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Multi-Way Conventional loudspeakers with crossovers

Isobaric frequency limits?
Isobaric frequency limits?
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Old 23rd September 2017, 01:30 AM   #11
john k... is offline john k...  United States
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Originally Posted by Bill poster View Post
Pretty sure two in parallel will give the same output but requires more power to do so ie 4 instead of 8 ohm load. Thats what I've read, correct me if wrong
Correct, but that is 3dB lower efficiency. 3dB more power in, same SPL out.
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Old 23rd September 2017, 01:54 AM   #12
Bill poster is offline Bill poster  Thailand
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Thanks for clearing that up. I agree that Isobarics don't generally make sense, 2 drivers etc.. just this driver normally requires such a big box it makes an argument for it, plus I can't see the equivalent in performance /isobaric cab

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Old 23rd September 2017, 08:07 AM   #13
scottjoplin is offline scottjoplin  Wales
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If mounted in reverse there is some canceling of non-linearity distortions
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Old 23rd September 2017, 11:30 AM   #14
john k... is offline john k...  United States
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Originally Posted by scottjoplin View Post
If mounted in reverse there is some canceling of non-linearity distortions
That is pretty much a myth. I've analyzed the isobaric system and it depends on many factors. In general if there is reduction in distortion is it slight. However, some distortion components can actually increase slightly. It is a completely different situation that the calculation of even order distortion with a push-pull pair of conventional woofers (separate boxes). In the case of isolated push pull system it is the sum of the output of the two system and that the even order distortion is out of phase and cancels. In the case of an isobaric system it is not the isolated outputs that sum. It is two nonlinear devices directly interacting. The motion of one is a driving force to the other. The bottom line is that a blanket statement that isobaric system reduce distortion can not be made.
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Old 23rd September 2017, 11:53 AM   #15
Juhazi is offline Juhazi  Finland
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I have always wondered how the outer driver can handle the extra cone movement from double force... Having double radiating cone area would be more beneficial, but of cource the box gets bigger too.
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Old 23rd September 2017, 01:46 PM   #16
john k... is offline john k...  United States
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I have always wondered how the outer driver can handle the extra cone movement from double force... Having double radiating cone area would be more beneficial, but of cource the box gets bigger too.
The pressure in the isobaric chamber actually varies as the pressure in the normal sized, single driver box. Thinks about it. The only way the outer driver will behave as if it is in a normal box is if the force on the back side is the same as it would be in a normal box. The rear driver sees a pressure force on the back side which is twice what it would be in a normal sized box, bot on the front side it sees the pressure in the isobaric volume, which is, again, the same as in a normal box. This both the front and rear drivers have the same net pressure force acting on them; that which they would have in a normal sized box. (Minor differences do occur.)
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Old 26th September 2017, 03:26 PM   #17
Bill poster is offline Bill poster  Thailand
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Originally Posted by john k... View Post
The pressure in the isobaric chamber actually varies as the pressure in the normal sized, single driver box. Thinks about it. The only way the outer driver will behave as if it is in a normal box is if the force on the back side is the same as it would be in a normal box. The rear driver sees a pressure force on the back side which is twice what it would be in a normal sized box, bot on the front side it sees the pressure in the isobaric volume, which is, again, the same as in a normal box. This both the front and rear drivers have the same net pressure force acting on them; that which they would have in a normal sized box. (Minor differences do occur.)
Suppose a small upside is that a lower Q is easily attained with a slight increase in box volume and will lessen pressure on the back of that cone.

Why tf am I so obsessed with isobarics..
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Old 26th September 2017, 06:29 PM   #18
scottjoplin is offline scottjoplin  Wales
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Old 26th September 2017, 08:08 PM   #19
Nico Ras is offline Nico Ras  South Africa
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Suppose a small upside is that a lower Q is easily attained with a slight increase in box volume and will lessen pressure on the back of that cone.

Why tf am I so obsessed with isobarics..
Simply because the sound moves you like no other you can taste it. I went one step further and loaded the rear speaker into a transmission line. I drive it with a massive 7 watt class A JLH amp in a listening room of 300 cu m.
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Old 26th September 2017, 08:57 PM   #20
JeffYoung is offline JeffYoung  Ireland
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Isobaric frequency limits?
I had both Saras and Linn's big Isobariks. I loved the Saras, but they tended to eat amps. The big Isobariks were a bit easier to drive. Never liked the midrange on them, though, and finally moved to Magnepans. But God, what delicious bass those Isobariks had.

And hey, this is DIY. You should build whatever takes your fancy.

Cheers,
Jeff.
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