Why Isobaric Subwoofer? What it Is And How it Works
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- čas přidán 17. 09. 2021
- The bottom line: use isobaric when it makes sense. If you already have the drivers (like I do) and are willing to use two in order to cut the box volume in half.
Unstated in the video is how important box volume is for speaker design. The box volume determines the tuning and how flat and extended the frequency response will be. Therefore, putting a driver that's designed for a 200 liter box in a 100 liter box will give you a very poor response. Being able to cut that box volume down to something more acceptable is the key reason to use two woofers in an isobaric arrangement.
Regarding efficiency and power, isobaric reduces efficiency by 3db, but the more modern woofers that are designed to work in small boxes have that efficiency drop built in - there's ALWAYS a tradeoff - no free lunch - to get more of what you want, you have to give up something to "pay" for it. For isobaric, it's a drop in sensitivity for a reduction in box volume.
That drop can be regained by wiring the drivers in parallel, but then you need twice the power to get the same spl. While that sounds like a major drawback, increased power requirement translates to increased power handling as well, so possibly a slight advantage for something like a subwoofer.
Also amplifier power is cheap today.
I know, I'm using the terms "sensitivity" and "efficiency" interchangeably. There's a difference, but not one that really makes a difference for a casual talk like I did here. Focus on what's important instead of searching for details to nitpick about.
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The bottom line: use isobaric when it makes sense. If you already have the drivers (like I do) and are willing to use two in order to cut the box volume in half.
Unstated in the video is how important box volume is for speaker design. The box volume determines the tuning and how flat and extended the frequency response will be. Therefore, putting a driver that's designed for a 200 liter box in a 100 liter box will give you a very poor response. Being able to cut that box volume down to something more acceptable is the key reason to use two woofers in an isobaric arrangement.
Regarding efficiency and power, isobaric reduces efficiency by 3db, but the more modern woofers that are designed to work in small boxes have that efficiency drop built in - there's ALWAYS a tradeoff - no free lunch - to get more of what you want, you have to give up something to "pay" for it. For isobaric, it's a drop in sensitivity for a reduction in box volume.
That drop can be regained by wiring the drivers in parallel, but then you need twice the power to get the same spl. While that sounds like a major drawback, increased power requirement translates to increased power handling as well, so possibly a slight advantage for something like a subwoofer.
Also amplifier power is cheap today.
I know, I'm using the terms "sensitivity" and "efficiency" interchangeably. There's a difference, but not one that really makes a difference for a casual talk like I did here. Focus on what's important instead of searching for details to nitpick about.
Good day.I know all that there is to know about the Isobaric design since< the early 1970's when I became an audio enthusiast .It was an ingenious idea in the 1950's and was a great way to reduce box volume.However time has marched along by leaps in technology .Today it makes no sense to build an Isobaric box even if you happen to be sentimentaly attached to four junk woofers that happen to be lying around.
@@1997inspire These aren't junk woofers. Suggesting that they are makes me question how much you actually know about the topic. Maybe there's more that you could learn if you went with the idea that you don't actually know it all.
@@1997inspire Since you know everything there is to know about isobaric enclosures tell me one benefit you will get with a clam shell vs stacked configuration? Hint, also a benefit no other cabinet design affords, therefore negating your entire comment?
Make a video, we need em.
@@brentb5303 Oooh, oooh, pick me!✋
I had no idea what they were. And now I do. Thanks John for learning me something new. I appreciate it.
Another important advantage of the isobaric box is that in the opposite coupling of the two drivers, the harmonic distortions caused by the movement of the membrane and its deviation are canceled.
I’ve debated this with people. I swear the bass just sounds better to my ears with an isobaric enclosure. It’s just plain physics. The two drivers are working together to maintain linearity.
And paralleled, the induced CEM force opposes itself ...
This is my favorite sub type, i have been making this the sub for 20yrs
"I added a model" -presents a hottie... respect good sir
I am learn and very interested in the subject matter at hand I look forward to these videos with great anticipation.
