The Isobaric Subwoofer Mockup Build and Testing
ฝัง
- เผยแพร่เมื่อ 2 มิ.ย. 2024
- Watch the first video in this series: • Dead Simple Trick to g...
While I almost 100% trust the results that the modeling software give, there's nothing like actually building one to test. This was quickly thrown together with various scraps of plywood and works as predicted.
This will be the lower section of my new main speakers, but I'm not entire sure how that bottom section will be made, yet.
Original concept (as shown in the video) is to have the outer woofer facing out, forward. I may change that to a clamshell design and have that facing backwards. Also shown is the vent facing forward, and I will likely move that as well.
The drivers are 12" custom made by Eminence. T/S specs:
Fs - 27.9
Re - 7.4
Qms - 8.9
Qes - .5
SD - 510cm^2
Vas - 126 L
Xmas (peak) - 9.8mm
Le - .84
You can help support the work I do in making these videos:
Project plans for sale: ibuildit.ca/plans/
Join the ibuildit community on Loacals: ibuildit.locals.com
Support this channel on Patreon:
www.patreon.com/user?u=865843...
My main channel:
/ jpheisz
My "Scrap bin" channel:
/ ibuilditscrapbin
Website: ibuildit.ca/
Facebook: / i-build-it-25804801424...
Instagram: / i_build_it.ca - แนวปฏิบัติและการใช้ชีวิต
![[TH] 2024 PMSL SEA GF D2 | Summer | ร่วมส่งแรงใจ เชียร์ไทยไปพร้อมกัน](http://i.ytimg.com/vi/dN2gLsCJ0T0/mqdefault.jpg)
While I almost 100% trust the results that the modeling software give, there's nothing like actually building one to test. This was quickly thrown together with various scraps of plywood and works as predicted.
This will be the lower section of my new main speakers, but I'm not entire sure how that bottom section will be made, yet.
Original concept (as shown in the video) is to have the outer woofer facing out, forward. I may change that to a clamshell design and have that facing backwards. Also shown is the vent facing forward, and I will likely move that as well.
Dang !! You look just like my brother i lost last year on labor day i am blown away !!
Subscribed
Very cool, John. I love how your room is turning out! I’m in the process of “filming” my home studio makeover series. It’s been 12 years and needs some serious attention. Boy I’d love to get my grips on a pair of JBL 4355’s or perhaps Urei 815’s 🤤 😭
Like to get my hands on a pair to sell! Too big for my room, but I would give them a righteous test drive before parting with them.
@@IBuildIt Waaay too big for my room too! There’re so big, I wouldn’t even notice the issues with my room ;)
Always enjoy your vids! In the last 27+ years of my professional car audio career I've built numerous isobaric enclosures for high end SQ systems and am quite impressed with the musical accuracy. Additionally the benefits of the smaller air space required for lower FS combined the increased power displacement is astonishing ...although using fill - in my experiences - results in a very dry and less than natural bass response that becomes less predictable. My best results have been when the subs are facing each other with little to no airspace between them (1 ran out out phase from the other) with the vent firing into a reflective surface.
Hey John, former Dolby guy here (in the 90’s when all this home theater stuff was taking off). In Dolby licensed products, “full range” refers to the bass management of the front speaker channels. Unlike theaters, Dolby requires a crossover to redirect LF information to the subwoofer so that the front speakers can be smaller (more convenient for home use). Turning “full range” off leaves the LF in the screen speakers and the subwoofer only receives the LFE channel instead of LFE + the LF from the screen channels. You’ll find nearly every “sub out” to have a LPF except in a minority of specialty cases.
That's understandable, but most or all sub amps have a low pass built in as well, and the two combined can create a dip in the response at the crossover frequency. That dip is responsible for at least some of the issues I blamed on SBIR in a previous video.
My preference would be to have control over both independently - the sub output and the front channel output, not both combined. Too bad that's not an option in the receiver I'm using.
@@IBuildIt Yea. Exactly. What you have is the minimum Dolby licensing requirement to support bass management in this way. Bypassing it (the LPF) is usually found in high end products.
Before even watching the video : The image on your intro is great ! that looks good !
