MFW-15 Project Advice Needed - Page 2 - AVS Forum
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post #31 of 100 Old 04-16-2011, 02:12 PM
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Quote:
Originally Posted by smokarz View Post

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?

a well braced 3/4" mdf 3 cubic footer will come in around 50 pounds or so before adding the driver. that is fine.

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Originally Posted by smokarz View Post

"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

our friend bill fitzmaurice introduced us to a product call pl premium. it appears that there is now a pl premium advanced. pl premium is very strong, but more important it expands to fill in any air gaps. it comes in a tube that you put in a caulking gun.

http://www.loctiteproducts.com/p/pl_...n-Adhesive.htm
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post #32 of 100 Old 04-16-2011, 03:03 PM
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thanks, already got a couple of tubes of PL Prem.

have any idea how much a sheet of 4'x8' 3/4" MDF weight?

if it weights more than 100lb, then perhaps my box with half of the sheet might come in at 50lb.
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post #33 of 100 Old 04-16-2011, 04:09 PM
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it will vary but roughly 100 lbs for a 4 x 8 sheet of 3/4 mdf is in the ballpark.

you are good on weight. if it seems like it is 'heavy', that is about right.

pl is the way to go. you have done your homework. nice. ;-)

don't work with that mdf in a closed in room. drag it outside for good ventilation while you chop it up. the chemicals are no good for your lungs.

you guys should be ready to build. ...just no air leaks!

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post #34 of 100 Old 04-16-2011, 06:17 PM - Thread Starter
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Thanks for the tips LTD02. For the bracing, would it be sufficient to use scraps from the 3/4" MDF? I'm just wondering if the 3/4" edge would provide enough surface area to give a good bond.

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post #35 of 100 Old 04-16-2011, 06:35 PM
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Using your MDF scraps will work fine. Even though you're using butt joints, they'll work fine so long as everything fits together nicely.

YID DIY
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post #36 of 100 Old 04-16-2011, 06:43 PM
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"Using your MDF scraps will work fine. Even though you're using butt joints, they'll work fine so long as everything fits together nicely."

+1.

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post #37 of 100 Old 04-16-2011, 07:10 PM
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brace, brace, brace, brace, brace..........ect. and when in question BRACE YO SELF!

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post #38 of 100 Old 04-16-2011, 07:17 PM
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i'll give that a +1, but mostly because the first line of NH's sig is my favorite. ;-)

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post #39 of 100 Old 04-18-2011, 07:10 AM - Thread Starter
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I figured since I'll be making these myself I should at least do something interesting with the cabinet, so here's what I came up with:



I would probably do this by just cutting out the outline on a second piece of MDF and chamfering it before attaching to the main baffle.

Would something like this have any affect on the sound?

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post #40 of 100 Old 04-18-2011, 12:40 PM
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Quote:
Originally Posted by Scott C. View Post

I figured since I'll be making these myself I should at least do something interesting with the cabinet, so here's what I came up with:



I would probably do this by just cutting out the outline on a second piece of MDF and chamfering it before attaching to the main baffle.

Would something like this have any affect on the sound?

Not for low frequencies.....

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post #41 of 100 Old 04-27-2011, 02:40 PM - Thread Starter
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Can anyone who has an MFW-15 on hand tell me what size screws it needs for mounting?

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post #42 of 100 Old 04-27-2011, 03:03 PM
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I used 1" 10-32 buttonhead screws and hurricane nuts.

Wem
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post #43 of 100 Old 04-27-2011, 03:28 PM
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Quote:
Originally Posted by Fatshaft View Post

Here's my approx. 3cuft boxes I just finshed building.


How did you get the hole diameter for the MFW15 driver? Is 13 13/16 the actual cutout?
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post #44 of 100 Old 04-27-2011, 07:48 PM
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Quote:
Originally Posted by wembley2000 View Post

I used 1" 10-32 buttonhead screws and hurricane nuts.

Wem

this is exactly what i get, per Wem's input.
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post #45 of 100 Old 04-27-2011, 07:49 PM
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Quote:
Originally Posted by diaz View Post

How did you get the hole diameter for the MFW15 driver? Is 13 13/16 the actual cutout?

it is 13 15/16"
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post #46 of 100 Old 04-28-2011, 05:56 AM
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*delete

oops sorry thought I was on page one and was on two..... Darn iPhone app stinks!

