How do passive radiators work?

They operate very much like a port in that they are tuned to vibrate at and around a specific frequency. One advantage over a port is that they take up much less space. Where a deeply tuned port need a lot of length, the passive driver just needs weight added to tune it. That way you can achieve a deep tune using a fairly small box.

Personally I like passive radiators. IMO they have the some of the benefits and characteristics of both a sealed and a ported speaker. From my experience if the active driver and passive radiators are tuned correctly you get that punch in the chest feeling when the bass hits hard. They have the low bass extention and efficiency of a ported sub but they have the quickness and punch of a sealed sub.

They effectively work exactly as a port would. The advantage is (as mojomike explained) that they take up less space. This can be crucial in a small enclosure or when tuning low - in a small box you may not have room for a port - to tune low requires a longer port which may not be feasable. Yes you could make the port a smaller area so the length wouldn't be a problem but then you run into problems with port compression and chuffing which is the other big advantage - they don't chuff. However, although they won't chuff/compress like a port they do have mechanical limits that will compress and bottom like a driver so it's not all a free lunch. The main reason they aren't used in many designs is generally a port will be just as effective for basically no extra cost (or very little cost) whereas PR's can add significantly to the cost.

There is nothing inherent about a passive radiator sub design that makes it any more like a sealed sub than like a ported sub. A sub with a passive radiator is neither inherently quicker or punchier than a sub with a port.

Like I said it was that way with my experience. Maybe the ported speakers I listened to were crap and the ones with passive radiators were good ones. Depending how much weight and how tight you have the passive radiators tuned makes them tighter(puchy) or boomy/muddy(loose). I'm not trying to argue, this was just what I noticed.

No, you're right actually. Given we're talking two speakers of equal quality, the one with passive radiator vs open tuned port would keep cone movement tighter.

These radiators are passive, but they are nowhere near being open air like a ported speaker. They aren't just tuned properly in size and stiffness, their passiveness has to be tuned just right to keep the air management so that they push out when the driver retracts, and vise versa, while still being passive vs sealed. No matter how you cut it that means tighter driver cone management.

Definitive Technology, one of the best speaker makers in a small home theater size, has designed their latest ProCinema 600 series with passive radiators in all the satellites and the sub. Everyone that's reviewed them be it customers or review sites/magazines have noticed better, fuller sound from this new design over the previous 60 series, and the passive radiators are the main design change.

Not exactly correct either, yes given the same power the active drivers' excursion will be less in most cases but this is not due to better "control" but due to efficiency loss around tuning due to the losses associated with the stiffness of the passive radiators suspension.

The main reason passive radiator designs often sound more like sealed, is due to the fact that in almost every case passive radiators are used to give a lower tuning than would otherwise be possible, and it is this lower tuning that gives it that sealed "sound". This is because the farther above the tuning frequency the more it behaves like a sealed enclosure, so if your tuning is low enough by the time you get into the mid/upper bass frequencies, where our ears are more sensitive to distortion and ringing, it is essentially acting sealed and will sound like sealed. There are many other factors involved in "sound quality" and "punch" than simply ported/passive/sealed, properly designed they can all sound very good, also badly designed can make any alignment sound bad. Sealed is the easiest to get "right" and is why often has the distinction of being the best. Passive radiator is also reasonably easy to get "right", ported can be trickier as it can be physically difficult to design the enclosure to be "right" and work from a construction standpoint, and often compromises are made in the design to make it buildable, however it has the most potential to have equal sound quality to the other alignments with the most low end efficiency, and therefore provide the most for the money.

First off I said quality, not power. One cannot equate power with quality of construction. Secondly I was referring to the dampening of the cone, not merely how much excursion it has. The extent of excursion has nothing to do with how precisely it's forward and back movement is controlled. That kind of control is never going to be possible with a mere port design. In port design cone control is specifically up to the driver design, there's no assistance from the enclosure.
Again, when we're talking "sealed" sound, we're talking cone control, vs flapping uncontrollably in an open enclosure. Let's not confuse frequency of tuning with control of the enclosure's gas management, the two are entirely different things.

I'll skip quoting any part of your last paragraph and just say that your having said many factors attribute to sound quality is the obvious. Where you miss the obvious however and somewhat contradict yourself is where you say ports and the proper tuning and fitting of them is the hardest, yet the best bang for the buck.

Indeed port tuning is not simple, nor is even port fitting in some cabinets. This is why you see SO many crappy sounding speakers that just have little holes and short tubes in them, that offer ever so slightly lower frequency, at the expense of sound quality. I don't call that best bang for buck. In reality it's the illusion of bang for buck a lot of consumers become victims of.

I have spoken with some pretty good subwoofer cabinet designers and I do know a bit about gas management in speaker cabinets. The Definitive Technology tech I spoke to also describes the benefits and function of passive radiators pretty much the same as I have here. Sorry, but I have to disagree with you.

