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Gallery Bjarne R

Antique full-range horns and subwoofer

 

Bjarne's loudspeaker system of today


The old Voigt horns have had fresh paint after this picture was taken - might improve the appearance a bit...

Gallery Update reveals that new colours can make a whole lot of difference...

The "new" loudspeakers really look stunning

Wauw - great job - Bjarne


Bjarne's own words about his system:

My loudspeaker system today consists of two full-range corner horns, with a mono subwoofer. Therefore, I use just a single Ground Sound DCN23 unit.

The full-range corner horns are original Voigt Domestic Horns from the 1930 ´s. The left one is s/n 44 from 1934, originally sold to the BBC, and the right one is s/n 152 from 1937, originally sold to a Mr. Bartholemew. They are surprisingly similar in manufacture, material etc. They are, today, fitted with Lowther EX 4´s.

Although the two horns have a quite capable reproduction as they are, I use the DCN23 to relieve the delicate Lowther diaphragms from the lowest frequencies, below 60 Hz, by crossing over to the subwoofer. Also, I use the DCN23 for slight equalisation by dampening the Voigt horns at 2-300 Hz, 1-2 KHz, 4-8Khz. For this, I used a Clio software and microphone. Furthermore, I use the DCN23 to take out one room resonance at 31 Hz. For this, I used a Room Analyser from XTZ.

My stereo system is simple consist only of a XTZ D3 class A pre/main amp, a XTZ CD100 and a Hypex UcD400 Class D amp, and of course the DCN23. The Class A amp drive the full-range horns via a 10 ohm resistor, as advised by mr. Nelson Pass. I entirely agree to his recommendations regarding amplifiers driving horns with efficient loudspeakers - White Paper.
The improvement at lower frequencies can be heard as well as measured. The Class D amp drives the subwoofer, which is a band-pass reflex system, with two KEF B139 in a push-pull (isobarik) configuration in order to limit cabinet size (150 l). -3db point is 23 Hz. From the pics. you can see I use a large diameter duct. The penalty for this is a long duct. I found out that that duct resonated vividly at 280 Hz. To dampen this, I first tried a “Pan-flute” termination of the duct inside. It worked, but did not suffice. Then, I tried a Helmholtz resonator, 2,5 liters, tuned to 280 Hz. It worked excellently ! The peak at 280 Hz is all gone, and the bandwidth of the sub extends beyond 500 Hz. Great fun ! So now you’re inspired ?

As you can see, I selected a Hi-Fi 2000 enclosure type Galaxy, no. 1GX288.

I decided to use a LEMO connector for the USB interface, due to the quality, discrete nice look and easy mount of the chassis female part. Male and female typeno’s. are FGG.1B.304.CLAD42, and EGG.1B.304.CLL.

The capacitors you can see on the perf-board at the output of DCN23 are a precaution recommended by Ground Sound. In some cases DC may appear (shortly) during adjustment and fiddling with the DCN23 / X-Over Wizard. Although not entirely necessary, I have included them anyway, in order to protect my Lowthers as much as possible. The perf-board also includes 1:4 voltage dividers for the High-Pass channels, due to the high efficiency of the horns, and to keep up the signal amplitude thru the DCN23, for lowest noise.

I am very content with my system as it performs today. The simplicity, low distortion, and absence of hum, hiss and noise, combined with the clarity and “forward reproduction” of the Voigt horns, gives me a full fill ment that has made me come to rest in terms of the itch to try something else…. at least for a while.

 

 

Above a picture mosaic of the DCN23 based Digital Crossover filter

Above you see the subwoofer

Below the subwoofer amplifier put together with a chassis from an ealier planned amplifier with transformer and capacitor bank, the UcD400 amp module and a Ground Sound AmpC module. The AmpC module controls amplifier muting and the soft start timing.

Measurements imported in the XOverWizard software and simulated response can be seen direct without further measurements. The music system on the right.

This gallery shows that - Antique doesn't have to be antique and not functional - put together with the right ingredients - the old horns have become a whole new cocktail ready for a nice evening with pleasant music performance !

 

 

Bjarne's loudspeaker history


Bjarne's own words on his achivements over the years:

I have built many loudspeakers over the years, of course particularly in my younger years. At the age of 18, I had already built loudspeaker systems of all commonly known types at the time (closed box, bass-reflex, transmission lines, horns, etc).

At the age of 20, I had built a complete Klipschorn system, including the famous K-400 midrange, which was a challenge that involved one of the teachers, Mr. Steckhan, at the technical high-school I attended at the time. He helped me “unfold” the sides of the horn so they could be jig-sawed from flat pieces of 2mm plywood. Note active crossovers and amps.

At the age of 24, I completed a horn system of my own design. In trying to step-up from the Klipschorns, I had, entirely independantly, designed reentrant bass-horns in order to maintain the efficient horn folding that the Klipschorns had offered. Reentrant horns, back then and to this day, are normally only used for midrange horns. Interestingly, I made them from cones of cardboard, soaked in polyester resin, in order to reduce weight. This is a loong story…

30 years ago. This is a simple approach to a ¼ wavelenght Voigt-pipe. It is mounted in the room corner. The unit is “firing” down onto a 45° reflector plate at approx. ear level (not shown), to distribute the high frequencies. The bass emits from the ceiling, through a gap of approx. 10 cm. Not the rugged mount of the unit, using the transport bracket shipped with Lowther units with the larger alnico magnets.

28 years ago. This is the speaker I built for Københavns Hi Fi klub with my friend, Lennart. They were in use for many years. Note “Matrix” cabinet, long before B&W reinvented it.

29 years ago. A nice smaller system I had to build, since we moved to an appartment with no room for large horns. Note trapez bass cabinet (TQWP) to toe-in the mid-high horns. Note active crossovers and amps.



Bjarne is very technical minded and he has always experimented with
technical solutions beyond what the "normal" DIY person would use.

 

 

 

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