Okay, lets try this again.
This has got to be one of the longest projects related to my Bluesmobile on record. Everyone that has casually read this blog knows that I never intended to build the roof speaker. After being asked where the speaker was at every event I attended during her debut season, I finally gave in and started work on the speaker.
Way back in July of 2018 I posted that I was finally in the process of building a replica of the CLM loudspeaker for the roof of the Bluesmobile.
And that’s where it stopped.
Truth be told the story started around Thanksgiving of 2017 when I dropped off the design to Summit Sheet Metal Specialists, Inc. in Summit, IL. Other than the guy looking at me like I had a third eye while trying to convey what I wanted done, he did a fabulous job fabricating the outer shell of the speaker.
While I originally commissioned the shell in Nov. 2017, the fabricator lost my number until early May, 2018. Once he finally found it (Dammit) he called to let me know that it has been done for quite awhile and to hurry up and pick it up, because it was taking up too much of his floor space.
I hurried up and picket up the shell in mid June (Can you see a pattern here?).
Then I got a hold of some extra wood a buddy of mine had left over from building his deck that I picked up to make the roof rack. I also found some 6×6 posts in the alley that I took and cut down to use as well. After examining them though I may use new 2×4’s for the structural frame and then use some of the old stuff for the detail stuff.
The dimensions for the outer shell were made specifically to fit an Atlas DR-72 65 degree uniform coverage loudspeaker. Retail for this speaker is $320 without the compression driver needed for it to work. Since I had no intention of making the roof speaker functional (sound coming from underneath car in order to play music at events with or without loudspeaker) I refused to pay that amount of money what essentially is one big prop.
All work on the speaker stopped in July, 2018. I got busy with events and appearances so it went on the back burner. From time to time I tried to figure out what I was going to do the fill the cavernous hole of the outer speaker shell, then I would forget about it.
While perusing eBay one morning in January I saw an ad for a vintage 31″ Atlas Horn Speaker. Just the size I needed. The price was still a high $250, so I threw out a low ball $125.00 and the guy took it. I was shocked at first, but later found out when I picked it up that he has been trying to get rid of this particular speaker for some time. He got it when he purchased an auction lot of many smaller Atlas speakers. He was able to sell those quickly, but was left with this monstrosity!
He was so happy to finally get rid of it! He couldn’t thank me enough! Not enough to give it to me for nothing mind you, but pretty close!
So now I have the outer shell and inner speaker time to figure out the rest. Like I said, this will be non-functional and I would like to keep the weight of the completed package under 100 pounds. I also want to somehow allow as much air as possible to flow through the speaker and not just around it.
The roof speaker in the movie is a replica CLM Civil Defense Speaker that was used almost exclusively in Canada, most certainly around the time an impressionable young Dan Aykroyd was growing up. The movie prop kept the overall design of the CLM speaker, but took some liberties as it was only a prop.
Here are a couple of pictures of a real CLM Speaker:
Notice the air screens in the front to prevent damage to the speakers, but also allow air through. Also take note of the big honking tube between the front and rear portions of the speaker.
Movie CLM Speaker:
Notice that the upper rear box is completely sealed and the small diameter tube between.
Like all aspects of my Bluesmobile build up to this point, I am going to take a homogenized approach to the speaker build by taking elements of the real speaker and movie speaker and combining them.
The rear of my outer shell measures 16 inches, so I decided to go with 8″ round PVC tube to keep the dimensions similar to the real speaker, and to for the strength to bridge the two pieces.
I then decided to utilize PVC socket flanges in order to give the speaker the industrial look of the real speaker.
For the rear horn, I going with good old fashioned 1/2 plywood. It will be strong enough not to flex, but it’s surprisingly light. See the pics below:
I decided the rear horn’s width should match the end of the big horn, so 16 inches it is. I’ll save you the trouble of having to see pics of each piece!
Once the construction adhesive cures completely, I will remove the temporary braces and fill the holes and other small imperfections with body filler and sand smooth before applying primer and final paint.
While not shown, I also built the little piece for the back of the horn that will allow for air to escape the horn. Also, I did not cover the front of the horn with plywood. I am going to leave it open and install perforated sheet metal over that section to allow the air to pass through, but look closed at first glance like the movie version.
I’ll be posting part two of the build hopefully by next week. If you’re curious as to what suddenly lit a fire under me to get the speaker done, it’s because I will be in the Northwest Side St. Patricks Day Parade and want the speaker to make it’s debut in a grand fashion!
