Discussion on what materials to build speakers out of

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scottmoose: I have worked with solid wood all of my life, and for the part 25 years professionally. I have built a hugh number of things with solid wood, so I know exactly what it will do.
When I get the opportunity, I will read everything by Terry Cain, not because he has anything to teach me about wood, but for my own personal amusement. I'm always interested in the spread of misinformation.:)
What I am saying here is that this is suposed to be a DIY forum, not the prestigious League of Elite Speaker Constructors. Rookie box builders shouldn't mess with solid wood for speakers. They also shouldn't be bullied into thinking that they will get inferior results by using a cheap material like MDF. Ever hear of Tony Gee? What, are all of his efforts garbage because he uses MDF?
I don't think so.
 
Err, Terry was first and foremost a DIY enthusiast. That's how he started, and remained to the end. He sold speakers for sure. That was his dream, after 3 decades of building fine furniture. His tragic death last December robbed us all of a good friend.

No acrimony intended on my part Al. Sorry it came over that way to you, or anyone else, and any unintentional offense I caused I apologise for unreservedly.



edit -I removed anything from this post that might have been construed as having a personal reference. As noted above, none was intended.
 
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As you know, I am fairly new to this forum. I joined to engage in conversations about one of my favourite topics: audio. It seems that here, unless you ask a question that all of the "experts" can weight in on, you are ignored. No one wants your opinion, they just want to answer your question. Some of the answers are wrong, I should bite my tongue?
A man walks into a bar where no one knows him, does that mean he knows nothing?

I'm having fun pinkmouse;)
 
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scottmoose: Sorry for the typo. BTW I visited Terry Cain's site and noticed that they use the much maligned Voigt pipe design. While this is a good design for solid wood (it eliminates cross-grain joints, at least on the top), didn't Martin King condemn this design as the worst possible TL configuration? Haveyou had the opportunity to hear them in action?
With that said, my rear surround speakers are small Voight pipes. Being surrounds, I never hear enough output to judge the quality.
 
Hi!
I think it was mentioned before but this is crucial when building with solid wood.
Even when moisture content is correct, the wood has to be sealed with lacquer on internal walls also. It's enough with one layer but it will almost impossible to glue them together with water based wood glue. Better then to use a solvent based glue but as always, test first if you have adhesion between lacquer and glue.
Another option is to mask the areas to be glued.

I had a humbling experience a few decade's ago. I had a house at that time with some pine tree's in the garden. A storm brought down five tree's. These were cut and dried in a friends sawmill. Two pair of speakers were built. 5-6 months later I was sitting and listening when a strange, like electric charges, occured! I turned off the amplifier but still could hear this sound. Turned to the loudspeaker and saw a crack travel from bottom to the top!!

Conclusion is, one can build speakers of solid wood BUT be prepared to get unpleasant surprises. It's a living material and despite your 100 years of wood working, mother nature does not give a d%&n of your experience.
BTW, my BIB's made of veneered chipboard has warped also, I think that you are not safe whatever is used.

Cheers
Peter
 
frugal-phile™
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MJL21193 said:
Terry Cain's site and noticed that they use the much maligned Voigt pipe design.... Haveyou had the opportunity to hear them in action?

The Abbey is actualy a mass loaded voigt. Not as much mass as i'd use, but they do sound quite good. I don't know if they sound as good as possible -- it would be interesting to hear them in comparison to a set of Metronomes with the same driver.

dave
 
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peterbrorsson said:
when building with solid wood.
Even when moisture content is cor

As i mentioned when i suggested the pine over the MDF, i did say that you needed to know what you were doing... building with solid is challenging. I have alerted Scott Dunn to this part of the thread -- he is the foremost expert i know on the subject. opefully he will check in on Monday (he only gets email at work) and comment.

dave
 
Can of worms. Abby is an ML TQWT -like Dave, personally I'd use more mass-loading with the port, but they've a good reputation.

Conversely, the Lowther Club of Norway Voigt pipe has a duff reputation. Usually this is blamed on it being an So=0 design. Actually, it's not that that causes all it's problems, but a mismatch between length, Vb and vent dimensions. Abby, although it looks like an So=0 design externally, actually isn't. That's as far as I can go on-line though re it's internal dimensions, as they're a current production model for the company.
 
