EV Cali Posted January 11, 2017 Share Posted January 11, 2017 (edited) I am presently refurbishing a pair of Kef 104/2 Speakers, new doughnuts / dust caps and complete rebuild of one of the bass speakers. During this process I have noted that one pair of the bass speakers face back in to a sealed cabinet. Top speakers in the picture. How can this be better than facing out in to the cabinet ,with sound exiting the port ,as the other pair do ? I also have a pair of 15'' PA Bass bins that are set up the same way. Edited January 11, 2017 by EV Cali Link to comment Share on other sites More sharing options...
luke352 Posted January 11, 2017 Share Posted January 11, 2017 When dealing with low frequencies the shape of the cone has no impact other than for stiffness etc.. So it doesn't matter if it faces in or out it is still moving air. The only impact you may see in that scenario is the slightly smaller radiating area on the back of the cone due to the voice coil former taking up some of the surface area. Does the lower driver go into a sealed chamber as well? Link to comment Share on other sites More sharing options...
EV Cali Posted January 11, 2017 Author Share Posted January 11, 2017 Thanks luke325 No the bottom pair of drivers face the other way and are close to the port ,as can be seen in the picture. If as you say it does not really matter what way they face I suppose the upper driver is also in the ported part of the cab. Just appeared odd to me that they do not both face the same way especially as you mention this would give a slightly smaller radiating area on the back of the cone due to the voice coil former taking up some of the surface area .Why not the other way round with a bigger radiating area. Link to comment Share on other sites More sharing options...
Sub Sonic Posted January 11, 2017 Share Posted January 11, 2017 It would be to help cancel out distortion. M&K subwoofers also use this principle, have a look on pages 8 and 9 in the link below. http://www.mksound.com/wp-content/uploads/2013/01/XSERIESWHITEPAPER.pdf Regards, SS 2 Link to comment Share on other sites More sharing options...
EV Cali Posted January 11, 2017 Author Share Posted January 11, 2017 (edited) Thanks Sub Sonic You certainly have the correct user name Edited January 11, 2017 by EV Cali 2 Link to comment Share on other sites More sharing options...
luke352 Posted January 11, 2017 Share Posted January 11, 2017 1 hour ago, Sub Sonic said: It would be to help cancel out distortion. M&K subwoofers also use this principle, have a look on pages 8 and 9 in the link below. http://www.mksound.com/wp-content/uploads/2013/01/XSERIESWHITEPAPER.pdf Regards, SS Definitely a possibility. A bit like an Isobaric setup, unusual having both firing into the ported chamber. But there are so many different styles of enclosure configurations. Link to comment Share on other sites More sharing options...
Sub Sonic Posted January 11, 2017 Share Posted January 11, 2017 Isobaric enclosures usually have the two woofers closely coupled (often face to face) so they act as one. The end result is that the enclosure volume can be halved compared to a single woofer, for the same response. The enclosure in the original post is a 4th order band pass, where one side of the woofer is in a sealed enclosure and the other is in a vented. This one is a slight variation where two woofers are used, but the principle is the same. SS 2 Link to comment Share on other sites More sharing options...
Atjan Posted January 14, 2017 Share Posted January 14, 2017 Also have a look at the polarity of the drivers when you rebuild. Make sure you replicate precisely. If you get that wrong you will probablybruin the LF response. 1 Link to comment Share on other sites More sharing options...
Atjan Posted January 14, 2017 Share Posted January 14, 2017 Also have a look at the polarity of the drivers when you rebuild. Make sure you replicate precisely. If you get that wrong you will probably ruin the LF response. Link to comment Share on other sites More sharing options...
legend Posted January 14, 2017 Share Posted January 14, 2017 A fundamental property of all waves (sound, light, water etc) is that they don’t ‘see’ objects that are much smaller than their wavelength but largely pass by them. Hence AM radio waves, whose wavelengths are of the order of 100 m, can be received in places where FM signal, whose wavelengths are of the order of 1 m, cannot. And there are limits that ultrasound waves, of the order of 1mm, can resolve. In the case of subwoofers, where the wavelength is around 3m at 100Hz and around 10m at 30Hz, the soundwaves effectively don’t ‘see’ the cabinet (dimensions around 0.3m) but largely pass around it. However, there will be a small time delay of around 1 ms putting the driver on the back compared to the front. At 100 Hz the phase change will be around 36 degrees but only around 10 degrees at 30 Hz, the latter probably not hearable. 2 Link to comment Share on other sites More sharing options...
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