Front PRs and phase
mdaudioguy
Posts: 5,165
Sitting here listening to my Monitor 11s tonight (got some 10s in the garage, too - wonderful speakers!) and was wondering how they work... If the passive radiator is pushed outward when the mids are pulled in, wouldn't they be out of phase with each other? Is there some sort of compensation for this in effect, or am I over-thinking it?
Post edited by mdaudioguy on
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You know, I've often wondered the same type of thing about radiators. Obviously it works but I have heard some say that it's a "certain sound" some might not like. I'm guessing this is referring to phasing, maybe? All I know is that I do like it. It would be neat to get some type of scientific explanation though...Remember, when you're running from something, you're running to something...-me
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A PR acts just like a port(most of the time). They're used in cases where a port size/length wouldn't be practical.
Edited..."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Some great info:
http://www.polkaudio.com/forums/showthread.php?45157-Passive-Radiator-Question
http://www.aespeakers.com/PRFAQ.php
http://www.salksound.com/wp/?p=144
http://www.subwoofer-builder.com/passive.htm"He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche -
Very good articles, thank you!Remember, when you're running from something, you're running to something...-me
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http://www.ehow.com/how-does_4965125_passive-radiator-work.html
http://www.centerpointaudio.com/PassiveRadiators.aspx
The RTA 11's have two PR's each tuned to a different frequency. They both use the same air pressure created by the MW drivers to extend the bass response. I actually almost always prefer a PR to a port, obviously there are some excellent ported speakers out there, but the PR just seems more natural to me in many cases, less colored. But the design has everything to do with it.
I think if you watch the drivers with the naked eye you will see they all move in unison, not out of phase. It would be interesting to see a Mythbuster's style high speed camera slowed down to see what's actually happening. If they were out of phase as you suggest it wouldn't work.
H9"Appreciation of audio is a completely subjective human experience. Measurements can provide a measure of insight, but are no substitute for human judgment. Why are we looking to reduce a subjective experience to objective criteria anyway? The subtleties of music and audio reproduction are for those who appreciate it. Differentiation by numbers is for those who do not".--Nelson Pass Pass Labs XA25 | EE Avant Pre | EE Mini Max Supreme DAC | MIT Shotgun S1 | Pangea AC14SE MKII | Legend L600 | BlueSound Node 3 - Tubes add soul! -
Well, I could be illogically trying to think logically through it...I think if you watch the drivers with the naked eye you will see they all move in unison, not out of phase. It would be interesting to see a Mythbuster's style high speed camera slowed down to see what's actually happening. If they were out of phase as you suggest it wouldn't work.
After reading through Face's links, I've reached the conclusion that I no longer care how it works - just that it does!
Interesting reading, though.
So, do you really think it's possible to detect phase differences with the naked eye? I agree that a high speed camera study of it would be interesting. Would surprise me if there wasn't some video available online somewhere... -
Naked eye, maybe if you're using 10-20hz test tones."He who fights with monsters should look to it that he himself does not become a monster. And when you gaze long into an abyss the abyss also gazes into you." Friedrich Nietzsche
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One disadvantage in operation is that the radiator is exactly "out of phase" with the woofer, meaning that its cone moves out when the woofer cone moves in, and vice versa, lending marginally audible effects in certain registers.
At the lower frequency where the PR resonates and produces its ouput, the MW's are becoming ineffective so the PR becomes the dominant driver. Phase inversion is not an issue since it's only out of phase with the tweeters at that point.'65 427 Shelby Cobra
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My unscientific understanding of how a PR works it that PR is taking the backward motion/energy of the powered driver and projecting it outside of the box by using air pressure inside the box. Like wise the port lets the backward motion/energy outside of the box via the port. Both the port and the PR are tuned for the desired frequency, for the driver and speaker box volume.I like speakers that are bigger than a small refrigerator but smaller than a big refrigerator:D
