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How to calcuate if your driver can be in a downfiring orientation

Wharfedale Evo 4.2

aks07

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Aiyo George the 5% rule!!:p The Lambda Acoustics SB12 that you brought for me from US was a touch n go scenario and I spent many a nights poring on EXEL spreadsheets trying to find a compromise.

Another basics question a DIY would ask is whether a driver is suitable for sealed or ported box. A simple explanation from The Loudspeaker Design Cookbook by Vance Dickason:

Woofers intended for use in closed-box systems are characterised by low free-air resonance (fs), relatively high cone mass, and long voice coils.... In terms of driver Qts, closed-box loudspeakers generally require woofers with a fairly high Qts of greater than 0.3... R.Small suggested a good rule-of-thumb which he called Efficiency Bandwidth Product (EBP)

EBP is quantified by:

EBP = Resonance Frequency / Driver Electrical Q
or
EBP = fs / Qes

EBP in the vicinity of 50 or less indicates a sealed enclosure would be more suitable, while EBPs of about 100 suggest a vented enclosure.

As an example the Lambda Acoustics 12 driver is suitable for sealed box. Why?

From the SB12 T/S specs:

F s= 20.9 hz
Qes = 0.64

EBP = 20.9/064 = 32.2, which is below the thumb rule factor of 50

Thus the SB12 is suitable for a sealed box and indeed its makers suggest cabinet of 2.0~4.0 cubic feet sealed.
 

GeorgeO

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Ashok

Pity we didnt have the time in May to go and listen to your sub. In case I come to Jamshedpur in November, I am going to set aside a day to spend with you-spouse factor permitting!

George
 

doors666

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thanx for the info. sdx-15 shows 2.24% sag, so I guess I can safely mount it as downfiring:)
 
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