Passive radiators and phase

If a passive radiator responds to the rear pressure wave of the active woofer, why is it not out of phase?

[@halrichard1969]

You gave me more knowledge on the dynamics of driver and radiator relations. I didnt realize, as you said that there would be an extension of sound beyond the capabilities of the driver. That is amazing. I did see the Xmax of the Passives peak and travel beyond the actual driver curve. It had me thinking of why this was happening because the drive highpass curve was rapidly diving to nothing yet the pressure of the passives was still peaking up. Thank you.

[@elgingaragegym]

Great video Paul, and very illuminating. Again always appreciate your time and efforts in educating people to all things hi-fi.

[@dangerzone007]

Passive radiators change phase with frequency. They are designed to be in phase with the active driver around about the corner frequency. At some point below the box tuning frequency they are out of phase with the active woofer. Passive radiator designs are a bit slower than bass reflex.

[@duncan-rmi]

what I thought they were intended to do was dampen the resonant peak of the system (the large driver & the cabinet combined) & thereby extend the useful response of same by smoothing out the response.

[@dangerzone007]

@@duncan-rmi no just extend the bass.

[@xentiment6581]

@@duncan-rmi i might be wrong but i read somewhere that port is actually smoother and passive radiator falls off more dramatically

[@juliocesarpereira4325]

Thanks for your explanation. Very clear, easy to understand and helpful.

[@shipsahoy1793]

I have a decent pair of stereo speakers that are passive radiator, but I prefer an excellent pair of a “proper” acoustic suspension design, that I’ll take that any day over the passive radiator. That said, I’ll take either one of those, of which I own both, over a ported design any day; although I do have a pair of bookshelf speakers that are in fact ported. Not terrible, just need to be placed even more carefully than the other types. I just prefer a good full range acoustic suspension type of sound.

[@user-od9iz9cv1w]

Interesting. Never really understood. Appreciate the layman explanation.

[@arsimahmetaj6272]

Excellent at always 👌

[@RoderikvanReekum]

A fully closed speaker design is even better but it is rare these days in the affordable price range. Do not like bass ports that much because of the noise they make especially if the design is bad. Olso placing can be more difficult if the port is in the back. But hay, it is so manufacturers can get more bass out there speakers for cheap.(?)

[@marcse7en]

I'm a British 🇬🇧 person, and in 1979, I had a pair of Celestion Ditton 15XR Speakers with Auxiliary Bass Radiators (the ABR units had polystyrene / styrofoam as part of their construction). They were great speakers, with very satisfying bass! EDIT: There's a red light flashing on Paul's telephone! ... Perhaps he's got voicemail?

[@rollingtroll]

They are still great speakers today, especially the later model with the more modern tweeter. Honestly speakers haven't improved much in the last 50 odd years. Preferences have changed but there were great speakers in the mid 60's, there are great speakers now. That said, there's some amazing sounding cheap speakers out there these days. You didn't have that in the sixties.

[@marcse7en]

@@rollingtroll I agree! ... My current speakers are a pair of British 🇬🇧 Mordaunt Short Pageant from 1979, and they sound amazing!

[@waynemackie3113]

I have some old Kef C55 and C75s. They have passive radiators and they sound great. The bass just feels so much smoother than you get with a ported design and they seem to cope way better with being closer to walls

[@RoderikvanReekum]

Yes, I had some Kef carlton with passive radiators, great sound. Old English speakers can be great.

[@terrybeavan4264]

I also have a set of C55's I bought them new around 1989 and I absolutely love them! Interestingly the center cap in the passive radiator contains a weighted metal disc (don't even ask me how I know, it involves an incident with a misbehaving Marantz 1122DC and fortunately the damage was replaced under warranty!) I don't push them hard these days knowing from what I've read the tweeters have probably lost the ferrofluid that cools them and replacements are now likely impossible to get. I'd like to take the time to hear some more modern speakers but I can't imagine parting with these, to me they sound great and have nice clean detailed bass that goes very deep and I've never felt the need to supplement them with a subwoofer.

