Monster magnet meets subwoofer...
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- เผยแพร่เมื่อ 26 พ.ย. 2022
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Speakers play music by magnetism. The stronger the magnet, the louder and better it will usually play.
Makes me wonder what will happen if I take one of my super-strong neodymium magnets and put it behind a subwoofer. Will it play much louder? Does it matter what pole of the magnet faces the speaker? Let's find out!
The F71 Teslameter donated earlier by Lake Shore Cryotronics:
www.lakeshore.com/products/Ga...
One of the 150x50 mm disc magnets donated earlier by www.magnetportal.de/
My Patreon-page: / brainiac75
Recommended videos:
Monster magnet meets plasma ball...: • Monster magnet meets p...
Monster magnet meets lasers...: • Monster magnet meets m...
Did you miss one of my videos?: / brainiac75
FULL MUSIC CREDITS
Time code: 0:01
"Darkness is Coming" Kevin MacLeod (incompetech.com)
ISRC: USUAN1100584
Intro part looped by me.
Time codes: 0:54 + 1:43
"Lightless Dawn" Kevin MacLeod (incompetech.com)
ISRC: USUAN1100655
Time code: 1:31
"Monkeys Spinning Monkeys" Kevin MacLeod (incompetech.com)
ISRC: USUAN1400011
Time codes: 2:35 + 11:06 + 12:09
"Long Note Three" Kevin MacLeod (incompetech.com)
ISRC: USUAN1100424
Time codes: 3:39 + 3:56 + 5:00 + 7:58
"Newer Wave" Kevin MacLeod (incompetech.com)
ISRC: USUAN2000024
Time codes: 4:48 + 5:28
"Energizing" Kevin MacLeod (incompetech.com)
ISRC: USUAN1900040
Time codes: 8:49 + 11:37
"Perspectives" Kevin MacLeod (incompetech.com)
ISRC: USUAN1300027
Time code: 10:10
"Peace of Mind" Kevin MacLeod (incompetech.com)
ISRC: USUAN1200099
All music above licensed under Creative Commons: By Attribution 3.0 License
creativecommons.org/licenses/b...
Time code: 8:17
Mix of two tracks:
1) The Shimmering by fran_ky (freesound.org/s/237363)
Licensed under Creative Commons 0 license
2) "Spacial Harvest" Kevin MacLeod (incompetech.com)
Licensed under Creative Commons: By Attribution 3.0 License
creativecommons.org/licenses/b...
ISRC: USUAN1100653
#Speaker #Subwoofer #Magnet - วิทยาศาสตร์และเทคโนโลยี
The basket may have become magnetized disrupting the magnetic field. Running a sine wave through the speaker for a while at moderate levels might help restore the magnetic field strength. I wouldn't know if the magnets were permanently changed. Neodymium magnets are usually used for small speakers, not large ones. It might be interesting to repeat the experiment with a field coil speaker. With and without the field coil working.
The subwoofer appears to have a machined aluminum frame. Not to say it couldn't gain some magnetism with the presence of the large neodymium magnet, but it would primarily function as a shorting device to the magnetic circuit. I could see this easily being the case with a stamped steel frame, which would already cause some stray flux to travel up the basket to the surround landing. Secondly, it's more likely that the larger neodymium magnet was just pulling some of the magnetic charge from the subwoofer, as it is possible to do not only with magnetism itself, but heat as well. (More susceptible in Neodymium though.)
• Brainiac75 is actually doing something "similar" on a larger scale that Digital Designs does offer as an upgraded package to some of their subwoofers, which is known as 'Supercharging", where a slug of Neodymium can be added to the top of the pole-piece to improve BL (Thus BL²/RE)
Also, there as several larger format subwoofers that do utilize rather large neodymium magnets, such as the B&C iPAL 21". If you search "B&C iPAL 21 magnet" on Google Images and locate the following post; "B&C 21-IPAL Driver and Measurements Discussion - Page 3 - Bass Gear - Data-Bass Forums". If I recall correctly, the B&C iPAL uses a 6" O.D. N48H, though, is information that is not publicly available to my knowledge.
Other Companies that provide large format Neo subwoofers include but are not limited to Harbottle, Sundown, Digital Designs, Ground Zero, Pride, Eminence, Massive Audio, etc.
