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Old 8th February 2013, 02:18 PM   #1
OllBoll is offline OllBoll  Sweden
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Default Sphere enclosure: Rounding magnet rear?

Hello there.

I'm planning to build myself a sealed spherical midrange enclosure by using two IKEA bowls =)

What I wonder though is this: My mid (TD6M) has a ginormous magnet and there exists an IKEA bowl of smaller size ( green in picture ) that i could mount on the backside to eliminate the large flat surface and make it rounded.

So... would this be a good idea, a bad idea or completely unnecessary?

Thanks in advance,
Olle
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Old 8th February 2013, 02:47 PM   #2
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Cover the magnet with felt or compressed waste, it doesn't need any reflective surface added ( and it eats volume, too )
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Old 8th February 2013, 05:37 PM   #3
AllenB is offline AllenB  Australia
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In my opinion, the main benefit of a spherical enclosure is on the outside of it, not the inside, and no I probably wouldn't bother with the smaller reflector.
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Old 8th February 2013, 05:43 PM   #4
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B&W do in their teardrop shape.

I think you'll find you need all the space you can get. My Ik bowls come in at a surprisingly low volume.

Don't forget a flat to mount the driver.
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Old 8th February 2013, 06:19 PM   #5
OllBoll is offline OllBoll  Sweden
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I thought about the teardrop but in my case there isn't enough space to do that =) It will be upwards mounted like the pluto but with a 10 inch woofer instead and then this spherical midrange on top. A teardrop would be too high making the distance between the woofer and midrange unnecessarily long.

Volume shouldn't be a problem wherever I have the internal reflector or not since this is a dedicated midrange that will cover 300-400 and upwards.

Though the general conclusion seems to be that the reflector is unnecessary it would be quite cheap to just buy a bowl, get some duct tape and then test with and without =)

And yes, the internals is only half of why I'm considering a sphere, should have a nice response on the outside. I've wondered about if covering the whole outside in wool felt would be overkill with a sphere or if it still is a good idea.

Last edited by OllBoll; 8th February 2013 at 06:23 PM.
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Old 8th February 2013, 06:42 PM   #6
OllBoll is offline OllBoll  Sweden
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Since it is isn't exactly a conventional speaker I thought I'd show a drawing of how it will look =)

The idea is to use an upwards firing U-frame in the bass region where room dominates and where it would be hard to build a big enough box to counter the long wavelengths and then use this sealed midrange on top. Currently my U-frame experiments have given promising results but if they in the end fail i'll just seal the bottom of the U-frame and turn it into a sealed woofer.
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Old 8th February 2013, 08:09 PM   #7
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So the "woofer" is going to fire onto the bowl?
What is the highest freq the woofer will reproduce?

Make the internal of the Ikea bowl as absorptive as possible.
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Old 8th February 2013, 11:42 PM   #8
OllBoll is offline OllBoll  Sweden
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Quote:
Originally Posted by bear View Post
So the "woofer" is going to fire onto the bowl?
What is the highest freq the woofer will reproduce?

Make the internal of the Ikea bowl as absorptive as possible.
Yep. It will be crossed acoustically at 300 with LR2 that becomes LR4 at 600 or LR4 from the start at 300. Time alignment and crossover slope matching will be done through DSP.

And yes, the inside of the bowl will be filled to the brim with wool =)
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Old 9th February 2013, 02:57 AM   #9
sreten is offline sreten  United Kingdom
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Hi,

Adding the rounded section to the back of the driver won't fix
the fundamental issues regarding the front of the magnet so
as others have said simply well stuff the sealed midrange.

rgds, sreten.
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Old 9th February 2013, 04:47 AM   #10
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Quote:
Originally Posted by OllBoll View Post
Since it is isn't exactly a conventional speaker I thought I'd show a drawing of how it will look =)

The idea is to use an upwards firing U-frame in the bass region where room dominates and where it would be hard to build a big enough box to counter the long wavelengths and then use this sealed midrange on top. Currently my U-frame experiments have given promising results but if they in the end fail i'll just seal the bottom of the U-frame and turn it into a sealed woofer.
U-frame pointing up places dipole null in horizontal plane; at best with open end close to floor quasi-cardioid with slot loading forms. Sealed is likely best approach.

Even small mid will start beaming around 3kHz, causing bright reflection from ceiling.

Good luck improving SL's Pluto this way.
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