InDIYana build - SuperNova Minimus

[wogg]

These will be a vintage speaker re-build. I have 2 pairs of Realistic Nova 15's from the mid 80's to use, one pair will be my 3 way for MWAF, this pair will be a more direct homage to the Realistic original as a 2 way with an 8" (ish) paper woofer.

Behold... the original Realistic Nova 15:



The tweeters were already purchased last year at the MWAF tent sale: Peerless DX25BG60-04
The Fs is low on these, and they should be able to reach near a 2k crossover point. There's some wiggle at the top octave in response, however that wiggle disappears off axis so it doesn't worry me much.

After a lot of woofer modeling, starting at response curves, and some preliminary PCD work to see if a 5 part crossover would work, I landed on the Dayton RS180P-8 for the woofer choice. They won't get the full bottom end that I'd like (<50Hz, preferably 40), but they should reach a solid 60Hz, which conveniently makes them match the stated specification of the original Realistic design. The regular RS180 does better in this cabinet, but the breakup makes a simple crossover impractical.

Woofers are on their way this week, and after cutting out the baffle the experiments to add rigidity to these old cabinets will begin!

[tomzarbo]

Dos post.

[tomzarbo]

Looks fun. I have a fondness for rat shack speaks too.
Last years MWAF design was almost a retro redo of a RS tower that I loved in my teen years but couldn't afford.
"genuine oiled walnut" rocks!
TomZ

[KEtheredge87]

Very cool sir! I'm using the RS-180P 4 ohm version in my InDIYana entry. I imagine the smooth top end response on those woofers will make them a favorite for many entering the competition. I'll be watching your cabinet retrofit with great interest. I've occasionally wondered how to improve some "classic" designs and "un-cut" whatever proverbial corners were cut for cost savings.

That name is pretty boss too! "Supernova Minimus" has a great ring to it!

[Billet]

Nice looking boxes, great idea. I look forward to seeing and hearing them in April.

[wogg]

Progress! The original Nova's were disassembled and cut up today. The tweeters are a bit more robust than the originals.



The woofer is a bit more robust as well.


A bit of a hack job getting the old baffle cut out. My old craftsman jig saw leaves about 1 1/4" from blade to the edge of the plate.

[wogg]

And we have baffles, cut to fit in the recess. I'll touch them with a 45 degree chamfer bit to line up a bit better with the little metallic trim ring.


A single 4' x 2' project board made 4 baffles + 1 extra for this project and my future 3 way. All I had to do was route the driver holes.


The little hole in the bottom right is the center of the 2" port. I routed the PVC outside diameter on the back side, 3/8" deep. The port connects to a 90 degree slow sweep elbow, so all I need to do is mount a little PVC slug to mate with the elbow. The front exit will be trimmed out with a flush bit, the rounded over with a 1/2" bit. I should have about 5" effective port length with the slug and elbow, just need a couple more inches for this one. I'll tune it by press fitting the PVC before glue.

Test fit for drivers, looks good! They do stand a little proud, but that should reduce when torqued down.


Next up... Getting the port bored out and determine what kind of bracing I can add. The baffle is 5/8" thick on this, but the sides and possibly rear appear to be 1/2" MDF. I want to do 45 degree 1x2 braces from side to back in a randomish pattern. There isn't that much depth in there though, so I'll have to figure out where I can fit them with the drivers mounted.

[xmax]

Very cool sir! I'm using the RS-180P 4 ohm version in my InDIYana entry. I imagine the smooth top end response on those woofers will make them a favorite for many entering the competition. I'll be watching your cabinet retrofit with great interest. I've occasionally wondered how to improve some "classic" designs and "un-cut" whatever proverbial corners were cut for cost savings.

That name is pretty boss too! "Supernova Minimus" has a great ring to it!

I used RS-180P in my brothers speakers, I didn't save the XO design but if I recall it was a simple (not far from textbook) 2nd order
and any little wiggles in the FR were less damaging (to the sound quality) than the corrective circuit. It's a fine choice for the
bare minimum event.

[djg]

Nice baffles.

[wogg]

Nice baffles.

Thanks!

[wogg]

Next step, carve out the port hole that mates to a couple 2" PVC slugs. The back side was already routed to mate with the PVC outside diameter with a 1/4" straight bit.


Just had to take it outside while the weather is acceptable to flush trim out the port and round it over.



I did the trim and round over without gluing in the PVC slug, figuring it fit tight and wasn't going to go anywhere. Unfortunately I was wrong on baffle #2, the PVC slipped down a bit right at the end of the run for the round over causing it to dig deep.


Only thing to do there is to glue in the PVC and use some filler for the glitch. After that sets up I'll have to hit it with the round over again to smooth it back out.

Amazingly, the port clears the original baffle hack job without additional work. That's awesome because I wasn't sure how I was going to do that without spending some time with an old fashioned rasp. I have some hardware showing up tomorrow to mount the drivers to the baffle. Then I just have to pilot and install the 6 baffle to cabinet bolts and cut some port lengths for testing. Then I'll be ready to pull measurements and work on the crossover.

[KEtheredge87]

I hate when the router starts walking places we don't intend it to go! Lucky thing that'll be an easy fix, just additional time and effort. Good work so far!

[xmax]

It can be scary when the CNC gets a mind of it own too...

[wogg]

Time to plan the added bracing. The goal is to keep the baffles fully removable and exchangeable with a different baffle if desired someday. In order to meet that goal, a proper window brace isn't going to work. So first, I tried to see what kind of space I had behind the drivers for bracing.


With the tweeters puled out I could see the space behind the woofer, but not really measure anything, so I guestimated. I chose to do 45 degree 1x2 pine braces, with a 7", 2x6" and 2x5" braces per cabinet, measured along the long side. The idea was to not be uniform along the side and back, and have different lengths to spread out the rigidity a bit. With a basic plan, I hit the miter saw.



Then the braces were laid out in the cabinets. I skipped the top and bottom panels since they're really pretty small anyway.

[wogg]

I glued them in with some 5 minute epoxy, which I also used to secure the port tubes to the back of the baffles. It turns out the PVC elbows don't quite clear the old baffle hack job, so I'll need to trim and sand out a bit more material before getting the bolt holes cut for the baffle mounting.

The back of the cabinet will be lined with egg crate foam cut around the braces, with some along the lower side opposite the port hole as well. The 90 degree port turn will face the side, and fire into the foam for what I hope to be maximum midrange suppression out the ports. Then I'll run some wire out the port and do some test measurements to get the crossover going. That original terminal plate is coming out for an improved PE version with banana jacks. I figure I'll order those as I get crossover parts.

While doing these, I'm thinking the Anarchy 708 based three way will be extra tricky, the ports need to be a full 6" longer in there to tune low enough for the Anarchy's which will require some extra care for port and brace placement. I'll cross that bridge when I get there for MWAF.