INTRODUCTION:
For many years we had a pair of speakers designed and created by the multi-instrumental, progressive rock musician Bo Hanssen from Sweden.
Sure there are great loudspeaker systems made by "backroom boffins" who only deal in the technical details of loudspeaker creation but any musician wants that "sweet" sound and in Bo's case, if you can't find it then you produce it yourself.
Bo had the philosphy of creating high-end loudspeaker systems but at affordable prices! Depends what you call affordable, these were still VERY expensive systems in their day.
Sad about the choice of trade name (SINUS), perhaps it means something different in Swedish!
SINUS was Bo's early venture into "better sounding" loudspeaker systems before morphing into RAUNA of Sweden, then Bo went off on his own (creative artist differences with his partners - happens a lot in the music industry) and was the driving force behind Opus-3 and other systems such as the CaveRex, Okko, Huggin & Munin - watch out for these names, loudspeakers that will astound and surprise!
As luck would have it, Bo was getting set to ramp up production and it all ended very suddenly with his sad passing away in 2011.
If you find this sort of information fascinating (I do!) then take a look HERE for more nitty gritty (no dirt band) on Bo Hansen and his exploits in the world of audio.
So what happened Russ? (I hear you ask, head cocked to one side and one eye closed!)
I was offering our complete A 103D system but not much interest once people found out how much it would cost to have them shipped! Bo made the cabinets extremely sturdy and the result was loudspeakers that felt like they were made of steel!
I waited and waited but the "right person" didn't appear from the mists, I have now decided to use these lovely old A 103D's as a component farm - sad but at least someone else can proudly say "Mate, I have Bo Hanssen inside my speaker system ... listen, you can hear him playing!"
So hear we go with this SPARE PART for the SINUS A 103D (or your own custom loudspeaker design, perhaps even a nice little guitar amp!) .... Read and enjoy
Very briefly, the SINUS A 103D was rated at 100W RMS per channel, presenting a 4 Ohm Impedance load to the amplifier
The configuration is 3 way - Bass, Mid Range and Tweeter.
The sound was "nice", I liked it very much but not just from the sound aspect but here was a loudspeaker designed by an accomplished musician! I like that ...
I currently have a very nice MONITOR AUDIO S2 system and some DALI 5's being used here and both of those are very good loudspeaker systems but this SINUS 103 D is another level ABOVE - a lot of it has to do with the larger 10" woofer but also the audio had greater "clarity" or "detail" - my source music was a range of classical using REAL instruments that can be very demanding of loudspeaker systems e.g acoustic pianos but I also played complex sound such as guitar ensembles and the sound didn't turn into a gooey mess, very nice.
I made "left - right" sound comparisons of the SINUS system to check if I could hear any audio differences between the two speaker channels (because, if you look at my description of the mid-range speakers and further down, one of these woofers, you can read they are NOT PERFECT!) But perhaps I am being just a bit pedantic because I could not discern major differences between the two channels when I made my final tests last week before dismantling the system.
Please read the description below for yet more detail about these woofers and what is "not quite right" with one of them.
SINUS (Bo Hanssen) - A 103D Loudspeaker System SPARE PART ONLY
Part: Woofer (Bass) Loudspeaker
10 Inch diameter
Made in Sweden
Circa 1970's
Part #: U 1051 Z
Each loudspeaker (I have two) has a batch or production number, 919 & 941
Impedance: 4 Ohm
250mm diameter ROUND
ACTUAL diaphragm (the cone) diameter is 220mm due to the metal lip around the outside (for mounting)
75mm diameter dustcover (which tends to indicate the voice-coil has a large diameter)
MATERIALS USED:
Dust cover is a fabric
Cone looks to be a heavy paper/card based - quite dense.
The outer cone support is NOT rubber but instead looks like a thin fabric impregnated with "something" - if held to the light, I can see through this surround.
Basket is all metal with a baked enamel finish (Grey) and is a Octo rear port design (eight large circular cutouts to the rear of the basket)
Inside the speaker I can see a substantial "paper like" spider system
Magnet (material unknown) is approximately 50mm diameter x 40mm height and surrounded by a very substantial U shaped bracket. This bracket also greatly reduces the external magnetic field from the magnet - whereas the magnetic "pull" is very strong near the magnet, outside of the bracket I could barely detect the magnetic field.
