Building the best loudspeakers

[planet10]

Originally Posted by Salas

You lower Fs by sqrtHz

Perhaps a bit misleading without the conditions.

A tightly coupled isobarik woofer has 1/2 Vas, same Fs, same Qt, 2x mass and BL vrs a single one of the woofers.

So (ignoring the volume of the isobarik chamber) if you put a compund driver in a box volume V, it has the same response as a single driver in a box of 2*V volume. So isobarik simply lets you use a box half as big (+ chamber) as you would need for a single woofer.

4 drivers (2 isobarik pairs) can be put in the volume you would use for 1.

Putting

[Salas]

You are right. I had in memory something about targeting the same volume and using it for going lower scenario or I dug it up from simple mass loading. Ignore my earlier post. Bad memory. Compound just allows half a box is a straight rule.

[chops]

Originally Posted by Salas

The loss is you go 4 Ohm without any 2.83VSPL referenced increase.

But you also reduce the work load on the drivers by half, as well as lessen harmonic distortion, especially if one of the drivers is physically inverted from the other.

[Salas]

Of course. Those are quality gains to consider as positives. Still there is a 3dbW loss in sensitivity that demands horsepower. The good thing is there are affordable high SPL pro woofers around that were not the norm in the 80s when some companies like Linn used the principle, plus class D. So this Isobarik thing becomes very viable again IMHO.

[chops]

Originally Posted by Salas

Of course. Those are quality gains to consider as positives. Still there is a 3dbW loss in sensitivity that demands horsepower. The good thing is there are affordable high SPL pro woofers around that were not the norm in the 80s when some companies like Linn used the principle, plus class D. So this Isobarik thing becomes very viable again IMHO.

Exactly, hence why I'm seriously considering incorporating an isobaric design in my next project.

[Salas]

Will save much space, braces the cabinet, push pull back magnet linked anti resonance trick, not a bad dish. Its they had 87dB B139s in the 80s and they got 'em down to 4 Ohm on top of it, plus the amps were not up to the task.

[454Casull]

Originally Posted by chops

But you also reduce the work load on the drivers by half, as well as lessen harmonic distortion, especially if one of the drivers is physically inverted from the other.

Has anybody done distortion testing for an isobaric pair of woofers vs a single woofer (in double the size)?

I'm curious to see how the distortion actually changes.

[Brett]

Not mwasurements, but worth reading.
Isobaric