Cool to see the actual and calculated side by side.
Also very cool to see that they actually match! Thanks for watching, Greg :)
Its always shocking to me to discover the infinite depth of any well of knowledge. I am over here from your woodworking content and I'm blown away by how involved this second hobby is/can be
I have been at this for most of my adult life and I can tell you there is nothing more complicated than a loudspeaker...That's what nuts like myself love about it!
@@russellanderson746
Indeed, absolutely right.
High performance loudspeaker design is a 𝙢𝙪𝙡𝙩𝙞-𝙙𝙞𝙨𝙘𝙞𝙥𝙡𝙞𝙣𝙖𝙧𝙮 𝙚𝙣𝙙𝙚𝙖𝙫𝙤𝙧 like few other pursuits.
Physics involved incorporates acoustics, mechanical and electrical engineering, electronics systems, magnetic designs utilizing ferrite, neodymium, and materials science including everythingfrom paper, to beryllium, titanium, aluminum, plastics, Teonex, mylar, and polyester.
Additionally, the physical construction incorporates wood-working, adhesives, addressing acoustic and panel resonances, constrained layer damping, baffle step compensation, and diffraction effects, driver center to center distances and proper acoustic summation and propagation.
The list goes on into psycho-acoustics and the manner in which we experience sound... ie., we don't experience sound the same way a measurement mic captures it.
A successful, high performance loudspeaker design incorporates all this and much more.
There's also the artistic component, ... the speaker as an object of art and expression.
I had completely forgotten about this type of design.
I've been in that car audio and home audio since their 80s.
I've never actually had the chance to make something like that, nor do I think I've ever had the opportunity to listen to one.
these videos are always very informative... I learn a lot - thanks for doing these, John!
I do enjoy these videos and hearing the theory behind building a speaker box. I will be following the series.
All my respect man for what you do ! Always in the right way and well explained !
Wish you the best !
Really enjoying this project, you have a natural ability to put things across ..👍
i built a few vented isobaric subs for my soundsystem a few years ago. tuned the vent to boost the super low bass (-20hz) - great for watching movies or listening to reggae music :) enjoying to watch these audio projects!
Fill changes the effective speed of sound inside the box, thereby influencing tuning, is how I remember it from the literature, it's been a while though.
True
As well as proximity of the damping material to either the driver backside, or the vent... it all matters.
So beautiful especially for being a prototype
looking promising!
Way above my head, but very interesting stuff.
I've been audio guy since high school, I'm 49 now... Built 100s of systems over the years in car, home & pro audio... Mixed as well for a cpl well known artist...
All the modeling software etc is really only a tool to get ya close to what your ears perceive as that perfect sound... Everything changes in room as well as after the subs are fully broke in or let's say you add a big comfy chair lol...
Back in the day we never had all this software etc. We did everything with pen paper & calculator. Then used our ears to "tune" anyhoot all that matters in the end is what your ears perceive as that perfect sound...
Diggen the videos John. Keep up the good work..!
i prefer the back to back arrangment. cancels out the nonlinearity (mostly) of the cone moving "positive" or "negative" . and allso the nasty stuff of air passing by the frame of the speaker, the spider etc... is kept isolated in the coupling chamber. yess it takes up a bit more space and maybe the coupling chamber is a bit larger this way , just consider it some minimal added mass.
The best bass performance in musical terms I've ever listened to came from isobarik loaded speakers, all from Linn speakers. Not many companies still sell isobarik loading speakers today.
Video quality was really nice. New camera or something? Either way, great video!
Very interesting thank you.
Thanks for sharing.
Have an older duel 10s sealed isobaric sony home sub 250 w, very underrated sub. Tight deep bass. For the money not dissapointed.
Huh interesting setup never seen or heard anything about that before
Amazing stuff, i recently bought a 4 2.1 soundbar that has a ported sub which delivers a an overpowering bass. It offers bass control the bass haa some boomy components. Any suggestions to kill the boomyness? Like stuffing something in the sub port?
Very informative...
