Lunch with Paul: Servo woofers
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- čas přidán 13. 10. 2020
- When PS Audio began their long-awaited loudspeaker project it was with Arnie Nudell and servo woofers. After an audio shootout PS has abandoned servo woofers in favor of Chris Brunhaver's design. Find out why.
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Very interesting! What a professional Chris is
I wish there was more of this on youtube. I really enjoy advanced speaker design talks. Finding info on stuff like transducer design feels almost impossible.
You may like GR-Research here on youtube.
@@repawnd1 GR Research is very good, but Chris gets the nod. Lol There's something about a southern accent which doesn't inspire confidence.
Just kidding. But it's a bias I notice. "Frontier accents" are fine and sound very competent, like how Tommy Lee Jones sounds. But anytime there's too much twang I start worrying about their educational acumen.
Don't blame me entirely. In media and movies, southern accents were never portrayed unless to ridicule. They all attempted to have a neutral accent or would adopt a Mid Atlantic accent to sound posh and sophisticated.
This is why Paul is a successful business person. He is willing to listen to sound advice. Probably why we have not seen his AN speakers. I got a chance last October to meet Paul, listen to the AN prototype speakers and met Chris. I was very impressed with the whole thing. Chris was a gentleman, Paul as well. The speakers were very nice, but then we listened to the IRS v and it was not there yet. I commend PS for their determined, never compromise mentality.
My thirty year old Velodyne subwoofer hasn't farted yet. And I feed it plenty of roughage.
Hey Jeff. Funny one right there! Agreed, I don't believe I will through out the servo system just yet. Still loving my 1995 F-1500-R subwoofer (O: Musical yes, for high impact movies, not so much..
Thanks for the summary. I started working with motional feedback (servo) systems back in 1979. Back then, the low frequency drivers' suspension and motors were so non-linear that acceleration feedback made large reductions in odd order distortion. Today, LF drivers are much better and the benefits of motional feedback with regard to distortion reduction are much smaller. However, I think there are still instances where motional feedback makes sense. One is increasing bass extension in systems employing smaller LF driver(s). Another is for reference or test LF systems where minimum distortion and phase shift (group delay) is desired/required.
I somehow get an ever stronger impression that Chris and Darren are kind of becoming the dynamic duo at PS audio, even though they work on quite different stuff - it's a joy to listen to both of them.
Paul, Darren, and Chris will soon be spotted donning capes and wearing their underwear on the outside.
I like this man, Paul. He comes across more as a "sound-system" tech.
He might be a great fit to lead a design project. His knowledge seems encyclopedic and broad based. It takes passion to keep up with all design aspects and the tech throughout the years. Sometimes post grad engineers are too specialized and they overlook the big picture.
JL Audio and Rels have something good going on with their subwoofers!
Really liking these lunch episodes.
One of your best vids ... thanks Chris & Paul
Love these shows thanks for sharing paul 👍
I learned a lot. Chris is a fun dude.
Thank you cris.:)
This video was great, but it needs a deep dive where each point can be fully unpacked, explained and examples provided. Let Chris have some time with this and make another more detailed and presented video. Thank you and Thumbs up!
I am sure that Chris, as a musician and Bass instrumentalist, is very competent to judge the performance of Bass reproduction.
We are waiting for your newly developed sound producing equipment, certainly very well tested during this design phase.
I don't know, I still have the older Genesis 2's and the servo bass towers deliver phenomenal bass. I have never heard any negative artifacts.
But pre-distortion technology did take off, there’s plenty of products offering distorted audio signals at your local A/V store
:) That's for sure!!
Sounds like audio snobbery 😂
I think this whole discussion needs to be qualified by the servo technology Chris has leanings against, there are more than a few implementations of this technology, some better than others.
Regardless of their position, I'm keeping my Rythmik L12.
Servo woofer, aka Philips MFB, those guys at Philips physics lab in Eindhoven where Way ahead of the time!!!
Still running their first model as a subwoofer for my tv.
Over 40 years old now.
@@andrepost7571 a MFB 521 loudspeaker? Or 544?
The Muse 18 subwoofer I've had for years seems to my ears to integrate well and having very low bass that is very quick and tight. I've been tempted to upgrade to a servo sub but after this discussion maybe not
Compression of speakers is also because the woofer voicecoil is moving outside the magnetic field, and thus will not have a magnetic field to contract to when the current keeps rising.
So a big Xlinear of the woofer will allow higher linear output, but also weight of woofer and voicecoil is important. And together with this the temperature of the voice oil need to be kept low. Otherwise it will alter the resistance.
