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passive radiator q's

Thoughts / suggestions on pairing a 10in passive radiator with an 8in MCM 55-5670 woofer, vs porting.
Additionally, would the DA DS270-PR 10 match up better to this woofer than the RSS265-PR (which I’d expect to be a better match for a sub driver) ?

Thanks

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Comments

  • `There is no other method than to build a model. If the 10 inch PR has a lot more XMAX than the 8 inch MCM, it might work.

    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • Yep, model model model. The MCM is a great driver, but it doesn't really get much into the 40's without a large and weird alignment.

    I have a signature.
  • model model model is a bit of an issue for a mac...

    getting just into the 40's would work

  • the ds270-pr 10 has an Xmax of 11mm, the rss265-pr 24mm
    the MCM 55-5670 7.5mm

  • For mac, install parallels and run windows in a VM. VituixCAD can run perfectly well through Wine as well, all that is required to install in wine is .NET 3.5 IIRC. I am in email conversations with someone on a regular basis who is using VituixCAD and REW on an M1 mac.

    I'm not deaf, I'm just not listening.
  • @tajanes said:
    the ds270-pr 10 has an Xmax of 11mm, the rss265-pr 24mm
    the MCM 55-5670 7.5mm

    I've got a spare PE buyout 12 inch PR (or 2) . Yours for the cost of shipping. It should work perfectly with the MCM

    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • Don,
    Thanks for the offer, but I'm trying to keep the spkr < 12 width as my current open baffles need to be replaced with a little more living room (i.e. WAF) friendly design.

    dcibel,
    I had tried parallels in the past and my old iMac struggled. That being said, I'm downloading it now on my new iMac- should be no problem (other than the issue with what's between the keyboard and the chair)...

  • Probably telling you it's time to buy a real PC. Do you have VBA toolkit installed? macros enabled?

    I'm not deaf, I'm just not listening.
  • Enabled macros, then this message popped up.
    Installed toolkit with download.

    Seems like similar issue as in the past? Any suggestions to getting this program to work via Parallels would be appreciated.

  • edited February 12

    Install excel 2016 or earlier, 32bit preferred, install vba analysis toolkit, enable macros. That’s pretty much the entire process iirc. Or just install VituixCAD, it covers everything that old spreadsheet does and more.

    I'm not deaf, I'm just not listening.
  • I’ll give it a go- thx

  • 40Hz in a large enclosure for an 8" woofer sounds like a port of sufficient size could easily be used, which is always better than a passive radiator. Those DS series PRs are pretty lossy too, which shows up in the modeling as reduced output down low compared to a port.

    rjj45PWRRYD
  • edited February 12

    You definitely need the 32-bit Office. I had the same errors with 64-bit Office and switched to 32-bit. No more errors.

  • dcibel...or just install VituixCAD...
    THX It's up and running, now time to do some homework with this program

    dcibel
  • edited February 12

    Loading a PR from the database into the cabinet model can be a bit clunky, but it works.

    Once you have your driver selected for the enclosure design, select radiator type -> passive radiator. Then check the "PR" checkbox at the top of the window to show only the passive radiators in the database, select the desired PR, then "get from table" at the bottom left to load the PR parameters (enclosure tab).

    I'm not deaf, I'm just not listening.
  • edited February 17

    so, looks like I'll be going with a port
    Q: thoughts / recommendations on port id best/reasonable practices?

    I'll be targeting a net internal vol of ~ 1.1 ft^3, so thinking a 2.5 id with this driver would work

  • In the design/simulation software, aim for port velocity <17m/s under normal high volume listening conditions, <25m/s maximum .

    rjj454thtry
    I'm not deaf, I'm just not listening.
  • great- thx for info

  • IF I have the info in correctly, a 2.5 id shows max at 3.0 m/s, a 2.75 max 2.6 m/s
    Looking at the red line as the max in VituixCAD around 40Hz (seems too good, so I'm probably doing something wrong?)

