MFW-15 Project Advice Needed - AVS Forum
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post #1 of 100 Old 04-12-2011, 11:38 AM - Thread Starter
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I'm looking to work on a new sub project, and with the MFW-15's available at such a great price, I thought I'd take advantage of that. I just bought a Behringer EP1500 to power the sub(s), and now I'm in the process of deciding what kind of enclosure to build.

My room is about 1500cuft, and I use it for about 80/20 HT/Music. I'm looking to go with 2 drivers (although I'll get away with 1 if I can). The type of subs I'm looking at are, 2 sealed, 1 dual opposed, or 1-2 ported. I like the idea of sealed to make the box construction a bit simpler, and not to have to worry about a high pass filter (hopefully), but if there's enough of a case for a ported alignment I wouldn't have a problem investing in a Minidsp or BFD (I'll probably get one down the line anyway).

Budget is fairly simple. I've already got power, and I'm planning on about $180-190 for the drivers. I'd like to keep material costs under $100, which I don't think should be too much of an issue.

It's a fairly small space, so I don't exactly have room for something like the THT. I listen at about 10-20 below reference, so crazy SPL isn't a priority, although I would like to maintain decent levels when I eventually move to a larger space. Based on my situation, which of the possible choices I listed above would serve me the best? Or would something else entirely be better? I'm open to suggestions.

Sounds Good to Me... keeping track of my audio projects.

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post #2 of 100 Old 04-12-2011, 11:43 AM
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i am getting ready to build 2 single sealed MFW-15s.

simple build, and smaller footprint. my room is about 1900cf.

and i just picked up an EP2500.
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post #3 of 100 Old 04-12-2011, 11:53 AM
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I just got 4 of the MFW-15's to augment my current SVS subs. The room is about 2500cf.

I was thinking of going with either 4 single sealed subs or 2 dual opposing sealed subs. The single sealed is the easiest to build and would give me more placement flexibility. The dual opposing seems like a popular configuration though, not sure of the benefits over a single sealed though.

I am getting a EP4000 to power them.
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post #4 of 100 Old 04-12-2011, 12:01 PM
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I'm pondering a 4 sealed configuration with the yet to be finalized amp that Mark Seaton and friends are optimizing for such a project.
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post #5 of 100 Old 04-12-2011, 12:07 PM
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I'm leaning towards four single sealed cabinets and one of the Seaton/MotorCity modified SA1000 amps.

I need to get rid of my two working MFWs and SVS 12/2+ but need to find local homes as I really don't want to ship em. I don't want to mix and match ported with sealed.
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post #6 of 100 Old 04-12-2011, 02:26 PM
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I just about finshed 4x 3cuft sealed MFW-15 cabs.
I placed 1 cab in each corner of my HT room (11.8 x17.7)
I'm driving them with an EP4000 in bridged mode at 4 ohms total load.

I'm just now trying all kinds of music and movies to see what it gives.
When cranking the volume...it pounds!!!

I will be putting a build blog up soon.

Today I purchased 4 pillows at Walmart and ripped them open and stuffed one per cab.
I will get 4 more pillows and stuff 1 per cab more. There's room for 2 pillows per cab.
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post #7 of 100 Old 04-12-2011, 03:30 PM - Thread Starter
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As much as I'd like to do 4, 2 is all I have room (or budget) for. What would be the benefits of dual opposed vs. 2 sealed? I like the idea of being able to spread out the 2 subs to even the response a bit, but would I be able to get better extension and/or SPL from a dual opposed setup?

I tried plugging some things into WinISD, and this is what I got. The grey line is a 6cuft ported box tuned to 15Hz (I just took what it initially gave me and changed the box size to 6cuft). Blue is a single 3cuft enclosure, and yellow is a 6cuft dual opposed. (sorry if the colors are a little hard to see)



It looks like the dual opposed is slightly flatter, but it really doesn't extend any further than the single sealed. Also note that there is a 15 Hz HPF on the ported.

Sounds Good to Me... keeping track of my audio projects.

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post #8 of 100 Old 04-12-2011, 04:23 PM
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The dual opposed models flatter because WinISD halves the Le when using 2 drivers, as would happen when drivers wired are in parallel. 2 single subs will have the same frequency response as a dual opposed in the same size cabinets. Dual opposed subs simply will have little box movement as the subs move in opposite directions and I think that's pretty much the only benefit. If you are using 2 drivers, I would go with 2 singles to help even FR around the room.
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post #9 of 100 Old 04-12-2011, 05:39 PM
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I also have 4 drivers and will build 4 x 2.5^3 boxes. I am waiting to see what mark and kevin develop amp wise before I purchase an amp since their amp is supposed to drive 4 of these drivers perfectly with 4 2.5 to 3 cubic boxes or dual opposed etc.

