Moving Coil vs. Linear Drive Speakers with Dave Rat

Learn the difference between moving coil and linear drive speakers in this video...
Thanks to ‪@DaveRat‬ for making this video possible and supporting Audio University.
‪@DaveRat‬ 's KZbin channel: geni.us/ebxTO
Rat Sound Systems, Inc.: geni.us/iZlQ5
Soundtools: geni.us/WWBRByT
#AudioUniversity
Disclaimer: This description contains affiliate links, which means that if you click them, I will receive a small commission at no cost to you.

[@cboyamg]

Seeing a sub loaded into its enclosure by a forklift.. that’s a first for me. I love it!

[@janosnagyj.9540]

Same thing I said when I saw it. Amazing!

[@teddine7366]

I was just going to make the same comment. That speaker is giving me back to the future flashbacks. lol. I've been following Dave Rat for awhile now and have seen some of the bands he has worked with and seen him out in the wild mixing shows. Never got to talk to him personally but would love to.

[@MBdrummer3288]

Dave Rat is such a wild dude. I’d love to be a friend of his and just hang out and have a few beers and talk about music. I know it’d be so much fun!

[@analogkid4557]

Me too, brother! Oh, and I am a drummer, too!

[@pirojfmifhghek566]

Those failsafes are really fascinating. I suppose it's the kinda thing you absolutely need when you're dealing with that amount of current. One can only imagine how many impromptu electrical BBQs Dave has created over the years.

[@3y6ac]

+

[@csj9619]

Kind of an audio mad scientist of sorts. A man after my own heart. Those drive units look powerful. I'm gonna go ahead and approve.

[@johannjohann6523]

The magic of frequency and vibration and energy creating "sound" and music. The food for the soul!

[@daysend1341]

Can you imagine in a concert running 12 of these in the background. Every time anything drops below 40 Hertz they kick on and take your breath away. 😂 That is so awesome❤❤❤

[@andreasu.3546]

I guess you wouldn't want them to "kick" in at any threshold with a super loud volume because that wouldn't sound great. They will take over from the next cabinet above (in the frequency spectrum) and just extend the response down to lower frequencies at the same level.

[@sekng473]

I think this speaker produce Voice not music?

[@daysend1341]

@@sekng473 I thought it was a low frequency bass driver? I could be wrong tho.

[@ScottGunMag69]

This will take big shows to the next level. And this level has been pretty good!

[@analogkid4557]

Rat is the man. Full of great knowledge.

[@MickeyMishra]

I'm still waiting for the first person to mount a few of these in a Car Audio SPL environment. Dave is one really cool dude!

[@bassdabob]

Yes 2 units in series is 0.5ohm and 20k so there is amps out ther that can do it. Unfortunately this design has only very limited xcursion compared to traditional spl speakers

[@jasonnelson6624]

​@@bassdaboband here I thought space and rear suspension would be what limited the use of 2 of these. 😂😂😂

[@bassdabob]

@@jasonnelson6624check the parameters. Those woofers play well in 250liters each

[@FOH3663]

I'd suspect the motor noise may be a non-starter for car audio.

[@jasonnelson6624]

@@FOH3663 I had wondered if an ib setup would help with that?

[@andyevans2336]

I remember using Servo Drive subwoofers in live shows back in the 1980s. Tom Danley designed and boy! What an upgrade from traditional 15" woofers!

[@echodelta9]

I remember seeing a 2 inch speaker in a first gen transistor radio that had a short link to the little cone and went to a magnet-coil mounted on back. So we were half way in the early 60's. Likely done in the teens with first gen radio speakers post horns. The key thing here is feedback with servo action not just a dumb motor. I have a pair of PA speakers that have feedback and their sound never fails to deliver.

[@eabr2881]

Dave Rat productions is awesome.

[@aaax9410]

Before voice coils this is pretty much how loud speakers worked but this is on a grand scale , very cool :)

[@pacresfrancis1565]

Im trying to learn more about Linear Drives but I cant seem to search good results. Where do you get info about them?

[@FOH3663]

​@@pacresfrancis1565 I'd peruse Voice Coil, an industry source on drivers. ProSoundWeb as well.

[@teddine7366]

man,,, now im trying to remember what they were called. they needed the audio signal plus power. for the life of me i cant remember. field coil speakers maybe. hmmmm. they used something like an electromagnet. if you can remember comment back.

