TL Design I can't build

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#401
😱

gosh it's just like watching a movie. i'm on the edge of my seat...

i'm happy everything seems to be working out.

have you thought ahead to how you're going to mount these things on a stand? let me (us) know if we can help in that endeavor.

:nod:

keep warm!

/andrew - wore shorts today in san francisco.
 
#402
I think I have the mounting thing pegged. I'll save a little something for the Great Unveiling. But thanks for offering.

Here is a better picture of phase one. It's a wonder what natural lighting can do.
 

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#403
since you asked...

I do have a couple of questions about the final form of the enclosures.

1) Does the tweeter necessarily have to be ABOVE the woofer? Does it have to be in ANY sort of alignmnent with the woofer at all?

2) With regard to the tweeter: how do I determine phase placement? Where has this been discussed on this forum? Vifa P17-WG-00-06 and Vifa D27-TG-05-06. It's very easy for me to recess the tweeter from the woofer, but how much?

3) With regard to wiring the xover to the drivers: how much soldering do I HAVE to do, if any at all? **Edit** The crossover is already assembled, a pre-fab dealie done to spec by Madisound.

Thanks,

Dave
 
#404
If Madisound did the crossover, it probably would be best to call them and ask these questions. Driver placement can affect behavior around the crossover frequency. If Madisound is vague, it probably is a good idea to put the tweeter abutting the top of the woofer.

By the way, what is the crossover point?

The tweeter is customarily placed above the woofer. However, some Transmission Lines find it necessary to have the woofer above the tweeter, and nobody has yelled Bloody Blue Murder about it yet. Some well regarded speaker systems have the tweeter flush with the front of the woofer cone, but offset from the centerline, inward slightly-like an inch or so-toward the other speaker. However, I have never heard of a tweeter directly on the side of the woofer, unless you are talking center channel, line arrays or planar.

If you want to offset the speaker front-to-back, the normal thing is to set it so the dome of the tweeter is on the same plane as the dustcap of the woofer. I have always suspected that the ideal situation is to line up the dome so that it sits at a place in between the plane of the dustcap and the plane of the front of the woofer cone. However, I have not conducted tests.

As long as you have some adjustability here, why not try different tests? One of the Electrostatic pioneers-I am not sure which-back in the sixties made an electrostatic woofer and an electrostatic tweeter, which sat above it. He just kept moving the tweeter back and forth until he achieved the clearest sonic image. Since I imagine the tweeter is going on the end of some 2" PVC pipe stuck into the Tee, (I'm just guessing here), I think a little experimentation would be easy to do and would add some pizzaz to the project.
 
#405
Thanks, Kelticwizard, for the info. I'm not quite sure, but I think it crosses over at 2kHz.

Here's phase 2 complete. No problems so far. The segment on the far left gave me just the slightest argument, and I think it may be a 16th of an inch off one way or the other. My marks mysteriously would not line up again...

1/16th is no biggie.

Dave

PS--oops, a leaf sneaked into the pic. covers the segment in question
 

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#408
kelticwizard said:
Some well regarded speaker systems have the tweeter flush with the front of the woofer cone, but offset from the centerline, inward slightly-like an inch or so-toward the other speaker.
Click to expand...

Below is an example of what I meant by that statement-the ScanSpeak Reference Monitor.

Of course, you can also line the tweeter slightly behind the plane of the front of the woofer cone-that is another variation.
 

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#409
Phase3c

I spread the epoxy with my finger until it created a seal. I can add coats of epoxy until I'm satisfied.

This allowed me to use a thin piece of cardboard to seal the tee-top, a strategy which will give me room to store the crossover components.
 

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#411
I like the concept of storing the components in that compartment very much.

One thing-I would advise that the piece that seals the top from the outside to be somewhat stronger than a piece of cardboard, though I do believe the PC7 will stiffen that quite a bit.