Thank you! I have seen woofers like that but had no idea how they work.
my old dual 6.5" iso cranks hard. tune the in and out ports to 25Hz and 70Hz and it fkn rips. Kids need this knowledge post acropolis. thanks John :)
Could you share your build please can’t find much info on YT. I am actually wanting to build a isobaric bookshelf try to get fullrange instead of a tower
@@anandshah71 you need bassbox an old piece of software from harris technologies or find an article from siliconchip (an australian magazine) that had a really good design with dual 6s.
Thanks for the model for scale, and you should check out the plans on pbn audio on the Dayton Audio Xenia speaker which has the 6 LF in a isobaric per side
I used to use isobaric in band pass loads when I where young. I was sub & sat mad back then.
I was in the same boat, but took a different fork in the river. I used my 4 old 12" woofers to make twin open baffle subs. They sound amazing with music, or movies and take up very little space.
Luv this video, but I like how he shows size comparison. But I heard for two e as small and twice the cost I can put on a book shelf😂😂. Informative video luv it
Cheers for this, great explanation.
I appreciate you sharing this. I am going to through this out for thought, what determines the spacing between the two speakers, and what if you were to slightly pressurized or create a slight vacuum in that chamber? I really came online to see if a bass player could incorporate a powered subwoofer with his bass amp and speakers to increase the lows. Because it seems like I have yet to find a bass amp that produces the same Hz bass playing that is recorded in studio and then played back through a stereo with subwoofers on a CD or any recording device.
1. By putting them in series back-to-front you're losing out on the second most important part of isobarik coupling. Mounted front-to-front or back-to-back, you can decrease the odd-order distortion components by a quite significant margin. Odd order distortion is greatly increased by driver nonlinearities that are different in out-stroke compared to in-stroke - by using two identical drivers where one faces "out" and one "in" from the box's POV, those nonlinearities are partly balanced out. That's why most old professional or consumer grade isobarik solutions use the drivers with the fronts facing each other. It maximizes the coupling between the drivers (minimizes air-spring effect), and lowers THD.
2. Low-Q EQ does still do a VERY good job in the lower ranges. You'll see VERY close to zero difference in distortion and compression when you compare a single driver EQ'd to give the same FR as in the same box where you had a "passive" isobaric setup before. And you won't hear any difference either.
3. Multisub setups are several times more space-efficient and give better results (on flattening in-room bass response) than ANY kind of elaborate room treatment in small-medium sealed rooms. Removing room-modes by actively REMOVING them is simply put more efficient than trying to mitigate them passively on second bounce. The room still has to take care of reflections above the modal limit frequency in a good way, but below?
1 - the reduction in distortion isn't significant. It's there - it exists - but it isn't enough to make an audible difference.
2 - too much faith in EQ.
3 - too much faith in multisub. Multiple subwoofers don't "cure" room modes and need a ton of EQ to work properly. They aren't the panacea they are hyped up to be.
Nothing equals treating the room - nothing. The more treatment it has, the better the system will sound.
It may be worth your while to experiment with parallel vs series wiring with your isobaric setup because although a lesser ohm load will merit more power gains from your amplifier, wiring in series will increase the bl factor of your subs.
Yes!!!!!!!! Thank you for posting this!!!!!
Good stuff man.
Wow great video.
Thanks for sharing.
If I did it I would experiment with a slight difference in woofer output by resisting one by like less than one ohm. And listen to how that may affect the bass. Also have a slight difference in added weight on the woofers. Or if none needed, just weight one woofer very slightly with Blue Tack, and hear how the bass sounds. Sound nodes are ridiculously complex and that is why fine tweaking a bit like this works (or fails miserably). You will hear the difference by such a small tweak.
for example a single sub will need a 5liter box. if I put another one in an isobaric setup but keep the box size. how will it affect the sound? specially the frequency?
Btw, it's not limited to 2 elements, you can assemble several in order which cut the needed volume even more. For example i had four 6,5" bass elements which optimum sealed enclosure is 30L / element. I did built isobaric system, four in line in 8L net volume. Result is outstanding, it goes to 26Hz with ease. Of course the maximum spl is less than four elements in traditional system, but enclosure would be 120L then 🤣. I will most definitely build more systems like this!