[@aaax9410]

@@teddine7366 They are indeed feild coil

[@KristoffKuche]

I always wanted a fork lift to move gear around . One of my trucks , a two ton Grumman is propane powered . Poly coned linear transducers , way cool !

[@erniesanders3724]

Dave is “The Master”.

[@KetansaCreatesArt]

Such a master. 😎✨ By the way speaking about the cone coming out or in - after touching the battery to the terminals, if the cone comes out then that is supposed to be the correct polarity. Minus to minus and plus to plus.

[@podboris16]

dave is such a leyend!

[@ovalwingnut]

Pretty COoL stuff... Really appreciate hearing about the nuts & bolts of speakers. All this is going on my resume. Thanks! Cheers from So.Ca.USA 3rd House On the Left (pls call before stopping by)

[@healthymindhealthybody9692]

More version of speaker and motors would be EPIC

[@user-pq9ji7kt4l]

Oh. This will be cool!

[@vse0]

The Danley principle with upgrades. VERY neat!!

[@FOH3663]

Danley principle?

[@dannelson6980]

Servo-drive was a rotor motor with linkage to the cone. The mass of the rotor and linkage made them only useful below 50 Hz.

[@FOH3663]

@@dannelson6980 Thank you. Well familiar on Tom's work, just curious on what the OP was referencing in particular.

[@andreasu.3546]

What a great guy.

[@johannjohann6523]

You know ya got a subwoofer when you need a forklift just for the driver. lol. Dave Rat - the mad genius!

[@621ELECTRONICS]

Quite the interesting subwoofer design.

[@rishiyoutube]

Really informative video. Learned a lot. Though horrible camera work by the videographer who took handheld shots!

[@K.D.Fischer_HEPHY]

Awesome stuff. Need more if it.

[@chucksaeger7500]

Fascinating!

[@VA3JPX]

Now, that is cool. Gotta love new technology. No wonder live concerts sound better and better as the years go by, it's because of people like this who think outside the box.

[@shanerorko8076]

No he is thinking inside the sub box.

[@FOH3663]

The quality of live sound can be extraordinary today ... thank goodness.

[@normal_human]

I really wanna hear this beast in action..

[@FOH3663]

I believe Dave employs them in the EDM tent at Coachella.

[@halbertking2683]

So a guy brings a Fender Vibrolux Reverb . He said it had no low end . I asked about anything else he could tell me . He just replaced a speaker . That's what 2 speakers out of phase gives you.

[@toddwilliams8761]

2 speakers out of phase: Such a simple wiring mistake. A monumentally horrible effect on the sound, with such an easy corrective measure to fix it.

[@CajunReaper95]

⁠@@toddwilliams8761fun fact running speakers out of phase is a common practice in a isobaric setups as the subwoofers run in a push pull configuration!

[@ScottGunMag69]

It’s the best mistake.

[@Onionbaron]

Ace Of Base!

[@mrsonor1090]

That's a band from Sweden :)

[@FOH3663]

​@@mrsonor1090 Yep, knew it! I saw the sign ...

[@mrsonor1090]

@@FOH3663 Well, It's a Beautiful Life...

[@FOH3663]

@@mrsonor1090 It's all that she wants ...

[@mrsonor1090]

@@FOH3663 And I'm also from Sweden, so... Happy Nation. But Don't Turn Around because it's a Cruel Summer (this has gone to far... make it stop)

[@jacobclark89]

Just when I thought I seen everything 😮

[@tanmaymondal69]

Amazing

[@deltacx1059]

There are the fan/paddle style speakers that can go super low but you have to put them in a window or a special hole in the wall.

[@marcusfred4480]

Yes. A rotary subwoofer.

[@FOH3663]

"they go super low, but you have to put them in a window or a special hole in the wall" That's an IB or Infinite Baffle alignment.

[@johnbogle6475]

Linear drive speakers are such a bizarre concept. I've always though of speakers as an air pump of sorts (of course push pull :). This design reminds me of an internal combustion engine (piston & connecting rod) but rather than a crankshaft converting the energy into rotational force, the connecting rod directs the energy directly into the cone. I'd guess it is too heavy for accurate mid or HF information. As for a Sub though... Very cool.

[@andrewgillis8572]

6 even 8 inch speakers used as bass frequency mics thru the years

[@roadiesnrockstars]

Excellent explanation 😉

[@felixokeefe]

Correct me if I'm wrong but I'm thinking these things could be fitted out with water cooled coils if needed for more power handling.

