B&C Sub 18 plan internal volume |
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Foca_Dacian
Registered User Joined: 05 February 2011 Location: Romania,Cluj Status: Offline Points: 118 |
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Posted: 27 July 2017 at 9:59am |
I have done some calculations and the results ar not as stated in the plan.
Internal volume of the box 47 x 70 x 61=200,69 Liters total internal volum. Port volume is 30,2 x 47 x 13,8=19,58 Liters 200,69 - 19.58 -7 liters(volume of the 18 inch driver I use)-2l bracing and we end up with 172 liters , not 183 liters as the design stated. Am I correct? Also, what would be the tuning , if the internal volume is not as stated in the design?
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djeddie
Old Croc Joined: 26 April 2004 Location: Bristol Status: Offline Points: 4125 |
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The enclosure shown in the plan has no driver and no bracing, hence the 183l. (Actually about 181l).
If you are that worried simply make the enclosure slightly bigger. I doubt it would make much difference as the T/S parameters of the driver your planning on using are probably not exactly as stated on the spec sheet. Some of those parameters can vary by as much as ±20%!!! Which driver are you planning on using? Edited by djeddie - 27 July 2017 at 7:05pm |
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Chas n Dave : it's like Drum and Bass but with beards. E=mc² ±3dB
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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At this volume, 11l of air will propably move the box tuning in between 0,6-0,8Hz. That´s nothing...
Don´t get caught into details like that too much, unless you´re developing something on purpose. |
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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Foca_Dacian
Registered User Joined: 05 February 2011 Location: Romania,Cluj Status: Offline Points: 118 |
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I will be using Faital Pro 18HP1010-4 ohm version:
I want to build 4 B&C Sub18's. Simulations are similar to B&C 18TBX100,except F3 @ 37 Hz with 18TBX100 and F3@ 43 Hz with the Faital. If I tune to 40 hz ,then I get F3 @39 Hz with the Faital. How do I simm the ports from the B&C Sub18? The software tells me the port needs to be 532 mm deep for 35 hz tuning, I am probabilly doing something wrong,I have simmed two ports with the area of 27000 sqmm. Actually what I am interested is , how short do I need to make the ports for 40 hz tuning? That was why I was calculating volume really precise, beacouse something does not add up. I would appreciate some help with this. |
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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You cannot sim triangular ports really. You propably need to develop your box and measure the outcome. Good thing about ports is, that you can make it shorter at first, and then add lenght to it, until you´re where you want to be. So your development box can become your final box...
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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Foca_Dacian
Registered User Joined: 05 February 2011 Location: Romania,Cluj Status: Offline Points: 118 |
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The ports are rectangular on this plan,this is the b&c sub18 plan:
Edited by Foca_Dacian - 28 July 2017 at 12:07pm |
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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Oh, these... I had different construction in mind. You still cannot simulate it very well in most simulators, because these don´t count with friction and "port enlongation" as few walls all of it continue in its way as part of the enclosure. So my post holds in a same way, no matter what shape it is....
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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Foca_Dacian
Registered User Joined: 05 February 2011 Location: Romania,Cluj Status: Offline Points: 118 |
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What can I use to measure the impedance plot and see where the tuning is?
I'll start by making the port 30 mm shorter than in the plan and go from there.
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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It´s quite easy. Download Arta software (Limp is inside, and you need that one).
Make hardware setup seen in the help, section 3 - Measurement setup, first image. You need just some wire, 50-120 Ohm resistor, and two jacks for your soundcard. Then you make your software setup - pick audio devices and write in the resistance used, and which channel is which. If you´re lucky, you´re done in 15 minutes. Then you can measure (Play button). Lowest impedance between two peaks of the bassreflex enclosure shows you the tuning. Phase at 0° at this tuning might be more exact than impedance. You can compare... |
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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mini-mad
Old Croc Joined: 13 July 2012 Location: london Status: Offline Points: 6903 |
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...sound simple enough... can I do this with a driver in free air to find it's us parameters? |
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If it sounds like a gorilla is trying to escape, turn it down.
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Crashpc
Registered User Joined: 26 February 2008 Location: Czech Republic Status: Offline Points: 465 |
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Yes. With added mass method, you can measure TS parameters too.
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Nikon and Canon people should not be married to each other. Why did you let this happen?
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