KT88

Back story. MY 1977, bought in 2000, used for 6 years. Everything was original, somehow they got duller and duller. At that time I had no idea about ageing capacitors. Years later I changed to polypropylene capacitors because they are the modern standard and have such good properties as everyone says. But the spark was gone. So they were mothballed again. 7 weeks ago I activated them for the first time in years. Somehow the memory of the first years was different, the sound was warmer earlier. So much for the back story in a nutshell.I must say that I felt little pressure to optimise the Lascala because I have the Jubilees since 2008. But now I have gone through my small collection of all speakers, so much time at home since Corona... The Lascala with AA and polypropylene (PP) caps. I like the Lascala very much in principle. It offers such an even impulse over the frequency band that I hardly know from any other speaker. But the sound is a bit hard and edgy. The K400 sounds tinny. The 77 sounds hissy. I can clearly hear all three drivers separately. Intuitively, I listen quite softly; listening loudly to some music hurts my ears a lot. Especially rock and many instruments like in a large classical orchestra. I have avoided songs with soprano saxophone at all e.g. Some songs, on the other hand, are cream puffs. Silky, full and soft, beautiful vocals, some piano recordings. But woe betide an electric distorted guitar. I asked myself, how can it be that some kind of sound is so acceptable and other music is intolerable? The Lascala with AA and polyester (PO) caps. I am trying to give my subjective listening impressions because I have not yet found anything on the subject in this form that says more in detail about the polyester caps and their sound characteristics. But I think that the honest listening impression should not be neglected. It is not enough to say buy the Klipsch certified replacement capacitors which are polyester types, the same ones that are used in the current Heritage series today. What if I do it so that everything is historically correct, but it is done because of an emotion of safety, just because it is recommended? Personally, that would be too little strength of a reason. I would like to make an attempt here to describe these PO types as I hear them, independent of guidelines or recommendations. How did I come up with this attempt in the first place? I have read quite a bit in the forum here, the thousand discussions about capacitors for almost 20 years...And of course there are a hundred other forums with 10,000 posts about caps. Then I noticed in some threads here this relatively new movement that there are now Klipsch certified caps. I was sceptical at first...What on earth is a Poyester cap supposed to do I thought...a design that seems to be from the day before yesterday, or that is supposedly primarily used in cheap mass loudspeakers today. Add to that the fact that I have a Tannoy Canterbury from 1993, it also has polyester caps. And Tannoy is really kicking *** that they use clarity caps (PP) in the same speaker nowadays. You can imagine that all this does not help to accept why I should go the way of polyester caps in the Lascala. Add to this that I am not technically very competent. I am writing this because others may feel the same way. You hear a lot, you see marketing slogans, then it's the best Teflon caps because they have the fastest impulse, then it's silver or gold foil in oil. The best in the whole world. The gold comes from the legendary Inca treasure and was saved from being plundered by the conquistadors. The oil in which this special gold floats was already part of Cleopatra's bath concoctions. The connecting wires are made of pure silver that was mined in Colorado. Aliens wind the capacitors together in a secret place under the guidance of the spirit of Nicola Tesla. I will not deny that there are other very good capacitors that fit the AA and Lascala. But the message is that the electrical values must be correct as a prerequisite before one evaluates the perhaps great properties of a capacitor detached from it. In view of this, it is hard to believe that I should use polyester caps to make my Lascala sound original again. But there is another side, 1) because PO are quite cheap it may be worth a try, why not, 2) and that is the main reason. Chief bonehead has spoken on the subject a few times. That convinced me right away. Roy mentions that the cap must fit the Xover and of course the drivers. A supposedly "better" cap can be completely inconsistent. If the values (not the uF value but ESR