Speaker Related Projects

   Vector2
(A T-line and ribbon tweeter 2-way. August-2012)

   Polaris
(A tall, thin, upwards firing omnidirectional speaker. May-2010)

   Shiva_PR15
(A powered subwoofer using a 12" driver and 15" passive radiator. Jan-2010)

   Can-Less
(A computer speaker; redux. December-2005)

   Can-Can
(A computer speaker in a light canister. Jan-2005)

   Sonosub
(10" vented subwoofer in a cardboard tube, powered by a Parapix amp. May-1999)

   MTM Center Channel Speaker
(A Madisound design. Nov-1997)

   2-way Surround Speakers
(5" woofer and 1" tweeter. July 1997)

   3-piece mini system
(6" DVC bass module mated to 4" car speaker. June 1997)

   3-way Vented Floorstanding Speaker
(vented 10" woofer, 5" mid and 1" tweeter in a 4 ft tower. Summer 1995)

   NHT1259 Subwoofer
(A 12" woofer in a sealed architectural pedestal. Winter 1994-95)

   Inexpensive Speaker Stands
(Particle board, sand and spray paint. Fall 1994)

   2-way satellite
(6.5" woofer and 1" tweeter. Summer/Fall 1994)

Electronics Related Projects

  900 MHz Audio Receiver
(Better use for bad headphones. Jan-2008)

  Buster - A Simple Guitar Amp
(Perfect for the beginner. Jan-2010)

  A PC-based Audio Console
(Use a PC to play tunes. Jan-2010)

  LM-12 Amp
(Bridged LM-12 opamps. Aug-2003)

   CeeDeePee
(A CD player and FM tuner from spare computer parts. Oct-2002)

   Quad 2000 4-Channel Amp
(Premade modules by Marantz. May-1998)

   Zen Amp and Bride of Zen Preamp
(by Nelson Pass. Apr-1997)

Articles

  Backing-up LPs to CD-R
(Whiningdog.net 10-Dec-2002)

  Using Wood in Speakers FAQ
(Work in progress)

   MDF FAQ for speaker builders

   Woodworking Tools for the DYIer
(HomeTheaterHiFi.com Oct-1998)

  Some Thoughts on Cabinet Finished for DIY Speakers

   Large Grills Made Easy

   Some Parts Suppliers
(Outdated)

Other Useful Stuff

   DIY Audio Related URLs

  Veneering Primer
(by Keith Lahteine)

   How to get a Black Piano Finish
(by DYI Loudspeaker List members)

   Sonotube FAQ
(by Gordon McGill)

   Excerpts from the Bass List
(Oldies but Goodies)

DIY Loudspeaker List

   Current DIY Loudspeaker Forum Home

   Former DIY Loudspeaker List Subscription Page

  DIY Loudspeaker List Archives

Using Solid Wood in Speakers FAQ (Work in Progress)


by Louis Lung

original revision 0.1; 09 January 2001
revision 0.2; 21 March 2001


Disclaimer

The information presented here is provided as-is and is believed to be correct at the time of its writing. No guarantees, implicit or otherwise are provided. Use this information at your discretion. Neither the author, nor contributors, are responsible for any injury, damage or loss, directly or indirectly related to the contents of this FAQ.

Woodworking is potentially dangerous. Make sure you understand the proper use and operation of any tool before using it. Remember - Safety First !


Notice

The goal of this FAQ is to provide information pertaining to the use of solid wood (sometimes refered to as lumber) in speaker building. While much of the information contained here pertains to woodworking in general, the emphasis is on speaker building.


In creating this FAQ, I consolidated various pieces of email I had previously written for the Bass List with some new material, and am presenting it in a Q&A format.

Purpose

Speakers can be made from all kinds of materials. For commercial off-the-shelf speakers, particle board is typically used. Higher quality speakers often use medium density fiberboard (MDF). Yet others use materials ranging from concrete to stone to composites. Just about anything is possible. For the hobbyist, the obvious choices are typically readily available building materials from the local lumber yard or warehouse store.

Among DIY cicles, natural wood (a.k.a. lumber or solid wood) is a common choice. Solid wood offers the appeal of wood's natural beauty and gives the feel of a heavy, dense, handcrafted speakers. But like all things made of natural wood, the results are not always easy to predict.. Each building material has its own set of characteristics and wood is no exception. The purpose of this FAQ is to provide relevant information on the use of wood in speaker building. The goal is not to tell somene what to do and what not to do - that is purely the builder's decision. Rather the goal is to provide a foundation on which the builder can make an educated decision after assessing both the risks and thebenefits of using lumber.

Table of Contents


Q: What is meant by Solid Wood or Lumber ?

A: In this FAQ, the terms "wood", "solid wood" and "lumber" are used interchangeably. Solid wood is real, natural wood; not a man-made material. Examples of a man-made wood product are plywood, particle board, medium density fiberboard (MDF), and flakeboard.


Q: In general, is it a good idea to use Lumber for speakers ?

A: In general, it is not a good idea to make an entire speaker out of solid wood. This is not to say that it can't be done; just that the average builder should not consider doing so without a good solid understanding of the issues. There are some places in a speaker where it is generally, relatively easy to use solid wood. In other places, solid wood is more difficult to use properly.

The two main reasons for not using wood are (1) wood's non-uniform characteristics and (2) wood's movement. The former affects the sonic qualities of the speaker box, the latter affects the integrity of the box with changes in the environment.


Q: Wood is nice and dense; it must be better than man-made materials right ?

