Quick newbie question port calculation

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Hi all,

Just finishing my reflex bins. I've been using WinISD pro but stumble upon one question. Does WinISD subtract the volume displaced by ports from vb as it calculates them (as BBpro does)? I don't imagine it does because it doesn't request the panel thickness. Until I calculate Lv, can't subtract vol from vb - but need vb to calculate lv

Can you help me tune my cab? (Lv)

Vb is 201 litre (taking volume displaced by driver and all internals except ports (not yet known)
Ports are 3x 120mm ports with one flared end
Baffle is 36mm
desired fb is 40.7hz

Thanks in advance for any guidance

Ben

Edited by Ben W - 28 August 2011 at 3:19pm

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Ben W Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 27 December 2010 Status: Offline Points: 43	Post Options Post Reply Quote Ben W Report Post Thanks(0) Quote Reply Topic: Quick newbie question port calculation Posted: 28 August 2011 at 2:52pm
	Hi all, Just finishing my reflex bins. I've been using WinISD pro but stumble upon one question. Does WinISD subtract the volume displaced by ports from vb as it calculates them (as BBpro does)? I don't imagine it does because it doesn't request the panel thickness. Until I calculate Lv, can't subtract vol from vb - but need vb to calculate lv Can you help me tune my cab? (Lv) Vb is 201 litre (taking volume displaced by driver and all internals except ports (not yet known) Ports are 3x 120mm ports with one flared end Baffle is 36mm desired fb is 40.7hz Thanks in advance for any guidance Ben Edited by Ben W - 28 August 2011 at 3:19pm

Meat Members Profile Send Private Message Find Members Posts Add to Buddy List Old Croc Joined: 05 June 2009 Location: Manc Status: Offline Points: 1514	Post Options Post Reply Quote Meat Report Post Thanks(0) Quote Reply Posted: 28 August 2011 at 4:20pm
	You won't get exact porting lengths from winISD or most other programs. Its a pretty crude guess that maybe gets within 5Hz most of the time. If you want accurate tuning you need to measure the minimum impedance of the speaker find out where its tuned, modify the cab then measure, repeat until you're happy.
	Don't test the champignon sound

Ben W Members Profile Send Private Message Find Members Posts Add to Buddy List Registered User Joined: 27 December 2010 Status: Offline Points: 43	Post Options Post Reply Quote Ben W Report Post Thanks(0) Quote Reply Posted: 28 August 2011 at 4:41pm
	Ok. Thanks. I did assume it was an estimate. Could you provide any information re: how to tune by impedence? For now I'll go with WinISD tuning. Thanks B.