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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: 14 Dec 2021 at 1:40pm
The heavy cloth on the original speaker dust covers muffled the sound but the speakers look better to me when covered so I have stripped and recovered them with a modern speaker cloth. It is acoustically transparent so I get a nicer look and the clearest sound. An hour well spent on the work involved!

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: 15 Dec 2021 at 9:02pm
One of the cheapest modifications I made to these speakers but highly recommended.

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 Mar 2022 at 8:18pm
I'm enjoying these seventies speakers every day and wonder why I stopped using them. Admittedly having a service manual and better test gear has helped me get the most out of them. I am considering a trial with a different dome midrange driver next.
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: 20 Mar 2022 at 2:09pm
I must admit that I'm enjoying 47 year old AD0210 squawkers in my Philips speakers a lot so unsure what I'd need to buy to improve on them.
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 Apr 2022 at 2:28pm
I had switched back to my Gold GX300 speakers driven by the excellent Proprius amplifiers. Partly because I rotate my hoard of hifi and partly to compare to the Philips RH544's. I noticed that percussion was more natural so this made me wonder why? I set myself the challenge of adapting the 544 sound to have the 'air'nor 'sparkle' of the GX300's even if it wasn't a permanent change.

Reading service manuals helps. I found Philips had changed the negative feedback circuit to cut back the treble when they changed the tweeters, fitting a larger 5n6 capacitor to rolloff the treble when they put a new tweeter in. Having testing the FR and THD on the AD0140's in my 544's I understood why they wanted to dial them back. But I had put  modern fabric dome tweeters in that were well matched and quite smooth so I thought an experiment was in order with C561.

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 Apr 2022 at 2:46pm
I used some polypropylene capacitors. Listening to music and measuring with REW and a calibrated microphone.

There is a HF cut control in the input stage of my 544's which operates from 7kHz so I knew I could reduce the treble later if I needed to. I tried 1nF, 4n7, and 2n2 PPL plus the original 5n6 ceramic. I went with 2n2 PPL as a good compromise on the FR and I liked the sound best. Another cheap modification I am enjoying.

You can have too much of a good thing which is why I went for 2n2 not less. Some guitar amps have a presence control that decreases the NFB signal with a capacitor in series with the pot so it is the treble that is boosted. It will be slightly  louder. The sound gets richer or less clean, turn it up and turn your guitar down slightly.

The fine MFB Freaks website has people going down to 680nF so I may yet try 1nF. See what I have in my spares box!


Edited by Fatmangolf - 17 Apr 2022 at 5:22pm
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 Apr 2022 at 5:38pm
I also took out the sub-bass extender (parallel caps I added to the active rumble filter) as I couldn't hear or measure a difference to the response. Before removing the caps I could see higher distortion under 40Hz so it was sucking up power from the amp.

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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