Together with this is the passive filter also very important.
Perhaps Chris can answer as well. If I'm understanding you, the voice coil moving outside the magnetic field isn't compression, ... it's simply operating into the non-linear BL region.
You're right about the moving mass (weight of the V.C. and the cone), it's important ... as a increased moving mass lowers both sensitivity and resonant freq.
That said, it's ALL important!
@@FOH3663 indeed maybe Chris can elaborate on this topi, but I think the non linear BL field will thus generate not linear sound pressure even when more energy is put into the voice coil, so I think compression and distortion will occur in that case.
The ideal driver will generate linear more sound pressure if more power is applied. It should be linear for 1 W till 1000w. Specially when transients occur and music is played on a louder level. For instance playing piano music on a level that would match a real piano on your room. It takes a lot of power and will easily need >200 watt. (I tried this in my own living room) the peaks measured where 215watt max spl at listening position was 90dB(a)
Now I understand why I don't like servo woofers. My theory on deep bass; if you can see the woofer moving, it's not big enough.
I think servos are okay for open baffle subs since they suffer from over-shoot and low damping. Otherwise, if you're getting distortion, get a more powerful sub or add more to your system so you don't have to overdrive it.
And that's why horn loading works so well - you're not driving the woofer diaphragm to distortion in order to achieve adequate SPL's. Tom Danley certainly has it figured out.
What new woofer did you use when you rebuilt the IRS towers?
Paul, to honour Arnie, put active servos in your speakers not to assist the woofers but to move the speakers automatically around the room or deploy accoustic absorbers or deflectors to tune itself according to its environment.
There's no honoring anyone to include old tech if new tech and methods have moved on.
Did you not get my joke / technological advancement? Your speaker's would be like R2D2s moving around your house to place their speakers in the optimal position for the presented sound content.
What's old can become new again. For example Electric cars.
If you're a hammer every problem is a nail. If you're a servomaniac then every problem can be solved best by using servo systems. The posting that I found most interesting was Bascom King's explanation of the servo system for the Infinity IRS. The first thing to do if you are going to install a servo system is to optimize the open loop design of the system. This was not done for Infinity IRS with what turned out to be less than the best quality woofers and a system resonance frequency of 60 hz. This was much too high and could have been far better. Another problem was pushing the servo to its limits at 100 hz cutoff but the IMIMs even in the quantity he used them couldn't reach that low and the result amazingly was according to Paul up to 100% THD. This is inexcusable in any speaker system at any price. Why didn't he add a lower midrange or as he called it a midbass coupler as he did in IRS Beta? That would have solved the THD problem completely.
My experience and my theoretical analysis agree that the best design I've encountered is the optimized acoustic suspension design. Since its inventor and those who worked with him and for him didn't fully understand how it worked they had to optimize it using trial and error and they succeeded as confirmed by their measurements and what they heard. From Wikipedia
"The AR-1 set new standards of low-frequency performance and low distortion that were unsurpassed for many years and some of the best loudspeakers available fifty-two years later continue to use the acoustic suspension principle for highest quality, low distortion bass reproduction." "The disadvantage of this arrangement is low efficiency. Since the restoring force is large with a large woofer in a small cabinet, the cone must be massive to keep the resonant frequency in the required low bass region."
My understanding of it came from the fact that the enclosure filled with fibrous stuffing controlled the damping factor by providing an enormous surface area that the woofer has to push and pull air between. This frictional loss is proportional to the velocity of the air, the surface area of the fibers, and the coefficient of friction of the fibers to the movement of air. This then puts the entire picture together for Newton's second law of motion applied to forced oscillation which describes all woofer/enclosure systems. The advantage this system has over all other systems is that the damping factor b and the spring constant k are independent of frequency and amplitude. Another advantage is that the restoring force which is mostly air pressure is applied uniformly over the cone which eliminates both radial and circumferential differences in force that tend to twist and shear the cone into harmonic distortion modes. The cone itself is much heavier of necessity and therefore inherently much stronger than light cones of the same diameter typically used today.
Great post, very informative and a lot to chew on.
Are there any acoustic suspension designs you can think of being designed and sold today? Direct order like NHT might still offer something. Other than that, I'm drawing a blank.
It appears most all the speaker companies are going after bass extension by any means necessary>>> ports and ocassionaly passive radiators. And it bores me to tears, and I'm opposed to it in principle (not so much in practice). Ported speakers can sound great, but I don't like the freqiency peaks and phase issues of using such a design.