[@ubza1234]

If you play with a large slinky, ideally metal, that is to say, stretch out your arm horizontally with the slinky hanging down in front of you, and you then bounce it below the resonant frequency of the slinky, at the resonance of the slinky, and above the resonance of the frequency, and observe the relationship between the difference of input (your hand) and the output (the bottom of the slinky) you will learn a lot about how ports and passive radiator. Take note of phase and amplitude in particular. If you are holding a metal slinky, you may also notice the inertia of the slinky pulling on your hand more at resonance, then below or above resonance. It really is the easiest way to explain the different phenomena going on here ☺

[@user-yx9xm9ue1b]

I'm thinking that he is talking about the standing wave that builds inside the box at low frequency

[@ssgeek4515]

Woow never knew that. Resonant freq for the passive diaphragm 👍

[@sonusancti]

Thank you Paul and from your explanation, correct me if you care to, the ideal speaker would therefore be: a) Have a bass driver whose resonant frequency is below 20Hz; b) Have an enclosure that likewise takes box's resonant frequency below 20Hz This speaker should therefore give linear response down to 20Hz without need for ports or passive radiators.

[@paul8699]

Yes and this is why sealed boxes are considered the 'easiest' to design. They're very linear and hard to screw up. The problem being the box needs to be massive to avoid losing volume down low (Hofmann's Iron Law). So in a small box you need to use DSP, so most companies choose reflex boxes to have a more satisfying roll off. -a different Paul

[@robh9079]

My understanding is the box would have to be massive.

[@sonusancti]

@@paul8699 But wouldn't an open baffle eliminate much of the complexity as more manufacturers are doing?

[@johndough8115]

@@paul8699 I used to own a Phillips WOOX boombox that featured special Passive Radiators. You are correct in that at lower volume levels.. the bass isnt anything to note. Yet at mid to high volume levels... it was INCREDIBLE. HOWEVER... to solve this issue, Phillips included an EQ Toggle, that merely boosted the Bass frequency levels (similar to cranking the bass dial on an old Receiver). This doubled the "EXCITEMENT" levels of the Passives, at even the Lowest of volume levels. Of course, I always Crank my music... so I rarely used that EQ Toggle.

[@mkshffr4936]

Kind of. If the speaker is actually flat the the bass will be over emphasized due to the effects of the room. Interestingly the room gain slope is pretty close to the roll off slope in a sealed speaker.

[@bmosst]

Still curious - Why only 1 cycle? Where physically does delay come from? A certain travel distance from rear air to front air?

[@D800Lover]

It's a modified Helmholtz resonator. Not easy to explain unless you are steeped in this sort of thing.

[@SpyderTracks]

The more I learn about speakers the more I realise just how difficult it is to make a really good pair, the science behind it is mind boggling.

[@marmerg]

a good example I've seen used (not my idea ) is the similarity to a "slinky " , held by one end and shaken at different frequencies until you find the frequency where the bottom end becomes in phase with the top end ...yes there is a time delay, but at the right frequency , the top and bottom oscillate "in phase", all be it time delayed by one cycle . Only a visualization ,but an apt one for understanding P/R operation .

[@g.fortin3228]

Well. Still unclear, can't wrap my head around this one as the speakers I had were clearly moving the opposite of the radiators.. guess we need the man to clarify why this is. Older Polk models. 10B.

[@jasonbrindamour903]

Conspiracy theory: Chris is just simply a part of Paul's imagination...lol

[@sidesup8286]

His camera would have to have an active imagination too. Chris has been filmed & interviewed quite a few times.

[@artyfhartie2269]

Loudspeaker manufacturers need to think outside the box (pun intended) and design the crossover as a separate module which can be sold either separately or together with the loudspeakers. This will make it easier for consumers to repair or update the crossovers or even use different crossovers. The manufacturers could also put out new better ones. Audiophiles could power their loudspeakers drivers any way they choose. Crossover modules would just connect with RCA, coax or XLR cables to the speakers. The sky the limit.

[@sonusancti]

While I get the curiosity behind it, it wouldn't make business sense nor technical sense given the vast majority of none tech savvy music lovers. I'd much prefer to see full range drivers that will make crossovers obsolete, at least from 20Hz - 10KHz. HF only needs one capacitor.

