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Old 30th July 2012, 05:15 PM   #111
ChrisA is offline ChrisA  United States
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Originally Posted by Bcrary3 View Post
If one were making his or own cabinet, say for a subwoofer, would it be best to have it made from a solid wood, or a ply wood? Also if it's made from either of these materials, would sidefiring or bottom firing be the best option?
For this use, you want a material that is sonically "dead". That means it does not resonate. Solid wood, especially a soft wood like pine will resonate and add "color"' to the sound.

Use VERY high quality void-free plywood. (they don't sell this at Home Depot) or if you can't find it use 5/8" MDF. MDF is ugly to work with and needs to be covered to look acceptable but it is as sonically dead as it gets. Perfect for a sub woofer. Being void free, like Baltic Birch is very important. Voids can cause an annoying "buzz" when they vibrate. Use only the best plywood, or MDF.

Solid would be good if you were building a musical instrument speaker, A pine cabinet is perfect if you play blues guitar.

If you must have "real wood" nominal one inch maple works for a sub. It has a bright sound if used for a full range speaker but should be OK for a sub.

All that said, if I were going to mass produce hi-end subs. I'd case the cases in concrete. A few people actualy made these in the 1950's. Concrete is a tenth the price of wood and 100 time more "dead" than even MDF. The other 50's trick was to build a double wall cabinet and fill the void space with sand. Then they invented MDF and that killed the resonance problem (but not the "ugly" problem.)

Last edited by ChrisA; 30th July 2012 at 05:21 PM.
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Old 30th July 2012, 06:02 PM   #112
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Quote:
Originally Posted by ChrisA View Post
For this use, you want a material that is sonically "dead". That means it does not resonate.
There is no such thing as a material that doesn't resonate. The key is to design a box that has its resonances placed where they will not get excited.

For a subwoofer this is pretty easy, as one can easily push resonances above the bandwith of the woofer. With no energy being supplied at the frequency panels will resonate, it is as if they do not exist.

The key for a woofer is stiff panels that resist ballooning and that push potential panel resonces high up (bracing is also required).

Good plywood is stiff, much stiffer than MDF (which i believe is unsuitable for quality speaker enclosures). It takes about 1" of MDF to match the stiffness of 5/8" (15mm) of baltic birch plywood. The mass & homogenous nature of MDF brings additional issues.

Solid wood is tricky to work with, and if you have to ask the question, you likely do not have the experience to work with it. Well done (and typically in smaller boxes) solid wood can make fantastic speaker enclosures.

dave
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Old 30th July 2012, 09:32 PM   #113
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ChrisA - concrete or sandwich wall/sand filled enclosures look good on paper, but have you personally ever built, or more importantly, moved any?

maybe you have, and they sound wonderful, but I've found even something as conventional as a well braced dual layer BB plywood box for subs can be a bitch to move.
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Old 30th July 2012, 10:38 PM   #114
ChrisA is offline ChrisA  United States
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ChrisA - concrete or sandwich wall/sand filled enclosures look good on paper, but have you personally ever built, or more importantly, moved any?

maybe you have, and they sound wonderful, but I've found even something as conventional as a well braced dual layer BB plywood box for subs can be a bitch to move.
Not me but my dad did. Back in the "old days" you could not get real quality plywood and more importantly speaker cabinets where quite large. Also back then must hi-end HiFi equipment has build in small quantities in small shops.

But they had refrigerator dollies that would go up and down stairs back then just like they have today. But really, a 150 pound speaker is not all that hard to move around. We don't see them in Best Buy because they would cost to much to ship. Today we have light weight stuff because it is all made in China and the cost to ship depends on the weight. But 50 years ago speakers were mostly build very near or even in the retail HiFi shops that sold them. Many times when you bought something the retailer would come to your house and set it up for you.

I liked the sand idea. Easy to move to your home but then once in place you add 100 pounds of sand. It was actually pretty common up into the early 1960s. Warfdale (sp?) used sand in their speakers and they where very hi-end in their day.

Concrete is not unreasonable. It is actually dirt cheap. a 90 pound bag costs $7.00 But a better reason to use it is that it can be cast into compound curves that are hard to make in wood. For example a true horn shape. The problem is the amount of work to make the forms. This is why I said I'd use concrete if I were selling speakers. They would be easy and in-expensive to produce and I could charge quite a premium price.

