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Philips MFB speakers

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Fatmangolf View Drop Down
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 16 Aug 2021 at 7:29pm
I have decided to go through replacing the electrolytics inside my RH544 speakers. It may improve the sound slightly and will give me decades of listening pleasure.


Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 17 Aug 2021 at 8:14pm
More decades of listening pleasure. I'll look at some of the other capacitors at the same time.

Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 18 Aug 2021 at 8:45pm
The parts are here thanks to MFBfreaks. There's going to be some soldering this weekend!
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 21 Aug 2021 at 10:06am
I replaced 30 electrolytics in each speaker with standard modern equivalents, nothing exotic. It took me about four hours plus resetting the four amps' bias levels and MFB gain. Well worth the cost and time for the extra clarity and separation between different instruments. The main supply capacitor is a larger value (6800uF in place of 4700uF), otherwise it is the same or close values throughout. So I am hearing the electronics as if factory fresh in the mid-seventies and I like the music I am hearing even more than last week.

It is raining outside so a lazy day of listening to music is tempting me! No I will get some exercise...  Maybe I could play another album first...


Edited by Fatmangolf - 21 Aug 2021 at 10:13am
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 30 Nov 2021 at 9:31pm
Three months later and I am still enjoying my RH544's. They are still on the Partington stands but with Isopucks which have tightened the bass, or rather stopped the floorboards joining in!

Trivially I also fitted a C14 socket on the older speaker that had an original 2 pin socket. I had converted the other speaker years ago when I lost the 2 pin mains lead in a house move

I listen at moderate levels so I am going to lower the LF extension by changing the rumble filter frequency. It has been written about on the MFB Freaks site so why not give it a try?
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2021 at 6:40pm
The LF extender is just lowering the rumble filter's corner frequency by changing C514 and C515, part of the Salen and Key HPF built around transistor 424. I used 1 / 2 Pi x Fc x R, where R is the square root of R625 and R633. One is half the other's value for Q=0.7071 so it was 31 Hertz. I added a 68nF ppr capacitor in parallel with the original caps to get about 225nF and 21 Hertz corner frequency.

I checked the gain needed and amp power was sufficient. The Qtc is about 0.8 as the box ratio alpha is about 3, so response falls at about 11dB/octave. Fc is 77 Hz so 2 octaves down is 19 Hz. At 21Hz this would need over 10 Watts to match 1 Watt at 100 Hz.

It sounded fine and I tried some tracks with sub-bass. Then a 20 - 120 Hz sweep, no distortion but door and furniture rattled.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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Post Options Post Options   Thanks (0) Thanks(0)   Quote Fatmangolf Quote  Post ReplyReply Direct Link To This Post Posted: 04 Dec 2021 at 9:19pm
I am aware there's not much down there on most recordings.
Jon

Open mind and ears whilst owning GSP Genera, Accession M, Accession MC, Elevator EXP, Solo ULDE, Proprius amps, Cusat50 cables, Lautus digital cable, Spatia cables and links, and a Majestic DAC.
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