[@FOH3663]

Yes, but that'd introduce unnecessary complexity and failure modes. In typical applications, it's vital that it's absolutely bulletproof. They have structural heat sinking, plus ample coil area for thermal dissipation.

[@mycreations4527]

Can you do a video covering the topic of DC Offsetting? My Dad has a few recordings he did in 1996 and as I was remastering the audio, I noticed a Majority of the signal is offset from the center. I believe I know most of how it works but I think it would make for a great video

[@teddine7366]

Meyer Sound has a video with this girl laying across one of their giant subs. Imagine taking a few of these and laying a mattress on top and just lay there with like a 25 hz cycle playing through them. Maybe that would fix my back.

[@wherearewewherearewe]

23 hz 😁 Well now I HAVE to find one of these to play on!

[@cougar1861]

Does the order of magnitude greater ability of the linear speaker to dissipate heat correspond well to what, I assume, is its much greater generation of heat?

[@bassdabob]

I think the video misses then main benefit of the mforce. With its 0.25 resistance it barely creates any power compression at all as the current only drives the cone and lacks the standard 1000s of watts heat loss. In addition to that the driver will not shift parameters as a standard woofers as there is no Long term heat aswell.

[@cougar1861]

@@bassdabob Thanks

[@dasibaho]

Fascinating.

[@Bassotronics]

I’m confused. I’m using a t-line system with an 18” Subwoofer and I can play down to 12Hz and can feel it and shakes my Windows. Not sure what I’m missing.

[@kristofnagy1574]

I think Dave was talking about driving the speaker without acoustic loading. I'm not really into designing and simulating boxes, but maybe if the driver can safely move at a certain frequency under high power without burning itself, then when acoustic load is added by a box, the output will be higher than a normal speaker.

[@Bassotronics]

@@kristofnagy1574 Oh ok.. thanks. :)

[@FOH3663]

An 18", 12hz capable transmission line would lack level, and freedom from BL non-linearities and compression, ... vis-à-vis this platform.

[@circuitsmith]

My tinnitus is aroused just watching this!

[@deaf_as_hell_wilson]

I just want to know how I could get my hands on a singular M-Force linear motor

[@Edwin-van-der-Putten]

my guy is

[@bassdabob]

I think the video misses then main benefit of the mforce. With its 0.25 resistance it barely creates any power compression at all as the current only drives the cone and lacks the standard 1000s of watts heat loss. In addition to that the driver will not shift parameters as a standard woofers as there is no Long term heat aswell. My only concern is dust inside the motor as there are glide rails that guide the magnets embedded into the design. What does dave rat say about this? Especially as there are many design that have the motor facing outside.

[@Sheldon42]

Big problem with these are very high Q of the system. Your frequency response changes with just about everything: sub position, number of subs, temperature, drive level...basically they never sound the same. And also motor can overheat pretty easy. And glide rails fail.

[@bassdabob]

@@Sheldon42where does this information come from?

[@Sheldon42]

@@bassdabob I developed and built Mforce subs. So, first hand. You need to correct EQ on them every time you use them.

[@bassdabob]

⁠@@Sheldon42so position and amount is similar to other systems? Temperature? You mean the surrounder temp? I could not notice any further heat until now. I believe glides might fail because they can easily be dirtet. Maybee we speak separately about your experiences.

[@CajunReaper95]

This might be a dumb question but I’m not well versed in Pro Audio but how come PA subs still use accordion surrounds vs the high roll surrounds you seen in other applications like home theater subwoofers and car audio subwoofers?

[@mattlong4102]

I think it's the increased balance between the restoring force of each direction of travel at high spl. Meaning the amount the surround pushes back as the cone moves away from its rest position is more even when comparing inward and outward displacement.

[@flamencoprof]

Good science, well explained. Why is the drive mech in front of the cone, where it can "muddy the waters", so to speak? 🙂 With something that big, would axial length really matter? Or is it because the design is mainly aimed at low F, which wouldn't even see the driver?

[@FOH3663]

The motor being on the "front" has zero negative impact on performance. The 56 foot wavelengths of a 20hz tone aren't impacted by the motor out front. Even way up top of the sub's range at 80hz the wavelengths are 14 feet ... so the mechanism is still acoustically small.

[@flamencoprof]

@@FOH3663 I should have considered the actual wavelength, I stand corrected, thx.

