Polk R-300 - the difference a crossover makes

Discussion in 'Loudspeakers' started by Swerd, Oct 9, 2007.

  1. Swerd Audioholic Ninja

    Swerd
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    A friend of mine, Dennis Murphy, likes to design hifi speakers, especially their crossovers. Occasionally he buys something on sale for a ridiculously low price, tests them, and designs a new crossover that is inexpensive, but improves their response. He recently did this for some Polk R-300s available for a special price of $50 a pair.

    First read this introductory thread.
    He then posts a number of frequency response curves. The first 3 are with the original Polk crossover, and the rest are with his new crossover. He says the new crossover parts cost about $23 for each speaker. Not too bad - what a difference a good crossover can make :D.
  2. jonnythan Audioholic Ninja

    jonnythan
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    Fascinating. I wonder if the R300 and R30 use the same drivers.... ;)
  3. Swerd Audioholic Ninja

    Swerd
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    If you're really interested, ask Polk.

    Even if the drivers are the same, the tweeter on top vs. woofer on top layouts on the front baffle will create a different sounding off-axis presentation. As a result, they may have quite different crossovers.

    It just may be possible that Polk is replacing the R-300 with the R-30 because of the problems that Dennis pointed out.
  4. jonnythan Audioholic Ninja

    jonnythan
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    The R300 is newer. The R30 is apparently getting replaced by the R300.

    I'll see what Polk has to say.
  5. GlocksRock Audioholic Spartan

    GlocksRock
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    I always thought my old Polk R series speakers sounded pretty good, but they don't hold a candle to my def techs! But for $100/pr. you really can't beat them.
  6. RuSsMaN Enthusiast

    RuSsMaN
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    The R30 is oop. The R300 is it's direct replacement. You have two models now in the R series, and the new M series. They are made for different retail establishments, but for all intents and purposes identical in performance - the cosmetics and driver layout are changed to cater to different crowds. The R series has more modern 'euro' style and are rear ported, while the M series retains a more conventional look and are front ported.

    Two floorstanding models:

    http://www.polkaudio.com/homeaudio/products/individual/floorstanding/m20/
    http://www.polkaudio.com/homeaudio/products/individual/floorstanding/r300/

    Two bookshelf models:

    http://www.polkaudio.com/homeaudio/products/individual/bookshelf/m10/
    http://www.polkaudio.com/homeaudio/products/individual/bookshelf/r150/

    Interesting mods too. It's amazing what one can do with entry level products that have a solid foundation to begin with.

    Cheers,
    Russ
  7. jonnythan Audioholic Ninja

    jonnythan
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    The R30 uses the same woofer, but a different tweeter.

    Someone else on the PE forums posted his results for a replacement crossover for the R30 and they look good.. so I might be trying that out :)
  8. Dennis Murphy Audioholic Chief

    Dennis Murphy
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    I'm amazed that the 300 is the newer version. Placing the tweeter below the woofer requires a very specific type of crossover, which the 300 doesn't have. The result is a serious lack of energy as you move above the tweeter axis. Since the 300 cabinet is only 33" high, the ear will be way above the tweeter unless the cabinet is placed on a base of some kind. I know there are all kinds of talented engineers at Polk. I wonder who isn't letting them do their job. Dennis Murphy (I think that will show up as dennis murhy on my signature--I have a sticky P key. I can't figure out how to edit my name.)
  9. RuSsMaN Enthusiast

    RuSsMaN
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    Actually, the R30 and R300 don't share the same midwoofer. They aren't worlds apart mind you (very similar mechanical and electrical specs), but they are different drivers.

    The new R series and M series were complete re-designs for the entry level market.

    Cheers,
    Russ
    Last edited: Oct 12, 2007
  10. RuSsMaN Enthusiast

    RuSsMaN
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    Dennis, there is also the M20 that I linked to. (and can also be found at rediculously low sale prices on occasion)

    It's a styling option for Joe Consumer. Chances are he is going to be a good 5-10db deep in tone controls, loudness contouring, and dsp's etc etc. Is that an excuse for the design? I don't know. What I do know, is two products are offered at the pricepoint, with similar performance, but different designs to cater to different (cosmetic) tastes.

    I'm sure research panels / public polling and what not comes into play, I've taken a few for certain speaker companies, and most don't even ASK about the SOUND!!! 'Which speaker looks better, which one would you buy'

    You'll find the refinement 'up the lines'. Entry level products are full of compromises. Some more obvious than others.

