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Monday, October 31, 2011

Speaker Cabinet Construction Materials

It's surprising just how important the material that a speaker cabinet is made from is to the sound. Here's an excerpt from The Ultimate Guitar Tone Handbook that describes just how great a factor the construction material really is.

"The type of wood used for building a cabinet contributes to its tone. Cabinets, like guitars, can be built out of just about any kind of wood. But just like guitars, just a few kinds of wood are used because of their sound or cost.

Baltic Birch
Marshall cabinets are built out of 11 ply Baltic birch, a wood that’s known for its strength and light weight. This is one of the reasons (besides the speakers and the closed back) that nothing else sounds quite like a Marshall cabinet. Other manufacturers also use birch, but some use the cheaper and thinner 3 or 5 ply, which compromises the sound. Others use 13 ply birch to make the cabinet more robust in transport, but heavier as well (see the graphic on the left).

Pine Plywood
Early Fender cabinets were made of pine (see the figure on the left), which is light and has it’s own tone. Pine was inexpensive, easy to get, but it wasn’t the strongest wood, which was a negative for the gigging musician. Like most manufacturers, Fender slowly but surely changed their cabinet wood, first to marine plywood, and then particle board (known as MDF - medium density fiberboard). MDF is very strong and inexpensive, but contributes is somewhat neutral sounding at best, and harmonically dissonant at worst.

Medium Density Fiberboard (MDF)
Today, most manufacturers (even Fender and Marshall) use MDF for their inexpensive cabinets, and birch or birch composite for their more expensive or vintage cabinets. (see the figure on the left) That’s why you can have two cabinets from the same company loaded with the same speakers, yet they can sound completely different.

Plywood and MDF has less cabinet resonance than solid woods like pine, cedar and birch. The resonance is what contributes to the “warmth” of the sound, but can also be responsible for blurring the notes because of the slight absorption of sound. That means that the sound coming out of a pine cabinet may be full and round, but it won’t project as well as a cabinet made of plywood. Baltic birch is chosen because of its musicality, although it’s not quite as resonant as pine although it does have a bit harder edge. The resonance that occurs with MDF is described as “dead” and “atonal.” Anything that adds color actually wastes a bit of the speaker output since some of the energy vibrates the wood instead of the air.

Sometimes cabinets were designed out of necessity instead of a grand tonal design. In the case of the famous Marshall 1960 4x12, the cabinet was built as a way to contain the four Celestion G12 speakers, which were cheap and plentiful at the time. These speakers were rated at just 15 watts and were prone to flapping on hard hit low notes, so the closed back cabinet helped limit the cone travel because of the air suspension, and having four speakers kept the amp from blowing them out."

You can read additional excerpts on this and all my books on the excerpts page at
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Rand Bliss said...

Ahh Bobby...that's great. Sounds like you're a Marshall Man deep down. Absolutely!

Favorite of yours truly too. There are certain craft traditions in this world that just have to be continued - Marshall's is definitely one of them.

If you want classic tone, stick with what works. And if it ain't broke, don't fix it ♫

Anonymous said...

Cabinet resonance and rattle can certainly ruin an otherwise great amp. I recently bought a fender pawnshop amp it has a resonant vibration to certain notes that makes it unusable at higher volumes, but if I plug in my good old marshall 1922 cab it sounds fantastic.
I have disassembled the fende amp and added some additional wood screws to try to tighten it up, but it did not help. Any suggestions?

Bobby Owsinski said...

Screws aren't usually enough. You'll have to glue everything as well.

See if you can determine exactly where the problem is by having someone play through it while you listen.

It might be the hardware that's causing the problem.

Unknown said...

I've been looking at 2x12 cabs, and find it confusing and somewhat absurd that most are more expensive than their 4x12 counterparts, but also I hate particle board.. it's heavy and dull. I don't mind a slight compromise of sound for portability, so I've been tooling around with the idea of building a smaller, lightweight 2x12 out of Pine or the birch you mention in the article.

Would you have any recommendations or advice on how to approach it? Or should I just cave and spend stupid money on an Orange or other 2x12 that's overpriced but (arguably) better built and properly matched (speakers to size to wood to airflow, etc..)?


Bobby Owsinski said...

Check out Rocket Rocket Cab or Mojotone empty cabinets first before you build. They're a lot cheaper and you'll get exactly what you want.

Unknown said...

Hi everyone,
I have an old Sunn 1200S head (tubes) that I am restoring, but no cabinet. Wondering what type of wood was used in the original (70's era) construction? I may need to build my own. I seem to recall most cabinets used six 12" speakers. The amp was a powerhouse, and I last used in in a studio perhaps 20 years ago with an unknown (forgot the name / specs) cabinet.
Thank you.
Al -


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