Replacement Grills for Polk Series 7B's

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MDN
MDN Posts: 16
in Vintage Speakers
I'm looking at a pair of Polk 7's that don't have the grills. Is there a source to buy the grills or an alternative solution? Thanks in advance.
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  • F1nut
    F1nut Posts: 49,787
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    MDN wrote: »
    I'm looking at a pair of Polk 7's that don't have the grills. Is there a source to buy the grills or an alternative solution? Thanks in advance.

    The none BS answer to your question is there is no source for replacement grills.
    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023 Answer ✓
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    These are probably from a Monitor 7. I question the seller's measurements of 23-3/8" x 13-3/8" (prob. should be 14"), but lots of eBay sellers are measurements challenged. Also, the seller "can't remember" what speaker model they got them from. The speaker peg hole positions are different from my 7Bs, but they even have the partial depth mystery forstner bit hole that mine have. These probably came from a later 7B than mine if the 23-3/8" is correct, but then the badge should be on the speaker and not the grill so still doesn't compute:

    https://www.ebay.com/itm/354490406849
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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: 4,180
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    slow_polk7 wrote: »
    Gardenstater wrote: »
    ... they even have the partial depth mystery forstner bit hole that mine have.

    It appears that, without that relief, the "spring nut/insignia post" assembly would prevent the grille from fitting tightly against the baffle.

    You are correct! I didn't have my glasses on when I looked at mine this morning lol. Flat black spring nut on flat black paint.

    To OP: I wouldn't buy those grills without having the seller re-measure dimensions and ask for the locations of the grill post holes from each other and from edges. If the post holes are in the wrong positions they could always be filled and relocated but it is a bit fussy and not much room for error. I guess I would make a template to drill through.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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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Answers

  • Gardenstater
    Gardenstater Posts: 4,180
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    If you make your own I would definitely use Baltic Birch plywood instead of particle board for more stability/less warpage. And do a roundover on the inside edge. You would be able to take the opportunity to also use a more sonically transparent grill cloth and possibly use magnets instead of the grill pegs.

    Honestly, I never listen to mine with the grills on.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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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  • odcics2
    odcics2 Posts: 309
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    Line the inside edge of the entire grille with a half inch of felt to help get rid of diffraction.

    Keep in mind they were designed by Polk to listen with the grilles on.

    But, whatever sounds better to you is all that matters.
    When it comes to music, our ears are the biggest variable. That explains why there are so many speaker companies!
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  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023
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    There was one speaker line that they made the marketing claim "sounds better with the grill on" but it was definitely not the Monitor 7. I think it was the tower speaker advertisement; 15t etc..

    Yeah, here it is on p. 2 of the technical brochure:

    2is4a1da2e4b.jpg


    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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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  • odcics2
    odcics2 Posts: 309
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    Other speaker companies have used the grilles to advantage... Paradigm comes to mind.
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  • odcics2
    odcics2 Posts: 309
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    Gardenstater wrote: »
    There was one speaker line that they made the marketing claim "sounds better with the grill on" but it was definitely not the Monitor 7. I think it was the tower speaker advertisement; 15t etc..

    Yeah, here it is on p. 2 of the technical brochure:

    2is4a1da2e4b.jpg


    Oddly enough, the bottom illustration is the basis of the Monitor 7 design,
    a hemispheric radiation pattern! Begs the question as to which design is better.
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  • xschop
    xschop Posts: 4,683
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    Grills are for burgers and steaks.
    Don't take experimental gene therapies from known eugenicists.
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  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023
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    The only source for the grills would be eBay. Sorry I didn't mention. I have only seen them go up for sale once in the past 4 years or so, so I wouldn't hold my breath. Except for WAF or small children or pets or your own sensibilities I wouldn't let that stop me from buying if the price is right.

    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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 FacebookShare on Twitter
  • slow_polk7
    slow_polk7 Posts: 33
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    Gardenstater wrote: »
    ... they even have the partial depth mystery forstner bit hole that mine have.

    It appears that, without that relief, the "spring nut/insignia post" assembly would prevent the grille from fitting tightly against the baffle.
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  • subkron
    subkron Posts: 57
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    @Gardenstater "...seller's measurements of 23-3/8" x 13-3/8..." may actually be correct, it depends on where you take the measurements. On my 7Bs the sides & tops are bowed in at the centers. At the top corners I have about 13-15/16" but it is closer to 13-1/2" or so in the middle of the run.

    I actually have Baltic birch on order to make new grills for mine.
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  • odcics2
    odcics2 Posts: 309
    edited April 2023
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    The polk MW and even the tweeters have a tendency to collect dust and grime without grilles. You can see nasty examples on ebay.

    What is a safe way to clean the MW ?
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  • pitdogg2
    pitdogg2 Posts: 24,553
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    odcics2 wrote: »
    The polk MW and even the tweeters have a tendency to collect dust and grime without grilles. You can see nasty examples on ebay.

    What is a safe way to clean the MW ?

    Yes. Original Windex and a microfiber no lint cloth well wetted with the windex. It's best to try and support the driver with your free hand. Carefully clean in a circular motion around the driver starting with the rubber suround working inward. Keep the cloth wet once it starts to dry it will start grabbing the tacky driver surface. I have used 3-4 paper towels folded up with success as well. Once again it will tear and stick to the driver if not well wetted.