@@DJSNT DD audios supercharging option doesn't really change the bl much but it does raise the inductance significantly which allows the sub to play higher in the octaves with a smoother response curve
Neodymium magnets don't like to get hot, they lose their magnetism.
I worked in a club were the bass speakers magically just stopped making sound.
@@Margarinetaylorgrease i dont think the neo got hot there at all lol
@@Audysseus It was a response to Neo's being used in small speakers.
When your running 600w + drivers heat is a thing.
Hope that clarifies.
Maybe the weird results with the 20hz test have something to do with the selected frequency? Try using a white noise signal (frequency flat) with longer time duration (at least 10-15 seconds, but longer is better), and later analyze the frequency response differences. Perhaps you find that, for that particular frequency, the response is lowered, but increased for others. I'd like to see you try something like this in a future video.
I agree, I think testing at Fb might produce a more interesting result as well. Though the demagnetizing is a bit of a problem. So all results will probably be inconclusive. Unless he picks himself up a magnetizer. That way he can re-charge the ferrite after each test.
This is what I was thinking too. You could be creating some sort of resonance at certain frequencies and their harmonics.
Yeah, because the music used isn't just 20Hz bass
I think you changed the impedance rise on the 20hz cycle. If you could get power reading in real time I bet the subwoofer is receiving more power depending on the orientation of the neo magnet. If you have a clamp and multimeter you could get a power reading while playing the 20hz.
This might be the actual right answer. Higher Bl will cause more electrical damping. At and near resonance frequency, this gets rather criticsl.
I took an acoustics class in college where I earned a degree in electrical engineering. It was VERY high level. You would not believe all the the theory and math analysis that goes into optimizing a speaker's design. It doesn't surprise me that you didn't really improve the speaker. It is designed to tight tolerances with the parts that are there. The math in that class killed me. I almost didnt pass.
My cat was coming near me during the video. She was purring then exploded.
Oh boy, never knew infrasound could have that effect ;) Thanks for the early watch!
Same Here 😲:-D
horifying
They’re always free replacement cats on craigslist, we have two that we got from craigslist and they are pretty good.
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An interesting alteration to the last test you did would be to play a sine wave sweep from 20Hz to 20KHz, and comparing the frequency response of them with/out the magnet
i love how you show what types of dangers the experiment can cause in the beginning, keep up the cool experiments
Hey Brainiac75,
The most critical evidence of performance changes would come from the Thiele Small Parameter; Large Scale Parameters via Klippel would provide the most information as to the effect on BL over Excursion, and what impact this has on inductance, but that would be a pretty penny to accomplish.
Typically, a shift in the BL will directly impact the Q parameters (Qts & Qes). The Lower the BL figure, and therefore a lower BL²/RE, would result in Higher Q parameters. Typically, the lower the Q parameters become, the more adequate a subwoofer becomes for bass reflex enclosure designs, whereas, the higher the Q parameters become, the subwoofer yields better performance in a sealed and/or Infinite Baffle alignment.
If the Q parameters were being lowered, a bump also occurs in the response above the tuning frequency of the bass reflex enclosure as the driver becomes more resonant.
Measurement of bandwidth before the magnet is applied, then post-application of the magnet being attracted to, and repelled from the magnetic structure of the subwoofer would certainly be the cherry on top.
I love your mixes. Your answer was exactly what I was thinking, albeit, you did a much better explanation than I could've.
It's a good explanation, but one thing you've written is very wrong: If Bl is lower, then Qes and Qts and higher.....If Bl is higher, then Qes and Qts is lower.......You know that speakers with strong magnets usually have low Q factor, because stronger magnet means more electrical damping, and more damping = lower Q. This is the formula for Qes: Qes = Res / (Bl * Bl) * sqrt(mms / Cms).
@@vladimirmikasinovic2374 I am actually aware of this, but in my haste to respond I swapped around higher and lower in the explanation. It has sense been corrected.
Just like the old saying, measure twice, cut once. I should have reread the response more thoroughly. 🤦♂
Yeah he’s got 30k or whatever a klippel cost lmao
In days of powerful cheap processing, Bl, and Qes values might not have much to do with a speaker choice. You just straighten it out. The elephant in the room is true efficiency, heating and power distribution. Rule of thumb if all else being equal, you have DSP, and an amplifier with more voltage swing, get lowest qes/highest (bl*bl)/2 driver possible. Flat natural frequency response is not needed anymore. Just being that guy, poking. 🤣
The difference is probably due to the fact that the simulation isn't taking into account may things. For example, just a simple screw somewhere could slightly change the magnetic field leading to a different reading that then one you where expecting. If you were to get the real life setup as close as possible to the simulation, you would probably get closer results to resemble that simulation.