@@thunderpooch Sorry but I have no idea. I haven't shopped for speakers in decades, even used ones. Careful, not all closed box speakers are acoustic suspension speakers. For example as far as I can tell variants of BBC Ls 3/5a and Harbeth P3ESR are not. Some subwoofers might be. I just don't know.
@@markfischer3626 I am aware, and am glad you provided that clarification since many people aren't aware that not all sealed speakers are acoustic suspension.
It would be nice to find a few and hear them.
Rel are not using servo in their very musical subs.
@Art DIY I heard it was an accelerometer attached to the sub cone. I believe Paul did a video on this before about how to control subs and the accelerometer was the better way
@Art DIY an accelerometer is not a servo, an accelerometer is normally found on chips. From the articles I have read most high end subs have some form of accelerometer tech.
I have a Velodyne 12" sub. It does not have a servo (as far as I know) but damn they do a good job at decreasing distortion. Never heard it made a bad sound even at really high levels when listening to music with alot of bass or even when watching movies with insane bass explotions etc :O But it does not limit the way you mention here so I guess that was more a thing on older Velodyne subs?
Heard some great Velodyne subs. Remember I fell in love with the DD18 but could never afford it. Only 18" I have heard that could play nice with even small 5" speakers.
Paul, good work on building your design team with these young and knowledgeable audio thinkers (Darren & Chris)!! I'd like to hear Chris's thoughts on low frequency room correction systems that are on some of the mid & higher end subs and his preference for connecting and integrating sub(s) into a two channel system, speaker level, line level, or other. High & low pass filtering?
can you please make a video explaining in detail what a servo is, its parts and how it works? thanks very much.
i have a pair of 3a master control speakers with servo woofers and a ribbon tweet from early 80s. one of the best sounding speakers ive heard. sadly the electronis failed. the person i hired to fix them was more of a failure.
When are your speakers coming Paul, you’ve been promising a long time now? We’ve heard lots of critical opinions of design elements of others. Sort of sets the bar really high for your company. Hope to hear some speakers of yours sometime.
So. Are field coils the answer?
What about the Rythmic F-18? Why is it everyone raves about these subs and how they have such high sound quality compared to the majority of other subs? I have two on order what is your experience with these subwoofers?
What up fellas? I recently ran into a video of a JBL Paragon speaker and wow wee that thing is cool looking. What do you think of this speaker? Is it worth the $16k it’s currently selling for (someone on Facebook marketplace has one)??? Thanks.
Servos even when implemented well add complexity potential for repair as well. Modern drivers -ie improved cone materials magnets spiders etc - drive distortion down-why use a complex server when u can allocate your budget toward these quality basic parts of a sub?
becasue your amp doesn't have to be as large and you can save that money back!
Absolutely agree. Intrinsically good designs where box tuning (air suspension) controls woofer excursion is the way to go. Just ask Boeing about 737-max to learn how software control of an intrinsically bad design is NOT the way to go. Phase information in bass is important too. Building a really good transducer will ALWAYS sound better than band aids on cheaper designs. Totally agree! Intrinsically good design with tight tolerance engineering Trumps complex correction software on a cheap sloppy transducer. ATC speakers use the old school transducer design approach and it still works.
Car audio phoenix gold, made a concept sound quality subwoofer named the cyclone. You guys should look it up, its like nothing ever seen in a speaker. Its more of an low frequency “airpump”. Responsive from 11hz up
This is a Tom Danley invention and we may discuss rotary woofers or some of his other inventions another time. Definitely a huge fan of his work.
@@cbrunhaver thank you for clarifying 🙏🏼
Wolfgang Klippel. Audio Science Review uses Klippel Measurement System. Does PS Audio? Just asking?
Anyone remember the “cyclone” subwoofer? Lol
Whaaat servos aren't always great? Always thought servo subs were the dream. I have a B&W DB4S 10" 1kW closed box, it goes down to 10 Hz at +-3 dB. I guess B&W measured it in factory and programmed a DSP to achieve it. Would it be possible to implement a accelerometer and slowly training the DSP for each sub? I have this theory that the sum of multiple frequencies doesn't come out the way they should because the drivers aren't ideal.
I dont think this conversation is geared towards Rythmik servo subs. They use a different method that works it seems.
I didn't think you can rule out feedback systems question? is digital or analogue. How much you want to put in and the slope you want to add? if a cabinet and driver it's sound resonance using a feedback servo system at these given frequencies is beneficial but nowhere else.
