Is it possible to design a multi-port cabinet (simulating 3 or 4 equal ports by adjusting the diameter) where the length of the ports is made equal to the width of the front panel of the speaker cabinet? I.e. made a tubeless bass reflex cabinet? pro and cons?
It has been done many times. The disadvantage is the port is smaller. Adding a tube allows you to keep the tuning while making it wider.
Pros are simpler construction, cons are the smaller ports for the same Fb (frequency of box tuning) in a given box volume are easily "blown out" at relatively low power.
A slug of air only 12-18mm deep in a port does not have far to travel before it becomes wind, rather than a low frequency sound wave.
....and the length of this opening aka. port length.
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However, I would plan for an opening that is several times larger.
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Not tubeless. A vent with the length equal to thebaffle thickness. Many nolder seigns are such as are all the Pensils.
dave
Sorry, in my post above I was probably still thinking too much about a post in another thread where someone suggested something like this for a given driver/enclosure size combination, which I think would work very badly in this case.
In principle, however, this can work if the Vb required for a balanced tuning is very large in relation to the driver size and fb not too low, so that the cross-sectional area of the port does not have to be too small with such a short length.
But if you declare a port with a length equal to the thickness of the front baffle to be a target in itself, you deprive yourself of a degree of freedom in the development of a loudspeaker, and in my opinion without any recognisable advantage.
In principle, however, this can work if the Vb required for a balanced tuning is very large in relation to the driver size and fb not too low, so that the cross-sectional area of the port does not have to be too small with such a short length.
But if you declare a port with a length equal to the thickness of the front baffle to be a target in itself, you deprive yourself of a degree of freedom in the development of a loudspeaker, and in my opinion without any recognisable advantage.
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Speaking of tubeless designs... Anyone tried replicating TAD's port found in E1TX ? How does one go about calculating this type ?
Exactly what I was thinking ) Considering there are actually two flares and only one throat, should I assume the throat area/diameter for each flare is the actual value /2 ? 🤔
Although port tubes are typically cylindrical, any hollow shape can serve the same purpose.
TAD's slot port tubes can be calculated the same way as any high aspect ratio bass reflex port tubes.
When a side, or sides of an enclosure are used as a port wall in square, rectangular or triangular ports, the port length is effectively made longer by the additional mass of air adjacent to the walls.
The port's end correction factor "K" used in calculating Fb (box tuning frequency) would increase from .732 for a standard round port of the same depth and cross sectional area to over 2 for the thin port.
TAD's "Aero-Dynamic' slot exit has a bit more area than the interior to reduce port noise somewhat.
The CE1TX Fb is ~39Hz as can be seen by the impedance dip at that frequency.
The thin port exits reduce potential rodent occupation of the cabinet...
Art