Ikea salad bowls

[Ray P]

You may need a sandwich filling...

Cheese and Piccalilli be OK? It seems to be the de-facto standard on ths forum.

[stevieg]

Picalilli on the outside with the cheese in the middle. If you use Emmentaal you will have ready made ports.
Cheers Steve

[Morgan Jones]

Point to bear in mind with the salad bowls is that they are not necessarily hemispherical nor perfectly identically circular at the rim.

This was what I measured for my recently purchased Ikea salad bowls. Very definitely not a perfect hemisphere. But I don't suppose for one moment Blanda machined them by hand, she probably told a CNC machine to do the work. I found small differences (<0.1mm) between bowls.

They just fitted in my lathe, so I bored and rebated the hole for JX92S. MDF ring was added behind the hole to give the screws a bit more to bite into. Terminal plates are not yet made.

[brig001]

I should have measured mine before I built them, but mine are about 200mm diameter
The four are pretty close, probably within a mm of each other. I put the biggest at the front so the step isn’t visible

Brian

[Morgan Jones]

I thought the first bowls looked smaller!

I have a cunning plan for the valley where the two bowls will join; I shall wrap a length of 3mm diameter plastic belt round the loudspeaker to secure it to its stand, thereby concealing the join and serving a useful function.

[brig001]

Looking at your drawing, it doesn’t look like there’ll be a valley. The edges of mine were radiused so I taped sandpaper to the floor and rubbed the bowl on it until there was a flat that I could glue to. This also ensured that the edges were flat

I kept the valley as a “feature” - they’re mine and I can call it that

[Morgan Jones]

Ah, I failed to radius the edges in the drawing; there will be a valley. I only included gross features, so the dimple underneath was also neglected. I shall use your abrasive paper wheeze to remove the varnish and enable a strong joint.

[brig001]

A bit of an update

Was relying on the high pass filter on the amp to tame the 50Hz peak in my room response, but always found it tricky to set and the response was never ideal. These were the settings (on separate pages, so you have to imagine a bit):

2024-05-27 Pretty happy with this one high pass.png (65.06 KiB) Viewed 4671 times

2024-05-27 Pretty happy with this one.png (100.8 KiB) Viewed 4671 times

[brig001]

Changed to using a PEQ to deal with the peak and made the high pass more gradual:

2024-06-15 Tried a 50Hz notch instead high pass.png (65.4 KiB) Viewed 4669 times

2024-06-15 Tried a 50Hz notch instead.png (103.17 KiB) Viewed 4669 times

Much better control and now as the bass goes lower, it fades rather than just disappearing. 30Hz may be a bit low, but the drivers don’t seem fussed, so a definite improvement

Brian

[Morgan Jones]

That's interesting. I was expecting to need something to take the sting out of the JX92S 12kHz peaks I've previously measured, but I was also half expecting to need a lot of baffle step compensation which you don't appear to have needed. I've made and fitted rings behind the holes for the drivers so that the (20mm long) screws now have something to bite into and I've made one of the rear panel plates for connections, but not the other.

Progress has been delayed by buying a Telequipment D1011 10MHz oscilloscope on Sunday for a friend that turned out to need fixing, and even that had to move a Solartron 7075 DMM (presently in pieces) out the way. Next up, I'll finish modifying the DMM (to clear space), and the Helmholtz coils need to be used, then I can get back to the loudspeakers. For initial testing, I'll put them on conventional stands. Of course, they'll want to roll off, but if I make four 30mm long posts per loudspeaker, screwed to the stand and with self-adhesive hemispherical feet at their other end, that should allow the loudspeaker to be supported by the posts. I'm quite keen to make swarf at the moment because it's a lot cooler there than in the lab.

[brig001]

I initially tried the Purify method to get rid of the 6kHz spike, but couldn’t get the tuning right. Might have another go one day

Regarding baffle step, my speakers are about 20cm from the back wall, so I think that helps