Tarkus Speaker design by Paul Carmody

[MrBoat]

I earned a Guinness or two today. Can almost hear them! Still need braces and ports.

Tweeters are a snug fit and a little too tight for finish coats, which is just how I like them, I save the little hockey pucks and wrap some 180 grit sticky on them and fine tune the fit to allow for clear coats. I hate seeing gaps around tweeters. It ends up drawing my eye to it for the duration. Luckily for me, Peerless apparently uses the same flanges on numerous tweeters because I alreasy had a pilot hole for this exact size in my homemade circle jig. I always practice the flush stepped cuts on scrap first. It's worth wasting the material to prove the cuts first even if for piece of mind.

Thanks to all who helped me out last night. You fixed my new year off on the right foot. I had a good evening for the rest of the night. Much appreciated.

 

[-Jim-]

Hopefully my little bit helped. I'm enjoying reading about this build with the good photos. Keep it coming.

 

[MrBoat]

Hopefully my little bit helped. I'm enjoying reading about this build with the good photos. Keep it coming.

It did help. It helped jog my memory that I had already gone thru this with this design 3 years ago when I ordered the parts. Just couldn't see it.

I have one other question though. On the colored suggested layout, there is a hyphenated line going from one ground to the other. I don't get what the dotted line means unless it has something to do with the reverse polarity on the other drivers. It's been a number of years but I thought that type of line used to mean shielded cable or something.

 

[-Jim-]

It did help. It helped jog my memory that I had already gone thru this with this design 3 years ago when I ordered the parts. Just couldn't see it.

I have one other question though. On the colored suggested layout, there is a hyphenated line going from one ground to the other. I don't get what the dotted line means unless it has something to do with the reverse polarity on the other drivers. It's been a number of years but I thought that type of line used to mean shielded cable or something.

I checked his notes and there's no mention of the intent of the dashed line. (See Green Arrow) I've always used dashed lines in wiring diagrams to show an option on a circuit, but I've always thought crossovers are typically just wired one way. The change in polarity of a driver is accommodated in the circuit design. Note how the + terminals of the 6.5" SDS and the DX25TG both attached to the upper GND Block while the - terminal of the 10" SLS does the same which effectively reverses it's polarity compared to the other two drivers. On the schematic the orientation of drivers is shown below their names. (look for a + or a - _

I'd have to redraw the schematic from the layout drawing to see for certain as I can't visualize it from the picture on my monitor. (My wife says I've never been good at visualizing things.) Maybe another member can. If not I'll try to make some time tomorrow and figure it out.

 

[MrBoat]

I checked his notes and there's no mention of the intent of the dashed line. (See Green Arrow) I've always used dashed lines in wiring diagrams to show an option on a circuit, but I've always thought crossovers are typically just wired one way. The change in polarity of a driver is accommodated in the circuit design. Note how the + terminals of the 6.5" SDS and the DX25TG both attached to the upper GND Block while the - terminal of the 10" SLS does the same which effectively reverses it's polarity compared to the other two drivers. On the schematic the orientation of drivers is shown below their names. (look for a + or a - _

View attachment 59355

I'd have to redraw the schematic from the layout drawing to see for certain as I can't visualize it from the picture on my monitor. (My wife says I've never been good at visualizing things.) Maybe another member can. If not I'll try to make some time tomorrow and figure it out.

I added the wire between there anyway. Didn't see what it would hurt with them both labeled ground without any other special notes on the crossover. I mean why bother to leave a trace there is there is to be no connection. Wonder if it means twisted cable, perhaps. I don't see why it would need that though unless it's for how many components share that ground point to make a more robust connection to add redundancy or something.

 

[ryanosaur]

I don’t know why it’s dashed, but the connection of that common ground to the other is necessary as there is no other connection back to the amplifier without… unless some other wiring change is made.

In some manner it seams he could have slightly redid the layout to accommodate a single hounding point as the are so close… or perhaps just the inclusion of a solder tag strip could have helped to connect everything.

 

[MrBoat]

Found this original design thread on the Tech Talk forum at Parts Express.

Haven't waded all the way thru it yet but figured to link to it here just in case someone in the future happens across this thread.

 

[MrBoat]

Today hopefully I can install window bracing and ports in the big cabs. Small cabs are essentially done other than attaching the backs.

 

[Alex2507]

Found this original design thread on the Tech Talk forum at Parts Express.

Haven't waded all the way thru it yet but figured to link to it here just in case someone in the future happens across this thread.

Welcome to The Big 10 Inch Club!

The PE thread reminded me of meeting a couple of those posters and hearing their speaker designs. You're right about one of the key components being the fun you have listening.

Pg. 8 shows the FR graph w/ an F3 toward the mid to high 40's. It's a little misleading because there is just so much low end slam (for me anyway).

I'm looking forward to the finish.

 

[ryanosaur]

Some things... you just can't leave alone...

Welcome to The Big 10 Inch Club! ...there is just so much low end slam (for me anyway).

I'm looking forward to the finish.

 

[MrBoat]

I got on to window braces today and gluing baffles on and the backs/baffles on the small cabs. Working on ports next. Meanwhile, I earned a beer on my last day off for the foreseeable future. So hard to get things done on two day weekends otherwise.

I cut the holes out on the bandsaw right thru the webs. The plywood holds the braces which holds the plywood which holds the. . . If I felt so strongly against this tactic, I would spline it back together. But add glue and installed in place, they still are as effective. Especially on such a narrow box.

