Sennheiser Orpheus HE-90 with matching tube a

I've spent some time researching open baffles over the last 24 hours. I'm now not so sure.

I knew already that a bass driver suspended in air does no bass because the air pressure is equalised between the front and the rear.

Screwed to a baffle board it doesn't do much more bass because of air pressure equalisation... but it's slightly better.

Put it in a speaker cabinet without a back (a U shaped open baffle) it fairs a little better.

So how to get deep bass? You can't! The only way to achieve that is to attenuate everything else to make it appear that way (the Harbeth M20 being one example but a different enclosure).

That's what I gained by reading between Linkwitz's lines regarding the only crossovers that work... active ones - requiring an amp per drive unit.

In my experience you could improve matters slightly by using a 12, 15 or 18 inch driver...

Then I got to thinking that the U shaped cabinet differs from a rear ported reflex only by the size of the hole...

But, a rear ported reflex can actually be made to reinforce low bass, so should be more efficient?

But then being ported it is tuned to a particular frequency.

So no joy there then.

Back to the OB, so it requires a sub to do the bass? But the sub isn't open baffle.

You see Ash I don't think you understand that HD540 techniques aren't the same as an open baffle... open back headphones have two isolated chambers: the inside next to your ear, and the outside sealed off by the cushion. The outside chamber being massive by comparison - not open, but a form of infinite baffle!

Infinite baffle speakers are actually sealed boxes which use absorptive fillings to make them "appear" bigger than they are.

Deja vu... can't help thinking I've been here before, because I have! First time round was circa 1975.

Good luck!

Graham