My Three Pi Speakers Finished - AVS Forum
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post #1 of 29 Old 04-07-2012, 03:19 PM - Thread Starter
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Attached are two pictures of my completed Three Pi speakers. The cabinets are 3/4" MDF laminated in a special order deep blue high gloss laminate from Nevamar.

The room is in a rent house I'm living in while another house is being built, so try picturing them in a room with dark blue walls and no windows.

The sound is terrific. These are very accurate speakers that will produce more sound than you can stand with no strain at all. The actual speaker section is only 30", but I had them lengthened to 50" to bring the drivers to seated ear level.

I need at least one more subwoofer, and I think I will build two more Three Pis for surrounds. But, I'm not putting anything else in until I'm relocated.
LL
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post #2 of 29 Old 04-07-2012, 03:32 PM
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Those look awesome! Did you spray clearcoat?
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post #3 of 29 Old 04-07-2012, 04:06 PM
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Yeah, spill it already. We want all the details on your great looking build.
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post #4 of 29 Old 04-07-2012, 04:55 PM - Thread Starter
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Quote:
Originally Posted by Jay1 View Post

Those look awesome! Did you spray clearcoat?

No. That is a tough finish of some kind on the laminate. I had to order it that way.

Floyd

A lie can travel halfway around the world before the truth gets its shoes on. -- Mark Twain
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post #5 of 29 Old 04-07-2012, 08:27 PM
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Get some hex head screws from madisound, the silver screws stick out like a sore thumb

Two alpine sws-15d2 drivers for sale $150
erich kit + titanic MK3 $200

Want to measure your subwoofers? check out my dummies guide for a step by step process to Room EQ wizard
http://polaraudio.blogspot.com/2012/01/calibration.html
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post #6 of 29 Old 04-08-2012, 05:17 AM
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Or spray them black before installation

Very nice color!
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post #7 of 29 Old 04-08-2012, 07:17 AM
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Nice.
Like the laminate. Eliminates the whole problem of finishing.

T6

Clearwave 4TSE and 4CC build thread
http://www.avsforum.com/avs-vb/showt...1#post19489740
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post #8 of 29 Old 04-08-2012, 08:41 AM
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I really like the look of these. Very nice! Just out of curiosity, what was the cost of the laminate and how difficult was it to install?
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post #9 of 29 Old 04-08-2012, 02:52 PM
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Those look amazing
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post #10 of 29 Old 04-08-2012, 11:57 PM
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Nice.

Not to rain on your parade, but with the importance that Wayne places on minimizing lobing, why is aren't the horn and woofer closer together?

Noah
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post #11 of 29 Old 04-09-2012, 12:21 AM
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i didn't want to do any raining either noah, so let's cast it more as good info for future builders...

guys, designs such as this are optimized when the horn and the woofer are mated as close together as possible, as this creates the best possible accoustical summation of sound from two different point sources. the further the two sources go apart, the more you run into cancellations, lobing effects, and all kinds of other nasties...

i hate to sound negative because the design does so much very well. the spacing is kind of like moving from 93% to 95% of perfection, while most other designs might be down at 50% or something like that, so the build is very nice all things considered.

Listen. It's All Good.
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post #12 of 29 Old 04-09-2012, 07:26 AM
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Quote:
but with the importance that Wayne places on minimizing lobing, why is aren't the horn and woofer closer together?

Because Wayne designed the enclosure to have internal front-back, side-to-side braces installed between the waveguide and the woofer. I'm sure the crossover is designed for proper vertical lobe steering. Builders of the Three Pi design should follow the front baffle cutouts exactly for the crossover to work correctly.
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post #13 of 29 Old 04-09-2012, 10:58 AM
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His spacing looks pretty similar to what's shown on the Pi website?

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post #14 of 29 Old 04-09-2012, 11:01 AM
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Quote:
Originally Posted by bobgpsr View Post

Because Wayne designed the enclosure to have internal front-back, side-to-side braces installed between the waveguide and the woofer.

That can be done (I have) even with them butted right up next to each other, as there's still baffle material behind the horn and woofer mounting flanges.