e.g.) are not those that the xover needs in the interaction of all components then it goes wrong. If the overall impedance is changed, if the energies no longer reach the individual drivers in the intended way, if the phases of the individual drivers no longer work together, if the Q of the caps is too abrupt and thus the curves make the drivers sound too sharp, etc.. Because the original Klipsch certified caps are quite expensive with freight and duty, I tested with comparable PO, my motivation was now very high. On the market I have not been able to find the exact capacity values. Probably Klipsch has commissioned a large pile of specific values. I tried it in principle and tested with commercial values of capacity. 2.2uF for the tweeters and 2x6.8uF for the squaker. I know that again I change the ESR if I parallel 2x6.8uF, but I thought if it works well I can always order the 13uF from Klipsch's sales partner so I don't reduce the ESR. I consider the deviation of the capacitance values themselves to be relatively minor for the test, especially with the squaker because it's a 6dB circuit and I'm still in the tolerance range with 13.6uF. How was the hearing test with the PO: I initially changed only one speaker so that I could hear mono PP against PO. My first song was from the CD "Riding with the King" Eric Clapton with BB King, "Three O'clock Blues". Wow! Guitars sound like guitars are supposed to sound. I've been playing guitar in bands for 45 years, still do today. I know what my ES335 sounds like, my Bassman amp or Lespaul Standard, acoustic guitar, drums, etc. If you've been making music yourself for decades, no speaker can lie to you. Back to the song from EC and BB. With the PO caps, it was instantly fun to listen out loud again without the pain and discomfort. The annoying hiss of the K77 was gone. The guitar has punch and color. The voices are more natural, better said, they are natural now. Next I heard Getz/Gilberto, 1964, "O grande amor." It begins with a tenor intro. Very melancholy and at the end of the intro, before vocals enter for the first time, the tenor literally screams out. With the PP it was like running away from the room, with the PO it is a strong soulful expression. Next recording, Daniil Trifonov, "The Carnegie Recital" piano solo, life. With the PP it was so that the middle and higher piano notes always sounded a bit tinny. They stood out, the piano had no wooden body. My guess compared to the PO: It's really not just about the frequency response and equalising what makes the difference. With the PP the sound forms differently! The impulse is not even in the frequency band, some frequencies are "faster" others are lazier. Overall, one might be tempted to associate this sound with the metal horn K400 and project the "blame" on the horn. Often you can read that people want to remedy the situation by wrapping the K400 in tar paper or other measures. With the PO it was without exaggeration a different instrument. I have a piano in my room, I know how it sounds. Trifonov's playing with PO is melodic, warm, punchy, uninhibited and yet much more powerful. One hears much more the complexity of the chord vibrations with ease. Next, one of my favorite records. Herbie Hancock, 1975 life, "Flood" of which the title "Spank-a-Lee". It's about the first minutes, almost only bass and drums. It's a rhythmically very complex music. The interaction between both musicians is fabulous. It's the kind of music I should never try to copy. At best you would hit the notes, but you should find your own thing, it would never have the soul to try to copy this music. Why am I telling this? Somewhat exaggerated, it's because the PP are copying this music. One is satisfied when listening if one does not know it better. I was shocked when I heard it with the PO. Now it showed that with the PO the bass seemed much faster and lively. The interaction was stunning and lively. In a word, the Lascala have timing with PO that they didn't have with PP. With PP, the bass dragged behind (I mean the instrument, but also the frequency range). My conclusion, the change from PP to PO is not a small nicety, it is not "nice to have". It is a dramatic improvement that turns three drivers into a whole as a musical speaker. And it is not just an "improvement" in the sense of a new innovation but it is the rediscovery of qualities that were once a reality but which we can no longer remember after 40 years. My best acoustic gauge: My wife coming back home when I was done soldering and listening to the music. She just casually says, "Oh, now they sound right". Heinz

