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Discussion Starter · #1 ·
Would someone please straighten out my thinking on the differing effects that enclosure volume has on sealed vs. ported subs output? This is a math question, not a my favorite sub question.


The example I am currently pondering is the "giant killer" rumors that have been said about the upcoming Rocket UFW-12... If I make the assumption that the giant to be killed is the SV PB-12 Ultra, wouldn't the 8000^3 inches of the UFW-12 put it at a significant natural (pre-EQ & amp correction) disadvantage to the SV PB-12 Ultra's 11250^3 inches? That seems like a lot of volume advantage to overcome with amp, eq and other methods.


Am I looking at this correctly or do sealed subs play by different interior volume rules?

Thanks,
 

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If the UFW-12 beats the PB12-Ultra in clean (THD under 10%) output below 30 Hz, I'll promise to eat my hat. ;)


Jokes aside, you can't really compare two completely different subs/designs. But if you compare the results of the same driver either in sealed or vented box, the vented one beats the sealed one in both extension and SPL (down deep).


The woofer in a sealed box will need much more Xmax and power handling to keep up with the vented one.
 

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Nope, same rules, aka Hoffmann's Iron Law.


The only way the Rocket could overcome SVS' output and extension advantage is with more power, as well as a driver with the capability to dissipate the extra heat that goes with it.
 

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Quote:
Originally Posted by noah katz
Nope, same rules, aka Hoffmann's Iron Law.


The only way the Rocket could overcome SVS' output and extension advantage is with more power, as well as a driver with the capability to dissipate the extra heat that goes with it.
Power isn't enough, if the driver doesn't have a sufficient Xmax, it will bottom out before the amp clips or the voice coil melts.
 

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A ported alignment will yield approximately 9 dB more output at the ported sub's tune point, using the same size driver with comparable parameters.


The UFW-12 is utilizing twice the ampage, so that will reduce the deficit to approximately 6 dB...at the tune point.


When appyling EQ to a sealed sub, the size of the box is less relevant than the capabilities of the driver in the box it ends up in. It's usually best to model the driver in progressively larger boxes until you acheive the maximum flat response with EQ and still have 15-20% X-Max headroom.


MLS was never trying to design a 1X12" sealed sub that equals a 1X12" ported sub's output all the way down to tune, otherwise, he would have designed an ultra beater ported sub.


It will take 2 UFW 12s to match the ultra...at it's tune point. Below 20 Hz, both subs are irrelevant and above 20 Hz, the sealed sub will eventually catch up top and surpass the ported sub's output, which is again, irrelevant in most user's cases.


The real question is: Does the UFW-12 match the ported sub in SQ at normal listening levels in an average sized room in a smaller package?


Given that R-DES comes with the UFW-12 package and we're talking about the average MC audio room size, I would say it easily will.


Max SPL is a rather ridiculous argument as I have always said, 'If you want more output, buy more subs'.


Just an opinion.


Bosso
 

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Discussion Starter · #6 ·
Thanks guys! Great info... I wonder if my failure to account for interior volume brings the margin closer... I now recall that the UFW didn't have a base plate (couple of inches?) and then there's internal bracing...


Also, judging by the weight of the ultra, I'd say there's more wood in there.


Being that I'm in a
 

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Quote:
Below 20 Hz, both subs are irrelevant and above 20 Hz
Hi Bosso-


Would you please clarify your comment? I thought the ultra could hit 16hz fairly well.


Thanks,
 
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