duburonf@gmail.com
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Now lets look at the RB-5 Horns On the left is the K-124-K Horn used in the RB-5 II On the right is the K-105-K Horn used in the RB-5 Interesting that the only difference i can see visually is the way the ribbing of the horn casting is formed. Looking at them at first glance I would expect the K-124-K horn casting with the extra bracing runs branching off the main ribs (in red) would sound more subdued or muted that the K-105-K casting with its single deep ribs (in yellow). The surprise was after tapping both horns with the handle of my screw driver revealed that the K-105-K horn was the more muted or dead sounding. Not very hi-tech and it would not reveal what happed at higher frequencys. I still found it interesting. Anyway... I had never run across a comparison of the two horn structures so I thought I would post the pictures for discussion.
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THANKYOU AWESOME!
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HI AMPED great post you made on November 3rd last year (pg2 of this thread)... by any chance... do you still have a copy of that RB-5 schematic that you can post???
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Here is another issue to mull over... Picked up a pair of crossover boards to use for a recap project I believe that the P/N: 116436 is for the RB-5 and P/N: 116487 (the new pair I got) are for the RB-5 II. Can anyone confirm? I will say this about the two crossovers, the overall board condition of the new right-hand boards (one is shown) was dreadful. It has been cleaned and is ready for reassembling to backplate. P/N: 116436 - Looked like it had a better enviromental life Better Connection Hardware (no rust or corrosion evident) 18 AWG wiring to horn and driver P/N: 116487 Back of Circuit Board (CB) had solder connection crude - had to use Electrical cleaner and a copper brush to clean the crude off the solder joints. Connection Hardware (CB hold-down screws, "CB to backplate" connector jumpers, nuts and lock washers for back plate) had traces of rust on them. 14AWG wiring to horn and driver WIth Credit to "AMPED" on his November 3rd post on page two of this thread It is also my understanding that there are three caps to be replaced. a 20.0 mfd cap (the black one) and two red Mylar caps. - The small red Mylar cap between the chokes is a 3.0mfd cap - The large red Mylar cap under the black one is a 12.0mfd cap My choices are SOLEN CAPS (5% TOL), Dayton Audio (5% TOL), or Dayton Audio (1% TOL) Is this also correct? I may have a second pair of RB-5 speakers here in the near future. more to come
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JJPTKD Sorry I was looking back over this thread tonight and reprocessing the wonderful information that was shared...and I tripped over this section of the thread. I WAS IN ERROR. I was having a bad week and took it off in a weird direction. You are 100% correct and I was trying to make a point that was not entirely on track with what you were trying to tell me. Ya I know better now. Thanks for your patience.
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Just to close the loop... I restore a lot of vintage speakers... I have some good ones too I am slowly realizing these RB-5s are some dynamic and wonderful speakers to listen to. I completely agree they do not need a Subwoofer. I am listening to Boz Skaggs "DIG" cd tonight and they are just blowing me away. Very happy with them
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Interesting... I did find issues with the "cheap assed" spade connectors on both the diaphragm and woofer. This might have been the source of the original problem. i had to gently crimp the connectors down for a tighter fit on the spades. I would need to reinstall the original components to see if that was the problem. I might not as they are singing now!!
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I am really interested in this observation. We hear so much about the fabled legendary RB-75.
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I have two sets of KSB-3.1 speakers and they out perform my restored bookcase collection (EPI M50 (3 pairs), Baby Advents (2 pairs), AR-18b (two pairs), AR-18s (2 pairs), Boston Acoustics A6 (one Pair), AR-28S (a single orphan)) Don't let those metal grills fool you. These are great speakers!
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Pictures of the spare stuff I have... Keeping all this for now. Probably going to pull the crossover apart and check all the components and rebuilt it. The horn will be a good platform to compare aftermarket replacements.
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Update... I located both a replacement K-105-K horn assembly and a Klipsch 2-way Speaker Crossover (PN: 116436) off eBay. I did a "shot gun" replacement of both parts on the suspect RB-5. It's now alive and making beautiful music. I also remove the round grills and did some cabinet repair to fix the reamed out MDF material the cretin created when he muscled the four screws in. The grills were reinstalled using carefully sized nylon standoffs under each of the four grill hold-down lugs to fix the geometry
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THIRD TIME... Depends on how the results are posted... The manufacturers tend to list the nominal impedance which is the average ohm reading when a signal is present to the tweeter which is "DESIGNED" to be 8 OHMS! If you slap a VOM on it and check the STATIC RESISTANCE (DCR VALUE) you will not get 8 ohms... but something else. The Crossover is designed to work in harmony for the desired sound based on the speaker components (drivers, tweeters, ports, enclosure volume,...) to make it all work. The trick is what type of impedance value are they posting for our consumption... Is it DCR or nominal (average)??? I consider this 4 ohm vs 8 ohm issue closed for now.... I am sure that someone with a additional audio engineering will step in and at some point add additional info to this discussion. such as the Thiele/Small parameters
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You missed the point of my last post... a VOM meter puts DC across the K-105-K tweeters and give you a DCR reading of 3.1 to 3.3 ohms. The SS Tweeters give you a DCR reading 6 ohms and 6.5 ohms. The 8 ohms spec is what the manufacturers tend to list the nominal impedance which is the average ohm reading when a signal is present to the tweeter. You slap a a VOM meter on a new SS tweeter and it will give you a DCR reading of roughly 5 ohms according to the guys at Simply Speakers. That is still an a difference of 2 ohms. Being curious by nature...I have procured a spare K-105-K off eBay this evening and plan to order the replacement SS Part Number: D-417 to try it out in my lab to see what the differences might be. More to come...
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Not saying your wrong here... Every data sheet I can find on the RB-5 and RB-5II refer to the tweeter being a K-105-K. So naturally after opening my RB-5 up and finding a K-105-K inside I am assuming the RB-5 at least, did in fact, use the ones labeled as K-105-K. So for now let's just focus on the other aspect of a tweeter's condition... We need to keep in mind that static resistance check with a DC Voltage (or the "DC Resistance" (DCR)) is not a complete picture of the Tweeters condition The two SS replacement parts I listed as being 8 ohms (this is NOT a static DCR reading), but rather the manufacturer's listed "nominal impedance value" of 8 ohms which is the average ohm reading when an analog sinewave (or AC signal) is applied to the tweeters inputs. This dynamic resistance reading of a tweeter will change from 8 ohms according to the audio frequencies applied to the tweeter. Both of these SS replacement tweeters have a DCR value assigned of 6 to 6.5 ohms I am beginning to think... assuming a new tweeter starts out its life with a DCR reading of over 6 ohms, that DCR below a reading of 3.5 ohms might just be a good indication of why after 20-plus years some tweeters might not sound as dynamic as they were when new. A discussion with Michael Crites today left me much more aware of what these static DCR readings can indicate.
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This eBay item is for a K-124-K. I have a K-105-K tweeter in my RB-5. I just buttoned my Tweeter back in the enclosure, I will have to open it back up sometime tomorrow and check it. Yes both replacements are 8 ohm and I am wagering the K-105-K is also 8 ohms. More to come tomorrow... ~~~~~~ NOV 3rd - Update Tweeter on both speakers measured 3.1 ohms (DCR)
