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Old 25th August 2008, 03:56 PM   #1
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Default Wood & Varnish

A discussion was had between Scottmoose and I over wood selection for building horn speakers. Different types of finishes were also discussed. Obviously like anything else in audio, preferences and bias will depend on personal preference & thy ear taste buds. It seems the subject might make a nice discussion thread.

Here is a little of my experience with diff woods and Spawn designs...... This should get the thread started...

I've built three pair of Saburo's and two Sachiko's. One pair of Nagoaka D90's and a pair of Derek Walton inspired voigt pipes from solid pine.
All of them I've built from different wood and used different finishes.
My first Saburo was constructed from 3/4" Maple Ply. The front and sides were covered with Maple veneer to hide the ply edges. I then coated them with a water based General Finishes Polycrylic, which is recommended for Maple as it stays clear and does not yellow like some oil based poly is prone to.
The second set was made from Cherry ply with no veneer. Stained and then coated with the same polycrylic. (easy to work with and clean up)
Both were in my listening room at the same time. (photo below) To this day I still feel the Maple ply had a "livlier" sound. Perhaps quicker sounding? The Cherry had a deeper, robust sound.

One Sachiko was built from Birch ply and the other from Maple ply. A close friend of mine had my original birch ply pair that were painted black. (Photo on the Frugal-Horn splash page) He requested I build another for him from Maple and veneer the front with Mahogany to better match his room. When we swapped out the drivers and fired up the new cabinets, we immediately noticed that the new Maple cabinets had that lively sound I mentioned before.
I have a pair of Maple Saburo's about 3/4ths complete. Perhaps some Mono experiments are in order with one finished and one with no finish??
Would be happy to hear your thoughts and observations regarding wood species and finishes.
Photo below is of the Maple speakers and Cherry ones in my listening room at the same time.
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Old 25th August 2008, 05:39 PM   #2
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Hi Derek -good to see you starting a dedicated thread on this. Usually material threads tend to focus on MDF vs BB arguments, so a broader ranging one could be very useful.

I think key to this are the resonant properties of different materials, their MOE / stiffness - density / weight etc. To say nothing of how they've been treated. All materials behave differently, and in an ideal world need treating differently to control their natural resonant behaviour as desired -either to push it to a frequency where it's unlikely to be excited, or to use their different character to subtly add some coloration.

Personally, I don't want my own speakers to add any of their own colorations to the sound -I'd love to build something out of 10 - 14ga CRS if I could, which would push natural resonance modes way up, out of the cabinet's operating BW. GM has mentioned this idea too.

Reducing audible resonances to ~inaudibility is to all tastes though -some people feel that allowing a natural wood material (solid wood or ply or whatever) to resonate in the cabinet's BW gives a more realistic tonality to the sound of recorded acoustic instruments. Here's a couple of old posts by the late Terry Cain that sets out this alternative take:

Quote:
It’s funny, solid wood was / is SO taboo for monkey coffins. Basically any mild hardwood with good stiffness to weight ratio that is of “cellular diffuse” grain structure. Western maple like alder has this consistent structure. Oaks and “concentric ring” type woods are too resonant, or at least they are “louder” being more resonant. I once made a xylophone with a young 6th grader where all the keys are solid wood THE SAME SIZE and the intrinsic tone made a full scale E through F with local woods only. So in a speaker as the Japanese always knew. Wood sounds good. Look at pianos, there are plenty of cheap plywood and “wood products” in newer pianos. But try to convince a player that sounds good? Older solidwood pianos have life and richness that resonant solid wood contains. Speakers that use a cabinet to increase output ie “horn loading”, benefit from the micro reflectivity of a solid wood surface and the homogenously resonant structure. Solidity and stiffness far exceed what is possible with industrial particle wood panel products. They’ll never make an airplane from spars of mdf. And in vibration control stiffness to weight is x and y. Alder has a wonderful complex grain structure that’s very concistent and works extremely well. It’s also very stable over time. TC
And discussing this later...

Quote:
> > Perhaps the speaker industry has headed in the wrong direction by trying to make speaker cabinets absolutley “dead” and neutral.
=I think most japanese audiophiles and most hornophiles would agree. I certainly do. I believe this was an “overcorrection” due to the emergence of particle board in the 60’s. It sucked as furniture, and lo and behold the lowly speaker box industry found a cheap panel to make big-uns with. It fits in the sealed box/highpower requirements of the Hirsch/Houck era. Truckers must love mdf and PB, to and from speakerplants. Anyway I think we definately got carried away with the dubious “positive” aspects of composite wood panels in the name of “saving forests. Now mdf is so ubiquitous that things like “hand tools” are long forgotten tools for building. Automated panel stackers feeding automated hot melt edgebanding and CNC routers build 99% of all wooden audio products.
> > But, maybe we are losing some of the “life” by not taking advantage of the inherent resonant character in natural wood to give audio presentation a more real and textured feeling.
=Takes wood to make wood IMHO. Resonant sound is just that. Coming from a cello or a speakerbox. Interesting that some of the very best speakers in the world use polymer and graphite composites, kevlar etc. Seemingly in order to mock the characteristics of wood.
YMMV, as always. It's not a subject I know much about & there are some very knowledgeable people here, so hopefully we'll see a productive discussion with lots of useful information.

