Banned
Joined 2002
Nice,
The boards I purchased from Kristijan use the protection zeners on the input also. Nice feature, hope it is never needed. I need to make a business trip to start stuffing the boards.
Is this one of your winter projects?
O/T Someone I know recommended using the Jensen 4 pole caps early this week for power supply filtering. I looked around to source some. What I found was a shock. 49.00 each. There is a nice 10,000 ufd 40v that would be perfect for a Mini A. Looks good on paper.
George
MikeW said:
The boards I purchased from Kristijan use the protection zeners on the input also. Nice feature, hope it is never needed. I need to make a business trip to start stuffing the boards.
Is this one of your winter projects?
O/T Someone I know recommended using the Jensen 4 pole caps early this week for power supply filtering. I looked around to source some. What I found was a shock. 49.00 each. There is a nice 10,000 ufd 40v that would be perfect for a Mini A. Looks good on paper.
George
Sheetrock travails are done for the moment, thank goodness. Now I'm down to scrubbing the concrete floor on my hands and knees. I hope to be done with that tomorrow. Then I get to move all the goodies back in and perhaps get some R&D done on a few whatnots that I've got in mind.
I hadn't realized anyone was doing a Mini-A board. They're cute!
Now, the funny thing about this is that I've got this unrequited itch to build some bi-amped, self-powered speakers like I think I mentioned in the original thread...and the Mini-A would be ideal for a tweeter amp...
Grey
I hadn't realized anyone was doing a Mini-A board. They're cute!
Now, the funny thing about this is that I've got this unrequited itch to build some bi-amped, self-powered speakers like I think I mentioned in the original thread...and the Mini-A would be ideal for a tweeter amp...
Grey
Scrubbing concrete? Buy a gallon of muriatic acid and a plastic bristled push broom. Turn on a fan and im sure you can figure out the rest. Do your self a favor though and spray anything in the house containing iron with some thin oil first.
A guy that came into the hardware store I work at wanted to do exactly what I just said. He wouldnt take my advice not to try it, so I sold him a gas mask and suggested the oil, and saluted him on the way out. I consider it evolution in progress.
As for the mini-A board, I would love to get a pair from someone professionaly made, but I have to have exact spacing on the mosfets because the heatsinks are already drilled and tapped. Maybe one day I will get around to finishing it...
-Chris
A guy that came into the hardware store I work at wanted to do exactly what I just said. He wouldnt take my advice not to try it, so I sold him a gas mask and suggested the oil, and saluted him on the way out. I consider it evolution in progress.
As for the mini-A board, I would love to get a pair from someone professionaly made, but I have to have exact spacing on the mosfets because the heatsinks are already drilled and tapped. Maybe one day I will get around to finishing it...
-Chris
Says here:
"Contains Sodium Metasilicate Pentahydrate and Sodium Carbonate. Avoid contact with skin, eyes, and mucous membrances..."
Actually, it occurs to me that I'd better stop or Rodd will get it in his head that I'm encouraging newbies to snort this junk up their noses and SinBin me again. Harrumph! Don't ask me what I think of the way the site's being run...I might answer.
HCl (aka Muriatic Acid) is useful stuff and I happen to have a gallon on hand, but what I don't have is good ventillation. My Mad Scientist Laboratory is in the basement and there's precious little ventillation down here, even with fans. This stuff doesn't make noxious fumes. Add to that the fact that it's old and I want to use it up to clear more shelf space and it seems like a good time to scrub.
As for the hands and knees part, I've got to get up under built-in shelving and such. Elseways, I'd use a pushbroom like I did in the brewery.
Two output devices, eh? Now, that's interesting.
Okay, here's what I've been thinking. I did Ariels and ME-2s for the 5.1 AV system upstairs. Well, actually it's 5.3, but let's not get picky. Anyway, the point is that those tweeters come in pairs, right? I couldn't stand it. I went ahead and bought woofers and stuff to go with the spare tweeter. So I've got this center channel speaker up front...and a spare ME-2. In which I just happened to wire the drivers out separately so as to be able to get to all three drivers. (Yes, I know what's-his-face likes the crossover mounted externally, but I didn't wire the woofers in parallel until I got outside the box in case I wanted to do something kinky, like give each woofer its own amplifier.) So, supposing we were to put a Mini-A on the tweeter and an Aleph-X on the bottom. Which is part of what led to the whole Mini-A/Aleph-X thing anyway.
Well!
Okay, then I started thinking about the bottom end, which is a little on the puny side. Then I turn around and...lo...there are those nifty old KEF B-139s, just begging to go in and carry the load from, say, 150 Hz on down. So then we go for another Aleph-X, or perhaps just a straight X. Now we're tri-amped.
Then, just to be really excessive, what about another B-139 below that (i.e. roughly 40-50Hz, which is where they poop out unless you put them in a transmission line), crossed over with an LP filter at about 20Hz, making that the subwoofer.
An LP at 20? Huh? I thought you wanted something that would cross over at 50!
No, I'm not nuts, despite what some have tried to tell you.
Suppose we use a driver--any driver--in a sealed box that's -3 @ 50. Coming in from the right, we have a straight line at 200...100...a little droop...then -3 dB at 50...then a typical 12 dB/oct rolloff. Just for a moment pretend that it's not a driver, it's a high pass filter. What would happen if we added a low pass at 100? We'd get a bandpass, right? It'd be -3 dB at 50Hz (HP) and -3 dB at 100Hz (LP) and kinda-sorta flat in between. In reality, the droopiness would make it rounded, but you get the idea.
