P Trap

[johnnyp]

Thanks, djk, for the link (above) to a most unusual PWK crossover design. Note: there is no autoformer in the mid circuit but there is one in the tweeter circuit where it is wired "inversely" to increase tweeter output. (this crossover is used for a new, super-efficient speaker designed to produce 108dB @ 1w/m). After reading the text accompanying this design, I believe the LC values shown in the squawker (mid) circuit to roll-off the high frequencies may not be the ideal values to use for AA crossover tweakers.

According to his text, the "L22 , C22 produce a rise at approximately 5,500 Hz." (PWK, page 9/10, lines 27 & 28). He has selected these LC values to increase output at 5,500 Hz in the mid circuit before they begin to roll off the highs. Likewise, the monster 128uF cap across the woofer terminals increases output at 350 Hz (page 9/10, line 25).

Crossover tweekers may want to experiment with a smaller value for the C22 capacitor (maybe 1uF - 2uF) to minimize the resonance at 5,500 Hz. Looking at the ALK design, I noticed he has chosen to use the L22/C22 combo before the autoformer in the squawker circuit. Don't know if this would make a difference.

[djk]

>>According to his text, the "L22 , C22 produce a rise at approximately 5,500 Hz." (PWK, page 9/10, lines 27 & 28). He has selected these LC values to increase output at 5,500 Hz in the mid circuit before they begin to roll off the highs. Likewise, the monster 128uF cap across the woofer terminals increases output at 350 Hz (page 9/10, line 25).

Crossover tweekers may want to experiment with a smaller value for the C22 capacitor (maybe 1uF - 2uF) to minimize the resonance at 5,500 Hz. Looking at the ALK design, I noticed he has chosen to use the L22/C22 combo before the autoformer in the squawker circuit. Don't know if this would make a difference.<< I wish people that don't know how to run resonance formulas on a calculator would not respond.If you would bother to run PWK's parts values you would see that he is dealing with the peak by filling in the dip below it.If you just decrease the cap value as you suggest you will increase the frequency of the peak right into the range you are complaining about.The >monster 128µF cap< across the woofer increases the response at 350hz to fill in the monster hole in the frequency response of a Klipschorn,Belle,and LaScala.That is why all the current versions of the afore mentioned models have this cap in their networks.As for >a new, super-efficient speaker designed to produce 108dB @ 1w/m)< that is a standard K33E woofer and that is how loud a Klipschorn is at 250hz.See the JAES article by PWK on the Jubilee last fall.It has acual frequency response graphs of both the Jubilee and the Klipschorn, not the advertising bs they hand out.Maybe you haven't read this post? posted 03-13-2001 07:44 AM

>> Thanks to Al for the graphs.I recommend you try the 230µH + 4µF on the K55V along with the 6µF change on the tweeter.PWK designed this to lift the falling response of the K55V before slamming it off hard at 5Khz.Because of the non-coincidence of the mid-range and the tweeter there are a series of dips and peaks on either side of the crossover point.Cutting the midrange off with a steep filter like this will reduce both the frequency spread and amplitude of these peaks.Just changing the second capacitor in the tweeter circuit does improve the sound but the full effect won't be there until you help the mid-range clean up its act too.As far as the 128µF cap in parallel with the woofer goes I have seen values from 100~140µF used.I have also used 68µF in parallel with the woofer and a Zobel of 6 ohms in series with 27µF and this combination also wired in parallel with the woofer.This last combination is the most benign for an amp to drive.The 140µF is the worst.Anybody having a real POS amp should use the 68µF with the 6 ohm + 27µF Zobel.Good quality electrolitic caps are ok for the woofer circuit although Klipsch uses high quality film types here.The 4µF in parallel with the midrange must be a very high quality film type.It should be pointed out that it is very easy to try the different caps on the woofer.Put a card table in front of one speaker at a good listening distance.Run a suitable length of zip cord from the woofer terminals out to the table.Wire one of the 27µF caps in series with the 6 ohm resistor.Set the other 6 ohm resistor to the side.Buss together one end of both 68µF caps, the second 27µF cap, and one end of the Zobel.With a bunch of clip leads from Radio Shack you can try both 68µF in parallel (136µF),a 68µF and a 27µF in parallel(95µF),and a 68µF by itself and with the Zobel.Keep the volume low but loud enough to hear what is going on.Whatever sounds best is best.This is a $10 experiment and the worst thing that could happen would be to find you liked the 136µF value the best and found you had to order another pair of 68µF caps.Otherwise you have enough parts to make two of every combo that you tried.<<In case this is not clear I will reiterate: the peaks and dips are greater than seen from the drivers themselves because of driver spacing.

