radiogram

Islander: Fair Enough. Happy listening. BTW: I am posting my CT125's for sale if case anyone is interested.

Islander: I totally disagree. Just beacuse a tweeter is a physical Drop In has absolutely no bearing on how it matches with your existing speaker & network. Certainly subjectively one couls find it an improvement, but if subjectivity is the thing, then any one can drop in virtaully ANYTHING that physically fits can claim improvement. My post was based on objectivity not subjectivity. One could use an equalizer or a tube amp with high output impedence and find the altered response better. The point here is when we say Drop-In it has to have some objective basis and CANNOT be based on subjective impressions. One's subjective opinion is as good as another. No credible equipment manufacturer blindly builds things on subjective hearing including Klipsch. They may use it to tweak the end result but the foundation is still solid objectivity. Objectively the CT125 is a mismatch with first order networks that have squakers extending up to 6KHz. Just beacause one likes its overlapped sound cannot not in anyway make my analysis wrong.

Dean: Thanks for the suggestion. I also read good things about HD600/650. The HD600 is very much in my radar even though it is a bit beyond my budget. Do you have any experience with Denon Headphones? I am sure you are right about this. While I never owned quality headphones, I have herad a few.

Greg: I think what everybody is trying to say is that while ultimately we all listen and decide, there is a basis and foundation that precedes listening i.e. sound (no pun intended) principles of physics, acoustics, filter theories, electrical engineering etc. I certainly appreciate your passion with KHorns and sharing with people with your subjective experiences, of course you are not the only one, there are a tons of others who do so and not all of them may be anymore technically qualified than you are. However, any subjective analysis without precise understanding & adjustment and covering of all technical basics (at least as we know of today) could mislead one i.e. the evaluator himself, in deciding what is better or worse. Sure enough, if everything is based on technicality alone then no amplifier or speaker manufacturer would even bother having a listening evaluation or a listening team. They will simply apply theory, build, measure it and ship it out. But we all know that is not the case. They do listen. But in what sequence? They just do not start building arbitrarily by just listening and tweaking endlessly. They start with some technical fundamentals and theory. This is the BASIS. Listening is only next, to validate and tweak further. If this were not the case and ultimately only ears matter then I am sure these companies can make more profit by hiring anyone who can just tweak circuits by trial and error. But again they all have EEs, Physicists, etc in their R&D (I am not talking about mushrooming internet based audio compaies that just rebrand cookie cutter designs). Why should they bother when they can pay someone else a lot less to just listen and decide? After all they are business houses who sell to customers. PWK himself has a formal background in Physics and Engineering. Even Amar Bose who does not publish specs has a PHD from MIT! (one many people hate, but I do not). Anyway, all things we use in life, audio, cellphones, automobiles, microwaves, etc – they were not created by some accident by some non-technical person. They were all out of inventions from scientists, Mathematicians, physicists, Engineers, etc. The CD format we all listen to these days is nothing but an application of mathematicians (Fourier, Nyquist, etc). Sure if a common man looks at Fourier transform it is total gibberish and techno babble. But digital recording and digital telecommunications work only on this principle and not by some accident or tweaking. There is a good scientific reason why medform works for diabetics, why Tylenol helps headache and all these came out only from science and principles that are measurable. Should a diabetic just go by his gut feeling on how he feels or should he periodically check his glucose numbers? The point about do not bother me with anything technical but I want only what the ears say, IMO probably applies to people who are casual listeners and mostly do background or party listening. I have some friends that prefer their HT in a box to my Klipsch’es and even over a well regarded monitors I owned in the past (Proac Response 2). Of course their rationale was the same – I do not care about what technical explanation you give, my my ears like my HT in a box. That is their choice, they are entitled to it and is fine with me. But the point here is, when we are talking about people who own speakers like KHorns/B&Ws/Quads/ etc, these are a different sect of people who are a lot more discriminating (I am not of course including rich snobs who just own these only to show off just because they can afford it, without any real passion or understanding of audio – If one stuffs a radio shack into a audiophile suit with mega buck price tag they may buy it and be quite happy and proud). The tweeters you have tested themselves exhibit so much variation in not just sensitivity (and that too one that varies at different frequencies) but overall response characteristics, pass band band-width, roll characteristics, etc. Having a same network to judge all of them may not be fair to all of them and may bias you unfairly even if that is not your intent. The ideal thing would be to customize network for each driver separately with some common performance goals that again is within the limits of all the drivers and then compare them as not just tweeters but as driver-network pair. But this requires understanding what to measure, how to and needs precise caliberated instruments. And even when done so, need to be recommended as a tweeter cum specific network combination as a pair. So, the bottom line here is while we can all say ultimately we tend to judge by ears, the fact is that we will not even have that luxury to say so if not for science & measurements to begin with. Cheers

