My 1212/66 Build

[5StringPocket]

I've wanted to try the Eminence 3012LF/Faital W6N8-120 pairing ever since I saw Post #632 in this Low Down Sound link:

http://www.talkbass.com/forum/f15/low-down-sound-cab-club-started-452230/index32.html
A single 12 cab has never quite done it for me so it was either build a pair of 8 ohm mirror image 12/6 cabs which could be stacked, or double up the recipe and build a 4 ohm single 1212/66. To be practical this single cab would need a manageable size and weight.

I considered an ultralight composite build but it was too far out of my comfort zone so I checked out light plywood options and decided to try 12mm 7-ply Okoume marine plywood because of its high strength to weight ratio. A 4'x8' sheet only weighs 40 lbs (1.25 lb/ft2) compared to 43 lbs for a 5'x5' sheet of 12mm birch ply (1.75 lb/ft2) used in a previous build. Okoume is stronger and lighter than Auraco but considerably more expensive.

The fEarful 1212/6 is optimized for a pair of Kappalite 3012LF woofers so it made sense to modify its dimensions to accommodate the larger mid chamber required for the pair of Faital 6.5" drivers, faithfully replicating its internal volume and tuning in the process. The scale drawing I ended up with also drew from the Baer ML212, another excellent design. I'm hoping for a finished weight between 63 to 65 lbs.


I contacted Ralf Patterson to see if he could build me a crossover like the one used in Deb's original cab from LDS in a 4 ohm version for this 1212/66 configuration. He built a beefy 1000 watt, 4 ohm, 800 Hz crossover for me which should work nicely with these drivers. Here are a couple shots of the drivers and crossover.



Here are a few construction photos. Bracing every 7" worked out well with the cab symmetry and should provide a very sturdy box. One other thing I wanted to try was Recex screws instead of tee nuts. The screws need more than 12mm thickness to get a proper bite so I made plywood reinforcement rings for the baffle cutouts. Not only will these provide a double thickness for screw mounts but I'm guessing they will also help suppress vibration on the baffle much like dead ringers do on a bass drum. We'll see.



This one gives a good view of the bracing.


Here's a couple shots all glued up with the edges rounded. At this stage, the box weighs 32.8 lbs.

[cableguy]

was there something you didn't like about the 18sound mid in the fEARfuls? I have a 12/6-12/sub and one 18sound covers the mids/highs all I would ever need. Anyway, sweet looking build. The 2 3012LFs provide a great yet tight low end.

[mikeddd]

I do believe I saw your sketch/schematic in another thread sometime back and loved it. Still seriously loving it and to see it come to fruition is a beautiful thing! The bracing scheme looks extremely solid; you can never have too much bracing unless it's a solid block of wood!

Good on you for going with the tweeterless build. I only just got my 15/6/1 (to spec) running today and I can say that I really don't think I'll make much use of the tweet at all. But better to have it and not need it, I guess. Playing my passive Jazz basses into it, the only thing the tweet is putting out is amp hiss, really. The mid on the other hand...how did I ever live without a mid-equipped cab?

Your cab is looking GREAT. Very solid. Can't wait for more pics! Good luck.

[rpsands]

What's the deal with the round hole in the side?

[mikeddd]

Originally Posted by rpsands

What's the deal with the round hole in the side?

Round handle? There are two of these holes; one on each side in the same place. What I want to know is why the back panel has random letters in all the boxes. Was my two year old son over your house too? He wrote all over my fEARful. Duratex took care of all that. :d

[will33]

I'm guessing his choice of handles have round cups.

[5StringPocket]

Originally Posted by cableguy >
Was there something you didn't like about the 18sound mid in the fEARfuls?

I have a pair of 15/6/1 cabs with the 18Sound mid and ASD1001 HF driver. It's an excellent mid driver, very strong with a pretty flat bandpass response. I wanted to try the Faitals for two reasons. First, they have a more extended high frequency response which is desirable in a 2-way without tweeter. Second, their response has a dip around 2.5k and a peak around 6.5k which is what I would do with eq to back off those upper mids a bit and add a bit of clarity to the treble. I wanted to see if their out of the box response was more to my liking with less eq. I know what the 6ND410 is like and wanted to check out this driver to satisfy my curiosity.

Originally Posted by rpsands >
What's the deal with the round hole in the side?

The round hole is for a 4-sided plastic handle which should be nice for grappling this cab at different angles. I usually stay away from plastic and use the Dayton Audio large steel bar handles but I think these will work out well.
Dayton Audio PH114 Plastic Pocket Handle 4-Sided
They provide comfortable hand holds and when carrying this cab the force will be on the side pulling the cab toward my chest with one handle while supporting the weight of the cab at the bottom on the other side. These handles save 1 lb of weight, have a pretty small cross section and snug fit, and are actually pretty solid. I bought a bondo kit with epoxy resin and fiberglass cloth to stiffen up the surface facing inward. Pictures on this to follow.

