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CF-4 crossover rebuild, upgrades, et cetera


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I'm new to the forum. A few years ago I purchased a mint set of KG-4's. I had always wanted a set as a teen and was not disappointed. One thing led to the next and I finally hunted down a set of Epic CF-4's. They are Version 2's, October 1994 build.

 

These speakers are phenomenal. I'm running them with a Bob Latino VTA ST-120 tube amp which I build about 18 months ago.

 

I'd like to do some work on the speakers and looking for feedback and suggestions. I've seen a few posts by Moray James on the subject, but it seems to be bits of wisdom here and there (I don't think I've amassed the bits). The things I'm wondering ...

 

1) Crossover networks are due for rebuild, at least the caps. Recommendations? Is there a schematic or parts list? I suppose when I open them up I could figure it out, but wondering if this is documented.

 

2) Bracing - I've seen some commentary on firming up the cabinets.

 

3) Sound deadening - again seen comments about Dynamat on the horn shells, and some other things.

 

4) Compression drivers - I have a set of EV-1506 sitting around. Should they be pressed into action? If so, any changes that should go with them? Or if staying with stock compression drivers ... anything need to be done with them?

 

5) Version 2's have the 2.5" ports. Should I go back to 5" ports of Version 1? if so, what's the change to the crossover necessary to go back in time.

 

Finally on the amplifier ... it's a 60wpc tube affair. Great sound, but I'm thinking these speakers need a high quality solid state amp with mojo, to eek out what they are capable of. Power on hand with the tube amp is likely not up to the task.

 

Thanks for any feedback or thoughts you can share!

 

Filippo

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Boy, did you ever post at the right time!  (BTW, welcome to the forum, yadda yadda, but let's get down to business!)    :) 

 

I finished my CF-4 ver1 yesterday.  That would include bracing and installing the EV DH1506.  I have very specific notes and some observations on sound quality.  I plan on updating a thread I made on the CF-4, I just haven't gotten to it yet.

 

This is the CF-4 box with stock bracing, and the polyfil I use instead of the stock foam sheets.

 

post-58280-0-54060000-1431220692_thumb.j

+++

 

Be sure to read the post by AlexG5775.  He did the same mod to his CF-4. (he had version 2's)

https://community.klipsch.com/index.php?/topic/151115-epic-cf4-mods-amp-rack-build/

 

Then we'll talk.  B)

Edited by wvu80
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1) Send crossover to Bob Crites

2) See thread bellow

3) See thread below

4) See thread below. 

5) I tried the 5" port and i did not notice a huge difference so i just left them as 2.5. But yes, you can switch them to 5" deep and see what you like. 

 

Does that tube amp have a preout? If it does, biamp, with tube amp for the tweeters, preouts to give signal to the SS amp for the woofers. Make sure you remove the speaker cable that links the tweeter and woofer input on back of crossover. I would go with a SS amp with a gain knob in the front. I went with a crest ca6 and works very well. There are many similar pro amp you can probably find on your local CL. YGPM and lmk if you got more questions.

 

Also, try a search to find more info.

 

https://community.klipsch.com/index.php?/topic/151115-epic-cf4-mods-amp-rack-build/?hl=%2Bamp+%2Brack

 

Alex

Edited by alexg5775
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I built a VTA ST-120 which is currently pushing the CF-4s. No pre-outs. I'll probably go straight solid state. Not sure I want to tackle bi-amping.

 

IMG_20140126_130228%253Anopm%253A.jpg

I've read the threads. A good start for sure.

Lots to ask. On the crossovers not sure why they'd need to be sent out. I'm solder friendly ;-). Seems like an easy refurb if parts selected. Am I missing something?

So 2.5" port stays? I heard that elsewhere, too.

How exactly are the 1506 braced - what's that gel stuff? Looks like they should be bolted to a brace .... HEAVY!

 

Wvu80, I happen to be fishing in WVa. Head back tomorrow to VA. Looking forward to seeing you post notes and photos.

Thanks for the warm welcome!

Filippo
 

Edited by fmorelli
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On comparisons ... or putting these puppies through their paces, I was partial to Diana Krall - the album, "The Very Best of Diana Krall" and spool up the tune, "Peel Me Some Grapes". You might also try, "Frim Fram Sauce" off the same album, an old Nat King Cole song, but I think Diana really makes it sparkle.

 

I love the CF-4 sound. If I had to make critical observations, they would be ...

- while headroom is phenomenal, as is the detail, they are almost too harsh in the brights at times. And I hate to generalize, but that's with a tube amp.

- the sound stage is almost in front of the speakers, not at the speakers. This may be the crappy listening space I have them in. But they seem to almost forward project somewhat.

 

Those comments made, the OMG realism is something else.

