Concept, Beolab 11 style isobaric sub using Ikea Blanda metal bowls. - Page 4 - diyAudio
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Old 30th June 2012, 09:57 AM   #31
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Quick sketch, but to scale (magnet size was a guess)

4x5" drivers, or 2x6"

I don't personally like the larger gap

Click the image to open in full size.
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Old 30th June 2012, 11:11 AM   #32
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You have the 5"ers mounted isobarically - that isn't what I suggested, and won't give the same performance as the simulations I posted either.
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Old 30th June 2012, 11:18 AM   #33
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ok, two outward facing drivers in each half sphere?

Without hogging its on dsp (2in 4out) is there a way to wire this up so the drivers can share the signal?
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Old 30th June 2012, 12:00 PM   #34
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Quote:
Originally Posted by Studio Au View Post
ok, two outward facing drivers in each half sphere?
Yep.

Quote:
Originally Posted by Studio Au View Post
Without hogging its on dsp (2in 4out) is there a way to wire this up so the drivers can share the signal?
A series-parallel arrangement of all 4 would give a 4 ohm (nominal) load for a single amplifier channel.
You could wire each pair in series to give an 8ohm load for 2 channels of amplification.

For the 6"ers, you'd have either a single 8ohm or 2ohm, or two lots of 4 ohm if you have a stereo amplifier.

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Old 30th June 2012, 02:29 PM   #35
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You will find it hard, if not impossible, to port this small of an enclosure to a low frequency.

If I was fixated on this project I would use a pair of sealed long excursion 8s or 10s, and either a Linkwitz Transform or an ELF crossover (Bag End).
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Old 2nd July 2012, 07:49 PM   #36
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is this due to the small enclosure or the small port size?

Could the port be routed through the other bowl, imagine a snake twisting through both.

I think lots can be done with the MiniDSP, due you know of a 8 or 10" sub that can work in a sealed 11l enclosure?
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Old 2nd July 2012, 08:01 PM   #37
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The problem with small boxes and ported subs is that to get decent clean output you need to have a good amount of port area (meaning longer port needed), and the sub use dictates low tuning (longer port needed again). So fitting the port into the box becomes physically impossible.
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Old 2nd July 2012, 08:15 PM   #38
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"due you know of a 8 or 10" sub that can work in a sealed 11l enclosure? "

Any driver with a good x-max will do. The Qtc will be quite high, that's what the Linkwitz Transform is for.

Some of the Velodyne and Bag End designs have sealed system resonances around 80hz or so.
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Old 2nd July 2012, 08:22 PM   #39
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Nice drawings P10. Should clear up come comments in several threads.
My take:
isobarik is an expensive way to not buy a more expensive driver.

The idea of big metal bowls gives me shivers, but as subs, well it's the volume that matters. The ones in the photo look WAY too small to be subs. Please do your T/S calculations.
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Old 2nd July 2012, 08:48 PM   #40
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We are talking about 11" bowls, 5" drivers, and the word "sub" in the same thread?

Here is an idea. Pull up a copy of WinISD. Pick any speaker and do a sim of a sealed box. Make the box 11L. Then go into the editor and keep changing Fs and Qts until you get numbers that look like a sub. Look around for drivers like that. When you find one, let us all know.

For what I consider a real sub, the Peerless 12" in 60L is one of the smallest and one of the cleanest. Very good efforts have been done with several 8's, but the total box size goes up a lot. 200L is not an unreasonable size for a sub.

Subs don't have to be in the same room. Only their output. They can be in attics, adjacent rooms, under the floor, outside. Creativity here is the rule.
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