Originally Posted by mikeddd >
What I want to know is why the back panel has random letters in all the boxes. Was my two year old son over your house too? He wrote all over my fEARful. Duratex took care of all that.

I haven't seen your son in my garage but Duratex is a great cover up. The letters are all in the interior bracing grid to identify the individual foam pieces cut to fit. I rolled on 4 coats of Duratex this weekend. Glueing in the foam dampening and mounting the cabinet hardware is the next stage of assembly. I'll post up when I get some pics.

[Robby Hoinsky]

Interesting build. Looks very solid with all that bracing. I'm very excited to see how it ends up sounding. I'm a little concerned about the two inductors being so close on your crossover board though. They really should be farther apart and at 90°.

Robby

[5StringPocket]

I was wondering about that too but figured the two coils are in series and supposed to be coupled. I'll check with Ralf Patterson about that. He has built a lot of crossovers and should be aware of this.

Another detail I'm curious about is the sensitivity match between woofer and mid. The Alpha 6A at 93.6 dB/w is 1.9 dB less than the 3012LF at 95.5 db/w and seems to balance well with it. Likewise, the Faital W6N8-120 at 95 dB/w is 2.0 dB less than the custom 12" woofer (97 dB/w) in the Baer ML212 and also seems to balance well. I'm hoping the Faital sensitivity will balance well as is with the 3012LF. I can put in a 4 ohm -1.8dB resistor pad if needed but Ralf suggested I try it with the crossover as is before adding anything. I'm going to try this out first with my Streamliner 900 amp which seems to tame the mids somewhat so it might be fine and just need some bass cut and a boost at 600 Hz to line things up.

[Derek Kiernan]

Cheat sheet:

[Oobly]

At first glance it looked like the crossover and wires are too skinny for 1000W... then I scaled it according the to speaker sizes and realised it's probably okay.

[staindbass]

nice cabinet ! it will sound great.

[5StringPocket]

The cheat sheet applies when you need to minimize inductor coupling such as between woofer and mid sections. I contacted Patterson Audio and found out the two large iron core inductors on my crossover are in parallel and coupled. It seems reasonable when using off the shelf components you sometimes need to improvise. In this case perhaps one inductor with the desired (x)mH wouldn't quite handle the required current, so a pair of (2x)mH in parallel were used instead. This is similar to the use of parallel resistors in an L-pad.

I used 2" polyurethane foam for most of the insulation. Hobby Lobby sells it for upholstery cushioning. It cuts like bread with an electric carving knife. I cut it slightly oversized so the pieces were snug but not too compressed. I laid out all the pieces to aid assembly and used a shot of spray adhesive on the back of the foam and on the wood to keep them secure. A can of WD-40 to spray your gloves with is handy to keep things from getting too sticky.


With the foam in place, I mounted the side handles and castors. One of the foam circle cutouts removed for the handles was divided into two thinner slices which were glued onto the handles inner surface. The mid chamber was then filled with Acoustistuff polyfill. Here is the cabinet ready for final assembly. At this point it weighs 39.7 lbs.

[Boostedrex]

Coming together nicely! The attention to detail is admirable to say the least. Looking forward to seeing the finished product. Nice to see someone else who is using Faital Pro drivers. I've had EXCELLENT results from the 3 different drivers of theirs that I've used in the past. Though none of them were a 6.5" midrange.

[Robby Hoinsky]

Some nice work there. How are you liking the 4 sided handles so far? I've heard mixed reviews of them.

Robby

[rpsands]

I think you might find that poly foam a bit thick for what you're doing. Watch out for the cab sounding overdamped. Mileage varies on this of course

[mikeddd]

The amount of time it must have took to cut each piece of foam exactly to size is mind-boggling. I wish I had so much free time. Just jealous. Dumb question: Does the midchamber have a divider or is it one chamber? I don't see a divider in any of the pics. I'd imagine it's divided, but I gott ask anyway.

It's looking GREAT so far!

[Robby Hoinsky]

Originally Posted by mikeddd

The amount of time it must have took to cut each piece of foam exactly to size is mind-boggling. I wish I had so much free time. Just jealous. Dumb question: Does the midchamber have a divider or is it one chamber? I don't see a divider in any of the pics. I'd imagine it's divided, but I gott ask anyway.

It's looking GREAT so far!

It probably isn't divided. No real reason to since they are outputting the same signal.

Robby

[mikeddd]

Makes sense, Robby. But I'd be worried about reflections and interaction from two high-powered open back drivers like that.

[rpsands]

Originally Posted by mikeddd

Makes sense, Robby. But I'd be worried about reflections and interaction from two high-powered open back drivers like that.

I imagine he's stuffing the heck out of that mid box