Noah
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post #15 of 29 Old 04-09-2012, 06:49 PM
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The point is that Wayne Parham has designed the Three Pi crossover for the driver spacing as done by his plans for the Three Pi speaker baffle. It looks to me that Floydster followed that. If one does not follow that then one does not really have a Three Pi speaker - but rather something else that will need a custom desired crossover to get the correct vertical angle direction for the main response lobe. Closer driver spacing may make this design process easier in PCD but that redesign is not needed if one uses Wayne's Three Pi crossover design and implements the Three Pi enclosure to Wayne's plans. I trust Wayne's expertise with this. And yes, I have read his advice to Zilch (RIP), on minimizing driver separation.
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post #16 of 29 Old 04-10-2012, 01:12 PM
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Quote:
Originally Posted by noah katz View Post

Nice.

Not to rain on your parade, but with the importance that Wayne places on minimizing lobing, why is aren't the horn and woofer closer together?

Quote:
Originally Posted by LTD02 View Post

i didn't want to do any raining either noah, so let's cast it more as good info for future builders...

guys, designs such as this are optimized when the horn and the woofer are mated as close together as possible, as this creates the best possible accoustical summation of sound from two different point sources. the further the two sources go apart, the more you run into cancellations, lobing effects, and all kinds of other nasties...

i hate to sound negative because the design does so much very well. the spacing is kind of like moving from 93% to 95% of perfection, while most other designs might be down at 50% or something like that, so the build is very nice all things considered.


In general reducing the spacing between woofer/HF-horn is a good thing for the reasons you both stated above, but remember this is a "Fully Optimized" design that goes beyond the "general principles" of good speaker design. Increased (from minimum possible) spacing between the woofer/HF-horn was purposely implemented by Wayne in his 3pi speaker. This was done to reduce unwanted reflected sound energy to the listening room's ceiling that is outside of the 90x40 degrees design radiation pattern in the frequency range centered around the HF/Woofer crossover. The vertical null location caused by the HF/Woofer interaction was also optimized to be just outside the 90x40 degrees design vertical radiation pattern. From his pictures it appears that Floydster has implemented Wayne's optimized vertical driver spacing.


Cheers, Joe
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post #17 of 29 Old 04-10-2012, 05:42 PM
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there are many things that one can optimize. many would argue that it is more important to minimize the phase difference between the two drivers to the listener than whether the cancellations occur at a difference of 27 or 30 degrees outside the horn flare. if you always sit with your ears located exactly between the tweeter and the woofer centers (well, technically on the center lobe, which may be steared up slightly), then spacing isn't that important and you will have good phase. if you are above or below that point, phase will be improved by having the drivers as close together as possible.

Listen. It's All Good.
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post #18 of 29 Old 04-10-2012, 06:12 PM
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Well that's very surprising given how Wayne harangued Geddes about the perils of the greater C-Cdistance of round vs. rectangular elliptical horns.

And I don't see how such "optimization" could be such for all of the different room sizes and listening positions out there.

Quote:
Originally Posted by Muzikal-JRNE View Post

Increased (from minimum possible) spacing between the woofer/HF-horn was purposely implemented by Wayne in his 3pi speaker. This was done to reduce unwanted reflected sound energy to the listening room's ceiling that is outside of the 90x40 degrees design radiation pattern in the frequency range centered around the HF/Woofer crossover. The vertical null location caused by the HF/Woofer interaction was also optimized to be just outside the 90x40 degrees design vertical radiation pattern.


Noah
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post #19 of 29 Old 04-11-2012, 11:49 AM
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Hey guys. I asked Wayne to clarify his design choice for vertical driver spacing over on his Pi Speakers forum at AudioRoundTable. Below is the link to the thread:

http://audioroundtable.com/forum/ind...17297&start=0&


Cheers, Joe
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post #20 of 29 Old 04-11-2012, 03:11 PM
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so the driver spacing was a bracing choice...noah gets the prize.

