Its been a while since I was her but now am back working on my amp. I'm hoping someone has an idea to help solve my problem. It's a standard push-pull tube amp, 10 watts/channel.(EF86 to a 12ax7 to 2 EL84s) with negative feedback.
I have 10ohm wirewound resistors across the 8 home output of the transformers and each channel will oscillate except the channel with the oscilliscope probe across the 8ohm output. Move the probe to the oscillating channel and it stops and the other channel oscillates.
I'm looking at it with a textronix 2215A a dual trace oscilliscope.
What is going on?
I have 10ohm wirewound resistors across the 8 home output of the transformers and each channel will oscillate except the channel with the oscilliscope probe across the 8ohm output. Move the probe to the oscillating channel and it stops and the other channel oscillates.
I'm looking at it with a textronix 2215A a dual trace oscilliscope.
What is going on?
Looks like you posted in the wrong forum in a thread unrelated to your sexual orientation
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Using a Co-Ax with a Paraline
Hello, Stan Rawcliffe here.
I have an Electro Voice Centurion speaker cabinet that my father built in 1958/1959 that is falling apart. I am figuring out how to rebuild it and being as it is a tapped horn, I realized that a Paraline is a perfect method of injecting the sound into the horn. Then the idea of using a co-ax to drive a Paraline came up.
Here’s the set up for my question: What if you used a large co-ax, such as a Great Plains Audio 604, but replaced the HF horn with a pipe that injected the pressure wave into the Paraline at a point equidistant from the LF driver? By playing with the LF phase plug you can adjust the distance/timing of the LF signal path to match the HF signal path and the LF and HF would be in perfect sync throughout the entire audio spectrum, at least until the drivers break up. You could design your crossover for any frequency you want. If you bi-amped the cabinet, you could adjust the crossover point up and down to find out what sounds good, no testing required. There’d be lots of testing to get to this point for sure.
So here’s the question: What happens when you use a HF compression driver in a 40 HZ horn, especially considering that it starts in the Paraline?
Thanks, Stan
Hello, Stan Rawcliffe here.
I have an Electro Voice Centurion speaker cabinet that my father built in 1958/1959 that is falling apart. I am figuring out how to rebuild it and being as it is a tapped horn, I realized that a Paraline is a perfect method of injecting the sound into the horn. Then the idea of using a co-ax to drive a Paraline came up.
Here’s the set up for my question: What if you used a large co-ax, such as a Great Plains Audio 604, but replaced the HF horn with a pipe that injected the pressure wave into the Paraline at a point equidistant from the LF driver? By playing with the LF phase plug you can adjust the distance/timing of the LF signal path to match the HF signal path and the LF and HF would be in perfect sync throughout the entire audio spectrum, at least until the drivers break up. You could design your crossover for any frequency you want. If you bi-amped the cabinet, you could adjust the crossover point up and down to find out what sounds good, no testing required. There’d be lots of testing to get to this point for sure.
So here’s the question: What happens when you use a HF compression driver in a 40 HZ horn, especially considering that it starts in the Paraline?
Thanks, Stan
Well, it's my understanding is a tapped horn is a horn with the driver placed on the side as opposed to the end. Here is a link to a tapped horn tutorial that has a diagram a few scrolls down.
Simple Tapped Horn Tutorial using Hornresp
The EV Centurion has the same configuration. Search on electro voice centurion which will pop up a link to automatically download of a set of plans from the EV Museum Site from the '50s.
Simple Tapped Horn Tutorial using Hornresp
The EV Centurion has the same configuration. Search on electro voice centurion which will pop up a link to automatically download of a set of plans from the EV Museum Site from the '50s.
Earl
I admit to not knowing much, but I thought a tapped horn has the driver on the side of the horn. Yes, the Centaurions horn is folded up and the driver has a semi-circular throat in the baffel for the sound to enter the horn. There is an odd shaped box, perhaps a couple of cubic feet, in back of the driver, and the horn folds around it.
Regardless, a Paraline seems to me to be a great way to inject the sound into the horn I am rebuilding whether it's a tapped horn or not.
Stan
I admit to not knowing much, but I thought a tapped horn has the driver on the side of the horn. Yes, the Centaurions horn is folded up and the driver has a semi-circular throat in the baffel for the sound to enter the horn. There is an odd shaped box, perhaps a couple of cubic feet, in back of the driver, and the horn folds around it.
Regardless, a Paraline seems to me to be a great way to inject the sound into the horn I am rebuilding whether it's a tapped horn or not.
Stan
Won't work.
I found the Centurion plans, and it's basically a front loaded horn, folded into a snail, with a midrange, tweeter and super tweeter.
So basically it's set up like this:
1) There's a horn loaded woofer that fires down and exits out of the back of the enclosure.
It looks like this snail horn, but picture if the entire thing was upside down. (Mouth exits out the top of the back, instead the bottom of the front.)
2) On the front of the centurion (which would be the same panel as the BACK of the CV sub) there's a midrange, tweeter, and super tweeter.
If you tried to use a coax the midrange and tweeter frequency response would be completely wrecked by running through the bends in the horn.
The reason that it works in a Synergy or Unity horn is that there's no bends.
The reason that it (sorta) works in a Paraline is that there are bends, but the pathlength from throat to mouth is constant. It doesn't vary with angle. Well, theoretically at least
I think the peaks and dips in the measured response of the Paralines is because the sound doesn't radiate perfectly radially.
