Stereo Integrity HT 18" Alfa-74 project - Page 6 - Home Theater Forum and Systems - HomeTheaterShack.com
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post #51 of 107 Old 11-15-13, 08:11 PM Thread Starter
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Re: Stereo Integrity HT 18" Alfa-74 project

Hello everyone

This project is still moving ahead, but slow. I spent several nights trying to figure out the bracing and ports on the triangular shape design, but I was not comfortable with the result and the open area that would be available. So, I don't want to have any risk of bad performance since I'm investing time and money, so I'm now taking a different direction.

Now I will work on a more traditional design, a square design with straight ports, so I would get a design that should deliver a performance according to the win ISD calcs.

I'm still targeting 500L (17.6 ft3), and after adding port, driver and bracing volume, I will be building an enclosure of 551L. 2 flared ports 6in diameter x 54.4 cm (21.4in) for 18 Hz tuning.

I will be using double layer for the baffle.

Internal dimensions are:

Width: 62cm
Depth: 80cm
Height: 120 cm

Inner port is 216mm away from the panel, so it's more than 1 diam away, so it should not be a problem.

See the new design:
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post #52 of 107 Old 11-15-13, 08:14 PM Thread Starter
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Re: Stereo Integrity HT 18" Alfa-74 project

But I just would like to get your opinion regarding the bracing, please see the pics:

What do you think?

Is this ok?

I'm also planning to add a second layer to the bottom, because I'm planning to add some feet and I would like to have a good support.

any comments?
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post #53 of 107 Old 11-16-13, 08:48 AM
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Re: Stereo Integrity HT 18" Alfa-74 project

The bracing looks good to me. Have you figured out how much it will weigh? At some point the weight and size of the feet would dictate whether you need another layer on the bottom. Or if you don't want another whole sheet on the bottom, you could put some corner bracing on the inside of the bottom.
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post #54 of 107 Old 11-16-13, 04:04 PM Thread Starter
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Re: Stereo Integrity HT 18" Alfa-74 project

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Paulcet wrote: View Post
The bracing looks good to me. Have you figured out how much it will weigh? At some point the weight and size of the feet would dictate whether you need another layer on the bottom. Or if you don't want another whole sheet on the bottom, you could put some corner bracing on the inside of the bottom.
Well, considering that I would be using 3 and a half MDF 3/4 sheets, and around 80 punds per sheet, and adding the driver weight, my guess is that it will be a little higher than 300 lb.

I like your idea about bracing inside, I will run some sketches.

I just got the material and the build will begin within next week.

Regards
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post #55 of 107 Old 11-18-13, 10:05 AM
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Re: Stereo Integrity HT 18" Alfa-74 project

I like your design This is going to be a nice looking sub!

Some thoughts: you are going to use a substantial amount of sheet goods for your bracing. Have you considered doweling or bracing with laminated cut strips to minimize how much effort you will have to put in for window cuts? I would put a dowel or laminated strip across your enclosure at all your current bracings' intersections.

By essentially breaking up the panels into smaller panels you not only increase their resonant frequency but increase their perceived strength as well. To do that you only need those intersections reinforced to get to that rule of thumb of no panel size over 12x12".
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post #56 of 107 Old 11-18-13, 12:05 PM
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Re: Stereo Integrity HT 18" Alfa-74 project

Sub'd, looking good!

I think about speakers for hours every day. I believe it is mental illness.
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post #57 of 107 Old 11-18-13, 12:17 PM Thread Starter
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Re: Stereo Integrity HT 18" Alfa-74 project

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BD55 wrote: View Post
I like your design This is going to be a nice looking sub!

Some thoughts: you are going to use a substantial amount of sheet goods for your bracing. Have you considered doweling or bracing with laminated cut strips to minimize how much effort you will have to put in for window cuts? I would put a dowel or laminated strip across your enclosure at all your current bracings' intersections.

By essentially breaking up the panels into smaller panels you not only increase their resonant frequency but increase their perceived strength as well. To do that you only need those intersections reinforced to get to that rule of thumb of no panel size over 12x12".
No but sounds interesting. Let me see if I understand correctly, I have to replace all the window type bracing with some kind of rods?

In the other hand, if I continue with window type bracing, will I have the same results using MDF or plywood?

Regards
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post #58 of 107 Old 11-18-13, 12:19 PM Thread Starter
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Re: Stereo Integrity HT 18" Alfa-74 project

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skeeter99 wrote: View Post
Sub'd, looking good!
Thanks !!!!, I hope it performance good too!!
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post #59 of 107 Old 11-18-13, 12:36 PM
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Re: Stereo Integrity HT 18" Alfa-74 project

Nice design, I like it.




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post #60 of 107 Old 11-18-13, 01:22 PM
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Re: Stereo Integrity HT 18" Alfa-74 project

Quote:
alfa-74 wrote: View Post
No but sounds interesting. Let me see if I understand correctly, I have to replace all the window type bracing with some kind of rods?

In the other hand, if I continue with window type bracing, will I have the same results using MDF or plywood?

Regards
I probably didn't make much sense - here's what I was getting at:

Stereo Integrity HT 18" Alfa-74 project-alpha-74.jpg

They could be rods or pieces of wood 3/4" laminated with another 3/4" to get a piece for one rod that is 1.5"x1.5" by whatever length you need. Doing this would eliminate the need to cut windows out of a sheet and would minimize waste (and likely keep weight down a bit).

Take a look at this thread http://www.hometheatershack.com/foru...8d2-build.html from baniels.
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