Isobaric works most efficiently when the speakers are face to face (less air bouncing between the diffusers). Do not use such a low port setting, there is nothing to listen to, and you get more problems than perceived advantages. 75-80 hertz for midbass and 40-45 for subwoofer. It is not the frequencies as such that are important, but the correct distribution of powers and pressure levels.
What about damping of the drivers below the port tuning frequency of e.g. 40Hz?
I'm curious about the phase relationship of those two speakers working together. Will you need to adjust the phase so they are perfectly in phase and working together or is that not a concern.
Do you feed the same signal to both speakers or are they two different outputs from the amplifier.
Very interesting. Thanks John
No phase issues. The drivers are wired together in parallel from one source.
At these frequencies, the sound wavelength is measured in meters. So technically, there will be a VERY VERY VERY small phase mismatch, but it is so small that it can be assumed to be zero. For example, at 20Hz the wavelength is around 17m. Let's say John spaced the drivers 20cm (8") apart. The error would be around 0.1%... (I think I did the math right...please correct me if not).
@@CDN_Torsten you are assuming that the rear woofer is producing sound waves independently of the front woofer. It doesn't work like that - only the front woofer is producing waves. The sealed airspace between the woofers couples them together so that they act as one unit. The smaller the space, the more effective that coupling (or connection) is.
Think of the rear woofer as just a motor that's working with the motor in the outer woofer.
I’m probably not the only one wondering, but have you done a video talking more about the design spreadsheet and the testing equipment (sound source, microphones and software)?
Sweet!
Nice and concise! What about resonance of material used . Density such as particle board has might also influence the build. I'm getting older and hearing loss affects my attitude . LOL.
I remember using folded horn in developing speaker boxes. That was transistor moving into IC days. LOL! No calculators and 'puters!
Since this is just a mockup, material density is not a concern. With that said, that's something that is generally overemphasized by a lot of speaker builders. Large panels need to be braced, but there's not much difference in the density of the common materials used.
3:41 Why not put the drivers face to face? You can just put a bit of grill cloth over the front so you don't have to stare at the magnet.
Very interesting, thanks for the science behind the construction of the speakers, how do you connect them both together, parallel to get 4 ohms ?
Parallel, but they can be wired in series.
Are both drivers wired in phase or out of phase
@@robertspringer9477
Both drivers need to be physically in phase, ... regardless which direction they face.
Did you ever get a chance to build the final cabinet?
Bro I have a 12inch subwoofer I wonder what is the size of the enclosure box hole and 6inch subwoofer hole from enclosure box
I wonder if the isobaric will help with combing
I'm finding this series very interesting, even though I don't understand much of what the graphs or the nomenclature mean.
Have you followed any of Mark at Car Audio Fabrication’s home theater build? That is his current project too.
Have you ever tried Flat panel speakers?
Nice video ! But can you please briefly explain how the second woofers sound wave can get through the front woofer cone material to double the sound output from both of them? Thanks 😊
the point is not to get more output but more bass extension, they both move air like one woofer does.
think if it like acoustical dsp.
for anyone making subwoofer, just make a normal sealed dual driver subwoofer, add dsp to get deep bass. much easier and more output. you need dsp anyways for whole system so why not use that for the subwoofer also.
@@sudd3660
You're right, you don't get more output, but you don't get more extension either.
The only product of this approach is a requirement for half the box volume.
Nothing else.
is it not posible to use 1 subwoofer with a longer pole in the middle so that you can attach two cones to one subwoofer, instead of driving each cone individually ?
Can it also be build with the magnets facing each other?
Did you finish building this, John? I can't find it.
So when you measure the driver itself it loses dbs at the frequency the port is tuned to but when you measure the port you gain dbs in that frequency so when they work together they even out? Am I understanding that correctly?
Yes
It's not all additive and in phase, but most energy sums in the right direction... filling in the freq response.
At port tuning the driver's excursion reduces dramatically and the port is primarily responsible for acoustic output.
It's a compromise.
You're leveraging for that extra output at tuning, ... at the expense of a faster roll-off below tuning.
