Isobaric midbass

[Kashtan]

Hi to everyone.
I wonder if there is any positive experience in using this type of load in relation to midbass.
Range is a 80-315Hz around.
Cone to cone a designe.
I`m read about DLS demo car 2007, BMW, winner of SQ challenge, his have a isobaric midbass, also exist Ivy Signature SE - midbass isobaric, 3 pieces on one, twelfe on channel.

 

[weltersys]

The "positive experience" is the Vas (volume of air spring = to speaker compliance) of the isobaric pair is halved, so a speaker enclosure can be half the volume it would normally be for the driver chosen.
Cone to cone (clam shell) isobaric arrangements reduce even order harmonic distortion caused by non-linear suspension and magnetic structures.

More linear magnet and suspension structures and purpose designed low Vas drivers are now more readily available and lower in cost than in 2007.
For a small production company like Ivy, isobaric loading reduces the amount of different drivers types required for the various designs they produce.

 

[mayhem13]

Lower HD isn’t a result in both of the ISO alignments provided the air gap is the same?

 

[Kashtan]

The "positive experience" is the Vas (volume of air spring = to speaker compliance) of the isobaric pair is halved, so a speaker enclosure can be half the volume it would normally be for the driver chosen.
Cone to cone (clam shell) isobaric arrangements reduce even order harmonic distortion caused by non-linear suspension and magnetic structures.

More linear magnet and suspension structures and purpose designed low Vas drivers are now more readily available and lower in cost than in 2007.
For a small production company like Ivy, isobaric loading reduces the amount of different drivers types required for the various designs they produce.

Thank you. I forgot to add - in practice.
And exactly the midbass. I know the theory.

 

[grec]

In practice Isobaric bass sounds tighter and "faster", like way more expensive woofers. Close to Servo-feedback effect, but not that superior. In midbass range is less effective, but still there.

 

[profiguy]

If you arrange isobaric drivers as magnet to magnet, this lowers HD overall, but you need to dampen the coupling chamber very well to not get any standing wave or cavity resonances.

Traditional isobaric setups with woofers cone to cone are harder to dampen properly, mainly because its difficult to get any dampening material to stay in place not having cabinet surface to attach the dampening media to.

 

[Andersonix]

In practice Isobaric bass sounds tighter and "faster", like way more expensive woofers.

It's due to the double cones not letting as much box coloration back through.

 

[Kashtan]

In practice Isobaric bass sounds tighter and "faster", like way more expensive woofers. Close to Servo-feedback effect, but not that superior. In midbass range is less effective, but still there.

Thanks. I tried to find this cases, but it didn’t work out much except for those cases in the first post.
I was also interested in servos for midbass, such cases are also rare like isobaric midbass, but there were, for example, Cabasse top models of the 70s and 80s.

 

[grec]

Totem Mani was also isobaric.

 

[ScottG]

ex. Wilson Benesch

http://www.wilson-benesch.com/wp-co..._Loudspeaker_Review_Roy_Gregory_Audiobeat.pdf

Isobaric’s like bi-amping (their own amplifier with more current). You can further improve them by flattening in-box resonance:

ex.
https://www.diyaudio.com/community/...pensation-circuit-design.317079/#post-5300579

 

[A4eaudio]

2023 was "The year of the isobaric 8-inch two way", although I just made that up.

Each year there is a DIY speaker event called InDIYana in Indiana, USA. Each year there is a casual "theme competition" and last year's was a two way with 8" or larger woofer and restrictions on the tweeter that ruled out most waveguides.

My speaker (Bosi 225) won, using Isobaric Dayton Audio RS225-8's crossed around 1.4khz to a Satori Tweeter.

JHollander had a speaker he named "Not Qualified" because it could not compete due to the Wavecor Tweeter being too large. Used Isobaric RS225P. This speaker won 3rd place in Parts Express' Speaker Design Competition in the over $300 category.

User 4thtry had an Isobaric two way called the Zonkers using the Dayton Audio SD215A-88 subwoofers (isobaric) and Dayton RST28F tweeter. He placed 3rd at Parts Express Speaker Design Competition in the Dayton Audio Category.

 

[superlian]

I appreciate comment on this design. The MTM midrange and tweeter section will be cardioide down to ca 300 Hz. (Its the new TPCD drivers from Seas).

The goal is to make a small, slim 3 way fullrange speaker.

I intend to use this Seas midbass woofers in separate isobaric chambers:

https://www.madisoundspeakerstore.c...e-l16rnx3-6-aluminum-cone-woofer-h1869-8-ohm/

Madisound suggest 0,65 cf pr driver (f3 32 Hz) in standard vented enclosure.

In a isobaric enclosure the vented chamber will be 1/2 = 0,325 cf pr chamber (with the same port dimension?)

The closed chamber should be as small as possible.

 

[picowallspeaker]

Hi, for me ( Ime/IMO) the voices should be the less possible, so for a three way- 3 drivers. Dunno about the cardiod glamour but, as before, voices should be less, so no returning of the back wave.
For isobaric I'd say- try ...But historically it's a technique developed with old drivers, and those that you pointed are more than enough for a single speaker, I mean, those woofers ( And I hadn't seen ' midrange' speaker but 'woofer') noone ever dreamt of having them in the past

 

[john k...]

Many years back I analyzed the isobaric system. http://musicanddesign.speakerdesign.net/Isobaric.html

 

[superlian]

THX

My main interest for isobaric is to reduce the size of the speaker and i understand that it is a expensive tradeoff.

Is your conclusion that the benefits of reduction of distortion and standing wave reflections through the membrane is minor?