celestion Ditton 15XR - Passive Radiator question

REXTON · 17th April 2011, 09:46 PM

Hi,

I'm in the middle of upgrading my 15's. I'm replacing the foam in the speaker but was wondering what would happen if I put too much foam in the passive radiator chamber of the cabinet. Should I just leave the area devoid of foam or completely fill the area??

Thanks in advance.

18Hurts · 17th April 2011, 10:27 PM

Foam?

You mean speaker stuffing like the inside of a pillow? I used the matting sound material with my passive but kept it away from the cone. Passive radiators have quite a long stroke and will compress the stuffing in short order, maybe too much. Since the cone is moving so fast, I'm afraid the stuffing will wear on the cone and could throw it off balance which will put torque on the suspension. You do have the option to zip tie some netting around the frame of the passive, it will keep any loose speaker stuffing from hitting the disc or cone.

Jonathan Bright · 18th April 2011, 07:22 AM

If you mean putting more fibrous material inside the speaker cavity in addition to what Celestion originally placed there you will alter the bass characteristics a bit.

It will depend on how dense you pack it etc but the difference between empty and "fully packed" increases the apparent volume by the square root of two i.e. about 1.4. This is the result that Gilbert Briggs obtained experimentally and was the same as the theoretical calculations (James Moir, I think). Now that may not of course be a bad thing. May sound better. But both theory and practice suggest it will have an effect. Try it I guess.

Cheers, Jonathan

REXTON · 18th April 2011, 04:12 PM

Thanks guys. I just intended to try and dampen the cabinet down internally as much as I could. So I'll have to experiment and see what happens!

17th April 2011, 09:46 PM	#1
REXTON diyAudio Member Join Date: Sep 2009	celestion Ditton 15XR - Passive Radiator question Hi, I'm in the middle of upgrading my 15's. I'm replacing the foam in the speaker but was wondering what would happen if I put too much foam in the passive radiator chamber of the cabinet. Should I just leave the area devoid of foam or completely fill the area?? Thanks in advance.

18th April 2011, 07:22 AM	#3
Jonathan Bright diyAudio Member Join Date: Feb 2004 Location: Queensland	If you mean putting more fibrous material inside the speaker cavity in addition to what Celestion originally placed there you will alter the bass characteristics a bit. It will depend on how dense you pack it etc but the difference between empty and "fully packed" increases the apparent volume by the square root of two i.e. about 1.4. This is the result that Gilbert Briggs obtained experimentally and was the same as the theoretical calculations (James Moir, I think). Now that may not of course be a bad thing. May sound better. But both theory and practice suggest it will have an effect. Try it I guess. Cheers, Jonathan __________________ "It was the Spring time of the year when aunt calls to aunt like mastodons across the frozen waste." P.G. Wodehouse.

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17th April 2011, 10:27 PM	#2
18Hurts diyAudio Member Join Date: Nov 2010	Foam? You mean speaker stuffing like the inside of a pillow? I used the matting sound material with my passive but kept it away from the cone. Passive radiators have quite a long stroke and will compress the stuffing in short order, maybe too much. Since the cone is moving so fast, I'm afraid the stuffing will wear on the cone and could throw it off balance which will put torque on the suspension. You do have the option to zip tie some netting around the frame of the passive, it will keep any loose speaker stuffing from hitting the disc or cone.

18th April 2011, 04:12 PM	#4
REXTON diyAudio Member Join Date: Sep 2009	Thanks guys. I just intended to try and dampen the cabinet down internally as much as I could. So I'll have to experiment and see what happens!

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