

port velocity with 3 drivers and 1000 watts per driver (3000 watts total) is only 15ms at 20hz, so pretty low velocity.

cab is huge so will have resonance if not stuff, but a couple pillows from wally mart will help with that.

response, no room gain, 1 cab only, 3 drivers, 3000 watts


cone excursion


port velocity


[ignore the port length value, apparently winisd gets this wrong for slotted ports and maybe some other ports]

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