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Thread: PR 300 tuning

  1. #1
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    PR 300 tuning

    Does anyone have a thread or other reference on tuning a PR 300 passive radiator?

    Thanks

  2. #2
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    Hi,

    In the technical information section, you will find the loudspeaker component section and there find the 1980 speaker manual. On page 5 is info on the pr15. That should give you some info on how to proceed.
    KEEP ON LISTENING!

  3. #3
    Senior Member DerekTheGreat's Avatar
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    JBL L150A - Passive Radiator Tuning ( PR300 )

    A so called necro thread but rather than make my own, I'll post my findings here..

    This weekend I played with speaker placement and the mass rings on my PR300's. I found that each PR300 had four rings, each weight about 10 grams a piece and a washer+lock washer over a screw similar to those used to fasten the units to the L150A's cabinet. The washer+screw combo weigh about 4 grams each, for a total of ~44-45 grams. It seemed my L150A's were responding too well to lower frequencies while being a bit weak in the upper bass frequencies, aka the "party" bass. That stuff seems to fall between 50-90hz. Removing 1 mass ring from each side while placing the far corner of each speaker 7 inches from the wall and the inside corner 5 inches from the wall resulted in the most pleasing bass presence and response. The difference in distance from the wall gives the perfect speaker "toe-in" for me. I removed two rings to see what that would do and while there was more party bass and the bass seemed a bit tighter, there was less of the "thump" associated with it and a definite loss in the deeper bass- would need a subwoofer to make up for it. So that's why I went with just a single weight removed. That gave me the shift up in the spectrum I was looking for- a tighter thwack in the chest with ample thump to accompany it. I lost a smidge of the subwoofer like performance down low but my conclusion is the modifications made for better overall music listening enjoyment.

    Test tracks:
    Another one bites the dust - Queen
    December: 1963 (Oh, What a Night) - Frankie Valli
    Running - No Doubt
    Middle of the Road - The Pretenders
    Fame - David Bowie
    Hotel California - Eagles
    Let's Dance - David Bowie

    Equipment:
    Marantz 3600 Pre-amp
    Marantz 510M
    Audio Control C101 Series II Equalizer
    Ipod w/ .WAV files

  4. #4
    Administrator Mr. Widget's Avatar
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    Interesting choice, but showing us your playlist it makes sense. None of those tracks have deep bass. If these musical selections are typical of your day to day listening then you probably have made the correct choice. I would suggest you document your modification and stick it on the back of one if your speakers so that a potential new owner could “restore” the speakers back to factory specs if desired.


    Widget

  5. #5
    Senior Member DerekTheGreat's Avatar
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    Quote Originally Posted by Mr. Widget View Post
    Interesting choice, but showing us your playlist it makes sense. None of those tracks have deep bass. If these musical selections are typical of your day to day listening then you probably have made the correct choice. I would suggest you document your modification and stick it on the back of one if your speakers so that a potential new owner could “restore” the speakers back to factory specs if desired.


    Widget
    Deep enough for us to notice, especially on Hotel California and Running. But I do doubt the bass in most of my material is 20hz low but definitely lower the the LX44's would play.. There are passages in H.C. in which there are a few notes followed by an underscore of deeper or deepish bass presence, with plenty of what I call "sustain" to the note. With two discs removed, the "feel" of that sustain from both Hotel California and Running were all but lost. With just one, there was still a noticeable increase in kick-drum impact yet the weight of said impact wasn't lost like with two removed. With zero removed, kick drum presence didn't really hit you in the chest and the speakers seemed more like subwoofers. I mean, if the stuff I listened to didn't have deep bass I wouldn't be able to notice the extra emphasis that has been bugging me the past several weeks. The recone definitely made a difference in regards to speaker dynamics. As the parts have been breaking in, I've noticed bass becoming more present and deeper. Especially when compared to how they were before the fantastic job done by edgewound. You weren't able to feel these things downstairs or across the house before, for example.

    Those weren't the only things we listened to, just what I remembered and what we definitely used for A/B comparison. Mumford & Sons was another, and quite a few of their tracks hit low with plenty of sustain to make out a difference. Funny that my wife thought I was mad and that removing those fiber pucks wasn't going to make a difference. Truth be told, I wasn't sure what to expect either. But if I put these down stairs eventually, all pucks will go back in. I got pretty quick at swapping them, done in roughly five minutes a side.

    Modification has been documented and the weights are retained. These will not get sold, I've got too much money into them and I actually like them quite a bit. I wrote a nice comparison between these L150A's and a set of Klipsch Cornwall I's and despite what I read elsewhere, the L150A's are the superior speaker to my ears. They're more articulate & defined, not to mention they both dig deeper and reach higher than the Cornies. Cornies just don't need big watts like the JBL's do though, which is a serious thing to consider depending on your gear.. Anyway, if I one day pick up a set of L220/L222's and like them more, then the L150A's will replace the E90's downstairs. But the E90's with a hefty amount of EQ reduction make decent home theater stuff.

    I just figured I'd put this information here as the info I found doesn't give layman descriptions of what adding or subtracting weight does, beyond "adding mass will lower the tuning frequency" and vice versa.