It looks like your crossover has no zener diodes. That's good. On the AA crossover of my Lascala, it's the two parts on the left of the picture, to the right of the coil, that are screwed into the metal frame. Yes, please let us know what happens next.

Your heresies look fantastic, it gives me goosebumps. And...you could have the highly sought-after Dual Phase Plug K55 V, which were only installed for almost one and a half year. You'll recognise them by the soldered connection cables instead of compression spring connections. Guard them like the apple of your eye. I don't know if I just admire them or if I'm a bit envious I would change as little as possible. I would also listen first before unscrewing all the chassis or the back panel. There are many possibilities for the capacitors. But I have noticed with my 1977 LaScala that capacitors that are good in isolation are not right in conjunction with the crossover and drivers. I have sonicaps and the squaker and tweeter are too loud and too edgy. Roy Delgado of Klipsch, chief engineer, has selected capacitors that are very close to the electrically important values of the original sheet metal enclosure types you have. I am currently in the process of changing my capacitors in this way. They will arrive tomorrow. If I lived in the USA I would buy the capacitors Roy recommends. You can get them from JEM. In the Klipsch forum under "modifications" you can find it at the top of the pinned threads. Personally, I'd try comparable polyester capacitors because shipping with customs would cost two and a half times as much to Germany. But if you buy the caps from JEM you have the right capacitance values (which are special!) whereas I have to piece it together. The background is that it is not about whether other capacitors would be better than polyester types. It's about the polyester types being the right ones for your crossover and your speaker! After all, the latest Heritage speakers that are getting praise all over the place have the same capacitors in them, as you can see in photos on the internet. Here's what I would do: Even if your tin can capacitors look good, have them tested by a professional. It's not just about the capacitance, it's about the ESR (equivalent series resistance). If it's all good, you're welcome to keep them, but I'm afraid it's not. Because even if the capacitors are still tight and dry, the inner workings may have changed chemically in 40 years...even if the original caps were also polyester in oil and not paper in oil. So if they no longer measure ok, I would buy the JEM ones if I were you, the reason is written above. I would tighten all screws of the horns and chassis very carefully. I would certainly change the red rubber sealing ring. It will have crumbled, at least check it. This seal is between the K55V midrange driver and the midrange horn. You just have to unscrew the K55V driver. Because the connecting wires to the drivers are soldered, simply unscrew the wires on the other side at the crossover. Then they can easily be unscrewed together with the driver. This gasket rubber is very important to seal the driver so you get the full SPL of the lower frequencies and to avoid an edgy sound. I wouldn't change the cable connectors to be honest, and I honestly think biwiring is nonsense. I would also leave the internal wiring as it is. But that is just my opinion One last point. My crossover type AA has Zener diodes to protect the tweeters. I do not know if your xover has also those Zener diodes. If you are not listening to gangster party volumes with 100 watts and if your amplifier does not make loud cracks when you switch it off and on, then unscrew one of the Zener diodes. The highs will be much smoother and nicer. You also have the K77 M, which is much more resilient than my old alnico K77. But...this last point is up to your responsibility. Other participants may have something to say about it here. What ever you do, never change the crossover for something else that is supposedly more modern and more „awesome“. You would lose the great original sound and the exceptional capabilities of your rare K55V with dual phase plug. I hope I could be of some help to you. To mention that in addition. I am not affiliated or related to JEM. JEM is simply the only dealer currently selling Klipsch certified capacitors. I do not deny that there are other types that would also fit electrically, and may have been wound by virgins in the moonlight. But capacitors are a minefield and with the Klipsch certified ones you are sure that they work as intended. This is what my sealing rings looked like after 44 years. The black ones are my interim solution until I get originals, I cut them from a rubber pad and it works fine.

