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Another Ikea Bowl Speaker

Posted 3rd February 2013 at 12:04 PM by googlyone

I stumbled on the people making speakers from the Ikea bowls. It kind of inspired me as the speakers were truly different and bizarre, but at the same time something completely different.

So I had to make some.

I fumbled around in the cupboard and came up with three choices of woofers that would do OK in a small enclosure - and after a few measurements and stuff settled on a pair of old Vifa M13SG-09-16 drivers. These were pretty well suited to an enclosure of a bit over 8 litres.

This drove me to the larger bowl, a 28cm one.

This is how they came out...

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To fit the driver I simply routed a rebate - and then cut the inside out.

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The material of the bowl was quite thin once I had finished routing things - so I cut out a circle of ply and glued it to the inside of the bowl. I had to go out for the evening at that point so I simply used acrylic filler as an adhesive. It works very well if you have the time to wait...

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I failed to take photos of the way I attached these speakers together. In one of her typical throwaway lines, Anne my wife said "why don't you use dowels down the edges of the bowl?". Easier said than done whe you consider the bowl is about 8mm thick at the edges.

On thinking though, I concluded there was some wisdom to this statement - but instead of dowels I used nails as pins. I used about 1.5mm nails, and did the following:
- drilled four holes on one of the bowls,
- Pushed nails into these
- But cut them off about 2mm above the edge of the bowl
- Then aligned and phshed the top bowl on, resulting in the short nail ends marking the top bowl
- Drilled the top bowl on the marks
- Pulled out the short nails and replaced with longer ones
- Pushed the bowl halves together

Then I used fibreglass around the inside of the bowl - using three layers of glass sheet. It came out as strong as a brick shithouse.

I tested them by hanging from the roof...
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The response of the Vifa MG13 is bery very polite, which is why I bought them in the first place. These ones were intended to be used as an MTM, in this case I have gone retro and made a 16 Ohm speaker!

The tweeter I used again came from the cupboard. This is actually a car tweeter that I found a couple of pairs of. In its day it was quite expensive (about $45 a pair heading on 10 years ago). On measuring these I could see why, good flay response, low Q and clean response.

The crossover is pretty conventional:
- The woofer starts rolling off at between 4 and 5KHz
- The tweeter start rolling off in the region of 3KHz (resonance at 1800 Hz)
- I picked 4.1KHz as the crossover point, and used a first order electrical, but the rolloff of the drivers would make this more like 2nd order.
- The tweeter got a trap to really flatten out the 1.8Khz impedance peak, it was not bad but in my experience it is worth knocking this peak out if you really want a crossover to do what you would expect it to do.
- The bass driver got a zobel network, again this might be overkill as this driver is well behaved, but I did want to roll the driver off, and I did not want the 1st order crossover battling an increasing impedance of the driver.

I chose to mount the crossover inside the "bowl" box, tight at the back, aiming to counterbalance the weight of the speaker at the front. I did this by gluing all the parts of the crossover to the speaker port, and porting the box at the back. This almost succeeded, but did result in a pretty odd three dimemsional crossover wrapped around a speaker port!

Note: I will never take a photo of the crossover, as whilst it is robust, it is dog ugly.

So how to hold them up?
- I thought the bowl boxes looked pretty 60's retro.
- So I thought a really 60's retro stand is in order.
- My wife wandered out and exclaimed "they look like space rockets". Good - exactly the comment I was looking for.
- Note the doorstops used as detail on the top and bottom of the pole....

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The speakers simply sit on top of these stands. The tweeter plugs into sockets on the back of the bowl speaker.

How do they work?

I am actually very surprised.

The frequency response is very well behaved - within 3dB out to somewhere near 15KHz where there is a slight rise before tapering off toward 20KHz. A minor blemish on an otherwise excellent measured response, I dont think this will be an issue with my age.

On listening they are great. If odd to look at and definitely not child proof.

Well there you go!
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  1. Old Comment
    KMossman's Avatar
    who knew Ikea has a new product range!

    Nice blog!
    Posted 5th February 2013 at 12:05 AM by KMossman KMossman is offline

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