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.

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.

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.