 

Filippo

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Wvu80, I happen to be fishing in WVa. Head back tomorrow to VA. Looking forward to seeing you post notes and photos.

 

Mustang Guy, also from WV is a fisherman.  I bet he weighs in at some point on fishin' in our beautiful state.  ;)

 

It's late and I'm headed to bed, so more later.  I think between a few of us here, we can answer all your questions.

 

I have pics of the bracing, and I think I can give you a lot of details of some things that worked, and other things that didn't seem to work in terms of being able to actually HEAR a difference.  I modified one speaker and kept the other stock for over a month and played them at the same time so I could tell what the differences are.

 

I don't have tests and measurements, but I have a pretty good ear and I try not to be biased in "hearing" improvements that aren't audible.

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Hey Filippo: welcome to the forum. Great loudspeakers you have there. If I had a set of CF4 parts I would build new cabinets from the ground up in a WWT configuration rater than the stock WTW of the CF3/4. The CF3/4 horn is a really good one I like to think of it as the poor mans K510 only with a one inch throat. The horn itself is a great design but it is a cheaply made horn and has little strength the walls are so thin they flex and if you want to run the DH1506 you will need a hangar or a cross brace to take the weight the horn will not it will break. I don't use my horns any more I use Karlson K-Tubes with double cutaways and I run them with EV DH1A drivers . If you want to stick with the stock cabinet and you want to brace it I would recommend more brace work than what mot people install. I have attached a link showing a good solid brace job inside of my Quartet cabinets. Leave the bottom of the cabinet alone and you will want that space for your crossovers. Bob can sell you fresh capacitors or you can buy better ones. Film and foil stacked are a good starting place. Better caps better sound also you can upgrade the auto transformer there is the German one on ebay and Dean has some larger than Klipsch versions which would be ok for upgrade too and they are closer to home. You should try listening to your horn positioned up centered at your seated ear level to get an idea as to how the speaker can stage and image. This will give you an idea as to why I prefer the WWT set up as it gets the horns up where they should be. Time align the horn with the woofers you will be pleased that you did. Pull the horns install some blanks and stick the horns up on top of the cabinet and experiment for a while and see what your think. I like to use some 25 - 30 PPI open cell foam in the throat of the horns and I like to use a ping pong ball in the horn I hang it on thread so it is just in front of the transition section (right after the first conical section) with about 3/8" space on either side of the ball to the left and right horn wall. That ought to get you rolling. Best regards and please do keep us all posted as to your results and thoughts Moray James.

http://www.audiokarma.org/forums/showthread.php?t=372783&highlight=klf20&page=3

Edited by moray james
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I will take the mods one at time so each one can be dissected and discussed.  I did my mods one at a time on ONE speaker because I wanted to compare the mods to stock.  I wanted to hear a difference considered all the work I did.  Some things worked, some did not, at least to my ears, in the non-scientific way I tested.

 

BRACING Summary:  Bracing doesn't help the sound, but it is needed to support the larger compression driver.  Bracing  makes no audible difference in listening to music.

 

The stock CF-4 has two 1x3x15" hard wood braces which run horizontal from left-to-right.  Two additional horizontal braces were added.  One was rubber damped and kept in place on one end with glue, some small screws and have some pressure loading on the other end.  The support brace for the DH1506 Compression Driver (CD) is glued and secured with screws on both ends.  This gave me three horizontal braces, with the top brace being doubled up in strength.

 

This pic is from the perspective of the bottom, looking towards the top.

 

post-58280-0-77320000-1431264251_thumb.j

 

The compression driver/horn sets into the space between the double brace on left, and center.

post-58280-0-30520000-1431265928_thumb.j

 

I added a single 1x3x42.5" brace from top to bottom. You can see the rubber biscuit at the top of the brace.

post-58280-0-37080000-1431265965_thumb.j

 

The vertical brace was offset instead of being exactly in the middle.  The brace could have been symmetrical if placed on the bottom of the horizontal bracing, the longer DH1506 prevented the top mounting.  The top was pressure loaded with a 1/16th rubber biscuit made out of a rubber hose I cut up with scissors.  The brace was glued and screwed into the bottom, and glued/screwed into each of the horizontal braces.

 

The most important brace is easily attached just under the where the DH1506 rests.  I left a 1/16" gap between the brace and the CD so there was a piece of hard rubber on which the CD would rest.  I supported both the top and bottom, but did not attach rubber  side-to-side.  The rubber touches the outside of the CD which already has its own rubber wrapping. 

post-58280-0-24160000-1431266387_thumb.j

 

It was not possible to attach the bracing around the CD's throat.  In listening tests I could not hear any detrimental change in the sound.