What do you mean with „the sound is different“? Is it meant in principle, or in the sense that a self-biasing amp looks for the best operating point, and the manually adjustable amplifier can be fine-tuned a bit? It's sometimes done that way with guitar amplifiers. A somewhat "hot" idle current gives the sound more warmth and fullness, but the tubes have a shorter life. Conversely, a "cold" setting makes the amplifier sound (deliberately) harder and dirtier with longer tube life. These are all factors that should not play a role in hi-fi. The circuit of my MC275 MK4 is self biasing. MC traditionally has a relatively low anode voltage, I mean around 450V. And the circuit together with the special output transformers is unique. I would be interested to know why the new MC275 has a manual bias. I have a MC2102 from 2001 and it needs to be adjusted. Maybe because 4 KT88 per channel is a bit much for self biasing? But there is only one adjustment screw per channel so in any case a matched octet makes sense.. BTW it is a very unfortunate procedure. You have to unscrew the amp bottom and put it on the back side where the speaker terminals are on a soft pad. Inexperienced people have very quickly caused a short circuit if you get to the wrong pin of the V4 with the voltmeter, it unfortunately happened to me 16 years ago although I knew what I did but I slipped and a diode was fried. It weighs a murderous amount of 88 pounds. That's why it's an ordeal for customers who don't know anything about electronics if you have to send the amp in for this bias adjustment. Even worse I estimate that almost no one will be in the know of this measure. It's only described in the service manual but not in the owners manual. On the other hand, Mcintosh can't say it's a lifetime adjustment, because it has to be done every time you change the tubes in the MC2102. By the way, I suspect this missing readjustment is one reason… (among others perhaps, like the power transformer is not bigger than that of a MC275, or because parallel switched KT88 do not sound as good as only one per phase…yes more output current but less subtile?) …why its sound is sometimes rated less good in forums than the MC275. Ok, the sound signature is slightly different in comparison to a MC275 but many people might hear it after all these years and probably some tube changes without having been adjusted in bias. And it top form it is a very good sounding amp. The pic is out of the MC2102 service manual

A very good choice, Bubo. W126 was one of the best cars ever made in my view in terms of reliability, comfort, drivability, safety, rust protection (later ones were not as good until 2010 re rust. My father had one new in 1981, gas engine. We have a 1992 w124 coupe (in the US it was only available as a cabriolet as far I know) and my 1968 230 /8 since 1994, both cars I am second owner. Beside Merc there is a vintage car from Zuffenhausen in the garage which I imported myself from California 8 years ago, not an expensive trailer queen but a 1975 911S narrow body G model as a reliable driver to have some fun.

Yes, we like it a lot, with ham or a steak, cooked potatoes and hot liquid lemon butter. In Cologne sub area are quite some farmers around who sell their home grown Spargel (Asparagus). After all, they seem to strike a chord with the zeitgeist at Klipsch. As you say, the new generation loves vinyl, analogue touch and feel. That also fits in with the newer hand crafted movement. I love the USA and I have been to your beautiful country some times in the last 11 years when I could afford it, also in areas that are not only visited by tourists like Kentucky which I also liked very much and some areas look like my home in Westphalia in the countryside...but with a subtropical climate in Kentucky. What I noticed very positively in the USA already in 2010 was the movement of very tasty beer from small breweries, just as a small example. Another movement among young people is, many are climate committed and they want electric cars and not to drive themselves anymore (at least the young urbans, the people in the country urgently need their real cars). But I still have a 1974 vintage car and then my son goes crazy for it and want to drive it. Pure analogue.

