Auto Tuba Dual 8
Posted: Thu Sep 02, 2021 2:16 pm
Hi BFM Groups
Here I have my 2nd BFM cabinet build. I have already built 6 t24 single 10's. As usual after you build you want to build something else. So an Auto tuba it is. After the T24's I bought myself a small CNC and I've included some of the pics from the machine. I built this cab out of MDF to test all my cnc cuts, fitment and to try out this mini beast before spending on higher quality/priced baltic. The CNC is nice, but the plans are actually faster, and forgiving.
Here are my mouth brace pieces, and a brace for inside in speaker chamber (not really needed but this was a test cab and also a test of my cnc skills)
These are all the pieces that are in the enclosure. I decided on two long larger braces that you can see in the top. Nothing wrong with the plans braces. I just did it as a test and to also keep the alighment as I put it all together.
I did a .2 inch rabbit for the sides for the panels to slide into for alignment
Testing the fittings and only the back piece glued in place. Don't worry to the top piece was not secured with that gap.
Next testing to make sure the cones were aligned over the screw holes and would not cone rub the baffle before I put the "square blocks" in place
Attached the internal brace which also helped me align my panels. All were very close with the CNC, with just left me to do a tiny bit of sanding edge to make fit perfect. As I already had t24's I was not in any massive rush to build so I took my time. I fitted a piece or two, let dry, then sealed the edges on Both side for any possible air gaps. As the pieces were .2 inch into the panel and fit snug I still sealed to prevent any leaks.
Here is that looong internal brace that is complete over kill (insert Bill rolling his eye emojie here. ...lol) It was built a little out of sequence than the plan, but on only the back and bottom order . As it was very square and let me do my wiring and connection plate work with the back off. I also did a single piece for each access panel "lip" as you can see ,and it only needed a little sanding to slide right is and very snug.
The mouth brace, I copied the look of Functionone bass cabinets as I like that look with the circles
Here is the raw cabinet prior to me starting the finishing. As you can see I purposely left the top edge longer so I can router it nice and straight and then do a round over. Still need to fill the screw holes on the one side then sanding and paint.
The final product ran into an issue:
I first set my amp output to 20volts to get the cabinet playing. I was not expecting a T24 output, but was ready for some bass. But no go. as soon as I got little volume it started to make a massive "KAK, KAK" sound. I played with crossover, (no eq was on) check voltage, checked polarity, listened for air leaks everything was good...... but it sounded very bad at 1/3 plus volume. I knew I could not be the design as my t24's sound awesome. Long story short a brand new MCM driver was bad. Luckly I bought 4 of them as the idea was to build 2 Auto8 dual8's and use them for dj monitor cabs, or for bass in small gigs. New driver in and here we go.
On a ground plane (ie my garage) in the middle of the room I'm getting about 110db with music. But place in in my truck, and it maxed at 130.4db playing music. BTW the track I was listening to was Junior Reid -One Blood
I will have some more picture up once I start finishing
Here I have my 2nd BFM cabinet build. I have already built 6 t24 single 10's. As usual after you build you want to build something else. So an Auto tuba it is. After the T24's I bought myself a small CNC and I've included some of the pics from the machine. I built this cab out of MDF to test all my cnc cuts, fitment and to try out this mini beast before spending on higher quality/priced baltic. The CNC is nice, but the plans are actually faster, and forgiving.
Here are my mouth brace pieces, and a brace for inside in speaker chamber (not really needed but this was a test cab and also a test of my cnc skills)
These are all the pieces that are in the enclosure. I decided on two long larger braces that you can see in the top. Nothing wrong with the plans braces. I just did it as a test and to also keep the alighment as I put it all together.
I did a .2 inch rabbit for the sides for the panels to slide into for alignment
Testing the fittings and only the back piece glued in place. Don't worry to the top piece was not secured with that gap.
Next testing to make sure the cones were aligned over the screw holes and would not cone rub the baffle before I put the "square blocks" in place
Attached the internal brace which also helped me align my panels. All were very close with the CNC, with just left me to do a tiny bit of sanding edge to make fit perfect. As I already had t24's I was not in any massive rush to build so I took my time. I fitted a piece or two, let dry, then sealed the edges on Both side for any possible air gaps. As the pieces were .2 inch into the panel and fit snug I still sealed to prevent any leaks.
Here is that looong internal brace that is complete over kill (insert Bill rolling his eye emojie here. ...lol) It was built a little out of sequence than the plan, but on only the back and bottom order . As it was very square and let me do my wiring and connection plate work with the back off. I also did a single piece for each access panel "lip" as you can see ,and it only needed a little sanding to slide right is and very snug.
The mouth brace, I copied the look of Functionone bass cabinets as I like that look with the circles
Here is the raw cabinet prior to me starting the finishing. As you can see I purposely left the top edge longer so I can router it nice and straight and then do a round over. Still need to fill the screw holes on the one side then sanding and paint.
The final product ran into an issue:
I first set my amp output to 20volts to get the cabinet playing. I was not expecting a T24 output, but was ready for some bass. But no go. as soon as I got little volume it started to make a massive "KAK, KAK" sound. I played with crossover, (no eq was on) check voltage, checked polarity, listened for air leaks everything was good...... but it sounded very bad at 1/3 plus volume. I knew I could not be the design as my t24's sound awesome. Long story short a brand new MCM driver was bad. Luckly I bought 4 of them as the idea was to build 2 Auto8 dual8's and use them for dj monitor cabs, or for bass in small gigs. New driver in and here we go.
On a ground plane (ie my garage) in the middle of the room I'm getting about 110db with music. But place in in my truck, and it maxed at 130.4db playing music. BTW the track I was listening to was Junior Reid -One Blood
I will have some more picture up once I start finishing