 

The 42.5" horizontal brace is placed face down across the braces, and offset closer to one edge to allow clearance for the DH1506 which is very deep compared to the stock and much lighter K-63-KN.

 

Screws:  If you haven't discovered star drive screws, this would be a good time to start.  :)  I use #6x 1 1/2.  It will not split your MDF, they are self starting (no pre-drilling) and the bit does NOT slip.  You can pound it in like a nail to start it, then use your cordless drill with the star bit.  With SPAX the drive bit came in the box with the screws.

0de9bfb4-b436-4394-b189-648b56a04f57_400

http://www.homedepot.com/p/SPAX-6-1-1-2-in-Blue-Zinc-Medium-Density-Fibreboard-Screw-315-per-Pack-4351010350406/202040978

 

+++

 

Listening test:

 

The stock cabinet will vibrate noticeably at louder volume.  I could put my hand on the top or sides and there is significant vibration.  Sound wise, it's almost like the sound envelopes the entire speaker box.  Good or bad, that's what it does.

 

The highly braced speaker vibrates just as much as the stock speaker, tested by the highly subjective "hand on the speaker while playing loud" test.  I also did the "knuckle rap" test and I could hear no difference in the pitch from one speaker to the other.  Where the braces physically attached the knuckle rap had less resonance, but not much.

 

In listening to the speakers stock to modified, I could hear no audible difference.  Still if the compression driver is being swapped out for the EV DH1506, at least one brace must be added to support the extra weight, so some of the bracing is needed.

Edited by wvu80
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Opening the box:

 

The front baffle is screwed on and comes off very easily. 

 

In terms of sequence, I suggest:

 

1.  Remove the drivers, starting at the top, middle, then bottom.  The ports do not need to be removed.  Use your powered drill or screwdriver to remove the screws.  Four per woofer, 8 for the CD.  The wires are attached as marked, plus to plus, minus to minus.  The GREEN stripe is for the Pos on the CD.  The woofs have RED stripes for Pos.

 

2.  Remove the six rubber grommets where the grill attaches.  Dig them out with your fingers and pull.  You can also safely use some needle nose pliers if they are too tight.  They should pull out easily with no chance of tearing.

post-58280-0-35880000-1431272232_thumb.j

 

3.  Remove the SIX screws under the rubber grommets.  I covered the entire top of the box with cardboard to protect the woofers.

post-58280-0-91760000-1431272263_thumb.j

 

4.  Remove the TWO screws in the center.

post-58280-0-72480000-1431273807_thumb.j

 

5.  Gently rock the baffle and it should lift off easily.

 

6.  Note there is some still clay-like pliable gasket material around the outside edges.  I removed mine.

post-58280-0-11840000-1431268258_thumb.j

 

I replaced it with Rope Caulk.

http://www.homedepot.com/s/rope+caulk?NCNI-5

 

This is what I used:e4ed3767937000d95faeda5994c50414a8946c38

I used a knife so I could use only ONE strand of the rope caulk.  The single strand did not work well for me because the baffle did not seat as flat as it should have.  That may have been because my rope caulk was older and not quite as pliable as new.  I would suggest you flatten the rope caulk before re-seating the baffle.

Edited by wvu80
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Moray James, thank you for taking the time to post and share. First off I completely understand your WWT perspective - a night and day difference when listening to these speakers sitting versus standing. WWT would be more practical, but I'm not looking to go down the rat hole of building a cabinet (though it is an enticing idea).

 

Are there any specific suggestions on capacitors and autotransformers? I'm unfamiliar with "the German one" and "Dean", though I did some searching to no avail.

 

Filippo

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Are there any specific suggestions on capacitors and autotransformers? I'm unfamiliar with "the German one" and "Dean", though I did some searching to no avail.

 

There is no autotransformer in the CF-4.  It is located on the back of the speaker terminal block.  Here is what is looks like:

post-58280-0-92200000-1431316496_thumb.j post-58280-0-68680000-1431315902_thumb.j

post-58280-0-58480000-1431315917_thumb.j post-58280-0-35880000-1431316692_thumb.j

 

I have not modded my cross over (XO).  AlexG sent his off I think.

 

I also think the general suggestion is to NOT change XO values, just upgrade the stock caps for higher grade ones, even when swapping out the stock K-63-KN for the EV DH1506.

+++

 

Not tonight (for me), but at some point I would like to hear some discussion/suggestions on changing XO values when using the DH1506.  My question, is the DH1506 being used to its full capacity, or is it crossed too high?

 

The spec sheet for the DH1506 under General Specifications Frequency Response 500 to 20,000 ( essentially  flat from 500hz to 3Khz with controlled rolloff beyond...), and the recommended XO is 800 with the proper horn.  The KN-63 is crossed at 1500hz.