[@robh9079]

At least some manufacturers are providing tweakable crossovers - i.e. level adjustments for the tweeter - so easy to do. Guess there is not a sound business model and/or demand - after all boxes and connectors are expensive, have a low WAF, and it wouldn't improve sound (at least any more than money spent elsewhere). - I am sure they would prefer you to upgrade in the form of a newer model too!

[@sonusancti]

@@robh9079 agree

[@artyfhartie2269]

@@robh9079 What I was saying is that a separate crossover module for each speaker allows the consumer many options. To choose her or his preferences in sound instead of one built in by the manufacturer and also to update to the latest technology. And also not having to depend on all this BS room equalizer software etc. The company also would have a new line of products to sell.

[@sidesup8286]

An outboard crossover would also take it out of the cabinet and free it from the degrading vibration of being inside a cabinet, where there is a literal mini earthquake going on from the output of the woofer.

[@rollingtroll]

Dear writer; Having heard the FR20, I can assure you; very, very different league from anything B&W ever made. Assuming you gor the rest of your rig up to snuff, you'll forget B&W exists all together really quickly :). Bass is very tight, very musical and very controlled sounding. It's rare to hear a bass this musical yet controlled. Usually lows that manage to be fast enough to properly follow a musical line, are overly dry and not very natural sounding, a bit boxy. The FR20 did a great job combining both. I personally prefer a slightly slow/sloppy bass over an overly dry/fast one if I had to choose, but the FR's prove you can have your cake and eat it too.

[@ryanschipp8513]

I heard the FR30's. Nothing special. Overpriced. Someone can get a pair of $10,000 Tower speakers from a reputable manufacturer and run dual subwoofers and match the performance if not better it.

[@user-od9iz9cv1w]

Good point. I heard them this weekend. To my ear they are very pleasant on a variety of music. I think people could enjoy them for years. Lot's of others at the show were more dramatic drawing attention to the bass vs sounding natural.

[@ryanschipp8513]

@@user-od9iz9cv1w I take it you have heard heard a Canton speaker...

[@rollingtroll]

@@user-od9iz9cv1w I am actually working on a video of the show. It of course won’t allow you to hear the way they sound but it will allow you to compare to other setups there. I personally like a slightly more “coloured” sound, retro if you will, a little laid back, but they still were easily top 3 of that show.

[@user-od9iz9cv1w]

@@rollingtroll I look forward to your video. To me the Gershwin Black Swan was the winner. Alsyvox and Acora pretty interesting. I only went for 90 mins and stayed to the big stuff in the conference floors. I've been many times as I live 10 mins away and know how challenging the Westin bedrooms are to produce decent sound.

[@sidesup8286]

Has there ever been a study to find out just how much delay before the ear can detect that there is a delay? If there is too much of a delay, would it sound weird? Just how weird and in what way? If you've ever seen the inside of a transmission line speaker cabinet, some of them look like a complex maze made for a rat. Making the bass wave make all those twist and turns inside the cabinet, to fool it into thinking it is a much bigger cabinet, before finding its way out of usually a rectangular port, has to involve some tardiness of the tunneled bass, compared to the bass coming directly out of the woofer. Yet transmission line bass speakers are known for having some of the tightest most coherent bass ever. I have experimented with making my own admittedly crude transmission line bass cabinets; and the results have always been surprisingly spectacular. Even before Vandersteen, Polk Audio and some others I assume were making speakers with passive radiators. I listened to a pair for years,. and the low bass didn't have quite the get up and go of the mid and upper bass, but as I improved my amplification, it was less and less noticeable and toward the end was nothing to complain about at all; in fact it was quite good bass. Too wide a cabinet and annoying diffraction effects though, prompted me to upgrade the 70s era Polks. The quite expensive high end speaker I upgraded to, ironically was just the opposite in the bass. It had a round port and the low bass had better definition than the mid bass. Does anyone remember Goetz speakers? That guy was a genius with crossovers. The sound was so seamless and fast. Of course back in the early 1980s, $1500 would probably translate to close to a $4,000 speaker today. Only very recently have I been able to match the dynamism of that speaker and it's bass deepness. It took finding vintage 94 db drivers, a great subwoofer and a much bigger listening room than I had before. If you occasionally hook up rear speakers and delay the sound by small fractions of a second, you can pretty realistically simulate a much bigger acoustic environment. Anything from a jazz club to a cathedral. Digital time delay units became a fad back in the 1970s and 1980s. Whether you liked the effect or not, they always improved the bass with more than just the two speakers playing/crossfiring in the room. It did adversely effect the focus of the main front channel though.