At low frequencies, the speaker impedance is mostly back EMF generated from the voice coil moving in the magnet. The voice coil has to move further to generate the same back EMF when the magnet is weaker, increasing the volume. it will also increase the current draw from the amp and reduce the speaker efficiency.
Since I said with my experience, crushed ice in a tube would be the safest way to bring magnets together, I always wondered how much it would affect a speaker with just one these magnets. 🤣
It is more than 50 years that I operated in the electronic sector. When I begun, ferrite loudspeakers were still part of the future. The speaker at the time used iron magnets, and the most powerful commercial speaker was 4 Watt of power - which coincidentally was the same power delivered by a single ECL82 or 6AQ5 (beam tetrode) working in class A.
10 W speakers were reserved to Hi-Fi systems utilising a push-pull of two EL84 per channel.
Again, there were no ferrite around. The speaker were reasonably efficient even with iron magnets, because a loudspeaker is designed as a system, where the moving coil mass and excursion is balanced against the magnetic field.
Changing only one parameter can't bring improvements; the whole system must be re-dimensioned and re-optimised.
With a stronger magnetic flux in the same air gap, you can increase the coil mass so it can handle more current, you can have wider excursion (which require higher damping factor) and a wider cone area, which in the end increases - in a non-linear fashion - the amount of power transferred to the air. In all of this, η (efficiency) varies wildly.
Designing a speaker is a feat of engineering and, notwithstanding the existence of models and simulators, is still done manually because there are many competing factors. It useless to make an extremely efficient speaker if it is not linear. Neodymium speakers can be very small for a given power, but their linearity & bandwidth outside a speaker box can make you cry...
That's actually a very nice subwoofer that you have. The box rise (Impedance rise) could have actually been affecting it. A very good way to tell if a magnet/magnetic field effects a speaker would to do the test while using shunt resistors in series with both coils (each coil having an independent shunt) and oscilloscope to see if the current increases or decreases while while watching the current waveform to see if anything changes.
Or just simply run the driver at a single frequency..
As far as I can guess, the big magnet would have messed up the TS parameters of that driver to some extent, and bass reflex enclosures are sensitive to those changes.
1) A 10% increase in magnet gap strength is only about 0.4dB SPL increase...
2) A resonant system is dependent on Fs and Q to get a response level. Way above the resonance, efficiency should scale with magnet gap field strength. At or below - you have to calculate the resonant behavior to get SPL difference. Lower field strength might give higher SPL at a certain frequency depending on the resonance function. Especially in a fouth-order system like a ported sub
you should have checked how much power was going into the speaker during the test too because I am pretty sure the impedance of the speaker changes with the magnetic field too so you probably had different amounts of power into the speaker during the test
Oh, i can't wait for the audiophiles' expert opinions!
my audiophile expert opinion is the big magnet is way way to far away....+ the magnetic circuit or the woofer is already "perfect"....any additional magnetic field will not add much energy
Now this is the magnet content I can get behind! We need more speaker magnet test videos 😂
Oh boy this might go wrong. Speaker going BRRRRRRRRRRRRRRRRRR
Me enjoying the music from the speaker at full volume,suddenly he talks 💀
My theory would be that the TS parameters change if the magnetic field strength changes. Higher strength will result in higher Fs and lower will result in a Less Efficiency but deeper bass extension.
I don't think Fs (or rather: Fc) will change significantly or at all, but Qtc will definitely change.
Maybe when in or close to resonance, a stronger motor will attenuate the oscillation because it is out of phase.
However, I don't know if this theory is true - because my impression was that with lower Q (stronger motor given all other parameters remain), the output at Fc stays about the same, but the passband will be louder. There are many effects at play concerning speakers at resonance and their impedance and output levels, some of which will sometimes null each other out and sometimes not. It isn't a very conclusive experiment to make for people not familiar with the peculiarities of audio physics.
It would have been better to do the frequency test in the passband of the woofer (say: 80 c/s) because here the outcome would be much more predictable, louder speaker, stronger motor.
