Line Arrays

[djdube525]

Does cable geometry (twisting conductors) affect inductive reactance?

What affect does inductive reactance have on signal passing through the cable?

FWIW... if ya want to geek out...

Here's a calculator for finding the inductance (L) of two parallel lines which can then be used to find the Reactance which is equal to 2*PI*f*L where f = frequency (more info here).

[steve]

Thanks steve.
So in a feedback loop wewant short untwisted conductors.  Phase compensation with cap would not help because it rotates phase in same direction as the twisted conductor capacitance? Usually the ground leg is separated anyway.

It might sound good Rich, but no, you want only the capacitance that was originally designed in the feedback loop. Too much or too little will negatively affect phasing of the feedback signal.

But on speaker wires, I always keep the capacitance minimal.

525, yes, in general, paralleling inductors is similar to paralleling resistors.

Cheers
Steve

[richidoo]

Thanks Dave

steve, when you parallel 8 conductors in SC, how do you separate them mechanically to avoid capacitance.

[steve]

Thanks Dave

steve, when you parallel 8 conductors in SC, how do you separate them mechanically to avoid capacitance.

In my test setup, I just purchased either regular 18 gauge wire and cut to length. I have also purchased pairs of 18 gauge wire in common jacket and cut to length. Parallel the pairs together.
Do Not connect one wire to + and the other wire of the pair to -.

I just laid all the + 8 wires together and a foot or so apart from the - wires. Capacitance will be minimal, near zero. If all the + wires are close together, not a huge deal. Same for all the - wires. The main point is to separate the + from the - speaker wires.

Cheers
Steve

[richidoo]

Right... no capacitance between the positives. Cool

[steve]

I was wondering how your project is progressing Rich? Is there anything unexpected that you have encountered that we could benefit from knowing?

Cheers
Steve

[richidoo]

Started working on this again. This is a big step of gluing the driver mounting nuts to the inside of the cabinet. Once the box is glued together, these nuts will not be accessible, so the gluing has to be in the right place and very strong so they don't pop off. Today I screwed all the drivers to the baffles in preparation for gluing the nuts to the inside of the baffles tomorrow. I will be gluing them with Loctite PL Construction urethane adhesive. It cures by reacting with moisture in the air, or water applied to bonded surfaces, and foams slightly. Very strong!!! I will just apply it around the edges of top of the nuts, nut under each nut, because I don't want to glue the mounting screws into the T-nuts.

6-32 x 1/2" button head hex screws and T-nuts.

Attached Pictures:
1. 16 drivers unpacked
2. Ready to assemble a strip of 16 drivers = half a speaker
3. 1 baffle assembled.
4. 4 baffles assembled, ready for T-nut glue
5. Closeup of driver assy
6. 64 drivers vs 4 drivers - which will win?
7. My daughter baked my BD cake(s) I'm 13yo

[djdube525]

Attached Pictures:
6. 64 drivers vs 4 drivers - which will win?

This doesn't seem like a fair fight... Lord Vader appears to be using the force to defend the current setup... 


Nice progress Rich!

[Nick B]

Started working on this again. This is a big step of gluing the driver mounting nuts to the inside of the cabinet. Once the box is glued together, these nuts will not be accessible, so the gluing has to be in the right place and very strong so they don't pop off. Today I screwed all the drivers to the baffles in preparation for gluing the nuts to the inside of the baffles tomorrow. I will be gluing them with Loctite PL Construction urethane adhesive. It cures by reacting with moisture in the air, or water applied to bonded surfaces, and foams slightly. Very strong!!! I will just apply it around the edges of top of the nuts, nut under each nut, because I don't want to glue the mounting screws into the T-nuts.

6-32 x 1/2" button head hex screws and T-nuts.

Attached Pictures:
1. 16 drivers unpacked
2. Ready to assemble a strip of 16 drivers = half a speaker
3. 1 baffle assembled.
4. 4 baffles assembled, ready for T-nut glue
5. Closeup of driver assy
6. 64 drivers vs 4 drivers - which will win?
7. My daughter baked my BD cake(s) I'm 13yo

Hmmm....a picture of you when you were 17 and now you are 13?? Is there a pattern here??
Congrats!
Nick

[Bob in St. Louis]

Nice cupcakes! 