(Ported systems rolloff at 24dB/octave, sealed systems roll off at 12dB/octave)
4:18 Interestingly the resonance-frequency drops when you bigger the isobaric volume (the volume between the chassis). So you have more benefits by optimizing the airflow between the woofers than by minimizing the volume. 5:17 Ported enclosures should contain a less damping stuff as possible. It only reduces the energy you can get out of the port. May you cover the walls with convoluted foam (if needed adding a layer of polyfill) to damp the mids. But be sure to let the space between woofer and port free of any stuff. Can't wait to see the final Box ^-^
Adam, are you saying spread the woofers further apart in the connecting sealed chamber or am I totally misunderstanding you?
@@colbylaro9361 If you mount the speakers membrane to membrane there can be a benefit in increasing the volume between the membranes (but also in the other two verions).
@@colbylaro9361 I am not Adam
So what are you saying?
@@djambush360 jambush
🟦.... I would have made the enclosure out of the thickest-walled PVC-pipe of the proper diameter that I could find, It's very easy to mount the drivers into a PVC "End-Cap".
I think it was Pioneer that used a non powered dummy woofer face to face with a powered woofer in a 80s car stereo plastic cabinet, not sure if it was ported, if i remember it sounded pretty good and was fun tearing it apart to see what was inside. Please use high density particle board for your enclosure and wool batting instead of pink.😮
Test it sealed, looking at the in room response, I’d expect a sealed design to give you a flatter in room response.
Definitely worth a test.
It would look flatter because the response from the sub would be falling below 45Hz. When combined with the speakers, the in-room response is actually very flat.
The idea that fill "adds" volume is a long since busted myth, particularly in a ported enclosure. In a sealed enclosure it will slightly lower Fs as a larger enclosure but this is done by way altering the Q. This is not the same as an actual increase volume which also has an increase in sensitivity. There will be some benefit in reducing the port issues as you have shown.
I've done measure with and without stuff in ported design and the result are very different.
The stuffing helps port resonance as quell as "virtual volumex inside the box.
Please read some articles about that and do some tests (in the right way of course)
Unibox predicted the results pretty much bang on, and it accounts for the extra volume the heavy fill provides. You can see it calculates the Vb as 115 liters.
I've heard a couple of speakers builder here on TH-cam say it's especially useless for lower frequencies. But on the other hand, it wouldn't hurt either.
@@IBuildIt I will add here that I have always read that it is very important to make sure that the pathway between the diaphragm and the port in a bass reflex design be unobstructed by fill....You may already know this, but if not it may to some degree explain the divergence from the Unibox(a progam I also use and love) predicted response. I am really enjoying this build and all of your work on room treatment and design. Thanks for sharing your findings and skills!!
@@russellanderson746 the "pathway" between the port and cone doesn't need to be clear, the mouth of the port needs to be open and unobstructed. The box can have plenty of fill as long as it doesn't block the port.
As for the divergence, that's little more than a rounding error. As in, if I'd rounded over the port opening on each end, that would have shortened the port to the point where they would matched perfectly. As it is, it's nearly perfect anyway, or as good as I've seen.
I think mdf is the best wood for density as you can hear the wood on a speaker in the audio signal like the bloom etc.
Being the subwoofer should only see 250hz and down for non directional bass response that 450hz bad tone from port would never be in there if crossed over at correct point
🟦.... Rather than using any kind of "fill" for the cabinet, IMHO you'd be better off covering one of each of the opposing internal surfaces (One directly opposite the woofer and two connected sides) with a 1/2in thick layer of Rockwool).
Next step should be isobaric OB. I'm watching Your videos in the wrong order.
what music do you listen to? is it philharmonic, symphonies, drum n bass or maybe hip hop?
I do not claim to be an audiophool. In your effort to improve the acoustic coupling between the two speakers by positioning them close to each other, are you introducing a magnetic coupling between the speakers? Does it matter?
This video flowed more smoothly than a lot of your other videos. I assume you were reading a script, but there was a lot less verbal static.
If they are both doing exactly the same thing, how could that be a problem?
@@IBuildIt it seems that the rear voice coil is in the magnetic field of both speakers. I don't know how the fields from the 2 magnets add together. I don't know if it matters enough in the real world.
@@bobt2522 like trapping a voice coil between two opposing magnet fields ?
So after all that talking, you didn't tell us what it sounded like?