Re: Modifying my 24 year old B&W P4
Posted: Mon Oct 25, 2021 4:35 pm
Back to familiar ground. Semi omni with mid bass up firing.
That has tamed the mid range a little and the presentation is not so in my face now I think I am so used to mid bass pointing up and doped that anything else is a bit of a shock and takes a bit of getting used to. So now I have semi omni again but no doping and a 1st order speaker level xover at 3.5kHz (ish).
There was still a bit too much mid range for my liking so I dropped the high pass capacitance to 10uf. that made a positive difference but it is still grating. I need to put them against the wall but it's hard when my cube speakers need moving and these TL's on their sides do not lend themselves very well to positioning.
This exercise has given me some courage to move away from doping but I don't think I will be doing it with a kevlar cone. The break up higher than xover is getting through and giving everything an edge that I don't like. You don't get this with a doped kevlar cone- it's liquid smooth but with some of the dynamics and detail taken away. Or maybe what I think is now detail is some frequency response problem. These 2" full range are still breaking in as well. At least with this lower xover they will get there faster.
I think these P4's will be passable once the xover frequency is decreased and done at line level passively. I might even have the courage to give these B&W kevlar 6.5" cones a spray of plastidip. It peels off because I removed some from Zebbo's old soft dome tweeters that he swapped out. The plastidip came off in one piece and looked like a dome.
I am aware of the need to match the directivity of the two speakers at xover, especially when both forward firing. This probably will be ok as the lowering of the xover frequency will make a better match between the 6.5" and 2" cones. I will have a 2" full range with 1st order high pass filter rather than what came with the speaker - a 25mm aluminum dome with ferro fluid and a third order ellectrical filter. In theory a 1st order xover is better for phase but there may be some other xover trickery going on in the original that I haven't got round to understanding yet. A first order low pass with a third order high pass. then there is any acoustical roll off to add in plus other things I don't know about.
Anyway, I am sure I can improve them even if they don't turn out perfect.
That has tamed the mid range a little and the presentation is not so in my face now I think I am so used to mid bass pointing up and doped that anything else is a bit of a shock and takes a bit of getting used to. So now I have semi omni again but no doping and a 1st order speaker level xover at 3.5kHz (ish).
There was still a bit too much mid range for my liking so I dropped the high pass capacitance to 10uf. that made a positive difference but it is still grating. I need to put them against the wall but it's hard when my cube speakers need moving and these TL's on their sides do not lend themselves very well to positioning.
This exercise has given me some courage to move away from doping but I don't think I will be doing it with a kevlar cone. The break up higher than xover is getting through and giving everything an edge that I don't like. You don't get this with a doped kevlar cone- it's liquid smooth but with some of the dynamics and detail taken away. Or maybe what I think is now detail is some frequency response problem. These 2" full range are still breaking in as well. At least with this lower xover they will get there faster.
I think these P4's will be passable once the xover frequency is decreased and done at line level passively. I might even have the courage to give these B&W kevlar 6.5" cones a spray of plastidip. It peels off because I removed some from Zebbo's old soft dome tweeters that he swapped out. The plastidip came off in one piece and looked like a dome.
I am aware of the need to match the directivity of the two speakers at xover, especially when both forward firing. This probably will be ok as the lowering of the xover frequency will make a better match between the 6.5" and 2" cones. I will have a 2" full range with 1st order high pass filter rather than what came with the speaker - a 25mm aluminum dome with ferro fluid and a third order ellectrical filter. In theory a 1st order xover is better for phase but there may be some other xover trickery going on in the original that I haven't got round to understanding yet. A first order low pass with a third order high pass. then there is any acoustical roll off to add in plus other things I don't know about.
Anyway, I am sure I can improve them even if they don't turn out perfect.