It's been a long time since I last posted much on these shores. Life has just drifted away from this forum.
Anyways, one day someone phoned me up being referred to me for building custom speakers and that he had some very specific requirements. After delving somewhat deeper it turns out what was perhaps most sensible was a sub woofer that would suitably underpin four Dunntech Sovereigns that were being quad-amped with TACT amplification.
After a thorough analysis of the room following a site visit, I thought to go out on a limb and propose a horn sub woofer to make up a stage in said installation. A proposal that I didn't seriously consider that it would be accepted as it is as loony as it was ambitious. The design was for a sub 20Hz corner frequency and its design tuned to cancel a notch in the frequency response at the listening position. It was to far outmatch four B&W DB1s. Cue a couple of weeks of on-off modeling, some phone calls to speaker importers, timber merchants and lots of German cursing at a screen.
To my surprise, I was to proceed. What followed was the most challenging build I have undertaken to date, easily eclipsing this build. It took a team of six men to move each of the two 300kg modules into position, in hindsight eight would have been more appropriate. The install counts over 1500 screws and fasteners.
Here a work in progress pic before the top was installed. If one didn't know, one'd assume it was a stage and that perhaps Dunntech had loaded some plutonium in their Dynaudio woofers.
Yesterday I got to validate the performance of said horn in the room corner tucked away behind the screen. Please note that the room resonances and reflections super-impose themselves on this measurement as the horn's exit area of 3m^2 make a "near field" measurement impossible without such room interference. The mid-band sensitivity of each of these 21" beasts is around the 108-109dB mark, the rest of the measurement speaks for itself. A single Watt per cabinet would outplay the four DB1s and then you can add 27dB headroom for which the 18Sound driver is rated continuous.
Moving to the listening position, one can see two axial modes at 18 and 23Hz causing havoc (it's a bit excessive but then this whole project is). The horn was designed to couple to the room and it is evident by the response line only crossing below the zero line around 13Hz (the mic is a 1/2" metal capsule). The deep suckout between 30-40Hz is much reduced leaving the remaining concern at a 57Hz resonance set up between room floor and ceiling and an oblique mode which may benefit from some 60Hz EQ.
On firing it up with no EQ it was immediately evident that too much of a good thing is wonderful. Tight, punchy and dynamically unlimited. Visceral and easy in a way only horns can really do it.
Anyways, one day someone phoned me up being referred to me for building custom speakers and that he had some very specific requirements. After delving somewhat deeper it turns out what was perhaps most sensible was a sub woofer that would suitably underpin four Dunntech Sovereigns that were being quad-amped with TACT amplification.
After a thorough analysis of the room following a site visit, I thought to go out on a limb and propose a horn sub woofer to make up a stage in said installation. A proposal that I didn't seriously consider that it would be accepted as it is as loony as it was ambitious. The design was for a sub 20Hz corner frequency and its design tuned to cancel a notch in the frequency response at the listening position. It was to far outmatch four B&W DB1s. Cue a couple of weeks of on-off modeling, some phone calls to speaker importers, timber merchants and lots of German cursing at a screen.
To my surprise, I was to proceed. What followed was the most challenging build I have undertaken to date, easily eclipsing this build. It took a team of six men to move each of the two 300kg modules into position, in hindsight eight would have been more appropriate. The install counts over 1500 screws and fasteners.
Here a work in progress pic before the top was installed. If one didn't know, one'd assume it was a stage and that perhaps Dunntech had loaded some plutonium in their Dynaudio woofers.
Yesterday I got to validate the performance of said horn in the room corner tucked away behind the screen. Please note that the room resonances and reflections super-impose themselves on this measurement as the horn's exit area of 3m^2 make a "near field" measurement impossible without such room interference. The mid-band sensitivity of each of these 21" beasts is around the 108-109dB mark, the rest of the measurement speaks for itself. A single Watt per cabinet would outplay the four DB1s and then you can add 27dB headroom for which the 18Sound driver is rated continuous.
Moving to the listening position, one can see two axial modes at 18 and 23Hz causing havoc (it's a bit excessive but then this whole project is). The horn was designed to couple to the room and it is evident by the response line only crossing below the zero line around 13Hz (the mic is a 1/2" metal capsule). The deep suckout between 30-40Hz is much reduced leaving the remaining concern at a 57Hz resonance set up between room floor and ceiling and an oblique mode which may benefit from some 60Hz EQ.
On firing it up with no EQ it was immediately evident that too much of a good thing is wonderful. Tight, punchy and dynamically unlimited. Visceral and easy in a way only horns can really do it.