Take it one step further. Slide that low pass filter down to some arbitrary frequency, say, 20 Hz. Put on your thinking cap and we'll do this in three parts.
First, the under-20Hz region. Add a flat line (the pass band from the low pass filter) and a sloping line (the falling response from the driver), and what do you have? Well, you've still got a falling response below 20 Hz. They sum to a low pass.
Next, the above 50 region. Add a flat line (in this case the driver response), and a sloping line (the low pass slope from the filter) and what do you get? Right. A high pass function. The response is falling.
Now here's what drives people nuts. Between 20Hz and 50Hz, you've got two falling responses, one HP and one LP. One slopes from right to left and the other one from left to right. What happens when you sum those two? A flat line.
We just took a driver that effectively stops at 50Hz and made a subwoofer out of it. Without a boost circuit. Without oscillations. Without feedback, feedforward, or other manipulations. The really cute thing about all this is that the driver still cuts out before it gets to the really ugly subsonics. It's flat (we're assuming that the driver/cabinet combination has a smooth rolloff) in the middle. And it rolls off nicely in time to meet the 'real' woofer. All with one, count 'em, one crossover slope! Less phase shift. Less circuitry. Automatic matching between the woofer and the subwoofer in tonality and crossover point.
Neat.
Need I say Rushmore?
Grey
"Contains Sodium Metasilicate Pentahydrate and Sodium Carbonate. Avoid contact with skin, eyes, and mucous membrances..."
Actually, it occurs to me that I'd better stop or Rodd will get it in his head that I'm encouraging newbies to snort this junk up their noses and SinBin me again. Harrumph! Don't ask me what I think of the way the site's being run...I might answer.
HCl (aka Muriatic Acid) is useful stuff and I happen to have a gallon on hand, but what I don't have is good ventillation. My Mad Scientist Laboratory is in the basement and there's precious little ventillation down here, even with fans. This stuff doesn't make noxious fumes. Add to that the fact that it's old and I want to use it up to clear more shelf space and it seems like a good time to scrub.
As for the hands and knees part, I've got to get up under built-in shelving and such. Elseways, I'd use a pushbroom like I did in the brewery.
Two output devices, eh? Now, that's interesting.
Okay, here's what I've been thinking. I did Ariels and ME-2s for the 5.1 AV system upstairs. Well, actually it's 5.3, but let's not get picky. Anyway, the point is that those tweeters come in pairs, right? I couldn't stand it. I went ahead and bought woofers and stuff to go with the spare tweeter. So I've got this center channel speaker up front...and a spare ME-2. In which I just happened to wire the drivers out separately so as to be able to get to all three drivers. (Yes, I know what's-his-face likes the crossover mounted externally, but I didn't wire the woofers in parallel until I got outside the box in case I wanted to do something kinky, like give each woofer its own amplifier.) So, supposing we were to put a Mini-A on the tweeter and an Aleph-X on the bottom. Which is part of what led to the whole Mini-A/Aleph-X thing anyway.
Well!
Okay, then I started thinking about the bottom end, which is a little on the puny side. Then I turn around and...lo...there are those nifty old KEF B-139s, just begging to go in and carry the load from, say, 150 Hz on down. So then we go for another Aleph-X, or perhaps just a straight X. Now we're tri-amped.
Then, just to be really excessive, what about another B-139 below that (i.e. roughly 40-50Hz, which is where they poop out unless you put them in a transmission line), crossed over with an LP filter at about 20Hz, making that the subwoofer.
An LP at 20? Huh? I thought you wanted something that would cross over at 50!
No, I'm not nuts, despite what some have tried to tell you.
Suppose we use a driver--any driver--in a sealed box that's -3 @ 50. Coming in from the right, we have a straight line at 200...100...a little droop...then -3 dB at 50...then a typical 12 dB/oct rolloff. Just for a moment pretend that it's not a driver, it's a high pass filter. What would happen if we added a low pass at 100? We'd get a bandpass, right? It'd be -3 dB at 50Hz (HP) and -3 dB at 100Hz (LP) and kinda-sorta flat in between. In reality, the droopiness would make it rounded, but you get the idea.
Take it one step further. Slide that low pass filter down to some arbitrary frequency, say, 20 Hz. Put on your thinking cap and we'll do this in three parts.
First, the under-20Hz region. Add a flat line (the pass band from the low pass filter) and a sloping line (the falling response from the driver), and what do you have? Well, you've still got a falling response below 20 Hz. They sum to a low pass.
Next, the above 50 region. Add a flat line (in this case the driver response), and a sloping line (the low pass slope from the filter) and what do you get? Right. A high pass function. The response is falling.
Now here's what drives people nuts. Between 20Hz and 50Hz, you've got two falling responses, one HP and one LP. One slopes from right to left and the other one from left to right. What happens when you sum those two? A flat line.
We just took a driver that effectively stops at 50Hz and made a subwoofer out of it. Without a boost circuit. Without oscillations. Without feedback, feedforward, or other manipulations. The really cute thing about all this is that the driver still cuts out before it gets to the really ugly subsonics. It's flat (we're assuming that the driver/cabinet combination has a smooth rolloff) in the middle. And it rolls off nicely in time to meet the 'real' woofer. All with one, count 'em, one crossover slope! Less phase shift. Less circuitry. Automatic matching between the woofer and the subwoofer in tonality and crossover point.
Neat.
Need I say Rushmore?
Grey
- Status
- This old topic is closed. If you want to reopen this topic, contact a moderator using the "Report Post" button.