 

[MrBoat]

To deal with the entry cuts, it's just a matter of gluing a wedge in the crack and breaking it off. This gives a solid reconnection and glue will handle the rest. On the bottom I drove them in from each side after the brace was in so's I didn't make the brace larger, which would have made gluing the brace more awkward than it already is.

 

[MrBoat]

All bracing is now complete. Yet another to check off of the list. Top cabs were only prescribed a side-to-side brace. I am surprised a cabinet that stout needed any. I think he used plywood for his, and modern .75", isn't. It's closer to 5/8" in many instances. That's one of the good thing about MDF or some domestic ply. It's a full .75".

 

[ryanosaur]

All bracing is now complete. Yet another to check off of the list. Top cabs were only prescribed a side-to-side brace. I am surprised a cabinet that stout needed any. I think he used plywood for his, and modern .75", isn't. It's closer to 5/8" in many instances. That's one of the good thing about MDF or some domestic ply. It's a full .75".

I approve.
I know the upper is a small box, but those resonances can be a b!tch.

 

[MrBoat]

When researching this build, I had no idea this design went back so far or I just didn't notice. 2010 still seems so fresh to me somehow, but it's been a bit!

ETA: I have found a lot of favorable reviews of this design while waiting for glue to dry. I have a good feeling about this speaker.

 

[MrBoat]

Everything fits. All that's left to do before finish is mount the crossovers and port. It calls for a 13.5" x 4" Sched 40 pipe. Glad to see it to this point. Will likely try them out before finish to help me decide what they get. The classix2s begged for walnut/black faces. They still look proper to me in those skins.

 

[ryanosaur]

Vintage Fender Sunburst.

 

[MrBoat]

Vintage Fender Sunburst.

Everybody liked that example. I did too. Don't know how I would feel about looking at it forever though.

 

[highfigh]

All bracing is now complete. Yet another to check off of the list. Top cabs were only prescribed a side-to-side brace. I am surprised a cabinet that stout needed any. I think he used plywood for his, and modern .75", isn't. It's closer to 5/8" in many instances. That's one of the good thing about MDF or some domestic ply. It's a full .75".

FYI- most sheet goods are now metric. They show it as inches for the full sheet dimensions but often, the thickness is really 19mm.

BTW- having built literally hundreds of boxes for speakers and mostly for subwoofers, I highly recommend using some kind of mechanical fastener to secure the sides/back/front/bracing, etc in addition to the glue. I know the glue holds very well, but the face of MDF isn't as porous as the edges or real wood and it won't absorb the glue in the same way, so it doesn't hold as well. Narrow or box staples work very well, as do drywall screws. Any excessive depth in the holes when using screws can be filled- I prefer Bondo auto body filler, but a good wood filler will work, too.

Remember, nobody has too many clamps.

Also, and this is for when you build other boxes and speakers, I see that the sides appear to have rabbets at the front, to accept the baffle- if you used a router for that, I would recommend routing a dado for the edges of the bracing because you'll have no chance of a glue joint failing and it actually makes assembly faster because the bracing can't slide on the other pieces.

 

[MrBoat]

FYI- most sheet goods are now metric. They show it as inches for the full sheet dimensions but often, the thickness is really 19mm.

BTW- having built literally hundreds of boxes for speakers and mostly for subwoofers, I highly recommend using some kind of mechanical fastener to secure the sides/back/front/bracing, etc in addition to the glue. I know the glue holds very well, but the face of MDF isn't as porous as the edges or real wood and it won't absorb the glue in the same way, so it doesn't hold as well. Narrow or box staples work very well, as do drywall screws. Any excessive depth in the holes when using screws can be filled- I prefer Bondo auto body filler, but a good wood filler will work, too.

Remember, nobody has too many clamps.

Also, and this is for when you build other boxes and speakers, I see that the sides appear to have rabbets at the front, to accept the baffle- if you used a router for that, I would recommend routing a dado for the edges of the bracing because you'll have no chance of a glue joint failing and it actually makes assembly faster because the bracing can't slide on the other pieces.

Home center "3/4" is more like 17.7mm. I have to shim it to make it match up to real 3/4".

I would have rabbeted the braces but the drop I had left wouldn't let me get both out of it if I made it for rabbets. The corners on the bass bin are already screwed with drywall screws. I just glue the braces in first and screw after unless the piece is a little loose. These braces only had enough room for glue and had to be bumped into place once glue was on them. Appreciate the tips.

I also use cabosil/epoxy for filler, than I saturate the enclosures with thinned epoxy. As the solvent in the epoxy dissipates, it returns to it's full viscosity gradually and I keep feeding it until it won't take anymore. I get about .25" penetration and it makes it to where the extra sharp corners needed for veneer, aren't so fragile anymore and it hardens the MDF substantially. Sanded, cleaned epoxy is a very good (if not the absolute best) primer for paint, solvent based adhesives like contact cement. It turns MDF into a sort of a phenolic type material with what amounts to extreme durability. All screws are set in epoxy as well and will never vibrate loose. They may even need to be heated with a soldering iron in some cases to get them out.

first coat of thinned epoxy on a set of baffles. 80 grit sandpaper on an RO is all it needs to get adhesive to really grab hold.

ETA: Since the window brace is trapped on all 4 sides, all the screws really need to do is keep it located. I epoxy seal the insides of the cabinets as well. These should last hundreds of years. I'll use leftover epoxy filler to make epoxy fillets on both sides of the braces. Best place to put it, rather than toss the overages when it starts to kick.