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)
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.
-Joe
-Joe
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.
Mick
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.
Mick
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?
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.
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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