    Cheers,
    Russ

    PS- the Engineers have been busy, 11 new subwoofers, the new VM and RM series, new RTiA series, not to mention the custom install / inwall / floor / ceiling and 12 volt products. ;)
    Last edited: Oct 12, 2007
  11. Dennis Murphy Audioholic Chief

    Dennis Murphy
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    Well, I certainly can't complain about the drivers. Excellent value. But it does depress me to think that consumers really equate sonic suckouts with superior sound. It's not a matter of $$. I only used two caps, two coils, and a couple of resistors. Anyhow, thanks for the polite reply. I appreciate it.
  12. RuSsMaN Enthusiast

    RuSsMaN
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    Anytime Dennis, I've heard nothing but good things about you over the years.

    So, are you taking preorders? I just ship my crossovers out? ;)

    Cheers,
    Russ
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  13. jonnythan Audioholic Ninja

    jonnythan
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    How do you know?

    Here is what Polk told me:

    "The drivers are the same but the tweeter is different. The R300 uses
    tweeter part # RD1901-1 and the R30 uses RD6516-1."

    I read this as saying that the woofers use the same part number.

    edit: I see you are also from Polk :D

    So, R300... better or worse? :)
  14. RuSsMaN Enthusiast

    RuSsMaN
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    Actually, you are right, and I am wrong. They do share the same midwoofer. My parts sheet is incorrect!

    I like the R30 over the 300, and the M20 over them both as far as the entry level models go.

    Cheers,
    Russ
  15. patnshan Senior Audioholic

    patnshan
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    I'd love to have those crossovers to try them in my R300's. I like them, but a $46 part that could make a difference would be worth it to me.
    Let me know!
    Thanks,
    Pat
  16. Dennis Murphy Audioholic Chief

    Dennis Murphy
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    Hi I'm certainly not going to keep the new crossover a secret. Just e-mail me if you want the schematic (rdmurphy13@verizon.net). The woofer section is just a 1.5 mH inductor in series, and then an 8.0 or 8.2 uf capacitor to ground. The tweet section starts with a 4.7 series cap, with a ground circuit consisting of a 3 ohm resistor in series with a .40 (or .39) mH inductor. And it finishes off with a 2-3 ohm series resistor. My 2 Polks measured a little differently in the highs--one needed a 3 ohm series resistor for flat response, the other only a 2 ohm. I'm finishing up my pair. I'm installing 1.5" acoustic barrier material from Parts Express in the upper compartment behind the drivers (the cabinet is braced below the woofer--glad to see that). I'll let you know if I think the new sound treatment improves things.
  17. Swerd Audioholic Ninja

    Swerd
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    The schematic should look like the attached figure, and the parts list including part numbers for Parts Express.

    Polk R-300 crossover parts

    Inductors – Jantzen air core
    1.5 mH #255-260 18 gauge
    0.4 mH #255-032 20 gauge

    Capacitors – Dayton polypropylene
    8.2 µF #027-426
    4.7 µF #027-422

    Resistors – Dayton non-Inductive 10 watt
    2 Ω #004-2
    3 Ω #004-3
    Total $42.40

    Attached Files:

    Last edited: Oct 19, 2007
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  18. Dennis Murphy Audioholic Chief

    Dennis Murphy
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    Revised Polk 300 crossover

    Yup--that's what it looks like. Thanks very much. You can also use an 18 ga for the .40 shunt coil in the tweeter circuit. That's actually what I used. If you're going to place the speakers near a rear wall, you can use a 1.25 mH coil in the woofer circuit.
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  19. fightingfish Enthusiast

    fightingfish
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    I am wondering the same thing as John L. asked in the external thread linked in the first post here. Could the Polk R50's crossover be reworked to provide improved performance?

    I ask because my brother and I just built crossovers for his Natalie P's. Neither of us ever really held a soldering iron before. However using a schematic we didn't need to understand technically what we were doing.

    I own the Polk R50's and enjoy them much more than the stock htib speakers I used to have. Maybe over time I'll be able to pick out what I like and dislike about them.
  20. Dennis Murphy Audioholic Chief

    Dennis Murphy
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    Hi I'm sure they could be improved. But I've lost track of what current models are being heavily discounted and have the tweeter on top. I don't want to futz around with lame ducks. Is there an R500? If so, is it more current than the R50?
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