It is one thing to describe something theoretically, it is another to do the steps to bring it to completion, to make the little decisions necessary to actually make something happen. Now that I see all those pieces on the floor, I must admit that you seem to be on schedule to completing a rather daunting task!!! :bigeyes: :bigeyes:

by kneadle
PS--oops, a leaf sneaked into the pic.
Click to expand...

Hey, if you're going to build a giant caterpillar, you gotta expect him to eat something! 😀 😀
 
#412
kelticwizard said:
The tweeter is customarily placed above the woofer. However, some Transmission Lines find it necessary to have the woofer above the tweeter, and nobody has yelled Bloody Blue Murder about it yet. Some well regarded speaker systems have the tweeter flush with the front of the woofer cone, but offset from the centerline, inward slightly-like an inch or so-toward the other speaker. However, I have never heard of a tweeter directly on the side of the woofer
Click to expand...

I always try to offset the tweeter from the midbass centerline... below casues a different tilt in the XO lobes. And the speaker pictured has a good rationale for side by side placement:

An externally hosted image should be here but it was not working when we last tested it.


I
f you want to offset the speaker front-to-back, the normal thing is to set it so the dome of the tweeter is on the same plane as the dustcap of the woofer. I have always suspected that the ideal situation is to line up the dome so that it sits at a place in between the plane of the dustcap and the plane of the front of the woofer cone.
Click to expand...

This is the best scheme to get you in the ballpark if you are only using the drivers physical construction. The actual acoustic centre can be anywhere in the speaker and can move around with frequency.

To nail it you need some test kit. Setup with the XO and the tweeter wired out of phase you move it back & forth until you have the largest null in the FR. At higher freq this is very sensitive to mic position.

dave
Click to expand...
 
#413
kelticwizard said:
One thing-I would advise that the piece that seals the top from the outside to be somewhat stronger than a piece of cardboard, though I do believe the PC7 will stiffen that quite a bit.
Click to expand...

The epoxy/cardboard seal is actually much thicker than the PVC wall. And if I need more, I can always add more epoxy, or even cut a piece of wood to fit underneath the cardboard. The key was sealing it while preserving the space above.

Now that I see all those pieces on the floor, I must admit that you seem to be on schedule to completing a rather daunting task!!! :bigeyes: :bigeyes:
Click to expand...

It's a little surreal for me, too. They should be completely done by next weekend. Watch for a post called "Spiral shaped enclosures..."


Hey, if you're going to build a giant caterpillar, you gotta expect him to eat something! 😀 😀
Click to expand...

Heh heh. I'm building caterpillars!

Thanks,

Dave
 
#416
kneadle said:
Which test kit for a low-budget amateur who likes doing it? I'm low-budget and I like building speakers and stuff...
Click to expand...

If you are running windoz there is a free program -- Speaker Workshop? -- that does all sorts of tricks. I understand the UI can be somewhat obtuse and that it is a good idea to build a Wallin jig.

Me the dyed in the wool mac guy is even negotiating a free PeeCee so i can try it out.

dave
 
#417
Speaker Workshop sure has the right price. I can attest to the goofy UI, but eventually you can figure it out. All you need is a decent mike. ~$10 in parts if you aren't afraid to make it yourself. I've been using SW, and it has been pretty good so far for frequency response measurments -- That's all I've tried.
 
#419
kelticwizard said:
..... Since I imagine the tweeter is going on the end of some 2" PVC pipe stuck into the Tee, (I'm just guessing here), I think a little experimentation would be easy to do and would add some pizzaz to the project.
Click to expand...


ok, paint me pink and call me goofy, but wouldn't it be neat if the tweeter was mounted on the end of one of the caterpillar's 'antennae'? i suppose you could have two tweeters, but i guess that's just not done.

/andrew
 
#420
I don't understand why you don't just get a pvc cap to cover the crossover? I doubt that a cap will cost more than 4-5 dollars... and it sure will look better than a cardboard cover.. and it will be easy to remove if you need to modify the crossover.
 
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