Vifa M13IC midrange chamber

murat · 27th October 2007, 01:47 AM

Hi. I was gonna use Vifa M13IC 1.8 liter chamber with Vifa P13WH00 midrange but the chamber is not available anymore. It doesn’t seem to be a big deal to built one with strong PVC tubing or similar.

1) Does anyone know the dimensions? I have only seen the picture. Is it made of metal or plastic?

2) Do the shape and dimensions actually matter or is it just enough to get 1.8 liter inner volume with an arbitrary shape? It will be filled with fiberglass.

Thanks!

andrew01 · 27th October 2007, 09:56 AM

Plastic.

I have an old datsheet from 1990 , which shows the following :

Part # 727024

Vol=1.8L
Length = 222mm
Diameter = 118.5mm
Radius total = 68.7mm
Radius inner = 63mm
Radius hole centers = 66mm (4 holes )

murat · 27th October 2007, 05:34 PM

Thanks a lot Andrew. I calculate the volume 1.83 liter from these values assuming one end hemispherical

murat · 17th November 2007, 05:03 PM

Ooops. Wrong calculation... I generate the following figure from the numbers (I have added 6.6 cm which is mounting hole location of of the driver)

Now volume is 2.19 liter. More than 20 % error. Am I missing something?? Andrew, do you mind checking the numbers for a typo? Thanks...

5th element · 17th November 2007, 05:33 PM

Remember the drivers structure will take up some of the volume too. Perhaps the 1.8l vifa are referring to, is the volume left after the driver is mounted?

jnb · 17th November 2007, 08:10 PM

I recall a study that found this enclosure to be a poor performer. IIRC it produced a group of resonances, and one in particular that was hard to damp. I think the flat ended tube was found to be only slightly better.

murat · 17th November 2007, 08:54 PM

Thanks guys.

What if I use a shorter cylinder with a bigger radius? Even a rectangular box with ~ 2 liter inner volume after 5th element's suggestion. Would I expect a better or worse resonance structure? To remind, the box will be filled with fiberglass.

jnb · 17th November 2007, 10:41 PM

IIRC a normal box and, surprisingly, a cube when around this size both performed well. That is to say that there was close to +/-1dB of difference between no box, and box with damping (except for bass performance, of course). I think that all cylinders and other round shapes in this test were not as forgiving.

Note that I'm only accounting the internal effect of the enclosures.

murat · 20th November 2007, 12:04 AM

Here is the reply I got from Prof Leach:

"The volume is not critical at all. Just be sure you put fiberglass into the chamber. That includes around the magnet."

27th October 2007, 01:47 AM	#1
murat diyAudio Member Join Date: Nov 2004 Location: knoxville tn	Vifa M13IC midrange chamber Hi. I was gonna use Vifa M13IC 1.8 liter chamber with Vifa P13WH00 midrange but the chamber is not available anymore. It doesn’t seem to be a big deal to built one with strong PVC tubing or similar. 1) Does anyone know the dimensions? I have only seen the picture. Is it made of metal or plastic? 2) Do the shape and dimensions actually matter or is it just enough to get 1.8 liter inner volume with an arbitrary shape? It will be filled with fiberglass. Thanks!

17th November 2007, 05:33 PM	#5
5th element diyAudio Member Join Date: Oct 2002 Location: England	Remember the drivers structure will take up some of the volume too. Perhaps the 1.8l vifa are referring to, is the volume left after the driver is mounted? __________________ What the hell are you screamin' for? Every five minutes there's a bomb or somethin'! I'm leavin! bzzzz! Droggon Attack!

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27th October 2007, 09:56 AM	#2
andrew01 diyAudio Member Join Date: May 2003 Location: Adelaide Southern Suburbs	Plastic. I have an old datsheet from 1990 , which shows the following : Part # 727024 Vol=1.8L Length = 222mm Diameter = 118.5mm Radius total = 68.7mm Radius inner = 63mm Radius hole centers = 66mm (4 holes )

27th October 2007, 05:34 PM	#3
murat diyAudio Member Join Date: Nov 2004 Location: knoxville tn	Thanks a lot Andrew. I calculate the volume 1.83 liter from these values assuming one end hemispherical

17th November 2007, 08:10 PM	#6
jnb diyAudio Member Join Date: Dec 2006	I recall a study that found this enclosure to be a poor performer. IIRC it produced a group of resonances, and one in particular that was hard to damp. I think the flat ended tube was found to be only slightly better.

17th November 2007, 08:54 PM	#7
murat diyAudio Member Join Date: Nov 2004 Location: knoxville tn	Thanks guys. What if I use a shorter cylinder with a bigger radius? Even a rectangular box with ~ 2 liter inner volume after 5th element's suggestion. Would I expect a better or worse resonance structure? To remind, the box will be filled with fiberglass.

17th November 2007, 10:41 PM	#8
jnb diyAudio Member Join Date: Dec 2006	IIRC a normal box and, surprisingly, a cube when around this size both performed well. That is to say that there was close to +/-1dB of difference between no box, and box with damping (except for bass performance, of course). I think that all cylinders and other round shapes in this test were not as forgiving. Note that I'm only accounting the internal effect of the enclosures.

20th November 2007, 12:04 AM	#9
murat diyAudio Member Join Date: Nov 2004 Location: knoxville tn	Here is the reply I got from Prof Leach: "The volume is not critical at all. Just be sure you put fiberglass into the chamber. That includes around the magnet."

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