1973 Yamaha NS 550 (tall boy) new Feb 2007PART TWO "Hallowe'en added September 2008 HERE
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I have always fancied getting hold of one of these early Yamaha loudspeakers featuring the odd shaped cast frame bass drivers. These drivers are so beautifully engineered and Yamaha have always been well known for making sturdy cabinets. I was expecting to find one of the smaller, shallow variants the NS 10, NS 15 or NS 20s since these seem quite common. It was a surprise then when I picked up a working pair of the larger 550s at the local Cash Convertors. They were complete, extremely heavy but in very ordinary cosmetic condition. The Salesman at the store seemed quite impressed that I knew a bit about something so old, but he was happy to be getting rid of something that looked so bad. They had been painted very badly with a range of nearly empty spray cans. The had black, silver, gold, pink red and blue paint patches all over them. On one the grille had been partly finished in gold. The other had a sprayed face that resembled Jesus. Jesus also appeared on one bass driver and there was a message making out that drug use was cool in silver on one side.
Good then that all drivers worked correctly. Internally it was completely correct. The original specs states that these are 90+dB sensitivity 8 ohm with a power rating of 36W. The boxes were completely stripped and all the Yamaha felt removed. The wooden cabinets were treated with a fairly potent chemical strip. Luckily most of the paint came off fairly quickly. The bass driver proved much more difficult. Citrus strip (oil of Orange) available at Bunnings worked a treat and did not effect the cone material
Hot work in the back garden
Following the chemical strip I gave the cabinets a light sand and then used the excellent Gilly Stephenson's dark restoration wax (available at Bunnings) The end results above Powered by my wonderful Sony VFET power amp below
A closer view of the preferred tweeter
How do they sound? Well in a nutshell, these are great speakers but deserve a better tweeter. The original tweeter JA 0505 has a 25mm aluminium dome but is simply too bright if not used with the inbuilt attenuator. I decided to change the crossover to a SEAS to get rid of this extra set of resistors. The SEAS uses very smooth sounding green polyester caps The JA 3505b bass driver is a wonderful driver. I dont think I have ever heard bass presented so naturally before. They may only have a 36W power handling but the bass notes are never forced or boxy sounding. The vocals are also highly detailed and very natural. I had a pair of expensive Kenwood "Carbon disk" tweeters which are much heavier than the original Yamaha dome. These were able to fit onto the back of the original ply frame. They are now much more integated and the Kenwood tweeter extracts much more subtle detail. The tall boy cabinet may look a bit "disco" but they have two internal braces and they are very strong. The drivers are placed at a perfect listening height without the need for stands THESE ARE GREAT SPEAKERS and easily as enjoyable (with this replacement tweeter) as the legendary NS 1000M
PART TWO BACK TO TOP HERE added September 2008 "Hallowe'en Speakers" Whilst the original Yamaha bass drivers are simply a work of ART one as it turned out had been quite badly cooked at some point and I have been unable to get it repaired. The original bits spent about 18 months having an extended holiday. I really like the quality of these old Yamaha cabinets so it was only a matter of time. I still have the original tweeters. The bass/mids have effectively become a forgotten repair. (they are still sitting at the workshop!) SO WITH HALLOWE'EN coming up I decided to build some party speakers. (Secretly I would really love to own a pair of Klipsch Heresy) so this is a move in that direction.
My new party speakers "Hallowe'en" I decided to use a pair of 12in Alnico ACE TONES. These had been re-coned recently and certainly seemed to suit the idea of a Pro audio type speaker. I finished them off with a pair of JAYCAR piezo horn tweeters. The following has been copied from the JAYCAR website Response RSN1142 Piezo CD Horn Tweeter Similar to the KSN1142 piezo. This tweeter horn combination is not like the conventional exponential horns that we commonly see which disperses the high frequencies on a very narrow beam, it utilises a Constant Directivity (CD) horn which offers a uniform frequency response dispersion through its multi- taper design. • Impedance 8 ohms
Response RSN1142 I have used an old SEAS crossover here to help remove any extreme top end. (By adding a 10 ohm resistor across the tweeter) http://www.talkbass.com/forum/archive/index.php/t-376190.html http://www.audiokarma.org/forums/showthread.php?t=79659 They are really very good, I think I have managed to bridge the gap between HiFi and Pro audio and they should have the ability to go quite loud. They are very heavy. Probably about 50-55kg each!
The Hallowe'en speakers sit either side of a crystal (red edge) Samsung 100Hz LCD screen. You can also see the GrandView screen for serious late night movie sessions. I use a Hitachi PJ TX200 LCD projecter. Disks and other gear stored on the left. Lots of cables run through the walls and ceiling Sunshine Coast Palms and cold beer behind the bamboo!!??
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