Converting from one round port to several round ports

[NighthawkGS]

Hi folks, hopefully quick question regarding converting from one large round port to several smaller ones:

I have an old small cab, an ex SWR combo, which has one dumb little 2 in zero length round port. I would like to conform it to a published eminence cab spec (see below).

MY QUESTION:

The spec calls for a single 4 inch diameter 4.5 inch length round port. Could I substitute 2 smaller ports with the appropriate diameter and same length to achieve identical volume, and attain the same tuning? (And/or could I also change the length somewhat to get the numbers exact with an even sized diameter?)

Thx!


Legend CA10-8 Small Vented Bass Guitar Cab
By Jerry McNutt, Eminence Speaker LLC
Limit to 80 Watts; F3 at 70 Hz.
Not for Full Range Use; best used on top of a 15".
Box Properties
--Description--
Name:
Type: Vented Box
Shape: Prism, square
--Box Parameters--
Vb = 0.85 cu.ft
V(total) = 0.965 cu.ft
Fb = 70 Hz
QL = 7
F3 = 70.29 Hz
Fill = minimal
--Vents--
No. of Vents = 1
Vent shape = round
Vent ends = one flush
Dv = 4 in
Lv = 4.457 in

 

[Redbrangus]

You can substitute 2 ports of the same length as long as the cross-sectional area stays the same. Someone should check my arithmetic, but I think that's gonna work out to be 2.8+ inches for the new port diameter. Then the question becomes what the port velocity would be...would it be audible?

 

[agedhorse]

Is the cabinet's internal volume the same as in Eminence's specs?

 

[NighthawkGS]

Is the cabinet's internal volume the same as in Eminence's specs?

Internal volume is close, something like 94% of what they specify. On their website, they say that being within 10% won't make much of a difference.... Certainly wouldn't mind compensating the port dimensions if that was practical....