[@sudd3660]

try it yourself, if you have subwoofer play with the phase knob, hopefully you do it on the remote while playing music or tones. or do changes in dsp, delay the signal of main speakers or subwoofer, or midranges if you have more channels on the dsp. you are going to heard large changes across the board. less issues below 50hz i think, and if it is gradual even less.

[@johndough8115]

You wont notice the Bass on the Passives, until they are "Excited" enough. This can be done one of two ways: 1) Increase your volume levels 2) Use an EQ, and boost the Bass frequencies. I used to own a Phillips WOOX boom-box, that had special Passive Radiators in them. The stereo had a Special EQ mode toggle, that would boost the bass frequencies, so that even when you were playing the system at lower volume levels... the passives would be very "Excited". But since I typically play my music Loud as hell... I just used the Normal EQ setting, and cranked them to the max. The deep bass levels that those 6.5" drivers produced (via the passives) ...far surpassed my large Techniques 12" 3way house speakers. They also gave my Audiophile speakers ( EPI 100v ) a real challenge in the Bass output. But the EPIs produced a much more Accurate bass.. and the tweeters on the EPIs completely destroyed the upper and mids of the Phillips speakers. There was no notable "Phase" delay in the Phillips woox speakers, at all. You are far more likely to notice issues with the High Frequency drivers, than anything else. That said... I have a feeling that Transmission lines and Horn based speakers, are far more likely to suffer from such a thing. Personally, Ive never liked Ported speakers. The bass they produce sound Artificial, and "muddy"... and there is often also some Port noise distortions too. Ports can be "OK" at lower volume levels.. but once you reach mid to high volume levels.. you easily notice the "DRONING" artificial sounding bass sounds... as well as port noise issues. Also, I disagree about your statement about Transmission lines being the best bass. I picked up one of these Bose wave radios at the thrift shop for cheap... for kicks and giggles. The system uses a long snaking tube, just like transmission systems... and it suffers the same issues as ported speakers. Sounds "OK" at very low volume levels. But once you get to mid volume levels... everything get Droning and Artificial sounding. It gets really bad, at max volume levels.

[@sidesup8286]

I don't think I'd make a blanket statement on transmission line loudspeakers based on the Bose Wave Radio. I cannot say I've heard transmission line speakers play at 90 db, but companies like IMF and others who were famous for making transmission line speakers, were known for their awesome bass response. Maybe the IMF Reference Standard Mk. IV & V loudspeaker was THE best overall speaker on the market for near a decade. I did borrow an ascertation from Stereophile saying transmission line speakers have the best bass definition. I think the then editor John Atkinson made that comment; and based on my experience I adopted that as my belief. It can be said with certainty that a well done transmission line speakee can have amazing bass definition and extension. Talking about cheap stuff like the Bose Wave Radio; I recently noticed some cheap vintage Sony speakers which had plaatic cabinets, but which also had Kevlar drivers, which are a bit of an exotic material in a cheap speaker made of plastic. Kevlar is a great material for clean; but it's supposed to have a breakup mode at a certain frequency. Because of Kevlar, some really cheap speakers had virtually 5 grand speaker midrange purity. But there were other problems with speakers like that.

[@johndough8115]