Bubo, it started when I had a music teacher who also gave me piano lessons. I was 15, it was 1974, he had a MA230. Ok, with Bose 901 but at least the old Alnico version. Despite the speakers, the Mc sound was burnt into me. Regarding your question, brands like Grundig and Dual were very popular and successful after the Second World War in young West Germany. Grundig was a bit more for very normal people, Dual was a bit more refined but affordable for almost everyone. That was the mono era and Grundig made very nice tube radios for the kitchen and living room. Televisions, too, of course. Dual has always been a pure audio brand. I got my first mono record player as a gift from my father in 1966 when I was 7 years old, a very simple Dual, the lid was the loudspeaker. I loved it and listened to all the Beatle, Rolling Stones and other singles. In 1972, my father bought a stereo system, which only did a small circle of people in Germany at the time. He had dreamed about it for a long time. A Sansui QX 6500 receiver with Dual turntable 1219 and Braun TG1000 tape recorder and Sansui SP2500 speakers at the front, it was a pseudo 4 channel system. . Because our house was occupied by American army in 1945 as an officers' mess, my father had early contact with jazz music. He was hired as an interpreter by the Americans at the age of 15 because he had learned English at school; only a few children could attend a grammar school. Some of the military had record players and jazz records. That was the start and he this to him new sound. Grundig became less popular when the Japanese conquered the hi-fi market for the masses in the early 70s. Dual managed to hold on, primarily with record players. We subsequently had a 701 in the family, it was the first with a direct drive. I personally liked Thorens more. Back to Mc and Klipsch. At that time it was a very illustrious small circle that could afford something like that in Germany or even knew what it was. Since the mid 80s there has been a hifiscene that knows what these brands are. Mc stands for very high quality, but there is also a lot of expensive competition, also US brands were successful like Mark Levinson or Krell, later when tubes refreshed in the market also Conrad Johnson or Audio Research in addition to the sand amps. Klipsch Heritage series has always had a dedicated but small fan base, but most hifi lovers prefer a more comfortable and visually and acoustically pleasing loudspeakers with higher WAF if you know what I mean. Those who have money like to buy Sonus Faber or things like that. Klipsch is also quite well represented among these people with its Hifi series of slim towers. One must also take into account that most homes and living rooms are really smaller here than in US houses which is an issue to get a KH e.g. But I think that types like new Cornwalls or Heresy spaeker could get a renaissance. I don't know how Dual is doing today, Grundig is not relevant in the hifi scene and the younger generation does not know the brand any more at all. I have a positive feeling that a new generation is about to rediscover real and good sound which is associated with bigger speakers, horn speakers…the opposite of now still popular small bluetooth cubes. My son is of course a bit influenced by his father who built his first horn soeakers at the age of 16 and a KH bass unit when beeing 19. But he and his friends are very open minded to rediscover good sound when visiting my place at home.

Just my unimportant 2cents. I have heard a few tube amps over the last 30 years. Some are very impressive at the beginning. For example, I have an Audion Silvernight 300B in my small collection. What a holographic spatiality. Or old Leak Stereo 20. What a warm inviting sound, especially with older jazz and classical recordings. But at some point something starts to get on your nerves. Be it too little pressure with the 300B or a colouration with the Leak Stereo20 that makes everything sound the same. I have used other tube amplifiers. It's not so easy with the preamplifiers either. After various devices, the EAR 864 was my favourite for years. I had it connected to a Mcintosh 2102, a nice pairing. This power amp can still drive more difficult speakers well. But now I want to say which two amplifiers have stood the test of time over many years. Because...some qualities, that the amplifier becomes your friend and companion, I can only appreciate and identify over a long time. Of all the amplifiers, there are two models left that I can always listen to without getting tired. One is the Quad II, which is so beautifully balanced and so unagitated. By the way, it's fantastic with Klipsch Heritage speakers, no matter how old or new. The other is the amplifier that I have been listening to every day for 18 years now. It's an MC275 Mk4 from 2002, with the output transformers that Mk4 got first and that are still in use today. With the screw terminals and the adjustable RCA inputs (but I use XLR). I bought the 275 for €2,800 in Switzerland in 2003, it was only a year young used. I didn't want to buy more but the dealer had offered me an original sealed packed virgin C22CE preamp from 1996. Ok, I had bought it for 1.900€ and thought that I could surely sell it for that money. Back home I had it connected together with the MC275 just for a try. It had blown me away. Since 2003 I have never felt the need to have anything else than this combination of 275 and C22CE. Firstly, this balanced and fatigue-free very musical sound of this combination. On the other hand, the universality. From my Klipsch Jubilee passive to the small LS3/5a, the MC275 can really drive anything or at least most of not too exotic speaker loads. My favourite speakers, my 1977 Lascala are a marriage made in heaven with the 275. Even though I don't really need that much power. But the 275 is like a small V8 engine and the Lascala is like that V8 in a light agile sporty car. If I would invest 6000€ or $ today, it would be immediately again a e.g. MC275 Mk4 because it is not as expensive as younger versions but very good. I didn't like the 275CE from the 90s, it had different output transformers than the vintage versions from the 60s and worse than from the Mk4. And the new LED tube illuminated versions are not my cup of tea. A side effect that is not as important to me as the always musical sound is the safe investment. I wouldn't shy away from spending $1,500 more because I'm sure you'll get that money back at any time. Another positive aspect. You can hear a better tube. But the C22CE and the Mc275 don't sound bad with any tube. And...they are very gentle in the wear of the tubes. The power tubes last a long time because they are driven very conservatively. Sounds like I am a Mcintosh rep but I am only a satisfied customer.

