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I recently aquired a 10" Dayton rss265hf-4 and was considering buying two sd270-prs and building a sub for home theater. I have read lots of previous peoples builds with the sdx (mikep's) build and was wondering if the similar enclosure size would work the room is 14x20x8 open one side and would most likely be running it with a bass 300 amp. I am looking for an overall good sun that has punch for hometheater and is also good with music.

Any advice would be greatly appreciated.

Thanks
John
 

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While PRs aren't a bad idea, those particular SD270s would require at least 5 cu ft to tune well. It's possible however that a different pair of PRs tune better.

Even a vented RSS265 requires about 3.8+ cu ft to get decent extension so PRs wouldn't be likely be much lower than that number.
 

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I'm still trying to figure out why people use pr's. Just build a nice solid slot ported cab tuned to ~20hz (maybe 18hz if you can spare the space). Play around with the knobs in WinISD until you get a nice smooth response. Read the LLT post if you haven't already. You'll get non-ideal sound up to 2*tune_freq (and group delay), so tune as low as you can.
 

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Why use PRs: 1) smaller gross cabinet volume 2) no port noise 3) no port compression at high SPL 4) same performance possible as ported

From what I've read, port compression is more common than you would think. It's also harder to identify since it isn't there at low listening levels. At the same time, it's easier and cheaper to go with ports instead of PRs...
 

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smaller gross cabinet volume
Assuming the chosen passive radiators are actually going to work in the given cabinet volume.

2) no port noise
3) no port compression at high SPL
There's still non-linearities at high SPLs/excursions.
 

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I would assume the PR is properly chosen for the application, and of course it has it's own limitations. The deep notch in a PR build's response is irrelevant as it falls below the passband anyways. The steeper bottom end roll-off is a factor also, but not very significant since this is most often at 20Hz or below anyways. Also, the "max tolerable port velocity" depends on the size of the port, 17m/s is can be a rule of thumb for a 4" port. A little lower for smaller and a little higher for larger.
 

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Yep, that's basically what I gathered when I read a few threads after my post. All told, I would definitely port over again (except I would use a slot instead of round). I think my 7" ports are doing ok at the limits of my Titanics. Not measured ok, just a good hunch based on a bunch of 15Hz kicks to my head. But yeh, it's true, my two cabs are somewhat huge and heavy.
 

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You can get externally loaded PRs to change the tuning for your room without having to remove the PR or anything, since you can access from the outside.
 
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