^^^ I know one pretty good subwoofer cabinet designer you've spoken to--at least electronically--and he posted just above you.

http://www.funkaudio.ca/Custom_Gallery.html

Doesn't mean a whole lot really. "Pretty good" is relative to one's success, and I don't even see anything but over priced ported enclosures, nor is it as well known a brand as they make it out to be. Looks to be still in the start up stage. You Google that name and you get one of 3 or 4 sites, including one that redirects you.

The vague and even contradictory terms he uses leaves me even more skeptical. In reality the internet is full of people trying to use forums to launch their business. Doesn't mean they succeed at it, and if he was as successful as he makes it sound, he wouldn't need to be glomming onto forums to get customers.

They make light of "big box stores", yet contradict that resistance to volume sales by trying to make themselves sound like they have a vast global consumer base. Yet where is their name seen even in smaller volume high end audio stores? None that I've seen in the US. Sounds a lot like snake oil to me.

You know when you see someone talk as if they prioritize basic build quality of speakers using cabinet material like aluminum, it's more about a gimmicky fashion statement than bang for the buck sound quality. How he could even mention bang for the buck in his post above is a bit absurd really.

^^^

do a bit of browsing around in the subwoofer forum... your eyes may be opened a bit...

I have two subs with passive radiators. By my experience and everything reliable I've read they are no different (apart from losses with the passive radiator) from ported except not requiring a bulky port taking up space in the enclosure.

I understand that the radiator is tuned to some frequency, but what is making those frequencies. If the woofer is capable of making those frequencies then why bother with a radiator. So my question is what is driving the radiator. Is it still the woofer but the woofer is not capable of high output at those low frequencies and so the radiator adds to the output?

Its called "passive" for a reason. It substitutes the mass of a cone for the mass of air in a tuned vent.

I get all that but where is the frequency coming from that causes it to vibrate? Is it still produced by the woofer and the radiator just adds to the low output of the woofer as it is tuned to resonate at that frequency?

BTW my earlier question was not in response to your post. If was a general question.

I guess I get it. My assumption was indeed correct.

http://www.humanspeakers.com/whatis/PR.htm

Mupi,

The passive radiator moves because of air pressure fluctuations within the sealed enclosure, like a diaphragm, caused by the movements of the active driver cone (the one with a magnet and powered).
Think how pressures within the speaker enclosure vary and differ while operating a sealed or ported cabinet if you were to measure with a very sensitive device, capable of measuring fractions of a pound of pressure, capable of measuring say 1/25th of 1 psig.

Think of it this way. At first, high fidelity speakers were sealed, then came along the bright idea to port the cabinet to boost acoustic output (generate sound from both surfaces of the driver cone. Passive radiators do similar, but with a slightly different twist (some degree of dampening possible). Vented or PR rely upon driver cone rear surface movements/radiating area to generate additional sound, the need to create more sound output from a given power level and cone radiating area. Sealed generate sound from the front face of the driver cone, vented and PR rely upon or "play" both sides of the driver cone to create output. Hence why ported subs "sound" more dramatic. And reason why a ported or PR cabinet can never be as sonically accurate as a sealed. Ported or PR rely upon "ringing" or secondary movements to generate additional sound. Quantity at the cost of accuracy. You want highly accurate bass output, get sealed enclosure driver surface area, multiple units, multiple drivers, more amplification power.
Some people don't care for sealed sub sound characteristics, they prefer exaggerated versus accurate. They want more BOOM, it impresses family and friends, see my room vibrate wildly.

Not entirely correct. I assure you my subs don't "ring." There is much snake oil in the discussion of what the benefits of sealed subs are. Its been discussed ad nauseum.

I hope you realize that you you are arguing with a guy (Nathan) who builds subs that leave anything Deftech has ever produced in the dust. Deftech subs are middle-of-the-road at best. They never meet their ridiculous, exaggerated, over the top specifications. Nathan is the guy than many hard-core enthusiasts turn to when they get bored with certain so-so performing subs such as Deftechs. If you want to keep that argument going, you're just going to wind up looking silly.

polizzo,

you haven't heard a good quality ported sub yet with that ^ narrative.

Take a look at the blind 2012 test linked in my sig. We had two ported subs and at least half mistaked them for sealed in both cases. Boomy and inaccurate they are not.

too late...

When I decided to upgrade a couple of years ago I had pretty much made up my mind to go sealed. When I spoke to John over at Acoustic Elegance he asked me a bunch of questions about my room and listening habits and steered me to the PR design instead as a better bang for the buck choice. Fewer cabinets for the same or better low end output as well. He indicated that sound quality degradation with the PR design really isn't a practical concern. I listen to a lot of music and can say my PR subs (2 P1512's) are as good if not better than my Empire for sound quality.

