Passive radiators, What exactly do they do?

Discussion in 'Archived Threads 2001-2004' started by jeff lam, Sep 26, 2001.

  1. jeff lam

    jeff lam Screenwriter

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    I've seen these on many of your projects and in catalogs. What are they used for and what exactly do they do to the sub?
     
  2. jeff lam

    jeff lam Screenwriter

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    OK, So what is everyones personal opinions about PR's? From what I gather, they are best when a long/large port is desired but not available. Is this correct?
    Would these work well on the top of a down-firing tube sub? Like SVS but use a PR instead of a port?
     
  3. John Morton

    John Morton Stunt Coordinator

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    I'm no expert - too many time constraints, BUT, I say go with PRs.
    My Infinity HPS-1000 sub has a 15" down firing driver with dual 15" PRs (on each side of the roughly 100 liter enclosure). I did near field testing and found that the driver is almost perfectly flat from 100 down to around 40, where it slopes down slowly (well, excluding the 70 hz +5db gain which in use makes it flat because I cross it at 60 hz - too cool, my mains drop at 80 and the sub picks up at 80 :). At 20hz the driver is substantially lower in db. The cool thing is the PRs slope up in an almost exact mirror of the driver's drop. They then flatten out to the same db level that the driver was at to begin with. The PRs then start to slope down slowly at 20 hz. The end result at a 45 degree angle to the sub enclosure is a damn near perfectly flat response.
    My friend and I ran the same tests 4 different times because we just couldn't believe what we were seeing. We figured we must have been doing something wrong, but we got exactly what we expected when we measured his sub (not a terrible curve, but certainly NOT flat. We even re-ran these tests with the HPS-1000 higher and lower to the ground (too high created a harsh mode). All I can say is Infinity must have done something right!! In HT use, it can shake the entire house!!!! In music use, I have NOT heard anything better!!!!
    My old Infinity HPS-500 has FAIRLY CLOSE to the same volume, a 15" driver, and a rear port. I THOUGHT it was good until I got the HPS-1000.
    Just my 2 cents!!
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  4. Geoff L

    Geoff L Screenwriter

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    Im sorry I have nothing to add about the PR question and hope you dont mind me asking another dealing with the HPS-1000.
    Question for John M,
    Allways was curious as to how the HPS line of Infinity subs performed. Thier first attemp at PR's that I know of. Never have gotten the chance to listen to any of the line as no one in our area carries them.
    How dose the 1000 do down low. 25 and down?
    Have you done some max spl measuring to audiable distortion, along with the responce work you posted. Of course room size and sub location would make a large difference on both flat curves an max spl. Given it's design and 1000 watt power rateing would have one belive this is quite the SPL performer to boot.
    What type of limmiter are they useing if any?
    Although BU line some like, but to me nothing but a boom box, yuck. Thier new lines I have not listened to yet, and some speak well of them though my interest is only in the HPS-1000. I no many use BU line and are very happy, this is just my opion. Most certainly not trying to compare the two lines as its apples to oranges.
    Thanxs
    Geoff
     
  5. TerryC

    TerryC Stunt Coordinator

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    My Friend Lewis Beesze has a HPS-1000. We compared it side by side to my old ported Shiva 4.1ft3 tuned to 21hz. From what I remember the Shiva extended considerably lower from 28hz on down. Above that they were pretty much neck and neck. Its tuned rather high too, Louis told me the PR's move a lot on Frequency sweeps in the 30Hz area which suggests that may be their tuning area.
    Lewis ended up blowing the driver in his while watching some DVD at reference, he is actually one of the few people that listen at reference constantly.
     
  6. Geoff L

    Geoff L Screenwriter

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    Thanks Terry,
    It would seem the 30 hertz or so tunning is what I would assume from your post that Infinity was looking to do for smoothest freq responce along with spl. At it's size, cabnit wise, most but the (harder core deep bass guys) [​IMG] would find it acceptable.
    At it's price there is no doubt a better performer could be built that would easily surpase it in all areas of performance.
    Most non-pro reviews ive read (not that many either) like it's over all performance. Given it's size and attractive looks most like everything but the price!
    Thanks for your input...
    Geoff
     
  7. Lewis Besze

    Lewis Besze Producer

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    As Terry said the Shiva was flatter,then the HPS-1000,however this sub around 35hz is an absolute killer.
    I would say the tunning is around somewhere 25hz[below 30hz for sure].
    The driver is made by JBL.After a few enthusiastic demo of the TPM LD sent the woofer to oblivion,and it was replaced by a JL Audio 15W6.
    This driver actually was flatter then the original and cost less then the replacement driver from Infinity[JBL] would have been.
    Another unfortunate demo with the Matrix chopper scene and the amp was smoked literally.
    Now it's being driven by a Mackie M-1200,and being eq'd by a Behringer FBD,and sound better then ever.
    As Terry pointed out I'm reference level guy,so I asked him to build a sub that can raech 115db at the seat,at most of it's frequency band[20-80].
    He succeeded.
    Check out the "Made a new sub" thread for more info in the "hardware" section.
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    "You Hungarians always disagree"
     
  8. John Morton

    John Morton Stunt Coordinator

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    Thanks for the info Lewis!!
    Unfortunately, we didn't get too far past the near field tests. My friend was building a 140 liter sono-tube with a Shiva and he was most interested in near field comps. He didn't have the Shiva at the time, but I was impressed with how good his sounded with a Velo 12" driver. He now says his Shiva in this enclosure does sound substantially better than before and is almost perfectly flat to 20 hz.
    I agree, you'll be pushing the HPS-1000 pretty hard at reference, and especially in a large room. My room is 13x18, watched via the short side (foyer entrance on one end :-(. I listen at about 85 db at the listening possition. I keep the volume at 5.5 out of 10 for movies and 3.5 for music. It's all the sub I'll ever want for a room this size.
    I guess for me it also comes down to price and time. My friend has about 100 hours and $400 into his Shiva. I have 2 hours of placement experimentation and $450 in my HPS-1000. He has some knowlege and experience I don't have. I'd be hard pressed to find that much time right now.
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  9. John Morton

    John Morton Stunt Coordinator

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    Sorry Geoff!! Didn't mean to miss replying to you!!
    I had a BU-80 with the Infinity Minuette speakers. I've also listened to the larger BU-120. Anyway, I called Infinity to ask them before I bought the HPS-500. They told me the BU series was strictly their entry level sub. The HPS series however stands for High Power Series and was designed for audiophile applications. I agree, IMO, the BU subs I've heard, although I thought they sounded great at the time, were pretty much boom boxes. I still have an Infinity HPS-500 which sounds WAY better than any of the the BU line, but not even close to the HPS-1000. Again, IMO, it comes down to experience. I hadn't listened to many subs when I started out a few years ago, so the BU-80 sounded great. Now I realize that there will always be something that sounds better. I can say that the rumors of the LFE input not working on the HPS line are correct on SOME OF THESE SUBS. I have used 3 HPS-500s and 2 HPS-1000s. The last HPS-1000 I got in did have the LFE problem. NOT A BIG DEAL THOUGH!! All I had to do was replace the SMALL board inside the power supply on the back of the sub and it works great. I basically re-made the board from scratch using the original as a guide. I'm very happy with the HPS-1000 for the size and makeup of my room.
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