Yes, they do and I also like Mick's drumming. This reminds me of the song "Dreams" and made me realize that I have not listened to FM in a long time. I am going to serach that CD down and play it on the Cornscala's I built recently. Cheers

Lee: I understand your points. My dissatisfaction with many recordings actually extends beyond the CCR example. Even many modern CDs I have that were digitally mastered while they "sound" good there seem to be an aritificiality to it. Ironically even though the CCR album may not be up to the mark, it sounds relatively much less artificial than some modern digitial recordings. As I have mentioned in another post in this thread, the drum track on a test CD I have sounds pretty close to real. I am able to identify that drums with what I experienced last year up close in a small Italain resturant in Greenwich Village NY where a live Jazz band was playing sort of a spanish fusion Jazz, pure live unamplified (It was an awesome experience BTW). But I am unable to relate the drum and symbals in the same manner with many recordings I have, even modern ones. Maybe I am conditioned growing up listening to good old rock & roll that was just pure and simple - Drums, Lead guitar, Bass Guitar, maybe a keyboard and that's it (no other ecletronic crap) and perhaps this why I am finding them to be more natural than modern ones in spite of their limitations using analog equipment for mastering. And thanks for the pointer to RPG. Gram

Shawn: I do agree with that. However, the reason I also brought up the recording was, for example I have a test CD that has a track that has only the drummer and no other instruments. This track in the same room and the same system, the drum and symbals sound very close (if not quite) to natural. If it was mostly the room this track must have also been influncenced as it does with other commercial ones. But many commercial ones I have, even modern digital masters, the drums and symbals do not sound stand out separate as much and they are somewhat burried as part of some many others. Now, this gives me a good excuse to buy a pair of good headphones that I have been putting off for a long time. Any suggestions under $300? Thanks

Lee: I recently went to a party a few ago where they had a live band (of couse the eventual sound was still coming through amplifed electronics and JBL speakers). They were playing a lot of classic rock like CCR, Alman Brothers, etc. Never in my course of that session I had any thoughts about any audiophile jargons like midbass, upper bass tightness, etc. The only things I were remarking on were how the drum and symbals sound good and so the drummer must be good or the singer is OK but really cannot go high pitch like Fogerty, etc. I came back home and put on my CCR, etc CDs, that were played at the party. It did not sound the same. It did not sound bad but I was only reminded of lower mid congestion and all audiophilia jargon that never entered my mind in the party. I hear bass but not distinct drums, I hear symbals but something burried in the mix, soft and not metallic and live as it sounded. In fact this is the case with many of my CDs and even some Vinyls. Of course the Room has a LOT to do with it. But I somehow feel that it is not just the room and the recording has a lot to do with it. In that context I am surprised as to many people cite commercial recordings as a reference in evaluating speakers when they are mixed as per the Engineer's preference and based on what room and what monitors he used to equalize, when none of them match up with the system and environment under evaluation.

This thread has made me realize that I myself is now confuded on how to match sentivity between different drivers (be it instrument or ears or whatever). A driver's sensitivity is not constant. Lets us say that Tweeter A has a an average sensitivity of 106dB in the 4-6KHz range and average sensitivity of 99dB in the 10-15KHz range (Somewhat like K77). Tweeter B has an avergae sensitivity of 103dB in the 4-6KHz range but has an average seneitivity of 101dB in the 10-15KHz range (somewhat like Beyma). Now what band will one use to match sensitivity? If I use 4-6KHz band to match up that means Tweeter A will be at 96dB in 10-15KHz range and Tweeter B will be at 101dB in the same range. Then Tweeter A will sound let us say lacking in air whatevr jargon that is. Alternativley if I use 10-15KHz band then Tweeter A will be +5dB more than Tweeter B in the 4-6KHz rnage and will subjectivley sound brighter or in your face or more detailed as one may choose to describe it or conversly Tweeter B may sound dull or more listenable or refined etc. So it may be important to specify what are the sensitvities in the whole pass band first and then explain the choice of what reference frequence or bandwidth that was used to match sensitivities. What do you guys think?

I have been a Hersey owener and recently bought a pair of K77-F from Klipsch for my Cornscala project. It seesm to me tha the K77-F extends lower than the K77 in my Herseys (circa 1984) and they also seem to have relatively flatter balance and overall better sounding. Has anyone done any actual measurement plots? Thanks

Hardhead: You have a point in that if a tweeter has lower sensitivity then the resulting output will reduce overlap. However the downside to it is that the acoustic output in the highs also are lower and out of balance. Now I do not know clearly if and how Greg had all tweeters tested at the same sensitivity, Greg mentioned that he also tuned by the ear (which I am not sure is a reliable method to match sensitivity at high frequencies, but that's beside the point here). If I look at this post comparing the plot of K77 vs Beyma (http://forums.klipsch.com/forums/p/40675/372387.aspx), on the surface it may seem that the Beyma actually starts rolling off (i.e on the lower side of the bandwidth not the higer side) even earlier thna the K77 and its extension at the very end may seem moot since it is already at levels about -5dB and further taking into account the -xdB imposed the by crossover and hence should render less overlap than the K77. However, the average sensitivity of the Beyma in the 5Khz-12Khz range is actually lower than the K77. So, if we match them up then certainly the Beyma will be more extended in the lower nethers in a more audible passband and should consequently result in higher overlap compared qith say K77.

