Solid Hardwood Ultimax Subwoofer Build - (Bombelsub) - AVS Forum
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Old 02-20-2014, 11:35 PM - Thread Starter
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Hi guys !
This will be my first build-post in this forum.
I've chosen a nice Dayton Ultimax 15" subwoofer, which I got from PE.

I needed a box for it, but did not want to go with MDF, so came the idea to make it from hardwood, which is available where I'm from (South-America).
I read about the pros and cons of using solid wood, and will explain these also.

I am using a Behringer iNuke NU3000DSP amplifier to feed this puppy.

The Ultimax driver will be mounted in the rear of the baffle, and I am using 2x 4" "dimpled" Precision Ports.

Size: W52cm, H68cm, D75cm.
Internal volume: 262 liters / 9.25 cu ft.
Wall thickness: 22mm
Baffle thickness: 42mm
Corner bracing: 4x4cm

Do let me know your opinion and/or experience on the use of this particular subwoofer driver and the use of solid wood for the enclosure.

(more info about the build progress will be added in a few)

First drawings dated: feb 6th 2014







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Old 02-21-2014, 12:14 AM
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make a mdf or plywood box and then build the solid wood box around it. also u will need to brace the box. look at other builds for how to do it.
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Old 02-21-2014, 12:21 AM - Thread Starter
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thanks for your input cookie.
I did have bracing planned and drawn, but at this point have decided not to use it yet.
As 1 side will be accessable with screws, I can always add bracing if I think it's needed.
I will add this bracing of there is more wall vibration than I think is acceptable for this size sub.
The wood used is VERY hard, VERY heavy and has a much higher tensile strength when compared to either mdf or plywood... cool.gif

As for using mdf as an inner box, what would this bennefit ?

attached a pic of the cut hardwood, dated feb 14 2014...
For esthetics, I used several different types of wood, but most of the wood used is "Basralocus" (http://www.tropicalmarinetimbers.com/basralocus/index.html)
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Old 02-21-2014, 12:59 AM
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I agree with the above.
Build out of MDF.
Then wrap that with a nice 1/4" or 1/8" of your hardwood, which looks great btw.
Here is a few pics to give you an idea about internal bracing, which you're going to need. The sides/top/bottom will all flex.

https://www.google.com/search?q=subwoofer+enclosure+bracing&num=50&espv=210&es_sm=122&source=lnms&tbm=isch&sa=X&ei=DQcHU9f1Ccr22QX--IGwDA&ved=0CAkQ_AUoAQ&biw=1280&bih=595

How did you come about the size required for your build?

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Old 02-21-2014, 01:07 AM - Thread Starter
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hi guys, Thanks for your feedback... I added a reply, but I see it got removed for having an external link :/

regarding dimensions: the height and depth were determined by the cabinet it will be placed under (70cm high, 75cm deep)
I was a bit flexible with the width, I used 52cm, based on a ~9cu ft net volume.

I had the bracing planned and drawn, but decided not to add it yet.
The wood i am using is VERY heavy and VERY hard. It does not flex/vibrate.
I use several types of hardwood, most are called "basralocus".
This wood had a VERY high tensile strength.

I know about cabinet bracing, and I know what purpose it serves. smile.gif
IF at a later point I do need bracing, this can be added, as the baffle and the top of the enclosure will be screwed to the frame.

What would be the benefit of using an internal box made out of mdf or plywood ?

Attached, pic of individual pieces of wood. Dated feb 14 2014.
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Old 02-21-2014, 01:24 AM - Thread Starter
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My Behringer NU3000DSP got too loud for comfort...
Luckily I read about this and had also ordered a Noctua NF-R8, which I used to replace the stock fan. This is an excellent mod ! From where I sit, I cannot hear the fan noise anymore !!

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Old 02-21-2014, 05:43 AM
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Old 02-21-2014, 06:40 AM
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Originally Posted by Bombelman View Post

What would be the benefit of using an internal box made out of mdf or plywood ?
The natural expansion and contraction of wood with changes in humidity will eventually fracture the glue joints and it will no longer be airtight. Furniture builders know this, and they use building techniques that allow for this expansion and contraction to occur, but those techniques won't allow the box to be airtight.

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Old 02-21-2014, 10:08 AM - Thread Starter
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Quote:
Originally Posted by Bill Fitzmaurice View Post

The natural expansion and contraction of wood with changes in humidity will eventually fracture the glue joints and it will no longer be airtight. Furniture builders know this, and they use building techniques that allow for this expansion and contraction to occur, but those techniques won't allow the box to be airtight.

