Or, use the full volume and put in two sets of woofers. I've done that before too in a vehicle that did not have room for two full size boxes. But, that was over 35 years ago before DSP was commonplace. With DSP and servo controlled subs, I just don't see the need for using isobaric designs anymore. Once upon a time, though, they did serve a purpose.
That does not reduce the air volume needed for each woofer to reach a particular frequency. Without the appropriate air volume, you still need servo control and/or DSP if you want maximum low end extension.
They both push out and the same time, and pull in at the same time.
The other option is to make a single driver either on the top, or the bottom. If on the bottom you have to put the whole speaker on legs to give the driver room to move without restriction.
And yes - you certainly need to have some form of frequency shaping if the driver excursion does not become a factor. There is a lot of information on this and calculation spreadsheets on Siegfried Linkwitz's site. See for example the 7 pages from here https://www.linkwitzlab.com/frontiers.htm
My experience as well. I had 8” isobariks in my hatchback years ago. Small enough to tuck out of the way yet powerful enough to blurr the rearview mirror. The smaller box is also stiffer and less resonant at low frequencies than the larger box.
Just to clarify, the above statement applies when the two drivers are connected in parallel. If connected in series the isobaric system frequency response will be -6 dB for the same input voltage.
Correct. As noted in the passage I quoted (in the link I posted), the parameters they listed were for a parallel connection.
I saw that, but they don't say what happens for a series connection, which I felt was also worth knowing 🙂.
Correct. This is neither an isobaric construction nor a dipole. It is two closed boxes facing each other with in-phase radiation, similar to a push-push construction.
If they were connected with reversed polarity, there would be no sound emission, the sound emitted by the two closed boxes would cancel each other out.
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They are ripole upon further inspection
With some heavier "mass loading" than traditionally seen on the back "OB" exit. Or maybe not.
Jeremy
With some heavier "mass loading" than traditionally seen on the back "OB" exit. Or maybe not.
Jeremy
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Ok, seems that you're right and I was wrong. 😢
This picture seems to make it more clear:
The isobaric design is useful to a manufacturer that wants to build a new, "innovative", sealed, passive crossover speaker to sell into the classic high end dealer model, where equalization is verboten, but they already have a thousand woofers in the warehouse that are close but quite right for a single driver sealed design. Once you have the woofers and can build whatever box, bigger and heavy seemingly more impressive, this is a good solution. All the above mentioned improvements apply. Woofers front to back cancel some of the distortion. The in box F 3dB is lower for a given volume and sealed bass is great. Of course the max SPL is the same as one woofer and the efficiency is lower.
Does seem backward if you must mix tech.
We were all wrong. I just happened upon that pic low in the second web page of a link off the main page. The advertising glamour shot pics didn't show a clear back view. 😳
Jeremy
Ripole comes from "RiPol", the shortened version of Axel Ridthaler's patented "Ridtahler dipole",
The "figure of 8" pattern depicted in the Treble Clef Audio Model M photos makes the dipole radiation and conceptual origin obvious (to those familiar with the RiPol..), though it doesn't appear they acknowledge Axel's work.
The larger volume between the speakers and rear chambers in the original RiPol create a nasty 10-20dB resonance peak in the 180-300Hz range (volume and depth dependent) requiring a fairly low and steep crossover frequency which relegates them to subwoofer use below ~125Hz.
The Treble Clef Audio woofer's small volume, constrained layer synthetic rubber damping and cement based syntactic foam damping material in the hemispherical rear chambers claim to raise the resonant peak frequency "to at least above 370 Hz".
https://patentimages.storage.googleapis.com/61/d2/2b/fc5c2ba683cf36/US11363369.pdf
Hmm, 370 Hz is nearly an octave below the invention claim of 16-700Hz:
Oh well..Lets go to the real world:
Anyway, it looks cute, and the Treble Clef Audio Equalization Manual and White Paper are actually quite well written and informative.
They can be found under "Documentation":
https://trebleclefaudio.com/product
Art
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