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Multi-Way Conventional loudspeakers with crossovers

infinite box volume
infinite box volume
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Old 25th March 2003, 06:39 PM   #1
joz is offline joz
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Join Date: Nov 2002
Location: athens greece
Default infinite box volume

Whats happening if we use an almost infinite volume box for a bass driver,especially a subwoofer ( using the volume of a room, and the baffle is the wall of the room)
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Old 25th March 2003, 08:51 PM   #2
redrumjoe666 is offline redrumjoe666
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Depending on the compliance of the driver and the volume of the room, you would get various modes and degrees of distortion, since the size of the room affects which wavelengths are going to cancel and which are going to be multiplied. The volume of the room acts as a spring force and has to be in line with the speaker's compliance, otherwise it will probably overdrive, adding distortion.

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Old 25th March 2003, 09:49 PM   #3
Kanga is offline Kanga  Australia
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As the box size approaches infinity, the Qtc (total damping) will approach the Qts of the driver. In the case of a room being the box, the Qtc will be very close to the Qts of the driver. For drivers which have a Qts of 0.3 to 0.5 this will mean that the system is underdamped. You would need to use a driver with a Qts of 0.5 or more. A lot of car drivers have a high Qtc.

As joe says, you would also tend to have standing wave problems using a room as an enclosure rather than a box, which will generally have dimensions that are too small for standing waves to form with a sub. How much of a problem this will be I'm not sure.

One further point is that the wall would need to be well reinforced (eg brick) or else you will have all sorts of colouration added by the wall vibrating along like a cheap plastic speaker box.

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Old 25th March 2003, 09:51 PM   #4
toenail is offline toenail  United States
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If the exterior wall of the room were to play the role of baffle wouldn't the back of the driver have to be sandwiched between two studs and another layer of sheetrock, therefore creating a tall, narrow, shallow box?
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Old 26th March 2003, 01:44 AM   #5
ThomasW is offline ThomasW
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Use of a wall cavity isn't a good idea, first it's to shallow. Second it would be quite difficult to get an airtight seal. And if it's sealed the materials are inherently resonant

FWIW, there will be no more room modes with a true IB sub that there will be with any standard 'box' sub.

For true IB operation the space needs to be 4-10 times the Vas of each driver/drivers used.

The use of RDO (Resistively Damped Operation) with DVC drivers allows the user to tailor the "Q" to personal taste.
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Old 26th March 2003, 12:55 PM   #6
joz is offline joz
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Location: athens greece
When i say the baffle would be a wall that separates two big rooms,certainly the wall will be very well constructed.I like to hear
whats happening with the drivers behavior(subwoofer) if works with an infinite volume( of the room that works as a huge closure).
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