A: Some hardwoods are denser than man-made composites, offering what appears on paper to a superior material for speakers. However, this density varies millimeter to millimeter within the wood - growth rings are the simpliest was to "see" this change in density. Density also varies at a larger scale, from board to board, tree specimen to specimen.

Because wood is a natural material, it lacks uniformity thus making it a poor choice as the main building material for speakers.Ultimately, it is not density alone that makes one material better than another. Uniformity is much more important and solid wood cannot match the uniformity of man-made composites like MDF.

Remember that while the quality of a musical instrument (such as a violin) is often associated with the particular sound it produces, a speaker box is not supposed to produce any sound at all; only the drivers are supposed to cause sound. The box resonances that cause the box to "sing" in a totally wooden box are much harder to tame than in a composite box.


Q: What is wood movement ?

A: Wood movement is the expansion and contraction of wood as it absorbs and releases moisture.


Q: What affects wood movement ?

A: Many factors affect wood movement. Below are some of the obvious ones though there are probably more.

  • The cut of the wood -
  • The humidity -
  • The temperature
  • The finish applied -

Q: OK, so wood moves. Why does that matter ?

A: The total amount of movement is proportional to the size of the piece so for small pieces of wood, these changes are extremely small and will not likely cause problem. One typical use for small pieces of solid wood is along the edges of speaker panels where a roundover (radius edge) is more easily obtained with solid wood and much more difficult to do with veneers.

Because speaker baffles and side panels are much larger than edge trims, movement in lumber can be significant and may cause problems. Here are pictures of two speakers made of MDF with a solid wood baffle. The wood is stained hickory with a clearcoat (by Ray Wagner, used with permission).

cracked

This one has a cracked baffle.

not cracked

while this one remained intact.

The moral of the story is that using lumber in a speaker may cause problems, but like all natural things, you'll never for sure until it happens. How lucky do you feel ?


Q: Do some woods move less than others ?

A: Yes, each species has its own characteristics.


Q: Do some cuts of wood move less than others ?

A: Yes. Radial wood movement (quatersawn lumber) is typically less than tangential movement (plain sawn). How much less ? If you look up the charts, most woods have radial movement in the range of 30% to 70% of tangential.


Q: Can I prevent wood from moving ?

A: Practically speaking, you can't. Better yet, you shouldn't try to. [fill in]


Q: If I put a finish on the speaker, wouldn't that seal the wood and keep it from moving ?

A: A surface finish reduces the rate of moisture transfer but does not eliminate it. Different finishes affect the rate differently so reaching EMC (equilibrium moisture content) will take different amount of time with differing finishes.


Q: What's the problem with a cross-grain wood joint ?

A: [fill in]


Q: Since glue is said to be stronger than wood, why can't I just glue it down and prevent it from moving ?

A: [fill in]


Q: If wood moves, wouldn't normal wood furniture have the same problems ?

A: Yes. In fact anyone collecting antiques will tell you that panels made from solid lumber usually fail the test of time if they are not allowed to move. Wood movement doesn't have to be bad. It's only a problem when the construction does not allow it to move. That's why glued (or otherwise movement limiting) cross-grain construction is bad and why floating panels are used in quality solid wood furniture.


Q: If cabinet makers can solve wood movement problems, why can't I use the same techniques on speakers ?

A: Floating panel construction is typically used to account for wood movement in furniture. In a speaker a floating panel is risky to implement - since it's designed to move, it can rattle. The rattle can be limited by various means but suffice it to say that it's not your typical construction. It also won't be airtight so it'll need an additional airtight interior box.


Q: I've seen/made/heard of wooden speakers that don't have any of the problems you describe. What's the deal ?

A: [fill in]


Q: I really want to use lumber. Is there any way to still use it in my design ?

A: [fill in]


Q: Isn't plywood made from wood ? How come it doesn't have movement problems ?

A: [fill in]


Q: What if I glue wood to a box ?

A: [fill in]


Q: Isn't veneer wood ? Why doesn't it have movement problems ?

A: [fill in]


Q: I really like the look of real wood. How can I get that look without using lumber ?

A: The simplest method is to use a veneer. Wood veneers are thin slices of wood which are glued to a stable substrate - your speaker box. Veneers offer several advantages :

  • Once glued to a stable substrate, they will not have lumber's movement problems.
  • They are much more environmentally friendly than solid wood. They are sliced, not sawn so there is much less waste. Each tree yield many more square feet of coverage as a veneer than as solid wood.
  • There are several ways to slice a veneer from a log. Some methods yield a veneer with an appearance not obtainable from lumber.
  • Some rare and/or expensive wood species are only available as veneers.
  • Veneers can be glued on curved surfaces.
  • Veneers easily cover up ugly boxes made from composites giving both the advantages of man-made materials and the beauty of wood.
  • Pre-veneered furniture-grade plywood requires no veneering skills, and comes in many different species of wood.

See Keith Lahteine's Veneering Wood and Plastic Laminate primer for more information on veneering

A: For those not satisfied with the look or "feel" of a veneer, it is possible to make your own plywood from lumber.


Q: Where can I get more information on wood ?

A: Check out the following :

I left out a lot of details that are beyond the scope of this FAQ. Anyone wanting more information on wood and its properties should check their local library and/or online sources.


Q: Where do I send comments, suggestions, additions and corrections for this FAQ ?

A: See the "About" page on this site.

 

 

01-May-2004


Note: The contents in these pages are provided without any guarantee, written or implied. Readers are free to use them at their own risk, for personal use only. No commercial use is allowed without prior written consent from the author.