@@sidesup8286 The technology that Bose used for the Wave Radio, and its later "Acoustimass" box driver... is the same physics principles behind a stand-alone Transmission speaker, as far as I can tell. Sure, the enclosure is likely made of Plastic.. but that would never really be notable. Borrowing someones Quotes, and forming an Opinion based on that and that alone... is pretty Foolish. Especially since a lot of the dudes that talk the most... tend to have a corrupt Agenda to push. In the Case of BOSE... their Agenda is making ECO speakers, that consume less overall power.. as they are part of the ECO-Nazi radical cultists. They used the Cheapest drivers, and use various "Trickery" to get the best possible sound... out of the worst low-power drivers. Even to that end, they dont sound very good... especially compared to other speakers that are much cheaper... (that can also play much louder, and have far more Dynamic range / Frequency Response). Ive listened to speakers from all sort of brands, using all sorts of technologies. Its only from listening to a certain type of speaker, that I form my OWN educated opinions / experiences from (and this is how it always SHOULD be). Of course... there will always be limitations. For example, Ive heard some lower spec "Planar" speakers... and I thought they sounded like Trash. That said... Im sure there are plenty of high quality planar's, that would change my low opinion of them. (Though, from what Ive discerned from descriptions of others... they may be fantastically accurate, but they have an extremely narrow soundstage... and thats a NO GO for me) As for the cheap Sonys with Kevlar cones... Kevlar was likely only used, for Aesthetics and Misguided Hype. Their woofers on their low spec systems are nowhere near Audiophile grade.... so it almost doesnt matter WHAT material they used for the cone... because it will always sound like trash, no matter what cone material they chose. I found this out.. when I had some foam Rot on the 6.5" woofers of my Phillips Woox speakers. I tried to replace them with some sony boombox speakers (which I believe actually had the kevlar cones)... and they didnt even come CLOSE to the original drivers, in accurate sound reproduction, in excursion potentials, nor in any other way. The Woox drivers were simply FAR superior Driver designs, bordering on Audiophile grade level of Quality... And that was pretty much unheard of, in cheaper consumer level equipment. (and that little woox system DESTROYED all of the Bose equipment Ive listed... and much more that I didnt list) The reason why the ECO Radicals pushed the Industry towards Ported speakers... is because Sealed speakers require more Power to overcome the additional Air-Pressures involved. The woofers in an audiophile grade sealed speaker, use much stronger Magnets, and most stronger Coils. This added Strength and Power... produces FAR superior Cone acceleration and control. .. and that equates to almost ZERO distortion levels, even at max volume capabilities. ECO Radicals dont care if your music sounds like CRAP... so long as they are getting you to use lower power levels at the AMP. This is also why they started Compressing all of the music to HELL, in the 90s, and beyond. CDs in the 80s have FAR more dynamic range, and detail, than anything produced in the 90s and beyond. Its utterly SICKENING.

[@Fastvoice]

There are studies like that. You may e. g. google "The Human Ear Detects Half a Millisecond Delay in Sound" - done by Acoustics researchers at Aalto University.

[@adv.rohitl.jbrasdesa2402]

Paul please spend your time checking the quality issues with your power regenerators. All talk and no quality psaudio

[@sudd3660]

all the description of a passive radiator design sounds like a sound quality compromise, some extra bass benefits with some drawbacks. i have dsp gear so i am not a customer of passive radiator or ports.s i can see the use of passive radiator design for those with a more common stereo, more bass extension is worth the tradeoff in that case.

[@PSA78]

There's usually less tradeoff with a passive radiator (or port) than DSP.

[@robh9079]

My understanding is a radiator has distinct advantages over a port and should be seen as a better alternative (though more costly).

[@sudd3660]

@@PSA78 then to do dsp as usually done, get a nice dsp unit, like the minidsp SHD studio for example.

[@PSA78]

@@sudd3660 I'm not sure what you meant exactly, but the quality of the DSP isn't the issue with trying to compensate for something the woofer/box wasn't designed for.

[@sudd3660]

@@PSA78 i small sealed box performs great with dsp, not huge drawback with that, box does not fight against it, and the woofer plays what it is feed. where are the problem?

[@villageroma]

No it's not out of fase. The negative wave of a sub cone gets inverted internally pushing a delayed positive on the passive radiator reaching a delayed in fase wave. Problem is that this is no hi-fi but a boom box. As a musician neither I or any of my colleagues likes this effect. It tricks your brain but it messes up with music timing and weight. That may work in a open space but in room forget it. I remember that in the 60's and 70's brands like Phillips were advertising no boom box in their products. 😂

[@Paulmcgowanpsaudio]

You're correct that many (most) PR implementations are poorly done. Where you're incorrect is by suggesting every implementation is like that. Certainly, we would never put anything on our products that sounded as you describe. That's nuts. Truth is, properly done, a PR is great. Using, as we do, a low distortion low coloration woofer, in combination with a properly designed PR sonically beats a servo woofer system that was once state of the art. The danger in these comments is always the sweeping hand proclamations. Just because boom boxes may use a woofer, or a passive radiator doesn't therefore condemn other products with different goals from employing them to great advantage.