Interested ! Please see my comment above. Thanks
1:53 What differences in sound can be expected when the chamber is unsealed or open? Would this potentially enhance the bass response? Your assistance is greatly appreciated."
Think i could get good resualts using some cheap woofers like some 6.5" pyle gear componets?
I wish that you lived in Virginia, so that I could share with you my speaker designs.
What is the main box behind them is it sealed also or ported ? If it is ported do you port for one or from the box being smaller does the port get bigger ? Like would you do this because you have to 1500 watt woofers and a 3000 watt amp? I have stuck a pair of 10 inch in a I don’t know if it would still be isobaric but they sound like a 15 or a 18 I got one sealed out of a 1 cubic foot box playing face to face with .7 cubic feet between the pair the other one is playing out a port on the backside of .7 cubic feet about 22 sq inches of port around 24-26 long and it’s a square sealed box with a tube box for the sealed chamber and the ported also there one positive to positive the other is negative to positive on one channel of my amp they really sound good like this there very low and create accurate bass with out the sealed box and arranged back to front there not as low and sound a bit destorted at the time they were in parallel wiring and I had played them into the sealed box like that but decided to turn the one around when back to back they didn’t sound as low and they couldn’t handle as much power now front to front with .7 between them sealed real good they sound better also wired series now I was thinking of doing some 15” woofers this way and see if I cud get the lower sound from them ! Maybe they might sound like 18s or 22s ? But I don’t have a round box guess it wouldn’t hurt to be all square oh yeah the 10’s required .6 seald and 1.4 ported I just though it together to see about the isobaric thing to start ! But then looked and had a sealed box and thought wounder about double sealed and single ported ? Just if any one would know is this just a no name or order or do I have like a 4 th order isobaric box or what would this be I don’t know we’re to begin? Thanks for the info about this everything is so great about audio and seeing what works and what don’t then stumbling on to new things and kinda adding your own twist to it !
Yes. I agree and approve 😁.
dude i love isobaric boxes. can you make a box with an isobaric and a single driver ? i wanted to get better lower (under 50hz) end and mid end (above 50hz) bass
Where do you put the cutoff frequency for this arrangement? Also, what does it sound like when a pure sine wave sound gets into the frequency range where the wavelength of the sound matches the distance of the speakers. Should be around 1-2kHz in your case. Or half the wavelength. Should cause some destructive interference between the two speakers. Probably sounds pretty awesome if the frequency is just slightly off :)
Hello, I really appreciate all comments about subwoofers and specially the Isobaric mount. I must relate this part of my experience because I think that as everybody You underestimate the real bottom of the signal: Modulation. Let me try to explain ! When analysing (with any kind of method) the audio waveform, You see appear some lower frequencies that are stimulated by the modulation of the signal . Basically, the Fourrier analysis explain this, also logic makes easy to understand that when You hit the Knob in 1 second revealing a 1kHz signal, You compose a modulation which is made of 1000Hz, 1HZ and 999 Hz and 1001 Hz ... As a signal establishing itself in acoustic pressure takes a small period to exist, You have a modulation. As a Choir sings an A, the harmonic composition of the voices create a modulation which has nothing to see with the A note. When a group of strings plays a chord, with vibrato on every instrument, You get the feeling to hear something fully tuned, though some sub harmonics have nothing to see with the original Chord ... and it is beautyfull ! To hear this is natural to our ears. Imagine the modulation there is in a musical (classic orchestra ) Final à Tutti with the great orchestral Drum (14Hz) !!! .At that moment, there's a huge modulation of mainly the reverb. Can You imagine reproducing that moment WITHOUT the 14 Hz ???
This is why I consider that the Sub system should be targetted UNDER 30 Hz ( this freq is very well tuned in port systems) and this is why I'm interested in Isobaric cone to cone system, at the rear or sides of the main enclosure. Two main advantages: as You described very well, the box may be half the size, and (nobody dares speak about this) the (in french) force contre électromotrice " counter current" is opposed if parallel wired. And it should really help the Amp !