I guess with a weaker field you get less back emf, increasing the terminal velocity of the coil, which increases the volume in the end. This could be the case if the back emf in a speaker is not negligible.
yep, and if the port is tuned to a frequency higher than 20 hz (which it very likely is), 1) the speaker is essentially flapping around, and likely approaching this terminal-ish velocity, 2) the second speaker+port resonance may be contributing to even eliminate surround return-spring action, leading to even more likelihood of approaching this terminal velocity.
it's like an unloaded dc motor, which will spin faster if one reduces the strength of magnets...
@@victortitov1740 Shouldnt it act like a synchronous motor with a fixed 20 Hz input?
Watched your content some 9 years ago and this is finally being recommended back to me after making a new yt account, forgot this gem of a channel existed (sry). Great content as always I've always enjoyed the magnet experiments. Thx for all the childhood inspiration!
I lost count of how many speaker coils I wrecked in my childhood. They sounded great until they sounded terrible 😂
That is the most strange subwoofer design I've ever seen
Don’t let the magnet eat you. Magnet: nom. You: aaAaAaAaaAAaAAaaaAaaaa!!!
The magnet glued to the back of some speakers is to aid in magnetic shielding for near electronics by compressing the fields. Should make little difference in the output sound. ;)
from what i know, if the polarity of the speaker is correct, the speaker should vibrate outside, maybe that influences somehow
False, the cone will move outwards and inwards at the same rate, given the coil is within it's linear region, and a sine wave with no offset.
I rewatched ur merging monster magnets like a million times
I never thought I would be sitting here on a Sunday morning binge watching videos from a fellow from Denmark and learning so much in a cool way. Thanks brother. May God bless you and draw you near to Him.
I loved this video. Please do a part 2!!
thanks for the music timecodes haha
and thank YOU for providing readily accessible and low abstraction level edutainment
Ez.. the monster magnetic field over powered the little ones and because of it's massive field the entire area was already filled with dense magnetic flux lines.. hence sound increased instead of decreasing..
In the repelling set up the fields were almost erased away from the ceramic due to the super strong repelling force of the monster hence the entire magnetic strength of the ceramic decreased (may even demagnetized a bit permanently), resulting into lesser amplitude.
very interesting, try sticking more rings from the magnetic ones on the speaker and maybe it will increase its performance.
I would have wanted to see you open the speaker case and put the neodymium directly against speaker magnet so that magnets touch.
Different frequencies induce a different impedance on the voice coil. I suspect this has something to do with the 20hz test. You should repeat the test at 20,30,40,50 and 60hz. Also do a sine wave sweep from 20hz to about 120hz.
You should have slap (but gently) this magnet onto the rear metal flange - this would have given a significant increase in volume. 😉
Maintaining attractive polarity.
It seems like their is a point when the magnet makes it louder with the South pole facing it, then it gets more quiet as it gets too close. Maybe it was nothing.
2:25 -- summing like this only works when you consider that Z is actually a vector! To get the ohmic value, you calculate the vector length Z = sqrt( X^2 + R^2 ). Z is a vector, similarly to a complex number in the coordinate plane of real and imaginary components (swap them for resistance and reactance, respectively). The angle in which Z is pointing equals the phase difference between voltage and current. Oh yeah, and X can actually be negative (a capacitor). Try wrapping your head around that.
9:25 -- I think that here we need to consider that the monster magnet is conductive. Every time a magnetic field reversal occurs in the coil, a respective field oscillation occurs in the magnet itself. Such magnet re-magnetisation cannot occur instantly, and it also consumes the energy of the external field. This effect gets stronger at higher frequencies. And it gets particularly strong with conductive magnets due to the eddy currents. At high frequency, a significant portion of the coil energy can be absorbed by the monster magnet, lowering the sound volume. At low frequency, this magnetic loss is insignificant. And as for the volume gain, I have not a clue. Did you position the monster magnet so that its edge (where the field is stronger) is aligned with the speaker axis, and the monster's field strength actually takes priority?
you can't expect the additional magnet to do anything because it isn't part of the magnetic circuit and the real magnetic density in field lines exists in the pole gap where the magnetism is at it's highest a good thought experiment.
"Today on recreating the Skullcandy Crushers in a subwoofer..."
The prolonged exposure to loud volumes warning instantly disregarded lol, i run four 12's in my car and pound my ears on a daily basis ha ha!
I haven't been above 2x12" in my cars over the years. More than enough for small European cars x) Thanks for watching!