I like the picture of the two pairs of Saburo's BTW.
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Old 25th August 2008, 05:49 PM   #3
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My new favorite quote.... "It takes wood to make wood." T. Cain

I wish he was still with us. I would have loved to have met him.
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Old 25th August 2008, 08:28 PM   #4
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The loudspeaker should be viewed as a fine musical instrument. I wish more manufacturers would put the same emphasis on design and fine tuning as do musical instrument makers of violins, cellos, guitars, etc. There is a lot of math using the golden ratio in making a violin and few designs take advantage of tone woods like sitka spruce or maple. I have yet to see many DIY designs using real wood. Perhaps this is because it is significantly more difficult and expensive to build with real wood due to having to account for movement. Yet few expensive commercial designs use real wood. One exception that comes to mind is Sonus Faber and they are absolutely beautiful. Unfortunately, they are very expensive.

Given a larger room, I would love to hear this design. Even at $3,000, I imagine it would be better than most commercial designs costing significantly more.
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Old 25th August 2008, 09:16 PM   #5
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Well, it's certainly one view.

However, the riposte is that a loudspeaker is not a musical instrument. A musical instrument produces sound. A loudspeaker reproduces the sound of instruments that have already produced the aforementioned sound & which has been recorded.

So if you design a speaker to resonate like a viola, it's probably going to sound rather good when reproducing a viola, but what happens when you feed it with a signal containing, say, a bassoon? Answer: you get a speaker that produces unnatural colouration.
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Old 25th August 2008, 09:16 PM   #6
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I think this is a very interesting discussion. One side says the cabinet should be dead, the other side says the cabinet should be musical. I have several Victrola's and a Brunswick record player. These are the kinds that do not have any amplification, only mechanical amplification, anyway, no electricity whatsoever.

The Brusnwick horn is all wood, the Victrolas have some kind of metal horn at least at the small end. The Brunswick sounds much better than the Victrola. Of course there are many more viarables, the needles, the diaphragms, the tone-arms, a great deal of variables.

I have to say though that on the boards discussing these things, the wooden horns are much more respected for thier tonality, and the sound reproduction of sounds. I guess the wood resonates in a more natural way? I can say with my small collection that it seems the hardwood horn sounds better to me.
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Old 25th August 2008, 09:30 PM   #7
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I'd be careful about introducing terms like 'one side thinks a cabinet should sound "dead" the other side thinks it should sound "musical" ', because it's very easy to misinterpret.

I do not believe a loudspeaker should sound 'dead.' That implies its over-damped. All I'm stating is that IMO, a loudspeaker is not an instrument. It's a loudspeaker, and therefore, it's task is to accurately reproduce a signal fed into it, not produce tones etc. of its own devising.

That's not to say that a cabinet designed to add a little of its own character to things will sound bad though. Sometimes, it can even help make a duff recording sound good. It's a bit of a shotgun approach though.
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Old 25th August 2008, 10:55 PM   #8
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I think it's safe to say, and I'm unanimous in this (grin), that the recording process removes some information. No matter how good your recording process is, some information is removed. Also the physics of speaker driver design simply does not allow you to exactly reproduce every sound, A speaker is not a human throat, nor is it an oboe, or a violin. It's absolutely amazing that the driver does such a wonderful job.

Therefore, if the recording process (and of course any signal processing and amplification chain) removes some information, and the driver cannot exactly reproduce all the sounds recorded anyway, I think it's fair to say than any school of thought that allows some 'coloration' as you say to inject some of the original quality back in...is meritorious. (Was that a run on sentence?)

Over damped and underdamped? Really the best solution would be to have a specific speaker design for each musical instrument, make the recording of each instrument separate, and then reproduce them in your home with your 50 or 60 different speakers...problem solved. Looks like you have some work to do. I'll just leave you alone.
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Old 26th August 2008, 02:55 AM   #9
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When I say a loudspeaker should have the same design consideration as a musical instrument, I mean the same level of craftsmanship, attention to detail, and knowledge of acoustics which raises the bar considerably. Speaker enclosures should not resonate with the sound like a violin, but can make the driver more efficiently couple with the air and mechanically compensate for deficiencies in driver response (i.e., back loaded horn). No loudspeaker system should be designed to introduce anything beyond the original recording. Maybe it is a difference of semantics here.
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Old 26th August 2008, 03:43 AM   #10
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I think the cabinet should definately add something. I think it should make the music reach out and grab. I think it should make me feel like I'm there. Whether it does this by efficently coupling with the air or resonating like a violin...I'm sure is a matter of taste. Baskin robins has 31 different flavors because not everyone has the same taste. If everyone was normal, like me, then baskin robins would only carry chocholate.

I'm sure there are enough speakers out there for everyone!

Some people like to put "buds" in their ears. I for one, like to move a lot of air! I want a big speaker that will vibrate your beer mug off the top. I want there to be so much music coming out of them that it makes people become spontaneously incontinent when I turn them up! I'll let you guys pick your own speakers, out however. As long as we all agree that we like speakers!
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