Eqpmt: Denon AVR-4520CI, EP 4000's, Sony BDP-S5100, Old Rear Projection DLP. 

Builds: Maelstrom 21 Ottoman Build, Dual Opposed MFW's x 2, Statements, SEOS-12/TD12M x 5. 

On Deck: TD6M's/SEOS Surrounds x 6, Finalists (maybe)

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post #10 of 100 Old 04-12-2011, 06:40 PM
 
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Quote:
Originally Posted by BIGmouthinDC View Post

I'm pondering a 4 sealed configuration with the yet to be finalized amp that Mark Seaton and friends are optimizing for such a project.

I was all hot to get four of these since they are so cheap and place all four up front in place of what I have now. Figuring my current displacement is equal to 7.5 of the MFW -15's, I think I am going to stay with what I have since what I have takes up less space in my small room. But man is it tempting.
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post #11 of 100 Old 04-12-2011, 07:00 PM
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Quote:
Originally Posted by mjg100 View Post

I was all hot to get four of these since they are so cheap and place all four up front in place of what I have now. Figuring my current displacement is equal to 7.5 of the MFW -15's, I think I am going to stay with what I have since what I have takes up less space in my small room. But man is it tempting.

I'm pairing mine with my mal 21. Should be nice.

Eqpmt: Denon AVR-4520CI, EP 4000's, Sony BDP-S5100, Old Rear Projection DLP. 

Builds: Maelstrom 21 Ottoman Build, Dual Opposed MFW's x 2, Statements, SEOS-12/TD12M x 5. 

On Deck: TD6M's/SEOS Surrounds x 6, Finalists (maybe)

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post #12 of 100 Old 04-13-2011, 05:08 AM
 
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Quote:
Originally Posted by smbsocal View Post
I just got 4 of the MFW-15's to augment my current SVS subs. The room is about 2500cf.

I was thinking of going with either 4 single sealed subs or 2 dual opposing sealed subs. The single sealed is the easiest to build and would give me more placement flexibility. The dual opposing seems like a popular configuration though, not sure of the benefits over a single sealed though.

I am getting a EP4000 to power them.
A dual opposed sub will be either 2 ohm or 8 ohm depending how you wire it. 2 ohm is hard for many amps to drive and 8 ohm means your amp has less power. You can do two dual opposed subs and wire them so that they represent a single 8 ohm load.
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post #13 of 100 Old 04-13-2011, 05:22 AM
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Quote:
Originally Posted by mjg100 View Post
A dual opposed sub will be either 2 ohm or 8 ohm depending how you wire it. 2 ohm is hard for many amps to drive and 8 ohm means your amp has less power. You can do two dual opposed subs and wire them so that they represent a single 8 ohm load.
I don't think that's possible unless you meant a 4 ohm load.
I have 4 single subs and cannot see how to get an 8 ohm load.

Maybe I can't see it.

Edit: I think you mean per cab...sorry
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post #14 of 100 Old 04-13-2011, 10:37 AM
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What kind of an amp are they considering? Is it a plate amp? Or a rack amp? I'm building dual opposed.
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post #15 of 100 Old 04-13-2011, 10:41 AM
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Quote:
Originally Posted by tjk002 View Post

What kind of an amp are they considering? Is it a plate amp? Or a rack amp? I'm building dual opposed.

Not a plate amp, I believed a rack amp. You can drive 4 MFW's with it in various configurations.

Eqpmt: Denon AVR-4520CI, EP 4000's, Sony BDP-S5100, Old Rear Projection DLP. 

Builds: Maelstrom 21 Ottoman Build, Dual Opposed MFW's x 2, Statements, SEOS-12/TD12M x 5. 

On Deck: TD6M's/SEOS Surrounds x 6, Finalists (maybe)

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post #16 of 100 Old 04-13-2011, 10:48 AM
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Quote:
Originally Posted by tjk002 View Post

What kind of an amp are they considering? Is it a plate amp? Or a rack amp? I'm building dual opposed.

A significantly modified/optimized SA-1000 as seen at Parts Express, similar to what we offer with the MFW Turbo kit and with the plate amps in the upgrade kits for the UFW-12.

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post #17 of 100 Old 04-13-2011, 11:27 AM
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Thanks for the response. I'm building the boxes without the drivers on hand, does anyone know what the cutout should be?
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post #18 of 100 Old 04-13-2011, 11:36 AM
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I've seen 13 13/16"or 13 7/8".
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post #19 of 100 Old 04-13-2011, 11:41 AM
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Driver cutout: 13 15/16"
Driver Outside: 15 1/4

Eqpmt: Denon AVR-4520CI, EP 4000's, Sony BDP-S5100, Old Rear Projection DLP. 