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  • odcics2
    odcics2 Posts: 309
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    Thanks!
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  • odcics2
    odcics2 Posts: 309
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    Amazing that the MW can still be tacky after all these years.
    I wonder what’s the composition of that proprietary material.
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  • F1nut
    F1nut Posts: 49,787
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    subkron wrote: »
    I actually have Baltic birch on order to make new grills for mine.

    MDF would be a better choice.

    Political Correctness'.........defined

    "A doctrine fostered by a delusional, illogical minority and rabidly promoted by an unscrupulous mainstream media, which holds forth the proposition that it is entirely possible to pick up a t-u-r-d by the clean end."

    President of Club Polk

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  • Gardenstater
    Gardenstater Posts: 4,180
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    subkron wrote: »
    @Gardenstater "...seller's measurements of 23-3/8" x 13-3/8..." may actually be correct, it depends on where you take the measurements. On my 7Bs the sides & tops are bowed in at the centers. At the top corners I have about 13-15/16" but it is closer to 13-1/2" or so in the middle of the run.

    I actually have Baltic birch on order to make new grills for mine.

    My particle board grills haven't done that to me but they did both take on a bit of a banana shape, which is my fault for being too lazy to install them on the speakers after a listening session.

    Baltic Birch is a bit more difficult to machine than MDF, and can be splintery, but it would still be my choice for a grill frame because of being less dense/lighter and having a MOE (modulus of eleasticity) at least twice that of MDF. Here's some data I found online:

    1wmzpc1ey53l.jpg

    7g3gmyeovw2n.jpg
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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 FacebookShare on Twitter
  • odcics2
    odcics2 Posts: 309
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    What about resonance?
    Isn’t MDF the best choice?

    A lot of high end speaker manufacturers use it.
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  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023
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    odcics2 wrote: »
    What about resonance?
    Isn’t MDF the best choice?

    A lot of high end speaker manufacturers use it.

    Resonance is more of a concern for speaker enclosures, especially if you remove your grilles to listen as I do. The driver is the source of mechanical vibration and is not directly attached to the grill, with the springy grill pegs being the only connection.

    I'll also add that I have never liked how when I go to remove the grills from the speaker by starting at either the bottom or the top, in the action of wresting the strong grip of my grill pegs at that end, it does not easily give up at the other end due to the flexibility of the particle board. Another reason why I think BB would have been better. Would BB absorb less moisture over time and not have as much tendency to warp? Not sure, but I would put a sealer on either one so maybe a moot point then.

    MDF is said to have lower resonant frequency than BB. Subwoofer builders prefer BB to get the resonant frequency up above system operating point. Neither BB nor MDF really have much internal damping to speak of.
    Post edited by Gardenstater on
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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 FacebookShare on Twitter
  • joebass3
    joebass3 Posts: 251
    edited April 2023
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    I think for speaker grills the big concern is warpage. Baltic birch may be better than most, but all plywood has a tendency to warp. Every piece of MDF I have used has been perfectly flat.
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  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023
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    joebass3 wrote: »
    I think for speaker grills the big concern is warpage. Baltic birch may be better than most, but all plywood has a tendency to warp. Every piece of MDF I have used has been perfectly flat.

    Every piece of BB and every piece of MDF I have used have been perfectly flat, initially. BB is void free, all hardwood, 9 plys. Finnish BB is said to be pretty much the ultimate if you can afford it and can find a source, and may be stiffer still than run of the mill BB.

    If you go to the trouble of fabbing your own grills, you sure as heck are going to seal them. If you also do an inside roundover, the need for the grill frame to be as stiff as possible is even greater.

    Just my 2c all of this. We audiofools can worry about everything :)
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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 FacebookShare on Twitter
  • Gardenstater
    Gardenstater Posts: 4,180
    edited April 2023
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    Gardenstater wrote: »
    joebass3 wrote: »
    I think for speaker grills the big concern is warpage. Baltic birch may be better than most, but all plywood has a tendency to warp. Every piece of MDF I have used has been perfectly flat.

    Every piece of BB and every piece of MDF I have used have been perfectly flat, initially. BB is void free, all hardwood, 9 plys. Finnish BB is said to be pretty much the ultimate if you can afford it and can find a source, and may be stiffer still than run of the mill BB.

    If you go to the trouble of fabbing your own grills, you sure as heck are going to seal them. If you also do an inside roundover, the need for the grill frame to be as stiff as possible is even greater.

    Just my 2c all of this. We audiofools can worry about everything :)

    And when we speak of warpage we should specify direction. Plywood is very unlikely to warp in 2 of the 3 directions, due to the adhesive laminated opposing grain direction method of construction.

    Do an experiment. Rip on a table saw 4 pieces that are 3/4" thick x 1-1/2" wide x 4ft long. Do one each: 1) MDF, 2) Particle Board, 3) Baltic Birch across the outer veneer grain, and 4) Baltic Birch with the grain. Then suspend them by a couple loops of string in a non climate controlled outdoor space with a roof over them so that all surfaces are exposed to the humidity in the air. Check them in a year or so. I'll bet you that the BB samples will still be straight as the saw cut them but you will not be able to say the same for the MDF and Particle Board.
    George / NJ

    Polk 7B main speakers, std. mods+ (1979, orig owner)
    Martin Logan Dynamo sub w/6ft 14awg Power Cord
    Crown D150 amp
    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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