Are you going cardioid bass system, that's where you want to be Paul much better system more control more sensitive less reliant on room boundaries.
I thought of a way to change the battle for increase in volume what is a problem cardioid solves a lot of this, but if you could have a servo controlled baffle system to control the base ports in its order. might be a better implementation of a servo you're not controlling the speaker your controling the cabinet put that to Chris see what he says.
That would eliminate these problems you talked about with the servo control speaker I can't believe nobody's trying it that way. so simple and cheap as well
What an amazing microphone you're using... that douchebag with the push cart was heard loud and clear 50 feet coming and going...
Indeed! Good catch!
Textbook example of the psycho-acoustic phenomenon... "The Cocktail Party Effect"
Whereas we're quite adept at filtering out multiple irrelevant stimuli, and focus on the primary stimulus of choice.
However, presented in this video, those tools aren't at our disposal for obvious reasons.
We hear so differently and descriminently than a microphone picks up. Also, there may be an AGC, ... reaching out and amplifying and leveling (compression/limiting) all the various sources.
Myself, I like the 𝘮𝘪𝘭𝘪𝘦𝘶 ...
Why is it that subwoofers with high (qts) values sound better in sealed enclosures? imo
Because they peak and provide a kick or bump in response,but at the expense of low notes.
I would disagree with the "gradual distortion" line. Thats like stomping on a dog turd in your yard to get rid of it. It will just result in a system that sounds progressively worse as the amplitude increases. Might be good at a concert with many kW of amplifiers and walls of speakers, but at home Id rather just have distortion products when the speaker gets close to its excursion limits or the amplifier treads into clipping since the solution is free, easy, and simple: Turn the damn volume down!
Ok ok ok, I need to work with y’all; y’all hiring a Quality Assurance / Compliance person?
So, where's all the bad press for Rythmik subs?
there is none... that is because there are different ways of doing servos that don't have the same problems as Chris talks about, but keep the drivers extremely well behaved... I'll take this video with a grain of salt
Lucid discussion.
hmmm..... isnt this a repeat?
theres Henry Diltz at the other table, _again_
They film multiple segments per day. Eeek, blasphemous but true.
@@thunderpooch , i am aware....i think somebody lost track of which segments have been shown.
@Fat Rat and another "eeek" goes for Paul throwing Arnie's servo design under the bus. Rest in pieces sub par servos. Haha
Honestly, this shows great maturity by Paul, and I love it. Move on if the times and tech warrant it. If Chris designed a better sounding system, so be it.
@Fat Rat ok. Have you recently seen pictures of the new subs? I have not, but very curious.
Make subwoofers great again ✌️
Most of us audiophile's that know first hand they suck 1996 infact i always wondered if paul can hear he seems to think they are all that none servos kill them the young guy knows and hears all he described junk setup ..
You should hire this guy to design speakers for you...oh wait. :-)
Velodyne = mud.
I suspect you guys abandoned servo technology for cost reasons. I've certainly never hear any "transient squashing" on my Velodynes. If anything they're faster & certainly sound better than any I've compared so far.
Please don't abandon ribbons to meet your marketing budget. I was already disappointed by the Heil debacle. Next we'll get all the horn propaganda when you get that religion.
fantastic reply, had me laughing... couldn't agree with you more
Paul wtf - how can PS Audio make such refined hifi but not give a hoot about the sound recording of videos. It’s your brand mate!
They're having lunch outside. Deal with the lifelike sounds of everyday life :)
@Fat Rat Thanks Rat!
@Fat Rat thank you for caring Rat
@Fat Rat - caring about the defending of terrible audio
Legacy Audio solved all your issues.. www.legacyaudio.com
Relax your jaw man😳
Interesting that you moved away from servo. Still not had a proper Woof Woof experience at home.
In the UK to 'trump' commonly means to fart. Not a good bass policy 😝
Sound sucks on Lunch with Paul.
Because mic is omni-directional, but not directional as "Rode"
Man. I thought you were gonna follow Arnies ways. Not sure I trust this guy to uphold the purity of that. Sighting the works of somebody that worked at Harman does not instill confidence...
I think the more important statement was... "we listened to Chris' design and it sounds better" Kind of trumps all other statements.
@@user-od9iz9cv1w moreover, the fact that they even aired this segment is pretty definitive proof that the system without servo control sounds better.
Paul loved Arnie and looked up to him, but time and technology move forward. It's a big thing for Paul to admit what is most likely true: the system designed by Chris sounds and performs better.
@@thunderpooch I agree. You nailed it.