  • @tajanes said:
    IF I have the info in correctly, a 2.5 id shows max at 3.0 m/s, a 2.75 max 2.6 m/s
    Looking at the red line as the max in VituixCAD around 40Hz (seems too good, so I'm probably doing something wrong?)

    Got to input the voltage desired for maximum SPL listening level. 90 dB is usually plenty loud

    Don, Donno, or "Hey you" all work for me, But never "Mr Johnson"
  • sorry, a newbie with this VituixCAD,
    even at 100dB looks like I've got something not quite right

  • Looks fine, but your simulating at 11W input power only, keep cranking up until cone excursion >50Hz starts approaching Xmax.

    Keep in mind that SPL on enclosure model is half space model at 1m, so baffle step losses is not included and actual SPL at listening distance not included. Reality in room is a lot more complex than that SPL graph.

    rjj45
    I'm not deaf, I'm just not listening.
  • edited February 18

    2.5in is probably fine given the power level of 112W and Pmax for the driver at 80W. Do you often crank it to 11? If so, maybe go with a larger size.

    If I can interject on the cabinet choice, it seems a bit small and with not a lot of bass extension for an 8" woofer. You've also got Ql set at 3 which would be an rather leaky cabinet. I think you can get a fair bit more bass out of that driver with not a much larger box.

    Try using 45L, and tuning of 40Hz, Qa= 15, Ql = 10

    Qa = Q of "stuffing"
    No fill : Qa = 100
    Minimal : Qa = 20-50
    Normal : Qa = 10-20
    Heavy : Qa = 5-10

    Ql = Q of leakage
    Some rules of thumbs

    Vented box, small ~ 30 litre : Ql = 15
    Vented box, medium ~ 60 litre : Ql = 7
    Vented box, large 100+litre : Ql = 5-7

    You will find that the lower tuning and adjusted Q values I suggest also demands a larger port size. I'd go for 3" port for that woofer (7.6cm)

    rjj45Steve_Lee4thtry
    I'm not deaf, I'm just not listening.
  • The impedance plot caught my eye as it's missing the traditional bass reflex double hump (or the first hump is below 10 Hz). I did a quick sim of the 55-5670 in WinISD using your parameters and the manufacturer's driver's specs. It produced very similar results for most plots, but the impedance plot looked like this.

    4thtry
  • edited February 18

    WinISD uses Qa = 100, Ql = 10 by default, adjustable by the advanced button in the box tab. It produces the same result as VituixCAD with the same input data.

    Looking closer at @tajanes screenshot above, it looks like Rms and Cms is entered incorrectly for the driver as well. Change Cms to correct value of 0.974, and set Rms to zero so it is recalculated, will correct the sim a bit including the impedance off the chart at low freq that Ed mentions.

    Steve_Lee4thtry
    I'm not deaf, I'm just not listening.
  • guys, thanks for taking a close look> I've gone in and corrected driver entries
    definitely brings into question the power handling/excursion of this driver per my objectives (mid 40's f3)

  • As far as the cabinet model goes, it performs rather well for an 8" woofer. The cabinet I suggested above provides F3 of 41Hz and plenty of power handling, so you should be good to go.

    I'm not deaf, I'm just not listening.
  • edited February 18

    I may be jumping off the deep end, but since I'm looking at replacing my open-backs with something much smaller (waf for the living room) thinking in the neighborhood ~20ht x11w x13d inches, maybe I need to go a different route.

    I'll be sticking with biamping (legacy powerbloc4 per ch 325w @8ohm and 650w @4ohm) and miniDSP for active Xover between the woofer and a Beyma 5cx200Nd coax (using a passive for the coax), so I can push the low end. I sort-of remember an old AudioExpress article where someone took a very large Pro woofer in a small(er) box and eq'ed it, and matched with a horn (great article btw, if I can find it I'll post). So, looking at maybe getting DA RSS210HF-4s in either a closed or Aperiodic vented (I have a couple of Scanspeaks laying around) and see if I can get f3 towards the low 40's keeping the surrounds intact... Playing around with the software it looks possible.

    Has anyone played with these drivers? Thoughts?

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