[Al Klappenberger]

Hi Guys,

I managed to get very confused trying to follow what specific networks

everybody has been talking about here, so I will make a few general points.

Mainly that a second order filter can be made to generate a peak. This is

what could be thought of a "Tschebyshev" (Spelling?) lowpass filter. It is

possible to design for any peak you want by simply keying the desired

correction factor, in dB units, as passband ripple into a filter syntheses

program. This works because even order Tschebyshev filters exist between

unequal terminations making an impedance mismatch at DC and coming to a

matched condition at the peak. Any values of L and C can have any correction

factor you need (dB) by selecting the termination impedance. The L and C values

determines where the peak will be. The same values also determine where the

crossover (of the network, at least) will be too. In short, there's a lot of

interacting factors. A further complication is my "thing" of making constant

impedance networks. I found that I can easily make a Tschebyshev response on

the lowpass portion and a Butterworth response on the highpass portion of a

second order diplexer if I assume perfect resistive terminations. Getting

that takes some doing! It involves knowing the complex impedance of the

drivers involved and correcting for it (Zobel). This gets even harder when

there are two (maybe three) different bass horns involved (Khorn, La Scala

and Belle). This is why I am using first order filters for the woofer /

squawker transition. That way, the horns themselves determine the crossover

frequency and frequency response. This is how the "AA" network did it

(mostly) and initially what my network was inended to replace. Remember,

when the AA network was in production, it was used in the Khorn, Belle and

in the La Scala.

Both the designs I have up on my web site are Butterworth designs and assume

no passband ripples. This assumes a perfect resistive load by the drivers,

which of course, isn't necessarily the case. Anyhow, no corrections of any

kind are intended. The objective was a smooth transition form one driver to

the next and a constant impedance load to the amplifier. The curves I have

run so far show the response is not too bad. At this point I don't know if I

can improve it by employing these methods or not. I need to do more testing

to know. I have only had the equipment to do it for a little while and I

should go over everything again to verify that I did it correctly. I am

getting more proficient with the equipment now that I have been doing it a

while. In any case, I think any improvements would be guilding the lilly. My

main incentive for doing it would be that PWK did. If he thought it was

worth doing, so should I!

I would scan and post the curves I have made, but these are not sanitized

and make things look bad when they are not. I don't want the average non-

technical viewer to get the wrong impression of Klipsch speakers!

Al K.

[JLOUNDER]

Al K

The network in question was the Heresey 1's type E, and the installation of a trap that was discussed last year. Since all of the threads were cut I had to post the question again to get all of the details. pkeller responded with the information I was seeking. Since he has the same year Heresey's I have, I wanted to know what mods he has done and how it changed the sound of his Heresey's. I love my Heresey's but there is always room for improvement. That's the beauty of this BB, to educate the newbies what modifications can and should be made to improve the sound of Klipsch speakers.

I thought I was an average non-technical viewer until I read your response. I know I am going to have to do a lot more reading to get to average.

Jim L

[Al Klappenberger]

Jim,

Ok.. Sorry I don't have any direct experience with the Heresy. The Cornwall is close and I do have one of them. It's has the K57-K squawker which does not need the P-Trap though. That only needed for K55V Atlas drivers. I got into this thread late because I just didn't see it soon enough! Sorry.

Al K.

[pkeller]

I've tried to attach a photo of one of my rebuilt X-overs and a copy of Al K's Heresy "E" schematic. Neither attachment contains the "P-Trap". I hope this works.

By the way, below is a list of parts used for the crossover and P-trap.

X-over:

14ga 2.5mH Perfect Lay inductor(Madisound)

(2)2uf Northcreek Zen capacitors

T2A autoformer (Universal Transformer Co.)