[richidoo]

Thanks! They were yummy!

I got the T-nuts glued on today. That PL adhesive is really something.
Start building the cabinets tomorrow.

[steve]

Thanks! They were yummy!

I got the T-nuts glued on today. That PL adhesive is really something.
Start building the cabinets tomorrow.

3 weeks later, and the suspense is continuing to build. 

Cheers

Steve

[richidoo]

Aha! Thanks for another wake up call Steve! I wouldn't make any progress without you!

You're intuition must be itchy cuz I'm actually already working on it today. I'm regluing the T nuts with CA glue because the PL construction adhesive that I used before is very strong and tough, but it doesn't wick under the TNuts to make a good enough joint. It's more like taping them on from above. I could only glue one side of the TNuts with PL while the drivers screwed down to hold the nuts in place, so some of the TNuts could rock a little on the other, loose side. The CA seeps under and glues it tight. I'm using Bob Smith medium viscosity 15 second cure, but on the rough side of the masonite it cures very slowly, but it's solid after 10 minutes. Luckily I haven't glued any fingers together yet, but there's still one baffle left. I like the first wiff of CA, reminds me of happy days in my previous stress free hobby of model airplane building. But after a few minutes the smell gets old fast.

Also today I will drill 4 small holes in each of the 64 divider panels that go between each driver, holes to allow the hookup wires to pass through. Some of the panels need less holes, according to the wiring schematic, but the most holes any panel needs is 4, so I'm drilling 4 in all of them, then I'll fill the unused holes after the hookup is done. That's easier than gluing each divider panel in a "correct" position, and messing it up. Also allows changing the wiring schematic if I already messed that up but don't know it yet.   Since all the drivers move the same, in same volume chambers, there shouldn't be any air movement through the holes, but I'll seal them up anyway, and the wires through the holes. Once the holes are drilled I can start the sexy job of gluing up the boxes.

Edit: My wife wants me to finish these so she can hear what all this work is for. So I am motivated to show it off for my biggest fan and that should accelerate my progress. Just don't hold your breath! 

[djdube525]

Edit: My wife wants me to finish these so she can hear what all this work is for. So I am motivated to show it off for my biggest fan and that should accelerate my progress. Just don't hold your breath! 

Ahh... the single biggest motivator of projects... the Mrs... 

not speaking from any recent experience...

[Nick B]

Aha! Thanks for another wake up call Steve! I wouldn't make any progress without you!

You're intuition must be itchy cuz I'm actually already working on it today. I'm regluing the T nuts with CA glue because the PL construction adhesive that I used before is very strong and tough, but it doesn't wick under the TNuts to make a good enough joint. It's more like taping them on from above. I could only glue one side of the TNuts with PL while the drivers screwed down to hold the nuts in place, so some of the TNuts could rock a little on the other, loose side. The CA seeps under and glues it tight. I'm using Bob Smith medium viscosity 15 second cure, but on the rough side of the masonite it cures very slowly, but it's solid after 10 minutes. Luckily I haven't glued any fingers together yet, but there's still one baffle left. I like the first wiff of CA, reminds me of happy days in my previous stress free hobby of model airplane building. But after a few minutes the smell gets old fast.

Also today I will drill 4 small holes in each of the 64 divider panels that go between each driver, holes to allow the hookup wires to pass through. Some of the panels need less holes, according to the wiring schematic, but the most holes any panel needs is 4, so I'm drilling 4 in all of them, then I'll fill the unused holes after the hookup is done. That's easier than gluing each divider panel in a "correct" position, and messing it up. Also allows changing the wiring schematic if I already messed that up but don't know it yet.   Since all the drivers move the same, in same volume chambers, there shouldn't be any air movement through the holes, but I'll seal them up anyway, and the wires through the holes. Once the holes are drilled I can start the sexy job of gluing up the boxes.

Edit: My wife wants me to finish these so she can hear what all this work is for. So I am motivated to show it off for my biggest fan and that should accelerate my progress. Just don't hold your breath! 

This is a great example of what I'm trying to preach! Men, stand up for yourselves! You are the king of the ...what?? I'm busy right now!! I can't...really, I don't want to... sorry. Have to go, the wife is calling...