Casting a resin speaker box using RTV.

[ACL1504]

I was taking inventory of my speakers and found that I needed three QSI speaker boxes. I have three of the Mini-Oval Speakers by QSI but no boxes. Heck, I don't even know if QSI is still in business. The Mini-Oval Speakler is an 8 Ohm 1.0 Watt speaker. It measures .56" X 1" or 14X25 mm.

Here is what the speaker looks like.



It is small but sounds great in smaller locos with DCC sound.

I have one speaker box that fits the speaker and decided to change gears for a few hours. I took the speaker box/enclosure and placed it in a small plastic box. It was a perfect fit.



Continued in a few.

[ACL1504]

I then used Baby Powder to lightly cover the speaker box and the inside of the plastic box. This reduces the friction in the demolding process.



I used the RTV (Room Temperature Vulcanizing) from Micro-Mark. It's the 1 to 1 rapid 4-hour cure Silicone Mold Rubber.

I used a round dowel to thoroughly mix Part A and Part B.



Continued in a few.

[ACL1504]

I like using the small Dixie Cups for mixing. They have lines and other patterns on the cups. I use these lines to determine how much rubber mold compound and resin mix to use.



I used equal parts of A and B and mixed thoroughly. I then carefully poured the RTV into the plastic tray/box.



The completed mold was ready to remove after four hours but I let it sit overnight.

Continued in a few.

[ACL1504]

This morning I used a #11 Xacto knife to pry the mold out of the small plastic box.



After removing the silicone rubber mold, I removed the speaker box/enclosure.



The original speaker was then placed back into the mold for your viewing of how it looks when it is ready to be removed.



Continued in a few.

[ACL1504]

Here is a better view of the Dixie Cup.



I then mixed Part A and Part B of the casting Resin. I used the Micro_Mark CR-600 High Performance Casting Resin. After thoroughly mixing the two parts, I poured the resin mix into the rubber mold and let it harden.



NOTE: You have about two minutes to make the pour after mixing the two parts.

You can remove the new part after 30 to 60 minutes. I let it sit for about two hours as I was working on something else.


The mixture is clear but will dry to a milky white.

Continued in a few.

[ACL1504]

The new resin speaker box is white and hard.



The speaker fits into the new part with no problem. This was an easy fix to get the speaker enclosures I needed. I've made four just in case. But I'll have the rubber mold for quit some time.



Tom

[donatode]

Nice Job....and neat too!!!!

[jimmillho]

Is that speaker similar to the ones from Digikey ?

Jim

[ACL1504]

Nice Job....and neat too!!!!

Donato,

Thanks, much appreciated. This was an easy task and the RTV is great for making spare parts.

Tom

[ACL1504]

Is that speaker similar to the ones from Digikey ?

Jim

Jim,

Thanks for stopping by. I'm not familiar with the Digikey. It is a Digitrax product? I haven't found anything else the small QSI speaker will fit into other than the QSI speaker enclosure.

Tom

[GPdemayo]

Great job Tom.....does the sound system for the C&O J-3 need one of these super special custom built speaker boxes? 

[ACL1504]

Great job Tom.....does the sound system for the C&O J-3 need one of these super special custom built speaker boxes? 

Greg,

Thanks, much appreciated. No, your C&O J-3 will have a mack daddy speaker in it! No enclosure needed. The brass tender will act as the box. Some foam around the speaker will do the trick.

Tom

[jimmillho]

Tom,
Digikey is the Electronics Co that had the small speakers we used for the PFM System.

Jim

[ACL1504]

Tom,
Digikey is the Electronics Co that had the small speakers we used for the PFM System.

Jim

Jim,

I don't remember the name. However, I've only used the PFM 1.5" 8 Ohm speakers from PFM/PBL. PFM is marked on the top of the speaker. This is what happens when one gets old, I just don't remember.

Tom

[GPdemayo]

Great job Tom.....does the sound system for the C&O J-3 need one of these super special custom built speaker boxes? 

Greg,

Thanks, much appreciated. No, your C&O J-3 will have a mack daddy speaker in it! No enclosure needed. The brass tender will act as the box. Some foam around the speaker will do the trick.

Tom

Mack daddy.....that sounds even more super dulexee !