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I've never been a fan of the tall obilisk shaped speakers, either flat topped or one-side leaning.
>So< must be so close to 0, it might as well be 0.It wouldn't be hard to model with MJK's mathcad models anyhow. Using that, the best results are always obtained with the taper going the oher way, reducing cross-section toward the port.
Increase mass loading by making the port smaller, right?
 
As i mentioned when i suggested the pine over the MDF, i did say that you needed to know what you were doing... building with solid is challenging. I have alerted Scott Dunn to this part of the thread -- he is the foremost expert i know on the subject. opefully he will check in on Monday (he only gets email at work) and comment.

dave

Well, I prefer to build with solid wood or chipboard. In my occupation I have to have some general knowledge in all of the mentioned materials.

The issue with MDF is as always, the sand dust from MDF is not so good for your lungs.
Also there's problems with the edges that tends to crack if the bonding in production of the MDF is not 100%.
Manufacturers of MDF do not keep the mixture of fibers constant due to availability of raw material =You could have a board with totally different properties from batch to batch.
This is hard earned experiences from my profession but maybe not an issue for the DIY community.
All in all, it's your choice that matters in the end

Cheers
Peter
 
I'd paint the mdf if that ends up being that which I use. Still waiting to see what kind of Ply I can get and at what cost.


Pine is going to be expensive relative to the quality of the wood itself and price of MDF, and I'd only end up using it on the side panels. But I am familiar with it's tendency to warp, so it is likely a no-go, I had a look at the stock and its not as good as I'd want for the risks. I can only get HDF at 1/2".
 
It's trunkated a fair way down the pipe. CSA of So still isn't vast, but it's significant. That's as far as I can go.

Yes, decreasing port CSA and / or increasing port length will increase the mass loading on the pipe. I've modelled Abby in Martin's worksheets -it's easy enough to do. I can't post the plots though for obvious reasons. Nelson Pass has some measurements of his own pair on his First Watt site.

Re a negative taper always giving better results, not really, no. It's application dependant. A positive taper QWR will always need to be longer than a straight or negative taper line as the resonant frequency of a pipe is a function of both length and taper, not just length. Conversely, you get more pipe-gain from an expanding line, which, for example, a low Q driver (or a fairly high Q one come to that) would find beneficial. Swings & roundabouts really.
 
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peterbrorsson: True, about there being a difference in MDF from sheet to sheet, manufacturer to manufacturer. One thing though, is the consistantcy of the material in each sheet is uniform, unlike solid wood.

scottmoose: I should hve qualified it by saying " better results for reasonable sized boxes" My master won't let me play with FR drivers, so I only have experience with real ones where high Q = less than ideal for a mass loaded system.
 
peterbrorsson: True, about there being a difference in MDF from sheet to sheet, manufacturer to manufacturer. One thing though, is the consistantcy of the material in each sheet is uniform, unlike solid wood.

Hi MJL21193!
Consistancy of MDF in the same sheet is not the same. How do I know that? I have to be precise in application of stains and lacquers when testing for industrial use. Everything is measured in g/sqm. What I do is take a sheet and cut it in the same dimensions in order to make it easier to measure applied amounts. Each piece weighs different so I have to tare the scale every time a new piece is used. Ergo, density varies, consistancy not so good.
Truth is that I have not compared density differencies in percentages between solid wood and MDF. My bet is that hardwood is very close to MDF in this case. Pine and spruce are different animals.
In reality I don't think it makes any difference concerning "normal' sized speakers. What matters is price!!

Cheers
Peter
 
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Hello Peter! How much difference are we talking about here? In solid wood you can actually see the difference - growth rings, winter growth is slower and denser than summer growth. My own personal perspective is that the differnces between all of these materials is small, be it MDF or plywood or particleboard or solid. The difference between these only detectable by a Golden Ear type.
 
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MJL21193 said:
My own personal perspective is that the differnces between all of these materials is small, be it MDF or plywood or particleboard or solid. The difference between these only detectable by a Golden Ear type.

2 VI diyFests ago we built otherwie identical MDF & plywood bipolar ML-TLs for the FR125. Everyone could hear the difference.

dave
 
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