Builds: Maelstrom 21 Ottoman Build, Dual Opposed MFW's x 2, Statements, SEOS-12/TD12M x 5. 

On Deck: TD6M's/SEOS Surrounds x 6, Finalists (maybe)

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post #20 of 100 Old 04-14-2011, 01:01 PM
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Quote:
Originally Posted by Mark Seaton View Post

A significantly modified/optimized SA-1000 as seen at Parts Express, similar to what we offer with the MFW Turbo kit and with the plate amps in the upgrade kits for the UFW-12.

Mark,

Where can I order one of these amps? Are they available now?
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post #21 of 100 Old 04-14-2011, 01:18 PM
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Quote:
Originally Posted by tjk002 View Post

Mark,

Where can I order one of these amps? Are they available now?

We are still working out the last of the customizations. We have the response dialed in, and now we need to do some final testing with a full set of 4 drivers which we are currently building some boxes for. Sandbagger (Kevin) will be doing the modifications and offering them through Motor City Custom Audio. There is a sub forum on my user forum for MCCA where you can find some threads like this one showing the progress.

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post #22 of 100 Old 04-14-2011, 09:04 PM - Thread Starter
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At the moment I'm leaning toward 2 sealed at about 3cuft. My question now is about box construction.

Is it necessary to double the front baffle? Also, how extensive should the bracing be? Would some strips of MDF (8-9" wide) top/bottom, front/back, and side/side be sufficient?

Sounds Good to Me... keeping track of my audio projects.

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post #23 of 100 Old 04-15-2011, 06:56 AM
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i am also in the process of building 32 cf sealed boxes.

i won't be doing double baffle. i will have one piece of mdf with a big circle in the middle of the box for bracing.
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post #24 of 100 Old 04-15-2011, 08:47 AM
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Wembley has a PDF drawing of a single sealed box in his dual opposed MFW thread.
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post #25 of 100 Old 04-15-2011, 11:34 AM
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Here's my approx. 3cuft boxes I just finshed building.

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post #26 of 100 Old 04-15-2011, 07:33 PM - Thread Starter
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Another quick question. Supposing I want to end up at 3 cuft, and I'm planning on using some kind of stuffing, should I still build it so it has an internal volume of 3 cuft? Or should I make it a little less since the stuffing supposedly increases the apparent volume?

Sounds Good to Me... keeping track of my audio projects.

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post #27 of 100 Old 04-16-2011, 11:57 AM - Thread Starter
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Sorry for the double post, but the modeling I've done in winISD makes me wonder about going the sealed route. I should have mentioned in the first post that I'd like to get usable output into the low 20's if possible. From winisd it seems like the only way to do that would be with a ported design. Is this actually the case? WinISD shows -3dB in the mid 30's for a 3cuft sealed box. Would room gain help it extend much more?

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post #28 of 100 Old 04-16-2011, 12:29 PM
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a lot here reccomeneded mutiple sealed boxes. that's what i am doing.

building 2 right now, and maybe 2 more if desire.
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post #29 of 100 Old 04-16-2011, 01:07 PM
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for folks modeling in winisd for the first time, one thing to keep in mind is that it is 2 pi space (i.e. as if you measured your subwoofer out in an open field).

in room, you will benefit from two effects. the first is boundary gain. this comes from the walls and ceiling. it changes 2 pi space into a much smaller space, so you get more spl.

the other effect is pressure vessel gain. this occurs when the long diagonal dimension of the room is less than about 1/2 wavelength. for medium sized rooms this occurs somewhere in the 25hz ballpark. below this point there is 12 db / octave of free gain, theoretically. in practice it is closer to 6-9db per octave. you will see this in how seaton will e.q. the subwoofer. it will appear to rolloff significantly in 2 pi space, but then will be pretty flat down to single digits in room.

so, again for the first time winisd guys, don't feel that you need to make your model flat in winisd to be flat in room. a -3db point in the twenties will provide a pretty flat response in a medium sized room.

the single driver per enclosure solution is good if you build your enclosures heavy. also, it is very important to get them sealed up. air leaks are the most common failure point that i've seen with these builds.

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post #30 of 100 Old 04-16-2011, 01:15 PM
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LTD02, thanks for the info for us new guys.

could you elaborate on this?

"the single driver per enclosure solution is good if you build your enclosures heavy"

what is your definition of heavy? how much does it need to weight? and isn't this limited by your enclosure size?

"it is very important to get them sealed up. air leaks are the most common failure point that i've seen with these builds."

how would you suggest sealing up the box? from what i've seen from the builds here, simply run glue inside along the edges/corners?

thanks
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