Quick Port Question

ReTrO · 4th April 2008, 09:58 PM

I have one port tuned to 20Hz of length 45cm and opening 2 x 30cm.

If I have 2 ports of the same opening and aiming for the same 20Hz tuning, should they both be 45cm long, or double @ 90cm?

Reason for asking is being confused by WinISD.

schmeet · 4th April 2008, 10:05 PM

I believe if you have two ports they should be twice the length of one port for the same tuning.

palesha · 5th April 2008, 02:25 AM

Quote:

I have one port tuned to 20Hz of length 45cm and opening 2 x 30cm.

R u sure?
For 20hz & port 45 cm x 30 cm, the box size will be 793.5 litres.
Is this ok?
Then if u want to put two ports of 45 cm length & 30 cm opening,
the length will be 111.945 cms. each, in one software or in other it is 115.53. Marginal difference. This calculation is based on above cabinate size. Or just give here .Qts, Fs, & Vas. for proper results.

ReTrO · 6th April 2008, 10:37 AM

The port size for a single is calculated in WinISD. The cabinet is 88L in volume.

Many thanks

richie00boy · 6th April 2008, 10:39 AM

I think he means a slot port of 2 cm by 30 cm.

If you double port area you need to double port length for the same tuning. So you will need two ports of 90 cm length.

ReTrO · 6th April 2008, 10:42 AM

Cheers, that was exactly what I meant.

ßart West-VL. · 6th April 2008, 11:21 AM

I just used WinISD and I get 101.7cm for two equal ports of 2cm x 30cm
Or one port of 100.9 - 4cm x 30cm which has the added advantage of having less friction surface and giving less noise I would think.

Be carefull with WinISD! Simulate, for example, with 20 ports and a realistic length (take 100cm in this case) you will see the ports will get very small, yet the 'vent mach' seems to be very good. It's not in real live!
That's why you should use one port only in WinISD.
I already mailed to them a long time ago, no response and no update.
(This is WinISD beta)

Bart.

AndrewT · 6th April 2008, 12:46 PM

I hope you are all using WINisd pro.

ßart West-VL. · 6th April 2008, 01:42 PM

Quote:

Originally posted by AndrewT
I hope you are all using WINisd pro.

That says enough for me, from now on I'll use the Pro Alfa version.

Bart.

palesha · 6th April 2008, 04:02 PM

Retro :

Quote:

The port size for a single is calculated in WinISD. The cabinet is 88L in volume.

As i told u, give me Fs, Qts, & Vas. I will design this in commercial software i hv.

4th April 2008, 09:58 PM	#1
ReTrO diyAudio Member Join Date: Dec 2003 Location: Hove, Sussex, UK	Quick Port Question I have one port tuned to 20Hz of length 45cm and opening 2 x 30cm. If I have 2 ports of the same opening and aiming for the same 20Hz tuning, should they both be 45cm long, or double @ 90cm? Reason for asking is being confused by WinISD. __________________ Richard Wilson

6th April 2008, 10:37 AM	#4
ReTrO diyAudio Member Join Date: Dec 2003 Location: Hove, Sussex, UK	The port size for a single is calculated in WinISD. The cabinet is 88L in volume. Many thanks __________________ Richard Wilson

6th April 2008, 10:39 AM	#5
richie00boy Did it Himself diyAudio Member Join Date: Nov 2003 Location: Gloucestershire, England, UK	I think he means a slot port of 2 cm by 30 cm. If you double port area you need to double port length for the same tuning. So you will need two ports of 90 cm length. __________________ www.readresearch.co.uk my website for UK diy audio people - designs, PCBs, kits and more

6th April 2008, 10:42 AM	#6
ReTrO diyAudio Member Join Date: Dec 2003 Location: Hove, Sussex, UK	Cheers, that was exactly what I meant. __________________ Richard Wilson

6th April 2008, 11:21 AM	#7
ßart West-VL. diyAudio Member Join Date: Jun 2005 Location: West Vlaanderen	I just used WinISD and I get 101.7cm for two equal ports of 2cm x 30cm Or one port of 100.9 - 4cm x 30cm which has the added advantage of having less friction surface and giving less noise I would think. Be carefull with WinISD! Simulate, for example, with 20 ports and a realistic length (take 100cm in this case) you will see the ports will get very small, yet the 'vent mach' seems to be very good. It's not in real live! That's why you should use one port only in WinISD. I already mailed to them a long time ago, no response and no update. (This is WinISD beta) Bart. __________________ Bart


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4th April 2008, 10:05 PM	#2
schmeet diyAudio Member Join Date: Mar 2008	I believe if you have two ports they should be twice the length of one port for the same tuning.

6th April 2008, 12:46 PM	#8
AndrewT diyAudio Member Join Date: Jul 2004 Location: Scottish Borders	I hope you are all using WINisd pro. __________________ regards Andrew T.

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