What I find a bit crazy are the different ways of looking at things and evaluating them. One example. Let's take two markets and two target groups. One group is obsessed with the supposedly greatest sound increases through the supposedly best and most expensive replacement capacitors. They often forget whether the replacement capacitor fits the network at all when all parameters are taken into account and not just the capacitance. I have no objection to this, everyone should have fun with what they love and some people are doing it right even to care about all important parameter like overall impedance of the network. In my case it is not the desire for "sound improvement" but that I hear an imbalance with the sonicaps that can be technically explained…and or it is a matter of my taste . But on the other hand, products are judged as a whole and there is no question of urgently replacing capacitors or other items. Steve Guttenberg, for example, has made three videos about his Cornwall4. He loves this loudspeaker more than anything, he has reported sound improvements after the break-in period. He is absolutely satisfied. Steve is not at all the type to tinker with his Cornwall now. He accepts and values the product as it is. Incidentally, this has strengthened my decision to simply order the basic Mylar capacitors. I have seen on photos that Klipsch uses exactly the same Mylar type (with corresponding capacitance values) in the Cornwall4 that are also offered as original replacements by JEM for the old Klipsch models. Why should not be good enough for me what is built into brand-new and very successful Klipsch Heritage speakers today.

Thanks for advice. Before I go exotic routes I ordered mylars/polyester caps and I will polish the old Aerovox after cleaning and drying them:)

Deang, I thought the current midrange driver was an alnico Atlas again, like the K55V used to be. Only that Atlas now specifies a maximum of 4500 Hz for some reason. The modern tweeters are indeed different from the classic K77 and they run easily lower than before.

I have an AA Crites crossover with Sonicaps and I share the impression of some participants that the sound in the Lascala is not quite as I remember it with the original crossover. But the original Aerovox capacitors have been leaking for years and have the wrong values. (I don't want to start a discussion about the sound and the quality of the sonicaps with this thread, only about the possible changes via a resistor. It could be any polypropylene capacitor). Can I simulate a PIO at least approximately, e.g. with a 0.5 Ohm resistor (or other values) in series to the capacitor? It would change the impedance and also turn the phase a bit. Only...the "real" ESR is known to be frequency dependent. A resistor would work the same at every frequency and therefore produce a different sound result than desired? OK, it's a low effort experiment so I'll try it out before testing other capacitors. But maybe someone here on the forum has already tried it?

Dave, thank for the recommendation, do you mean Russian K75-10 and/or KBG-MN types? That ones I could get i.e. from Bulgaria which is part of the EU via ebay and therefore no customs and cheap shipping. TBH I see two potential issues. This caps are also some decades old, how about value shift and/or ESR shift. If they leak I would be not surprised if they are PCB based as the coolant, at least the KBG-MN types. Soundwise one can read good reports. Or do you have experiences with this types?

