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not saying i'm doing this but isobaric with 1.5" drivers

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  • not saying i'm doing this but isobaric with 1.5" drivers

    not saying i'm doing this but isobaric with 1.5" drivers, would there be any benefit to doing this in this day and age? assuming at 0.01cuft enclosure would be roughly the same in an isobar setup. I was just thinking when modelling and i had the option.

    When i say enclosure being the same, i mean the time you have the first coupling of the driver and the sealed enclosure behind it.

  • #2
    Isobaric can be useful when dealing with drivers that have very high Vas, to reduce the enclosure size. If said driver is, for instance, an Altec 421 with Vas of 1140 liters the size reduction would be substantial. When you have a small Vas to begin with there's no point to it.
    www.billfitzmaurice.com
    www.billfitzmaurice.info/forum

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    • #3
      You also double the power handling
      craigk

      " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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      • #4
        I can see that cramming isobarically loaded drivers into something like a BT speaker may have benefit if DSP is not used like the commercial offerings. Mainly for bass extension, and power handling. However, a 1.5" driver has a high Fs that will not change even when loaded this way, so the extension result is likely minimal.

        Later,
        Wolf
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        • #5
          I was just waiting on a part for the beer can and was thinking of what could actually be done, I have some OP amps and was even thinking if a boost circuit would be worth while, the box is too small for two traditional drivers unfortunately

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          • #6
            It's more correct to say an isobaric configuration requires twice the power in order to produce the same SPL as only a single driver because only the output of the room-exposed driver is doing the radiating. "Double the power handling" was often used as a marketing tool for commercial isobaric woofers. Again, as Bill said in Post #2, the only benefit from an isobaric configuration is in reducing the required cabinet volume.
            Paul

            Originally posted by craigk View Post
            You also double the power handling

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            • #7
              Originally posted by 3rutu5 View Post
              I was just waiting on a part for the beer can and was thinking of what could actually be done, I have some OP amps and was even thinking if a boost circuit would be worth while, the box is too small for two traditional drivers unfortunately
              I think your BF37 can squeeze into a space as small as 1/6-1/8'th liter and still reach 105-125hz F3, and I think you'll have about that much space in the can (I'm guessing pretty hard on the wall thickness and other things filling the inside...in my defense it looks distractingly cool). I think your chosen driver looks to be a good fit for the project as-is.

              EDIT: Are you trying to find a way to fit a pair of speakers in there for stereo (ISO or DSP or other methods to avoid choking the bass too much with a stereo pair in the same small can)?
              Or is this still strictly a mono creation and you're worried the cabinate size isn't enough for the single driver?
              My first 2way build

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              • #8
                Originally posted by Paul K. View Post
                It's more correct to say an isobaric configuration requires twice the power in order to produce the same SPL as only a single driver because only the output of the room-exposed driver is doing the radiating. "Double the power handling" was often used as a marketing tool for commercial isobaric woofers. Again, as Bill said in Post #2, the only benefit from an isobaric configuration is in reducing the required cabinet volume.
                Paul

                it is more correct to say you or bill neither understand isobaric loading. here is a nice simple video that explains it very well. notice the next last chart, the one on bass response.

                https://www.youtube.com/watch?v=BdF7nTU_QOQ
                craigk

                " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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                • #9
                  Originally posted by LOUT View Post
                  I think your BF37 can squeeze into a space as small as 1/6-1/8'th liter and still reach 105-125hz F3, and I think you'll have about that much space in the can (I'm guessing pretty hard on the wall thickness and other things filling the inside...in my defense it looks distractingly cool). I think your chosen driver looks to be a good fit for the project as-is.

                  EDIT: Are you trying to find a way to fit a pair of speakers in there for stereo (ISO or DSP or other methods to avoid choking the bass too much with a stereo pair in the same small can)?
                  Or is this still strictly a mono creation and you're worried the cabinate size isn't enough for the single driver?
                  I actually was thinking I have 0.01cuft which I had tuned to 90hz I think last build and was just thinking whilst I wait....stereo or mono I don't really care, just as much bang for my buck using what I have on hand. I'm happy with the size for the speaker as with the other build I got some bass which was impressive, not punch you in the chest bass but something I could hear.

                  I generally do these builds and at the 90% mark I'll see something I completely forgot about or didn't know of that would take the project to the next level

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                  • #10
                    Originally posted by craigk View Post

                    it is more correct to say you or bill neither understand isobaric loading. here is a nice simple video that explains it very well. notice the next last chart, the one on bass response.

                    https://www.youtube.com/watch?v=BdF7nTU_QOQ
                    Ive watched his videos before and I find (even though I don't always understand the jargon) informative.

