Wapsi Square Forum

Crossover networks: Wow, been a few years...

Love the fact they're using the 18-ohm resistors in parallel - that being done for capacity or just to get the resistance down low enough?

Just Old Al wrote:Crossover networks: Wow, been a few years...

Love the fact they're using the 18-ohm resistors in parallel - that being done for capacity or just to get the resistance down low enough?

The upper sketch says that they're 25-watt resistors.

A 4.5-ohm, 100 watt resistor would be a real beast! I imagine that using four resistors in parallel provides the necessary amount of heat dissipation capacity rather less expensively... and with less inductance, perhaps.

I haven't traced out the schematic to see whether these are acting as a series pad for the tweeter, or as a Zobel... but in either case, the amount of power they are designed to work with, says that these crossovers we probably from some very hefty speaker systems!

I am suddenly reminded of "Resistor Brakes" used by diesel-electric mining equipment (Like, the BIG house-sized dump trucks and stuff). Motion is converted to electricity, electricity is pumped through a huge bank of huge resistors, converting electricity into heat. A radiator then pulls heat away from the resisters so they don't pop.

Rather ingenious, really, because dissipating kinetic energy as heat via frictions causes a lot of wear and requires a very frequent replacement schedule.

The next step, of course, is to replace the resistors with batteries, to store the energy instead of let it float away as waste heat. I believe Priuses and other electric vehicles use something like that.

GlytchMeister wrote:The next step, of course, is to replace the resistors with batteries, to store the energy instead of let it float away as waste heat. I believe Priuses and other electric vehicles use something like that.

"Dynamic braking" if you dump the power into resistors, "regenerative braking" if you feed it back "upstream" or into a storage device of some sort (battery or capacitor). Not a new thing - electric trains have been doing it for more than a century. Definitely useful - it adds significantly to the economy of an electric vehicle, especially under stop-and-go conditions. You're correct, the Prius does use it.

Sorry for the shoddy hand-sketch; it was a quick phone-pic from a quick sketch to pour over and not have to take up desk space with the real items...

What I'm hoping to do is graft them into the 'yet to be rebuilt' home theatre space (currently stashed away in some drum cases and rubbermaid bins.

Those beasties (wait until you see the actual units themselves.) came out of these floor standing high-end speakers with piezoelectric ribbon tweeters and something like two 12" or 15" main drivers, set into a half inch, 3/4" thick fiberboard (Masonite like) backplane.

I've not yet got the gumption up yet to reverse engineer the freq. cut-offs for these things

My daughter was in Dubai last weekend, went on a "Desert Safari" and was treated to a falconry display.
Along with riding a Rover over the sand! Al should like this shot.

Al does indeed like that shot! Mid-years IIA - very nice indeed.

I emailed the kid and asked if she had taken any other Rover photos. Al, here you go!

I think I can hear Al drooling from here...

So THAT'S what that "ga-loosh splort blort splap blap blip blip blip" noise was...

(Thank you Don Martin, for a treasure of noises.)

Red Shoulder hawks are back. They've been around for a few weeks, this was the first chance I had at photos. I was indoors and heard one making a racket, sounded close so I stepped outside to see the hawk in a tree in my back yard. Went back in, grabbed camera, and these were the best I was able to get. The hawk was high in the tree and not positioned for a good shot. A couple weeks back I saw a hawk working on the nest that is a couple houses over, keeping fingers crossed for this year!

Beautiful!

I had a nice encounter with a red-shoulder last weekend. I was out with another ham-radio operator, as part of an exercise our group was doing to survey stream levels and relay the information back to the city EOC. We had just checked and photographed the conditions at one bridge over Stevens Creek, when a huge hawk flew downstream towards us, landed in a tree, gave us a good looking-over, then flew back upstream out of sight. Unfortunately I was slow in getting my phone out and didn't get a picture.

There was a hawk and a crow who for some reason or another developed a personal feud. Sure, other crows would fuss and mob the hawk when it got too close to their place, but this one crow would go out of its way to harass the hawk whenever and wherever it saw it.

One day the hawk was just drifting along and minding its own business, when the crow saw it and took off after it. The hawk swooped around, and the crow stayed right on its tail. So the hawk did a sudden dive down under a fallen tree that had about a foot of clearance between it and the ground. The crow followed it. But what the crow didn't see was that after passing beneath the tree, the hawk performed a quick Immelmann. When the crow came out the other side, the hawk came down on top of it and smashed it into the ground in a cloud of black feathers. The hawk then sat there and ate crow, which it didn't seem to mind in the least.

Hansontoons wrote:Along with riding a Rover over the sand!

In case anybody ever wondered, having a crate of smashed extra-strength glowsticks leak all over your Land Rover does not favourably impact its desert night-time stealth characteristics.

So, who is feeling both hungry and adventurous?

That next-to-last item really sucks.

Good sausage? Permissible cheese? Pest sauce?

Either a sense of humour, or a lousy translator... Who will dare try to find out?

AmriloJim wrote:That next-to-last item really sucks.

PG-13, remember...

jwhouk wrote:

AmriloJim wrote:That next-to-last item really sucks.

PG-13, remember...

Ok, so I won't post the photo that shows entirely what was being snacked upon...
From my daughter's travels- South Africa safari a few years back.

lake_wrangler wrote:Good sausage? Permissible cheese? Pest sauce?

Either a sense of humour, or a lousy translator... Who will dare try to find out?

Well, grasshoppers are often considered pests, and the toasted grasshoppers I had at a bar in Vientiane were quite tasty. About halfway between Fritos and grilled shrimp, flavor-wise.

Not sure how you would make them into a sauce, though. Blend them with melted permissible cheese, I suppose.