I envisioned a transition at the joint between the side panels and the front panel with the roundovers. The front panel would get painted or duratexted black, and then the remaining panels of the cab veneered with a lighter color veneer. Sorry to not make that clear but I assumed this would come up in discussion. I just don't want to end up with this big box all covered in duratex, and that is unfortunately about my skill level!
I would be tempted to make the front baffle 90* and veneer the whole thing. A mixed finish can be another pain in the butt.
I never understood round-overs on a subwoofer. The round-over is nothing to those frequencies.
What veneer are you considering?
Anyone can feel free to step in and help Charlie. I would love to and might but I am so far behind on so many projects.
The front baffle is 1.5" thick. So it would be possible to guide a saw at 45deg along the edge to make a decent size chamfer. That would look nice, too. Like the pic above in many ways.
Edit: actually I took a look at the cab just now and the cutout rebate is pretty close to the edge. So the roundover could be converted into a chamfer but not made larger.
I could only watch that video for about 30 seconds due to the bouncy camera work. Did he fill the paint cans with any sort of liquid? Did he test the load resistance after it ran for a while and the elements were hot?
He did fill them up with water and got it up to 150 degrees. Still measured 8.1 ohms. Those elements are less than $12/each, so that makes for a really cheap 1kw load setup. I wish they were short enough to fit in one paint can.
That's a great idea! I could bolt the pipes to the back of my equipment rack. I don't generally work on anything over 120W/ch, so it would never get that hot anyway.
Good question. I'm guessing the rating would be lower when it's not in some kind of liquid. But without some kind of datasheet, I have no idea what it might be.
Kinda what I was thinking, even at 1/10th of the rating it'd be 350W @240V. Strapping four together for a 4 ohm load and it's still 1400W@240V. If an amp does 60V@4ohms that's 900W. I think halving the voltage equals 1/4 the wattage, so it would probably need to be liquid cooled as you'd be back to only 350W.
They are Vishay Milwaukee resistors. Each one is 4 ohms rated at 420W continuous and can do 10x rated power for 5 seconds.
I was looking at them as load resistors for amplifier testing but there are some reports that they may introduce too much distortion for the distortion comparisons I do. So, I also have some 100W rated Arcol HS series power resistors along with heat sinks to mount them to, which have a good reputation for amp testing. I will test both and post results.
One of the issues I have with the big Vishay Milwaukee's is how to mount them. The standard method is with end brackets and a threaded rod running through the middle. That to me seems too much like a cored inductor. When I had access to a Ceramics Lab, I would have whipped something up using some scrapped kiln furniture - but I don't any more....
The other problem is that they will take a ton of heat without any issue, but won't dissipate heat very well. That will tend to cause resistance to drift due to the temperature coefficient of resistance of the wound conductor, which might be why some people have trouble with them for distortion measurements. Depending on what you want to do with them, it may or may not be an issue for you.
Keep an open mind, but don't let your brain fall out.
Comments
Post pics and measurements, please. I might have walnut in stock already. My biggest issue is time.
It's this product:
https://www.parts-express.com/Denovo-Audio-Knock-Down-MDF-4.0-cu.-ft.-Subwoofer-Cabinet-for-Dayton-Audio-18-Ultimax-300-7089?quantity=1
External dimensions: 23" H x 20" W x 20.75" D
Would prefer a different wood species.
Those rounded corners are a PITA.
Yep, but I was not envisioning veneer covering them and they are only on the face where the driver is mounted. All other corners are square.
I envisioned a transition at the joint between the side panels and the front panel with the roundovers. The front panel would get painted or duratexted black, and then the remaining panels of the cab veneered with a lighter color veneer. Sorry to not make that clear but I assumed this would come up in discussion. I just don't want to end up with this big box all covered in duratex, and that is unfortunately about my skill level!
I would be tempted to make the front baffle 90* and veneer the whole thing. A mixed finish can be another pain in the butt.