[@navinadv]

@@Paulmcgowanpsaudioin a system where there are multiple Passive Radiators can we spread the resonance of these PRs by making the PRs with different cone mass? So if your system has 4 PRs you could technically have 2 PRs resonating at 25Hz and 2 at 20Hz making the response less “pesky”? Theoretically you could do the same with ports by having ports of different length and/or diameter (which determines the air mass). Is there any limitation on the size of the PRs with respect to the size of the “active” woofer? For example could we use a 8” PR with a 5.5” woofer?

[@villageroma]

@@Paulmcgowanpsaudio boom box ain't a product but is an effect. It have to do with resonance as you explained in your video and hi-fi has always tried to eliminate that effect especially that from a cabinet. The results of this effect has no trace in the original recording and it's a coloration (read distortion) completely made by adopting PR equipment no matter how good or bad has been implemented. Now you make and sell speakers to purposely deliver this added effect of distortion. Again this is not what hi-fi is supposed to be especially when low frequencies can't keep up at timing and rhythm within them self and especially with the rest of frequencies spectrum. The only resonances allowed in hi-fi should be the ones naturally coming from the instruments at the time of recording. Boom box effect dyed some 60 years ago but somehow managed to come back to us from afterlife.

[@ryanschipp8513]

​@@PaulmcgowanpsaudioPaul, a pair of 10k Canton speakers with dual REL subs will match the sonics of your FR20's and FR30's for a fraction of the price....and they are handmade in Germany (over 50 years of speaker engineering). Why are your made in China speakers so expensive compared to the set up I mention?

[@vladimiravidon4576]

@@ryanschipp8513 iPhone. Last time we used the phone made domestically, it had a rotary dial.

[@KarelSmout]

This time I am afraid you're wrong. They are out of fase - but they are also out of place. The 'common misconception' at 6:20 is correct: if the air moves in, the radiator cone moves out. And so they should! Thus the large basis waves are in sync with the room. Look at it as a car door. If you slam a door, wind gets out somewhere. The last door closes lessen easy because of the air trappen in the car. Passieve radiator gives breathing room to the conus, and adds to the motion itself.

[@johndough8115]

Passives have "weights" that you add on to them (internally). The weight is what prevents them from moving at a frequency that isnt low enough. When the correct frequency is hit, the mass is "Excited", and moves in accordance with that frequency and mass. Its not as simple as you have described.

[@Gary_Hun]

1:24 - kzbin.infoMnfhuWhH8uk

[@digggerrjones7345]

"A port, which is just a hole in a speaker" should tell viewers all they need to know.

[@ryanschipp8513]

Paul, come clean. You have mentioned you are "trying" to get Chris on camera multiple times. Literally multiple times. Just admit it, he'd rather not be a part of your channel. It's just not his thing. End of story.

[@graxjpg]

you cant say whether or not hed care to be a part of the channel, but its obvious that he isnt comfortable being on camera from his appearances.

[@ryanschipp8513]

@@graxjpg yes it's one or the other but Paul keeps on talking about getting him on and it's just ridiculous at this point for him to keep on mentioning it when it's never going to happen

[@user-od9iz9cv1w]

@@ryanschipp8513 He and Paul did a long video with Chris explaining his design choices and testing process in the warehouse. I think it was with the launch of the 20s or maybe the 10. Just watch it and then there is not much else for him to talk about repeating material over and over. He is an engineer and ok on camera, but it is not his field of dreams as it is with Paul.

[@ryanschipp8513]

@@user-od9iz9cv1w I know all about that. What I'm bringing up is Paul repeatedly saying how he's going to bring Chris on again. He's beating a dead horse . Its just silly for him to continue to keep on bringing it up when we all know it's never going to happen. That is my focus of my comment .

[@graxjpg]

@@ryanschipp8513 hes been answering the same 50 questions for years… if hes making an effort to get chris on camera without pressuring him or making him uncomfortable, it might take a special kind of question or scenario to get chris on camera and if paul is actively working on convincing chris i dont see the problem in mentioning it.