@@brainiac75 My four 12's are in the boot of a mondeo, i still want more bass lol but boot space limits me to four and my electrical system also means im on the limit of what i can run :(
You need to measure the speaker impedance while playing with true rms volt meter and a/c clamp to determine real time output power because it will change when you have a more/less BL or a stronger motor force. If the woofer impedance had even a slight increase then your output from the amplifier will be reduced. If you turned up the amplifier to maintain the same rms output power from the amplifier the speaker could see an ever larger spl increase.
I think the problem was that the 2nd test you did not place the magent in the center - it was placed lower (There for it was a differnt magentic field affecting the test in the 2nd test)
Your tests should be done with an app of approximately 750w rms at 4 ohms to get the maximum output. This 1.5 times the rms value is typically what professional sound engineers use for low end powering
I have this subwoofer driver laying around😝 It has done an impressive job over the years in use
To use a monster magnet, you need a pancake style voice coil. The flux is too high for a regular voice coil because it will experience an undue amount of eddy currents.❤
The Speaker is a DUAL VOICE COIL!!!!! So the modeling you did is NOT THE SAME! - That is the ONLY thing I could think of 🤷♂
We need a dedicated video on your home theatre setup, it looks quite serious!
When I was shopping for a home to buy these loud car audio systems provided a quick and invaluable indicator of what properties to avoid.
Depending on the frequency generated by the coil, you will create a resonance in the envirement. It is possible that the induction force in the coil will affect the ressonant circuit of the speaker and then variate your results. I dont know but it is possible that when mannufacturing neodimium magnets, some elements tend to migrate to north or south pole. The difference between chemical composition can change the inductance of the coil.
The explanation is actually quite simple. When you increase the magnetic field in the coil gap, it actually increases the impedance of the speaker. That means, the velocity of the coil is slower for the same amount of voltage. The coil will draw less current, so it won't draw as much wattage from a given amplitude. When you use a low frequency test tone, the speaker operates in 'compliance mode'. That means, the excursion is proportionate to current, rather than velocity, therefore, no EMF. At a frequency well below the free air resonance of the cone, the impedance of the speaker drops to approximately the DC resistance of the voice coil, drawing more current from the amplifier. A stronger magnetic field produces more force, for a given current. The result is, the speaker becomes less sensitive to high frequencies, but, has much more force at low frequencies. The frequency has to be low enough, that the improvement in EMF doesn't raise the impedance, lowering the power the speaker will draw.
I love these crazy experiments. Though I actually expected these results given the way most speakers and microphones work, it's still great to see it tested anyway. I keep wondering why electromagnets aren't used more these days. As we all know, permanent magnets aren't.
Only good reasons are cost and convienience, no one wants to connect their speakers to the mains, the extra power supply would incur costs. However if you drove both voice coil and electro magnets in a push pull configuration, in theory you could lower distortion.
@@engjds True, it would make isolation harder, and thus cost more in terms of components. Though, a company that makes professional grade products likely wouldn't care. They could just charge more and their customers would take it.
@@anon_y_mousse Yeah, speakers are a funny technology, they havent changed at all nearly in decades, just slightly better materials, more rare earth magnets used.
I think the biggest advancement will be made when spiders and surrounds are replaced by magnetic suspended systems where you can control compliance.
Electrostatics good, but they are poor at low frequencies, same with planar(mags).
You can buy 2nd speakers now at around £500 from 4 decades ago that will blow anything new up to 5 grand.
You measured the magnetic field of the speaker magnet backwards, the north needle of a compass is it's south pole, so the speaker performed as expected even tho it looked like it was backwards
audio engineer here,you said that it wasn’t a huge difference with the magnet near. keep in mind that dBs are a logarithmic scale, for every 3 db more the volume doubles, so it was a pretty large difference
I always wanted to try this when I was a kid but the strongest magnets I could find were other speaker magnets.
01:59 "more watts needed from the amplifier" - are you sure about that? Does the efficiency of the speaker change somehow?
Comment before watching: I don't expect more bass. With motor Motor force usually the Qes in the Thiele Small Parameters is lowered and with that the Qts. BUT the SPL in the higher frequencies will be increased.
After watching:
The results i don't understand either even though i build and modify speaker's for a long time.
I once stuck a left over speaker Motor on the back of a subwoofer. It lowered it's Qes making the box needed for it smaller. Also the midrange SPL increased yet that didn't matter for the subwoofer off course as it's not used for midrange.