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post #47 of 100 Old 04-28-2011, 07:03 AM
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To the OP, I think you are on the right path with 2 single driver sealed boxes. Your room is very small and you indicate that listen at slightly lower levels. If for some reason you find the output lacking, you can always scrap the sealed boxes and make MFW-15 box clones which are ported and tuned to the upper teens I believe. I'd suggest not making them look pretty (paint, veneer etc) until you test them in your room.

I would suggest placing one in a corner to maximize the boundary effect mentioned by LTD. Then try the 2nd sub in as many feasible locations as you can find to try to smooth the response. Having some ability to take measurements would be nice as would some basic EQ.

Bracing a box this small won't be very involved. Use 2-3" wide scraps and connect panel to panel where you can. Sand to fit and then glue/nail/screw. If you don't end up with enough scrap, just buy a couple of 1" oak dowels from your lumber yard for the remaining bracing.

Good luck and be safe while cutting the MDF.
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post #48 of 100 Old 04-28-2011, 07:57 AM
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where is everyone getting MFW-15s? I thought av123 closed down last year...
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post #49 of 100 Old 04-28-2011, 08:37 AM
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There are two guys who bought a bunch of the leftover drivers from the manufacturer. One is GR Research ask for Danny as it is not on the web site and the other DIY Sound group http://www.diysoundgroup.com/ aka Erich H.

There are a few hundred being liquidated. Once they are gone it remains to be seen what would replace them for projects being designed around the driver.
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post #50 of 100 Old 04-28-2011, 09:23 AM
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Quote:
Originally Posted by BIGmouthinDC View Post
There are two guys who bought a bunch of the leftover drivers from the manufacturer. One is GR Research ask for Danny as it is not on the web site and the other DIY Sound group http://www.diysoundgroup.com/ aka Eric.

There are a few hundred being liquidated. Once they are gone it remains to be seen what would replace them for projects being designed around the driver.
I thought there was a Dayton driver that matched pretty closely, no?

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post #51 of 100 Old 04-28-2011, 10:15 AM
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Quote:
Originally Posted by pgwalsh View Post
I thought there was a Dayton driver that matched pretty closely, no?
The Dayton DVC is similar but sells for around $160. It might be possible for someone to commission Eminence to build the MFW woofers by the batch. Obviously someone would have to make a business case for it.
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post #52 of 100 Old 04-28-2011, 10:52 AM - Thread Starter
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Thanks for the help. I'll definitely try them out in the room before making any significant investment in finishing. I do have the capability to do some REW measurements. EQ might happen a little later, but for the time being I'll just try to optimize the placement.

You said that bracing wouldn't be much of an issue with a box this size, but what does that mean in terms of a double baffle? Would you recommend them?

Quote:
Originally Posted by coctostan View Post
To the OP, I think you are on the right path with 2 single driver sealed boxes. Your room is very small and you indicate that listen at slightly lower levels. If for some reason you find the output lacking, you can always scrap the sealed boxes and make MFW-15 box clones which are ported and tuned to the upper teens I believe. I'd suggest not making them look pretty (paint, veneer etc) until you test them in your room.

I would suggest placing one in a corner to maximize the boundary effect mentioned by LTD. Then try the 2nd sub in as many feasible locations as you can find to try to smooth the response. Having some ability to take measurements would be nice as would some basic EQ.

Bracing a box this small won't be very involved. Use 2-3" wide scraps and connect panel to panel where you can. Sand to fit and then glue/nail/screw. If you don't end up with enough scrap, just buy a couple of 1" oak dowels from your lumber yard for the remaining bracing.

Good luck and be safe while cutting the MDF.

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

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post #53 of 100 Old 04-28-2011, 11:45 AM
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Quote:
Originally Posted by Scott C. View Post

Thanks for the help. I'll definitely try them out in the room before making any significant investment in finishing. I do have the capability to do some REW measurements. EQ might happen a little later, but for the time being I'll just try to optimize the placement.

You said that bracing wouldn't be much of an issue with a box this size, but what does that mean in terms of a double baffle? Would you recommend them?

