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Topic: Romy's Isobarik Loudspeaker

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Posted by Romy the Cat on 05-30-2007

Fllowing my experiments with Injection Channel

http://www.GoodSoundClub.com/TreeItem.aspx?PostID=4473

I have discovered recently that I was a greedy fool who should know better.

The new Injection Channel does OK as a independent single channel but it produces too much baas in contest of the entire Macondo Acoustic System. So, my desire to go for larger box and lower resonance frequency was a move to wrong direction, at list in context of the Macondo’s needs. So, why I started a new thread? I did so because is it not a conversation about the Injection Channel – it will be use another smaller box but about the thoughts that I develops after I learned that new Injection Channel box was too big.

My first reaction was to reduce the volume of the Injection Channel box. I thought to fill the box with non-condensable and non-compressible material but then I decided to make a new box. However, while I was thinking about the material chooses that would fill up the excessive boxes, the material that wopuld not virtuously increase the volume of the box, - a very interesting idea occurs to me.

I asked myself why don’t I fill the portion of my oversized volume with some kind of inflated balloons made from rubber, latex, chloroprene or nylon? I mean the inflatable volume should disperse the volume that is available for the driver. However, the inflated latex is not firm and the volume inside the balloon will be still semi-compressible by the driver and compression of the air behind the driver.  Well the boundary of the balloon will most likely act as dumper. The balloon thickens might me changed – and consequently the compliance of the ballooned walls might be changed. The air in the balloon is at higher pressure then air behind the driver – and therefore the driver will compress that air (and the walls of the balloon) at different rate then the “free” air inside of the acoustically suspended driver in a box. Then, we could go for inflating the balloon not with air but with helium or hydrogen or whatever else… The point is that the propagation of the pressure in the different materials would be different and who know how it would affect sound….

OK, let take the concept a one step further: the active dumping. Pretend that we have a balloon inside of a speaker, or some kind of elastic inflatable wall, let call is – the “balloon”. The balloon is inflated but the final pressure inside the balloon is controlled by an ultra-high-throw low-passed driver. The purpose that driver is not “to sound” but to act as a pressure pump for the balloon. By, manipulation the phase discrepancies between the radiating driver and the “pumping driver” theoretically it would be possible to accomplish the effect of infinite baffle inside of enclosure of any size. Moreover, using the active dumping it would be possible to inflict any imaginable custom dumping, affectively inflicting custom resonances to the radiating driver…

Very interesting….

I personally have no practical inters in the idea but I think the idea is very powerful and it might be fun to play with the concept.

Rgs, Romy the Cat

Posted by Paul S on 05-30-2007
Are you serious?

You do see this sort of thing used in expensive automobile suspensions, including the new Ferrari 599...

Is one idea here to get away from any sort of vent at any cost?

Would such a bladder also require temp sensors and vario cooling?

Does this mean the surface/cabinet resonances of your present large-ish box are pitched too low, or are you just thinking to lose or CONTROL some of the internal/volume-related resonance?

EQ still sounds like an easier way out to me, so maybe I am misunderstanding the application.

Best regards,
Paul S

Posted by George on 05-30-2007
Excellent Reviews Too!

http://www.amazon.co.uk/thesharperedge-830156000025-Budweiser-Inflatable-Speakers/dp/B00006IUFI

Posted by Markus on 05-30-2007
The balloon must be flexible to work as you intend. That means that the radiating driver will effectively "see" the volume in the balloon, too. So why the balloon? Also, won't the sound of the internal driver reach the outside world through the membrane of the radiating driver?

It all looks very close to an isobarik design, even though I appreciate you would want to use the internal driver differently from a conventional isobarik design.

Posted by Romy the Cat on 05-30-2007
 Markus wrote:
It all looks very close to an isobarik design, even though I appreciate you would want to use the internal driver differently from a conventional isobarik design.
Yes, it did remind me in a way the isobaric configuration, though the  isobaric concept was made to increase amount of bass. What I propose should do opposite - decrease the amount of the bass by spreading out the primary resonance… I am not saying that it should be good but it should be auditable in a certain way….