Great info.
In most cases increasing the motor force near the voice coil will indeed improve performance however it's not as easy to do and isn't always successful by just adding an extra magnet to the already existing magnet,in fact in most cases that might actually decrease the magnet strength at the voice coil.
thats amazing that an addon magnet can do that
Burn holes into the center spiders to make them more flexible and also Burn holes into the Membrane into the inside between dustcap and voicecoil. Speaker will have more gain compared to the magnetic Drive and less compression. Resonance frequency will be like 5hz 😎
FEMM not taking into account the metal of the driver basket holding all the soft parts. A bucking magnet on top of the motor structure might be interesting but might need to change how the coil sits to play well with it.
Path of least resistance at play, the large neo magnet overcomes the ferrite and reduces its magnetism, in a nutshell its creating magnetic fields in unwanted areas
Measuring the displacement of the cone with and without the 'Monster' might show some better results. However, its a little hard to do so.
I am a music producer, and i love speakers too! Great video!
It would be interesting to do tests on a range of frequencies. I wonder if the low frequency allowed the monster magnet more time to influence the speed of the cone than it would at higher frequencies.. and maybe that could have some impact on the difference between the music test and the 20hz test.
What kind of amplifier would you use to power that subwoofer in your home?
If they're like my pair of HK BU-2's, each sub has it's own built -in, high-current amplifier.
I need an external amplifier
The subwoofer is inexpensive and not really highest quality, so I would probably match it with an inexpensive PA amplifier and only let it play very low frequencies. The amplifier should be several hundred watts and preferable a bridgeable stereo (or mono amplifier) stable at 2 ohms impedance. Place it behind my couch to get some kicks close up ;)
@@brainiac75 I need to add that to mine as both my BU-2's are 12in floor-firing in the front corners of my den. I bet adding another pair behind my couch would sound ...err......I mean, feel awesome when they hit!! 👍
@@kaotictouch345 Each one of my BU-2's not only has their own built-in high-current amp but each has it's own volume and Rolloff controls plus a polarity inverter switch.
the extra magnet on the speakers is used for MID RANGE and TWEETERS, and you will have a higher response on 200Hz-20 000 Hz (louder); also you should take the math Vmax excurion of the magnetic plates and the voice coil should be repositioned on the depth for frequency respose (for subwoofers the voice coil is positioned a little bit upper than full range speakers to have a higher response at frequencies below 200Hz, and the voice coil travels more mm together with the cone pushing more air waves to produce bass)
My guess before watching the video:
The added magnetic field will cause a stronger Lorenz force acting on the coil, for the same current flowing through it. However, with it being AC the current flowing through the coil is not determimed by its ohms resistance only, but mainly by its impedance. And while at zero elongation of the membrane the acceleration might be a lot bigger with the added magnetic field, at some point the membranes elasticity will push back, and this will cause an added impedance to the normal impedance of the coil, cause it cant move freely through the magnetic field, and thus due to the law of lenz, this will cause and opposing reaction, which in this case will result in a higher impedance. So after all the amplitude might get a little bit bigger with a bigger magnetic field,cause when theres no elongation at all, theres only a resistance due to inertia of the membrane itselve, and thus overall the force and thus the acceleration of it should be bigger than normal, and thus overall its pushed more, but i think this effect is tiny. But the frequency peak of the speaker and thus its sound characteristic will probably change dranatically due to it,because of the changed average impedance. Also at some point, the membrane cant flex that much anymore,and thus at this point the membrane and thus also the coil will come to an almoust sudden stop, which will cause a voltage spike, that might damage the driver. Also the membrane might get damaged.
I think its magnet fits its purpose in strength and size pretty perfectly, cause they designed it,and thus more magnetic force probably will be more bad than good, cause else, they would have chosen a stronger/bigger magnet or a more suitable coil, or arrangement. I think they choose a sweetspot, that you cant improve that easily.
Just to clarify Impedence (Z) is a combination of resistance and reactance, and this impdence is a combination of electrical and mechanical. The compliance of the spider+surround (Cms) and the Mass (Mms). As you rightly say, acceleration will increase due to increased magnetic field strength. IF the magnets were aligned perfectly, IMO they would work, I do not understand your argument for them not.
Love this!
