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Philips MFB speakers |
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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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!
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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One of the cheapest modifications I made to these speakers but highly recommended.
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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.
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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.
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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. |
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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 |
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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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Fatmangolf
Moderator Group Joined: 23 Dec 2009 Location: Middlesbrough Status: Offline Points: 8960 |
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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.
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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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