For me it is exactly the opposite case. I have 1977 Lascala, all original drivers. The Aerovox caps of the AA crossover have been leaking since long time and the values were no longer correct. I bought in 2006 an ALK universal network, which I had exactly 4 weeks in operation, it was not my idea of musicality. Since 2010 I have Crites AA crossovers, but that was with the sonicaps also not really the sound as in my memory with the Aerovox. Shortly later I had not used the speakers for 10 years because all the time I listened to Jubilees with K402. Since three months I have reactivated the old LaScala out of curiosity. Everything is ok, only mids and treble are still too loud and a bit sharp. Although the sonicaps have now settled in after a hundred hours the squaker and tweeter does not sound as in my memory with the original PIO caps in the sense of a homogeneous sound. So I'm glad that there are now the new original Klipsch capacitors, which another member I quote above would like to remove immediately. The caps Klipsch offers for the old AA xover look the same as in the pic of the new CW4 xover which is good news because the reviews about the CW4 a so very positive around the world. It is not about the „best“ cap in an insulated view but what fits best in the network also in terms of ESR value and so on. So to the price of the replacement caps the selecting process of the polyester (I think so) type has to be added as well as the ordering by Klipsch of today exotic values like 2uF and 13 uF. And that makes a point, even if I would use smaller values to reach 13uF in parallel constellation of caps I would alter the ESR to a „better“ smaller value but which would be probably wrong regarding the network requirements. The only downside is that shipping and tax plus customs to Germany is in addition more than the price of the caps themselves. Alternatively I could try new motor run caps which I can get over here but I am afraid that the newer PP foils do not behave like the old times PIO and I do not want to waste my time with trying out different caps over and over.

Others may know better but there is probably nothing really healthy inside those old caps regarding dangerous PCB.

T_Evans, congratulations on your new amp. Is the problem with the coax cable also gone? If not, this is usually the only working solution because (or if) there are different ground potentials between the mains and the antenna connection that cause the hum. See below the link. The isolation transformer type works best in my system. https://en.wikipedia.org/wiki/Sheath_current_filter

Bob, welcome to the Forum,, I have Lascala from 1977 and the original AA crossover capacitors are damp and rusted even though I always stored them dry. I wouldn't be surprised that your capacitors don't look very different. Others will know better, but those original capacitors with their incorrect values and high ESR can indirectly affect bass response in my experience. I currently use an AA replacement crossover since 11 years that Bob Crites had built. There are better capacitors out there, but these sonicaps are ok at least in values. I assume that you have connected everything correctly. But maybe it wouldn't hurt to double check if the KHs are still connected correctly in phase. The bass that a Bose 901 can do in the same large room, even if they are closer together, should easily be surpassed by the KH. BTW you have a very nice location and some fine classic cars are to be seen at your place.

garyrc, That sounds very reasonable to me and it goes along the lines of my guess in my thread about the timeline of the K55V versions...until the end of the AA crossover when the K55V was discontinued.

When I compare the frequency response and the specifications of the new PD-5VH with the curves that can be found here on the forum for the K55V (regardless of whether single or dual phase plug), then I would be afraid that the PD-5VH is not so well suited for my AA crossover. But maybe Atlas measured the new driver with a different method than ALK or BEC did with the K55V? Or the new heat resistant alnico material has less magnetic strength, or are they using different, perhaps more massive diaphragms that drop out at 4,500 Hz? One more point that interests me a lot, I had started another thread that has no replies yet. Without hijacking this thread...regardless of the specification of the PD-5VH, is it mechanically possible to mount the old dual phase plug of the soldered K55V (of course the whole part with the thread for the horn) on a PD-5VH?

Jim, thank you very much for the very detailed and valuable information. I have a reason why I would not trade my K77 for K77M...or maybe I would, to keep the balance of the SPL? I would maybe buy them in addition as an alternative solution. It is a pity if the alnico K77 should have become more powerless. But I love the sound of alnico magnets, may be I could try first new diaphragms. Momently I am happy with the SPL of my tweeters even if they are on the „soft“ side. It's about the magic moment when the sound emerges from silence. For example, very quiet string instruments that just breathe. In my opinion, alnicos are much finer and more transparent than ferrite or ceramic magnets. I also have a question regarding the new Atlas PD-5VH alnico in this circumstances, are they identically good as the old K55V single phase plugs and interchangeable without any acoustic difference? Just in case I need new drivers.