It looked like the second test didn't have the super magnet aligned with the axis of the speaker magnet - could affect the direction of the magnetic field? I second the idea of using white noise. I also suggest you build a wooden holder for your magnet and tie or clamp down both it and the test object so you get a stable distance. Since field strength varies by the cube of distance for a disc magnet, any variation in distance will have a noticeable effect.
If it was the case where the magnet hurt the subwoofer then you wouldn't be able to have a subwoofer beside one another in a box
@Braniac75 where did you get a magnet such as this?
20 Hz test. This is probably well below the tuning of the subwoofer and maybe similar to the driver's free air resonance. Increasing the BL product of a speaker's magnetic gap can sometimes hold the cone back, providing a braking effect. Motor strength is good for providing pressure where the speaker is acoustically loaded (e.g. the tuning frequency of the port in a vented box, or the quarter wave resonance of a horn enclosure).
At both the vented box driver's combined passband resonance, and also frequencies well below the tuning, the high strength motors provide back EMF and the driver doesn't actually move as much and thus is not as loud! Technically the efficiency is not reduced as if you measured the driver's impedance, it would have increased with the more powerful magnets and is not drawing as much power from the amplifier. But when the driver is resonating in some way, you can often get more sound (time domain neglected) with a weaker magnet!
Often sealed boxes prefer a bit higher electrical Q and heavier driver cones, so the loudspeaker is free to "get its swing on" in the lower frequencies. This does ruin transient accuracy a bit, but does allow the enclosure and driver to produce deeper basst extension more loudly. With a ported box, electrical Q is somewhat a balancing act. Too low (strong magnets), and the box becomes a one note wonder, driving the port hard, but held back by its own braking effect everywhere else. Too high (weak magnets) and the speaker can swing back and forth easily in the middle resonance, but is completely gutless at driving the port resonances.
It's similar to electric motors, where weaker magnets give a better top speed (for the voltage) but less torque. If you just want to flap lightweight air around as fast as possible, sometimes the light cone and weaker magnet does better. If you want to compress air to drive a horn (which converts low displacement high pressure into a high displacement low pressure), then the stronger magnet and longer low resistance coil does better.
I know this is pretty long after the video came out, but my guess as to why the pure sine was louder when attracted rather than repelled is because with the lower field strength you're effectively lowering the resistance felt by the speaker, so it moves more air in the same amount of time with the same amount of energy.
This comes from just treating the system like a harmonic oscillator, where if you decrease the spring constant you can increase the amplitude for the same energy. However this does mean you'd expect a decrease in frequency and if this was not observed this may be a poor model
Increasing magnetic flux in speaker coil gap, increases the Fs (resonant frequency) of speaker. Efficiency of speaker below its Fs significantly low.
So try with 150-200Hz+ signal and results will be opposite. *as you expected
You're very intelligent. Thanks for the video
Cool video as always!
Can't find anything about that xzound xz12 what website do they have?
Very informative video
The Monster Magnet is not acting as a bucking magnet, as it is completely overpowering the existing internal magnetic field.
The Speaker magnet is able to pull the Compass Reading away from the Earth North, because the Speaker magnet is much stronger than the magnetic field of the Earth.
In the same way the Monster Magnet is overpowering the Speaker Magnet, in stead of creating the Bucking effect.
Increasing the magnetic field correctly will have a bigger effect on peak power rather than on efficiency (sensitivity)
At peak output the magnetic field becomes saturated.
A stronger field will saturate at higher power levels.
The size of the voice coil has a big effect on how much heat can be dissipated and therefore how long it can play at peak volume.
You can restore the Magnetic field of the Speaker Magnet, by using the Monster Magnet correctly. (Maybe even make it stronger than is was after 10 years of use)
Do a signal sweep. Every frequency will have a harmonic relationship with the amount and velocity of air the speaker pushes due to the inertial moment of the magnetic coupling.
"Careful, he bite."
I was hoping you were actually going to make a subwoofer with the monster magnet
The attracting field on low hertz pulls the coil back easier, so there would be a frequency that the pull of the coil doesn't make the sound louder.
id be curious to see what the voltage chokes looked like in the amplifiers during this
Here is not like only louder is most effect from this. Extra power in magnetic field made sensivity of system higher. But on the other side, there is also a membrane that holds the diaphragm of the speaker and it is cannot always work out fully with increased sensitivity from the additional magnet in order to give an absolute increase in sound quality based on the increase in the magnetic field near the coil. Also air pressure around membrane does not give working speaker properly if diaphragm of speaker is big and moving very fast with high power in the strong magnetic field.
