help with port size for Peerless XLS 10-inch

[atilsley]

Can someone please recommend the optimum port size (single or dual) for the 10-inch XLS driver?

http://www.vikash.info/audio/xls10/

The cabinet is a triangual shape, using 25mm side walls. Approx measurements are 52cm x 38cm x 25cm = 49,400 cm volume.

Amplifier is 150-watt D-class.

I will have two of these units for a stereo hook up, combined with Lowther horns.

Goal is musicality, not Home Theatre.

Also, how important is to flare the ports, either at one end or both ends?

Thanks.

[GM]

'Optimum' is dependent on a number of variables, but considering they are filling in below some horns I prefer a low tuning (Fb), but due to this driver's specs the vent will be fairly large, long and why a passive radiator (PR) is normally used. A smaller, shorter vent can be used if damped with stuffing though, like a TL. For this you'll need at least a 6.3 cm diameter pipe 40-50 cm long and shortening it along with experimenting with stuffing density is how to tune it in-room. Once done, tuning will be around Fs. Of course if this is too low for your tastes you can just keep shortening it until it allows you to play the lowest frequency music you have. IOW if you plan to never play pipe organ symphonies or other music with content below 27 - 30 Hz, then the vent will be much shorter, in the 10-20 cm range. Again, these will need some stuffing also to keep vent noise inaudible when the sub is driven hard down around Fb.

Flaring definitely helps reduce vent noise, though with long vents it's usually not enough, so since stuffing is required, flaring is a waste of time/$$$ IMO as it's easier, cheaper to just add a bit more stuffing.

GM

[atilsley]

GM, thanks.

Given there might be some restriction on a longer pipe, why not a larger pipe, eg 10cm ? Alternatively, x2 pipes at 15-20cm each in length?

Regards

[infinia]

These peerless subs are mostly using the passive radiators, because of vent length and port chuffing issues for standard alignments. You can DL the "Unibox" spreadsheet and play with different alignments. The program will show port air speed and excursion charts for alignments of your choice.
Below is taken from the App notes from Tymphany.

Vented cabinet data:

Total volume: 26 litre
Port diameter: 70 mm
Port length: 930 mm

Tuning frequency: 25 Hz



Conclusion for the vented system:
The port is long and large. This means that the port takes up some space in the cabinet, in this case using a 3 mm thick tube material will take up as much as 4.2 liters of box volume. Also including the approx. 2 litre that the drive unit occupies results in an internal box volume of 26 litre.
Because the port is almost one meter long the port needs to be folded inside the cabinet or build up using a labyrinth approach.
Given the design target from above it has been shown that it is possible to achieve the desired result, but the port need to be part of the cabinet design or folded to achieve the low tuning needed.

It has been shown that a high pass filter for the system is highly recommended to reduce the excursion below tuning.




from http://www.tymphany.com/xls-subwoofer

[GM]

You're welcome!

Well, bigger or multiple pipes requires a longer length due to increased friction losses and since you already need to restrict the pipe with stuffing, why make it bigger only to require more stuffing?

GM

[Thawach]

i see the vented box graph from Tymphany website. it begin to roll off at about 150 hz. and see the low qts parameter that's sure thin bass. you may use parametric EQ to adjust the respond graph. but i think it's only goog for passive radiator.


/TW