Finally, with the use of modern speakers with -double Magnet, long throw, long Xmax with fabulous suspension moving small mass for quick response and multiple low cost speakers, and also very affordable DSP that emulate all Your wishes, I think that I will keep a sealed box option... with 4 speakers in each... to place UNDER the usual sub, reproducing only the played notes ! (though C zero is 16 Hz !!)
If You've read me so far, don't hesitate to react ! Thank You for the post and this interesting subject.
Well said.
If I have a dual subwoofer , and get one identical subwoofer and make one isobaric . Will it damage the other woofer by itself ? As they will all be in the same box/enclosure
I have isobaric subvoofers. The dB is less at 100 Hz. But that's not any problem at all. I have a increase of output in the deep Regions instead. I use active filter 24dB around 80Hz . The sound quality is outstanding. You can't compare the clean sound with any single woofer.
In the 90’s isobaric was a popular configuration in Car audio Competition and higher end Car Audio
Yes, that's how I'm aware of the configuration. It was definitely trending in the mobile world back then. But that was really before manufacturers started optimizing subwoofer design for small boxes. Iso was a good way to get these woofers into manageable enclosure sizes, especially in a competition car where the increased cost of drivers and power wouldn't have been as big of a factor.
I just got a pair of Isobarik Saras here recently. Heard them before?
"For scale." Sure John. I see you. xD
I don’t know if these comments are still being watched but I have a question. Can I use an iso-baric setup to replace a dual coil speaker?
Isobaric is NOT push pull subs right? Like the ones from m&k & perlisten? is the 2nd driver in push pull setup in 180 degree out of phase?
I love Isobaric boxes. They do require a lot more power to get the full benefits, but they deliver a much punchier and solid sounding response. They sound more like a sealed box than a ported box in that aspect. For anyone looking for new subwoofers, it's important to learn about the Thiele/Small parameters, and at least get a basic understanding of what you need, rather than what you want. It's really beneficial when you know what kind of response you want, the physical limitations, and enclosure type you want. Instead of blindly buying a sub you are told is awesome, you can compare and look at the numbers to find out what you need, than what is sold as a dummy light. (like in a car dash dummy light).
Personally I'd just use a woofer with enough motor force to drive the box size I need. Probably back in the day, the motor strength on available drivers was weak and you had to have two pushing in tandem, or build a bigger box (which is a more efficient use of the woofers if you have the space.)
Isobaric loading: small box with 2 drivers combining their motor force
Is equal to 1 driver in proper size box as far as performance/amplitude
Interesting. The speakers I bought when I was in high school had an active woofer with a passive woofer below it, the passive one being driven by the cabinet pressure from the active one. When I think about it now, it makes me wonder if there was some phase cancellation between the two or if the frequency of the larger passive cone was different enough to avoid that.
The passive radiator acts like a port, but without a port.
@@IBuildIt The certain Philips boomboxes used Woox Radiators: Dual accordion-like Radiators, back to back, about 1" apart. The sound was completely different from a typical tube Ported speaker. The bass was deep, powerfully thumpy, and yet didnt have that artificial sounding farty bass... (which happens in ported speakers at louder volumes)
It was some of the best low bass / sub effect sounds, without an actual Sub.
Personally I find most subs muddy music, so I tend to avoid them unless its merely for movie effects. Even then, I prefer an actual Bass Shaker Transducer setup. You feel 10x more bass, without the need for mega volume level + high pressure air movement.
It is education I didn't know I need, but education nontheless.
3:12 Can you have the model show up in person and give us her explanation of isobaric in the next video? LOL.
On first view, I thought it was Brooke Burke, but now I'm not sure.
@@jodyburton0351 100% same exact thought. Not her though when I saw the small bewbs.
Have a ?... I watched the vid and you mention isobaric taking a smaller box. Does that mean smaller than the box would be with both subs loaded normally, or smaller than 1 sub itself would require. I can't seem to find a definitive answer. I know this is an old vid, but I happened across it searching for an answer.