Posted by RF at Ona on 05-30-2007

Congratulations, Romy, I think you just re-invented the ISOBARIK loudspeaker.

Although, Linn's Isobarik implementation of two drivers moving in parallel separated in a small chamber which would be nearly in constant volume (and pressure) couldn't really work as the trademarked name implied it was an interesting point of departure.

At one time, I thought to take the idea of using an internal self-contained loudspeaker to keep a constant volume/pressure chamber as way of  "killing two birds with one stone."

It would allow the primary driver to work nearly at free-air resonance but in a smaller enclosure. The price of inefficiency would be paid by the internal driver and efficient amp. A servomechanism would maintain the constant internal pressure. A servo would work well here as it would be homeostatic and not a motional feedback system where the linearity and phase of the servo would be critical. It would also not be in the signal path of the primary driver.

The second advantage would be to isolate the external cabinet from the high pressures which cause the panels to radiate. I also suspect that high internal cabinet pressures (i.e. both high and low pressure extremes) cause speaker cone bending different from that caused by the driving voicecoil and suspension. Avoiding this cone-bending/shape-distortion gives, I suspect, an advantage to high volume or infinite baffle woofers - an ease to their sound.

In somewhat picturesque terms, think of your highly regarded Aura 1808 driver in a modest non-vibrating enclosure operating at free-air resonance. An internal speaker such as small ContraBass Servomotor Driven Subwoofer (which uses a radial motor instead of a linear motor and is capable of formidable excursion) would be used to maintain the constant internal pressure.

I now live in a home with an attic and basement, either of which I might use for an infinite baffle woofer. This has made my earlier idea unnecessary for me personally.

Regards to all,
Robert

P.S.  Markus's post and Romy's reply came while I was writing this.


Posted by Markus on 05-31-2007
Robert,

your view somewhat mirrors that of Linn when they introduced their Isobarik speakers. In the almost 30 years since then, the theoretical understanding of isobaric loading has improved. What it does is to double the moving mass and the motor force. You can also look at it as a space saving device: if you look at the loading of the front driver, the space between the two drivers counts normally, the space behind the enclosed driver counts double. Isobaric loading can be seen as a (not inexpensive) way of getting deeper bass out of a given enclosure, or of reducing enclosure size for a given lower frequency limit. There may be further advantages, such as improved enclosure rigidity from the internal partitioning that isobaric loading implies.

Posted by SearcherOfBetterSound on 05-31-2007
All I can think of what it is, in simple terms, is that what you're describing is a nature-like and..actually it can be considered many things, more electrically direct or not, acoustically direct or not..equalizer for tone, pressure, vibrational manipulation... This is a way for calming and adding bloom to perhaps a too analytical and electrically misguided sound. Coming from a box/driver/opening/speaker-stand connection thing? Comparing to other equalizers, perhaps it could be thought that this is like a more "living" thing, more subtle and variable, while others, while you may normally think "nastiness", actually may be DEAD...could make sense, a dead box with a free-to-garbage regular speaker thing being fed it.. That is just what I've been getting at right now so correct me if I'm wrong. I would like to think that I TRY to be a complex-to-simple interpreter because I feel that both more-casual consumers AND you tech types (I don't think I'm either) do not try to teach the public in a more general or good enough way...sorry if this offends you guys, yet I think it's a VERY common and worldly "disorder" in my eyes (not trying to TEACH others ALL the necessary aspects to think and connect to, but just getting straight to the nitty-gritty of only few-aspects current idea-thinkings), but it's just what I feel and also explains why people haven't been answering some of my questions or aren't excited enough or whatever...

Posted by rowuk on 07-14-2012
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Would it not be possible to create a type of transmissionline, but with a closed port and many bends to spread the internal resonances and provide means to damp them.
Perhaps it is even good to tune an open transmissionline to a couple of octaves below the pass band and heavily damp it so that there is no LF reinforcement or port noise but the driver does not see a single cabinet resonance - and at the same time critically damp its own driver resonance.

Of course the biggest danger in the balloon is that it could "store" energy and release it at a later time, smearing everything.

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