DrWho Posted February 18, 2009 Share Posted February 18, 2009 This came up in another thread, so thought I'd share some resultshere. Sadly, it was a long time ago that I performed these mods and thecomputer I did the measurements on crapped out, but I might be able toreproduce them again. Anyways, I love my Chorus II's, but intheir stock form I've always felt that the bass was way too cleanalmost to the point of not being enjoyable. I also always wondered howKlipsch claimed a 101dB sensitivity since Hoffman's iron law woulddictate closer to a 98dB sensitivity. The K48 is an 8ohm nominal driverso its not like you can fudge the whole 2.83V as actually being 2W into4ohms....Thus, bring out the Chorus II brochure:http://forums.klipsch.com/forums/storage/4/1041389/Chorus%20II%20brochure.pdf Ifyou look closely, you'll notice that the entire woofer section is about3dB down from the HF, except for the very bottom where its tuned a bithigh to get a little bass boost (but it's still down relative to theHF). It's claiming that 0 on the chart is 100dB, so I'm not sure how torationalize that with my prediction, but the LF is still down a bit. Soall that to say, if you're running an active xover, you candramatically improve the LF on the Chorus II by bringing that woofer upa few dB. Couple that with the awesome performance of the passiveradiator and I think it'll give the Lascala II a run for its money (notto mention way better LF extension). That said, I've not createda new network that pads the MF and HF down to match the LF better. Withroom gain and the effects of a corner and all that, the lower basskinda gets built up a bit more relative to the other frequencies soit's not quite as bad...you kinda just get a little deemphasis in thelower mids where the top of the woofer's passband is. The otherthing I noticed with the Chorus II is the wild impedance responsearound 6kHz or so. Even with some acceptably low output impedanceamplifiers, you'll easily see a dB or two of emphasis at 6kHz...I thinkthis is mostly why a lot of people say that the Chorus II needs somejuice to have some low-end. What I think people are actually hearing isthe lower output impedance of the higher power amplifiers...which inturn will result in less of a spike in the frequency response at 6kHz.Less ringing crap at 6kHz means the bass is relatively louder, but it'snot really the bass that was fixed... My solution for thisbehavior was to lowpass the squawker at a slightly lower frequency. Idon't remember the specific cap value changes I made, but I canprobably look that up if anyone is interested. It should also be notedthat the squawker was exhibiting some extra output around 6kHztoo....so that in conjuction with the impedance effects really made itsound bad....low passing lower flattens the response too. Aftermaking those changes, I decided to experiment a bit with filmcapacitors too. Long story short, swapping over to films took a lot ofgraininess out of the mids. To be honest, I am surprised how drasticthe difference was. Now I'm not sure if the lytics from the early 80'swere already crapping out, but the difference it made in my applicationwas sufficient to be able to detect it without knowing that their werefilms in there. In other words, my lab partners had a lot of funswitching which Chorus II was connected to the amps we were working on(only one of them had the xover mods). Maybe one of these daysI'll get around to making a schematic of the changes I made, or mayberevisit and tweak things in further. However, going to actives broughtthe Chorus II's to whole new levels so I kinda wrestle with the thoughtof all that work....but I guess not everyone has 6 amplifiers and a3-way stereo xover at their fingertips... Quote Link to comment Share on other sites More sharing options...
michael hurd Posted February 19, 2009 Share Posted February 19, 2009 8 Channels, one box. 20 some odd pounds, SMPS. http://cgi.ebay.com/QSC-CX168-8-CHANNEL-POWERED-AMPLIFIER-90W-8-ohms-per_W0QQitemZ280313313319QQcmdZViewItemQQptZLH_DefaultDomain_0?hash=item280313313319&_trksid=p3286.c0.m14&_trkparms=72%3A1234|66%3A2|65%3A12|39%3A1|240%3A1318|301%3A0|293%3A4|294%3A50 Enough to do a 3 way active system with something like the Behringer DCX-2496 and have a pair of channels left over for say a sub or two. I forgot to mention, it's configurable from 4-8 channels, each pair of channels are bridgeable. Quote Link to comment Share on other sites More sharing options...
DrWho Posted February 19, 2009 Author Share Posted February 19, 2009 AB+B.....yuck? Crossover distortion city...and even moreso if you end up bridging it. Notice they only post distortion specs at full or near full output (it's only gonna get worse as you go down). Might be ok for a woofer, but a super efficient squawker ain't gonna be too happy. If you wanted to go the Behringer route, I'd invest in Sfogg's digital output mod and then feed that directly into that Panny digital receiver thing he's got going on...I think it's got 6 channels? Quote Link to comment Share on other sites More sharing options...
jwc Posted February 28, 2009 Share Posted February 28, 2009 Man. I just hooked up these Chorus II's where my LS II's sit. These are some nice speakers. And to think they are STOCK! OMG. Who.....not sure I'm gonna mess with actives on these to improve the bass. I think I will change out the caps to some savy overpriced stuff and have BEC do his tweeter diaphram thingy. I had heard Forte II's a long time ago and remembered really liking them. Never heard the chorus. I'm pleased. The bass is much diiferent that the cornwall despite the quote "chorus is a cornwall in another box". A Klipsch engineer once told me that. jc Quote Link to comment Share on other sites More sharing options...
IB Slammin Posted February 28, 2009 Share Posted February 28, 2009 Man. I just hooked up these Chorus II's where my LS II's sit. These are some nice speakers. And to think they are STOCK! OMG. Who.....not sure I'm gonna mess with actives on these to improve the bass. I think I will change out the caps to some savy overpriced stuff and have BEC do his tweeter diaphram thingy. I had heard Forte II's a long time ago and remembered really liking them. Never heard the chorus. I'm pleased. The bass is much diiferent that the cornwall despite the quote "chorus is a cornwall in another box". A Klipsch engineer once told me that. jc Well Mr. Deface the 1201 in your avatar, Please explain the LF difference in the two. (as to your ear) tc Quote Link to comment Share on other sites More sharing options...