I was not talking about power, I simply mentioned "given the same power". I never said anything about quality of construction. If you feel passive radiators offer better "control", above tuning, you simply do not know how a Helmholtz resonator works. The only time the passive radiators suspension affects the "dampening" of the active driver is below tuning, and the amplification system should be filtering out frequencies below tuning anyway.


If you think ports allow the driver to be "flapping uncontrollably", this only shows again you do not understand how a port works.


Not sure how this is a contradiction, ports can offer the best performance for the least cost, and sound just as good as passive radiators, however this is only when the port size/tuning/execution, is not compromised to make it physically work. In some designs ports simply cannot do the job required and this is when passive radiators become the best solution, not because of sound quality, but to allow an uncompromised Helmholtz resonator design. I have done many passive radiator designs and the goal is always to have the passive radiator behave as much like a port as possible and only have enough supension to provide support to the weights and have good longevity. The softer the suspension can be the better.


Examples of compromised designs, and very often intentionally so to increase the perceived bang for the buck(output/boom). When I say "bang for the buck" I am not talking about sheer output, but about value for the dollar.


None of the ported products on our old site are currently avaiable. We are in no way start up; we have been building custom speakers for over 12 years. We have only just recently changed our name and are revamping our entire product line, too keep up with our growth, and market changes. We do not claim to be a "large" company but we are well established. We are internet direct sales only, so you will not see our brand in stores, we do have OEM products (that will remain nameless) in stores. We have sold products "worldwide"; Hong Kong, Austria, Italy, Australia, Finland, to name a few.

There are no gimmicks, aluminum has its place but is far from "bang for the buck" option. When I said bang for the buck I was simply talking about the fact that ported design can offer the best bang for the buck.

Wow.

Archaea, I have read pretty much every word in your GTG/blind test, before execution and as it has evolved post meeting. It is and was very informative. And your right, I have not heard in person really good ported subs. I know your hands on (and ears on) experience way way outweighs mine, probably 90% of us here on the forum.

Nathan, well done on your rebuttal. That post was attacking and you handled it well with both knowledge and tact.

Hehe. I like the "appeal-to-authority" play, it just doesn't work here:

http://www.audioholics.com/reviews/s...oofers/fw-12.x

Here is the summary from the Audiohaulics review of just one of Nathan's offerings (not his more famous 15.3 or 18.3 sub designs):

"The Funkywaves FW 12.X Ported 12" subwoofer is a beautifully crafted piece of furniture. It must be said here, measurements alone do not adequately explain the unique sound of this sub. The tonal character is not matched by any of the other shootout entrants. It is a true subwoofer, offering flat performance all the way down to 20 Hz without any electronic equalization whatsoever. This product is, in a nutshell, very old school in its approach to making a small box go down to 20 Hz. It does so, not by any electronic signal manipulation, but by good old fashioned mass loading."

The first point in the "pros" column:

"Unsurpassed Cabinet workmanship & Aesthetics."

For grins, I wandered into a Magnolia last night and looked at a few def-tech offerings--and the prices they were charging--and got a good laugh at the "quality" enclosures their subs provided.

When you are done here, you might want to head over to the speaker forum and take a few cheap shots and Dennis Murphy and Jim Salk. That might go over just as well.

Learning the engineering principles behind how speakers actually work would be of far more benefit to you than merely regurgitating Deaf Tech's advertising spiel and believing that you actually understand the difference.

Hi Def Fan - you may be a fan, but you know absolutely nothing about HiFi, and even less about accurate reading. you are a diminutive and daft excuse for an educated audio authority. now im going to cut you down. where is your thriving speaker company's website? how many systems have you built from scratch? did you design and build your own divers, amplifiers, and enclosures? did you do all the raw math, cnc machining, cutting, soldering, design each cross-over, then finish the system with your bare hands? can you show us some credentials, other than regurgitating some mishigas from a second rate company? do you own an elite, world class company of any kind? do you employ multiple persons and contribute anything to the economic recovery that our community needs (mine and all the people that work for funk audio)? please do not insult audiophiles with better taste than you by voicing your future shop opinion here, let alone attack a company that is a icon of honesty and work ethic in my community. and for the record, funk audio's gear is pro audio and would retail for approximately double in any store, this is because the math says so, i build companies for a living, ergo, i know. this is not some empty opinion of a dozy twit. if you think that they are overpriced now, just wait, he just might charge what they are worth one day.

Funk Audio - good job, and keep that cool.

everyone else - nathan funk is a friend of mine, but as a business owner and a person he is neither belligerent or offensive. but i am (the profile pic on audioholics should be a hint). and to anyone who buys a funk system, you are getting a smoking deal every time because his prices are way too low for what the products are. again, because the math says so.

wonder if "hi def" is gonna come back and take his beating like a man?