If your receiver has eq like Audyssey or MCACC, that might be adequate. The only issue you might run into is a phase issue if one sub is much closer to you than the other.

I don't think double baffle is particularly important but it does allow you to recess the driver if you prefer that look. It is also very easy to do so most do it. I haven't seen anything that quantified the effect of a thicker baffle.
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post #54 of 100 Old 04-28-2011, 12:24 PM
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Quote:
Originally Posted by coctostan View Post

The Dayton DVC is similar but sells for around $160. It might be possible for someone to commission Eminence to build the MFW woofers by the batch. Obviously someone would have to make a business case for it.


I did that when I picked up the pallets. They will make them for us, but the price would be over $77. I think he said $110 - $120? I can't recall and it depended on how many were purchased, but it was around there. I could find out once the stocks get lower.
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post #55 of 100 Old 04-28-2011, 12:28 PM
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Quote:
Originally Posted by gtu2004 View Post

where is everyone getting MFW-15s? I thought av123 closed down last year...

Danny at GR Research bought about 200 or so from the bankruptcy sale.

By chance I found out that the original manufacturer actually had some sitting in their warehouse, so I was able to get those.
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post #56 of 100 Old 04-28-2011, 12:44 PM
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Quote:
Originally Posted by Erich H View Post
I did that when I picked up the pallets. They will make them for us, but the price would be over $77. I think he said $110 - $120? I can't recall and it depended on how many were purchased, but it was around there. I could find out once the stocks get lower.
It might not be worth it at that price point. It is a nice driver but nothing special. It is just the value at the current price is off the charts.
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post #57 of 100 Old 04-28-2011, 12:46 PM
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Originally Posted by coctostan View Post


If your receiver has eq like Audyssey or MCACC, that might be adequate. The only issue you might run into is a phase issue if one sub is much closer to you than the other.

I don't think double baffle is particularly important but it does allow you to recess the driver if you prefer that look. It is also very easy to do so most do it. I haven't seen anything that quantified the effect of a thicker baffle.

if your butt jointing it gives 1.5" surface area instead of .75 to hold the baffle on........ FWIW. I personally would not consider a sub enclosure without one, but maybe not necessary.......

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post #58 of 100 Old 04-28-2011, 01:13 PM - Thread Starter
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Originally Posted by NicksHitachi View Post

if your butt jointing it gives 1.5" surface area instead of .75 to hold the baffle on........ FWIW. I personally would not consider a sub enclosure without one, but maybe not necessary.......

A lot of the double baffles I've seen around here just seem to be two sheets laminated together and glued to the front like a single baffle which would still just be 3/4" wide. Do you suggest cutting the innermost baffle smaller so it rests "inside" the box?

Also, for recessing with a double baffle, would it be better to do the separate cutouts before gluing the sheets together?

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post #59 of 100 Old 04-28-2011, 01:21 PM
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Quote:
Originally Posted by Scott C. View Post


A lot of the double baffles I've seen around here just seem to be two sheets laminated together and glued to the front like a single baffle which would still just be 3/4" wide. Do you suggest cutting the innermost baffle smaller so it rests "inside" the box?

Also, for recessing with a double baffle, would it be better to do the separate cutouts before gluing the sheets together?

not sure what's best or proper, but that's what I did....... then face nail/screw into the double baffle If you wish.

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post #60 of 100 Old 04-28-2011, 01:48 PM
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I speak only for baltic birch plywood:

Once you make a cutout on a 3/4" sheet, its all the thickness you'll need for a speaker up to several thousand watts. But since you also want to cut down on resonance, it would be preferable to add a sheet to double up the baffle thickness. If you make a larger cutout on the front baffle, you are not loosing any integrity of the baffle as long as the cutout is near flush to the edge of the speaker. This is how I make most enclosures - inner diameter cutout, followed by an outer diameter cutout. Speaker mounts flush and recessed a little. Looks nice and clean in the end.

The beauty of it is you can add alot of birch and it wont be near as heavy as MDF. Plywood is super stiff and as long as you have proper braces, it will not absorb very much sound - it projects decibels out very efficiently. This can be unwanted in some cases, but once I started working with birch plywood, I can never go back to MDF.
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