Did you account for the resonant frequency of the speaker.? Maybe its around 20Hz. Perhaps a higher frequency may be more accurate.
Great and interesting Video as always! 👍
Thank you, JustPyro :o)
@@brainiac75 I think knowing the resonant frquencies of the speaker would help. Put a DC current through the voice coil, and then turn it off, and see how the speaker vibtates as it returns to equilibrium. A microphone connected to an oscilloscope, and perhaps some software like Sigrok PulseView may help. I would guess that in an ideal speaker, you should see a damped sine wave...
Once you know this, repeat the experiments with tones at or near the resonant frequency(and their harmonics), and tones far away from the resopnant frequencies.
20Hz is such a low frequency that it is boosted via bass reflex ( the hole on the left side of the box). It makes sound when the speaker membrane is retracting (so it's pushing the air out of the box) thats why monster magnet in an attractive position helps it. (At least I think that's why)
Question: Can blood be affected by magnets, or is the iron in the blood bonded in such a way it's no longer magnetic?
Follow up: If blood can be affected, how much more powerful would your magnet need to be to have any noticeable affect on blood flow?
I have a video about that. Search for Monster magnet meets bl00d... And thanks for watching :o)
I was going to reply that he's already tested that idea. It's an interesting video!
That sub is 500wrms.. dvc @ 4ohms..thats gonna need a lil more than 60 watts at 6ohms. Around 150-175w at 4 ohms would give you a increased out put , in which the subwoofer would be easier to notice the difference
i love how the monster magnets are still not devided into 2 its been 2-4years i guess
i always heard that adding a magnet to a speaker will add more bass which might be it
sounded slightly quieter in normal music yet louder playing 20hertz
Some subwoofers (Most notably models made by Digital Designs) can have an option to have a ring of neodymium fitted on top of the ferrite motor, to help increasing magnetic force in the pole-gap. This will in turn increase the efficiency of the subwoofer, since you can achieve higher output with less input power.
There are also subwoofers that have full neodymium motors instead of ferrite ones.
That might enable more amp power, but the main bottleneck on most subs is cone excursion (how far it can move), so that would achieve very little for most systems.
@@engjds Typically neo-subs are designed for high excursion. Like the Sundown Nightshade series for instance, with its 4" mechanical limit.
@@Skarfar90 As long as you test for it not going over excursion you will be fine, but I would just turn up the power to compensate and ditch the magnets, unless efficiency is really important.
A speaker is very complex you have the stiffness of the mechanical (spider and surround) plus the stiffness of the magnet (or how the voice coil interact) how they interact determines sound quality and loudness. With the super magnet you probably have an asymmetric cone movement (moves in one direction more than the other) as you unbalance the speaker's motor. This could lead to the extra dB as it gets pushed out harder than in the other setups. Just an edumacated guess based on what I know about how speakers work.
Just a layman interpretation here: Stronger forces input don't necessarily mean more force goes into the vibrations - you'd need both stronger forces AND a bigger or more robust vibration chamber in concert to have that work cleanly. Otherwise, the vibrations would 'step' on eachother more, converting to other forms of energy (heat, deformation) instead of going into the air as vibrations.
It's like slapping on a small drum. Within a range, the drum will react to stronger slaps with more sound, up until a limit. Approaching and passing that limit, you start just changing the pitch of the sound without increasing volume, then you start just damaging the drum, or having more of the energy just making the drum 'hop' after you hit it.
But make a bigger drum, and then you can raise that limit up further, depending on the materials used.
How about you try using a panel big enough and shaped to take the vibrations of the big magnet, and turning THAT into a speaker? Might need a friendly sound engineer, like the kind that set up big churches to help with that though.
Thanks for the input. I believe I may have messed with the Thiele/Small parameters of the speaker with the external magnet... Measuring at only one frequency (20 Hz) really only tells you something about the speaker at that frequency. I may need to revisit with white noise and some spectral analysis of the output. Much to learn for me yet :D
Stronger magnet means more to push against = speaker handles more power before being overwhelmed. Did you test to see if the speaker would handle more output with the additional magnet added?
Well since you left almost 1/2" on spacing due to the box. You should have removed the subwoofer from housing.
Also my car subwoofer picked up more when the magnet was near