Sanity check please - port tuning for a Fane Colossus 18XB

[pk]

Hi,

I am just about to have a pair of vented bass cabinets build and would really appreciate a sanity check on the port tuning before I make sawdust

Driver: Fane Colossus 18XB

http://www.fane-acoustics.com/downloads/FANE_Colossus_18XB_Specs.pdf

The most important driver parameters are:

Fs = 33 Hz
Qt = 0.337
Vas = 236 liters

The intended use is hifi (not PA).

Frequency range: up to 200 Hz
Tuning frequency: 30 Hz (I know this is below the drivers Fs, but the since it is for hifi and not PA, it should be ok)

Box volume: 220 liters


Using 'WinISD online' I have come up with the following, single rectangular port:

Port area: 346.8 cm2
Port length: 37.1 cm


Now, can these numbers from WinISD be trusted?

What makes me a bit concerned is that Fane's own recommendation for a smaller cabinet (200 liters) with a higher tuning (35 Hz) does NOT correspond to the numbers calculted by WinISD (Fane-port length = 10.1 vs. WinISD port length = 31.1 cm)!?

http://www.fane-acoustics.com/downloads/Cabinets18inch200Lres.pdf


I would like to build the bigger (220 liters) box tuned to 30 Hz. Can I trust the port calculations provided by WinISD??

Thanks a lot!

Best regards
Peter

 

[Xoc1]

The Fane recomended box states a frequency response down to 35Hz
This is not to say that the box is tuned to 35Hz.
The Fane box will be tuned above 40Hz to get as much efficiency out of the cabinet as possible - it is not tuned for a flat response.
From my own experience.
Learn how to simulate a ported cabinet in Hornresp. This will get you closer to the correct port length and frequency response.
Use your WinISD frequency generator (Get frequency from cursor option)
connect the pc to an amplifier and connect the speaker to the amp via a DVM current meter - The tuned frequency of the port is where the speaker draws the maximum current. I found this very easy to do and confirmed the port tuning was fairly close to the calculated figure. There are so many variables that effect the tuning that only real testing will confirm that everything is OK
Regards
Xoc1

 

[bjorno]

..Driver: Fane Colossus 18XB

http://www.fane-acoustics.com/downloads/FANE_Colossus_18XB_Specs.pdf

The most important driver parameters are:

Fs = 33 Hz
Qt = 0.337
Vas = 236 liters

The intended use is hifi (not PA).

Frequency range: up to 200 Hz
Tuning frequency: 30 Hz (I know this is below the drivers Fs, but the since it is for hifi and not PA, it should be ok)

Box volume: 220 liters...

Hi Peter,

Take a look at this:

b

 

[pk]

Hi Xoc1 and Bjorno,

Thanks a lot for your elaborated replies!

Xoc1: Thanks for indicating that the suggested design by Fane is not tuned to 35 Hz at all. I am sure you are right about that!

I have tried to model my own suggestion using HornResp, and it looks ok as far as I am concerned! However, one problem is the spike just below 300 Hz due to a rather deep cabinet.

Q: Do you think I will be able to hear this spike when using a 24dB/octave crosover at 200 Hz?

Bjorno: Thanks for the detailed calculations - I am impressed! Since my mid/high combo only reaches just below 200 Hz, I will have to go for a vented solution though.

Best regards
Peter

 

[bjorno]

..Q: Do you think I will be able to hear this spike when using a 24dB/octave crosover at 200 Hz?..Peter

Answer: No. Picture hints:

b

 

[pk]

Hi Bjorno,

Thanks a lot for the reply!

Best regards
Peter

Answer: No. Picture hints:

b