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Old 3rd June 2013, 09:05 PM   #11
bjorno is offline bjorno  Sweden
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Hi,

Wall-sub:

b
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Old 4th June 2013, 04:36 AM   #12
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Even if you can find a bass unit that will fit into a shallow depth, there should at least be enough space for damping material on the rear wall. Otherwise, assuming a paper cone, the rear wave is reflected off the rear wall and through the cone. Even if the cone is of a material that won't allow sound to pass through it, I would still think the cone very close to the rear wall would cause problems.

Regards,
Pete
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Old 4th June 2013, 05:39 AM   #13
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Yes, that is one of the first considerations to be done. That's why I suggested little
stiff cones which have more impact, i.e. find less air resistance . I was thinking of some side ( of the box ) mounting or inclined respect to the wall . Side mounting, one each side and one with the magnet in sight, in BR with slotted port ( heavily EQ'ed ). Adding some mass to the cone might help in lowering Fs ( and efficiency )
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Old 4th June 2013, 11:54 AM   #14
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Originally Posted by cT equals piD View Post
Even if the cone is of a material that won't allow sound to pass through it, I would still think the cone very close to the rear wall would cause problems.

Regards,
Pete
There is a cone material which does not allow sound to pass through it?
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Old 4th June 2013, 02:21 PM   #15
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Originally Posted by Charles Darwin View Post
There is a cone material which does not allow sound to pass through it?
Polypropylene? That is a kind of plastic resin. I really don't know for sure, but I would think that plastic is relatively much more impervious to sound passing thru it. Strangely enough, it seems that all materials can transmit some sound energy.

-Pete

Last edited by cT equals piD; 4th June 2013 at 02:23 PM. Reason: typo
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Old 4th June 2013, 03:20 PM   #16
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I'd find it even stranger if polyprop in the thickness used for cones would have any sound blocking properties.
Surely it would be cheaper for studios to be lined with that rather then going through the cost and hassle of building a floating room within a room.
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Old 4th June 2013, 06:23 PM   #17
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Quote:
Originally Posted by cT equals piD View Post
Even if you can find a bass unit that will fit into a shallow depth, there should at least be enough space for damping material on the rear wall. Otherwise, assuming a paper cone, the rear wave is reflected off the rear wall and through the cone. Even if the cone is of a material that won't allow sound to pass through it, I would still think the cone very close to the rear wall would cause problems.

Regards,
Pete
Pete,
The OP stated in the OP "The satellites run to 150Hz or so and the woofer enclosure will take over from there."

The wavelength of 150 Hz is 7.5 feet long, "damping material " on the rear wall will have virtually no effect in reflected waves at that low of frequency.
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Old 5th June 2013, 01:43 AM   #18
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Originally Posted by weltersys View Post
Pete,
The OP stated in the OP "The satellites run to 150Hz or so and the woofer enclosure will take over from there."

The wavelength of 150 Hz is 7.5 feet long, "damping material " on the rear wall will have virtually no effect in reflected waves at that low of frequency.
Good point. So that means the wave reflected off of the rear wall is very close to 180 degrees out of phase with the sound radiated into free air. Then also there is some cancellation as a result of that that nothing can be done about. Would you agree?

The author of the book that I am referring to about this subject of the wave reflected off the rear wall speaks of the reflected wave passing "right through" the cone. The cone he says is "virtually acoustically transparent". But I think a more correct description would be that the reflected wave (inside the box, off the rear wall) is exerting a force on the cone in opposition to the driven direction. In that way, the reflected wave might be said to in a way to travel "through" the cone.

-Pete
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Old 5th June 2013, 08:44 AM   #19
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How about this one (comes in 4 or 8 Ohm):

Europe Audio
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Old 5th June 2013, 09:40 AM   #20
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no way , the Sb acoustics is still to big.
At the very first start of the impulse the acoustic load would be like a very
little PS and very compressed , in terms of pressure . It won't allow high and
durable excursions IMO
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