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Passive Radiators, enclosure design and is it worth it?

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  • Passive Radiators, enclosure design and is it worth it?

    Guys, recently i saw the http://techtalk.parts-express.com/fo...ve-aggressives post and thought i would like to look into the possibility of using a passive radiator, but the entire concept confuses me. Some people mention that you use a box design suited to a sealed enclosure others say it is rubbish and dont do that use the sealed. I've also read that they should be double the displacement of the active driver. So made me think of how it is actually modeled, as i have only used WinISD really once, i was wondering is this the best piece of software to model the curve?

    For example i hate throwing things away and if i was to use the 3.5" Tectonics i've used previously i would need to have either a singular 5 or 6.5" PR. These passive radiators look to have a FS of under 40hz, so would one normally model this and do you need to design a crossover or filter or modify a box design?

    http://www.mh-audio.nl/PassiveRadiator.asp

    i had a look at this site as well for some guidance and i realize that online calculators aren't recommended, but not really sure how else to approach this.

  • #2
    Generally speaking, you use a PR where the port would be impractically long, usually because of a smallish box and low tuning. Some people also like them because a PR suppresses midrange radiation out of the box better than a port.
    Francis

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    • #3
      Originally posted by 3rutu5 View Post
      From what i can see you need a larger box with a PR to achieve what you could achieve with a smaller ported box? .
      The actual net box size is the same but a PR takes up less space than a port and its duct, so the overall size of a PR is smaller. The main reasons you don't see many PRs is they cost more than ported boxes, and they can be difficult to tune.

      www.billfitzmaurice.com
      www.billfitzmaurice.info/forum

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      • #4
        To be brutally honest, i liked the look of these very expensive speakers and me being me was thinking could i make a budget banger equivalent (well similar looks) using a 3.5" driver and substituting a PR for the subwoofer. so not really an equivalent in any way, shape or form.

        After having the boombox and the Tlines side by side and noticing the difference albeit having the same drivers, i thought i could get much much more out of the T-Lines with a redesign
        Attached Files

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        • #5
          The PR won't give you any more bass than a port would. But if you like the look, go for it!
          Francis

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          • #6
            Originally posted by fpitas View Post
            The PR won't give you any more bass than a port would. But if you like the look, go for it!
            right, i think the boombox enclosure specs would work best then

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            • #7
              PRs are NOT like closed boxes (either in size or F3). They are very much like vented boxes.
              WinISD (the "Pro" version) does PRs, but it won't offer you any suggestions (like it will for closed or ported).
              All you have to do is find a VENTed box size and tuning you like, then try to dupe that using the PR of your choice.
              Since PRs can add (potentially) a lot more co$t to a project, I'd only use them (if money is an issue at all) when it would be hard to fit a proper port into a (typically smaller) box.

              In 0.17cf, you can tune the box to near 60Hz using either a 1"id x 2-1/2"long tube (an easy fit - and NEARly free!?), OR your 290-217 PR w/10g added mass, for +$14.

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              • #8
                Originally posted by Chris Roemer View Post
                PRs are NOT like closed boxes (either in size or F3). They are very much like vented boxes.
                WinISD (the "Pro" version) does PRs, but it won't offer you any suggestions (like it will for closed or ported).
                All you have to do is find a VENTed box size and tuning you like, then try to dupe that using the PR of your choice.
                Since PRs can add (potentially) a lot more co$t to a project, I'd only use them (if money is an issue at all) when it would be hard to fit a proper port into a (typically smaller) box.

                In 0.17cf, you can tune the box to near 60Hz using either a 1"id x 2-1/2"long tube (an easy fit - and NEARly free!?), OR your 290-217 PR w/10g added mass, for +$14.
                Cheers Chris, i think i need to drop the look and work a "Free" port into the design. If i was to use the timber internals and do a rectangular port from the looks of it, i would need 0.5" x 3.5" that is 7" long (sorry i worked in MM, so 13mmx85mm which is 177mm long)

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