I have a 1977 Lascala with original K55 V single phase plug and round alnico K77. I am very happy with it and my question is partly out of curiosity, partly to maybe experiment a bit. But I will be able to restore and preserve the original condition. I have a lot of respect for originality, which I really like sonically as well. My question, or it is also a hypothesis. It is often the case that one measure leads to another measure even if someone would not have thought at the beginning that it might become necessary. That's why historically I wonder if the development of K55 versions happened independently of the development of K77 versions, or if there were interdependencies. Specifically: In about 1979 or around that? the square magnet K77 M appeared. But not because it was progress but because Alnico became too expensive. Only one year later, the dual phase plug appeared in the K55V. Could it be that the interaction with the K77 M caused PWK to make a change to the K55V? Is it possible that the single phase plug simply harmonises very well with the alnico K77? Two things,a) in the whole period between 1977 and 1983 or so? no change was made to the AA Xover, b) in real production the dual phase plug K55V never played together with the alnico K77. It is always very easy to say that a thing is better or worse when you look at it or measure it in isolation, like the sheet of a dual phase plug K55 V. But the interaction of all the components is the great art, you surely know what I mean. So, could playing a K55V dual phase plug together with an alnico K77 be disappointing? Perhaps PWK's intention in developing the dual phase plug K55 V was simply to connect more seamlessly with the slightly louder K77M? and not primarily because of the 9 Khz peak issue (which is not really audible for most people according to information here in the forum)? But the gain was so small that PWK returned to the single phase plug after only one year for the sake of a sensible investment with good reason and equally good sound? I look forward to answers, also very much if some have had experience with this.

I'm getting some old circa 1981 K-55V with solder connection and dual phase plug tomorrow which are not tested. Just out of curiosity and in case there is more damage than maybe the diaphragm...could I buy new PD-5VH and mount the old dual phase plug on it? I mean, of course, the whole part that is screwed to the horn and where the phase plug is mounted in. Or are these two versions fundamentally different in their dimensions and in the geometry of the screws etc.? On the other hand, could I combine the dual phase plug with a vintage magnet from a K-55V that only had the normal phase plug? Many thanks.

Since 1.5 years I am very happy with Tidal MQA via a Bluesound Node 2i. (EDIT: since mid of June 2021 I swapped for a new Bluessound Node which is definitely worth the upgrade). - The difference between MQA and CD res is audible if you compare the same recording. BTW the Bluesound also offers excellent Tunein sound quality.

With BBC specifications, it is the case that not all manufacturers and all decades of production are comparable. There are specifications, but they are sometimes interpreted within the margins or even exceeded. I have Stirling Broadcast LS3/5V2 built and licensed to BBC specifications. Still, they sound somewhat different than old Rogers, for example. You can't put two LS3/5a from different manufacturers or decades left and right together to make a pair. Back to Klipsch. As I write this I am listening to my beloved 1977 Lascala. I think it would be foolish to build new Klipsch that sound like these old darlings.Today there are other recordings, other music, other generations of ears. Still, I maintain that old Chet Baker or Bill Evans records sound subjectively better to me on these old speakers. But new recordings sound better on new versions. Another point. It would be nonsense to prescribe a fingerprint of a 1970 sound and build a new speaker to sound like it. But there are basic things to consider. Does a new Lascala sound better for any music? Does it sound as good as the old Lascala all the way down? Does the thin outer wall of the old Lascala perhaps sound better on a cello because it resonates more and is more lively? I mean yes. But isn't the same thin outer wall a big problem in dry pop recordings where resonances are more likely to interfere? I mean yes as well. This leads to the very old fundamental question, regardless of the age of the speakers...is there one speaker that does everything equally well? I have also Jubilees since 13 years. But for some recordings I like more the way how a smaller speaker integrates my room more. No matter how very good the Jubilees sound regardless. Isn't it nice how much you can get into it all:)

Ok, that is bad news if the basics are not right.