 

EV DH1506 spec sheet

dh1506.pdf

Edited by wvu80
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"The DH1506 is flat from 500hz to 20Khz"

 

Do you know how to read a data sheet?

 

The 1506 drops like a rock above 3Khz or so, and is about 15dB down at 14Khz, with a big resonant peak above there.

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"The DH1506 is flat from 500hz to 20Khz"

 

Do you know how to read a data sheet?

 

The 1506 drops like a rock above 3Khz or so, and is about 15dB down at 14Khz, with a big resonant peak above there.

 

Uh, no.  :blush:

 

I just re-read the Data Sheet in the first paragraph under General Specifications.  It says "essentially flat 500 Hz to 3000 Hz."   That was a whopper of a misunderstanding.  Thanks for the correction.  :emotion-21:

 

Later on in the RECOMMENDED EQUALIZATION section, it goes on the say "the DH 1506 can be made essentially flat to 20,000 Hz by using a simple smooth filter."

 

After reading the rest of the Data Sheet where it recommends XO and EQ info, do you have an opinion on the DH1506 when inserting it into the CF-4 network?  Any suggestions?

Edited by wvu80
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"do you have an opinion on the DH1506 when inserting it into the CF-4 network? "

 

I don't see the point in doing it.

 

" Any suggestions?"

 

I think the newer DH2 diaphragms may be made to fit the CF4 HF driver, that will give more sparkle on the top end.
 

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"do you have an opinion on the DH1506 when inserting it into the CF-4 network? "

 

I don't see the point in doing it.

 

" Any suggestions?"

 

I think the newer DH2 diaphragms may be made to fit the CF4 HF driver, that will give more sparkle on the top end.

 

 

According to the time stamp on my computer you responded at 4:00am so I understand it was probably a little late (or early!) when you posted.  :lol:

 

If you get some time, could you expound on your point that you don't see any reason to modify the CF-4 XO for the DH1506?  When Alex G sent his to Crites, I believe just the caps were replaced with better quality of the same values, which would reinforce what you suggested.

 

At some point I wanted to open a discussion on the DH1506 mod.  I have mine inserted as a drop in but I don't hear the "magnitude" improvement Moray suggested there would be.  There could be a variety of reasons for this, including my aging ears, but I question whether the XO needed some tweaking to get the most out of the CD.  It seems to me the DH1506 has some more potential than is being used.

 

I'd also like to hear your thoughts that the newer DH2 diaphragm might fit the stock K-63-KN CD.  I had not heard anything about that before now. 

 

Crites used to replace K-63 diaphragms but that is no longer an option, and I presumed replacement parts were not available.  On his web site he stated it was somewhat complicated and not a DIY job, sending the CD to him was recommended.  Since parts are not available, that seems like more historical information than current practice.

Edited by wvu80
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The discussion on the 1506 would be interesting, I certainly agree. Would be nice to baseline what specific components are actually in the crossover network. On my end I suppose eventually I'll have mine apart and sort out what's what.

 

BTW really good reference on the self tapping screws. I'll keep that in mind.

 

It would be interesting to start sorting out some of the different perspectives. One that has clearly jumped out is bracing versus not bracing the cabinet.

 

I will probably redo my grill cloth while I have everything apart. There are a few small holes. As well these were in a smoker's home. I intend to clean the cabinets with Murphy's Oil Soap, unless someone has a better idea.

 

Thanks,

 

Filippo

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Moray James, thank you for taking the time to post and share. First off I completely understand your WWT perspective - a night and day difference when listening to these speakers sitting versus standing. WWT would be more practical, but I'm not looking to go down the rat hole of building a cabinet (though it is an enticing idea).

 

Are there any specific suggestions on capacitors and autotransformers? I'm unfamiliar with "the German one" and "Dean", though I did some searching to no avail.

 

Filippo

[/quote

Hammer your front baffles out and replace them with new WWT ones. Bob Crites will CNC cut you a new set in Baltic Birch ply for cheap perfect fit. What's hard or expensive about that?

I finally included the link above so you can see how I braced the Quartet in the post above. This method insures that none box panels cannot resonate ate anywhere near the pass band of the woofer(s). Brace work is very much worth your time and effort but you need to brace all the panels and add extra brace work to the baffle where there will be the greatest amount of flex with the driver energy. Again leave the bottom of the cabinet alone as it will be the only place that you will have to install your upgraded networks later.

A panel brace should be 1x3 (on edge) so if you want to use say 3/4" ply for your braces make them 3/4" x 2 5/8" your strapping to tie all the braced panels together so the cabinet cannot flex should be 1x2 which is actually 3/4" x 1 1/2" you can use just about anything for this scrap ply or fir strapping just glue in place. Edited by moray james
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