KEF modification

[Newfie]

I have a pair of Kef c-40s. i believe they're a 3way. they have dual 8s and a 1" tweeter in a sealed box. i enjoy the laid back smooth sound hooked up to a 1978 sony receiver.
but, are they ever lacking in bass. Am i able to add a port? I'm thinking of adding one of those adjustable ports.

 

[Newfie]

here are some specs i just found:

Infinite baffle [ closed box ] design
-:®:- Internal volume : 30lt
-:®:- Power rating : 10W - 100W
-:®:- Drivers : 1 x 25mm dome tweeter, 1 x 200mm polypropylene cone bass / midrange, 1 x 200mm bass drivers
-:®:- Sensitivity : 91dB / 1W / 1m
-:®:- Frequency response : 68Hz - 20kHz -6dB at 58Hz
-:®:- Impedance : nominal 8 ohms
-:®:- Dimensions [ W x D x H ]: 247 x 262 x 650mm
-:®:- Weight : 9.6kg each speaker

 

[frperdurabo]

The short answer is that woofers designed to work in a sealed box of a given size probably won't work in a ported box of the same size. Try placing the speakers closer to the back and side walls. Or investigate digital EQ solutions.

The long answer involves learning about T/S parameters and buying and using test equipment. This can be a lot of fun...

 

[jerome69]

Add a subwoofer ?

You can easily measure the T/S parameter with your computer and a sound with a line input. You need a cable jack-jack and a resistance less than10$. I wrote a tutorial here (you may need to translate).
The problem when you go to a BR box from a closed box, the volume of the box should be double.

 

[chris661]

I'd personally think that two 8" drivers per side should be plenty. That said, 30L for both seems a little small. Perhaps adding stuffing will help a little?

 

[BHTX]

Add a pair of adequate DIY subs, LR2 @ 60 Hz.

 

[Inductor]

-:®:- Sensitivity : 91dB / 1W / 1m
-:®:- Frequency response : 68Hz - 20kHz -6dB at 58Hz

Lower sensitivity from original project should have given a little better lower extension to a point, together with a bigger enclosure.

68Hz@-3dB
58Hz@-6dB
(Pic from: KEF C Series speakers on Seattle CL - any good? - AudioKarma.org Home Audio Stereo Discussion Forums)