When and why did the typical floorstanding speaker lose the midrange driver?

[Pharos]

That raises the question of the Q of that resonance - breadth of the curve.

[drrdf]

Barry: More than one KEF bass driver was used in each unit, and as I explained that was only the peak level, to cover a wide dynamic range, and 40 W was an average level with the full 80 W available on the highest peaks. Who suggested that any of this was of modest size? I have made the point that all of this sort of approach is very volume consuming. You are also it seems ignoring the example which I cited where Briggs accomplished a significant radiation at 18 Hz with only 2 W of power output to a 15 inch acoustic driver. I do not have the house where I installed these infinite baffles any longer; the room where they were installed was around 119 cu m. As I explained I currently have to make do with smaller but nevertheless good units. Clearly they do not produce that performance. The parameters which you seem to concentrate upon to attempt shoot down this approach and its superb infra-bass performance are again in my opinion insignificant to the overall capability. Again I would point out that the proof of the pudding is in the eating. As you indicated previously you have evidently never tried it nor would want to, so you seem to want to denigrate the whole idea. Fair enough if that is what you want to do.

However for all practical purposes I would suggest that a large well-designed bass reflex unit is capable of an adequate performance in the lower bass region, particularly due to the increased Q factor, but does suffer from the anti-phase effect.

[drrdf]

Pharos: I agree entirely with all of your points.

[Barry]

Barry: More than one KEF bass driver was used in each unit, and as I explained that was only the peak level, to cover a wide dynamic range, and 40 W was an average level with the full 80 W available on the highest peaks. Who suggested that any of this was of modest size? I have made the point that all of this sort of approach is very volume consuming. You are also it seems ignoring the example which I cited where Briggs accomplished a significant radiation at 18 Hz with only 2 W of power output to a 15 inch acoustic driver. I do not have the house where I installed these infinite baffles any longer; the room where they were installed was around 119 cu m. As I explained I currently have to make do with smaller but nevertheless good units. Clearly they do not produce that performance. The parameters which you seem to concentrate upon to attempt shoot down this approach and its superb infra-bass performance are again in my opinion insignificant to the overall capability. Again I would point out that the proof of the pudding is in the eating. As you indicated previously you have evidently never tried it nor would want to, so you seem to want to denigrate the whole idea. Fair enough if that is what you want to do.

However for all practical purposes I would suggest that a large well-designed bass reflex unit is capable of an adequate performance in the lower bass region, particularly due to the increased Q factor, but does suffer from the anti-phase effect.

I was not denigrating your approach - I was trying to understand it. The calculations I made followed those of Bruel & Kjaer, on the subject of low frequency sound generation in a small volume (small compared to the wavelength).

[drrdf]

I was not denigrating your approach - I was trying to understand it. The calculations I made followed those of Bruel & Kjaer, on the subject of low frequency sound generation in a small volume (small compared to the wavelength).

OK Barry, I understand: I think ultimately it is one of those try it and see issues; and due to the resources necessary (mainly house) it is not an option open to all. By the way, I forgot to mention that an approach I have tried previously with some significant success is to vent Bass Reflex enclosures and labyrinth enclosures, where you have a house with a timber floor (increasingly unusual these days with solid floors of course) via an airtight pipe to the underfloor cavity. This means that there is no visible port on the enclosure, and the pipe goes directly from the bottom of the enclosure through the floor into the underfloor cavity. This I have found produces better infra-bass and eliminates to all intents and purposes any anti-phase radiation.

Ronald