  6. #6
    Senior Member edgewound's Avatar
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    Quote Originally Posted by DerekTheGreat View Post
    Deep enough for us to notice, especially on Hotel California and Running. But I do doubt the bass in most of my material is 20hz low but definitely lower the the LX44's would play.. There are passages in H.C. in which there are a few notes followed by an underscore of deeper or deepish bass presence, with plenty of what I call "sustain" to the note. With two discs removed, the "feel" of that sustain from both Hotel California and Running were all but lost. With just one, there was still a noticeable increase in kick-drum impact yet the weight of said impact wasn't lost like with two removed. With zero removed, kick drum presence didn't really hit you in the chest and the speakers seemed more like subwoofers. I mean, if the stuff I listened to didn't have deep bass I wouldn't be able to notice the extra emphasis that has been bugging me the past several weeks. The recone definitely made a difference in regards to speaker dynamics. As the parts have been breaking in, I've noticed bass becoming more present and deeper. Especially when compared to how they were before the fantastic job done by edgewound. You weren't able to feel these things downstairs or across the house before, for example.

    Those weren't the only things we listened to, just what I remembered and what we definitely used for A/B comparison. Mumford & Sons was another, and quite a few of their tracks hit low with plenty of sustain to make out a difference. Funny that my wife thought I was mad and that removing those fiber pucks wasn't going to make a difference. Truth be told, I wasn't sure what to expect either. But if I put these down stairs eventually, all pucks will go back in. I got pretty quick at swapping them, done in roughly five minutes a side.

    Modification has been documented and the weights are retained. These will not get sold, I've got too much money into them and I actually like them quite a bit. I wrote a nice comparison between these L150A's and a set of Klipsch Cornwall I's and despite what I read elsewhere, the L150A's are the superior speaker to my ears. They're more articulate & defined, not to mention they both dig deeper and reach higher than the Cornies. Cornies just don't need big watts like the JBL's do though, which is a serious thing to consider depending on your gear.. Anyway, if I one day pick up a set of L220/L222's and like them more, then the L150A's will replace the E90's downstairs. But the E90's with a hefty amount of EQ reduction make decent home theater stuff.

    I just figured I'd put this information here as the info I found doesn't give layman descriptions of what adding or subtracting weight does, beyond "adding mass will lower the tuning frequency" and vice versa.
    I just serviced a pair of L150s in the shop. Reconed the 128Hs with factory C8R128H and reconed the PR300 with a True Reproduction recone assembly. The previous repair person did an awful job of refoaming both sets, and the spiders of the PR300s were beyond their useful life...stretched all out of shape.

    Moral of the story? Passive Radiators wear out.

    Here's the before:

    https://www.facebook.com/UplandLouds...type=3&theater

    and after:

    https://www.facebook.com/UplandLouds...ref=nf&__xts__[0]=68.ARCC2v7WhFgF2fiBnl_T3m5IycZa2ySnwcTzvlNFmSXYV2 8S63zHeiBY0B_fqxaRP9kO538rkjhO8-tXkid-PZrZqM_FzXuLhtM-TmQQd3Ohl6FNpfGke8qdQYZEMPrGGi8D7vyrsvJwjNusyObgYv pIWMeTxMv9TCoq7xqEKwKR5xu1JJ0op9Ws0137pumCMQqwYHdO mfE66LvGoVoKyxiuLjc3uqO_kgeukVhaDCvrCnEu1NDs9tSO-uCxeLVxfyxBV9TEgzJDODPiTbAcY7Zg98OWxkL5Qn6yXNPSfj-SR_61Hq42UVZUi5m9MPhUySL9RdDw8mBegCFXsd1bygYz8g
    Edgewound...JBL Pro Authorized...since 1988
    Upland Loudspeaker Service, Upland, CA

  7. #7
    Senior Member DerekTheGreat's Avatar
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    Quote Originally Posted by edgewound View Post
    I just serviced a pair of L150s in the shop. Reconed the 128Hs with factory C8R128H and reconed the PR300 with a True Reproduction recone assembly. The previous repair person did an awful job of refoaming both sets, and the spiders of the PR300s were beyond their useful life...stretched all out of shape.

    Moral of the story? Passive Radiators wear out...
    Hey Ken!

    I believe we talked about my PR300's before I sent my 128H's over your way. I believe both the 128H's and PR300's were reconed with incorrect parts by the previous owner and then once more unbeknownst to me by that "official" reconer here in Oxford.. When I had the PR's out over the weekend I recorded the number on the back of each cone and I'll have to post back as to what they are here. Please follow the thread so you can tell me what they actually put in my units. They look very similar to what is supposed to be there, only the woofer cone is a deep purple instead of black and has a pulpy, wrinkled texture on the rear side similar to the 128H cones. Using a tone generator yields a rattle from the one on the left side at higher SPL's, this is not discernible with music playing though. One day, (probably next year..) I will arrange to have you recone those as well so my L150A's can be like the factory intended. Do you know how many discs are supposed to be on each PR300 from the factory? First time I took mine apart I noticed one side had three and the other had five..

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