Hi guys, thanks for the input.
I know about the natural expansion and contraction of certain woods.
And it is not without certain guarantees I set forward with this project.

This cabinet is being made by a local experienced furniture company/workshop.
I have been speaking to the owner and woodworker and both assured me this cabinet will stay leak free,
or else I will be refunded.
I told them this peace of furniture should survive my kids and grandkids... biggrin.gif

anyhow, the inspiration to use local hardwood came from furniture in my home, both indoor and outdoor, which is older than myself, and has yet to develop a single tear or crack (knocks on wood, hehe) I can take some pictures of this >30yr old furniture and post these later.

Don't get me wrong, I am not trying to defend myself here, or underestimating anyone's knowledge or experience. I myself am also concerned about the shape and seal of the enclosure.
But hey, you can't succeed without havin tried, right ?
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Old 02-21-2014, 10:11 AM - Thread Starter
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Here is a close-up picture of how the individual pieces are joined together.

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Old 02-21-2014, 10:13 AM
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As someone who has built speakers with veneer over MDF, 1/8" hardwood over MDF, and 3/4" thick solid hardwood panels, I can say this with confidence. The hardwood will look amazing. But it'll just be a matter of time before you get splitting or cupping with split seams. Solid hard wood is not dimensionally stable, and that is a major reason why you don't see it on commercial products.
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Old 02-21-2014, 10:16 AM
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You always have the option of building over 1/2 ply or MDF. It would add to the weight of course but we see it done all the time. I'm hoping it works out for you though.

EDIT> Anthony your always one step ahead of me. smile.gif lol

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Old 02-21-2014, 10:21 AM - Thread Starter
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Quote:
Originally Posted by Anthony_Gomez View Post

As someone who has built speakers with veneer over MDF, 1/8" hardwood over MDF, and 3/4" thick solid hardwood panels, I can say this with confidence. The hardwood will look amazing. But it'll just be a matter of time before you get splitting or cupping with split seams. Solid hard wood is not dimensionally stable, and that is a major reason why you don't see it on commercial products.

The walls are not 1 solid piece, but strips of different types of hardwood available. (5 in total, iirc)
They are also glued together. Panel thicknes 22mm, baffle thicknes 42mm.

I will make an enclosure from hardwood. Without mdf lining the inside, or with mdf as suggested. But not before I have seen how this works out first.

Anthony, would glueing the mdf to the hardwood be sufficient to keep the hardwood in place ?

edit: thanks for your reply steve.
if you have any links to share, i would love to see these.
For me, weight would not be an issue,

Attached picture of one of the finished panels, before assembly...

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Old 02-21-2014, 10:25 AM
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The best luck I had with hardwood was 1/8" hardwood directly bonded to MDF. My sub has this on the surface and it has held for the past decade with some creep, but nothing too terrible When I did solid 3/4, it was fine for several years, but eventually buckled enough to matter. This was with multiple laminated boards with alternating cupping. If temperature and humidity are more stable where you live, you might be luckier than I was. Good luck! I'm sure what you have built will be beautiful and will be fine for many years. I'm just not confident how many years before you run into issues (not 100% certainty, but a reasonable chance)
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Old 02-21-2014, 10:26 AM
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Originally Posted by steve nn View Post

EDIT> Anthony your always one step ahead of me. smile.gif lol

I can read minds!!! :P Or...I'll chalk it up to great minds think alike, but some are faster on the keyboard :-D
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Old 02-21-2014, 10:29 AM
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^^^ Well, you're admittedly quicker, I have no problem with that. TWISH +

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Old 02-21-2014, 10:31 AM - Thread Starter
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Quote:
Originally Posted by Anthony_Gomez View Post

The best luck I had with hardwood was 1/8" hardwood directly bonded to MDF. My sub has this on the surface and it has held for the past decade with some creep, but nothing too terrible When I did solid 3/4, it was fine for several years, but eventually buckled enough to matter. This was with multiple laminated boards with alternating cupping. If temperature and humidity are more stable where you live, you might be luckier than I was. Good luck! I'm sure what you have built will be beautiful and will be fine for many years. I'm just not confident how many years before you run into issues (not 100% certainty, but a reasonable chance)

Relative humidity around 90%, temperature average around 30 degrees Celcius. It's summer all year long here in the tropics :-)
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Old 02-21-2014, 10:32 AM
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A floating baffle made of solid hardwood may be fine, otherwise I would stick with veneer or another finish.