[@FOH3663]

@@flamencoprof It's so helpful to automatically associate a wavelength with a given frequency! That size orients you to essentially all acoustic interactions, everything's about wavelength size. Plus, historically flipping the driver over with the motor outward is advantageous for cooling. I'm sure there were more, but early on in the 80's TAD, EV, and I believe EAW had motor out subs/platforms, as they explored distortion lowering and motor cooling.

[@flamencoprof]

@@FOH3663 I am well-educated re frequency vs wavelength. However, despite a lifelong interest in guitar amps, I have never investigated the world of high-power low-f speakers. The cooling effect is obvious once pointed out. Even at over 70, I appreciate learning new things. Thx.

[@fixnreview]

What about the accuracy of this driver? Is it better than any moving cool or the same?

[@FOH3663]

It's all about level and extension. Our hearing mechanism isn't too adept at discerning distortions and non-linearities in the bottom octaves. That said, it's performance characteristics are stellar. Linear BL curve, essentially zero compression due to extraordinarily huge motor structure.

[@luke144]

Can I get a job Dave? I have serious experience. Please Dr. Rat!!!

[@Crixtonaizy]

EYYYYYY!!!

[@lisakingscott7729]

Great info, but the camera movement made me feel seasick. Also the permanent magnet does not have 'magnetic energy' it has a magnetic field, but that's a minor niggle.

[@acoustic61]

Seems like when phono cartridges went from moving magnet to moving coil. But opposite. I wonder if speed is sacrificed with added weight.

[@FOH3663]

In loudspeakers, speed isn't impacted by weight. Weight does impact sensitivity, but not speed. Speed is a function of how much current can be instantaneously pulsed into a voice coil, and that current is limited by inductance.

[@lazygazzzer]

Watching this I am wondering just how heavy these things are?

[@erman.k]

10:20 It is difficult to hear sounds between 0 and 35HZ. Usually the sound pressure is felt in the body.

[@GothGuy885]

I only knew about moving coil speakers, so this is really fascinating to learn about! thanks for the vid 😀👍

[@murrayshekelberg9754]

there are rotary subs as well

[@Edwin-van-der-Putten]

Dave love you... you are great!!! come visit me once!

[@Chromedome-ss6mg]

The question is that I've always wondered is what makes one subwoofer different from the other brands. Seems like they're pretty simple devices. Rockford fosgate compared to jl audio I mean what could be the major differences. What makes one company not copy a really good company and have the same speaker. I just don't get it

[@Notmehimorthem]

Dave is your Dad!!! LOL

[@snakezdewiggle6084]

I can't help but wonder, just when ' they ' will start crossing over to ambiant speakers...

[@administratorperson3272]

i have ads s10 subs, cast al. basket, 3&5/16" depth front mounted, Fs=16hz Qts< .21

[@AudioEuphoria080]

cool theory but anyone with subwoofer audio knowledge knows theres not too much going for these. you can easily get regular subwoofers to output at those bandwidths.

[@Mr_ToR]

why shaky camera?

[@lucianotognelli192]

E' la variazione di fase tensione/corrente che produce suoni. Nient'altro.

[@johnstreet797]

you could sub sonically communicate with elephants with that

[@goodun2974]

Using a subwoofer to communicate with elephants has been done before, several decades ago, with a 30" subwoofer mounted on top of a Jeep. ElectroVoice had a 30 inch woofer in 1958 and there have been a few others since then.

[@NNokia-jz6jb]

What brand is that? Type?

[@kristofnagy1574]

Powersoft M-FORCE 301P02

[@NNokia-jz6jb]

@@kristofnagy1574 Great. Thanks.

[@kristofnagy1574]

@@NNokia-jz6jb No problem!

[@kenp9073]

Shed a tear as Dave destroyed that amazing EV driver...😢😢😢

[@PaulEubanks]

I've seen those rotating fan blade subwoofers that do a similar thing, but I guess I don't see much point for reproducing sound below 30 Hz. Anything under 30-35hz isn't really useful sonic info tbh.

[@Bassotronics]

That really depends on your music goals or sonic goals because I have friends who can play down to 12Hz and shake all the windows and have a fun doing it. In fact, one time I was playing a 17 Hz tone in my car and a lady gave me the middle finger; that was awesome.

[@mboykin6047]

You can’t hear it perhaps but you can feel it in your chest

[@PaulEubanks]

Sorry nobody can hear LFOs, that’s the point.