Thanks Patrick!
Your reply just gave me one of those "well duh" moments. As you often have said, 18,000 Hz is about 1/4". Sending HF into a bent LF horn is going to have HF bouncing around in all kinds of unpredictable ways.
The Centaurion is supposed to sit in a corner so the back room walls reflect the sound forward through the side ports.
My hope and the real reason I started asking today, is to use a Paraline in place of the semi-circular cutout/throat in my pops Centurion.
It seem that a Paraline that is perpindicular to the axis of the horn, with a deflector bouncing the sound up the horn, would be a perfect way to couple my woofer to my horn.
Am I barking up the wrong tree or will it work?
Something else I am wondering about is the derivation of the word "Paraline". I understand the "line" part but what does Para refer to.
Thanks for your help
Stan
Your reply just gave me one of those "well duh" moments. As you often have said, 18,000 Hz is about 1/4". Sending HF into a bent LF horn is going to have HF bouncing around in all kinds of unpredictable ways.
The Centaurion is supposed to sit in a corner so the back room walls reflect the sound forward through the side ports.
My hope and the real reason I started asking today, is to use a Paraline in place of the semi-circular cutout/throat in my pops Centurion.
It seem that a Paraline that is perpindicular to the axis of the horn, with a deflector bouncing the sound up the horn, would be a perfect way to couple my woofer to my horn.
Am I barking up the wrong tree or will it work?
Something else I am wondering about is the derivation of the word "Paraline". I understand the "line" part but what does Para refer to.
Thanks for your help
Stan
Stan,
"Para" bolic curve.
The Centurion horn has some fairly large frequency response problems even below 300 Hz, about where it crossed to PA re-entrant (folded) horns.
Mid/High frequencies going through that horn (the wall corners form the mouth of the horn) will have a terrible response.
Imagine a 1/3 octave EQ with alternate bands fully cut and boosted to get an idea of how bad it would be.
Hello
I think I need to back up a bit and introduce myself.
I have just jumped into the High Efficiency Speaker world, full of ignorance. As I said, my dad built this Centurion back in the late 50s and now it is a mess. I inherited it about 10 years ago and have committed myself to making it right for Douglas using modern materials and techniques. The only part that will move to the rebuilt cabinet is the front and top walnut skin. To that end, I am about a week from moving into my new shop. One big reason to build the shop is to rebuild my dads speaker, not the only one but a big one.
I realize that this isn't the right place for me to be doing this intro but my original interest was in using a Paraline to couple my woofer to my horn so thank you guys for your responses.
Oh my avatar is Dougs Centaurion.
Thanks
Stan
I think I need to back up a bit and introduce myself.
I have just jumped into the High Efficiency Speaker world, full of ignorance. As I said, my dad built this Centurion back in the late 50s and now it is a mess. I inherited it about 10 years ago and have committed myself to making it right for Douglas using modern materials and techniques. The only part that will move to the rebuilt cabinet is the front and top walnut skin. To that end, I am about a week from moving into my new shop. One big reason to build the shop is to rebuild my dads speaker, not the only one but a big one.
I realize that this isn't the right place for me to be doing this intro but my original interest was in using a Paraline to couple my woofer to my horn so thank you guys for your responses.
Oh my avatar is Dougs Centaurion.
Thanks
Stan
Attachments
Kindhornman
Whatever type of horn I have, I have a speaker stuck on the side of the horn. Looking at the picture in #673 the edge in the semi circle is a diffraction edge for the sound wave to bend around and head up the horn, ie. to bend the sound wave at right angles. As I figured out what was happening in a Paraline, it occured to me that a Paraline might be a perfect way to make that right angle turn in less space. The length of the Paraline would be same as the diameter of the woofer. It would add the woofers diameter to the overall length of the horn.
I am not really trying to recreate the Centurion. I want to do it better. Way better. I need to keep it looking as original as possible so I'll keep the skin but other than that I am going to gut it.
Thanks
Stan
Whatever type of horn I have, I have a speaker stuck on the side of the horn. Looking at the picture in #673 the edge in the semi circle is a diffraction edge for the sound wave to bend around and head up the horn, ie. to bend the sound wave at right angles. As I figured out what was happening in a Paraline, it occured to me that a Paraline might be a perfect way to make that right angle turn in less space. The length of the Paraline would be same as the diameter of the woofer. It would add the woofers diameter to the overall length of the horn.
I am not really trying to recreate the Centurion. I want to do it better. Way better. I need to keep it looking as original as possible so I'll keep the skin but other than that I am going to gut it.
Thanks
Stan
If it were me, this is what I would do:
1) Keep the original horn loading for the woofer.
2) Ditch the Centurion's midrange, tweeter, and super tweeter
3) Where those three drivers used to be, put a 5" B&C coaxial or a 5" BMS coaxial.
So you would have a three way. Midrange and tweeter duties handled by the coax, with horn loaded bass.
The main reason that the Paraline works is that the diameter of the horn at the horn bends is a fraction of a centimeter. And note that the Paraline *doesn't* work as well as a plain ol' waveguide, like the BMS or B&C coax. IE, use a Paraline if you are very short on space and you need it's very narrow vertical coverage.
But if you *don't* need narrow vertical coverage, just use a waveguide.
And this is coming from someone who's built about a dozen of these. They're definitely interesting devices, but don't use one if you don't need to. Danley's flagship is still the SH-50, I don't see the SBH-10 changing that situation any time soon.