Alpair 7.3eN/12pw WAW build

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I’ve been enjoying my homebrew WAW speakers for a couple of years. When I built them I knew absolutely nothing about speaker design so I looked around for a design I could copy. Omega speakers had a good reputation, so I made a version of one of his Outlaw speakers using a Fostex F120a and a Dayton 8” sub. It sounded good enough that I was satisfied for a while but, reliable as the sunrise, the itch for something better soon reared its expensive head so I started a thread:

Am I getting the most from my Fostex F120a WAW?

The short answer to my question was yes.

And no.

Lots of reading and advice later, I realized that I still didn’t know a thing about speaker design so I decided to try one of the Planet 10 designs using Mark Audio drivers. Dave was incredibly patient and generous with his knowledge, both on the thread and in 50-odd emails during the build process. This weekend I finished gluing up the cabinets, installed the drivers and…..wow.

The cabinets aren’t veneered yet, and the drivers still have some breaking in to do, but these are already in an entirely different league from my previous speakers. So much more dynamic, with absolutely no shout. The bass I was so concerned about is there in profusion. I really didn’t think the 12pw would compare to the Dayton sub and I was right, but in the wrong way. There is so much bass that I may have to plug up a vent or two to settle it down. I’ll play with positioning and give them more time to break in first, but this driver/enclosure combination defies imagination. They are also MUCH faster than the Daytons. I had the 7.3 enclosures done a week or so ago and, paired with them, the Dayton sounded geologically slow. The speed and extended range of the 12pw, on the other hand, matches beautifully with the 7.3. Almost like they were meant to work together…..hmm.

The woodwork is far from perfect, but I don’t think my mistakes have any effect on the sound. They were time consuming but not especially difficult to make, though I will admit that my newly-acquired track saw made it infinitely easier than it would have been using my contractor-grade table saw. Safer too.

I also made some PLLXOs as part of this project. They were done a few weeks ago and made a HUGE difference from the start, even with the old speakers. With the new drivers I can really hear the extended range of the 12pw. The midrange is filled out more completely, without a discernable gap in the handoff from one driver to the other.


Now to select the veneer, and decide whether I’m going to do the sides in black (think Devore O/96) or veneer them the same as the front baffle.
 

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Dude, I've built more than a few pair of "traps" myself, and you could have fooled me with the quality of the woodwork - they are not a simple monkey coffin, that's for sure.

I'd think at least of veneering the fronts and beveled port sections. It'll take lots filler and coats of high solids primer to fill the exposed edge grain of the BB ply. Of coarse, trimming out the veneer around the port slots takes some time and patience as well.
 
Dude, I've built more than a few pair of "traps" myself, and you could have fooled me with the quality of the woodwork - they are not a simple monkey coffin, that's for sure.

I'd think at least of veneering the fronts and beveled port sections. It'll take lots filler and coats of high solids primer to fill the exposed edge grain of the BB ply. Of coarse, trimming out the veneer around the port slots takes some time and patience as well.

Thanks, Chris! I'm happy overall.

The main mistake I made was not building the lower ones first, then using that footprint to make sure the upper match. I did them separately, and my angles were not dead nuts, so the footprints are off by a mm or two (or three) at the rear corners.

The other issue was getting the tops and bottoms of the upper box even with the baffle where the driver cut out is. Cant just run the trim bit across the front without having anything for the bearing to ride on, so I had to do it freehand and sand. Ended up digging too deep in places.

I agree on the front and bevel veneering. It'd be tough to fill and polish the edges, and the pine I used for the spacers might not look great over time. I think a nice cherry or walnut will be lovely. Might stain the back and sides black, but still translucent enough to see the grain. I'll experiment and see. Might just veneer the whole thing.
 
The woodwork is far from perfect, but I don’t think my mistakes have any effect on the sound. They were time consuming but not especially difficult to make, though I will admit that my newly-acquired track saw made it infinitely easier than it would have been using my contractor-grade table saw. Safer too.
Mate! There's not a lot wrong with that woodwork. The cabinets look good and when veneered I think they will shine.
I'm a little surprised at the size of the small enclosure though as I think 9 liters is the recommended volume for the 7.3's.
 
frugal-phile™
Joined 2001
Paid Member
I should also say that the volume of the midTL is not critical, one can increase the height to of the box to do that. Minimal height was drawn to ensure minimal A12pw-A12pw centre-to-centre when a second set of bass cabinets is flipped upside down on top of what Quattrofish already has to make a tall MTM.

dave
 
Thanks for the kind words, all.

Dave, any chance you'd be willing to post the drawing for the 7.3 midTL? No stress if not.

Quattrofish, can you share details of your pllxo? Beautiful work on your cabinets. I share your enthusiasm for the 12pw.

Thanks.

The PLLXO consists of:
Low Pass: inline 10k resistor and 52nf shunting capacitor.
High Pass: 5.2nf inline capacitor

I was shooting for 53 and 5.3, as the impedances of my pre and power amps dictated that for a 300hz crossover, but the selection of caps I had only got me to 52. This puts the crossover a little high, but hopefully not high enough to run afoul of the 1/4 wavelength rule for acoustic centers. I'll take a look at that. Once I am certain that everything is well broken in I'll need to try some measurements and adjust from there. I just bought a mic, but sadly I have no idea how to properly measure. Time for more research!
 
I'm not going to say that I measured properly, but I measured.

And I measured. And I shifted the speakers then measured again. And again.

My mic is properly calibrated from Cross Spectrum, but I don't have a boom mic so had to set it on a tripod on the couch. It was above the top of the rear cushions, exactly where my ear is when listening, but I realize it isn't ideal.

Anyway, the upper frequency results varied quite a bit depending on subtle tweaks. My guess is most of that is bad mic set up. The big bump at 60hz and trough at 80hz, however, were consistent. They are also quite audible, especially when playing music featuring double (stand-up) bass. Lots of resonance. I tried to test treat the nearby corner with couch cushions. It helped the 80hz trough, though not by much, and didn't touch the 60hz bump.

Any thoughts?
 

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Certainly room issues. 8 ft ceiling?

dave

Yup.

8'2", actually, but...yeah.

The room is 22' x 10'. I listen across the short axis. My position is about 7 feet from the side wall.

I doubt that stacked couch cushions (6' high, 1' thick) are ideal for low-frequency dampening, but I would have thought that they'd help more than they did. The lack of significant impact suggests that it isn't the corner so much as the room in general.

I'm glad I didn't go for that MTM we first discussed, with two 12pw. They would have resonated my house to pieces.

I'm also glad that I had as many hours on the 12pw as I did, because I almost blew them out of the cabinets the first time I measured. WAY too much current. No nasty noises then, or now, so I may have gotten away with it. Whew!
 
frugal-phile™
Joined 2001
Paid Member
The A7/12pw combo puts the A7 about 34" off the ground

Without a base under the A12pw cabinet, about 32.5” (823mm). A bass easily adds 3-4”.

There is a variation of the design that trades height for despth so that they could be stand mounted:

MK12pwxwT-SM.jpg


Planset subscription would inclde me doing smaller volume boxes as well. Plansets are always growing :^)

dave
 
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