New three-way monkey coffins

[Paul Carmody]

The circle jig is awesome. I think that's the first time I've seen someone use a threaded rod to move the pivot point.

Do you find you have to do test cuts before routing the baffle, or do you have it dialed in to certain diameters somehow?

[DeZZar]

One day when I get around to making a better one I'll have a measurement system dialled in for it so its just a case of setting it like a table saw and cutting - but for now I generally measure it, then do a quick little test cut on some scrap and then cut all the circles I need for that radius before moving on to the next size.

[Paulie]

Super Awesome circle jig!

[LOUT]

Are these going to be left uncovered to show off the drivers or do you also have a grill design planned?

[DeZZar]

These will end up in a house with small kids so they'll get a grill. It will just press fit over the raised baffle.

[Wolf]

The only problem with that Circle jig is the single fact that adjustment can take a considerable amount of time. I suppose it's no different than a C-clamp, but the longer the adjustment, the longer the time between cuts. I'd be tempted to have a crank rather than knob for adjustment, or a way to facilitate the aid of a drill/driver for speed change. A spring loaded slip-joint with inside threads would be ideal, and likely 3D printable.

When i made mine, this why i did not go with all thread.

Just spitballing....
Wolf

[DeZZar]

Its a little better because its actually more like an Acme thread - not like a normal bolt - so it has a much longer pitch to it - it doesn't take long at all - but then again I'm not really going from one extreme to the other. Usually tweeter first, then midrange then woofer so from a change in radius point of view its just a few inches at a time. If I was needing to go from one end to the other I might create a thread release kind of mechanism where you can just press it down and slide it the whole way manually - but its never really been an issue.

[Steve Lee]

Yeah, but that dust collector and flashlight router-base, dude!

[Wolf]

I have dust collecting on my build as well.
Wolf

[davidroberts]

The circle jig is awesome. I think that's the first time I've seen someone use a threaded rod to move the pivot point.

Do you find you have to do test cuts before routing the baffle, or do you have it dialed in to certain diameters somehow?

Should be able to measure from the outside of the bit to the center of the pin. Craftsman used to have very simple jig. We had several of them at the car audio shop that I worked at in my younger days.

[Paul Carmody]

Oh I know how they work. It's how I used to do it before I broke down and bought a Jasper Jig. I really don't like that JJs are so fragile, but it's hard to beat how easy and quick they are to use.

[dkalsi]

DeZZar - did you use VituixCAD to determine ideal driver placement/offset - if so, were you specifying the enclosure width based on the protruding baffle, or the full width of the speaker?

[PWR RYD]

I have dust collecting on my build as well.
Wolf

Classic!

[DeZZar]

did you use VituixCAD to determine ideal driver placement/offset - if so, were you specifying the enclosure width based on the protruding baffle, or the full width of the speaker?

Yes. For these I specified the width based on the protruding surface. I figured there might be some unknown oddities to deal with based on the stepped edges but there isn't really a way to model that exactly.

Just off centre seemed best for these. The "best" positions are usually impractical so it's always a game of compromises.

[Ryan]

I am inspired to start my build, just need lumber prices to fall before August! Great work!

[DeZZar]

Hi All,

Little bit of progress on this build over the holidays so thought I would provide a bit of an update.

After modelling and trying a few different crossovers we've landed here for now:




Keeping it fairly simple all round with 2nd order filters and just a third order on the midrange low pass with a notch to really suppress the high frequency breakup. Here is the expected results from the modelling:



As I was driving interstate over the holidays to visit family I took the opportunity to deliver these to their new home in their current unfinished state as it would be quite some time before I had another opportunity. So they just remain raw boxes at the moment and in future visits they'll get their veneer and finishing touches.

We spent some time listening to the above crossover in a prototype state both in my workshop and in their final resting place. In short, they sound incredible even at this stage. I wasn't able to take a complete set of measurements with this crossover but based on the listening tests and an on-axis measurement to confirm the results we'll go ahead an assemble this crossover with some cheaper parts for further listening before upping the parts quality for a final build.

Workshop listening session:


Prototype crossovers - this is one of the iterations under test.

[DeZZar]

Here are the on-axis results. These measurements were taken outside at night and I was able to get the speaker quite high off the ground for a 9ms gate time - measured 1m on tweeter axis. There were some pesky crickets singing away in the background but I don't think they affected the results.



Interestingly the modelling called for the tweeter and midrange to be wired in normal polarity and the woofer reversed but when measured it was clear the tweeter needed to be inverted as well. Turns out we had been listening to them all this time with the deep null at 2.5K - they sounded great but we did notice some strange 'honkiness' to vocals on certain tracks - turns out this was the cause.

The other key difference is the model was predicting a rise in the tweeter response (akin to its raw measured nature) but in reality the on axis result is a little closer to the predicted listening window. There might be some room to bring the tweeter back up a little but for now it sounds very nice right where it is.

Here is the distortion from the above measurement. At 90db we are below 0.5% most of the time and well below 1% even considering the peaks across this range.


Sanity check on impedance results and we have a near on perfect match with the model:


Looks like we'd probably classify these as a 6ohm nominal load with a minimum of 4.2ohms.

All the parts arrived to assemble a proper prototype version of the crossover so more updates to come in due course.

[DeZZar]

Thought I would also add the CSD results...don't see enough of these...

[Wolf]

If it were me, I'd just invert the mid. This way the forward DC pulse of the woofer is kept intact for making impact sound right.
Wolf

[DeZZar]

Yeah I should have stated - that's exactly what I ended up doing!