Fuse for Peerless Tweeters

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motorcityguy
motorcityguy Posts: 69
in Vintage Speakers
Does anyone know why the specified fuse for Monitor 7's and 10's with Peerless tweeter is 1A, but for the first-gen Monitor 11 the spec is 0.75A?
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  • pitdogg2
    pitdogg2 Posts: 27,780
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    It is the same for all 1amp fast blow.
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  • motorcityguy
    motorcityguy Posts: 69
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    pitdogg2 wrote: »
    It is the same for all 1amp fast blow.

    But, according to Polk Monitor 11 owner's manual, "correct" fuse for THIS model is 0.75A, not 1A. In fact, Polk is rather adamant about it. (See screen shots from owner's manual.)

    I admit it is puzzling to me, since the Peerless tweeter is identical to Monitor 10 & 7, in which 1A fuse is specified.

    hvbnbo6t8ezh.jpg
    cnmzafbavw1z.jpg


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  • Gardenstater
    Gardenstater Posts: 4,890
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    Yeah I remember puzzling about that myself. The Peerless are the usual 8 ohm ones right? I mean they made 4 ohm ones as well.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • motorcityguy
    motorcityguy Posts: 69
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    Gardenstater wrote: »
    The Peerless are the usual 8 ohm ones right?

    Correct. They are (nominal) 8ohm Peerless.
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  • pitdogg2
    pitdogg2 Posts: 27,780
    edited August 27
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    Well, use the .75 amp fast blo. All the 7's or 10's have been 1 amp fast blo as well as my SDA 1 signatures.
    If you do a search here, you'll find most cases suggest 1 amp fast blo.

    https://forum.polkaudio.com/discussion/166860/fuses-on-vintage-speakers?utm_source=community-search&utm_medium=organic-search&utm_term=speaker+fuse
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  • motorcityguy
    motorcityguy Posts: 69
    edited August 27
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    pitdogg2 wrote: »
    Well, use the .75 amp fast blo. All the 7's or 10's have been 1 amp fast blo as well as my SDA 1 signatures.

    Yessir! That's the plan. But I was curious about the reasoning behind Polk's deviation from their usual 1A fuse. Not that everything Polk ever did makes sense.... But just thought there might be a technical reason that I was unaware of.
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  • pitdogg2
    pitdogg2 Posts: 27,780
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    It is kind of strange, it's not like they were different peerless tweeters. The SL1000 also used the 1 amp fast blo.
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  • Gardenstater
    Gardenstater Posts: 4,890
    edited 8:00AM
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    I'll take Mysterious Polk Anomalies for $200 Alex 🤣

    The circuit is definitely interesting. I wish I was better at analyzing crossovers. It looks like a pretty standard 2nd order high pass for the tweeter but unlike all the others I've seen from Polk, there is no series resistor for the Peerless whatsoever and it is usually a fairly high value. Could that be a clue as to why a lower amperage fuse, along with maybe the speaker not being super efficient (I need to try to find the dB rating)? Another weird thing about this hand sketched schematic is that it does not show the location of the fuse but the manual specifically says it is for the tweeter only:

    qnq5szrka6wa.png


    Post edited by Gardenstater at
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
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  • Gardenstater
    Gardenstater Posts: 4,890
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    Well according to this anyways, the RTA 11 was pretty darn efficient at 93dB. So that fuse probably has to be a low valued one because of the total lack of any series padding resistor for the Peerless Tweeter. It would probably have to be even lower if it wasn't for that sneak current through L4 and C2 to Driver #1 and Driver #2, which might be some sort of notch filter. The fuse would be located between that node in the schematic and C1.

    pcta2d88vrx2.jpg
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Onkyo A-8017 integrated
    Logitech Squeezebox Touch Streamer w/EDO applet
    iFi nano iDSD DAC
    iPurifier3
    iDefender w/ iPower PS
    Custom Steve Wilson 1m UPOCC Interconnect
    iFi Mercury 0.5m OFHC continuous cast copper USB cable
    Custom Ribbon Speaker Cables, 5ft long, 4N Copper, 14awg, ultra low inductance
    Custom Vibration Isolation Speaker Stands and Sub Platform
    · Share on Facebook