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Discussion Starter #1
I plan on building a 6.5 cu ft. slot port enclosure and I know its going to be heavy. so I'm tossing around the idea of using Plywood instead of MDF to save weight? I read somewhere that plywood is a bit lighter than MDF. Could somebody please advise me on the pros and cons of building in plywood and what it would involve.?
 

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I prefer to use plywood when building a cabinet but it is more expensive. I also prefer high quality ply so it tends to be double the price or more than MDF. Plywood is lighter than the same thickness MDF.
 

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As chrapladm has mentioned, unless you get high quality (read: expensive) ply it's probably not the best material to use. MDF has been chosen by the vast majority of subwoofer manufacturers for several reasons, so cost was not the only factor. It does have some inherent advantages over ply.

One question though... very rarely is a subwoofer relocated once the ideal location has been selected, so weight is generally not a factor when considering the cabinet material. Are you planning on moving this unit frequently?
 

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MDF has a consistent density, plywood's density is affected by the multiple layers and the adhesive used which can affect its resonance. Also, you can never know if the plywood will separate its layers down the road due to all the stresses from the pressure if used in a subwoofer or a bass heavy design...
 

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I have never had a subwoofer enclosure made out of plywood ever split on me.

SO either one will be fine. If you can afford it high quality ply if not then use ply for just the baffle.
 

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If durability and strength are something you are looking at, then by all means use plywood. It is much stronger and more durable than MDF. If it's going in the corner of the room and isn't going to be moved for years to come, MDF is going to work just fine.
 

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Discussion Starter #8
Thanks for all the good feed back. I've not been able to source good quality plywood yet, and it sounds like its going to be blowing my budget anyway, so MDF it is. Does anybody use primer on inside of mdf cabinets for any reason? maybe to improve the air tight property?
 

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Primer.......Never heard of that. Good quality adhesive is all you need.
 

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Discussion Starter #11
Ok this is getting slightly off topic but it relates to building with either material: I know a well regarded speaker designer in Aus who lined the walls of his enclosures with a sealant then lead sheeting then another butumen rubber material and this is supposed to create a really dead enclosure, and in turn result in better sound. This guy designed my mains speakers using the same techniques and this produced a really "dead" enclosure, and sounds great.
 

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There are some that I have red about using similar methods or green glue and multi layers of MDF and then there are others would just use LOTS of bracing.

I personally feel that it is not needed in mos cases especially in subwoofers with adequate bracing. I also would prefer heavy bracing as opposed to lead sheeting and all. That being said if you were chasing a sound that could be very slightly improved by changing cabinet design in the midrange then I would say go for it.

But again this is just my experience with subwoofers. When it comes to 3way speakers and other mains I tend to do overkill bracing and double walls to ensure a dead cabinet.
 

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I personally don't agree with a "dead" cabinet is a requirement. If the sound waves don't interact with the cabinet they will interact with each other, or perhaps the speakers itself, or a combination of the 3. I have loaded a sub with not a sealer but covered it with layers of Dynamat in order to keep the cabinet from resonating (which I think is very important). But for mains I don't see the point of the added expense in a DIY project, but "to each his own". Make you wonder what a speaker made out of 1" stone would sound like, but I guess its alot in the design of the driver and the crossover, you could probably tweek a Hefty Cinch-sack into a usable enclosure
 

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This is an old thread, but I am intrigued by the stone enclosure idea. I have an extra granite slab and the tools to cut it, I wonder if it would make a good sub. I like the idea of a downward firing sealed enclosure/end table.
 

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This is an old thread, but I am intrigued by the stone enclosure idea. I have an extra granite slab and the tools to cut it, I wonder if it would make a good sub. I like the idea of a downward firing sealed enclosure/end table.
My only concern would be with regards to the resonate frequency of the granite itself. If it's in the pass band you're likely to get some SQ issues.
 

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Jim,
Would you still have those issues if the box had acoustic sound damping foam and layers of an elastomeric-butyl material?
 

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Jim,
Would you still have those issues if the box had acoustic sound damping foam and layers of an elastomeric-butyl material?
I don't know for certain if there would be an issue, I only pointed it out because the resonant frequency for granite is likely to be far different than wood or MDF. The properties of the last two are well documented and known quantities because of how often they're used for constructing subwoofers, but there's going to be far less information to draw from when it comes granite. I just figured it might be something worth investigating further.

The RF won't change no matter what you do to the enclosure, but the effect it has would be minimized by internal damping because the back-wave off the driver would be partially absorbed by the foam and lining. That means less force exerted on the enclosure, so less chance for it to resonant in the first place.
 

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Solid maple :) or maple plywood or mdf.

personally I would use 1" aluminum...
 
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