P-Trap

.1 Heptalitz inductor (Solen)

3.0mh Northcreek Zen capacitor

[pkeller]

Here is the Heresy schematic that I tried to attach to the last post. Al K. posted it some time ago but it is no longer in the archives.

As for the numbers on the autoformer in the photo from the previous post, they are:

3619 0027 or it could be "OC27", I can't quite tell. It was ordered from UTC.

Paul

[Al Klappenberger]

Paul,

Only the 3619 number is important on the transformer. The other number is just a production run ID number or something like that. It's different for every bunch I order.

Al K.

[JLOUNDER]

Al K

No problem, you should be spending your time building the networks you designed. I've read a lot of your posts and have learned a lot, your contributions to this BB has been invaluable.

Paul K

Thanks for the detailed parts list, it makes it so much easier to order the right parts. I have yet to get my catalog from Solen, but will get to ordering as soon as it comes.

Than I can get started on my crossovers and sit back and enjoy the improved sound.

Has the mid problem you were having cleared up with more listening time?

Keep me posted.

Thanks again for all your help.

Jim L

[pkeller]

Actually, yes it has smoothed out quite a bit. I do have some Northcreek Crescendo .1uf 800v film & foil bypass caps on order to try in parellel with the 2.0 Zen's. I'll post the results when I get them installed.

At this point, I don't really think they will be needed, but I'll try them anyway.

The best description I can make between the stock crossover -vs- the new version is like the difference between pentode and triode tube amps. The stock network is like the pentode mode. More forward and centralized in presentation. The new version is like triode mode. More detailed and spacious, but less forward. Imaging is far-far better. It really takes advantage of naturally miced recordings.

Currently I have been listening using a very fine sounding rebuilt Dynaco ST-70 (I have three). Other amps I've used include Heathkit EA-2's, UA-2's, and Allen Organ #75's. All of them at partial or full restoration. They all do well with the new crossovers.

Hope this gives some perspective.

Paul

[Pete C]

The archives may be coming back. I tried a search of All and it looked through a folder called Archives. Maybe you can only get to them by searching? That would be okay with me.

[JLOUNDER]

Al K

After viewing your system in another forum I don't think you would have room for Heresy's anyway. If you have K-Horns than why would you need Heresy's?

Paul

Thanks for the update I was hoping that the caps would settle in with more use and mellow out some. The bypass caps might be another alternative to try to see what level they would take it to. That's quite a variety of amps to play with. You can get an idea of what amp works best with the type of music you like. I like the comparison using the pentode versus triode. I'm familiar with both triode and pentode and I think each one has it's pluses and minuses. Pentode has a little more drive but triode has a more liquid sound. Triode amps on K-Horns is breathtaking. One can only dream.

Keep me posted on the progress, hopefully I'll be up and going soon.

Pete C

I don't think we'll ever see the archives come back. It was a big source of information for all of the newbies(ME). It has been suggested they maintain them, however because of limited space they had to delete all of the threads.

Jim L

[pkeller]

For those interested, here is a photo of the Heresy 1 crossover rebuild. It is stock in component value and topography, but uses a 14ga Perfect Lay inductor and Zen 2.0 caps.

Not shown is the "P-trap" or the Crescendo .1uf bypass caps across the Zen's, that I currently have installed in my Heresy 1's.

Paul Keller

[Klipschguy]

Hello fellow Klipsch fans,

Sorry to get involved here, but you guys have me itching to tweak my 1980 Heresys. My Heresys have the K55V and a type E balancing network. My tweeter is the K77 with the square mud magnet. My question is how do I modify my network to include the PWK modification - in plain english. If PWK recommends the .23mH choke and the 4uF cap, that's what I want to use. How do I wire it, i.e. where does each end go (the previous explanations are a little confusing)? Also, with the Type E network, do I need the 6uf cap in the tweeter circuit and the 128uF cap in the woofer circuit, or will just the PWK P-trap suffice?

By the way, I love my Heresys, they are just a little "brassy" when compared the lovely sound of my Cornwalls, which are crisp, yet paradoxically mellow.

Thanks,

Klipschguy