                    I remember thinking about an isobar with some 3.5inch drivers and basically got told it is good for old drivers that weren't efficient, but today's modern technology it wasn't generally required.. probably like yourself I was CAD'ing up my project and watching YouTube at the same time and some isobar vids popped up and it made me think would this be beneficial here, or basically using the same.space and output as a traditional build
                    ​​​​​.

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                    • #11
                      Originally posted by 3rutu5 View Post
                      Ive watched his videos before...even though I don't always understand the jargon
                      ​​​​​.
                      You're not alone in that respect. For instance, compare this chart to his isobaric sealed chart:
                      https://billfitzmaurice.info/images/...comparison.jpg



                      The blue line looks like his single driver response, the red looks like his dual driver isobaric response in the same net volume. The reason for the difference is the system Q. One way to alter Q is via isobaric loading. But it's not the only way. What this particular chart shows is the RSS 315 HF Twelve in a net .5 cu ft box, which gives a Q of .99 giving the blue line, and the same driver in a net 1 cu ft box for a Q of .78, giving the red line. If you use two drivers in a sealed isobaric you can realize that same .78 Q, and the same transfer function, from a net .5 cu ft box. However, as Paul noted, when you look at the SPL chart the isobaric sensitivity is lower, so while the dual drivers will take more power they also need more power to get the same output. So why isobaric? Fifty years ago it could make the difference between needing a net ten cubic foot cab and a net five cubic foot cab for the same result. But today the idea of buying two RSS 315 HF and needing twice the power to realize a 0.5 cu ft reduction in the net box size isn't all that appealing.
                      Last edited by billfitzmaurice; 04-18-2020, 01:38 PM.
                      www.billfitzmaurice.com
                      www.billfitzmaurice.info/forum

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                      • #12
                        Sorry, you're just plain wrong. I do understand isobaric loading and used it for a personal build or two "way back when". There is only one driver exposed to the room and it can only generate so much SPL for a given input voltage. When you give it a specific voltage, the other driver is also receiving an identical voltage that consumes the same amount of power but does not radiate any SPL out of the box. Therefore, the pair of drivers requires twice as much power to generate the same SPL as a single driver.
                        Paul

                        Originally posted by craigk View Post

                        it is more correct to say you or bill neither understand isobaric loading. here is a nice simple video that explains it very well. notice the next last chart, the one on bass response.

                        https://www.youtube.com/watch?v=BdF7nTU_QOQ

                        Comment


                        • #13
                          you clearly gain bass output. the parallel wired drivers are producing a noted amount more bass energy. one other point, just because you design something does not always mean you got the best results, or that your design is correct. so i guess the best way to prove the effects of isobaric loading is to bring a speaker to MWAF. so i will be there with one this year. everyone can listen and see what they think with their own ears.
                          craigk

                          " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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                          • #14
                            I'm sorry but that's definitely incorrect as far as how efficient the system is which is my only point; the pair of drivers requires twice as much power as a single driver to generate a given SPL because only the outer driver is generating SPL and that is limited by its Sd, Xmax and thermal abilities. The inner driver neither helps nor hampers the outer driver, moving with the outer driver, but its output doesn't escape the box. An isobaric pair of drivers will be able to generate the same bass response (SPL-wise and frequency-wise) as a single driver but within a box volume half as large and that is the only advantage.
                            Paul

                            Originally posted by craigk View Post
                            you clearly gain bass output. the parallel wired drivers are producing a noted amount more bass energy. one other point, just because you design something does not always mean you got the best results, or that your design is correct. so i guess the best way to prove the effects of isobaric loading is to bring a speaker to MWAF. so i will be there with one this year. everyone can listen and see what they think with their own ears.
                            Last edited by Paul K.; 04-17-2020, 06:52 PM.

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                            • #15
                              Originally posted by Paul K. View Post
                              I'm sorry but that's definitely incorrect as far as how efficient the system is which is my only point; the pair of drivers requires twice as much power as a single driver to generate a given SPL because only the outer driver is generating SPL and that is limited by its Sd, Xmax and thermal abilities. The inner driver neither hinders nor hampers the outer driver, moving with the outer driver, but its output doesn't escape the box. An isobaric pair of drivers will be able to generate the same bass response (SPL-wise and frequency-wise) as a single driver but within a box volume half as large and that is the only advantage.
                              Paul


                              i do not know why you are stuck on how efficient they are. i never mentioned that. i said they can handle twice the power which is still correct. when you wire 2 drivers in parallel you are doubling the power that one driver can take. it doesn't matter if it is in or outside the box.
                              if nothing is going on with the inner driver why is the bass response on the graph +3 db on the roll off, and much more linear ?

                              craigk

                              " Voicing is often the term used for band aids to cover for initial design/planning errors " - Pallas

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