[@goodun2974]

​​​@@Bassotronics, Yeah, that's why we put audio systems in our cars, to listen to "tones". This may fall on deaf ears, hopefully not literally: try listening to music instead, that's a novel concept nowadays. And before you write me off as some old fuddy-duddy boomer, that's simultaneously both true and false. I was installing car stereos for my friends beginning in 1974, and by 1983 I had a triamped system in my car with 10" Dynaudio subs in a tuned cabinet I built, Fosgate and Audiomobile electronics, a/d/s speakers and a Nakamichi tape deck. My work was sufficiently well respected locally that I even installed Nakamichi systems in a half-dozen Saabs for the president of Saab-Scania US and his executives. The emphasis back then was on sound systems that were clean and *musical*, but I went to the Vegas CES show in 1988 or 1989, and of 60 or 70 cars out in the parking lot that were being used to demonstrate car audio equipment and systems, I only heard 3 that sounded good (Fosgate was one of them, I don't remember the other companies). People were going for loud volumes and heavy bass, and a completely imbalanced audio spectrum. Selling and installing an expensive system & installation to people who just wanted to be loud was easy enough, but there was no satisfaction in it. I got out of the business in 1990 ( became a telecom tech for a while, then spent 20 years as an audio-repair bench technician before retiring). Unfortunately, the years I spent climbing into car trunks and contorting myself to get underneath dashboards did some bad things to my back and neck ( I am 6'2" and used to be pretty flexible) and now I'm living with arthritis and pain. My hearing still works at least, although my top end response cuts out at about 13k; but there's not much worth listening to above that, just as there isn't much worth listening to below 40 Hertz unless you listen to synthesizers or recordings of church organs. The fundamental note of a bass guitar E string is 80 Hz with some output an octave lower at 40 Hz,and of course a bass drum goes a bit lower than that, but putting dual 15" or larger woofers in a car makes about as much sense as pouring a cup of sugar on your bowl of breakfast cereal.

[@goodun2974]

@pauleubanks, the wavelengths of low frequencies are so long that back in the days when bass players on big stages would use folded-horn speaker cabinets they could hardly hear themselves but the audience, and perhaps the singer at the very edge of the stage, got pummeled by the bass. It's impossible to reproduce anything audible that low in a car anyway because the cockpit size of the vehicle is so small. Sure, you can feel it , but then you also have to go through every part of the car and install sound-damping material and tighten everything down so that it doesn't rattle.

[@amgineacoustic]

They both use the same motive principle just reversed. So not so different They still just high excursion BRs

[@jesseb3758]

Robotunderground

[@karayuschij]

479th!

[@sixcolors4226]

3:37 Young dude said drill bit, positive, negative repeating; Old dude said "yeah you get square waves." Young dude said "audio is not square waves but is alternating current." WHO IS CORRECT? WHAT IS THE DIFFERENCE? Do a 13Hz and 26Hz square simultaneous audio wave and compare it to a 13Hz and 26Hz sine simultaneous wave. Old dude acts like a crack head on some shid in this video.

[@Sethfranzpopsicle]

the old dude is right its just off and on, no smooth transitions between pulses. thats a square wave a sine wave has smooth transitions between polarity flips. the battery on a drill situation would not provide any transition besides an open circuit between polarity flips im not an expert by any means but i think that old guy might know more about this stuff than this "audio university" fellow.

[@sixcolors4226]

@@Sethfranzpopsicle I don't know jack and the fact that I caught that shid and don't see it anywhere else in the comments is mind blowing.

[@felixmotanul5242]

Amazing and yet you sold all this knowledge and technical details to the Chinese. Result? Anyone who bought Made in China speakers made with prestigious names, cried after.

[@ГусьХ-х3г]

kzbin.info/www/bejne/gIi8cmCOg657jaM

[@whitlcj1]

Sbadass mk

[@Sethfranzpopsicle]

"not square waves" bro that would definitely be a square wave.

[@Edwin-van-der-Putten]

why you lean on the stupid guy?

[@7333-e3k]

Is it just me or does this guy sound a bit like Trump

[@FOH3663]

"... they tell me it's the most powerful subwoofer, very powerful, ... so, so powerful that it's more powerful than anything before it, ... a beautiful, powerful subwoofer. Very powerful ... very powerful. The most powerful"

[@tholisth6857]

First