Changing box parameters my adding another driver?

[Boscoe]

I don't mean just add another driver into the box and there you go, although still I propose something that has probably already been done.

In my idea there are two drivers; there is a radiating driver and then another driver to control the air in the box. Basically the control driver radiates somewhere where it's not heard, ideally out a hole in a wall! It goes on the back of the box and is wired out of phase so it absorbs the movement of air the radiating driver has created in the box so lowering the resistive force of the air in the box making it appear to the radiating driver to be a lot larger and so lowering resonance. The amount of power delivered to the control driver can be varied to tune the box.

How about that? Except from the waste amplifier power and added cost good idea?

[planet10]

The simplest form of this is the isobarik, where the control signal is the same as the radiating drivers.

I have notes from the late 80s describing a system where the rear driver is controlled by DSP. Very impractical at the time.

dave

[Boscoe]

Yeh I know about iso barik but this method instead of just having box size you could go further with this by giving even more power to the control than radiating driver which could make box size less than half.

[sreten]

Hi,

As you describe it it is fairly pointless. Your talking infinite baffle speakers
with the rear radiation going into another room, cellar, roofspace or outside.

There is no point to the extra driver, simply allow the drivers rear radiation
to go that way, the extra driver will do nothing you can't do with a driver.

You simply don't need a box with the idea, so a box is a poor idea.

The two drivers and box will simply act like one compound driver.

You can't half the size of a box you don't need in the first place.

Very obscurely you could use the arrangement to make a box seem
to appear bigger, by cancelling some of the rear radiation, but there
is no point ICS to not letting all rear radiation go to the elsewhere.

Its possible regarding the above the driver is too low Q not to need a box,
in this case you could use a resistive vent into another airspace to
make the box far smaller but still raise the Q of the bass alignment.

rgds, sreten.

It is infinite baffle isobaric, utterly no point to isobaric without a rear box.

[Ron E]

Originally Posted by Boscoe

Yeh I know about iso barik but this method instead of just having box size you could go further with this by giving even more power to the control than radiating driver which could make box size less than half.

Just use the power you are using in the "control driver" to EQ the main driver in the first place. Look at the Marchand "Bassis" and try to understand the 'linkwitz transform' concept.