Bob: The three inductors in the squwaker/tweeter section look like Ferrite core or steel laminate and not look like air core. What type are they? Thanks

Dear members: I would like to propose the terminology "Classic Cornscala" to clearly distinguish what the original cornscala was conceived from and how it as evolved today for the following reasons: 1. When someone today mentions today, it is hard to comprehend what drivers or dirver horn combinations he/she(!) is using for the mids and highs since there are many flovors today. 2. To give due credit to the people who inspired this concept - Bob Crites & James Cullison for their original work on Cornscala that was defined as follows: CLASSIC CORNSCALA: Bass - Cornwall Bass bin Mid - K55/K400/K401 Highs - CT125/K77 Your thoughts?

MechMan: In the very begining the Cornscala as inspired by Bob Crites and James W Cullsion, defined Cornscala as having Cornwall's bin, midrange of LaScala (K55/K400/K401 and highs of LaScala K77 or CT125 as per Crites version). But that was few years ago and now the term Conrscala has no universal definition except for perhaps assuming cornwall bas bin. The drivers and horns for the mid & highs are all over the place today. Just search conrscala in the forum you will see so many different flavors of midrange horns, drivers etc. Based on what Greg said, you may want to further inform Alk regarding your definition of cornscala or what Greg specified as Cornscala for the network, as I undertdand Al's networks are Precision built based on the drivers. Cheers

Al: Thanks for the detailed and patient explanation. Reading this in conjunction with re-reading your website article on measuring complex impedance, makes it much clearer now. This has also made me wary of my simplified measurement process and I doubt the accuracy of those data. I am going going to get a WT3 Tester as suggested by Lee and redo all the measurements and I will repost them. BTW, as much wonderful the internet is for informstion, it sure is a double edged sword. So much for many formulas and design advice based on just Re alone! Thanks & Regards

psg: Ok. This warrants a corrective statement from me. I have rephrased and corrected my post accordingly. So please read the same again The typeA falls into the said category. Its tweeter section is same as Hersey being first order. The squawker network except for the low cutoff being different is the same otherwise in that it is not a bandpass, thus allowing the full electrical output to be presented to it all the way to 20Hz. Even though the first order tweeter network only provides say a limited –xdB attenuation, the acoustic output of the K77 is actually much lower than –xdB, because the K77 itself acoustically drops off below 4000Hz (it is more than 10dB down at 3000Hz, all by itself fed with 0dB signal). Now if one were plug in directly a tweeter which extends much below in frequency into the same network, then its acoustic output will be attenuated only by –xdB imposed by the network and not lower since say at 3000Hz it is within the full passband of the tweeter. So in comparison there will be more overlap now. There is another aspect with TypeA is that there is no more room for higher sensitivity tapping as the tweeter section is connected directly to the input Cap. So there is no way to compensate for the lower sensitivity of the CT125 other the having to lower the sensitivity of the squawker and tweeter. My CT125s are about 6dB lower than K77, Greg of Volit Audio has reported 5.4dB lower and ALK also sometime back reported lower sensitivity. Now, getting to TypeAA - It is not in the same category as above. While its squawker section is still high pass and not bandpass, it has a 3rd order tweeter filter. This higher rate of attenuation should mitigate the CT125’s extended lower freq acoustic output. While it will still be more than the K77 in absolute terms, it may be at levels where it may not be audibly noticeable. So, in that context for TypeAA sure CT125 is a good possibility. However again note the sensitivity issue. In the TypeAA also (like the typeA) there is no more room for higher sensitivity tapping as the tweeter section is connected directly to the input Cap. One will be forced to lower the sensitivity of the woofer and squawker which is a more complicated affair and further negates the higher sensitivity advantage of the Khorn or Lascala. There are many tweeter choices out there (Beyma, Jbl, Selenium, etc). It is important one understands how they differ electro-acoustically form the one it replaces, does it need crossover mods and if so what changes and if one does not want to get into crossover mod at least understand what effect is. I would categorize CT125 as an alternative choice like many others, rather than a direct drop in. At the minimum even if one had a steep slope network, crossover mod is required for sensitivity difference alone. Again all said and done, one may like the end result subjectively, for which I have no argument. I can only give some perspective based on some objective aspects when in my experience it also somewhat seems to correlate with my perceived hearing. BTW, Thanks for helping me to correct myself. Regards

psg: I am sorry that I do not undertand your question clearly. While I do not have personal experience with either AA/AA, they are not just high pass tweeter netwroks. Both are balancing networks with a Low pass woofer section, squawker section tweeter section. In fact all Klipch networks are full dividing networks. Also, AA/A networks are for Khorn/LaScala and have nothing to do with Herseys. If you can explain me more your question, I can answer better. Cheers

