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Re: My 3π adventure [message #95565 is a reply to message #95434] Sat, 30 April 2022 13:30 Go to previous messageGo to next message
hudelson2 is currently offline  hudelson2
Messages: 6
Registered: May 2016
Esquire
I think you mean 50 millimeters or 5 centimeters, which is about 2 inches.
Re: My 3π adventure [message #95566 is a reply to message #95565] Sat, 30 April 2022 14:03 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
hudelson2 wrote on Sat, 30 April 2022 13:30
I think you mean 50 millimeters or 5 centimeters, which is about 2 inches.
Of course you're right, sorry about that.

The waveguides are done! Here is a picture and I will post some measurements when I do find the time to do them. They look way better up close, it's very difficult to photograph reflective surfaces.

/forum/index.php?t=getfile&id=3034&private=0

In other news I have gathered everything that's needed except the insulation. I have also tested the mounting hardware, the tnuts go into the wood very easily if you use an Allen head screw. I was trying with Philips before that and it was very hard to do. Some common epoxy will probably stick them fine, I don't thing there's a need for expanding glue. I will contact the cabinet maker when I finish with the plans and move on from there.
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Re: My 3π adventure [message #95568 is a reply to message #95566] Sat, 30 April 2022 16:31 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18362
Registered: January 2001
Illuminati (33rd Degree)

They look fantastic!
Re: My 3π adventure [message #95569 is a reply to message #95568] Sat, 30 April 2022 17:00 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
Thank you Wayne. They're really better up close. These were done professionally in a car paint place and they were baked as well. It was free of charge as well because a friend of a friend owns the place.

The funniest part was that on top of the paint for these a rather fancy lacquer was used. I instructed him to use the least amount of material possible and he used a lacquer that can produce a coating in very few microns, I really can't remember the number. He told me that they use that only on race cars in which even the smallest amount of weight counts. I found that both interesting and very funny at the same time considering the way it's used here.
Re: My 3π adventure [message #95597 is a reply to message #95260] Sat, 07 May 2022 21:02 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
Because there were some very slight imperfections from the paintjob I decided to do some measurements in order to see everything is ok with the waveguides. TL;DR everything is fine, or at least what worried me at first had nothing to do with the paintjob.

This is the measurement setup. It's a somewhat nearfield measurement to minimize room reflections as much as possible.

/forum/index.php?t=getfile&id=3059&private=0

This is the response. I tried both drivers and both waveguides but all the results are very similar to this.

/forum/index.php?t=getfile&id=3060&private=0

What initially worried me was that 2-headed spike in the 14k-18k region. Mainly due to the fact that in Wayne's measurements it wasn't there (the rest of it looks almost identical). It also appears to be flatter in the 800Hz-2kHz region but I guess that's good. This 2-headed spike appears to be a property of the drivers - it's there even without a waveguide attached and ironically something very similar can be seen in the response of the DE250 provided by the manufacturer.

This is the tweeter going through the crossover.

/forum/index.php?t=getfile&id=3061&private=0

And these are both responses plotted together and smoothed (var) in order to be more easily compared.

/forum/index.php?t=getfile&id=3062&private=0

By the way these babies HISS Shocked I was shocked to find that the DE250 when connected directly to my Hypex NC400 you can clearly hear them hissing and we're talking about an amplifier with a measured 105db SINAID Shocked It goes completely silent when it goes through the crossover. Just for fun I also tried it with my Monrio MC205 dual mono and it was a hissing festival. Coming from 85db speakers that go as low as 2.7Ω in the bass region this is a completely new world to me.

I am finishing up the plans, I will post an update here. I expect the cabinet construction to begin in the upcoming weeks.
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Re: My 3π adventure [message #95602 is a reply to message #95260] Mon, 09 May 2022 19:30 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
The last speaker material is finally here!

/forum/index.php?t=getfile&id=3063&private=0

The plans will soon follow.
Re: My 3π adventure [message #95603 is a reply to message #95260] Tue, 10 May 2022 14:36 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
On with the plans. Definitely one of the most stressful, if not the most, processes of the project.

This is the overall size compared to the original plans. The stock is a bit thicker (19mm - 3/4") and there's a very slight difference in internal volume (shown in the picture) which I think is negligible. This is due to rounding values from in to mm.