I never understood round-overs on a subwoofer. The round-over is nothing to those frequencies.
What veneer are you considering?
Anyone can feel free to step in and help Charlie. I would love to and might but I am so far behind on so many projects.
Turn the round over into a chamfer and veneer every thing.
The front baffle is 1.5" thick. So it would be possible to guide a saw at 45deg along the edge to make a decent size chamfer. That would look nice, too. Like the pic above in many ways.
Edit: actually I took a look at the cab just now and the cutout rebate is pretty close to the edge. So the roundover could be converted into a chamfer but not made larger.
I cut my big chamfers on my Bosch contractors table saw. I've done small chamfers with a 45 degree bottom bearing router bit.
Ron
Ron's work is always lovely.😍
I am going to start a new thread RE the swap.
Anybody have any large wattage load resistors? I'd like to be around 1000W @ 4ohm.
I hear some oven elements work well and can take the power.
Good suggestion Ken. A few decades ago I used industrial "oven" heating elements as high power loads for our DUT's.
The ham radio guys mount resistors in a paint can full of mineral oil.
https://worldwidedx.com/threads/700-watt-homebrew-dummy-load.48417/
Huh, thats a thought, thanks.
Found this👍🏼
I could only watch that video for about 30 seconds due to the bouncy camera work. Did he fill the paint cans with any sort of liquid? Did he test the load resistance after it ran for a while and the elements were hot?
He did fill them up with water and got it up to 150 degrees. Still measured 8.1 ohms. Those elements are less than $12/each, so that makes for a really cheap 1kw load setup. I wish they were short enough to fit in one paint can.
You could mount them in a metal pipe then fill it with coolant, chances are you would never heat it up enough to need to have a vent.
That's a great idea! I could bolt the pipes to the back of my equipment rack. I don't generally work on anything over 120W/ch, so it would never get that hot anyway.
Are the pipes and coolant even required then?
Good question. I'm guessing the rating would be lower when it's not in some kind of liquid. But without some kind of datasheet, I have no idea what it might be.
The operator might overheat before the element does.
Kinda what I was thinking, even at 1/10th of the rating it'd be 350W @240V. Strapping four together for a 4 ohm load and it's still 1400W@240V. If an amp does 60V@4ohms that's 900W. I think halving the voltage equals 1/4 the wattage, so it would probably need to be liquid cooled as you'd be back to only 350W.
not sure I'm following.
This should probably be broken out into another thread anyway. It is an interesting topic on it's own IMO.
Those big gold aluminum resistors are derated when not properly heatsinked. So was just thinking on the worst side for those heating elements.
Drew has surplus heat sinks.
https://www.ebay.com/sch/i.html?_from=R40&_nkw=8+ohm+load+resistor&_sacat=0&_odkw=8+ohm+load+reststor&_osacat=0
Proper Dale 250W resistors would be in $80 range, those heating elements are $45 and X overkill wattage.
I've got some of these:
They are Vishay Milwaukee resistors. Each one is 4 ohms rated at 420W continuous and can do 10x rated power for 5 seconds.
I was looking at them as load resistors for amplifier testing but there are some reports that they may introduce too much distortion for the distortion comparisons I do. So, I also have some 100W rated Arcol HS series power resistors along with heat sinks to mount them to, which have a good reputation for amp testing. I will test both and post results.
One of the issues I have with the big Vishay Milwaukee's is how to mount them. The standard method is with end brackets and a threaded rod running through the middle. That to me seems too much like a cored inductor. When I had access to a Ceramics Lab, I would have whipped something up using some scrapped kiln furniture - but I don't any more....
The other problem is that they will take a ton of heat without any issue, but won't dissipate heat very well. That will tend to cause resistance to drift due to the temperature coefficient of resistance of the wound conductor, which might be why some people have trouble with them for distortion measurements. Depending on what you want to do with them, it may or may not be an issue for you.
Sehlin Sound Solutions