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Old 02-21-2014, 10:33 AM
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My log home has hickory 3/4" planks exactly like this.
I can say with confidence as humidity changes you WILL have cracks/leaks develop.
100% guaranteed.

If you choose not to listen to those who have said so, based on their real experience, that is your choice.
Heck, coat the inside with some of that roll on bedliner stuff, maybe that will keep your pressure vessel from leaking when some cracks form, just a thought.
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Old 02-21-2014, 10:41 AM - Thread Starter
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A floating baffle made of solid hardwood may be fine, otherwise I would stick with veneer or another finish.

what is his "floating baffle" you speak of ? smile.gif
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Old 02-21-2014, 10:43 AM
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The Ultimax driver will be mounted in the rear of the baffle, and I am using 2x 4" "dimpled" Precision Ports.

What tune are you planning with this bad-boy enclosure?

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Old 02-21-2014, 10:59 AM
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btw nice avatar....... cool.gif

Agreed. smile.gif
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Old 02-21-2014, 11:06 AM
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+1 on the MDF box as the base box.

MDF is cheap and easy to work with. Why risk it and go to all of the trouble building if there is even a small chance the wood will warp or split?

That hardwood is indeed beautiful! Best of luck with your build.

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Old 02-21-2014, 11:20 AM
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Bombleman, I know it may seem like everyone is shooting down your idea but we really are not. I am one that likes things different and I have tried all the things others have as well. If you where doing front speakers or a center channel that might be ok since there is not as much pressure being put on the wood by a subwoofer. Please remember that these 15" subwoofers have been know to produce enough bass that the box will actually crawl a few inches. I agree that it will look beautiful but why waste all that work and money to have it leak in a few years or sooner if the work is not done right. Make a simple mdf box and then cover it. It will look amazing and last a very long time. Go ahead and spend the extra hour or so and brace it now. It doesn't hurt it if its in there. Also the one thing no-one has touched on is these panels you are talking about being removeable? How are they going to seal? Weather stripping?

Its tough, when building my sub box this last month or so I sent over probably 10 different ideas to one of the members here and he kept either shooting them down or telling me what was wrong with them. I finally went with MDF and as right now I couldn't be happier. This thing is a tank and will outlast me and the driver inside it.
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Old 02-21-2014, 12:19 PM
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This cabinet is being made by a local experienced furniture company/workshop.
FWIW some of the worst results of speakers built from my plans were realized by professional woodworkers who decided to ignore the instructions 'because I know what I'm doing'. With respect to chairs and dressers, maybe. But a speaker is not a chair.
Your panels won't have a problem. Where the panels join will, because the expansion rate across the grain and with the grain isn't the same, and with a box there are joints where with the grain and across the grain will meet.
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Old 02-21-2014, 12:23 PM
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Old 02-21-2014, 12:24 PM - Thread Starter
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I asked for an opinion, so I don't consider being "shot down". I respect all views.
Money is not a huge issue, and it's not that I don't want to listen: the use of mdf in this build can still happen,
however, the build is >90% done haha, these guys are fast....
All walls but the top and baffle have been glued and screwed since yesterday... biggrin.gif

I will attach some pics. Do tell me if you think glueing mdf panels to the inside will result in longer lifetime ?
(Or should I start all over)

These pics were taken a few minutes ago...


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Old 02-21-2014, 01:11 PM - Thread Starter
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Quote:
Originally Posted by steve nn View Post

What tune are you planning with this bad-boy enclosure?

iirc about 19Hz, calculated with 9cu ft internal volume,
and the 2x 4" Dimpled precision ports, at their full length.

(do correct me if i have made an error. baffle will not be cut till monday)
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Old 02-21-2014, 01:43 PM
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I will attach some pics. Do tell me if you think glueing mdf panels to the inside will result in longer lifetime ?
No, because the expansion and contraction of that thickness of wood will also cause it to separate from the MDF. That's why veneer isn't made thick, so that the adhesive bond to the substrate is stronger than the expansion and contraction forces of the veneer layer.

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Old 02-21-2014, 02:06 PM - Thread Starter
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Quote:
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No, because the expansion and contraction of that thickness of wood will also cause it to separate from the MDF. That's why veneer isn't made thick, so that the adhesive bond to the substrate is stronger than the expansion and contraction forces of the veneer layer.
mdf+glue+screws ? tongue.gif or just write it off in a few months/yrs from now and start over...?
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