Solder tags are installed (but insulated from the basket) as terminals for wiring (no spades used here!)
DIMENSIONS:
Round metal frame is 250mm diameter x 140mm Deep
Rear rectangular U bracket covering the magnet is 75mm x 80mm x 60mm Height
Mounting holes (4) are spaced 170mm apart from each other (straight line measurement) and are 3.5mm OD
Voice-coil DUST COVER diameter is 75mm
Weight: 2.2Kg
COSMETIC CONDITION:
CLEAN ***
SPECIAL NOTE: While they might be clean now, when removed from the cabinet(s) they were not! Why? The reason is that the cabinet was FILLED with small foam rubber or fibre small cubes or pieces packed LOOSELY. This filling was packed into "fibre bags" made of a mesh, so the very small particles of filler could "float around" inside the cabinet! NOT GOOD! I had to spend quite some time very carefully cleaning out all this dust but now they are nice and reasonably clean.
The manufacturing label on the rear of the magnet is NOT discoloured, unlike the mid range oval speakers.
One speaker (919) has some oxidisation (partially) of the surround (rust looking in other words) but make no mistake! This is not due to water or moisture. These woofers were sitting in a "bed" of material which felt like a plasticine but had gone quite hard. When lifting this material off, some of the baked enamel finish also came off! The rust look is where the plasticine type material was in contact with the surround.
This only occurred with one speaker, the other speaker (941) is fine.
TESTING:
We have had this system for yonks, never given us any concerns and in fact I personally liked these more than my Monitor Audio S2 (England) and Dali's (Denmark) but now that I have removed these from the cabinets, I could get a much closer look at them
WOOFER #1 (919):
This is the speaker which shows oxidisation at the rear of the surround (partial)
Cone is A1 - nothing untoward at all
Dust cover is undamaged, no holes or creasing/deformities
Support and spider are also A1 - no holes, no damage
Gentle cone movement testing: this was interesting...although I heard nothing when playing music, when I gently push the cone inwards I can hear a "rushing" sound, not a scratching noise though (which is the voice-coil rubbing the walls of the magnet well) It is as though air is being pushed out through the dustcover.
Also it is pretty obvious that the dust cover is a strange colour, I have NO IDEA why! There are no holes in the dustcover or other signs of issues - it is just a sort of brownish colour, I have no explanation for that.
Speaker measures 4.6 Ohm DC voice coil resistance (NOT impedance) and 0.32mH inductance
WOOFER #2 (941):
NO oxidisation has occurred to the rear surround - I managed to remove the plasticine gunk without lifting the enamel!
Cone is A1 - nothing untoward at all
Dust cover is undamaged, being without creasing or deformities but right in the centre I can see this TINY hole - WHY a hole? This is usually a trick used to "pull out" a deformed dustcover but I can see no signs of the dustcover having suffered past damage, just the little hole.
Maybe it is intended to reduce that "rush of air" sound I heard with the other woofer? Who knows....
Support and spider are also A1 - no holes, no damage
Gentle cone movement testing: absolutely no issues observed or heard at all, smooth as a baby's bum!
Speaker measures 4.2 Ohm DC voice coil resistance (NOT impedance) and 0.26mH
OBSERVATIONS:
Actually I did notice that with BOTH of these woofers, the cone movement is particularly smooth and responsive. Some larger speakers can have very stiff cone movements and the resulting sound is "harsh" but these woofers sort of float, truly nice to see them moving! This could be why I liked the system so much, the tweeters and mid range are not really "sound killers" but these woofers save the day, very nice indeed.
Regarding the voice coils and the different dustcover colour plus that "rushing air" sound, I am now suspecting that sometime ago (before I got these in the 1990's) someone changed the voicecoil - it just seems strange that the electrical characteristics of each voicecoil differ so much but then again ... maybe it's a 1970's thing, that period was a bit like that!
*** Where the photograph shows multiple loudspeakers, this advertisement is for ONE SINUS loudspeaker only - not all that are shown! ***
This loudspeaker has now been placed "cone down" onto a stiff cardboard backing and sealed within clear plastic to protect it until a new owner is found.