Austrians build concrete cast 5.1 speaker set -- Engadget

Speaker Design

Concrete speakers - Noise made me do it - sound,music and things that tickle your ears

One of the problems with these forums is that communications is too good so we all become "copy cat" builders. I'd like to see the DIY audio community get into one of a kind visual designs.
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Old 5th May 2013, 03:25 PM   #115
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I've built concrete speakers – right into the building structure in one case. Though I admit I chickened out and used wooden (all right, plywood) baffle boards, rather than moulding around the correct size oil drum or cylindrical whatever. Something I noticed, after a year in place they were still producing dust; acoustically irrelevant, but poor WAF.

Wouldn't like to tour them, though, or use them as OB monitors or for live recording. Don't much like MDF for that matter (that is the trendy name for chipboard, isn't it?). Not just weight, they tend to fall apart under impact stress, even if you put chicken wire reinforcement into the concrete.

One trick I picked up from the Beeb for lightweight acceptably low resonance cabinets was to use relatively thin ply (19 – 23mm) (good quality, though. I'm afraid getting cheap ply isn't worth the savings) then bond fiberboard to the inner surface to damp it down. Mount the driver, and attach a sweep frequency generator. With your fingertips you can feel the points where panels start to flex at specific frequencies; mark these, and add bracing only where it will be effective. A lot lighter than the equivalent build homogeneously.
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Old 2nd July 2013, 02:28 PM   #116
M Gregg is offline M Gregg  United Kingdom
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What's the difference,

Between teak oil and Tung oil?

How do you apply it?

(I'm assuming teak oil is not just for teak wood?)

I notice in post #75 of this thread an oil and wax finish<<what oil, and what wax was used?

Regards
M. Gregg
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Old 2nd July 2013, 03:03 PM   #117
M Gregg is offline M Gregg  United Kingdom
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I also found this interesting,

How to Finish Quarter Sawn White Oak So the Figure Pops Woodworkers Source Blog

Regards
M. Gregg
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Old 2nd July 2013, 04:10 PM   #118
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Teak oil is made from the teak tree, Tung Oil is from Tung.
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Old 2nd July 2013, 04:56 PM   #119
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Originally Posted by Cal Weldon View Post
Teak oil is made from the teak tree, Tung Oil is from Tung.
Tung nuts, specifically. Tung oil is a drying oil.
Tung oil - Wikipedia, the free encyclopedia

You apparently have to be careful with "teak oil" since it may be an oil intended for teak wood (and thus has no or very little teak oil in it) or it may be actual teak oil. Actual teak oil dries extremely slowly and has to be reapplied once in awhile.

For wood finish, you want a drying oil, like tung oil, Watco or boiled linseed oil. Oil often has chemicals added to it to make it dry.

For a traditional oil finish, which does not provide very good resistance to stains or moisture, it's traditional to apply a good wax (carnuba) to help protect it.

There are other finishes, like my favorite Waterlox, which have tung oil in them, but added chemicals to make the finish water proof. You want a water proof or at least moisture resistant wood finish to prevent wood movement. This is the reason that wood finish was invented in the first place many centuries ago. They found that their furniture fell apart from wood movement. This is also the reason that frame and panel construction was invented because it accommodates wood movement.

Shellac is an awesome wood finish you may also consider, though it is not tough and not resistant to alcohol (don't put your martini on your speaker cabs!).
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Old 2nd July 2013, 05:51 PM   #120
ChrisA is offline ChrisA  United States
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Quote:
Originally Posted by M Gregg View Post
What's the difference,

Between teak oil and Tung oil?

How do you apply it?

(I'm assuming teak oil is not just for teak wood?)

I notice in post #75 of this thread an oil and wax finish<<what oil, and what wax was used?

Regards
M. Gregg
This is not the rocket science people are making of it. All you do is buy a can of "oil wood finish". You put some ona rage and wipe it on, let it soak in a few minutes then with a dry rag wipe off as much of it as you can. Then wait some number of hours and you are done.

The trick is finding a brand of "oil wood finish" you like. There is no "best". and brands vary depending on where you live.

Oil finishes work best on hardwoods and even better on oily hardwoods like teak.

I have also allied water based acrylic on white pine as if it were an oild finish. That is with a rag and then wipe it dry. A tiny bit of the finsh soaks in then cures and makes the wood water resistant but never forms a film so the grain shows. It loks like bare wood. That is the advantage if oil, it does not form a film so the wood shows. It's disadvantage is that there is no film to protect the wood.
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