Listen. It's All Good.
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post #21 of 29 Old 04-11-2012, 05:47 PM
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Why not use a piece angle iron for the brace between drivers? It would take less space and certainly be strong enough. Better yet, albeit more costly, weld a rectangular brace which also add stiffness to the other sides. You could use some heavy duty adhesive like Sikaflex or 5200 to secure it to the sides without fasteners.
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post #22 of 29 Old 04-11-2012, 06:45 PM
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Hey Roy andNoah,
Why don't you show us what you made lately. Just saying.
Josh

JoshK on most other audio forums
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post #23 of 29 Old 04-11-2012, 06:53 PM
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Just saying what? Just throwing ideas out there. What's the matter with that?
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post #24 of 29 Old 04-11-2012, 07:21 PM
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Quote:
Originally Posted by Muzikal-JRNE View Post

Hey guys. I asked Wayne to clarify his design choice for vertical driver spacing over on his Pi Speakers forum at AudioRoundTable. Below is the link to the thread:

http://audioroundtable.com/forum/ind...17297&start=0&

Fair enough, sounds like nothing's lost by the spacing, though I still don't get his bracing argument; even if you had to thin the brace right at the top of the woofer, you can get still get a full window brace in if you wanted.

Quote:
Originally Posted by AudioJosh View Post

Hey Roy andNoah,
Why don't you show us what you made lately. Just saying.
Josh

Here ya go; check out the c-c spacing on the fronts.
LL

Noah
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post #25 of 29 Old 04-12-2012, 12:16 PM
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Quote:
Originally Posted by LTD02 View Post

so the driver spacing was a bracing choice...noah gets the prize.

Not quite:
Quote:
Originally Posted by Wayne View Post

the vertical nulls are centered at approximately 35° above and 25° below the centerline. That's a 60° spread. Even the spacing between the inside edges of the nulls is further than 50° apart. So the forward lobe is perfectly clean through a nice tall 50° vertical arc. I like putting the nulls in this position - just outside the vertical beamwidth at HF. It punctuates the edge of the pattern in the crossover region, where the horn/waveguide would otherwise have little vertical control
...
is important to me that the center-to-center spacing is at least short enough that a crossover can be designed that simultaneously matches horizontal directivity and places vertical nulls outside the pattern. Even if the pattern widens in the vertical in the crossover region, the nulls shouldn't be so narrowly spaced that they make the crossover region have a forward lobe any smaller than the horn's vertical pattern at HF. My goal has always been to provide constant 90° horizontal beamwidth and 40° vertical beamwidth at HF, with nulls spaced at least that far apart.

My loudspeaker designs achieve these goals. They have sound sources placed close enough to keep the nulls outside that 40° arc. The horn/waveguide has constant 90° horizontal beamwidth and 40° vertical beamwidth. As a result, polars are much better.

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post #26 of 29 Old 04-12-2012, 02:32 PM
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"You could bring the woofer and tweeter closer together by an inch or so, but then you would have very little room for the cross-brace, which is a pretty important thing. Cut it too close, and the brace becomes ineffective because the thin baffle section is too weak."

what wayne is saying is that the reason for the woofer spacing to the horn is a bracing issue not a performance issue. noah said that is not a problem because he has done it. even wayne does the same thing on the 4pi.

Listen. It's All Good.
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post #27 of 29 Old 04-12-2012, 03:07 PM
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The Four Pi uses a 15" woofer and the enclosure is smaller -- so what spacing latitude there is with achieving the right vertical nulls is more limited than what the Three Pi can do with a 12" woofer.

Wayne has given the technical reasons why he can use the Three Pi's vertical driver spacing and get the vertical nulls just outside the desired pattern as intended.
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post #28 of 29 Old 04-12-2012, 03:59 PM
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that is backwards. for a performance loudspeaker, the enclosure is designed around the horn and woofer.

"Wayne has given the technical reasons why he can use the Three Pi's vertical driver spacing and get the vertical nulls just outside the desired pattern as intended."

that was never in question.

Listen. It's All Good.
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post #29 of 29 Old 04-13-2012, 10:02 AM
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Quote:
Originally Posted by bobgpsr View Post

The Four Pi uses a 15" woofer and the enclosure is smaller -- so what spacing latitude there is with achieving the right vertical nulls is more limited than what the Three Pi can do with a 12" woofer.

It's not all that different, as everything scales - woofer/horn dimensions and XO freq.

Noah
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