/forum/index.php?t=getfile&id=3064&private=0

and this is the front panel plan both in mm and inches.

/forum/index.php?t=getfile&id=3065&private=0

1)It's a bit alarming that I had to modify the size of both cutouts in order to accommodate the drivers. For the woofer the cutout is supposed to be 11 1/16" (281mm). The official drawing of 12PLB100 shows a diameter of 282mm so it cannot fit there. I took the liberty and designed the hole to be 284mm leaving a 2mm tolerance, I hope this turns out to be ok. The 10 ½" (267mm) width for the waveguide also appears to be small, I made this significantly larger at 272mm.

2)The distance between the two driver's centers ended up being 11" (279.5mm). Does that sound correct?

3)On the recessed parts:

/forum/index.php?t=getfile&id=3067&private=0

/forum/index.php?t=getfile&id=3066&private=0

I am not sure at all about the depth and width of the recessed parts. I will have to discuss this with the cabinet maker but two issues pop in my mind right now. The depth should be straight forward; however, I will use a 2mm EVA gasket for both drivers. This thing compresses but its difficult to estimate by how much. I made the depths for the parts to be 1mm shallower so when the driver is installed with the 2mm gasket it protrudes for about 1 mm. This way hopefully when it's tightened it will sit flush. If it recesses too much, I can always install another 1mm gasket, I hope that works. For the width I really have no idea. The point here is for the width to be as wide as need for the driver to be installed but on the same time not wide enough for it to show the lateral 'inside' surface of it. How critical is this it will also depend on the finish I guess. I left a 3mm tolerance for the woofer and less for the waveguide, but I will give the waveguide to the cabinet maker to test it. Not for a moment I know how I will install a 10kg driver from the top by holding just the edges.

4)Support will be added behind the drivers. A 19mm depth ring behind the woofer this will have the size of the reassessed part but with a slightly larger external diameter (10mm bigger). Two 15mm depth bars will be added behind the waveguides in the place where screws are. These will also have the size of the top and bottom recessed parts. Everything is going to be mounted with M5 bolts and Tnuts.

5)The bracing will be of the 'window' type, made from the same MDF 19mm. I moved it as close as I could to the woofer support ring because it might interfere with the waveguide placement since a 5mm fiberglass sheet will be installed on top of it. Is this the best practice? It will actually be a bit closer to the waveguide than shown in the picture because I designed the woofer support ring to be a bit larger than in these plans shown here.

I would highly appreciate any feedback at this stage, this is really uncharted territory for me!

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Re: My 3π adventure [message #95604 is a reply to message #95603] Tue, 10 May 2022 15:58 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18362
Registered: January 2001
Illuminati (33rd Degree)

Looks really good so far!

You're right that the 12PLB100 driver is abnormally large. Just a smidge, but definitely larger than all the other 12" drivers we use. The cabinet shop had to re-work all the cutouts for the flat-pack kits that support the 12PLB100 midwoofer.

Re: My 3π adventure [message #95605 is a reply to message #95260] Tue, 10 May 2022 16:04 Go to previous messageGo to next message
ppkstat is currently offline  ppkstat
Messages: 38
Registered: February 2022
Baron
Thank you Wayne. I understand that I did everything correctly which is very surprising Laughing

Would you mind to share your experience about the width of the recessed parts (what tolerance is preferred there)? I would also like to hear your opinion about point 5, that is the height of the bracing window.
Re: My 3π adventure [message #95606 is a reply to message #95605] Tue, 10 May 2022 16:34 Go to previous messageGo to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18362
Registered: January 2001
Illuminati (33rd Degree)

The main thing about the brace between the woofer and tweeter is actually that it be suitable for placing and holding a sheet of fiberglass insulation. It serves two purposes: 1. To tie the baffle and cabinet back together (and side to side) and 2. To hold a sheet of insulation. The insulation should span the cross-section, dividing the cabinet into two areas. Bass will pass right through the two areas but midrange will be damped by the sheet in the middle of the cabinet much more effectively than if it was just lining the internal sides.

As for the groove routed for the drivers, that's purely done for aesthetics. So as long as the divers fit, you're good.
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