emilime75 wrote:
| Yay...my 1st post. This is actiually very much how I build my boxes as well. I've also been known to incorporate the bracing to support the back end(magnet) of some heavy woofers. A few points I will dare make, first of your work is good but there are some things I would do different. |
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I don't have any problem with suggestions. Also, they are good suggestions/comments...
emilime75 wrote:
| 1. Solid pine like that moves, a lot. It will expand and contract and eventually your joints will break free. Sticking with plywood or plain old MDF would be a much better choice, especially when the enclosure will live in the trunk of a car. If you really like the look of wood, use a real wood veneer after construction to make it look pretty. |
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True, but not as much as you think, though. While "a lot" is completely subjective, first of all, but there are also some fairly hard and fast numbers that apply to pine. Called the coefficient of expansion, this particular number for Douglass fir (the most commonly available version of pine plank or lumber) is between 2.1 and 2.8 per degree F, depending on where you find your numbers. That means that the difference of my particular panels (about 13 inches square), when measured at 0 degrees F, to 130 degrees F, would figure like this: .000028 X 13 X 130 = 0.04732 inches. Five one-hundredths of one inch is the expansion of any individual panel in my enclosure. Granted, in a MUCH larger enclosure, panel size and expansion can absolutely come into play, but in my case, THERMAL expansion is a non-issue. Moisture expansion, in Bakersfield California, where a muggy day is between 12% and 14% RH, I'm also of a mind to believe that humidity will never be an issue in this case, either. I was unable to find hard numbers regarding expansion of pine vs. humidity.
emilime75 wrote:
| 2. Gorilla glue is great stuff, and if you brad nail it AND CLAMP it together while it's brewing, you should have nice strong joints...however, what someone else stated about wetting the wood before applying Gorilla glue is true. It does not require much water, just barely damp, and it will cure stronger, not necessarily faster. This is how Gorilla glue works, as it is a reaction that occurs with moisture and this is true for pretty much all Polyurethane glues. You can read about this on Gorilla's website. |
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I do clamp. The brads (by the time the urethane cures) have added so little to the joint that they become non-effective, literally, and were they to be remove after the cure, the joint will be absolutely no weaker, but leave me with nail holes to fill. More work and no benefit, so no brads for me. As far as the dampening of the substrates? Never done it, never will. There is invariably enough moisture in the wood, even if kiln-dried to around (a typical) 9% or less, for proper curing of the adhesive. Adding moisture only reduces my working time, while adding nothing to the end product. In my experience, the glue foams significantly more when additional moisture is brought to the party, which to me means there is less adhesive left in the joint, which translates to a weaker joint. This may or may not be the actual case, and whether it is or not, the glue-to-wood interface is FAR stronger than the wood itself, so this should be nothing I have to worry about either.
emilime75 wrote:
| 3. You're right on about not needing any additional sealers after using Gorilla glue, as it expands naturally as it cures it does a good job of filling up any small cavities that might exist and will usually not require any sealents for the corners... but, we're back to that solid pine issue again, and this could be a cause for concern. |
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One of the things I love about Gorilla Glue, and have loved, since the first time I ever used it... One step cure all... Strong joint, and sealed as well!
emilime75 wrote:
| 4. This is the last one, I promise. When bracing your enclosures, you should try and place those braces in somewhat random places in order to avoid breaking up the panels into even dimensioned proportions. Doing that will eliminate the possibility of additional resonances building up inside the box and the possibility of it sounding bad. |
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In a larger box, you are absolutely correct. In a 12 inch cube (internal dimensions), there is no way for ANY standing wave to occur at the frequencies I am running. This particular enclosure is destined for 100Hz (wavelength? 11.3 feet!) and below, at a 48dB slope. When building a full-range system, I will always brace and even build the enclosure itself, using the Golden Ratio (.6 to 1 to 1.6) to prevent or at a minimum, minimize standing waves.
emilime75 wrote:
| Again, you obviously do good work, and I don't mean to be a know-it-all, but I have many years behind me as a wood worker/carpenter/speaker builder and a general audio enthusiast. |
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Thank you. I too have many years of cabinet building. Been into woodworking and cabinet building since high-school, some 20+ years ago, a wood shop in my garage, welding, electrician with the Navy from 86 to 92, and "The Critical Ear" for more years than I can remember. Currently the sub in my car is an iso-loaded 10" stuffed transmission line. Been an experimenter/builder since I can remember. Yep, I've done all that stuff for a while, too!
It all reminds me of something that Molière once said to Guy de Maupassant at a café in Vienna: "That's nice. You should write it down."
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I have seen a lot of different materials used for making an enclosure but this is the first I have seen using pine plank. It looks good though. You just forgot one thing, how does it sound?
I am curious to what you used to run the speaker wire through the enclosure. Did you simply drill a small hole and sneak the wires through it or did you use another method?
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