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Good 8" FR for Transmission Line
Good 8" FR for Transmission Line
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Old 15th January 2018, 10:25 PM   #11
CLAD is offline CLAD  United States
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Thanks guys. I will look into them.

Sorry for the absence of details. Sometime you just have to ask a simple question, because sometimes there really is a simple answer!

My project is a little more complicated than I initially wanted to talk about, but it's basically going to be a folded TL made of two concentrically arranged pipes. The FR driver will be mounted at the end of the outer pipe, and it will fire toward the ceiling. My plan is to mount a Hyperbolic cone above the FR as a waveguide to direct the energy laterally. It's not really all that original. There is quite a bit of imitation happening, and I'm not really trying to hit any specific audiophile mark. It just sounds like fun.

Obviously with what I doing with the waveguide, and not planning to use any other HF supplementation, I want the HF of the FR driver to be sufficient on it's own.

As far as bass, I'm happy if it makes it to 40-50 cycles.

I never thought much about the driver size, but the cutout hole has to be smaller than the 8" inner diameter if my inside pipe, in order to make a seal between the Baffle plate and the pipe.

I plugged two drivers into Hornresp (Dayton PS220, and Wild Burro Betsy). I'm still figuring out the program, but I liked Betsy a little better.

Thanks again for the suggestions. I'll pug in seral more drivers in, and if the project makes it to construction phase I'll post some photos.

Chris
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Old 15th January 2018, 10:32 PM   #12
planet10 is offline planet10  Canada
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Good 8" FR for Transmission Line
Quote:
Originally Posted by CLAD View Post
It's not really all that original.
Exactly that, but for a bigger driver, years (probably decades) ago in speaker builder magazine. A speaker for a bass player.

Quote:
but the cutout hole has to be smaller than the 8" inner diameter if my inside pipe
8” ID will want a smaller driver than an 8”. And you need to consider using a driver offset — a big advantage. So you will want to load the driver in the middle of the line and not end load it. Given that you might want to make it a stepped “voigt” with the terminus off the far end of the big pipe. I have a picture somewhere (of both that and the SB design)

dave
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Old 15th January 2018, 11:10 PM   #13
chrisb is offline chrisb
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CLAD - based on the description in your post #11 above, I'd certainly recommend the 10.3 over the 10P.
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Old 15th January 2018, 11:13 PM   #14
CLAD is offline CLAD  United States
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How about a coaxial?

Does that get discussed on the FR forum?
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Old 16th January 2018, 12:01 AM   #15
planet10 is offline planet10  Canada
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Good 8" FR for Transmission Line
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How about a coaxial?
That gets much more complicated with the reflector... one needs to then have 2 relectors -- look up the Morrison.

dave
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Old 16th January 2018, 12:11 AM   #16
planet10 is offline planet10  Canada
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Good 8" FR for Transmission Line
Jan 1990 Speaker Builder

Click the image to open in full size.

dave
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Old 16th January 2018, 12:15 AM   #17
CLAD is offline CLAD  United States
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Quote:
Given that you might want to make it a stepped “voigt” with the terminus off the far end of the big pipe. I have a picture somewhere (of both that and the SB design)
Thanks Dave, I would like to see the image, but unless it shows something different than what I think, doing the Voigt Pipe as I understand it, doesn't allow me to "Omni" the speaker. The 360 degree radiation pattern and the Hyperbolic Cone is the fundamental idea of this design, and everything else is a compromise to achieve that!

I recognize that what I'm doing is not ideal TL architecture, and I'm capable of building a better performing speaker, but this is what I want to try because I think it's going to be fun. I also think I might learn a thing or two!

I know I haven't described it in great detail. It's just an 8" pipe inside of a 10" pipe, with a cap on either end and a driver firing out of one of the caps,(I thought about using 3 pipes, but I revised it in the spirit of simplicity). If you have some ideas how I could improve on that concept, but retain the "Omni" capability, I would certainly spend a little bit of time trying to figure out if I could use them!

Thanks,

Chris
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Old 16th January 2018, 12:18 AM   #18
CLAD is offline CLAD  United States
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That photo is not the Voigt Pipe with an offset driver.

That's the Archetype for my idea it looks like!
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Old 16th January 2018, 02:02 AM   #19
astrojet is offline astrojet
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Quote:
Originally Posted by planet10 View Post
For the single driver ML-TL just divide the MTM in half vertically and place the centre of the driver at the space between the 2 12pw. Getting the A5.2 housed would get tricky with a side pod, or use the folded version.

dave
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Old 16th January 2018, 02:47 AM   #20
planet10 is offline planet10  Canada
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Good 8" FR for Transmission Line
Quote:
Originally Posted by CLAD View Post
Thanks Dave, I would like to see the image, but unless it shows something different than what I think, doing the Voigt Pipe as I understand it, doesn't allow me to "Omni" the speaker. The 360 degree radiation pattern and the Hyperbolic Cone is the fundamental idea of this design, and everything else is a compromise to achieve that!
Sure it remains possible. 8” pipe + 12” pipe give ~50in2 1st section | driver | 63in2 2nd section. terminus at the bottom — i haven’t drawn the terminus, it is in the annulus, likely a bunch of holes drilled, or a bunch of plumbing pipes of appropriate diameter (it will need to be modelled.

The sketch only shows the relation of the 2 pipes and where the driver would be mounted facing upwards. It is possible to use Saunders trick by use something like 2x4s cut on an angle lengthwise to decrease the cross-section of the “pointy” end of the pipe and to mitigate the abrupt change in cross-section at the driver end. It would need to sit proud of the floor on feet to give the terminus room — actually thinking about that the annulus at the bottom could be left open and the mass-loading vent formed with an appropriately designed base.

That should give you some ideas to think on. Th esktch is about 60” long using 8 & 12” pipe.

dave
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File Type: png Cyclindical-voigt-sketch.png (45.5 KB, 160 views)
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