Upgrade KG 5.5 ....................Better Than Khorn?

[Singlemania]

Was very fortunate to pick up a pair of KM6's (export version of 5.5's) in Germany from AFES around 97 not long before they were discontinued. The cabinets were stripped and wood veneered to cover the ghastly black vinyl! I have always had the upgrade bug and as fate would have it the baffles on both speakers became detached so I had the perfect excuse to delve inside and improve things. Judging by the the number of posts the defective glue seems to be a pretty established problem. I am a little disappointed with Klipsch customer support since I mentioned this to them a few years back and they said they were not aware of any problems with the quality control on the cabinets. For years I blamed myself for perhaps positioning them too close to a radiator but this is unlikely to have been the cause. Well as far as upgrading was concerned I first tackled the rigidity of the cabinet. Being such a large enclosure I am surprised it didn't have any bracing; which clearly accounted for the somewhat lively and colourful bass. I decided to partition the cabinet by separating the Horn from the Woofers. I used a sheet of 1" MDF with battons either side and glued this to both sides and the back. A small gap was allowed for the wire to the Horn. The resulting smaller enclosure for the Horn was dampened on all sides with bitumen based material and then filled with wool . A further half sheet of 1" MDF was glued between the woofers to add some bracing. It also provided a larger surface for the baffle to be attached to reduce vibration and increase tortial strength. Bitumen damping was also applied to the woofer magnets to reduce component resonance.The speaker units were wired with a mix of multiple strands of pure silver wire and OFC copper wire. I removed the crossover which is now housed externally away from any infection from vibration. The speaker terminals were replaced with a set of 4 silver plated audio note connectors to provide bi-wiring. The crossover components were upgraded for bi-wiring using a mix of Ansar and Volt components. The speakers have now doubled in weight and are a 2 man lift unless you are of herculean build. The increase in weight being mainly attributable to the damping material which is substantial if every there was an understatement! It was delivered to my house on an industrial fork lift pallet! The sound....well absolutely sublime. The brightness of the treble has been tamed and now sings sweetly without any harshness. Before the changes the bass was reasonably well extended but there was always a hint of boom from the cabinet and the midrange a little stark. I am pleased to say things have tightened up so much that I now have pieces of plaster falling in the cavity of my walls and the midrange warm and tuneful! Has anyone tried sand filling the cabinets below the port?

http://singlemania45.blogspot.com/ Some Pics

Tim

[STL]

I coated the back of the K-85-K horns in my KG5.5s with rope caulk, and that got rid of much of the harness. I have thought about bracing the cabinets, but unlike you I wouldn't do anything that would substantially change the internal volume of the cabinets. Decreasing the internal volume (and leaving the port untouched) means you're raising the venting frequency. While that will mean stronger bass output at higher (bass) frequencies; it also means less low end bass and a less linear frequency response (in the bass region).

[Singlemania]

Thanks. I played around with the port diameter at the time but as my listening room is relatively small and not resembling an aircraft hanger I did not detect a great difference in low end extension. Perhaps in a larger room your hypothesis would show through. The scale of improvement in bass quality to my ears is like night and day and I am now able to pick out notes that previously were obscured by the detrimental effects of the cabinet.

[STL]

So did you end up making a change to the port? In theory you'd need a lorger port (if keeping the diameter the same) to keep the vent frequency the same. You wouldn't want to make the port any smaller else you'd likely run into port noise issues. Also from your description, I'm not sure if your added bracing between the woofers has changed the airspace configuration -- meaning are the woofers still sharing airspace or are they effectively in separate enclosures now?

[Singlemania]

Well as far as the port was concerned I did something rather

different. Yes I did extend it but I used a novel method. I filled the entire

port with rigid straws which extended into the speaker and extra 2". I

have not taken any scientific measurement but rather relied upon my brother who

is a classically trained musician and also plays the church organ so I was

fortunate to have his trained ear discern any hump in the lower frequencies

which was eradicated by listening tests rather than electronic measurement. I

borrowed the idea of the straws from my old CELEF PE1 speaker. The

airspace configuration is slightly changed as you will see if you

visit my blog (see my initial posting for the address) where I have uploaded a

few images of the internal architecture. Its not a separate enclosure just

extends back about 9" from the front baffle.