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7pi build [message #91284] Mon, 23 December 2019 18:34 Go to next message
grimberg is currently offline  grimberg
Messages: 6
Registered: October 2017
Esquire
I am planning to build a pair of 7pi speakers and started preparing the project chart. I will use the JBL 2226H, Delta 10A and B&C DE250-8. I have a few initial questions.

1) Which horn to use with the tweeter?
2) The plan does not show where the binding posts should be placed on the woofer's cabinet. I am thinking the same panel on which the woofer is installed, correct?
3) Same as above for the mid-horn cabinet. The binding posts should be installed on the rear panel, right?
Re: 7pi build [message #91285 is a reply to message #91284] Tue, 24 December 2019 13:25 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18069
Registered: January 2001
Illuminati (33rd Degree)

Very good! I think you will be quite pleased with your project.

To answer your questions, the tweeter flare is the H290C waveguide. It doesn't need to be installed in a cabinet, but is more attractive when enclosed. You are free to use your imagination, but keep the waveguide close to the midhorn.

We used to offer a wood horn/waveguide but have ceased production of it after we made the H290C mold. The wood version was attractive but very expensive.

Some people just sit the midhorn on the bass bin and the tweeter on top of the midhorn. Others like to permanently mount the midhorn and tweeter. They mount the crossover in the bass bin and pass the wires through internal connectors to the midhorn and the tweeter.

I personally like to put connector plates on all three subsystems, and to put the crossover in its own little box. I sit the crossover box on the bass bin behind the midhorn. I also like to pin together the three subsystems rather than permanently attaching them or just leaving them sitting unattached. See the link below for positioning pin details and other tips:
Re: 7pi build [message #91471 is a reply to message #91285] Wed, 19 February 2020 12:48 Go to previous messageGo to next message
grimberg is currently offline  grimberg
Messages: 6
Registered: October 2017
Esquire
I have just received the H290C horns purchased from Pi Speakers. The B&C DE250-8 documentation specifies the bolts as M6 but does not mention how deep they should go. Could you tell me what length M6 bolts should I use?
Re: 7pi build [message #91473 is a reply to message #91471] Wed, 19 February 2020 13:44 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18069
Registered: January 2001
Illuminati (33rd Degree)

The DE250 compression driver comes with studs and nuts that are the perfect length. Just use the mounting hardware that comes with the drivers.
Re: 7pi build [message #93395 is a reply to message #91284] Sun, 28 March 2021 14:09 Go to previous messageGo to next message
grimberg is currently offline  grimberg
Messages: 6
Registered: October 2017
Esquire
Wayne,

This past year I had to halt my 7pi speakers build due to the unforeseen events we have all experienced. I have now all the parts and material in hand, ready to resume and hopefully complete the build in the coming weeks. Before preparing the plywood cut diagram I wanted to confirm if my understanding of the information you provided is correct.
Using the diagrams and information contained in the pdf file you provided, the internal dimensions of the bass bin should be: 16" W x 32 ¾" H x 7 ¾" D. The port opening should be: 6 ¼" W x 3 ½" and its depth 5 ¼" measured from the outside surface of the baffle. Is this correct?
Sorry if it sounds redundant.
Re: 7pi build [message #93397 is a reply to message #93395] Mon, 29 March 2021 09:14 Go to previous messageGo to next message
Wayne Parham is currently offline  Wayne Parham
Messages: 18069
Registered: January 2001
Illuminati (33rd Degree)

The box dimensions are right. The port is too, but do notice that it's kind of weird in that it is an "L" shape. It is made longer than the depth of the box by having a right angle at the end formed by the two pieces of 3/4" material on its top. This adds 1-1/2" extra length to the port.
Re: 7pi build [message #93419 is a reply to message #93397] Thu, 01 April 2021 17:55 Go to previous messageGo to next message
grimberg is currently offline  grimberg
Messages: 6
Registered: October 2017
Esquire
Wayne,

While working on the mid-horns I ran into a problem. After cutting one horizontal side and one vertical side using the measurements in the documentation, I realized they do not align properly. After making sure my layout was correct, I decided to calculate the lengths of the sides using the length of the bases and associated heights. My calculations showed the length of the sides on the horizontal piece at 14.70", while on the vertical piece they measure 14.98", a bit shy of 9/32". Has there been an update to the documentation since you sent me a copy? Should the horizontal side made longer to match the length of the vertical side, or vice-versa?
Re: 7pi build [message #93420 is a reply to message #93419] Thu, 01 April 2021 19:07 Go to previous message
Wayne Parham is currently offline  Wayne Parham
Messages: 18069
Registered: January 2001
Illuminati (33rd Degree)

The side panels are longer since their angle is greater. When I did the original prototypes, I cut them as shown in the plans. Later, the cabinet shop made a 3D model for cutting the panels and a jig for assembly.

None of that really helps much. What I suggest is that you make the top and bottom panels long enough they match the side pieces. The final result should be a horn that has 12" x 24" mouth and 4.5" square throat.
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