It cuts the box size for a single driver in half. If one driver needs a box that's 50 liters, then an isobaric box would be half that size.
Slightly altered joke from Predator:
John, to his girlfriend: "I want a smaller box."
John's girlfriend: "Me too, mine's as big as a house!"
Would this work for modern woofers too? Something like a pair of GRS 12SW-4HE 12"? I'm trying to build a small enclosure that with an f3 around 20 HZ. If this configuration doesn't work, do you think passive radiators are the best option?
What was your conclusion? Sounds like I’m looking at going a similar route to you.
@@zackobrien2223 i ran out of time while finishing the RLC speaker builds (new baby daughter) so I just bought a speedwoofer ha. I'd love to hear your thoughts and experience with your build.
@@Nickporter17 Congrats on the baby! I hope that setup is treating you well. I certainly will! I am fortunate to have an audio friend in his 60's with a ton of experience with cabinet building and DIY. So, I will be leaning on him heavily. Ill be sure to post here with my results. :)
@@zackobrien2223 thanks! Have fun with it!
I like your "scale model" lol
But you halve the useful Sd of the transducers. Admittedly has a smaller Vb but it has more lose than win
Thought Experiment - Make two identical size boxes. Purchase 5 identical woofers. Place one woofer in the first box, with the other 4 going in the second box arranged as two isobaric pairs. Both with model exactly the same. The box with 4 drivers will electrically handle 4x as much power, and the output will occur with half the speaker stroke.
All of that said; the real question is how much is SQ impacted? Do Iso's follow the signal tighter? I personally think they almost have to sound better / tighter / cleaner.
Clarification - By identical boxes I mean in terms of airspace after driver displacement. Obviously packing 4 drivers in a box is going to consume a lot of space, thus growing the enclosure size.
I want a smaller box so I am thinking of something like this.
Can you do isobaric with one dual voice coil driver and a passive radiator in a clam shell?
Probably sound crappy..better to put your radiator away from your driver
It by definition wouldn't be an isobaric design. You need two drivers working together. Passive radiator is not dissimilar to a ported enclosure. A port uses the energy inside the enclosure to essentially create an area of air that makes waves like a speaker cone or passive radiator. The difference would be in how the energy is transferred. More controlled in passive radiator configuration but less efficient since the mass your using to create the additional sound waves is obviously much greater than port air.
@@brentb5303 yes, I was trying to discourage him from doing anything silly.
I'd like to know what kind of music are you listening to with those big ass speakers?
If you ever look at his tee shirts you would know its Van Halen, Rush and similar bands.
.. didn't see the box size ... got distracted
efficient, small and powerful, you can only choose two lol
Why not run the woofers back to back but out of phase? Push pull.
Heck yea
No replacement for displacement
John: hold my 10mm socket
That last line is one I can't get people to understand. If you have something, you can take advantage of it. If I had a nickel for every person who said I was using the wrong material or that I was 'wasting good stock. I'd have a bag of nickels I could hit them in the face with.
You missed an excellent opportunity for clickbait with the model!
I thought the exact same thing. It would have been funny
Why not build an acoustically transparent screen and hide huge boxes behind the screen like a real movie theater thats what I'm doing :)
Because I'm not building a home theater. It's a 2 channel listening room.
@@IBuildIt but let’s be real you said you watch shows and movies down there how many hours are you going to listen to music only.
@@AllMyHobbies I listen to music up wards of 12 hrs a day. It pays all day in my shop
@@KipdoesStuff i hear ya but you don't sit in a 2 channel listening room for 12 hours a day
Every night since I started using the room I typically listen to music for more than half the time I'm in there. Take last night for example: I started watching a one hour show around 9:15. I finished that then listened to music until after 12.
If you are not into listening to music then you'll probably think that's boring. But for someone that is, the time flies.
Also a treated room makes a massive difference.
The motor and basket of a woofer is ugly?
How dare you!
John why are you making socialist barrack speakers?
Elaborate
@@xmachine7003 you wouldnt get it