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Multi-Way Conventional loudspeakers with crossovers

DIY PMC MB2 clone
DIY PMC MB2 clone
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Old 12th October 2017, 09:51 PM   #81
Charles Darwin is online now Charles Darwin  United Kingdom
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I think the felt should be ok.

Heavy is good. How thick is it?
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Old 12th October 2017, 10:07 PM   #82
wae is offline wae  Netherlands
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No screws??
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"If i ain't broken, DON'T fix it"
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Old 13th October 2017, 09:33 AM   #83
Heraldo Jones is offline Heraldo Jones
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They are looking great, waiting for the finished project and your opinion
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Old 13th October 2017, 03:06 PM   #84
WalterPPK is offline WalterPPK  Netherlands
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Thanks Heraldo! I hope it's worth all the trouble Yesterday I ordered the MiniDSP OpenDRC-DA8 .This should be the perfect tool to get a good sound.

Charles, the felt is 15mm thick. Maybe it's better to use 30mm eggcrate foam? What about stuffing, or lining on top of the felt/eggcrate foam, the box with sheep wool to lower Fb?

Wae, No I used lamellos. I did use some screws in the 25mm strips that hold the baffle. Unfortunately I placed screws where the screws of the baffle go through. They're blocked. Stupid mistake which I have to fix with some chiseling and 2C woodfiller

Last edited by WalterPPK; 13th October 2017 at 03:12 PM.
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Old 14th October 2017, 01:17 AM   #85
Charles Darwin is online now Charles Darwin  United Kingdom
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Do not overstuff a ported box.
They kinda need space to breath and obviously a direct path from woofer cone to port unobstructed by stuffing/damping.

You do not want to lower Fb since woofer, box volume and port are parts of a tuned system. Can't change one without affecting the others.
The idea of damping in a ported box is to absorb as much midrange as possible to stop it from exiting the box either via the port or through the woofer cones.
You do not want it to affect anything below about 150-200Hz because that is were the port starts to get involved.

I'd line the box with the felt but not the baffle and try some of that 30mm eggcrate foam on the back wall behind the woofers.
You can just stick in there loose and listen before making up your mind which sounds best.
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Old 14th October 2017, 02:03 PM   #86
WalterPPK is offline WalterPPK  Netherlands
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Thanks Charles, some tinkering will be done with the damping. Today I repaired two inserts that were to close to the edge. The wood broke. Glued in two oak pieces and routed them after installing the inserts. The clue is to support the wood with a clamp before installing the insert. The brace is not perfectly in the middle. Next time I make the back support brace for the baffle out of one sheet mdf. I test fitted the baffle with the Volt and it fits perfectly. The back of the volt will rest against a felt strip.

Click the image to open in full size.

Last edited by WalterPPK; 14th October 2017 at 02:08 PM.
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Old 14th October 2017, 02:34 PM   #87
andy19191 is offline andy19191  Europe
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Just to clarify a couple of points.

Firstly, the resonance provided by the ports is incompressible and so a clear path between woofers and ports is unimportant. The incompressible slug of air oscillating in the ports is driven by the woofers raising and lowering the pressure in the cabinet. When the air is entering the cabinet what is around is relatively unimportant because the air will enter as a jet but when it is sucking it will draw air from all directions around the port mouth and this should be as clear as practical. Rounding the mouth will also help significantly. Placing foam near the mouth will use some of the available pressure drop to suck air through the foam leaving less to drive the resonance.

Secondly, you have a large cabinet with (I think?) the woofers significantly driving the lowest internal cabinet modes. This will need damping and placing damping materials on the walls where the velocity is zero will do little to help. You need it in the middle where the velocity is a maximum.
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Old 15th October 2017, 06:25 PM   #88
WalterPPK is offline WalterPPK  Netherlands
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I understand Andy, so lightly stuffing the cabinet with some sheepswool will benefit the damping of the 1/4 wavelength standing waves? (horizontal 134hz, vertical 230hz).

The boxes are rather big. Drying the filler in the sun:

Click the image to open in full size.
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Old 15th October 2017, 06:34 PM   #89
WalterPPK is offline WalterPPK  Netherlands
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Reading this: chamfering driver holes I was wondering if it would be better to route a large 45 degree chamfer between the woofer mounting holes at the back of the baffle

Last edited by WalterPPK; 15th October 2017 at 06:36 PM.
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Old 15th October 2017, 06:53 PM   #90
Andersonix is offline Andersonix  Sweden
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DIY PMC MB2 clone
Felt is too dense as a stufing, and it will also be a narrow band absorber, likely in the highs only, so prob not that good as a midrange absorber.
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