Al: I am also quite overwhelmed trying to understand/refresh everything too soon. So I am going to ignore the context of my previous post and start off with something very basic. In that process I maybe overstating the obvious in the following post, but it is only to give you an idea and the thought process from where I come from and what logical flow I followed (or illogical as may may preceive and prove me so). So please do not mistake me for dwelling on the obvious. As much outrageous (sharing your humour!!) maybe Gill’s acceptance of oversight and further publically correcting himself, fortunately it reveals that I and Gill are on the same page. Unfortunately this does not place me in the same page as you in the following context: From Gill’s revision, both Gill and I seem to model the woofer as Re+Le and consequently Z=Re+JXL where Re is indepedent of freq. If the woofer were purely resistive then we need to deal only with Re. But we know that the woofer has a voice coil inductance and it contributes to Reactance and by virtue of that the woofer’s ultimate Ohms is no longer just resistive but it is a combination of resistance and reactive resistance that ultimately becomes impedance. We further know that the DC resistance part does not change with freq but the reactive part is one that changes with frequency thus rendering the Z of the woofer as one that is not constant but one that varies with freq and thus represented as Re+jXl. The nominal impedance of the woofer is not Re, but an average in the bandwidth of interest and that average is based on the value Z(f). So a speaker may have a DC Resistance of 4 Ohms, but its nominal impedance turns out to be say 7 Ohms. Now, how did the 4 Ohm Re now suddenly become a nominal Z of 7? That is precisely due to the contribution of JXl - the AC factor. So where I fail to be on the same page with you is you seem to use Z(nominal) + jXl to model the woofer instead of Re+JXL. The nominal impedance in itself is due to the contribution of XL adding to Re. For e.g for my cornwall bass bin you use the woofer model as 7+JXL. The 7 Ohm in itself is because of Re(=3.7)+JXl. So it is confusing to me that you model the woofer as Z(nominal) + jXl instead of Re+JXl when the nominal 7 Ohm already is a result of the Xl’s reactive contribution. Thanks.

Al: When I tested the Zobels I had connected the R first and then C to the ground. In your plots you seem to connect C first then R to ground. Does it matter since they are in series? Thanks

Comparison Plot

Al: What does your simulation say for R=6.3 & C=50uF. When I expereminetd that I seem to get a better impedance plot as below. Granted my measurement technique is crude, but the goal of zobel being to present a fairly contant load, ultimately if the measured voltage is fairly constant either across the know Resistor or Load, is not that a good indication or good enough?

Al: I do not have any specific instrument to measure Z. I am using the old fashioned crude method as follows: Amp Out------Known R=7.4Ohms----------------- | | R Woofer C | | | --------------------------------------------------------------- With a known input Voltage of say 1Volt, I measure the voltage across the known resistor, then divide that voltage By 7.4 to get the Current. I compute Z of the load as = (Input Volts - Voltage across R=7.4) / Current. How much I will be off by this type of calculation?

Al: After comparing your two Zobel plots and I got pretty excited about your 2nd plot with R=6.8 & C=27uF. I wanted to try it on the speaker and checked what closest parts values I had. The closed R I had was 6.3 (strangely it measures 6.3 Ohms but label says 5 Ohm). As far the Cap the only I coould get close to it was using 4 100uF Caps in Series to get 25uF. I connected this zobel across the Woofer and did a measurement test by using a known R=7.4Ohms in series between the Amp and the woofer with the paralled zobel and as usual reverse calculated impedence using voltage division. It seems pretty good except that it differs from your simulation in having a mild hump between 400Hz-900Hz. Please see attached Comparitive measurements. I would still like to investigate flattening aout the 400-900Hz region. Thanks so much.

Al, Can you explain how arrived at R=6.8 and C=27uF for the Zobel? Myunderstanding was that C=Le / Re (DC Resistance) and if I assume Le as 1.1mhy and use Re=3.7, I end up with 80uF. So my zobel has R=3.7 and C=80; Further some people sugget that the R in zobel must be 1.25 * Re. Thanks

Gill: The total impedence of the woofer is Zw = Re + jZl (where Zl being 2*pi*f*L). Is'nt then my measured impedence at the input of Re+Le circuit actually |Zw| = SQROOT(SQ(Re) + SQ(XL)) and NOT (Re + Zl) ? If I go by |Zw| and plug in my measured impedence @ 630Hz to be 7.7 Ohms with Re=3.7, I end up with Le=1.7mh. Please clarify.