Marvel Posted February 28, 2009 Share Posted February 28, 2009 When did you get Chorus IIs? I think they walk all over a Cornwall. The bass seems a lot cleaner to me, where the Corns seems a bit muddy. Quote Link to comment Share on other sites More sharing options...
jwc Posted February 28, 2009 Share Posted February 28, 2009 The chorus bass isn't as hard hittin. But "smoother"...not sure...just a few hours of listening. The tweeter is good...better than the CW. Now the midrange is not open like my la scala II's. An easy noticed difference. My wife walked in the room and said...."not near as good as those" (LS II's). curious what a cap upgrade will do to the mids. jc Quote Link to comment Share on other sites More sharing options...
DrWho Posted March 1, 2009 Author Share Posted March 1, 2009 You don't necessarily need actives to pad down the MF...but I think padding it down somehow is required to experience just what the LF can do....the passives just rock. The polar response of the midrange is definitely a lot narrower...not sure if that accounts for the openness thing or not? Quote Link to comment Share on other sites More sharing options...
MikeMilliken Posted March 1, 2009 Share Posted March 1, 2009 Please keep this thread going! I just got a pair of Chorus II's as well, havent even heard mine yet, just popped 'em with a 9 volt to make sure the polarity was correct and that all the drivers worked. I'd like to learn from your findings! Thanks, Mike M Quote Link to comment Share on other sites More sharing options...
Deang Posted March 1, 2009 Share Posted March 1, 2009 The midrange cap is a cheap electrolytic -- the midrange has no depth at all. I did Rick Flynn's Chorus II's on site at Audiokarma a few years ago, I thought it was a real nice improvement. I thought the sound was very well balanced. Regardless of the source material, I never felt the top was running away from the bottom. It's easier to work with placement than it is to modify the filter -- where even after modification -- you are still left with working out the placement issue. When I had the RF-7's, it was surprising the difference even a few inches made. Replacing the stock resistor with a Mills warms up the signature a bit as well. People don't like to hear me say that, but it's true. Quote Link to comment Share on other sites More sharing options...
MikeMilliken Posted March 1, 2009 Share Posted March 1, 2009 Any particular brand of cap you liked better Dean? Where is/was the best place to get them? Did you stay with stock values? Ever change to TI diaphragms on mids or tweeter? If so, did this make it necessary to alter the crossover values? On the mil specs, you got a source for them... and stock value or alteration? From reading what Mike Bentz said (I think it was him) , the mids needed to be padded down a wee bit. I wonder if that would be the case after the caps/diaphragms were changed? Thanks for all your help! Quote Link to comment Share on other sites More sharing options...
stormin Posted March 1, 2009 Share Posted March 1, 2009 The chorus bass isn't as hard hittin. But "smoother"...not sure...just a few hours of listening. The tweeter is good...better than the CW. Now the midrange is not open like my la scala II's. An easy noticed difference. My wife walked in the room and said...."not near as good as those" (LS II's). curious what a cap upgrade will do to the mids. jc Curious as to which speaker you are referring to. When you say bass isn't as hard hitting are you referring to your LS II's or Cornwalls. If it is the Cornwall do you have them there now or just thinking back? The best description I have for a Cornwall cranked up is a "rumble box"(Duke Spinner). I have found that the Chorus II has quite an impedance swing and actually loves power to improve the bass. At 500wpc it is hitting hard and appears to want more, unreal. I would hope your LS II has a better midrange for the huge price difference. I think that is one of the highlights of the LS is the midrange. Back in 1990 I felt the Chorus II mid was a huge improvement over what they had in the Chorus and Forte let alone the Cornwall. Then again I was not impressed later with their KLF's. I personally felt there was a backward movement in sound and development needless to say construction. IMHO but you know what they say about opinions. Quote Link to comment Share on other sites More sharing options...
jwc Posted March 1, 2009 Share Posted March 1, 2009 Replacing the stock resistor with a Mills warms up the signature Yes that is hard to accept but easy to do. Quote Link to comment Share on other sites More sharing options...
DrWho Posted March 1, 2009 Author Share Posted March 1, 2009 The Mills resistors are wire-wound so there's going to be a little inductance to them...I've not measured to see if this is a possible influence or not. The Mills resistors are also designed to be heat-sinked. Even the act of soldering will dramatically affect it's resistance...they behave like a really slow PTC, which when in series with a driver will behave like a compressor. Sadly, that compression is nonlinear with frequency due to the driver's impedance. Mounting them to a heatsink (which is required for their 50W power handling) dramatically reduces the thermal nonlinearity at lower levels. This is one of the reasons that autoformers/transformers are nicer for MF/HF attenuation... Quote Link to comment Share on other sites More sharing options...
Deang Posted March 1, 2009 Share Posted March 1, 2009 Hi Mike, what "Mills" resistors are you talking about? The Mills I'm recommending are non-inductive, have a 12 watt power rating (x10 for short burst), and do not need to be heat sinked. http://www.millsresistor.com/pdf/pg16prn.pdf Quote Link to comment Share on other sites More sharing options...
DrWho Posted March 1, 2009 Author Share Posted March 1, 2009 I was thinking of the MRC-50 available at Parts Conexion...but their website isn't working. Here's a similar part that looks the same:http://www.mouser.com/Search/ProductDetail.aspx?qs=sGAEpiMZZMuQ5%2fsBR7SoAutZHG5e2ETHeoTHGYVex6Q%3d The ones in your link look really awesome [Y] Quote Link to comment Share on other sites More sharing options...
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